Safety Switch for Photovoltaic Systems
Various implementations described herein are directed to a methods and apparatuses for disconnecting, by a device, elements at certain parts of an electrical system. The method may include measuring operational parameters at certain locations within the system and/or receiving messages from control devices indicating a potentially unsafe condition, disconnecting and/or short-circuiting system elements in response, and reconnection the system elements when it is safe to do so. Certain embodiments relate to methods and apparatuses for providing operational power to safety switches during different modes of system operation.
The present application is a continuation of U.S. application Ser. No. 17/240,276, filed Apr. 26, 2021, entitled “Safety Switch for Photovoltaic Systems,” which is a continuation of U.S. application Ser. No. 16/248,475, filed Jan. 15, 2019, now U.S. Pat. No. 11,018,623, issued May 25, 2021 entitled “Safety Switch for Photovoltaic Systems,” which is a continuation-in-part of U.S. nonprovisional application Ser. No. 15/250,068, filed Aug. 29, 2016, now U.S. Pat. No. 10,230,310, issued Mar. 12, 2019, entitled “Safety Switch for Photovoltaic Systems.” The content of these are incorporated by reference herein in their entireties for all purposes. The present application claims priority to U.S. provisional patent application Ser. No. 62/318,303, filed Apr. 5, 2016, entitled “Optimizer Garland,” hereby incorporated by reference in its entirety. Additionally, the present application claims priority to U.S. provisional patent application Ser. No. 62/341,147, filed May 25, 2016, entitled “Photovoltaic Power Device and Wiring,” hereby incorporated by reference in its entirety.
BACKGROUNDSafety regulations may require disconnecting and/or short-circuiting one or more photovoltaic (PV) generators or other components in case of an unsafe condition occurring in a photovoltaic installation. For example, safety regulations require that in case of an unsafe condition (e.g. a fire, a short-circuit, carrying out of maintenance work), the maximum voltage at any point in a photovoltaic installation may not exceed a safe voltage level. In some photovoltaic systems, it may be necessary to disconnect and/or short-circuit one or more photovoltaic generator(s) to achieve the safe voltage requirement. While photovoltaic systems may be deployed for tens of years, safety regulations may change at shorter time intervals (e.g. every several years). It would be advantageous to have a controllable safety switch which may be controlled to disconnect or short-circuit a PV generator in case of a safety hazard, and which may be controlled to reconnect the photovoltaic generator once the system is safe again. It would be desirable for controllable safety switches to be cost-effective and easily deployed.
SUMMARYThe following summary is a short summary of some of the inventive concepts for illustrative purposes only, and is not intended to limit or constrain the inventions and examples in the detailed description. One skilled in the art will recognize other novel combinations and features from the detailed description.
Embodiments herein may employ safety switches and associated apparatuses and methods for controlling currents through branches and/or voltages at nodes in photovoltaic (PV) installations.
In illustrative embodiments comprising one or more electrical systems, a group of electrical safety switches may be electrically connectable to a plurality of electrical power sources. The electrical safety switches may be controllable to maintain safe operation of the electrical systems.
In illustrative electrical systems, a safety switch may be deployed between serially-connected photovoltaic generators in a photovoltaic installation. In some embodiments, safety switches may be installed between each pair of PV generators. In some embodiments, the number and location of safety switches may be chosen with regard to current safety regulations, and in some embodiments, the number and location of safety switches may be chosen with regard to anticipated “worst-case” safety regulations. For example, in locales where adding, reconfiguring and/or removing system components is easy and inexpensive, safety switches may be deployed in a PV installation in accordance with the safety regulations at the time the installation was built. In locales where adding, reconfiguring and/or removing system components may be difficult or expensive, safety switches may be deployed in a manner that complies with a “worst-case” (i.e. most stringent) prediction of future regulations.
Illustrative safety switches according to some embodiments may be retrofit to existing photovoltaic installations and components. Illustrative safety switches according to some embodiments may be integrated in other PV system components (e.g. connectors, PV generators, power devices, combiner boxes, batteries and/or inverters), potentially reducing the cost of design and manufacturing of the safety switches, and increasing
In some embodiments, auxiliary power circuits are used to provide power to safety switches and associated controllers. In some embodiments, safety switches are located at system points which do not carry significant electrical power when the safety switches are in a particular state (e.g., when safety switches are in the ON state). Illustrative auxiliary power circuits are disclosed herein, along with associated methods for providing power to the auxiliary power circuits and safety switches regardless of the state of the safety switches.
In some embodiments, components and design of safety switches may be selected to regulate or withstand electrical parameters when illustrative safety switches are in the ON or OFF states. For example, some illustrative safety switches may comprise shunt resistors sized to regulate electrical current flowing through safety switches when the safety switches are in the OFF position.
Further embodiments include photovoltaic power devices comprising internal circuitry configured to limit a voltage between input terminals to the photovoltaic power devices in case of a potentially unsafe condition while continuously providing operational power to the photovoltaic power devices.
