Researches on Control Strategies of Modular Inverters Paralleling in the Power Grid

Abstract

Abstract:

Inverters connecting distributed power generators and micro-grid use modular structure, which is not safe and efficient because of the randomness and volatility of transmission power. This article builds the grid inverter system based on directly paralleled inverter structure. According to the DC side model and efficiency model of inverter, relationships between transmission power and efficiency are analyzed. For a changing transmission power, the efficient and reliable switching strategies are developed. Besides, synchronous controller and circulating current restraining controller are designed. The simulation and analysis show that the control strategies can not only switch the grid inverters smoothly, but also make the distributed generators connect to grid safely and efficiently.

Key words: Modular inverters, efficiency of inverter, restraining of zero-sequence circulating current, switching control strategies, improved synchronous controller

CLC Number:

TM711

Zhang Mingrui,Xie Qingqing,Lin Xianqi,Ouyang Li. Researches on Control Strategies of Modular Inverters Paralleling in the Power Grid[J]. Journal of Electrical Engineering, 2015, 10(7): 48-56.

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状态	P_sys	P_sys变化程度	P_in
1	不变	恒定值	=P_ratedn
2	不变	小范围波动	=P_ratedn
3	增大	未引起逆变系统超载	=P_ratedn
4	增大	导致逆变系统超载	>P_ratedn
5	减小	未引起逆变系统轻载	=P_ratedn
6	减小	导致逆变系统轻载	<P_ratedn

	参数	数值
高压直流	V_dc/V	18 000
滤波器	R/Ω	0.01
	L/mH	22.27
	C/μF	31
下垂系数	m/(10^-6rad/kW)	6
下垂系数	n/(10^-2rad/kvar)	6
双环控制	k_i_p	[115,0.057 7]
双环控制	k_i_i	[205 944,333]
零序环流控制	k_0p	10
零序环流控制	k_0i	1 000
载波频率	f_z/Hz	3 000

			工况
	1	2	3	4	5
时间/s	0~0.5	0.5~1.0	1.0~1.5	1.5~2.0	2.0~2.5
P_in/kW	500	700	600	200	1 000