ANALYSIS OF A HYBRID PWM BASED ON MODIFIED SPACE-VECTOR AND TRIANGLE-COMPARISON METHODS

A classical space-vector pulsewidth modulator (PWM) with equal duratio n of application of zero-state vectors V-0 and V-7 was modified, A fac tor-variable k(0) (proportional to the time of application of vector V -7) was introduced. By changing Lo from zero to one, the duration of a pplication of V-7 can be changed from 0% to 100% of the combined appli cation time for zero-state vectors, Correlation between modified space -vector and triangle-comparison methods (with added zero sequence) was established, The influence of factor k(0) on characteristics of the P WM was investigated. An expression for the optimal value of k(0) that provides minimum ripple in the load current was derived, Salient featu res of the new algorithm are extended linearity (up to a modulation in dex of 1.154), reduced switching losses, and ability to change the cur rent spectrum by changing k(0) every sampling time, The developed algo rithm is suitable for microprocessor and analog implementation, Since the new algorithm combines the theory of space-vector PWM with the eas e of implementation of a triangle-comparison PWM, it is named ''hybrid '' PWM (HPWM).