High-Performance PWM Frequency Changers

Besides the ability to change the frequency and amplitude of output voltages a high-performance frequency changer (FC) should produce sinusoidal output voltages and sinusoidal in-phase input currents and allow bidirectional power flow. The Venturini FC meets all these requirements but has some deficiencies which affect its practicality. Three kinds of improved FC´s¿a new direct FC and its special applications, a current source FC, and a voltage source indirect FC¿which retain all good features of Venturini´s FC and overcome its deficiencies are investigated. Their principles, features, and problems are discussed. New control laws and control circuits are proposed.