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.

Abstract: A power system and a method for starting a power system. The power system includes a first alternating current bus, a plurality of alternating current power supply units, a plurality of switch units, and at least one controller. The controller is configured to: start a primary alternating current power supply unit to output an alternating current voltage to the first alternating current bus, control a secondary alternating current power supply unit to output an alternating current voltage in an open-circuit state, and control the secondary alternating current power supply unit to output a voltage to the first alternating current bus when a bus voltage value is greater than or equal to a second threshold and is still in a rise phase.

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 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.

Abstract: A power converter control method includes: determining a phase angle difference between a phase angle of a voltage output by the power converter and a phase angle of a power grid voltage; and if the phase angle difference is greater than or equal to a first angle threshold, setting a d-axis current reference value and a q-axis current reference value that are used to determine a modulation voltage of the power converter to preset fixed values; calculating a first modulation voltage of the power converter based on the d-axis current reference value, the q-axis current reference value, and a power grid current; calculating a compensation voltage of the power converter based on a preset virtual resistance parameter and the power grid current; and using a sum of the first modulation voltage and the compensation voltage as a total modulation voltage.

Abstract: A converter circuit is configured to output a first reactive current to a power grid when a voltage value of an output port of the converter circuit decreases from a first working voltage value to a second working voltage value. The drive control circuit is configured to: in a process in which the converter circuit outputs the first reactive current to the power grid, when it is detected that the voltage value of the output port of the converter circuit increases to a third working voltage value and the third working voltage value is greater than or equal to a first recovery voltage value, control the converter circuit to output a second reactive current to the power grid, to recover the voltage value of the output port of the converter circuit to the first working voltage value.

Abstract: The photovoltaic power generation system includes a controller and M groups of DC-DC circuits. Each group of DC-DC circuits include N DC-DC circuits, where M is a positive integer, and N is an integer greater than 1. An input end of each DC-DC circuit is connected to at least one photovoltaic unit, and each photovoltaic unit includes at least one photovoltaic module. The controller controls the N DC-DC circuits in each group of DC-DC circuits to sequentially start online IV curve scanning and controls a time interval at which two adjacent DC-DC circuits start online IV curve scanning to be less than duration of online IV curve scanning performed by one DC-DC circuit. The photovoltaic power generation system can reduce a fluctuation of a power output during online IV curve scanning, reduce duration of online IV curve scanning performed by the photovoltaic power generation system.

Abstract: A power converter and an inverter circuit control method. A modulation signal is output in a bipolar modulation scheme near a zero-crossing point of the modulation signal of an inverter circuit, to prevent some modulation signals from being lost due to reasons such as minimum on time and dead time of a switching transistor in the inverter circuit, and further prevent an output voltage of the inverter circuit from being distorted near the zero-crossing point. When a three-phase inverter circuit performs discontinuous pulse width modulation, a zero-crossing interval is prolonged, and distortion of the output voltage of the inverter circuit is more clear. In this case, quality of electric energy can be better improved by outputting the modulation signal in the bipolar modulation scheme.