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Control strategy of LCL-type three-phase photovoltaic grid connected inverter


WANG Si-hua1,2, WANG Jin-qiang1,2,3

 

(1. School of Automation and Electrical Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China;2. Rail Transit Electrical Automation Engineering Laboratory of Gansu Province, Lanzhou 730070, China;
3.Baiyin Electric Power Supply Company, State Grid Gansu Electric Power Company, Baiyin 730900, China)

 

Abstract: The grid-connected inverter with LCL filter has the ability of easily attenuating high-frequency current harmonics. However, its suppression effect on the background harmonics in grid voltage is limited. A control strategy is presented, which is composed of an inner loop of capacitor current feedforward, an outer loop of grid-current feedforward and feedforward of grid voltage. The limitations and steps of parameters design for LCL filter are analyzed. Meanwhile, the capacitor current loop is employed to damp the resonant peak caused by the LCL filter and enhance the stability. The properties of different controllers are analyzed and compared, thereinto quasi-proportional-rasonant (PR) controller realizes the control with zero steady-state error of AC variables in static coordinates. In order to suppress the current distortion effected by the background harmonics in grid voltage, the feed-forward function is calculated for the grid-connected inverter with an LCL filter. After simplifying the block diagram, a full-feedforward control strategy for grid voltage is proposed. Theoretical analysis and Matlab/Simulink simulation results show that the proposed method has the advantages of high steady accuracy, fast dynamic response and strong robustness.

 

 

Key words: three-phase grid-connected inverter; LCL filter; active damping; quasi-proportional-resonant (PR) control; full-feedforward of grid voltages

 

CLD number: TM464   Document code: A

 

Article ID: 1674-8042(2019)03-0254-012   doi: 103969/jissn1674-8042201903009

 

References

 

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LCL型三相光伏并网逆变器控制策略研究

 

王思华1,2, 王金强1,2,3

 


(1. 兰州交通大学 自动化与电气工程学院, 甘肃 兰州 730070;2. 甘肃省轨道交通电气自动化工程实验室, 甘肃 兰州 730070;3. 国家电网甘肃省电力公司白银供电公司, 甘肃 白银 730900)

 

摘要:LCL型并网逆变器对高频谐波的衰减效果显著, 但对电网背景谐波的抑制能力有限。 所提控制策略由电容电流反馈内环、 并网电流反馈外环和电网电压前馈环组成。 分析了LCL滤波器参数设计的限制条件以及步骤, 同时采用电容电流来抑制LCL产生的谐振尖峰, 提高稳定性。 分析比较了不同控制器的特点, 其中准PR控制器在静止坐标系下就可以实现对交流量的无静差跟踪控制。 此外, 为有效抑制背景谐波的影响, 推导LCL型并网逆变器所需要前馈电网电压的函数, 并将其加入到原控制系统中, 经过适当变换, 提出一种电网电压全前馈控制策略。 理论分析和Matlab/Simulink仿真结果表明, 该方法具有稳态精度高、 动态性能好以及抗干扰能力强的优点。

 


关键词:三相并网逆变器; LCL滤波器; 有源阻尼; 准比例谐振控制; 电网电压全前馈

 

引用格式:WANG Si-hua, WANG Jin-qiang. Control strategy of LCL-type three-phase photovoltaic grid connected inverter. Journal of Measurement Science and Instrumentation, 2019, 10(3): 254-265. [doi: 103969/jissn1674-8042201903009]

 

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