Discrete-Time Voltage Controller for Voltage Source Converters With LC Filter Based on State-Space Models

Abstract

State-space control could provide both high dynamic performance and sufficient stability margin to voltage source converters with LC filter. However, an inherent digital delay induced by a digital control system deteriorates performance and even induces instability. In this paper, a discrete-time voltage controller is proposed based on a discrete state-space model. First, a state feedback control with a reference feedforward path is designed in the discrete-time domain with consideration for the digital delay. Second, an output current decoupling path is augmented to minimize the effects of an output current disturbance. Controller gains are derived as the functions of system parameters and design specifications, which is based on a direct pole placement and pole-zero cancellation method in a rotating reference frame. Moreover, a parameter sensitivity and digital implementation are discussed to improve the performance and stability of the proposed controller. The effectiveness of the proposed controller is verified with various experimental results. It shows that a filter resonance is well damped out while maintaining wide voltage control bandwidth.