Abstract: A photovoltaic inverter includes a conversion circuit, a collection circuit, and a controller. The collection circuit is configured to obtain a positive direct current bus voltage and a negative direct current bus voltage of the conversion circuit. The controller is configured to generate an even-order harmonic voltage regulation signal based on the positive direct current bus voltage and the negative direct current bus voltage of the conversion circuit and a phase of an output voltage of the photovoltaic inverter, generate a drive control signal based on the even-order harmonic voltage regulation signal, and control a switching transistor in the conversion circuit to be turned on or off to control the conversion circuit to output a target voltage and reduce a difference between the positive direct current bus voltage and the negative direct current bus voltage of the conversion circuit.

Abstract: Examples of power conversion devices and control methods are described. In one example, a power conversion device includes direct current buses, an inverter circuit, and a controller. After the power conversion device switches from a high voltage ride through state to a low voltage ride through state, the controller controls a change rate of an output active current of the inverter circuit to be a first change rate in a first time interval and a second change rate in a second time interval respectively in a low voltage ride through reactive current response process. The second change rate is greater than the first change rate. A sum of first interval duration of the first time interval and second interval duration of the second time interval is less than or equal to a low voltage ride through reactive current response duration threshold.

Abstract: Example power converters and detection methods are described. One example power converter includes a control device, a plurality of wiring terminals, a power conversion circuit, and a plurality of temperature detection devices. The control device is configured to: when an absolute value of a difference between a temperature value of one wiring terminal in the plurality of wiring terminals and a first reference temperature value is greater than or equal to a first temperature difference threshold, output a signal indicating that an abnormality occurs in the plurality of wiring terminals. In this application, a relative change of a temperature of one wiring terminal relative to another wiring terminal can be directly determined based on temperature values of the plurality of wiring terminals, thereby quickly determining, based on a magnitude of the relative change, whether there is an abnormal temperature rise caused by loose connections in the plurality of wiring terminals.

Abstract: An energy storage power generation system and a control method thereof. When a transient fault occurs in the power grid, the plurality of power conversion systems may enter a transient-state operating mode from a steady-state operating mode, and a parallel expansion multiple of the energy storage power generation system is less than a transient overload multiple. In embodiments, a physical characteristic of transient overloading and a short-time overload capability of the power conversion system are fully used, and the power grid is supported when a power grid fault is detected. This solution simplifies an architecture of the system and increases efficiency of the system. It is easy to understand that because a quantity of power conversion systems is reduced and costs of the system are also reduced.

Abstract: The photovoltaic system includes an inverter, a fan, and a controller. A photovoltaic string and a direct current bus capacitor are connected between a positive input end and negative input end of the inverter. The controller receives a fast shutdown instruction and sends a drive signal to a switching transistor in the inverter, so that the switching transistor performs a switching action under the action of the drive signal, and the switching transistor consumes electric energy during the switching action; or the controller turns on the fan after receiving the fast shutdown instruction to consume electric energy by using the fan; or the controller may send the drive signal to the switching transistor and also control the fan to be turned on, so that both the switching transistor and the fan consume electric energy.

Abstract: A power conversion apparatus includes a direct current end, a positive direct current bus, a negative direct current bus, a positive bus capacitor, a negative bus capacitor, at least three inverter bridge arms, a switch unit, a controller, and filter inductors, filter capacitors, and alternating current ends that correspond to the at least three inverter bridge arms. A third end of each inverter bridge arm sequentially passes through a filter inductor, a filter capacitor, and a switch unit that correspond to each inverter bridge arm, and is connected to a bus midpoint. The controller is configured to: when a voltage of a power grid is less than or equal to a first voltage threshold, control the switch unit to be turned off or impedance of the switch unit to be increased; then control a amplitude of the modulated wave of each inverter bridge arm to increase.

Abstract: A power converter includes a power conversion circuit, an output inductor, and a controller. Each half bridge arm in an upper half bridge arm and a lower half bridge arm included in the power conversion circuit includes at least two switching transistors. The controller is configured to: when the carrier wave is in a zero-crossing point region, control a switching transistor of the upper half bridge arm to keep an on/off switching state unchanged and control to prevent the switching transistors of the lower half bridge arm from performing an action, and control a switching transistor of the upper half bridge arm to perform on/off switching at a moment at which the carrier wave enters the zero-crossing point region.

Abstract: A three-level inverter includes controllable switch components T1 to T6. Each of the controllable switch components includes a parallel connected junction capacitor and an anti-parallel connected diode. A first terminal of T1 is connected to a positive direct current bus, a second terminal of T4 is connected to a negative direct current bus, a second terminal of T1 is connected to first terminals of T2 and T5. A controller is configured to: in a positive half cycle, control T3 to be conducted after T1 is conducted, and control T3 to be disconnected before T1 is conducted next time; and in a negative half cycle, control T2 to be conducted after T4 is conducted, and control T2 to be disconnected before T4 is conducted next time. The three-level inverter can balance voltages of the controllable switch components.

Abstract: An inverter and a control method for the inverter. The inverter includes a direct current conversion circuit, a direct current bus, an inverter circuit, and a controller. An input end of the direct current conversion circuit is connected to an input end of the inverter, an output end of the direct current conversion circuit is connected to an input end of the inverter circuit through the direct current bus, and an output end of the inverter circuit is connected to an output end of the inverter. The controller obtains a reactive voltage control amount based on actual output active power and reference output active power of the inverter circuit and adjusts an output voltage of the inverter circuit based on the reactive voltage control amount and a reference output voltage.

