交直流微电网中变换器级联系统稳定性分析与协同控制
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摘要
交直流微电网将成为未来配用电系统的重要组成形式,受到广泛的关注。但其中的恒功率负载具有负阻抗特性,容易引发母线电压振荡,不利于系统稳定运行。该文以控制母线电压的源变换器双向DC/DC和控制功率的负载变换器双向DC/AC为研究对象,建立直流变换器级联系统的等效阻抗模型,并进行稳定性分析。研究表明,LC滤波器会增大系统低频段输出阻抗,造成直流母线电压出现输出阻抗峰值频率附近的振荡。对此,该文提出一种协同控制方法,引入电压和功率协同控制,同时调整源变换器的输出阻抗和负载变换器的输入阻抗,从而减少级联系统输出阻抗的幅值并增加输入阻抗的相位,扩大系统的稳定裕度。最后,通过仿真和实验验证该文的分析和所提控制方法的有效性。
Hybrid AC/DC microgrid will be an important form of future power distribution system, and it has been grasping more and more attention. However, because of the constant power load(CPL), the DC bus is prone to oscillation and even instability. This paper selected bidirectional DC/DC converter and bidirectional DC/AC converter as research object, deduced their DC equivalent impedance, then built converters DC cascade system impedance model, and studied the stability of cascade system by the stability criterion.Researches show that, LC filter would increase the output impedance of cascade system in low-frequency stage, and the DC voltage is likely to oscillate around the peak frequency of output impedance. So, this paper proposed a coordinative virtual impedance control for improving system stability and capability of transmission power. The proposed method regulates the output impedance of source converter and the input impedance of load converter, and it can decrease the magnitude of output impedance and increase the phase of input impedance at the same time. Finally, simulation and experiment results validate the proposed control strategy and analysis.
Hybrid AC/DC microgrid will be an important form of future power distribution system, and it has been grasping more and more attention. However, because of the constant power load(CPL), the DC bus is prone to oscillation and even instability. This paper selected bidirectional DC/DC converter and bidirectional DC/AC converter as research object, deduced their DC equivalent impedance, then built converters DC cascade system impedance model, and studied the stability of cascade system by the stability criterion.Researches show that, LC filter would increase the output impedance of cascade system in low-frequency stage, and the DC voltage is likely to oscillate around the peak frequency of output impedance. So, this paper proposed a coordinative virtual impedance control for improving system stability and capability of transmission power. The proposed method regulates the output impedance of source converter and the input impedance of load converter, and it can decrease the magnitude of output impedance and increase the phase of input impedance at the same time. Finally, simulation and experiment results validate the proposed control strategy and analysis.
引文
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[10]张学,裴玮,邓卫,等.含恒功率负载的交直流混联配电系统稳定性分析[J].中国电机工程学报,2017,37(19):5572-5582.Zhang Xue,Pei Wei,Deng Wei,et al.Stability analysis of AC/DC hybrid distribution system with constant power loads[J].Proceedings of the CSEE,2017,37(19):5572-5582(in Chinese).
[11]Gu Y,Xiang X,Li W,et al.Mode-adaptive decentralized control for renewable DC microgrid with enhanced reliability and flexibility[J].IEEE Transactions on Power Electronics,2014,29(9):5072-5080.
[12]Wu M F,Lu D.A novel stabilization method of LC input filter with constant power loads without load performance compromise in DC microgrids[J].IEEE Transactions on Industrial Electronics,2015,62(7):4552-4562.
[13]王成山,李微,王议锋,等.直流微电网母线电压波动分类及抑制方法综述[J].中国电机工程学报,2017,37(1):84-97.Wang Chengshan,Li Wei,Wang Yifeng,et al.DC bus voltage fluctuation classification and restraint methods review for DC microgrid[J].Proceedings of the CSEE,2017,37(1):84-97(in Chinese).
[14]Amin M,Molinas M,Jing L,et al.Impact of power flow direction on the stability of VSC-HVDC seen from the impedances Nyquist plot[J].IEEE Transactions on Power Electronics,2017,32(10):8204-8217.
