Grid-connected method of three-phase voltage source type grid-connected inverter without surge current
A three-phase inverter and three-phase voltage technology, which is applied in the field of electric power generation, transformation or distribution, can solve problems such as large numerical value, impact of power devices and other components, and inability to track the output voltage of the inverter.
Inactive Publication Date: 2016-05-04
TIANJIN UNIV
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Problems solved by technology
Since there is no output current before the inverter is connected to the grid, the initial sampling current is zero when the grid is connected, and the output voltage of the inverter cannot track the voltage on the grid side, so there will be a large inrush current when it is connected to the grid
Generally speaking, the value of this inrush current is relatively large, and may even be several times the rated current, which will have a serious impact on power devices and other components
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[0041] The present invention will be described below in conjunction with the accompanying drawings and embodiments. This grid connection method is aimed at using the output current as the inner loop control of the three-phase voltage source inverter, and solves the problem of inrush current generated at the moment of grid connection. Aiming at the problem that inverters of this type of control cannot obtain relevant currents before grid-connection, resulting in control failure during grid-connection, the present invention realizes non-impact grid-connection control of this type of inverter by switching control strategies . Primary loop topology and control system structure such as figure 1 shown.
[0042] Usually, depending on the filter used by the inverter, the current inner loop control strategy is also different. In this method, the proportional resonance control method for the LCL filter is used to illustrate the grid-connected control process, but its basic principle i...
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The invention relates to a non-impact-current grid connection method for three-phase voltage source grid-connected inverters. The non-impact-current grid connection method includes acquiring various phases of voltages and currents on two sides of each grid-connected point in real time and computing D-axis voltage components and Q-axis voltage components of inverter sides; computing D-axis voltage components and Q-axis voltage components of grid sides; controlling the D-axis voltage components and the Q-axis voltage components, regulating duty cycles of driving signals of three-phase half-bridge circuits by the aid of inner current rings and outer control rings which are the D-axis voltage components and the Q-axis voltage components, and driving main circuits to output alternating currents in an inverter manner; operating the three-phase voltage source grid-connected inverters according to the steps before the three-phase voltage source grid-connected inverters are connected with grids, and gradually regulating the three-phase voltage source grid-connected inverters after grid-connected circuit breakers are assuredly reliably closed so that the three-phase voltage source grid-connected inverters can be in steady constant-power output states. The non-impact-current grid connection method has the advantages that impact currents can be effectively suppressed in voltage source inverter grid connection procedures, grid-connected output currents of the three-phase voltage source grid-connected inverters can be gradually increased until the grid-connected output currents reach steady values, and non-impact-current grid connection effects can be realized.
Description
technical field [0001] The invention belongs to the technical field of electric power generation, transformation or distribution. It is a grid-connected method that can effectively suppress the grid-connected surge current of the grid-connected inverter. Background technique [0002] In recent years, distributed power generation represented by photovoltaic and wind power generation has been increasingly connected to the power grid as a supplement to traditional power sources. Unlike traditional synchronous machines that can directly supply power-frequency AC power, distributed power sources usually cannot directly generate power-frequency AC power, so most of them realize grid connection and storage through rectification or inverter devices, while inverters are DC-type distributed power sources connected to the grid the most important interface. [0003] Inverter is a device that converts direct current into alternating current, and from the type of direct current source, ...
Claims
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IPC IPC(8): H02J3/38
Inventor 李永丽靳伟张玮亚孙广宇李小叶
Owner TIANJIN UNIV