Abstract: A method for providing control power for an electricity network in which at least one energy store connected to the electricity network supplies energy to the electricity network as required and/or takes up energy from the electricity network as required, the control power being delivered in dependence on a frequency deviation from a setpoint value of a network frequency, tolerance with respect to the amount of the control power to be provided being used to set a charging state of the energy store at a same time as providing control power by the energy store. A device for carrying out such a method includes a control system and an energy store, the device being connected or connectable to an electricity network, the control system being connected to the energy store and controlling control power given off and/or taken up by the energy store.

Abstract: A power distribution system that distributes power to electrical loads includes a switchgear apparatus that selectively routes power from one of two or more feeds to downstream portions of the system based upon commands received from a separate external switchgear controller device that receives data from various portions of the power distribution system. The switchgear controller device can operate in one or more separate operating modes, where commands to the switchgear apparatus are generated based upon user inputs or determinations made by an internal switchgear control module based at least in part upon the selected operating mode of the switchgear controller device. The operating mode can be set based upon user interaction with an operating mode interface. The switchgear control module may generate switchgear operation commands based at least in part upon data received from the switchgear apparatus and various portions of the power distribution system.

Abstract: An system and method to automatically disconnect a retrofit electrical unit from an electrical system in the event of an emergency situation and maintain power to the retrofit electrical unit.

Abstract: A hybrid thermal management system includes a battery, a capacitor, and a controller programmed to, responsive to a demand and a temperature being less than an upper threshold, select and operate only one of the battery and capacitor to satisfy the demand according to which of two values, corresponding to traction power dependent heat generation functions representing rates at which the battery and capacitor generate heat, is less to maintain the temperature below the threshold.

Abstract: In a fuel cell system which includes a fuel cell converter and a battery converter, noise generated in a high load region in particular is effectively inhibited, and silence is improved. A fuel cell system includes a fuel cell converter provided between a fuel cell and a load device, and a battery converter provided between a battery and the load device. The fuel cell system includes frequency setting means for setting a driving frequency band of the fuel cell converter and a driving frequency band of the battery converter so that these driving frequency bands do not overlap when a load of the load device is more than a predetermined threshold.

Abstract: A power supply conversion system receives an external power source to supply power to a load. The power supply conversion system includes at least one main power apparatus, at least one auxiliary power apparatus, a main switch, an auxiliary switch, and a control unit. The control unit turns on the main switch to restore the external power source when the control unit detects that the external power source is normally restored, and jointly supply power to the load with the auxiliary power apparatus. Especially, the output voltage of the main power apparatus is greater than the output voltage of the auxiliary power apparatus. In addition, the control unit disconnects the auxiliary power apparatus supplying power to the load when the control unit detects that the main power apparatus completely supplies power to the load.

Abstract: A method for controlling an electrical energy distribution network in which electrical power is provided via network nodes connected via power lines is provided. A portion of the network nodes are controllable network nodes with respective local controllers, and at least a portion of the controllable network nodes are energy generators. The energy distribution network is coupled to an energy transmission network at a point of common coupling and provides electrical power to the energy transmission network at the point of common coupling. The electrical power originates from the controllable network nodes. A central controller communicates with the local controllers and the energy transmission network. The central controller controls the energy distribution network with the aid of the communication with the local controllers and the energy transmission network such that at the point of common coupling, primary control power and short-circuit power are kept available for the energy transmission network.

Abstract: An energy storage system is provided that is adapted to simultaneously carry out control and system tasks in non-local and local power supply grids and to a method for operating such an energy supply system. The energy storage system has a modular structure and comprises more than one energy storage modules that are connected to each other via data lines. One of the energy storage modules is provided as master module and the others are provided as slave modules and the master module is configured for the overall control of all energy storage modules connected to the data line. At least the master module comprises at least one interface for receiving external control commands regarding the localized and non-localized control and system tasks to be carried out and a master control unit for storing and carrying out the external control commands.

Abstract: Featured are methods for regulating the AC frequency of the electrical power be supplied on an electrical distribution system or grid. Such a method includes electrically coupling an energy storage sub-system to the electrical distribution network, where the energy storage sub-system includes one or more flywheel energy storage systems. Also featured as devices, systems and apparatuses embodying such methodologies or for use in implementing such methodologies of the present invention.

