Power balancing control method of cascaded photovoltaic grid-connected inverter

Abstract

The invention brings forward a power balancing control method of cascaded photovoltaic grid-connected inverter on the partial shadow condition. The method comprises the following steps: (1), carrying out independent maximum power point tracking (MPPT) controlling on H bridges of all cascade units to obtain all-stage direct-current voltage instruction values and then carrying out PI controlling on a general direct-current voltage to obtain a grid-connected current instruction value; (2), carrying out quasi-proportional resonant (PR) control of the grid-connected current and grid voltage feedforward control so as to obtain initial duty ratio values of the H bridges; (3) carrying out per-unit processing on actual values of the direct-current side voltages of the cascade units according to the respective direct-current side voltage instruction values of all the cascade units, carrying out comparison with 1 and carrying out PI controlling so as to obtain active correction values of the duty ratios of the H bridges, and realizing power balancing control based on the duty ratio correction. According to the control method, floating control of the grid-connected current can be realized; and power balancing of all power units of the cascade inverter can be maintained. The provided control method has advantages of clear conception, simple control structure, and easy engineering realization and the like.

Description

technical field [0001] The invention relates to a power balance control method of a cascaded photovoltaic grid-connected inverter under partial shadow conditions, and belongs to the technical field of power balance control of cascaded inverters. Background technique [0002] Photovoltaic grid-connected power generation makes large-scale utilization of solar energy possible. Facing the high cost of power generation, improving system efficiency has always been a research hotspot. In the cascaded photovoltaic grid-connected inverter, due to the small number of series photovoltaic modules in the photovoltaic array of each level of power unit, when each level of power unit is controlled by independent MPPT (Maximum Power Point Tracking), local shadowing and Under the condition of mismatch between photovoltaic arrays, the output power of the system can be maximized. [0003] However, when there is a mismatch between partial shading and photovoltaic arrays, the use of independent ...

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Problems solved by technology

[0005] Purpose of the invention: The purpose of the present invention is to propose a power balance control method for cascaded photovoltaic grid-connected inverters under partial shading conditions, to solve the problem of inconsistency between the cascaded photovoltaic grid-connected inverters and the photovoltaic array. The power balance problem of the device under matching conditions ensures the stable operation of the inverter

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