New switching technique for current control of grid converters for wind power systems

A novel modification is applied to the hysteresis band (HB) modulation technique for direct current control in Grid side converters (GSC). This method employs a pair of hysteresis bands (a positive one and a negative one) and changes these bands according to the conduction times of the inverter switches. The rate of change of generated current is dependent on two factors: the instantaneous grid voltage and the conduction times of the inverter switches. The objective of changing the hysteresis bands is varying the switching frequency to reduce the ripple produced in grid currents. The proposed method is analyzed and tested in switching a voltage source grid connected converter applied in wind power systems. The matlab based simulations and experimental results validate efficacy of the new switching modulation method in decreasing the current ripple, switching losses, and Total harmonic distortion (THD) of Grid current.