[15]Middlebrook R D.Input filter considerations in design and application of switching regulators[C]//IEEE Ind.Applicat.Soc.Annu.Metting.Chicago,lllionios,1976:366-382.
[16]Feng X,Liu J,Lee F C.Impedance specifications for stable DC distributed power systems[J].IEEETransactions on Power Electronics,2002,17(2):157-162.
[17]Rashidirad N,Hamzeh M,Sheshyekani K,et al.Asimplified equivalent model for the analysis of low-frequency stability of multi-bus DC Microgrids[J].IEEE Transactions on Smart Grid,May,2017(99):1-1.
[18]Zhang X,Ruan X,Chi K T.Impedance-based local stability criterion for DC distributed power systems[J].IEEE Transactions on Circuits&Systems I Regular Papers,2015,62(3):916-925.
[19]伍文华,陈燕东,罗安,等.海岛VSC-HVDC输电系统直流阻抗建模、振荡分析与抑制方法[J].中国电机工程学报,2018,38(15):4359-4368.Wu Wenhua,Chen Yandong,Luo An,et al.DC impedance modeling,oscillation analysis and suppression method for VSC-HVDC system in the field of islands power supply[J].Proceedings of the CSEE,2018,38(15):4359-4368(in Chinese).
[20]伍文华,陈燕东,罗安,等.一种直流微网双向并网变换器虚拟惯性控制策略[J].中国电机工程学报,2017,37(2):360-371.Wu Wenhua,Chen Yandong,Luo An,et al.A virtual inertia control strategy for bidirectional grid-connected converters in DC micro-grids[J].Proceedings of the CSEE,2017,37(2):360-371(in Chinese).
[21]李云丰,汤广福,吴亚楠,等.直流电网建模分析与阻尼控制研究[J].中国电机工程学报,2017,37(12):3372-3382.Li Yunfeng,Tang Guangfu,Wu Yanan,et al.Modeling,analysis and damping control of DC grid[J].Proceedings of the CSEE,2017,37(12):3372-3382(in Chinese).
[22]Lu X,Sun K,Guerrero J M,et al.Stability enhancement based on virtual impedance for DC microgrids with constant power loads[J].IEEE Transactions on Smart Grid,2015,6(6):2770-2783.
[23]Zhang X,Zhong Q C,Ming W L.A virtual RLC damper to stabilize DC/DC converters having an LC input filter while improving the filter performance[J].IEEETransactions on Power Electronics,2016,31(12):8017-8023.
[24]Gao F,Bozhko S,Costabeber A,et al.Comparative stability analysis of droop control approaches in voltage-source-converter-based DC microgrids[J].IEEETransactions on Power Electronics,2016,32(3):2395-2415.
[25]郭力,冯怿彬,李霞林,等.直流微电网稳定性分析及阻尼控制方法研究[J].中国电机工程学报,2016,36(4):927-936.Guo Li,Feng Yibin,Li Xialin,et al.Stability analysis and research of active damping method for DC microgrids[J].Proceedings of the CSEE,2016,36(4):927-936(in Chinese).
[26]支娜,张辉,肖曦.提高直流微电网动态特性的改进下垂控制策略研究[J].电工技术学报,2016,31(3):31-39.Zhi Na,Zhang Hui,Xiao Xi.Research on the improved droop control strategy for improving the dynamic characteristics of DC microgrid[J].Transactions of China Electrotechnical Society,2016,31(3):31-39(in Chinese).
[27]Carne G D,Buticchi G,Zou Z X,et al.Reverse power flow control in a ST-fed distribution grid[J].IEEETransactions on Smart Grid,January,2017(99):1-1.
[28]季一润,袁志昌,赵剑锋,等.一种适用于柔性直流配电网的电压控制策略[J].中国电机工程学报,2016,36(2):335-341.Ji Yirun,Yuan Zhichang,Zhao Jianfeng,et al.A suitable voltage control strategy for DC distribution power network[J].Proceedings of the CSEE,2016,36(2):335-341(in Chinese).
[29]Tian Y,Loh P C,Deng F,et al.DC-Link voltage coordinated-proportional control for cascaded converter with zero steady-state error and reduced system type[J].IEEE Transactions on Power Electronics,2016,31(4):3177-3188.
