Analysis of current controllers for voltage-source inverter

Current-controlled pulsewidth modulated (PWM) inverters are widely used in high-performance ac drives because they give high dynamic responses in such systems. This paper presents a comparative study of several current controllers. Particular attention is paid to the hysteresis controller and the ramp-comparator controller, due to their simplicity and widespread use. An improved ramp comparator is proposed in which the current error signals are compared to three 120 degrees phase-shifted triangular waveforms. This eliminates the zero voltage vector applied to the inverter and reduces the inherent amplitude and phase errors. Computer simulations are used to compare the performances. Fast Fourier transform technique is used to show the power spectrum of the current waveforms. Experimental results validate the simulated performances.