Abstract: An input end of each DC-DC conversion circuit in the photovoltaic system is connected to a corresponding photovoltaic string. Output ends of a plurality of DC-DC conversion circuits are connected in parallel to an input end of a DC-AC conversion circuit. A controller performs a partial IV curve scan on each of the DC-DC conversion circuits, and in a scanning process, controls a total input power of the plurality of DC-DC conversion circuits to be consistent with that existing before the scan; and obtains a sum of the maximum input powers of all the DC-DC conversion circuits based on the maximum input power of each of the DC-DC conversion circuits, where a scanned voltage of the partial IV curve scan is less than an open-circuit voltage. The partial IV curve improves scanning efficiency and obtains a maximum input power in a power-limited state, facilitating subsequent power dispatch and control.

Abstract: A common-mode voltage injection control method and apparatus for an inverter. For the method and apparatus, a common-mode voltage for a DPWM mode is calculated based on three-phase port voltages and an output power command; a common-mode voltage for an MPC modulation mode is calculated based on the direct current bus voltage, the three-phase port voltages, and the output power command; a modulation proportion is determined based on a maximum phase voltage peak value of the three-phase port voltages, the direct current bus voltage, and a power factor of the output power command; and a common-mode injection voltage is generated based on the common-mode voltage for the DPWM mode, the modulation proportion, and the common-mode voltage for the MPC modulation mode.

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: A power supply system, a three-phase inverter, and a controller and a control method for a three-phase inverter. In the power supply system, after a low-voltage failure occurs in a power grid, a three-phase inverter outputs a first positive-sequence reactive current to the power grid through low voltage ride-through. When a voltage of at least one of three alternating currents output by the three-phase inverter is greater than a preset threshold, the three-phase inverter outputs a small second positive-sequence reactive current to the power grid through the three alternating currents, to reduce a voltage at an output end of the three-phase inverter and improve stability of the entire power supply system.

Abstract: A power converter includes a power conversion circuit, a bus capacitor, and a controller. A direct current input end of the power conversion circuit is configured to connect to a direct current power supply through a direct current bus. An alternating current output end of the power conversion circuit is configured to connect to an alternating current power grid through a point of common coupling (PCC). The controller is configured to: in response to that a difference between a voltage across two ends of the positive bus capacitor and a voltage across two ends of the negative bus capacitor is greater than a specified threshold, control the power converter to inject a second harmonic current into the alternating current power grid, to reduce the difference between the voltage across the two ends of the positive bus capacitor and the voltage across the two ends of the negative bus capacitor.

Abstract: A power supply system, a converter, and a circulating current suppression method of the converter. The power supply system includes at least two converters that are coupled between a direct current power supply and an alternating current grid. Each converter obtains target output reactive power when an output current of the converter starts to increase from an initial current, obtains a reactive power compensation parameter based on the three-phase output voltages. Further, each converter obtains compensated output reactive power of the converter based on the reactive power compensation parameter and adjusts actual output reactive power of the converter based on the target output reactive power and the compensated output reactive power, so that an absolute value of a difference between common-mode output voltages of any two of the at least two adjusted converters is less than a difference threshold.

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: A power supply system and a grid connection control method. The power supply system includes a power supply, an inverter, a transformer, a power station collection module, and an inverter collection control circuit. The inverter collection control circuit is configured to obtain an amplitude value and a frequency of an output voltage of the inverter, obtain an inverter power adjustment signal based on the amplitude value and the frequency of the output voltage, and control, based on the power station power adjustment signal and the inverter power adjustment signal, the inverter to output a target output power. Additionally, an output power of the inverter may be adjusted by using the power station collection module and the inverter collection control circuit. A structure is simple, and a control method is simple. This improves control precision and adjustment efficiency, reduces control time, and reduces control costs.

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: A fault detection apparatus includes an image capture module and a detection module, and the fault detection apparatus is configured to capturing an image of the photovoltaic module in a light emitting state, and performing fault detection on the photovoltaic module based on the image when a signal-to-noise ratio of the image is maximized, to identify a fault type of the photovoltaic module.

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: A power supply system for controlling the power supply system includes a direct current voltage conversion apparatus, an inverter, and a diode. The direct current voltage conversion apparatus includes a controller and a direct current voltage conversion circuit. The controller is configured to: control the output voltage of the direct current voltage conversion circuit, so that the diode is in a conducted state; detect a voltage on the direct current bus; and determine, based on the voltage on the direct current bus, whether high voltage ride-through occurs in the power supply system. According to the power supply system and the method for controlling the power supply system provided in this application, high voltage ride-through can be quickly detected while fault isolation is implemented, thereby improving efficiency of detecting high voltage ride-through.