[30]Tian Y,Chen Z,Deng F,et al.Active power and DCvoltage coordinative control for cascaded DC-ACconverter with bidirectional power application[J].IEEETransactions on Power Electronics,2015,30(10):5911-5925.
[2]Loh P C,Li D,Chai Y K,et al.Autonomous control of interlinking converter with energy storage in hybrid AC-DC microgrid[J].IEEE Transactions on Industry Applications,2013,49(3):1374-1382.
[3]Liu X,Wang P,Loh P C.A hybrid AC/DC microgrid and its coordination control[J].IEEE Transactions on Smart Grid,2011,2(2):278-286.
[4]李霞林,郭力,王成山,等.直流微电网关键技术研究综述[J].中国电机工程学报,2016,36(1):2-16.Li Xialin,Guo Li,Wang Chengshan,et al.Key technologies of DC microgrids:an overview[J].Proceedings of the CSEE,2016,36(1):2-16(in Chinese).
[5]Tomislav D,Lu X,Vasquez J C,et al.DC microgrids(part I):a review of control strategies and stabilization techniques[J].IEEE Transactions on Power Electronics,2016,31(7):4876-4891.
[6]周小平,陈燕东,周乐明,等.一种微网群架构及其自主协调控制策略[J].电工技术学报,2017,32(10):123-134.Zhou Xiaoping,Chen Yandong,Zhou Leming,et al.Amicrogrid cluster structure and its autonomous coordination control strategy[J].Transactions of China Electrotechnical Society,2017,32(10):123-134(in Chinese).
[7]许阔,王婉君,贾利虎,等.混合微电网交流不对称故障对直流系统的影响[J].中国电机工程学报,2018,38(15):4429-4437.Xu Kuo,Wang Wanjun,Jia Lihu,et al.Influence of ACunbalanced fault on DC side of hybrid AC/DCmicrogrid[J].Proceedings of the CSEE,2018,38(15):4429-4437(in Chinese).
[8]Xia Y,Wei W,Yu M,et al.Decentralized multi-time scale power control for a hybrid AC/DC microgrid with multiple subgrids[J].IEEE Transactions on Power Electronics,2018,33(5):4061-4072.
[9]Nejabatkhah F,Li Y W.Overview of power management strategies of hybrid AC/DC microgrid[J].IEEETransactions on Power Electronics,2015,30(12):7072-7089.
[10]张学,裴玮,邓卫,等.含恒功率负载的交直流混联配电系统稳定性分析[J].中国电机工程学报,2017,37(19):5572-5582.Zhang Xue,Pei Wei,Deng Wei,et al.Stability analysis of AC/DC hybrid distribution system with constant power loads[J].Proceedings of the CSEE,2017,37(19):5572-5582(in Chinese).
[11]Gu Y,Xiang X,Li W,et al.Mode-adaptive decentralized control for renewable DC microgrid with enhanced reliability and flexibility[J].IEEE Transactions on Power Electronics,2014,29(9):5072-5080.
[12]Wu M F,Lu D.A novel stabilization method of LC input filter with constant power loads without load performance compromise in DC microgrids[J].IEEE Transactions on Industrial Electronics,2015,62(7):4552-4562.
[13]王成山,李微,王议锋,等.直流微电网母线电压波动分类及抑制方法综述[J].中国电机工程学报,2017,37(1):84-97.Wang Chengshan,Li Wei,Wang Yifeng,et al.DC bus voltage fluctuation classification and restraint methods review for DC microgrid[J].Proceedings of the CSEE,2017,37(1):84-97(in Chinese).
[14]Amin M,Molinas M,Jing L,et al.Impact of power flow direction on the stability of VSC-HVDC seen from the impedances Nyquist plot[J].IEEE Transactions on Power Electronics,2017,32(10):8204-8217.
[15]Middlebrook R D.Input filter considerations in design and application of switching regulators[C]//IEEE Ind.Applicat.Soc.Annu.Metting.Chicago,lllionios,1976:366-382.
[16]Feng X,Liu J,Lee F C.Impedance specifications for stable DC distributed power systems[J].IEEETransactions on Power Electronics,2002,17(2):157-162.
