Modelling, design and control of grid connected converter for high altitude wind power application

High altitude wind based renewable energy generating system can be connected to a distribution level grid. The generated power at high altitude above the ground is transmitted at medium voltage DC to the ground based station. Thus, transmitted power is interfaced with the distribution grid at the ground station. This paper presents the power electronic converter (PEC) rated at 100 kW HAWP application that converts medium voltage DC to three phase distribution level grid voltage. The proposed converter topology consists of a neutral point clamped (NPC) three level DC-DC converter followed by three phase grid connected two level inverter. The designed power electronic converter uses four high voltage (HV) rating power semiconductor switches for buck converter before inversion to three phase AC distribution voltages. The active and passive components selection for two stage conversion is presented in the paper. The grid side current is controlled using quadrature axes current control method and inverter switches are switched using space vector modulation (SVM) technique. Simulations of the proposed PEC and control of the inverter are carried out using software programs PSIM-9 and MATLAB. The designed converter converts the 8 kV DC transmission voltage to 415 V grid side voltage with current total harmonic distortion (THD) of about 1.2%.