Abstract: A system for protecting a grid-connected photovoltaic inverter may include a detection device, a photovoltaic panel, an inverter, a transformer and an inverter controller. An output terminal of the photovoltaic panel is connected to an input terminal of the inverter, the inverter inverts a direct current into an alternating current and transmits it to the transformer a secondary side of the transformer is connected to an output terminal of the inverter, and a primary side is connected to a power grid. The primary side of the transformer is star-connected, and a neutral point is grounded. The detection device is connected between the primary side and the power grid, and is configured to detect whether a single-phase open-circuit fault occurs at the primary side and transmit a fault signal to the inverter controller. The inverter controller is configured to control the inverter to stop according to the fault signal.

Abstract: A three-level photovoltaic inverter pulse width modulation method and a three-level photovoltaic inverter pulse width modulator. The method includes: when it is detected that potential safety hazards exist in a three-level photovoltaic inverter, switching the pulse width modulation mode of the three-level photovoltaic inverter into a 13-vector space vector pulse width modulation mode, to solve the fault or abnormal problems in the three-level photovoltaic inverter such as midpoint potential offset or excessively large common mode leakage current formed when the ground stray capacitance of a photovoltaic assembly is large, wherein according to the 13-vector SVPWM mode, 12 short vectors in 27 on-off state vectors of the three-level photovoltaic inverter are abandoned, and only six long vectors, six middle vectors and three zero vectors are reserved.

Abstract: A grid-connected single-stage photovoltaic inverter is provided, which includes a direct current (DC) to alternating current (AC) inverter circuit, a DC to DC voltage booster circuit and a bypass element. An output of the DC to AC inverter circuit is connected to an alternating current grid, the DC to DC voltage booster circuit is connected in series between a photovoltaic array and the DC to AC inverter circuit, and the bypass element is connected in parallel with the DC to DC voltage booster circuit. A rated power capacity of the DC to DC voltage booster circuit is less than a rated power capacity of the DC to AC inverter circuit.

Abstract: A method for start control of photovoltaic inverter, a system thereof, and a photovoltaic power generation system are provided. A fan of the photovoltaic inverter is controlled to operate in a case that input voltage of the photovoltaic inverter is greater than a start threshold, and the fan operation is used as a load. Input voltage drop before and after the fan operates is obtained, and in a case that the input voltage drop is less than or equal to a voltage determination threshold, the photovoltaic inverter is controlled to start a grid connection. The voltage determination threshold is changed based on a power determination threshold of the photovoltaic inverter.

Abstract: A method and a device for generating PWM pulses for an inverter are provided. The three-phase inverter's characteristic of including high frequency complementary switches is used. Only three PWM peripheral units of a DSP control unit are used to output PWM high frequency signals, and a detection control unit determine for each phase two currently high frequency complementary switches according to the states of detected level signals outputted by a preset number of GPIO interfaces. The PWM high frequency signals are distributed for each phase to one of the two switches, and the PWM high frequency signals are inversed and then sent to the other one of the two switches. In addition, the states of other switches are maintained unchanged according to a preset correspondence between states of switches of a multi-level inverter and outputted level signals in different switching periods.

Abstract: A method and a device for generating PWM pulses for an inverter are provided. The three-phase inverter's characteristic of including high frequency complementary switches is used. Only three PWM peripheral units of a DSP control unit are used to output PWM high frequency signals, and a detection control unit determine for each phase two currently high frequency complementary switches according to the states of detected level signals outputted by a preset number of GPIO interfaces. The PWM high frequency signals are distributed for each phase to one of the two switches, and the PWM high frequency signals are inversed and then sent to the other one of the two switches. In addition, the states of other switches are maintained unchanged according to a preset correspondence between states of switches of a multi-level inverter and outputted level signals in different switching periods.

Abstract: A method for start control of photovoltaic inverter, a system thereof, and a photovoltaic power generation system are provided. A fan of the photovoltaic inverter is controlled to operate in a case that input voltage of the photovoltaic inverter is greater than a start threshold, and the fan operation is used as a load. Input voltage drop before and after the fan operates is obtained, and in a case that the input voltage drop is less than or equal to a voltage determination threshold, the photovoltaic inverter is controlled to start a grid connection. The voltage determination threshold is changed based on a power determination threshold of the photovoltaic inverter.