A Compound Control Strategy for Inverter Output Voltage in Micro-grid System

For poor inverter output voltage quality caused by operation of asymmetric load and nonlinear load in the micro-grid system, a compound control strategy for inverter output voltage was proposed; in this paper, based on positive sequence rotating coordinate system, Proportion Integrator (PI)+ Vector Proportion Integrator (VPI) controller was used to control fundamental voltage and unbalanced voltage. And based on two-phase static coordinate system, VPI controller was used to control harmonic voltage to finally realize voltage quality governance. In addition, DC/AC + z-type grounding transformer topology was adopted to solve supporting problem of single-phase load by a three-phase three-wire inverter. Finally, a 2.5MW converter device was established to carry out an experimental study based on TMS320F28377D controller. The experimental result verified effectiveness of the proposed control strategy. At present, this device has been applied to flexible substation system in Aliyun data center located in Zhangbei County, Zhangjiakou City, China.