Abstract: An object of the present disclosure is to provide a DC-to-DC converter with a simple circuit configuration that continues the supply of direct current power to a load without providing a redundant power supply circuit even if a switching transistor operates abnormally in the active state. A protection circuit unit that converts an input voltage of a direct current input power supply to a different direct current voltage obtained by stepping down the input voltage, as in a direct current voltage conversion circuit unit including a first switching transistor, is connected between the direct current voltage conversion circuit unit and the direct current input power supply and, if the first switching transistor operates in an active state, direct current power of the direct current voltage converted by the protection circuit unit is supplied to a load causing the first switching transistor to maintain operating in the active state.

Abstract: A switchgear controller device that generates commands to a switchgear apparatus that selectively routes power from one of two or more feeds to an electrical load of a power distribution system based upon the commands includes a user interface that displays graphical representations of various portions of the power distribution system. The switchgear controller device can receive data from components included in respective upstream portions and downstream portions of the power distribution system and generates graphical representations of present configurations of the components based at least in part upon the received data. Graphical representations of components included in the downstream portion of the system may be non-interactive, and graphical representations of components included in the upstream portion may be interactive based at least in part upon the present operating mode of the switchgear controller device.

Abstract: An embodiment is a circuit including a main power supply coupled to a first node, a charge reservoir coupled between a second node and ground, an isolation circuit coupled between the first node and the second node, and a plurality of secondary power supplies coupled to the second node, the plurality of secondary power supplies configured to receive power from the main power supply. The circuit further includes a detector circuit coupled to the first node, the detector circuit configured to detect the presence and absence of a first supply voltage at the first node, and a timing circuit coupled between the detector circuit and the plurality of secondary power supplies, the timing circuit configured to enable and disable the plurality of secondary power supplies in predetermined sequences based on the detection of the first supply voltage by the detector circuit.

Abstract: An expansion control circuit includes a delay circuit coupled to a first expansion module and a switching circuit coupled to a second expansion module. The switching circuit includes a buffer and a switching module. The buffer is coupled to the first expansion module. The first expansion module outputs a first control signal upon being switched on and outputs a second control signal after a working time. The delay circuit outputs a disconnecting signal upon being switched on. The buffer is switched off upon receiving the disconnect signal. The delay circuit further outputs a connecting signal after a delay time after outputting the disconnecting signal. The buffer is switched on upon receiving the connect signal. The buffer further outputs the second control signal to the switching module upon being switched on. The switching module controls the second expansion module to be switched on v receiving the second control signal.

Abstract: Wireless sensors configured to sense, record and transmit data are provided herein. In one aspect, the wireless sensor has a power harvesting unit; a transducing A-to-D converter unit, a microcontroller unit, and a transmitting coil. The power harvesting unit is configured to receive an external energizing magnetic field generated by an external interrogator and store the energy generated thereby. The transducing A-to-D converter unit has a passive electrical transducer configured to respond to variations in a physical property and a converter configured to measure a characteristic value of the passive electrical transducer and provide a digital signal that is indicative of the measured characteristic value. The microcontroller unit is electrically coupled to the power harvesting unit and the transducing A-to-D converter unit and is configured to receive the digital signal from the transducing A-to-D converter unit.

Abstract: A power supply device is connected to an external power supply and supplies electric power to a load. The power supply device includes a battery terminal that is used to connect a secondary battery, a superposition unit that superposes second electric power output from the secondary battery on first electric power supplied from the external power supply, and that outputs resultant electric power to the load; a power consumption amount retrieve unit that retrieves a power consumption amount of the load; and a controller that controls an amount of the second electric power to be output from the secondary battery, based on the power consumption amount.

Abstract: A distributed power system including multiple DC power sources and multiple power modules. The power modules include inputs coupled respectively to the DC power sources and outputs coupled in series to form a serial string. An inverter is coupled to the serial string. The inverter converts power input from the serial string to output power. A signaling mechanism between the inverter and the power module is adapted for controlling operation of the power modules.

Abstract: An image forming apparatus includes a fixing device to fix an image on a recording medium by heating the recording medium, multiple heat storing devices to store heat generated at the fixing device, an electric generating element to generate power by converting the heat into power, and a switch to switch connection and disconnection between the electric generating element and at least one of the multiple heat storing devices.

