SENSORLESS DIRECT POWER CONTROL FOR THREE-PHASE GRID SIDE CONVERTER INTEGRATED INTO WIND TURBINE SYSTEM UNDER DISTURBED GRID VOLTAGES

Abstract

Wind turbines with permanent magnet synchronous generator (PMSG) are widely used as sources of energy connected to a grid. The studied system is composed of a wind turbine based on PMSG, a bridge rectifier, a boost converter, and a controlled inverter to eliminate low-order harmonics in grid currents under disturbances of grid voltage. Traditionally, the grid side converter is controlled by using the control VFOC (Virtual Flux Oriented Control), which decouple the three-phase currents indirect components (id) and in quadratic (iq) and regulate them separately. However, the VFOC approach is dependent on the parameters of the system. This paper illustrates a new scheme for the grid-connected converter controller. Voltage imbalance and harmonic contents in the three-phase voltage system cause current distortions. Hence, the synchronization with the network is an important feature of controlling the voltage converter. Thus, a robust control method is necessary to maintain the adequate injection of the power during faults and/or a highly distorted grid voltage. The proposed new control strategy is to use the direct power control based virtual flux to eliminate side effects induced by mains disturbances. This control technique lowers remarkably the fluctuations of the active and reactive power and the harmonic distortion rate. The estimated powers used in the proposed control approach is calculated directly by the positive, negative, and harmonic items of the estimated flux and the measured current without line sensor voltage.

Keywords

• direct power control based virtual flux
• disturbances of grid voltage
• permanent magnet synchronous generator