A multimodule parallelable series-connected PWM voltage regulator

This paper presents the analysis and design of a single-phase voltage regul ator (VR) and its multimodule parallel control, The VR employs the pulsewid th modulation three-arm rectifier-inverter topology, The inverter side adju sts the load voltage with the series regulating structure aiming to minimiz e converter capacity and attain higher efficiency, The rectifier side regen erates the load power and executes the active power filter function to achi eve unity power factor. Based on such high-performance VR, a resistive droo p method combined with the P-V droop and Q-delta shift scheme is then propo sed to control the current sharing such that multiple VRs can be paralleled directly without any control interconnection. The proposed parallel contro l technique possesses the features of fast response, precise voltage regula tion, equal fundamental and harmonic current sharing, tolerance for paramet er mismatch, and so on, Two prototype 1-KVA VRs are implemented, and the ef fectiveness is demonstrated by some simulation and experimental results.