Further embodiments include electrical circuits for interconnecting photovoltaic generators and photovoltaic power devices configured to limit a voltage between various system nodes while continuously providing operational power to the photovoltaic power devices.
Further embodiments include a chain of preconnected photovoltaic power devices with associated safety switches, which may provide a cost-effective, easy way to wire a photovoltaic generation system along with associated safety switches.
In some embodiments, safety switches may be in communication with accompanying system devices, such as system control devices and/or end-user devices such as graphical user interfaces for monitoring applications.
Further embodiments include user interfaces for monitoring the state of and parameters measured by safety switches in illustrative power systems. A system owner or operator may be able to view a list of system safety switches, associated switch states and electrical parameter measured thereby. In some embodiments, the list may be a graphical user interface (GUI) viewable on a computing device, such as a computer monitor, tablet, smart-television, smartphone, or the like. In some embodiments, the system operator may be able to manually control safety switches (e.g. by pressing buttons).
As noted above, this Summary is merely a summary of some of the features described herein and is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. The Summary is not exhaustive, is not intended to identify key features or essential features of the claimed subject matter and is not to be a limitation on the claims.
These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following description, claims, and drawings. The present disclosure is illustrated by way of example, and not limited by, the accompanying figures.
In the following description of various illustrative embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which is shown, by way of illustration, various embodiments in which aspects of the disclosure may be practiced. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made, without departing from the scope of the present disclosure.
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In the illustrative embodiment of
In some embodiments, the power and ground buses may be input to system power device 110. In some embodiments, system power device 110 may include a DC/AC inverter and may output alternating current (AC) power to a power grid, home or other destinations. In some embodiments, system power device 110 may comprise a combiner box, transformer and/or safety disconnect circuit. For example, system power device 110 may comprise a DC combiner box for receiving DC power from a plurality of PV strings 104 and outputting the combined DC power. In some embodiments, system power device 110 may include a fuse coupled to each string 104 for overcurrent protection, and/or one or more disconnect switches for disconnecting one or more PV strings 104.
In some embodiments, system power device 110 may include or be coupled to a control device and/or a communication device for controlling or communicating with safety switches 102. For example, system power device 110 may comprise a control device such as a microprocessor, Digital Signal Processor (DSP) and/or a Field Programmable Gate Array (FPGA) configured to control the operation of system power device 110. In some embodiments, system power device 110 may comprise multiple interacting control devices. System power device 110 may further comprise a communication device (e.g. a Power Line Communication circuit and/or a wireless transceiver) configured to communicate with linked communication devices included in safety switches 102. In some embodiments, system power device 110 may comprise both a control device and a communication device, the control device configured to determine desirable modes of operation for PV power devices (e.g. power devices 103), and the communication device configured to transmit operational commands and receive reports from communication devices included in the PV power devices.
System power device 110 may be coupled to any number of other devices and/or systems such as PV systems 100 (e.g., various discrete and/or interconnected devices such as disconnect(s), PV cell(s)/array(s), inverter(s), micro inverter(s), PV power device(s), safety device(s), meter(s), breaker(s), AC main(s), junction box(es), camera etc.), network(s)/Intranet/Internet, computing devices, smart phone devices, tablet devices, camera, one or more servers which may include data bases and/or work stations. System power device 110 may be configured for controlling the operation of components within PV system 100 and/or for controlling the interactions with other elements coupled to PV system 100.
In some embodiments, the power and ground buses may be further coupled to energy storage devices such as batteries, flywheels or other energy storage devices.
Safety regulations may define a maximum allowable voltage between the ground bus and any other voltage point in PV system 100, during both regular operating conditions and during potentially unsafe conditions. Similarly, safety regulations may define a maximum allowable voltage between any two voltage points in PV system 100. In some scenarios, an unsafe condition in PV system 100 may require disconnecting or short-circuiting one or more of the PV generators 101 in a PV string 104.
As a numerical example, an illustrative PV string 104 may comprise 20 serially-connected PV generators 101. Each PV generator 101 may have an open-circuit voltage of 45V. In case of an unsafe condition (e.g. a fire, detection of an arc or a dangerous short-circuit somewhere in PV system 100), safety regulations may require that system power device 110 cease drawing power from PV string 104, resulting in an open-circuit voltage of 45·20=900V across PV string 104. Safety regulations may further require that in case of an unsafe condition, the maximum voltage between any two points in PV system 100 may not exceed, for example, 80V. To comply with safety regulations, safety switches 102 may disconnect the plurality of PV generators 101 comprising PV string 104, resulting in PV generators 101 (excluding the PV generators 101 coupled to the ground and power buses) having a “floating” voltage with regard to ground, and a voltage drop of about 45V between the two terminals of each PV generator.
In some embodiments, system power device 110 may respond to a potentially unsafe system condition by limiting the voltage across each PV string 104. For example, system power device 110 may comprise an inverter configured to regulate a voltage of about 60V across each PV string 104 in case of a potentially unsafe condition.
