三相并网逆变器频率耦合机理分析及稳定性判定
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摘要
并网逆变器中控制器dq轴结构或参数的不对称会导致系统在静止坐标系下存在两个扰动频率分量相互耦合,这一耦合因素会影响系统的稳定性。文中分析了系统中这两个扰动频率的耦合机理,分别得到了两个耦合频率下的逆变器等效导纳。利用这两个导纳,采用奈奎斯特判据判定了并网逆变器系统的稳定性,相比现有采用广义奈奎斯特判据的方法,稳定性判定过程简单,便于给出系统稳定裕量,指导逆变器控制器设计。实验验证了并网逆变器系统稳定性判定结果的正确性。
The asymmetric dq-axis structure or parameters of the controller in the grid-connected inverter will cause the coupling between two disturbed frequency components of the system in the static frame.This coupling factor will affect the stability of the power system.This paper analyzes the mechanism of frequency coupling,and derives the equivalent admittance of inverter under the two coupling frequency components.By using the two equivalent admittances,the stability of the gridconnected inverter system can be judged by the Nyquist criterion.Compared with the approaches using the generalized Nyquist criterion,the stability judgement process of the proposed method is simpler.By using this method,it is convenient to obtain the phase margin or gain margin of the system and guide the controller design.Finally,the correctness of the stability judgement results is verified through experiments.
The asymmetric dq-axis structure or parameters of the controller in the grid-connected inverter will cause the coupling between two disturbed frequency components of the system in the static frame.This coupling factor will affect the stability of the power system.This paper analyzes the mechanism of frequency coupling,and derives the equivalent admittance of inverter under the two coupling frequency components.By using the two equivalent admittances,the stability of the gridconnected inverter system can be judged by the Nyquist criterion.Compared with the approaches using the generalized Nyquist criterion,the stability judgement process of the proposed method is simpler.By using this method,it is convenient to obtain the phase margin or gain margin of the system and guide the controller design.Finally,the correctness of the stability judgement results is verified through experiments.
引文
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[19]王国宁,杜雄,邹小明,等.用于三相并网逆变器稳定性分析的自导纳和伴随导纳建模[J].中国电机工程学报,2017,37(14):3973-3981.WANG Guoning,DU Xiong,ZOU Xiaoming,et al.Self and accompanying admittance model for three-phase grid-tied inverter stability analysis[J].Proceedings of the CSEE,2017,37(14):3973-3981.
[20]SUN Jian.Impedance-based stability criterion for gridconnected inverters[J].IEEE Transactions on Power Electronics,2011,26(11):3075-3078.
[2]赵强松,叶永强,徐国峰.分布式发电系统中并网逆变器的新型有源阻尼策略[J].电力系统自动化,2015,39(14):140-144.DOI:10.7500/AEPS20141208009.ZHAO Qiangsong,YE Yongqiang,XU Guofeng.A novel active damping control scheme for grid-connected inverter in distributed power generation systems[J].Automation of Electric Power Systems,2015,39(14):140-144.DOI:10.7500/AEPS20141208009.
[3]谢小荣,刘华坤,贺静波,等.新能源发电并网系统的小信号阻抗/导纳网络建模方法[J].电力系统自动化,2017,41(12):26-32.DOI:10.7500/AEPS20170125005.XIE Xiaorong,LIU Huakun,HE Jingbo,et al.Small-signal impedance/admittance network modeling for grid-connected renewable energy generation systems[J].Automation of Electric Power Systems,2017,41(12):26-32.DOI:10.7500/AEPS20170125005.
[4]GUO Xiaoqiang,LIU Shichao,WANG Xiaoyu.Impact of phase-locked loop on stability of active damped LCL-filter-based grid-connected inverters with capacitor voltage feedback[J].Journal of Modern Power Systems and Clean Energy,2017,5(4):574-583.
[5]MIDDLEBROOK D R.Input filter considerations in design and application of switching regulators[C]//IAS,1976:366-382.
[6]FENG X G,LIU J J,LEE F C.Impedance specifications for stable DC distributed power systems[J].IEEE Transactions on Power Electronics,2002,17(2):157-162.
[7]WU Mingfei,LU D D C.Active stabilization methods of electric power systems with constant power loads:a review[J].Journal of Modern Power Systems and Clean Energy,2014,2(3):233-243.
[8]SUN J.Small-signal methods for electric ship power systems[C]//IEEE Electric Ship Technologies Symposium(ESTS),April 20-22,2009,Baltimore,USA:44-52.
[9]BELKHAYAT M.Stability criteria for AC power systems with regulated loads[D].West Lafayette,USA:Purdue University,1997.
[10]SUN Jian,KARIMI K J.Small-signal input impedance modeling of line-frequency rectifiers[J].IEEE Transactions on Aerospace and Electronic Systems,2008,44(4):1489-1497.
[11]SUN Jian,BING Zhonghui,KARIMI K J.Input impedance modeling of multipulse rectifiers by harmonic linearization[J].IEEE Transactions on Power Electronics,2009,24(12):2812-2820.
[12]CAO Wenchao,MA Yiwei,WANG F.Harmonic stability analysis and controller parameter design of three-phase inverter-based multi-bus AC systems based on sequence impedances[C]//IEEE Energy Conversion Congress and Exposition(ECCE),September 18-22,2016,Milwaukee,USA:8p.
[13]CESPEDES M,SUN J.Impedance modeling and analysis of grid-connected voltage-source converters[J].IEEE Transactions on Power Electronics,2014,29(3):1254-1261.
[14]BAKHSHIZADEH M K,WANG Xiongfei,BLAABJERG F A,et al.Couplings in phase domain impedance modeling of grid-connected converters[J].IEEE Transactions on Power Electronics,2016,31(10):6792-6796.
[15]HARNEFORS L,BONGIORNO M,LUNDBERG S.Inputadmittance calculation and shaping for controlled voltage-source converters[J].IEEE Transactions on Industrial Electronics,2007,54(6):3323-3334.
[16]WEN Bo,BOROYEVICH D,BURGOS R,et al.Analysis of D-Q small-signal impedance of grid-tied inverters[J].IEEE Transactions on Power Electronics,2016,31(1):675-687.
[17]辛焕海,李子恒,董炜,等.三相变流器并网系统的广义阻抗及稳定判据[J].中国电机工程学报,2017,37(5):1277-1292.XIN Huanhai,LI Ziheng,DONG Wei,et al.Generalizedimpedance and stability criterion for grid-connected converters[J].Proceedings of the CSEE,2017,37(5):1277-1292.
[18]RYGG A,MOLINAS M,ZHANG Chen,et al.A modified sequence-domain impedance definition and its equivalence to the dq-domain impedance definition for the stability analysis of AC power electronic systems[J].IEEE Journal of Emerging and Selected Topics in Power Electronics,2016,4(4):1383-1396.
[19]王国宁,杜雄,邹小明,等.用于三相并网逆变器稳定性分析的自导纳和伴随导纳建模[J].中国电机工程学报,2017,37(14):3973-3981.WANG Guoning,DU Xiong,ZOU Xiaoming,et al.Self and accompanying admittance model for three-phase grid-tied inverter stability analysis[J].Proceedings of the CSEE,2017,37(14):3973-3981.
[20]SUN Jian.Impedance-based stability criterion for gridconnected inverters[J].IEEE Transactions on Power Electronics,2011,26(11):3075-3078.