Voltage injection method for boundary expansion of output voltages in three shunt sensing PWM inverters

This paper describes boundary conditions for phase current reconstruction of a three current-shunt inverter and suggests a voltage injection method to expand the measurable areas. The boundary conditions are derived on voltage vector plane for symmetric space vector PWM. For the expansion of the areas, different voltages are injected depending on the position of the voltage vector with double sampling. When voltage vector is located in the insensible area, additional voltage is injected to place the voltage vector in the measurable area during next half of switching period and compensation voltage is added in the other half period. Voltages with minimum magnitudes are chosen to minimize the current ripples. Simulation results are presented to support the effectiveness of boundary condition derivation and proposed voltage injection method.