A control method for improving the grid-connected current quality of Lcl-type grid-connected inverters in weak grids

A control method and current quality technology, applied in circuit devices, AC network circuits, single-grid parallel feeding arrangements, etc., can solve the problems of complexity, affecting the quality of grid-connected current and power, lack of simple and feasible methods, etc., to eliminate mutual Influence, achieve adaptability, eliminate the effect of parameter perturbation

Active Publication Date: 2022-03-08
STATE GRID CHONGQING ELECTRIC POWER CO ELECTRIC POWER RES INST +2
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Problems solved by technology

However, this control scheme is relatively complicated, and the control parameters of each resonant (or quasi-resonant) controller need to be adjusted separately. During the measurement process, inter-harmonics need to be injected into the grid, which may affect the power quality of the grid-connected current, and when multiple inverters are connected in parallel Unclear physical meaning of grid impedance measurements at runtime
Therefore, the LCL type grid-connected inverter still lacks a simple and feasible method under the weak grid

Method used

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  • A control method for improving the grid-connected current quality of Lcl-type grid-connected inverters in weak grids
  • A control method for improving the grid-connected current quality of Lcl-type grid-connected inverters in weak grids
  • A control method for improving the grid-connected current quality of Lcl-type grid-connected inverters in weak grids

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Embodiment Construction

[0055] The present invention will be further described below in conjunction with drawings and embodiments.

[0056] Examples such as Figure 1 to Figure 4 Shown; A control method for improving the grid-connected current quality of the LCL type grid-connected inverter under the weak grid, which includes:

[0057] S1: Select LCL type grid-connected inverter side current i L , Grid-connected current i s and capacitor voltage u c For the state variables of the system, establish the mathematical model of the LCL type grid-connected inverter system;

[0058] Such as figure 2 As shown in the circuit topology of , the process of establishing the mathematical model in step S1 is as follows:

[0059]

[0060] where x 1 = i L -i Lref , x 2 = i s -i sref , x 3 = u c -u cref is the state variable of the system.

[0061] S2: In the model, the influence of the grid impedance is represented by the PCC voltage by using the relationship between the voltage of the common conne...

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Abstract

The invention discloses a control method for improving the grid-connected current quality of an LCL-type grid-connected inverter under a weak power grid, which includes: establishing a mathematical model of the LCL-type grid-connected inverter system; The relationship between voltage and grid impedance, the influence of grid impedance is represented by PCC voltage; according to the given grid-connected current i s The reference value and LCL type grid-connected inverter side current i L The reference value, using the indirect method to calculate the capacitor voltage u c The reference value u cref , and then using the capacitor voltage u c and common connection point PCC point voltage u pcc The relational expression calculates u pccref ; Solve the optimal H∞ control law parameters; use the obtained reference value and control law parameters to calculate the value of the duty cycle and obtain the value of the control quantity. The invention can keep the output current of the grid-connected inverter stable and suppress the resonance of the LCL filter and ensure the optimal quality of the grid-connected current when the impedance of the grid varies in a large range.

Description

technical field [0001] The invention relates to the technical field of grid-connected inverters, in particular to a control method for improving the grid-connected current quality of an LCL type grid-connected inverter under a weak grid. Background technique [0002] There are two types of existing grid-connected inverter current control methods suitable for weak grids. One type combines voltage feedforward control methods with multi-resonance (or quasi-resonance) control methods, adding special filtering to the voltage feedforward channel Devices such as resonant filters, band-pass filters, etc., can improve the phase margin of the system to a certain extent. However, this type of method cannot completely eliminate the influence of the grid-connected current positive feedback channel introduced by voltage feedforward. When the grid impedance is large, the quality of the grid-connected current is poor, and may even lose stability. Another type of scheme uses the online det...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/38
CPCH02J3/38H02J2203/20
Inventor 马兴徐瑞林陈涛朱小军付昂董光德杨爽廖铮陈民铀朱晟毅蒋望肖强赵小娟方辉王瑞妙向红吉
Owner STATE GRID CHONGQING ELECTRIC POWER CO ELECTRIC POWER RES INST
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