DSP-based space-vector PWM pattern generators for three-phase current source rectifiers and inverters

Current source converters (rectifiers and inverters) are usually modulated using off-line pattern generators, due to the complex requirements of the switch gating signals. However, on-line patterns (carrier- and space-vector-based) offer a number of control advantages, such as tracking-error minimization, zero steady-state error, and potential implementation of enhanced control strategies. With the capability of microprocessors and digital signal processors (DSPs), digital space-vector modulation offers an interesting alternative to standard carrier-based modulation techniques. This paper addresses practical issues such as switching-frequency minimization, uncharacteristic-harmonic reduction, and delay compensation. Improved space-vector algorithms are derived that (a) reduce switching frequency, (b) improve reference tracking, and (c) reduce harmonic distortion. Experimental results on a 2-kVA current source rectifier are used to validate the proposed algorithms and control techniques.