Abstract: The present disclosure provides a leakage current suppression method for a string photovoltaic system. The leakage current suppression method includes the following steps: S100, inputting synchronous carriers to a plurality of parallel inverters included in the photovoltaic system; S200, carrying out carrier modulation on the inverters; and S300, controlling the switching state of each inverter according to the result of carrier modulation, and then dislocating common-mode components output by each inverter, so that part of the common-mode components of each inverter are canceled out, and the potential variation of the common-mode components output by the photovoltaic system is reduced. The method has the beneficial effects that the leakage current suppression method in the present disclosure is pure in software optimization, low in cost and simple in implementation method.

Abstract: The present disclosure provides a PID (Potential Induced Degradation) effect suppression system. The PID effect suppression system includes a photovoltaic system, at least one voltage source topology module and a balanced circuit. The photovoltaic system is connected with a power grid. An output end of the voltage source topology module is connected with busbar neutral points of the photovoltaic system. A common earth end of the voltage source topology module is earthed, and then the potential to earth of a photovoltaic panel group in the photovoltaic system is improved through the suppression voltage output by the voltage source topology module, and the suppression voltage is greater than ½ of the output voltage of the photovoltaic panel group. Therefore, a PID effect of the photovoltaic system in operation can be effectively suppressed.

Abstract: The present disclosure discloses a T-shaped three-level overload operating system, including a three-level topology and an overload mode switching system. The topology is connected with a first device group and a second device group which form a T shape; the first device group is designed with an overload capacity, and the second device group is designed with a rated capacity; and the overload mode switching system is configured for being connected to the topology to control the first device group to perform overload two-level operation on the topology, or to control the second device group to perform normal three-level operation on the topology, so that the number of device groups of the overload design can be effectively reduced, and then the cost of the system can be reduced. A working method of the T-shaped three-level overload operating system is further disclosed. The topology can be rapidly switched among working modes according to an output current of the topology.