Reference is now made to
It is to be noted that the ratio of photovoltaic generators to safety switches, and the location of safety switches, may change depending on electrical parameters of photovoltaic generators and safety regulations. For example, if low-voltage PV generators (e.g. PV generators having an open-circuit voltage of 10V) are used as PV generators 101, and safety regulations allow a maximum point-to-point voltage of 55V in case of a potentially unsafe condition, a single safety switch 102 may be disposed per five PV generators 101. If safety regulations are changed to allow a maximum point-to-point voltage of 45V in case of a potentially unsafe condition, additional safety switches 102 may be added.
Safety switches 102 may comprise a resistor for regulating current through safety switches 102 when the switches are in the OFF state. For example, each of safety switches 102 may comprise a shunt resistor (e.g. resistor R31 of
In some embodiments, the values may vary depending on the regulated voltage provided by system power device 110 and the open-circuit voltage of each PV generator 101. For example, string 104 may comprise ten PV generators, and ten safety switches, each PV generator having an open-circuit voltage of 30V, and system power device 110 may provide a voltage of 50V across PV string 104. In that case, each safety switch may be operated to have a negative voltage of 25V, providing the string voltage of (30−25)·10=50V.
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Safety switch 302 may comprise communication device 305 for communicating with other devices and controller 303 for controlling the operation (e.g. turning ON and OFF) of transistor Q1. Controller 303 may be an analog circuit, microprocessor, Digital Signal Processor (DSP), Application-Specific Integrated Circuit (ASIC) and/or a Field Programmable Gate Array (FPGA). In some embodiments, communication device 305 may receive a command from an external device to change the state of transistor Q1, and communication device 305 may convey the command to controller 303. Communication device 305 may communicate with external devices using various technologies such as Power Line Communications (PLC), acoustic communications transmitted over conductors 308 and 309, and wireless communication protocols (e.g. Wi-Fi™, ZigBee™, Bluetooth™, cellular communications, etc.).
Auxiliary power circuit 304 may be coupled to conductors 308 and/or 309, and may provide power to controller 303, sensor/sensor interface(s) 310 and/or communication device 305. Auxiliary power circuit 304 may be variously realized, with illustrative embodiments disclosed herein (e.g. in
In some embodiments, safety switch 302 may further comprise measurement sensor(s) and/or sensor interface(s) 310 for measuring parameters such as current, voltage and/or temperature. For example, sensor/sensor interface(s) 310 may include a current sensor for measuring the current through conductor 308 or conductor 309, and/or a voltage sensor for measuring the voltage drop across transistor Q1, and/or a temperature sensor for measuring the temperature at or near male connector 306, female connector 307 and/or transistor Q1. In some embodiments, sensor(s)/sensor interface(s) 310 may provide measurements to controller 303, with controller 303 configured to take action (e.g. change the state of transistor Q1) according to the measurements received. For example, controller 303 may be configured to set the state of Q1 to OFF if a high current is measured through conductor 309, or if a high temperature is measured near male connector 306. In some embodiments, controller 303 may provide the measurements obtained from sensor(s)/sensor interface(s) 310 to communication device 305, with communication device 305 configured to transmit the measurements to a system controller or data-collection device (not explicitly depicted), such as system power device 110 of
It should be noted that while a preferred embodiment of the disclosure includes providing transistor Q1 for safety features (e.g. the ability to disconnect two PV generators from each other), other embodiments included herein might not include transistor Q1. Sensor/sensor interface(s) 310, auxiliary power circuit 304 and communication device 305 may be combined to provide measurement and data-reporting features even without the safety advantages (e.g. ability to disconnect a photovoltaic generator) provided by safety transistor Q1.
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In some embodiments, advantages may be obtained by integrating safety switch 402 into a photovoltaic generator connector or a PV generator junction box. For example, safety switch 402 may be built into connector 403 or connector 408 of a PV generator, providing safety switching functionality in a PV generator without necessitating additional components and connections. Integrating safety switches in PV generator connectors or junction boxes may reduce costs (e.g. by not requiring a separate enclosure and connectors for the safety switch) and simplify installation (since no additional components need be connected).
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In illustrative embodiments disclosed herein, safety switch 502 may be disposed between conductor 404 and electrical connection 512. Safety switch 502 may be functionally similar or the same as safety switch 302 of
In some embodiments, junction box 511 may further include an integrated PV power device similar to or the same as PV power device 903 of
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At step 605, the controller determines if a command (or, in some embodiments, a self-determination) to turn the switch to the ON state has been received. If no such command (or determination) has been received, the controller carrying out method 600 returns to step 604. If a command (or, in some embodiments, a self-determination) to turn the switch to the ON state has been received, the controller carrying out method 600 proceeds to step 606, turns the switch back to the ON state (e.g. by applying a voltage to a transistor node, or removing an applied voltage from a transistor node) and returns to step 601.
