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Photovoltaic inverter control method under condition of asymmetrical voltage sag

A technology of voltage asymmetry and control method, which is used in photovoltaic power generation, electrical components, output power conversion devices, etc.

Active Publication Date: 2014-05-28
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 during asymmetrical voltage sags, which solves the asymmetrical voltage sags that often occur in actual power grids and meets the needs of actual projects

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Embodiment Construction

[0035] 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, 6, 7, 8, which are described in detail.

[0036] Step 1: Build a photovoltaic array model, such as figure 1 shown.

[0037] The 5-parameter photovoltaic cell model proposed by the US SEL Laboratory (Solar Energy Laboratory) is used to build the photovoltaic array model. The battery model uses the equivalent physical and mathematical model of a single diode of photovoltaic cells to evaluate the output performance of the photovoltaic array. like figure 2 As 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, which contains 5 parameters in total: Photogenerated current (I pv ), diode reverse saturation leakage current (Io), ideality factor (a), equival...

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Abstract

The invention discloses a photovoltaic inverter control method under the condition of asymmetrical voltage sag and belongs to the technical field of photovoltaic power generation control. The method comprises steps of building a photovoltaic array model according to a photovoltaic cell teaching model and engineering practical cell parameters, extracting positive and negative sequence components of network voltage, calculating a reference value of output current on the basis of a flexible active and reactive control (FARC) strategy and analyzing an inverter output?power fluctuation?rate and an output current?harmonic total distortion rate on the basis of the FARC strategy, and using a proportional?resonant (PR) controller in a static coordinate system to design a grid-connected current control structure. PSCAD / EMTDC software is used for building a corresponding simulation?model. Grid-connected control and good dynamic performances can be realized whether under the symmetrical voltage condition or the asymmetrical voltage condition. The method has the advantages that grid-connected current control on the photovoltaic inverter under the condition of asymmetrical voltage sag can be effectively realized, the output?power fluctuation?rate and the output current?total harmonic distortion rate are smaller than those when other control strategies are adopted, and an asymmetrical fault ride-through capability of a photovoltaic plant 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 when voltage asymmetry sags. Background technique [0002] At present, most of the photovoltaic inverter control strategies are based on the ideal grid voltage, and the control strategy under the condition of asymmetric voltage sag is rarely studied. In fact, asymmetric voltage sags occur from time to time, mainly due to lightning strikes, short-circuit faults, and large-capacity motor starts. 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 sequenc...

Claims

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Application Information

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IPC IPC(8): H02M7/5387H02J3/38
CPCY02B10/10Y02E10/56
Inventor 徐永海黄浩杨琳
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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