Abstract: In accordance with an embodiment, a method includes receiving by a drive circuit electrical power from a voltage tap of a first rectifier circuit that includes a load path and a voltage tap, and using the electrical power by the drive circuit to drive a second rectifier circuit that includes a load path. The load path of the first rectifier circuit and the load path of the second rectifier circuit are coupled to a common circuit node.

Abstract: An electronic ballast includes an AC-DC converter, a DC-DC converter, a cooling device and a power supply. The cooling device is configured to cool the light source. The power supply includes a first power supply configured to generate a first operating voltage from a first voltage obtained from a chopper circuit included in the AC-DC converter to supply the first operating voltage to at least one of the AC-DC converter and the DC-DC converter. The power supply further includes a second power supply configured to generate a second operating voltage from a second voltage obtained from the chopper circuit to supply the second operating voltage to at least the cooling device of the AC-DC converter, the DC-DC converter and the cooling device.

Abstract: A power control device forms energy storage equipment together with a storage battery. The power control device includes: a communication portion that communicates with a power management device, which manages charge and discharge of the storage battery; a power conditioner that supplies electricity to a predetermined destination for supply; a control portion that controls operation of the power conditioner based on instructions from the power management device that are received by the communication portion; and an authentication processing portion that performs authentication processing with the power management device.

Abstract: An activation control apparatus includes a voltage fluctuation obtainer to obtain voltage fluctuation amplitude of an external power source at a given voltage, the voltage fluctuation caused when activating an apparatus using the external power source; a voltage fluctuation detector to detect the voltage fluctuation of the external power source at the given voltage; an activation controller to determine whether the voltage fluctuation amplitude obtained by the voltage fluctuation obtainer at the given voltage of the external power source, detected by the voltage fluctuation detector, is within a preset allowable voltage fluctuation range, and to control activation of the apparatus using the external power source based on a result of the voltage fluctuation determination made by the activation controller.

Abstract: Some embodiments of the invention provide a method for balancing the power output to each phase of a set of micro-inverters. The method of some embodiments is performed by a gateway, which receives output messages from a plurality of micro-inverters. The gateway identifies the phase of each micro-inverter and calculates the output of the plurality of micro-inverters to each power line of a multi-phase system. The gateway then sends control signals to the micro-inverters to control the output of each micro-inverter to maintain a balanced aggregate power output to each phase of the power grid.

Abstract: An adaptive voltage scaling system includes first and second devices. Each of the first and second devices includes at least one master serial interface port and at least one slave serial interface port. The first device is operatively coupled to a voltage regulator, and the slave serial interface port associated with the second device is operatively coupled to the master serial interface port associated with the first device. The first device controls the voltage regulator based on information obtained from the first and second devices using the master serial interface port associated with the first device and the slave serial interface port associated with the second device. The first and second devices receive voltage from the voltage regulator. A corresponding method and computer-readable medium are also disclosed.

Abstract: A power system includes a Rankine cycle local generator having a capacity greater than a maximum anticipated power level. One or more control devices are operatively connected to the local generator for regulating active and reactive power generated by the generator. Detectors are provided to sense active and reactive voltages. The controller directs the control devices to regulate the generator such that the active power and reactive power are sufficient to satisfy the active and reactive load conditions.

Abstract: A control unit and a method for operating a safety system for a vehicle are proposed. A step-up converter configured as a switching converter is provided. The step-up converter converts an input voltage, which is derived from a vehicle battery voltage, into a higher charging voltage at its output. In addition, at least one energy reserve storage is provided which is charged via the charging voltage for operating the safety system in the case of autonomous operation. At least one step-down converter is operated inversely with respect to the step-up converter, the at least one step-down converter converting down the charging voltage or a voltage which is output by the at least one energy reserve storage.

Abstract: A power supply device includes: a main power supply configured to feed power to a load with constant-voltage output using an external power supply; an auxiliary power supply configured to feed power to the load using an internal power storage unit; a constant-current/constant-voltage switching power supply configured to feed a part of current flowing through the load by which part the current exceeds an upper limit value of output current of the main power supply instructed by a current upper-limit instruction unit, with the constant-current output from the auxiliary power supply; and an output switching unit switching the constant-current/constant-voltage switching power supply from the constant-current output to the constant-voltage output when a power cut monitoring unit determines stop of power supply from the external power supply.

