Abstract: A grid connection inverter system includes a converter, an additional damping controller, a sampling circuit, and a controller. The converter is configured to output a grid connection voltage, a grid connection current, and power to the power grid. The sampling circuit is configured to detect the grid connection voltage, the grid connection current, and a power grid frequency of the power grid. The additional damping controller is configured to output a power additional value to the controller based on the grid connection voltage and the power grid frequency when the power grid is in a low-frequency oscillation state, where the power additional value includes an active power additional value and a reactive power additional value. The controller is configured to adjust, based on the power additional value, reactive power and active power that are output by the converter.

Abstract: This application provides a power supply system and a grid-forming control method, to increase a frequency synchronization speed of a grid-forming power generation device. The power supply system may include at least one new energy power generation device. The new energy power generation device may include a power converter and a control apparatus. The control apparatus may output an output voltage phase of the power converter based on a difference between a target output parameter of the power converter and an output parameter at a point of coupling, and adjust the output voltage phase of the power converter when a phase difference of a voltage at the point of coupling within a threshold time is greater than a preset threshold.

Abstract: An energy storage system (ESS) includes an energy storage unit, a power conditioning system (PCS), a frequency detection circuit, and a controller. The controller performs first/second frequency adjustment control on the PCS, adjusts a weight of the first/second frequency adjustment control based on a frequency difference between a frequency of an output voltage of the power conditioning system and a target frequency, controls the frequency of the output voltage of the power conditioning system to be the target frequency, and detects that islanding occurs in the power conditioning system. After islanding occurs in the power conditioning system in the energy storage system, the controller can adjust the frequency of the output voltage of the power conditioning system in which islanding occurs to the target frequency, so that islanding can be detected and an anti-islanding protection action can be completed.

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 power supply system includes N distributed generations and at least one detection control unit. The N distributed generations are connected in parallel or in series and then connected to a power grid, and N is an integer greater than 1. The detection control unit is configured to: when detecting that oscillation of the power supply system exceeds a preset threshold range, obtain a power compensation control proportion of each distributed generation based on impedance from each distributed generation to a point of common coupling of the power supply system. The power compensation control proportion is a proportion of power output by each distributed generation to total power output by the power supply system. The detection control unit is further configured to control a power output proportion of each distributed generation based on the power compensation control proportion.

Abstract: A photovoltaic power generation system and a photovoltaic power generation system control method, to implement fast frequency support. The photovoltaic power generation system includes: a direct current converter, configured to connect an output of a photovoltaic module and perform voltage conversion on a direct current output by the photovoltaic module; an inverter, configured to convert a direct current output by the direct current converter into an alternating current and output the alternating current to a power grid; and a first controller, configured to generate a first drive signal based on two of a first voltage of the direct current of the direct current converter, an active power output by the inverter, and an operating parameter of the power grid, and control an operating state of the inverter based on the first drive signal.

Abstract: A power converter includes a direct current conversion circuit, an inverter circuit, and a controller. An input of the direct current conversion circuit is configured to connect to the photovoltaic module, and an output of the direct current conversion circuit is connected to a bus capacitor of the inverter circuit. The controller is configured to change output power of the photovoltaic module. When power of the load is less than a specified threshold, the power converter is controlled to reduce the output power of the photovoltaic module from operating power to zero for at least once, where the operating power is greater than zero and less than rated output power, and when the output power of the photovoltaic module is the operating power, the power converter operates in a maximum power point tracking (MPPT) mode.

Abstract: This application discloses examples of an energy storage system, a power conversion system, and a method for optimizing primary frequency modulation. In one example, when the power conversion system determines that a state of charge (SoC) value of a target energy storage battery does not meet a target SoC value and determines that a present frequency of a power grid falls within a frequency modulation constant band, the power conversion system determines, based on a preset mapping relationship between a SoC value and an active power, a first specified active power value corresponding to the SoC value of the target energy storage battery, and controls, based on the first specified active power value, the target energy storage battery to be charged or discharged, so that the SoC value of the target energy storage battery can reach the target SoC value.

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 power conversion system including N power conversion units and a control unit, which can control, in a control periodicity, operating modes of one or more target power conversion units in the N power conversion units to be switched between a PR mode and an MPPT mode, and update a reference power based on a maximum power obtained in the MPPT mode, for an operating power of the target power conversion unit obtained in the PR mode to be an updated reference power, and the updated reference power is less than or equal to the maximum power. In addition, the control unit further controls an operating mode of a power conversion unit other than the target power conversion unit in the N power conversion units to remain unchanged, so that the power conversion unit other than the target power conversion unit does not perform mode switching.

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 embodiments include a power converter including a DC/AC conversion unit. A direct current bus is connected to the DC/AC conversion unit and a direct current source. The DC/AC conversion unit is further connected to a power grid. When a direct current bus voltage is less than or equal to a first voltage threshold, the power converter may switch to a current source mode to output first output power to the power grid, where the first output power is equal to an output power limit of the direct current source. Then, if a fluctuation amplitude of the direct current bus voltage is less than or equal to a first fluctuation threshold, the power converter may resume outputting second output power to the power grid in a voltage source mode, so that the second output power is less than or equal to the output power limit of the direct current source.

Abstract: A power conversion apparatus and a control method for a power conversion apparatus to reduce an amplitude of an output voltage of a converter when a grid is recovered from a fault, to ensure device safety. The power conversion apparatus includes a controller and a converter, and the controller is connected to the converter. The controller is configured to: after the output voltage of the converter is less than a first threshold, when the output voltage of the converter rises to be greater than a second threshold, reduce an active current output by the converter to a first current value, and reduce a reactive current output by the converter to a second current value, where the second threshold is greater than the first threshold.

Abstract: A method includes: performing one or more adjustments on a filter parameter based on battery information of the ESS that is at a first control moment, and performing one or more times of power filtering by the filter, until a power fluctuation rate determined based on a power obtained through filtering is less than or equal to a preset threshold; and determining, based on the power obtained through filtering, a given power of the ESS that is at the first control moment. During smooth control of a power, a relationship is established between battery information and a filter characteristic, so as to prevent a battery from quickly reaching a fully charged state or a fully discharged state.

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: A control method of a three-phase multi-level inverter includes: determining a modulation ratio based on output of the three-phase multi-level inverter, where the modulation ratio indicates a ratio of an amplitude value of a sinusoidal modulation wave in pulse width modulation to an amplitude value of a carrier; generating, based on the modulation ratio and a modulation ratio threshold, a common-mode voltage regulation signal for regulating a common-mode voltage in phase voltages of the three-phase multi-level inverter; adding the common-mode voltage regulation signal and a differential-mode voltage regulation signal for regulating a differential-mode voltage in the phase voltages of the three-phase multi-level inverter to obtain a composite regulation signal, where the composite regulation signal is presented as a modulation wave for discontinuous pulse width modulation (DPWM); and generating, based on the composite regulation signal, drive signals for controlling switches of phases of the three-phase multi-

Abstract: The present disclosure provides for a system for measuring optical properties of liquid samples. The system includes a housing having a multi-wavelength light source, a collimator, a beam-splitter, and a light sensor. A probe extends from the housing, The probe includes a sample inlet configured to receive a liquid sample. The multi-wavelength light source is positioned to direct light to the collimator, the collimator is positioned to direct light to the beam-splitter, the beam-splitter is positioned to direct light to the probe, and the light sensor is positioned to receive light transmitted through the probe.

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.