Reduction of power losses with smart grids fueled with renewable sources and applying EV batteries

This paper describes a low-voltage grid composed of small, domestic power plants fueled by clean and renewable energy sources and augmented with electric vehicle batteries as power storage devices. We propose that this grid could utilize a complex multifunctional control unit capable of optimizing the working point and charging current of the system, while also implementing active power factor correction, lowering extant harmonic distortion and controlling the voltage level in the low-voltage power lines. The complex controller structure proposed in this paper contains the following novel components: an upper harmonic controller which (together with the connection voltage controller) minimizes the amplitudes of the 3rd, 5th, 7th, 9th, and 11th high order components in the output voltage; and a connection voltage controller which controls the energy flow between the low-voltage network, its renewable energy sources and the electrical vehicle batteries. Unlike other similar approaches, the harmonic controller proposed in this paper does not rely on a measured current signal but rather optimizes the voltage shape, the latter of which depends on the nonlinear distortion of the whole low-voltage transformer area and determines additional power losses. We analyzed the proposed controller via simulations in a Matlab environment and as a result, achieved substantial improvements to the output voltage, current waveform and energy flow of the system's low-voltage conditions. Our calculations show that the implementation of substantial reductions in CO2 emissions could be achieved for an average household. The robustness of the method against nonlinear loads and fluctuations in overloads and overproductions was also tested. (C) 2012 Elsevier Ltd. All rights reserved.