A Hybrid Grid-Wind Energy System Using Voltage Oriented Control and Class C Chopper For An Electric Charging Station

A shunt interconnection made from a wind driven DC machine system, a three phase grid voltage supply, and a DC load representing an electric charging station is investigated The wind driven DC machine system participates with maximum power to the overall active power flow. It uses a class C chopper circuitry controlled properly by a typical maximum power point tracker (MPPT) controller. The grid has the role of supplying active power in case of any power deficiency needed by the DC electric charging station load. Similarly, it has also the role of absorbing active power in case of any additional power generated by the wind driven DC machine system and not needed by the DC load. This is done by using an AC/DC power electronic converter. Hence, the AC/DC power electronic converter should operate either under rectifier or inverter modes. The AC/DC power electronic converter is also operated under the next two conditions: 1-the reactive power expected at the grid voltage bus should be nearly null, 2-harmonics currents often encountered in the grid line currents waveforms should be tolerable. The two latter conditions are fulfilled by using the principle of voltage oriented control (VOC) technique. The performance of the investigated interconnection is simulated in Matlab/Simulink platform. Quite satisfactory results are obtained. The energy resources, that the released energy will be definitely (for sure) insufficient to satisfy the tremendous electric transportation energy demand. A possible and practical solution to overcome the problem of relying on the power generated by the renewable energy resources is to constitute a hybrid DC grid made of a combination of parallel renewable energy resources and interconnect it to the AC grid [1-2]. The DC grid is usually linked to the AC grid through conventional power inverter modules[1-2]. Interconnecting such renewable energy sources with the grid should not harm the performance of the AC grid and that can be possible by respecting standards that have been developed in this regard like the one stated in reference [3]. Most of the developed standards in this regard insist on: 1- controlling the level of harmonics generated by interconnecting power electronics circuitry and injecting them into the AC grid 2- monitoring AC grid bus power factor level. Poor power factor level is manifested by drawing reactive power from AC the grid and consequently creating unnecessary ohmic losses in the AC grid network. satisfaction about the obtained simulation results persists on being able to integrate easily the wind driven system with the AC grid while extracting maximum power from the wind energy system and having a unity power factor at the AC grid bus and less encountered harmonics in the ac line currents.. Key words. Grid-Tied Wind Energy system; AC/DC Converter; Class C Chopper; Maximum Power Point Tracker; Voltage Oriented Control.