This paper proposes a control approach and supplementary controllers for the operation of a hybrid stand-alone system composed of a wind generation unit and a conventional here generation unit based on synchronous generator (CGU).The proposed controllers allow the islanded or isolated operation of small power systems with predominance of wind generation.As an advantage and a paradigm shift, the DC-link voltage of the wind unit is controlled by means of a conventional synchronous generator connected to the AC grid of the system.Two supplementary controllers, added to a diesel generator (DIG) and to a DC dump load (DL), are proposed to control the DC-link voltage.The wind generation unit operates in V-f control mode and the DIG operates in PQ control mode, which allows the stand-alone system to operate either in wind-diesel (WD) mode or in wind-only (WO) mode.
The strong influence of the wind turbine speed variations in the DC-link voltage is mitigated by a low-pass filter added to the speed control loop of the wind turbine.The proposed control approach does not require the use battery bank and ultra-capacitor to control the DC-link voltage in wind generation Tank units based on fully rated converter.