Analysis of a hybrid PWM based on modified space vector and triangle comparison methods

Classical space vector PWM with equal duration of application of zero state vectors V₀ and V₇ was modified. A factor-variable k₀ (proportional to the time of application of vector V₇) was introduced. By changing k₀ from 0 to 1, the duration of application of V₇ can be changed from 0% to 100% of the combined application time for zero state vectors. Correlation between modified space vector and triangle comparison methods (with added zero sequence) was established. The influence of factor k₀ on characteristics of the PWM was investigated. An expression for the optimal value of k₀ which provides minimum ripple in the load current was derived. Salient features of the new algorithm are: extended linearity (up to 1.154), reduced switching losses and ability to change the current spectrum by changing k₀ every sampling time. The developed algorithm is suitable for microprocessor and analog implementation. Since the new algorithm combines theory of space vector with ease of implementation of a triangle comparison PWM it is named “hybrid” PWM (HPWM)