An auxiliary circuit for providing continuous power supply to a safety switch according to embodiments disclosed herein may be variously implemented. Auxiliary power circuits may provide power for operating a safety switch under varying conditions and at various times. For example, auxiliary power circuits may provide operational power to a safety switch at three times: at initial startup (i.e. when the system comprising a safety switch is first deployed), at steady-state ON time (i.e. when the system is up and running, during normal operating conditions, when the switch is ON), and at steady-state OFF time (i.e. when the system is up and running, during a potentially unsafe condition, when the switch is OFF).
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Auxiliary power circuit 704 may be coupled in parallel to transistor Q1. A first input of auxiliary power circuit 704 may be coupled to conductor 708, and a second input of auxiliary power circuit 704 may be coupled to conductor 709.
In some embodiments, auxiliary power circuit 704 may comprise analog circuitry configured to provide an appropriate control signal to transistor Q1. In some embodiments, auxiliary power circuit 704 may provide power to controller 710, with controller 710 configured to provide a control signal to transistor Q1.
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Auxiliary power circuit 714 may be coupled in series with transistor Q1. A first input of auxiliary power circuit 714 may be coupled to conductor 708, and a second input of auxiliary power circuit 704a may be coupled to transistor Q1.
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Operating auxiliary power circuit 704a according to the illustrative timing diagrams of
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The anode of diode D2 may be coupled to a transistor drain terminal (Vd), and the cathode of diode D2 may be coupled to the cathode of diode Z2 and a first terminal of capacitor C2. The anode of diode Z2 may be coupled to a drain terminal of transistor Q70, with the source terminal of transistor Q70 coupled to a transistor source terminal (Vs) and to a second terminal of capacitor C2. The gate voltage of transistor Q70 may be controlled by controller 710 (the control line is not explicitly depicted). The inputs of converter 721 may be coupled in parallel with capacitor C2.
Auxiliary power circuits 704a-b and 714 may be operated to provide a voltage drop across the terminals of safety switch 702 according to safety and effective system operation requirements. The drain-to-source voltage may be desired to be low during normal system operation, when safety switch 702 is in the “steady ON state”, i.e. when the switch provides a low-impedance path for photovoltaic power to flow through a PV string. When safety switch 702 is in a “steady OFF state”, safety switch 702 may be required to provide a drain-to-source voltage of about an open-circuit voltage of a PV generator without providing a low-impedance path for current flow.
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Operating auxiliary power circuit 704b according to the illustrative timing diagrams of
It is to be understood that illustrative operating points comprising MOSFET drain-to-source voltages of 65 mV and 90 mV, MOSFET gate-to-source voltages of 5V and 6V, and MOSFET drain-to-source currents of 10 A are used for illustrative purposes and are not intended to be limiting of operating points used in conjunction with illustrative embodiments disclosed herein. In some embodiments, multiple MOSFET transistors may be parallel-coupled to reduce ON-state resistance, thereby reducing the drain-to-source voltage across MOSFETs when in the ON state. For example, coupling five MOSFETs in parallel may reduce a drain-to-source ON-state voltage from 65 mV to 15 mV.
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Implementing auxiliary power circuit 715 as illustrated in
Elements of auxiliary power circuits 704a, 704b and 715 may be variously combined. For example, auxiliary power circuit 714 of
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In some embodiments, the power and ground buses may be input to system power device 810. In some embodiments, system power device 810 may include a DC/AC inverter and may output alternating current (AC) power to a power grid, home or other destinations. In some embodiments, system power device 810 may comprise a combiner box, transformer and/or safety disconnect circuit. For example, system power device 810 may comprise a DC combiner box for receiving DC power from a plurality of PV strings 804 and outputting the combined DC power. In some embodiments, system power device 810 may include a fuse coupled to each PV string 804 for overcurrent protection, and/or one or more disconnect switches for disconnecting one or more PV strings 804. In some embodiments, system power device 810 may comprise a system controller (e.g. a Digital Signal Processor (DSP), Application-Specific Integrated Circuit (ASIC) and/or a Field Programmable Gate Array (FPGA)) for providing commands to and receiving data from PV power devices 803 and safety switches 802.
Each safety switch 802 may be coupled between a first output of a first PV generator and a second output of a second output generator, and each PV power device may have two input terminals: a first input terminal coupled to the second output of the first PV generator, and a second input terminal coupled to the first output of the second PV generator. In this “two-to-one” arrangement, each pair of PV generators 801 are effectively coupled in series, with the combined voltage and power of the two PV generators provided to the input of PV power device 803. Each safety switch 802 is disposed between the two PV generators, for disconnecting the pair of PV generators in case of a potentially unsafe condition.
Some conventional PV installations feature a similar arrangement, with each pair of PV generators 801 directly connected to each other without a safety switch disposed in between the generators. In case of an unsafe condition, a PV power device 803 may stop drawing power from the PV generators, resulting in an open-circuit voltage at the PV power device input terminals which is about double the open-circuit voltage of each PV power generator. This voltage may, in some systems, be as high as 80, 100 or even 120 volts, which may be higher than the allowed safe voltage defined by safety regulations.
