Improved power balance control method for cascaded photovoltaic grid-connected inverters

Abstract

The invention discloses an improved cascaded H-bridge photovoltaic grid-connected inverter power balance control method, which aims to solve the problem that the system cannot run stably due to the unbalanced input power of photovoltaic panels on the DC side. The method includes the following steps: (1) total DC side voltage control, which is used to realize the DC side voltage of each H-bridge unit to track its maximum power point voltage, and obtain the system active current command value; (2) grid side current decoupling control, It can realize the independent control of active current and reactive current, and generate the total modulation wave voltage of the inverter at the same time; (3) Modulation strategy switching control, different modulation strategy switching control is performed according to the working mode of the cascaded H-bridge photovoltaic grid-connected inverter . This method can not only realize the stable operation of the cascaded H-bridge photovoltaic inverter in the failure mode, that is, when one or more photovoltaic panels fail and is disconnected from the H-bridge unit, but also can reduce the voltage fluctuation of the DC side and improve the efficiency of the inverter. system power generation.

Description

technical field [0001] The invention relates to a power balance control method of a cascaded H-bridge photovoltaic grid-connected inverter, and belongs to the technical field of power balance control of a cascaded photovoltaic grid-connected inverter. Background technique [0002] Photovoltaic grid-connected power generation has attracted much attention because it provides clean energy and is environmentally friendly. Facing the problems of how to improve the efficiency of photovoltaic system and reduce the cost of power generation, the cascaded H-bridge multilevel inverter has become a popular choice due to its modularization, easy expansion, high system efficiency, and low total harmonic distortion (THD) of grid-connected current. research hotspot. In addition, each power unit of the cascaded H-bridge multi-level inverter needs an independent DC power supply, which is just in line with the characteristics of photovoltaic module power generation, making MPPT control of a s...

AI Technical Summary

Problems solved by technology

[0008] (1) The existing technology can improve the power imbalance problem of the cascaded H-bridge photovoltaic inverter to a certain extent, but the adjustment range is small. When the system is seriously unbalanced, the system cannot operate stably

[0009] (2) The power balance of the cascaded H-bridge photovoltaic inverter in a large range can be achieved through the hybrid modulation strategy, but when the system is in the fault mode, one or more photovoltaic panels fail and are disconnected from the H-bridge unit. When turned on, the system cannot run stably

[0010] (3) The improved hybrid modulation strategy can realize the stable operation of the cascaded H-bridge photovoltaic inverter in the failure mode, that is, when one or more photovoltaic panels fail and are disconnected from the H-bridge unit, but it will cause DC side voltage Large fluctuations make the photovoltaic panels deviate from the maximum power point and reduce the power generation of photovoltaic panels

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