Model Predictive Switching Pattern Control for Current-Source Converters With Space-Vector-Based Selective Harmonic Elimination

This paper presents a model predictive switching pattern control (MPSPC) for a current-source converter (CSC), which achieves superb low-order harmonics elimination performance in steady state and improved transient responses. Based on a proposed space-vector-based selective harmonic elimination (SHE) method and prediction of load current at the next sampling instant, MPSPC prefers to following a precalculated SHE-pulse width modulation (PWM) pattern in steady state, and governing the CSC through a model predictive control (MPC) approach during transients. In comparison with existing schemes, the advantages of MPSPC are threefold: First, quantization error, introduced by a constant sampling frequency in MPC and degrading steady-state low-order harmonic elimination, is mitigated in the proposed scheme. Second, there is no weighting factor in the cost function, as used in existing schemes. Finally, MPSPC is totally realized based on one-step prediction, which simplifies the structure of the scheme. Both simulation and experimental results verify the steady state and dynamic performance of MPSPC with different SHE-PWM patterns.

I. Introduction

Recently, in medium-voltage (MV) motor drives, pulse-width-modulated (PWM) current-source converters (CSCs) appear to be a good alternative to voltage-source converters (VSCs) due to their advantages including four-quadrant operation, reliable short-circuit protection, machine-friendly waveforms, and reduced cost [1]. As Fig. 1 shows that the CSC is composed of six symmetrical gate-commutated thyristors with reverse voltage-blocking capability. On the dc side is an ideal current source, which is usually obtained by a current-source rectifier (CSR) and a series inductor in practice. A three-phase capacitor must be connected at the output of the CSC to assist the commutations of switching devices and also used as a filter. Fig. 1.

Topology of a single-bridge CSC.