By operating safety switches 802 according to apparatuses and methods disclosed herein, in case of an unsafe condition (e.g. detected by system power device 810, a PV power device 803 and/or a safety switch 802), one or more safety switches 802 may move to the OFF state, reducing the voltage drop between the input terminals of each PV power device 803 to about 40-60 volts, which may be an adequately safe voltage level.
Each PV power device 803 may receive power from two photovoltaic generators 801 coupled to the inputs of PV power device 803, and may provide the combined power of the two photovoltaic generators at the outputs of PV power device 803. The outputs of a plurality of PV power devices 803 may be coupled in series to form a PV string 804, with a plurality of PV strings 804 coupled in parallel to provide power to system power device 810.
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Each of photovoltaic power devices 1003 may comprise four input terminals: T1, T2, T3 and T4. T1 and T2 may be coupled to and receive power from a first PV generator, and T3 and T4 may be coupled to and receive power from a second PV generator. In some embodiments, PV power device 1003 may be substantially the same as PV power device 803 of
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PV power device 1103a may comprise transistors Q3, Q4 and Q5. Transistors Q3-Q5 may be MOSFETs, JFETs, IGBTs, BJTs or other appropriate transistors. For the illustrative embodiment of
A first PV generator (not explicitly depicted) may be coupled between terminals T1 and T2, and a second PV generator (not explicitly depicted) may be coupled between terminals T3 and T4. Under normal operating conditions, transistor Q3 may be ON, and transistors Q4 and Q5 may be OFF. Under these conditions, the two photovoltaic generators may be serially connected, with the combined serial voltage of the two PV generators provided between terminals T1 and T4. When a potentially unsafe condition is detected, the controller controlling transistor Q3 may turn Q3 to the OFF state, reducing the voltage drop between terminals T1 and T4.
Even when transistor Q3 is OFF, power may still be provided at the input to PV power device 903. For example, in some embodiments, controller(s) controlling transistors Q4 and Q5 may switch Q4 and Q5 to the ON state when Q3 is OFF, resulting in terminal T1 being short-circuited to terminal T3, and terminal T2 being short-circuited to terminal T4. Under these conditions, the first and second photovoltaic generator may be coupled in parallel between terminal T1 and T4, allowing PV power device 903 to draw power from the PV generators (e.g. for powering devices such as controller 905, communication device 911, auxiliary power circuit 908 and other devices depicted in
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Transistor Q6 may be similar to or the same as transistor Q3 of
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When a potentially unsafe condition is detected, the controller controlling transistor Q6 may turn Q6 to the OFF state, disconnecting the coupling of terminals T2 and T3. The voltage at node N1 may be the voltage at terminal T1 or the voltage at terminal T3, the greater of the two. While the voltage at node N1 might not be predetermined, in either possible scenario, a PV generator may be coupled to the inputs of PV power device 903, providing power to PV power device 903 (e.g. for powering devices such as controller 905, communication device 911, auxiliary power circuit 908 and other devices depicted in
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Each PV power device 1203 may be designed to be coupled to more than one PV power generator 1201. For example, in PV system 1200, each PV power device 1203 (except for the PV power devices coupled to the power bus) is coupled to two PV power generators and to two safety switches 1202, with each safety switch 1202 (except for the safety switch 1202 which is coupled to the ground bus) coupled to two PV generators 1201 and two PV power devices 1203.
Under normal operating conditions, each PV power device 1203 may receive power from two PV generators 1201, and may forward the power along PV string 1204 towards the power bus. Under normal operating conditions, each safety switch 1202 may provide a connection between two PV generators 1201 and may provide a connection between two PV power devices 1203 for forwarding power along PV string 1204. For example, under normal operating conditions, safety switch 1202a provides a connection between PV generators 1201a and 1201b. PV power device 1203a may receive power generated by PV generators 1201a and 1201b, with safety switches 1202b disposed between PV power devices 1203a and 1203b, providing PV power device 1203a with a connection for forwarding power to PV power device 1203b. Similarly, safety switch 1202b provides a connection between PV generators 1201c and 1201d, with PV power device 1203b receiving power from PV generators 1201c and 1201d.
In case of an unsafe condition, safety switch 1202a may be operated to disconnect PV generator 1201a from PV generator 1201b, and to disconnect PV power device 1203a from the ground bus. Similarly, safety switch 1202b may be operated to disconnect PV generator 1201c from PV generator 1201d, and to disconnect PV power device 1203a PV power device 1203b. Operating safety switches 1202 in this manner may reduce the voltage in various locations in PV system 1200 to safe voltage levels.
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During normal system operation, transistor Q7 may be held in the ON state, and transistor Q8 may be in the OFF state. Capacitor C5 may then be in parallel with capacitor C4, and a first PV generator may be coupled between terminals T1 and T2, applying a voltage to capacitors C4 and C5 and providing electrical power at terminals T1 and T2. Terminal T4 may be coupled to an output terminal of a second PV generator, and terminal T3 may be coupled to an input terminal of a PV power device 1203. The power input to safety switch 1205 at terminals T1 and T2 may be output at terminals T3 and T4 to the second PV generators and the PV power device 1203.