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: This application discloses a photovoltaic system and a carrier wave signal synchronization method. The photovoltaic system includes a plurality of inverters and a controller. Each inverter in the photovoltaic system inverts a direct current into an alternating current based on a received carrier wave signal, and transmits the alternating current to a power grid. The controller obtains first output currents of the plurality of inverters in an adjustment period, so that the controller can obtain first output current valid values of the plurality of inverters based on the first output currents of the plurality of inverters.

Abstract: A multi-inverter parallel system are provided. The system includes a first inverter and a second inverter. The first inverter includes a first controller, a first inverter circuit, and a first relay. The second inverter includes a second controller, a second inverter circuit, and a second relay. Phases of an output end of the first inverter circuit are correspondingly connected to phases of an output end of the second inverter circuit. The first controller may control the first relay to be turned on. The second controller may control, when the second relay is turned off, a direct current bus voltage of the second inverter circuit to be the same as a direct current bus voltage of the first inverter circuit, and control a common-mode voltage injection manner of the second inverter circuit to be the same as a common-mode voltage injection manner of the first inverter circuit.

Abstract: The embodiments provide an RSCC and a control method thereof. The RSCC includes an input capacitor, an output capacitor, N parallel RSC branches, and a controller. The controller is configured to: determine an average value of characteristic currents of N resonance units; and reduce a duty cycle of a control signal of a charging switch in a first switch unit when determining that a characteristic current of a first resonance unit is greater than the average value, where a corresponding branch is in a charging stage when the charging switch is turned on; or reduce a duty cycle of a control signal of a discharging switch in a first switch unit when determining that a characteristic current of a first resonance unit is less than the average value, where a corresponding branch is in a discharging stage when the discharging switch is turned on.

Abstract: A power line communication (PLC) system includes a PLC signal transmitting end, a PLC signal receiving end, and a power electronic apparatus. The PLC signal transmitting end is connected to the PLC signal receiving end through a power line, and the power electronic apparatus is connected to the power line. The power electronic apparatus is configured to increase output impedance in a first PLC communication frequency band, to reduce interference from an output current of the power electronic apparatus to a PLC signal in the first PLC communication frequency band. The first PLC communication frequency band is a PLC communication frequency band in which the PLC signal transmitting end sends the PLC signal to the PLC signal receiving end. In this way, the interference from the power electronic apparatus to the PLC signal in the first PLC communication frequency band can be reduced without adding an additional passive filter.

Abstract: A voltage conversion unit includes a positive voltage conversion apparatus and a negative voltage conversion apparatus. The inverter unit includes a positive inverter and a negative inverter. A negative output end of the positive voltage conversion apparatus and a positive output end of the negative voltage conversion apparatus are connected to a first end of a neutral wire, and a negative input end of the positive inverter and a positive input end of the negative inverter are connected to a second end of the neutral wire. When the neutral wire current does not meet the preset current range, the controller control the positive voltage conversion apparatus and the negative voltage conversion apparatus to change output voltages when output power remains unchanged, so that the neutral wire current meets the preset current range.

Abstract: A grid-tied power supply system includes a controller and at least two inverters. One inverter is coupled to a plurality of power supply modules. The controller is configured to determine a power parameter. The inverter receives a power control packet through a communication transmission medium, determines target power based on the power parameter carried in the power control packet, and determines, based on the power control packet and/or the communication transmission medium, a target adjustment manner corresponding to the power control packet from at least two adjustment manners. The inverter further adjusts, to the target power in the target adjustment manner, power to be output by the inverter to an alternating-current (AC) power grid. The inverter can directly adjust power to be output by the grid-tied power supply system to the alternating-current power grid.

Abstract: A power supply system, an inverter, and a method for controlling positive and negative bus voltages of an inverter. The power supply system includes at least one group of inverters, each group of the at least one group of inverters includes a primary inverter and at least one secondary inverter corresponding to the primary inverter, an input end of the primary inverter is coupled to a direct current power supply corresponding to the primary inverter, an input end of the secondary inverter is coupled to a direct current power supply corresponding to the secondary inverter, and a three-phase output end of the primary inverter is coupled to a three-phase output end of the secondary inverter and then is connected to an alternating current power grid.