Centrally Aligned Pulse Based One Cycle Control Technique for PWM Voltage Source Inverters

One Cycle Control (OCC) is a non-linear control technique for switch-mode power electronic converters, which is capable of extracting fast response from the converter. Conventional OCC, when applied to inverters, usually generate edge-aligned pulses, causing harmonics to appear at around switching frequency. This results in an inferior output harmonic profile as compared to conventional Sine-PWM or Space Vector PWM, both of which generate centrally aligned pulses. This paper presents an improved version of OCC, capable of generating centrally aligned pulses for inverters, thereby pushing the higher order harmonics, as seen by the load, to nearly twice the switching-frequency. This technique, nominated as Centrally Aligned Pulse based OCC (CAPOCC) also retains the 'fast-response' feature of conventional OCC, correcting errors within one switching cycle, and requires only the pole-voltages of inverters to be sensed, for its implementation. This paper explains the principle of this CAPOCC technique for both single and three-phase inverters, and explains the mechanism for generation of centrally aligned pulses. Equations are presented to facilitate the design of a CAPOCC based controller for a single-phase full-bridge inverter. The performance of the designed CAPOCC-based inverter is compared with a conventional OCC based inverter through simulations and experiments. The results confirm the superior performance of the proposed CAPOCC based inverter over conventional OCC based inverters.