Transistors Q7 and Q8 may be controlled by a controller (not explicitly depicted) similar to or the same as controller 710 of
When an unsafe condition is detected, the controller may switch transistor Q7 to the OFF state and transistor Q8 to the ON state. Capacitor C5 may be short-circuited by transistor Q8, while capacitor C4 may maintain the voltage imposed between terminals T1 and T2.
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The operation of the Buck+Boost DC/DC converter in PV power device 1203 may be variously configured. If an output voltage lower than he input voltage is desired, Q13 may be statically ON, Q14 may be statically OFF, and with Q11 and Q12 being Pulse-Width-Modulation (PWM)-switched in a complementary manner to one another, the circuit is temporarily equivalent to a Buck converter and the input voltage is bucked. If an output voltage higher than he input voltage is desired, Q11 may be statically ON, Q12 may be statically OFF, and with Q13 and Q14 being PWM-switched in a complementary manner to one another, the input voltage is boosted. Staggering the switching of switches Q11 and Q12, the circuit may convert the input voltage Vin to output voltage Vout. If current is input to the circuit by the Vin and common terminals, and the voltage drop across capacitors Cin and Cout are about constant voltages Vin and Vout respectively, the currents input to the circuit are combined at inductor L6 to form an inductor current which is equal to the sum of the current input at the Vin and common terminals. The inductor current may contain a ripple due to the charging and discharging of capacitors Cin and Cout, but if the voltage drop across capacitors Cin and Cout are about constant, the voltage ripples over the capacitors are small, and similarly the inductor current ripple may be small. The inductor current may be output by the pair of output terminals Vout. In some embodiments, a single output terminal may be included, and system designers may split the output terminal externally (i.e. outside of the PV power device circuit), if desired.
In illustrative embodiments, PV power device 1203 may be similar to or the same as PV power device 903 of
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The system topology illustrated in
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According to some aspects of the disclosure, PV power device 1603 may include power converter 1600 similar to, for example, PV power converter 900. Power converter 1600 may comprise a direct current-direct current (DC/DC) converter such as a Buck, Boost, Buck/Boost, Buck+Boost, Cuk, Flyback and/or forward converter. According to some aspects, power converter 1600 may comprise a direct current-alternating current (DC/AC) converter (also known as an inverter), such a micro-inverter. PV power device 1603 may have three input terminals, Tin1, Tin2, and Tin3, and two output terminals (not labelled, for clarity of depiction).
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Switch S16 may comprise a control terminal. The control terminal of switch S16 may be controlled by controller 1605. Correspondingly, controller 1605 may be configured to control switch S16. If an unsafe condition, such as a grid-outage, overvoltage, undervoltage, a problem with the inverter (such as, but not limited to, the inverter described above with reference to power converter 900), or any other problem which may result in a potentially unsafe condition, or a failure in the photovoltaic generator 1601a, is detected, controller 1605 may turn on switch S16, short-circuiting the input terminals of photovoltaic generator 1601a in order to protect, reduce the risk for, and so forth, power converter 1600 and/or personnel in the physical proximity of PV power device 1603. When switch S16 is OFF, the two PV generators 1601a and 1601b may be connected in series and to the input terminals of power converter 1600. In both scenarios, a safe voltage at locations within the system may be maintained. When switch S16 is ON, PV generator 1601a is short-circuited, and a reduced voltage between terminals Tin3 and Tin1 is obtained. Switch S16 being OFF may be indicative of normal operating conditions, and under normal operating conditions an increased voltage between terminals Tin3 and Tin1 may be permissible.
In an example of an aspect of system operation, communication device 1611 may enable sensor(s) 1604 to monitor the system described herein across above the common bus 1620 for a “keep alive” signal, as described above with reference to
It is appreciated that in the aspect of the present disclosure described herein above, in the event that PV generator 1601a fails, PV power device 1603 may continue working as long as switch S16 is turned ON. In such a case, PV power device 1603 may continue to receive power from PV generator 1601b. It is also appreciated that T-connector 1631 may provide a test point for measuring voltage across the PV generator 1601a, thereby enabling calculation of the individual operating parameters of each of PV generator 1601a and PV generator 1601b. Voltmeter 1642 is depicted in
According to another aspect of the present disclosure, an additional switch (not depicted) might be positioned between terminals, Tin2 and Tin3. The additional switch may also be controlled by controller 1605. In such an aspect, when both the additional switch is OFF, and switch S16 is OFF, the two PV generators 1601a and 1601b are connected in series to input terminals of power converter 1600. When switch S16 is ON, and the additional switch is OFF, the output terminals of photovoltaic generator 1601a are short circuited and photovoltaic generator 1601b provides the power to the input terminals to power converter 1600. Correspondingly, when the additional switch is ON and switch S16 is OFF, the output terminals of photovoltaic generator 1601b are short circuited and photovoltaic generator 1601a provides the power to the input terminals of power converter 1600. The ability to short circuit either one of photovoltaic generator 1601a or photovoltaic generator 1601b may make the system failure proof for each of the two photovoltaic generators 1601a and 1601b. When both switch S16 is ON, and the additional switch is ON, the output terminals of both PV generators 1601a and 1601b are short-circuited, thereby the input terminals of power converter 1600 are also short-circuited. Switch S16 (as noted above) and the additional switch may comprise a relay, a transistor, including, but not limited to a MOSFET, an IGBT, a BJT, a JFET, and so forth, or another appropriate switching element.