Abstract: In the case that an auxiliary such as the air conditioner is operated with electric power from the commercial power supply by controlling the charger prior to the system startup and the inter-terminal voltage of the battery is more than or equal to the threshold value Vref that is a voltage where there is a possibility of overcharging the battery when the battery is charged, the supply voltage of the electric power supplied from the charger is set to the voltage that is a little smaller than the threshold value, and the auxiliary is operated with the electric power from the battery and the electric power from the charger. This arrangement enables to prevent overcharging the battery and to operate the auxiliary in the case that an auxiliary such as the air conditioner is operated with electric power from the commercial power supply by controlling the charger prior to the system startup.

Abstract: A vehicle ECU executes a program including the steps of determining whether or not to permit discharge assistance, generating first assistance information, transmitting the first assistance information, carrying out discharge control when a result of determination as to whether or not to request discharge assistance and requested discharge electric power is received and when measures based on the result of determination can be taken, and giving notification about whether or not discharge assistance is carried out.

Abstract: To include an internal voltage generating circuit that includes a capacitor having a first electrode and a second electrode and generates an internal voltage by repeating a charge operation for charging the capacitor to a VDD level and a discharge operation for applying the VDD level to the first electrode of the capacitor to generate a voltage of two times the VDD level on the second electrode, and a control circuit that performs a control to apply a voltage that is lower than the VDD level to the capacitor when the internal voltage generating circuit is in a standby state. According to the present invention, when the internal voltage generating circuit is in a standby state, because a voltage applied to both ends of the capacitor is reduced, it is possible to reduce the power consumption due to a leakage current.

Abstract: A hybrid engine and battery generator and a method of operating the same. The generator is controlled to operate in at least three modes: a battery-only mode, a battery charging mode, and a boost mode. In the battery-only mode, the engine is off and an internal battery of the generator is used by an inverter to generate AC output. In the battery charging mode, the engine generates DC power, via an alternator and rectifier, which is used to charge the battery and to supply power to the inverter to generate AC output. In the boost mode, the battery and the engine generate DC power that is used by the inverter to generate an AC output with increased wattage, relative to the battery-only mode and battery charging mode. The generator automatically switches between the modes based on battery level and load demand.

Abstract: A wearable device includes a sensor, auxiliary electronics, a primary power supply configured to harvest radio frequency (RF) radiation received from an external reader and use the harvested RF radiation to power the sensor, and an auxiliary power supply configured to harvest energy other than that received from the external reader and use the harvested energy to supply power to the sensor and/or the auxiliary electronics. The external reader may supply less power in response to operation of the auxiliary power supply. Additionally or alternatively, in response to a determination that the auxiliary power supply is unable to supply power, the wearable device may disable all auxiliary electronics but for the sensor. In response to a determination that the primary power supply is unable to supply power but the auxiliary power supply is able to supply power, the wearable device may retain operating parameters in the memory storage unit using the auxiliary power supply.

Abstract: A multi-energy storage device system is provided that includes a first energy storage device (ESD) coupled to a direct current (DC) link. A bi-directional buck/boost converter includes an output channel coupled to the DC link and an input channel. A second ESD coupled to the input channel has a usable energy storage range defining an entire amount of usable energy storable therein. A database includes stored information related to a known acceleration event. A system controller is configured to acquire the stored information related to the known acceleration event and, during the known acceleration event, cause the buck/boost converter to boost the voltage of the second ESD and to supply the boosted voltage to the DC link such that after the known acceleration event, the state of charge of the second ESD is less than or substantially equal to a minimum usable energy storage state of charge.

Abstract: One embodiment is an enhanced power supply including electronic power supply circuitry within a housing. The enhanced power supply further includes one or more sockets operatively associated with the housing providing for the connection of an external apparatus to the enhanced power supply such that the external apparatus may communicate data or another signal through the connection to an output cable. The output cable may to be connected to a device such that both power and at least one signal will be provided to the device through the output cable. Systems featuring an enhanced power supply and methods of providing power and one or more other signals to a device with a reduced number of cables are also disclosed.

Abstract: A power management apparatus and a method of operating the same are disclosed. The power management apparatus includes a power conversion unit, a first sensing unit, a second sensing unit, a switch unit, and a control unit. The power conversion unit converts output power generated from at least one renewable energy generation apparatus. The first sensing unit is provided to sense a first current and a first voltage and the second sensing unit is provided to sense a second current and a second voltage. The control unit acquires an output power generated from the renewable energy generation apparatus and acquires a feedback power to an AC utility according to the currents and the voltages when the control unit turns on the switch unit.

