LCL grid-connected inverter indirect current control method based on instruction current compensation

Abstract

The invention discloses an LCL grid-connected inverter indirect current control method based on instruction current compensation, and belongs to the technical field of grid-connected inverter control.According to the control method, direct-current voltage outer loop and grid-connected current inner loop double-closed-loop control is adopted, on the basis of conventional inverter side inductive current feedback and filter capacitor current active damping indirect current control, the instruction current compensation amount is increased, and the purpose of high-precision control over the amplitude and phase of output grid-connected current is achieved; besides, an improved discrete differential operator is adopted to obtain filter capacitor current and grid-connected current feedback quantity so as to compensate calculation delay of state feedback quantity discretization, stability of the system is improved, and meanwhile the purpose of reducing cost of the sensor is achieved. The method is suitable for a new energy grid-connected power generation system, and is a simple and effective implementation mode.

Description

technical field [0001] The invention belongs to the technical field of grid-connected inverter control, and in particular relates to an indirect current control method of an LCL grid-connected inverter based on command current compensation. Background technique [0002] In order to cope with the increasingly severe energy problems, the rational development and utilization of renewable energy has become an important means for countries in the world to pursue sustainable development. Grid-connected inverter is the core of the conversion device between distributed generation of renewable energy and the grid, and its stable and efficient operation is of great significance to the entire distributed generation system. In the grid-connected inverter, the LCL output filter with small size and strong ability to suppress the high-order harmonics of the output grid-connected current is often used, but its third-order characteristics make the system operation difficult to stabilize, so ...

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Problems solved by technology

However, the filtering effect of the filter capacitor and the grid-side inductance on the high-frequency current component makes the grid-connected current and the inverter-side inductor current very different, which ultimately results in poor tracking effect of the controlled output steady-state grid-connected current on the expected value. There are large deviations in both the amplitude and the

[0004] Chinese patent CN104600705 proposes an idea of ​​"increasing the feedback regulation of the LCL filter capacitor current on the basis of the traditional single inverter side current feedback control". This idea can effectively suppress the resonance problem of the LCL, but it cannot eliminate the problem of the output grid-connected current. Steady-state phase and amplitude error; Chinese patent CN101741101 and the article titled "LCL Filter Grid-connected Inverter Parameter Design for Inverter-side Current Feedback" propose a phase correction method for incoming grid current: by detecting grid voltage and the phase difference of the grid-connected current, the comparison error between it and 0 is superimposed on the original reference phase after the droop control to eliminate the phase error. The disadvantage of this method is that the amplitude error problem is artificially made The amplitude of the command current can be solved. In addition, detecting the phase difference between the two in engineering will increase the system cost, which is not feasible and will complicate the controller design.

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