A generalized over-modulation methodology for current regulated three-phase voltage source converters

In most motor drive and utility applications, three-phase voltage source converters are required to operate in the over-modulation regions to improve steady-state capabilities and dynamic system performance and transit from the linear modulation region into the overmodulation and six-step modes seamlessly. This work presents a closed-loop current regulation concept for converter fed loads using the generalized space vector (GSVPWM) and generalized discontinuous carrier-based pulse-width modulation (GDPWM) schemes which operates effectively in the linear and overmodulation regions. The harmonic currents generated in these operational modes which naturally degrade the classical PI regulators are eliminated from the controller path by an open-loop harmonic current estimation scheme to ensure current regulation in the synchronous reference frame. The realization of the proposed modulation schemes and current regulation concept are validated by steady-state experimental results and dynamic response of a current regulated inverter feeding an impedance load.