| Abstract |
A voltage sourced rectifier control scheme for use with ac / dc / ac variable speed drives is presented in this paper. A control scheme is derived which directly calculates the duration of time spent on the zero state and on each switching state adjacent to the reference vector, over a constant switching interval, in order to drive the line current vector to the reference vector. In addition, under transient conditions, when dead-beat control is not possible, a control scheme is presented which ensures the line current vector is driven in the direction of the reference current vector. The current reference for the rectifier controller is derived from the bus voltage error and a feedforward term based on the estimated converter output power. The proposed space vector-based rectifier regulator is shown to exhibit improved harmonic and transient performance over existing per-phase duty cycle prediction methods, especially at modulation indices near unity. The dead-beat control of the rectifier input current is accomplished every half-cycle with constant switching frequency, while still symmetrically distributing the zero state within the halfcycle period. In this way, satisfactory performance under various operating conditions is achieved with relatively low switching frequencies and high bus yoltage ripple. |