Abstract: An electrical power system includes a power grid and a plurality of power plants connected to the power grid. A central repository including one or more electrical energy storage devices is connected directly to the power grid. The one or more energy storage devices are configured to be connected to the power plants via the power grid. The central repository is operable to draw a portion of a power output produced by one or more of the power plants via the power grid during a first period, for storage therein. The central repository is operable to discharge power to the power grid during a second period shifted in time from the first period. The discharged power is a function of a grid requirement or a function of a power demand notified by an individual power plant of the electrical system.

Abstract: A variable capacitance circuit includes: a prescribed node, to which an alternate current signal with a reference potential as a center voltage is applied; a first capacitor connected to the prescribed node; a second capacitor connected between the first capacitor and the reference potential; a third capacitor and a transistor for controlling capacitance, provide between a first node between the second capacitor and the first capacitor, and the reference potential; and a bias circuit which applies a first bias voltage to a second node between the third capacitor and the transistor.

Abstract: The power supply includes a first power connector, a power conversion circuit, a control unit and a detection circuit. The first power connector includes a plurality of power terminals and a first detecting terminal. The power conversion circuit is coupled to the power terminals of the first power connector for converting an input voltage into an output voltage. The control unit is coupled to the power conversion circuit for controlling an operation of the power conversion circuit. The detection circuit is coupled to the control unit and the first detecting terminal of the first power connector for detecting if the first detecting terminal is connected or disconnected with a predetermined voltage terminal and correspondingly generating a power transmission status signal to the control unit.

Abstract: A system for exchanging energy wirelessly comprises an array of at least three objects having a resonant frequency, each object is electromagnetic (EM) and non-radiative, and generates an EM near-field in response to receiving the energy, wherein each object in the array is arranged at a distance from all other objects in the array, such that upon receiving the energy the object is strongly coupled to at least one other object in the array via a resonant coupling of evanescent waves; and an energy driver for providing the energy at the resonant frequency to at least one object in the array, such that, during an operation of the system, the energy is distributed from the object to all other objects in the array.

Abstract: A power flow regulator includes a plurality of bi-directional DC-DC converters, each of said converters comprising a first input, a second input, a first output and a second output; and a capacitor electrically connected between the first and second inputs of each of said converters. Either the first output of each of said converters is electrically connected to a corresponding DC source and the second output of each of said converters is electrically connected to a common DC load, or the first output of each of said converters is electrically connected to a corresponding DC load and the second output of each of said converters is electrically connected to a common DC source.

Abstract: A power supply device includes: a first line, a second line, and a third line, each having a different electric potential from one another; a battery circuit in which a fuel cell stack and an electric storage device are connected in series; and a first DC-DC converter, wherein both ends of the battery circuit are connected to the first line and the third line, a connection point of the electric storage device and the fuel cell stack of the battery circuit is connected to the second line, a primary side of the first DC-DC converter is connected to the second line and the third line, a secondary side of the first DC-DC converter is connected to the first line and the third line, and electric power is outputted from the first line and the third line.

Abstract: A method and system for limiting energy to a sensor and/or an environment in which the sensor is located. A high current sensor driver is powered through a resistance-capacitance (RC) circuit. In a failure mode, the RC circuit constrains output of a sensor driver to the sensor in order to limit average current applied to the sensor. In one embodiment, the capacitor is chosen so that it can provide adequate current to the sensor driver for a short period of time. The value of the resistor may be chosen to ensure that under short circuit conditions direct current (DC) is limited to a safe value. The combined values of the resistor and capacitor may be adjusted such that the capacitor can charge to a prescribed level during the interval between active pulses.

Abstract: An automatic breaker apparatus for the USB power supply, comprising a manual switch module, a relay, a high frequency transformer, a PWM power source master control module, a drive module, a signal filter module, an MCU master control module, a lighting instruction module and at least one USB power output end. When a user presses down the manual switch module, the relay becomes conductive, thus causing the electronic apparatus connected to the USB power source input end to be charged, and determining through the MCU master control module whether the electronic apparatus is using the electric current based on the pulsed filter signal outputted by the signal filter module thereby driving the relay to disconnect and also starting the lighting instruction module to generate light.

