Extended voltage swell ride-through capability for PWM voltage-source rectifiers

Voltage swells are one of the most harmful voltage disturbances for static power converters. A supply voltage increase may severely damage or trip converters, causing production and revenue losses. In the case of the PWM voltage source rectifier, a swell causes saturation of its control system, followed by a transition to 6-pulse operation that leaves the DC-link bus uncontrolled. This paper presents a nonlinear control strategy to effectively deal with voltage swells. The proposed scheme takes two actions, first, it exploits the DC-link voltage capacity by allowing dynamic over modulation, and secondly it draws inductive current to maintain control over the DC-link bus in case the former action does not suffice. This is realized using decision-making space vector modulation, which completely covers both sinusoidal (M<0.907) and over-modulation ranges (0.907<M< 1) requiring minimum processing capacity. Further, a nonlinear control strategy is employed to linearize and decouple the converter d-q axes dynamics, assuring a dynamic response totally independent from the operating point. The latter is a desirable feature for high-performance ac drives. Finally, experimental results from a TMS320C32 DSP based system are presented and used for evaluation of the proposed control strategy