[17]Rashidirad N,Hamzeh M,Sheshyekani K,et al.Asimplified equivalent model for the analysis of low-frequency stability of multi-bus DC Microgrids[J].IEEE Transactions on Smart Grid,May,2017(99):1-1.
[18]Zhang X,Ruan X,Chi K T.Impedance-based local stability criterion for DC distributed power systems[J].IEEE Transactions on Circuits&Systems I Regular Papers,2015,62(3):916-925.
[19]伍文华,陈燕东,罗安,等.海岛VSC-HVDC输电系统直流阻抗建模、振荡分析与抑制方法[J].中国电机工程学报,2018,38(15):4359-4368.Wu Wenhua,Chen Yandong,Luo An,et al.DC impedance modeling,oscillation analysis and suppression method for VSC-HVDC system in the field of islands power supply[J].Proceedings of the CSEE,2018,38(15):4359-4368(in Chinese).
[20]伍文华,陈燕东,罗安,等.一种直流微网双向并网变换器虚拟惯性控制策略[J].中国电机工程学报,2017,37(2):360-371.Wu Wenhua,Chen Yandong,Luo An,et al.A virtual inertia control strategy for bidirectional grid-connected converters in DC micro-grids[J].Proceedings of the CSEE,2017,37(2):360-371(in Chinese).
[21]李云丰,汤广福,吴亚楠,等.直流电网建模分析与阻尼控制研究[J].中国电机工程学报,2017,37(12):3372-3382.Li Yunfeng,Tang Guangfu,Wu Yanan,et al.Modeling,analysis and damping control of DC grid[J].Proceedings of the CSEE,2017,37(12):3372-3382(in Chinese).
[22]Lu X,Sun K,Guerrero J M,et al.Stability enhancement based on virtual impedance for DC microgrids with constant power loads[J].IEEE Transactions on Smart Grid,2015,6(6):2770-2783.
[23]Zhang X,Zhong Q C,Ming W L.A virtual RLC damper to stabilize DC/DC converters having an LC input filter while improving the filter performance[J].IEEETransactions on Power Electronics,2016,31(12):8017-8023.
[24]Gao F,Bozhko S,Costabeber A,et al.Comparative stability analysis of droop control approaches in voltage-source-converter-based DC microgrids[J].IEEETransactions on Power Electronics,2016,32(3):2395-2415.
[25]郭力,冯怿彬,李霞林,等.直流微电网稳定性分析及阻尼控制方法研究[J].中国电机工程学报,2016,36(4):927-936.Guo Li,Feng Yibin,Li Xialin,et al.Stability analysis and research of active damping method for DC microgrids[J].Proceedings of the CSEE,2016,36(4):927-936(in Chinese).
[26]支娜,张辉,肖曦.提高直流微电网动态特性的改进下垂控制策略研究[J].电工技术学报,2016,31(3):31-39.Zhi Na,Zhang Hui,Xiao Xi.Research on the improved droop control strategy for improving the dynamic characteristics of DC microgrid[J].Transactions of China Electrotechnical Society,2016,31(3):31-39(in Chinese).
[27]Carne G D,Buticchi G,Zou Z X,et al.Reverse power flow control in a ST-fed distribution grid[J].IEEETransactions on Smart Grid,January,2017(99):1-1.
[28]季一润,袁志昌,赵剑锋,等.一种适用于柔性直流配电网的电压控制策略[J].中国电机工程学报,2016,36(2):335-341.Ji Yirun,Yuan Zhichang,Zhao Jianfeng,et al.A suitable voltage control strategy for DC distribution power network[J].Proceedings of the CSEE,2016,36(2):335-341(in Chinese).
[29]Tian Y,Loh P C,Deng F,et al.DC-Link voltage coordinated-proportional control for cascaded converter with zero steady-state error and reduced system type[J].IEEE Transactions on Power Electronics,2016,31(4):3177-3188.
[30]Tian Y,Chen Z,Deng F,et al.Active power and DCvoltage coordinative control for cascaded DC-ACconverter with bidirectional power application[J].IEEETransactions on Power Electronics,2015,30(10):5911-5925.