Abstract: A plurality of sodium-sulfur batteries are divided into a plurality of groups. Power to be input or output, which is assigned to all sodium-sulfur batteries in order to compensate for fluctuations of output power of a power generation device, is distributed to each group. The plurality of sodium-sulfur batteries divided in the groups are periodically rotated. This enables a uniform utilization rate of the sodium-sulfur batteries to be achieved.

Abstract: A power source of a bidirectional power system includes an energy storage device. Power can be transferred between the power source at a DC voltage and an electrical distribution network and/or a load at an AC voltage. A control system monitors for an islanding condition and, during normal operation, maintains an amount of power stored in the energy storage device and provides power to the load and/or network. Responsive to an islanding condition, power to the load can be maintained using the energy storage device, and the power system can be shut down and/or decoupled from the distribution network.

Abstract: An apparatus comprises a power electronic energy conversion system comprising a first energy storage device configured to store DC energy and a first voltage converter configured to convert a second voltage from a remote power supply into a first charging voltage configured to charge the first energy storage device. The apparatus also includes a first controller configured to control the first voltage converter to convert the second voltage into the first charging voltage and to provide the first charging voltage to the first energy storage device during a charging mode of operation and communicate with a second controller located remotely from the power electronic energy conversion system to cause a second charging voltage to be provided to the first energy storage device during the charging mode of operation to rapidly charge the first energy storage device.

Abstract: A multiple power supply device including a power consuming unit, a plurality of power supply units, and a plurality of switching units is provided. The power consuming unit receives a plurality of power good signals, and outputs a plurality of power control signals accordingly. The power supply units output a plurality of working voltages respectively, and meanwhile output the power good signals. When the power consuming unit is in a working state and one of the power good signals is enabled, the power consuming unit enables the corresponding power control signal. When the power consuming unit is in a working state and a part of the power good signals are enabled, the power consuming unit enables one of the power control signals corresponding to the enabled power good signals. The switching units transmit the corresponding working voltage to the power consuming unit according to the enabled power control signal.

Abstract: A direct current generating, management and distribution system includes a first armature winding, a first active rectifier having a first controller and coupled to the first armature winding, a first direct current bus coupled to the first active rectifier, a second armature winding, a second active rectifier having a second controller and coupled to the second armature winding, a second direct current bus coupled to the second active rectifier, a unit controller coupled to the first and second controllers, a first set of switches coupled to the first direct current bus and to the unit controller, a second set of switches coupled to the second direct current bus and to the unit controller, a third switch coupled to the first direct current bus and to the unit controller and a fourth switch coupled to the second direct current bus and the unit controller.

Abstract: A switching power source apparatus includes a first arm including first and second switching elements, a second arm including third and fourth switching elements, a series circuit connected between a connection point of the first and second switching elements and a connection point of the third and fourth switching elements and including a capacitor and a primary winding, a rectifying-smoothing circuit that rectifies and smoothes a voltage of a secondary winding and provides an output voltage, a reactor connected to a connection point of the first and second switching elements and a DC input end, and a controller that turns on/off the first and second switching elements alternately and the third and fourth switching elements alternately and synchronizes the first and third switching elements with each other and the second and fourth switching elements with each other.

Abstract: A method and apparatus for an electrical bus leveling unit are provided. The electrical bus leveling unit includes a first power supply configured to generate electrical energy having a first set of electrical parameters and a power converter electrically coupled to said power supply. The power converter is configured to be coupled to an electrical bus couplable to a second power supply. The electrical bus leveling unit also includes a controller including a processor that is communicatively coupled to the power supply and the power converter The controller is configured to receive information relating to the operation of the electrical bus from a plurality of sensors, control an output of at least one of the power supply and the power converter to transfer electrical energy to the electrical bus when the second set of electrical parameters on the electrical bus is outside a predetermined range.

Abstract: A method of converting a direct voltage generated by a decentralized power supply system into three-phase alternating voltage by means of a plurality of single-phase inverters (WR1-WR3), said alternating voltage being provided for supplying an electric mains, is intended to avoid inadmissible load unbalances using single-phase inverters. This is achieved in that, upon failure of one inverter (WR1-WR3), an asymmetrical power supply distribution is reduced by limiting the output of the other inverters. The method makes it possible to simplify three-phase voltage monitoring.