Abstract: An IV curve scan method for a photovoltaic module and an optimizer are provided. The optimizer receives an IV curve scan signal and controls an output voltage of the photovoltaic module corresponding to the IV curve scan signal to change from an open-circuit voltage to a preset minimum voltage according to a preset rule, while photovoltaic module connected to another optimizer can still operate normally, so that the system can operate normally. Then the optimizer uploads IV curve data of the photovoltaic module corresponding to the IV curve scan signal, to complete an IV curve scan on a single photovoltaic module.

Abstract: A DC-DC converter with a high transformer ratio includes two DC-DC converter bodies with inputs connected in parallel and outputs connected in series so as to ensure the high safe reliability and the high energy conversion efficiency of the DC-DC converter, while increase the boost ratio of the DC-DC converter.

Abstract: An IV curve scan method for a photovoltaic module and an optimizer are provided. The optimizer receives an IV curve scan signal and controls an output voltage of the photovoltaic module corresponding to the IV curve scan signal to change from an open-circuit voltage to a preset minimum voltage according to a preset rule, while photovoltaic module connected to another optimizer can still operate normally, so that the system can operate normally. Then the optimizer uploads IV curve data of the photovoltaic module corresponding to the IV curve scan signal, to complete an IV curve scan on a single photovoltaic module.

Abstract: A cascaded multilevel converter self-test system and a self-test method for the cascaded multilevel converter self-test system are provided. The self-test system includes a cascaded multilevel converter and a self-test device. The cascaded multilevel converter includes at least two converting circuits which are cascaded. The self-test device includes at least one current detecting circuit, a voltage acquiring module and a calculating module. The current detecting circuit is configured to detect a first detected current and a second detected current. The voltage acquiring module is configured to acquire first bus voltages and second bus voltages. The calculating module is configured to calculate an insulation resistance value of the cascaded multilevel converter based on the first detected current, the second detected current, the first bus voltages and the second bus voltages.

Abstract: A DC-DC converter with a high transformer ratio includes two DC-DC converter bodies with inputs connected in parallel and outputs connected in series so as to ensure the high safe reliability and the high energy conversion efficiency of the DC-DC converter, while increase the boost ratio of the DC-DC converter.

Abstract: A five level inverter comprises six switch tubes, two inductors, four capacitor units and two reverse current preventing devices. The common terminal of the third capacitor unit and the fourth capacitor unit is connected with the common terminal of the first capacitor unit and the second capacitor unit. The third capacitor unit and the fourth capacitor unit are used as the output filter circuit of the inverter, and the common terminal of the third capacitor unit and the fourth capacitor unit is used as the midpoint of the DC bus.

Abstract: A cascaded multilevel converter self-test system and a self-test method for the cascaded multilevel converter self-test system are provided. The self-test system includes a cascaded multilevel converter and a self-test device. The cascaded multilevel converter includes at least two converting circuits which are cascaded. The self-test device includes at least one current detecting circuit, a voltage acquiring module and a calculating module. The current detecting circuit is configured to detect a first detected current and a second detected current. The voltage acquiring module is configured to acquire first bus voltages and second bus voltages. The calculating module is configured to calculate an insulation resistance value of the cascaded multilevel converter based on the first detected current, the second detected current, the first bus voltages and the second bus voltages.

Abstract: A five level inverter comprises six switch tubes, two inductors, four capacitor units and two reverse current preventing devices. The common terminal of the third capacitor unit and the fourth capacitor unit is connected with the common terminal of the first capacitor unit and the second capacitor unit. The third capacitor unit and the fourth capacitor unit are used as the output filter circuit of the inverter, and the common terminal of the third capacitor unit and the fourth capacitor unit is used as the midpoint of the DC bus.