In still another aspect of the present disclosure, a single photovoltaic generator (not depicted) may be utilized rather than photovoltaic generator 1601a and photovoltaic generator 1601b. The single photovoltaic generator may have at least three output terminals (e.g., a first series string of solar cells connected between first and second output terminals, and a second series string of solar cells connected between the second output terminal and a third output terminal). The three output terminals may, respectively, connect to the PV power device 1603 over input terminals Tin1, Tin2, and Tin3. As described above, if an unsafe condition, such as a grid-outage, overvoltage, undervoltage, a problem with the inverter (such as, but not limited to, the inverter described above with reference to power converter 900), or any other problem which may result in a potentially unsafe condition, or a failure in the single photovoltaic generator, is detected, controller 1605 may turn on switch S16, short-circuiting the two of the terminals of the single photovoltaic generator in order to protect, reduce the risk for, and so forth, power converter 1600 and/or personnel in the physical proximity of PV power device 1603. When switch S16 is OFF, the output terminals of the single photovoltaic generator may be connected in series to the input terminals of power converter 1600, (i.e., “normal operation”) as described herein above.
In illustrative embodiments disclosed herein, photovoltaic generators are used as examples of power sources which may make use of the novel features disclosed. Each PV generator may comprise one or more solar cells, one or more solar cell strings, one or more solar panels, one or more solar shingles, or combinations thereof. In some embodiments, the power sources may include batteries, flywheels, wind or hydroelectric turbines, fuel cells or other energy sources in addition to or instead of photovoltaic panels. Systems, apparatuses and methods disclosed herein which use PV generators may be equally applicable to alternative systems using additional power sources, and these alternative systems are included in embodiments disclosed herein.
It is noted that various connections are set forth between elements herein. These connections are described in general and, unless specified otherwise, may be direct or indirect; this specification is not intended to be limiting in this respect. Further, elements of one embodiment may be combined with elements from other embodiments in appropriate combinations or subcombinations. For example, PV power device circuitry of one embodiments may be combined with and/or exchanged for power device circuitry of a different embodiment. For example, transistor Q9 of PV power device 903 may be disposed between electrical connections 512 and 513 of junction box 511 and operated to short-circuit the input to PV generator 101 of
Claims
1-25. (canceled)
26. A safety switch comprising:
- a first connector comprising a first conductor;
- a second connector comprising a second conductor;
- a switch circuit connected between the first conductor and the second conductor, wherein the switch circuit is configurable into: an ON state that provides a direct-current serial path between the first conductor and the second conductor, and an OFF state that disconnects the direct-current serial path; and
- circuitry connected between the first conductor and the second conductor and configured to: receive power across the first and the second conductors; control, utilizing the power, the switch circuit from the OFF state into the ON state; and control, in response to a loss of the power, the switch circuit from the ON state into the OFF state.
27. The safety switch of claim 26, wherein the circuitry is configured to receive the power at a first voltage between the first conductor and the second conductor when the switch circuit is in the ON state, and receive the power at a second voltage between the first conductor and the second conductor when the switch circuit is in the OFF state.
28. The safety switch of claim 27, wherein the circuitry is configured to maintain, while receiving the power, the switch circuit in the ON state.
29. The safety switch of claim 27, wherein the first voltage is between 15-200 millivolts when the switch circuit is in the ON state, and the second voltage is greater than 25V when the switch circuit is in the OFF state.
30. The safety switch of claim 26, wherein:
- the circuitry is configured to receive one or more power line communication signals transmitted to the safety switch via the first conductor or the second conductor; and
- the control of the switch circuit into the ON state is based on the circuitry receiving the one or more power line communication signals.
31. The safety switch of claim 30, wherein the one or more power line communication signals comprises an alternating-current signal over the first conductor or the second conductor.
32. The safety switch of claim 26, wherein, when in the ON state, the switch circuit has a current-voltage relationship that causes a voltage across the first and the second conductors to be between 15-200 millivolts when 10 amperes passes through the direct-current serial path.
33. The safety switch of claim 26, wherein the switch circuit has an on-resistance that causes a second voltage across the first and the second conductors to be generated in response to a serial current from the first conductor to the second conductor through the direct-current serial path.
34. The safety switch of claim 26, further comprising a diode having a cathode connected to the first conductor and an anode connected to the second conductor.
35. The safety switch of claim 26, wherein:
- the circuitry is configured to receive the power at a first voltage between 15-200 millivolts when the switch circuit is in the ON state;
- the switch circuit comprises a transistor connected, via a source or emitter terminal and a drain or collector terminal, between the first and the second conductors; and
- the circuitry is configured to generate a control voltage between a gate or base terminal of the transistor and the source or emitter terminal sufficient to maintain the switch circuit in the ON state.
