基于“虚拟负阻抗”的微网逆变器并联运行研究
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摘要
在低压微网孤岛运行模式下,传统下垂控制受线路阻抗特性的影响难以实现良好的均流效果。在控制环路增加虚拟阻抗可以抑制系统环流,但传统虚拟阻抗会增大逆变器的输出阻抗,导致输出产生电压降落,且由于系统阻抗阻性部分的影响难以将系统矫正为纯感性。为解决上述问题,提出"虚拟负阻抗"的控制策略,采用虚拟负电阻来抵消系统阻抗中的阻性部分,使逆变器保持较低的输出阻抗,减小系统输出电压的降落,再结合虚拟电感使其更趋近纯感性,改善环流抑制效果。在Matlab/Simulink中搭建了双逆变器并联运行模型,仿真结果验证了所提控制策略的可行性和优越性。
In the isolated running mode of low-voltage micro-grid,the conventional droop control is difficult to achieve a good consequent current sharing due to the influence of line impedance. Virtual impedance is usually added in the controller to alleviate the circulating current,but the conventional virtual impedance usually increases the inverter output impedance and then causes a certain voltage drop,due to the system resistive,it is difficult to correct the system impedance to pure sensibility. In order to solve this problem,a new virtual negative impedance method is proposed,which takes a virtual negative resistance to offset the resistive part of the system impedance,which can keep the inverter at a lower output impedance to reduce the system output voltage drop,then,correcting the system impedance to be a pure inductance with the virtual inductance,which can improve the consequent of circulation inhibition. Simulations of two parallel inverters are carried out on MATLAB/Simulink,and the simulation results verify the superiority and feasibility of the proposed control strategy.
In the isolated running mode of low-voltage micro-grid,the conventional droop control is difficult to achieve a good consequent current sharing due to the influence of line impedance. Virtual impedance is usually added in the controller to alleviate the circulating current,but the conventional virtual impedance usually increases the inverter output impedance and then causes a certain voltage drop,due to the system resistive,it is difficult to correct the system impedance to pure sensibility. In order to solve this problem,a new virtual negative impedance method is proposed,which takes a virtual negative resistance to offset the resistive part of the system impedance,which can keep the inverter at a lower output impedance to reduce the system output voltage drop,then,correcting the system impedance to be a pure inductance with the virtual inductance,which can improve the consequent of circulation inhibition. Simulations of two parallel inverters are carried out on MATLAB/Simulink,and the simulation results verify the superiority and feasibility of the proposed control strategy.
引文
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[11]李永东,谢永流,程志江,等.微电网系统母线和频率无静差控制策略研究[J].电机与控制学报,2016,20(7):49-57.Li Yongdong,Xie Yongliu,Cheng Zhijiang,et al. Research of nonsteady state error control strategy of bus voltage and frequency in microgrid system[J]. Elecric Machines and Control,2016,20(7):49-57.
[12]毛艳芳,熊旋,陈旭,等.单相逆变器双环控制改进策略研究[J].电测与仪表,2014,51(8):70-74.Mao Yanfang,Xiong Xuan,Chen Xu,et al. Research on Improved Dual-Loop Control Strategy for Single-Phase Inverter[J]. Electrical Measurement&Instrumentation,2014,51(8):70-74.
[2] Guo F,Wen C,Mao J,et al. Distributed secondary voltage and frequencyrestoration control of droop-controlled inverter-based microgrids[J].IEEE Transactions Industrial Electron,2015,62(7):4355-4364.
[3] Lasseter R H. Micro Grid[C]. Proc. Power Eng. Soc. Winter Meeting,2002:305-308.
[4]杨新法,苏剑,吕志鹏,等.微电网技术综述[J].中国电机工程学报,2014,34(1):57-70.Yang Xinfa,Su Jian,Lv Zhipeng,et al. Overview on micro-grid technology[J]. Proceedings of the CSEE,2014,34(1):57-70.
[5] Y Zhang and H Ma. Theoretical and experime-nttal investigation of networked control for parallel operation of inverters[J]. IEEE Transactions on Industrial Electronics,2012,59(4):1961-1970.
[6] Li Y,Vilathgamuwa D M,Loh P C. Design,analysis and real-time testing of a controller for multibus microgrid system[J]. IEEE Transaction on Power Electron,2004,19(5):1195-1204.
[7] De Brabandere K,Bolsens B,Van den Keyb-us J,et al. A voltage and frequency droop control method for parallel Inverters[J]. Transaction on Power Electron. 2007,22(4):1107-1115.
[8] J W He and Y W Li. Analysis,Design,and Implementation of Virtual Impedance for Power Electronics Interfaced Distributed Generation[J].IEEE Transactions On Industry Applications,2011,47(6):2525-2538.
[9] J W He and Y W Li. Generalized Closed-Loop Control Schemes with Embedded Virtual Impedances for Voltage Source Converters with LC or LCL Filters[J]. IEEE Transactions On Power Electronics,2012,27(4):1850-1861.
[10]张平,石健将,李荣贵,等.低压微网逆变器的“虚拟负阻抗”控制策略[J].中国电机工程学报,2014,34(12):1844-1852.Zhang Ping,Shi Jianjiang,Li Ronggui,et al. A Control Strategy of Virtual Negative Impedance for Inverters in Low-voltage Microgrid[J]. Proceedings of the CSEE,2014,34(12):1844-1852.
[11]李永东,谢永流,程志江,等.微电网系统母线和频率无静差控制策略研究[J].电机与控制学报,2016,20(7):49-57.Li Yongdong,Xie Yongliu,Cheng Zhijiang,et al. Research of nonsteady state error control strategy of bus voltage and frequency in microgrid system[J]. Elecric Machines and Control,2016,20(7):49-57.
[12]毛艳芳,熊旋,陈旭,等.单相逆变器双环控制改进策略研究[J].电测与仪表,2014,51(8):70-74.Mao Yanfang,Xiong Xuan,Chen Xu,et al. Research on Improved Dual-Loop Control Strategy for Single-Phase Inverter[J]. Electrical Measurement&Instrumentation,2014,51(8):70-74.