Microgrid Smooth Off Grid Technology Based on PCS Variable Master-slave Cooperative Control

doi:10.11985/2023.04.033

Abstract

Abstract:

The microgrid changes from grid connected mode to off grid mode. The traditional control methods of energy storage converter and photovoltaic inverter may cause the problems of microgrid system oscillation and overcharge and discharge of energy storage system. The microgrid structure with energy storage converter and photovoltaic inverter running in parallel is adopted. By analyzing the output power of each power supply of microgrid, a method is proposed when microgrid is off grid. Considering the variable master-slave cooperative control strategy of the charged state of the energy storage system, that is, the advantages of master-slave control, peer-to-peer control and hierarchical control are combined to complete the flexible switching of the energy storage converter between the droop control and PQ control of secondary voltage and frequency regulation, realize smooth off grid of microgrid, and prevent overcharge and over discharge of the energy storage system. Finally, a simulation model is built to verify the effectiveness of the proposed method.

Key words: Power conversion system, variable master-slave cooperative control, secondary voltage and frequency regulation, overcharge and over discharge

CLC Number:

TM561

LIU Yonghui, ZHANG Guopeng, SUN Xindi, ZHANG Siyu. Microgrid Smooth Off Grid Technology Based on PCS Variable Master-slave Cooperative Control[J]. Journal of Electrical Engineering, 2023, 18(4): 310-319.

Figures/Tables 19

References 20

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光伏单元输出功率与负载需求功率关系	储能系统SOC情况	PCS的控制方式	ESS1和ESS2的状态
光伏单元输出功率=负载需求功率	SOC1>90%，SOC2>90%	PCS1为下垂控制，PCS2为下垂控制	ESS1和ESS2均无充放电
	SOC1>90%，20%<SOC2<90%
	SOC1>90%，SOC2<20%
	20%<SOC1<90%，SOC2<20%
	SOC1<20%，SOC2<20%
光伏单元输出功率<负载需求功率	SOC1>90%，SOC2>90%	PCS1为下垂控制，PCS2为下垂控制	ESS1放电，ESS2放电
	SOC1>90%，20%<SOC2<90%	PCS1为下垂控制，PCS2为下垂控制	ESS1放电，ESS2放电
	SOC1>90%，SOC2<20%	PCS1为PQ控制，PCS2为下垂控制	ESS1放电，ESS2停止放电
	20%<SOC1<90%，SOC2<20%	PCS1为PQ控制，PCS2为下垂控制	ESS1放电，ESS2停止放电
	SOC1<20%，SOC2<20%	PCS1为下垂控制，PCS2为下垂控制	ESS1停止放电，ESS2停止放电
光伏单元输出功率>负载需求功率	SOC1>90%，SOC2>90%	PCS1为下垂控制，PCS2为下垂控制	ESS1停止充电，ESS2停止充电
	SOC1>90%，20%<SOC2<90%	PCS1为下垂控制，PCS2为PQ控制	ESS1停止充电，ESS2充电
	SOC1>90%，SOC2<20%	PCS1为下垂控制，PCS2为PQ控制	ESS1停止充电，ESS2充电
	20%<SOC1<90%，SOC2<20%	PCS1为下垂控制，PCS2为PQ控制	ESS1充电，ESS2充电
	SOC1<20%，SOC2<20%	PCS1为下垂控制，PCS2为下垂控制	ESS1充电，ESS2充电

参数	数值
大电网相电压、频率值	380 V、50 Hz
ESS直流侧电压	U_dc1=U_dc2=800 V
光伏发电系统直流侧电压	U_dc3=U_dc4=800 V
滤波电路电容、电感	L_f=0.6 mH、C_f=1 500 μF
下垂控制有功、无功指令值	P_n=10 kW、Q_n=0 kVar
下垂系数下垂控制电压、频率额定值 PQ控制指令值	m=1×10^-5、n=3×10^-4 U_n=380 V、f_n=50 Hz P_PV=20 kW、Q_PV=20 kVar