Programmed PWM to improve power quality in systems with distributed generation units

摘要

Pulse-Width Modulated (PWM) inverters are widely applied in Distributed Generation (DG) units and power quality equipment owing to their excellent performance and flexible control means. Programmed PWM (PPWM), as a special type of optimal PWM strategy, theoretically allows for setting the fundamental and the selected harmonic amplitudes directly to arbitrary values. The algorithms for solving PPWM problems that could be found in literature, so far, suffer from dependence on good guesses of initial values. This makes them highly impractical for real-time systems. In this paper, a novel Simplex Homotopic Fixed-Point Algorithm (SHFPA) is applied to inverters which interface DG units with the power grid. The numerical transformation and the associated geometrical algorithm render SHFPA fast, accurate and flexible. With typical contemporary digital signal processors, SHFPA can be used to set amplitudes of several tens of harmonics within one cycle of the AC power waveform. Hence, a single SHFPA-controlled DG unit can simultaneously play the roles of a generator and an active filter.