Abstract: When a frequency of an alternating current power grid has a first frequency, a grid-connected power converter adjusts an output power of a power conversion circuit from a preset reference power to a first power, where the first power is a sum of the preset reference power and a first inertia power. When the frequency of the alternating current power grid has a second frequency, the grid-connected power converter adjusts the output power of the power conversion circuit from the first power to a second power, where the second power is a sum of the first power and a first frequency regulation power, and an absolute value of a difference between the second frequency and a utility frequency of the alternating current power grid is greater than an absolute value of a difference between the first frequency and the utility frequency of the alternating current power grid.

Abstract: A photovoltaic system and a circulating current suppression method. The system includes a controller and at least two inverters. A direct current input terminal of each inverter is connected to a corresponding photovoltaic array. Alternating current output terminals of the at least two inverters are connected in parallel. The controller is configured to: obtain a direct current component of a common-mode output current of at least one of the at least two inverters and adjust a direct current bus voltage of the corresponding inverter based on a magnitude of the direct current component of the common-mode output current, to suppress a circulating current between the at least two inverters. A circulating current between a plurality of inverters connected in parallel can be suppressed, thereby reducing loss caused by a circulating current, and improving power supply efficiency.

Abstract: A direct current converter includes a three-level power switching circuit, a resonant circuit, and a controller. An output voltage at an output end of the three-level power switching circuit is used to charge the resonant circuit. The controller is configured to control power switching components in the three-level power switching circuit, so that when the resonant circuit performs charging or discharging at one half of a direct current voltage, one of the power switching components is connected to a current loop of the resonant circuit, and when the resonant circuit performs charging or discharging at the direct current voltage, two of the power switching components are connected to the current loop of the resonant circuit. By using the direct current converter, a voltage borne by the power switching component in the direct current converter during current conversion can be reduced, thereby improving reliability of the direct current converter.

Abstract: A power converter and a method. When the voltage at the grid connection point exceeds the preset voltage range and an amplitude of a voltage output by the power conversion circuit is not greater than a voltage threshold, embodiments can control the amplitude of the current output by the power conversion circuit to be not greater than a second current threshold, where the second current threshold is greater than the first current threshold, and a ratio of an active current to a reactive current output by the power conversion circuit is constant or changes; or, when the amplitude of the voltage output by the power conversion circuit is greater than the voltage threshold, embodiments can control the amplitude of the current output by the power conversion circuit to be equal to the second current threshold, where the ratio of the active current to the reactive current changes.

Abstract: The field of power systems includes a switching control method for a converter apparatus in a power supply system and the apparatus. This solution may be applied to a power conversion system in scenarios such as a new energy microgrid or an electrochemical energy storage station. In the method, a voltage of the converter apparatus at a control switching moment is stored, the voltage is used as an initial value after switching is performed, and the voltage is transited to a rated voltage in a first time period.

Abstract: An output end of a power converter is connected to a microgrid bus, and the microgrid bus is connected to an external power grid through a grid-tied switch. When detecting that a power grid fails, the power converter is in a first current source control mode. After a duration of the power grid failure reaches a first duration, the power converter switches from the first current source control mode to a first voltage source control mode. The first current source control mode is a current source failure ride-through control mode. The first voltage source control mode is a voltage source failure ride-through control mode. The first duration is less than a second duration, and the second duration is a time interval between a moment at which the power grid fails and a moment at which the grid-tied switch is turned off.

Abstract: A direct current end of the power converter is configured to connect to a photovoltaic module or an energy storage battery, and an alternating current end of the power converter is configured to connect to a load or a power grid. The power converter includes a power conversion circuit and a controller. The power conversion circuit is configured to convert a direct current into an alternating current. The controller is configured to: during black start of the power converter, first control a voltage amplitude of the alternating current output by the power conversion circuit to be increased at a first rate, and then control the voltage amplitude of the alternating current output by the power conversion circuit to be increased at a second rate, where the second rate is greater than the first rate.

Abstract: A photovoltaic system, a relay detection method, and a power supply system. When a fault, for example, sticking of the relay is detected, the controller stops sending a PWM driver gating signal to the inverter, and stops driving of a switch transistor in the inverter, and the inverter stops outputting power, and then determines whether a voltage difference between two ends of the relay is greater than a preset value, to determine whether the relay is faulty. The controller stops sending the PWM driver gating signal to the inverter only within a preset phase range of a voltage of the filter capacitor, to ensure that the voltage of the filter capacitor has a large value. Because the voltage of the filter capacitor is large, an alternating current grid-to-ground voltage is pulled up, to avoid detecting the fault as an alternating current grid-to-ground short circuit.

Abstract: This application describes examples of a grid-tied inverter apparatus and a grid-tied control method. In one example, the grid-tied inverter apparatus includes an inverter circuit, a controller, and a filter circuit. The controller is configured to adjust switching frequencies of a plurality of power switching transistors based on an output current value of the inverter apparatus, to adjust a resonance frequency of the filter circuit through different resonant branches, so that the resonance frequency meets a grid-tied requirement.

Abstract: An energy storage power generation system and a control method thereof. When a transient fault occurs in the power grid, the plurality of power conversion systems may enter a transient-state operating mode from a steady-state operating mode, and a parallel expansion multiple of the energy storage power generation system is less than a transient overload multiple. In embodiments, a physical characteristic of transient overloading and a short-time overload capability of the power conversion system are fully used, and the power grid is supported when a power grid fault is detected. This solution simplifies an architecture of the system and increases efficiency of the system. It is easy to understand that because a quantity of power conversion systems is reduced and costs of the system are also reduced.

Abstract: An exhaust trap configured to filter an exhaust stream of a vacuum furnace may include a housing and a media barrier. The housing defines an interior. The media barrier may divide the interior of the housing into a first chamber and a second chamber and is configured to allow the exhaust stream to flow from the first chamber to the second chamber. The exhaust trap may further include a filter medium in the first chamber and configured to filter the exhaust stream. No filter medium is present in the second chamber.