A Control Bandwidth Optimized Active Damping Scheme for LC and LCL Filter-Based Converters

Abstract

Control bandwidth and damping performance are two key specifications for high-order LC and LCL filter-based converters. The damping of high-order filter-based converters has been extensively studied. However, the control bandwidth issue was ignored. The quantitative relationship between the control gains and bandwidth is still unclear. Moreover, the delay compensator was designed independently without considering the interactions with the main controller. This paper proposes a control bandwidth-optimized active damping control strategy for the LC and LCL filter-based converters to overcome these shortcomings. With the proposed generalized controller, the close loop transfer function of the $\text{N}^{\mathrm {th}}$ order filter-based converter can be simplified to an $\text{N}^{\mathrm {th}}$ order low pass filter with an adjustable cutoff frequency. This greatly simplifies the control bandwidth optimization. To alleviate the negative influence of the computational delay on the control bandwidth, a novel delay compensator is proposed. To reach an overall optimized control performance, the particle swarm optimization (PSO) method is used to optimize the controller and delay compensator parameters simultaneously to realize both high control bandwidth and good damping performance. Experimental results verify the effectiveness of the proposed novel controller.

Keywords

• Active damping
• current source converter
• LC filter
• LCL filter
• optimal control
• three-phase converter