36. The safety switch of claim 35, wherein:
- the circuitry comprises a power circuit configured to generate the control voltage from the first voltage,
- the control voltage is greater than the first voltage, and
- the power circuit is configured to cease generating the control voltage based on: a serial current flowing between the first and the second conductors through the direct-current serial path falling below a threshold level, or receipt of a power line communication signal comprising a shutdown command.
37. The safety switch of claim 26, wherein the circuitry comprises an auxiliary power circuit configured to:
- receive the power from an auxiliary current flowing from the first conductor to the second conductor through the auxiliary power circuit.
38. The safety switch of claim 26, wherein the circuitry is configured to:
- receive a keep alive signal via the first conductor or the second conductor;
- maintain the switch circuit in the ON state based on receiving the keep alive signal; and
- control the switch circuit into the OFF state based on an absence of the keep alive signal.
39. The safety switch of claim 38, wherein the keep alive signal provides the power.
40. The safety switch of claim 26,
- wherein the switch circuit comprises a transistor; and
- wherein the circuitry comprises: a communication circuit configured to receive power line communication signals on the first conductor or the second conductor; an auxiliary power circuit configured to convert the power to converted power; and a controller circuit configured to: generate, from the converted power, a control voltage on a gate or base terminal of the transistor, and based on the power line communication signals, vary the control voltage to control the transistor into the ON state and into the OFF state.
41. The safety switch of claim 40, wherein the controller circuit is configured to, in response to the power line communication signals, toggle the control voltage between a first value of less than 1 volt and a second value of greater than 5 volts.
42. The safety switch of claim 26,
- wherein the safety switch comprises a transistor connected between the first conductor and the second conductor; and
- the circuitry comprises an auxiliary power circuit configured to convert a drain-to-source or collector-to-emitter voltage across the transistor to a gate-to-source or base-to-emitter voltage applied to a gate or base terminal of the transistor, wherein the gate-to-source or base-to-emitter voltage is greater than the drain-to-source or collector-to-emitter voltage.
43. The safety switch of claim 26, further comprising a resistor connected between the first conductor and the second conductor and in parallel with the switch circuit.
44. The safety switch of claim 26, wherein the first conductor is configured to be connected to a photovoltaic panel connected to a power device, wherein the power device is configured to, based on a change in current flowing through the safety switch, cease drawing power from the photovoltaic panel to turn the safety switch to the OFF state.
45. The safety switch of claim 26, wherein the switching circuit comprises a transistor that provides the direct-current serial path, and wherein the circuitry is connected in across the transistor.
46. A system comprising:
- a photovoltaic string comprising a pair of photovoltaic panels coupled in series through a safety switch;
- wherein the safety switch is connected inline between the pair of photovoltaic panels;
- wherein the safety switch has an ON state that provides a direct-current serial path between the pair of photovoltaic panels, and an OFF state that disconnects the direct-current serial path; and
- wherein the safety switch comprises circuitry configured to: receive auxiliary power through the photovoltaic string, utilize the auxiliary power to control the safety switch from the OFF state to the ON state, and in response to a loss of the auxiliary power, control the safety switch from the ON state to the OFF state; and
- a power device comprising: a power converter having inputs connected across the photovoltaic string, and a control circuit configured to control photovoltaic power generated by the pair of photovoltaic panels.
47. A method comprising:
- receiving, between first and second conductors of a safety switch, power;
- controlling, utilizing the power, the safety switch to an ON state that provides a direct-current serial path between the first and the second conductors; and
- controlling, in response to a loss of the power, the safety switch into the OFF state that disconnects the direct-current serial path.
48. A method comprising:
- receiving, at an output of a power converter, a first power line communication signal indicating for the power converter to shut down;
- controlling, based on receiving the first power line communication signal, the power converter from a first mode of operation that extracts photovoltaic power from a photovoltaic string according to a maximum power point tracking (MPPT) algorithm, to a second mode of operation that ceases to draw the photovoltaic power resulting in loss of photovoltaic current in the photovoltaic string, wherein the photovoltaic string comprises a plurality of photovoltaic panels coupled in series through one or more safety switches, and wherein each safety switch of the one or more safety switches is connected inline between a respective adjacent pair of the plurality of photovoltaic panels; and
- controlling, in response to the loss of photovoltaic current, the one or more safety switches from an ON state to an OFF state, wherein each safety switch of the one or more safety switches in the ON state provides a direct-current serial path between the respective adjacent pair of the plurality of photovoltaic panels to which the safety switch is connected, and in the OFF state disconnects the direct-current serial path.
Type: Application
Filed: Mar 16, 2023
Publication Date: Jul 13, 2023
Inventors: Yakir Loewenstern (Ariel), llan Yoscovich (Givatayim), David Braginsky (Yokne'am), Tzachi Glovinsky (Petah Tikva), Izak Assia (Shoham), Roy Shkoury (Rehovot)
Application Number: 18/185,028