Power balancing control method of cascaded photovoltaic grid-connected inverter

A technology of power balance and inverter, which is applied in the direction of single-network parallel feeding arrangement, etc., to achieve the effect of simple control structure, clear concept, and stable operation

Inactive Publication Date: 2014-05-14
SOUTHEAST UNIV
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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 probl

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  • Power balancing control method of cascaded photovoltaic grid-connected inverter
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  • Power balancing control method of cascaded photovoltaic grid-connected inverter

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[0025] The specific embodiments of the present invention will be described below with reference to the accompanying drawings.

[0026] The cascaded photovoltaic grid-connected inverter of the present invention adopts the voltage and current double closed-loop control to obtain the initial command value of the H-bridge duty cycle of each cascade unit, and each power unit obtains its own duty cycle by correcting the active component of the duty cycle. The air ratio is controlled separately to achieve power balance. Among them, the voltage and current double closed loop refers to the total DC voltage control (outer loop) and the quasi-proportional resonance control of the grid-connected current.

[0027] The overall DC voltage control has the following steps:

[0028] (1) Perform independent MPPT control on the H bridge of each cascade unit to obtain the command value of the DC voltage at each level and sum up to get Collect the DC side voltage of each unit, and pass through...

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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 ...

Claims

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Application Information

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IPC IPC(8): H02J3/38
Inventor 王书征赵剑锋姚晓君
Owner SOUTHEAST UNIV
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