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Method for controlling photovoltaic inverter under conditions of unbalanced network voltage

A photovoltaic inverter, grid voltage technology, applied in photovoltaic power generation, reactive power compensation, reactive power adjustment/elimination/compensation and other directions

Active Publication Date: 2014-07-30
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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Problems solved by technology

[0003] The purpose of the present invention is to provide a control method for photovoltaic inverters when the grid voltage is unbalanced, to solve the problem of grid connection of photovoltaic inverters in the case of unbalanced voltage, and to meet the needs of actual projects

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  • Method for controlling photovoltaic inverter under conditions of unbalanced network voltage
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  • Method for controlling photovoltaic inverter under conditions of unbalanced network voltage

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[0050] In order to make the purpose, technical scheme and advantages of the present invention clearer, the following will be combined with the attached figure 1 , 2 , 3, 4, 5, describe it in detail.

[0051] Step 1: Design of the photovoltaic system.

[0052] Photovoltaic grid-connected systems usually consist of photovoltaic arrays, photovoltaic inverters, filters and main grids, such as figure 1 shown. In the present invention, the photovoltaic array uses the 5-parameter photovoltaic cell model proposed by the U.S. SEL Laboratory (Solar Energy Laboratory) to build the photovoltaic array model. . Such as figure 2As shown, the equivalent circuit of the battery model is a current source connected in parallel with a reverse diode and an equivalent parallel resistance, and then an equivalent series resistance in series, including 5 parameters in total: photogenerated current (I pv ), diode reverse saturation leakage current (I o ), ideality factor (a), equivalent parallel...

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Abstract

The invention discloses a method for controlling a photovoltaic inverter under conditions of unbalanced network voltage and belongs to the technical field of photovoltaic power generation. The method comprises the steps of designing a photovoltaic system; putting forward an output current reference value algorithm of the photovoltaic inverter when the network voltage is unbalanced based on the instantaneous power theory; analyzing output power of the photovoltaic inverter adopting the current reference value algorithm; designing a current control structure of the photovoltaic inverter when the network voltage is unbalanced. Whether under conditions of unbalanced network voltage or under conditions of balanced network voltage, grid-connected control of the photovoltaic inverter and good dynamic performance can be achieved well by means of the control strategies in the method. The method has the advantages that grid-connected current control of the photovoltaic inverter when the network voltage is unbalanced can be achieved effectively, the output current of the photovoltaic inverter does not contain harmonic waves, fluctuation of output active or reactive power is small, the output active or reactive power can be regulated flexibly, and unsymmetrical fault ride-through capability of a photovoltaic power station can be improved.

Description

technical field [0001] The invention belongs to the technical field of photovoltaic power generation control, and in particular provides a method for controlling a photovoltaic inverter under the condition of unbalanced grid voltage. Background technique [0002] At present, most of the photovoltaic inverter control strategies are based on the ideal grid voltage. In fact, unbalanced grid voltage always exists, especially factors such as lightning strikes, short-circuit faults, and large-capacity motor start-ups cause grid voltage asymmetry. In this case, due to the existence of the negative sequence component in the grid voltage, both the grid voltage and the grid-connected current have double frequency fluctuations in the synchronous rotating coordinate system. At this time, if the photovoltaic inverter still adopts the control strategy when the grid voltage is symmetrical , it will not be able to effectively control the negative sequence component of the current, which wi...

Claims

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Application Information

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IPC IPC(8): H02J3/18
CPCY02E10/56Y02E40/30
Inventor 徐永海黄浩李科
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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