An analytical approach to steady-state current control properties of power converters featuring discrete-time switching

Power converters with semiconductors switching only at predefined, equidistant instants - known as ldquodiscrete-time switchingrdquo, ldquosynchronized switchingrdquo or ldquoclocked commutationrdquo - show considerably different current control behavior compared to pulse-width modulated (PWM) converters with linear current con trollers. This paper presents and explains some of the effects of discrete-time-switching on output current waveforms, especially when using a predictive switching state selection algorithm. Typical characteristics of generated switching state patterns are presented. A single-phase and a three-phase inverter controlled by a predictive discrete-time modulation strategy are considered. Analytical, experimental and simulation results show that average switching frequency and error current RMS are well defined, in spite of the inherent randomness of the control scheme.