A potentially beneficial new opportunity is emerging around the exchange of energy between electric vehicles and the electrical energy grid, particularly as more low-carbon energy sources are connecting to the grid. Accordingly, this paper presents an optimization framework to activate the potential capabilities of electric vehicles equipped with bidirectional chargers for energy conditioning (including energy management and power quality improvement) of the future distribution networks. The proposed nonlinear optimization seeks to concurrently enhance the operation performance (using the network voltage deviation index) as well as power quality of the grid (using total harmonic distortion index). The proposed model is tested on a 33-bus distribution network to demonstrate its efficiency and performance.
This paper presents the design of a single-phase electric vehicle (EV) on-board bidirectional charger with the capability of power conditioning. This charger can control its charging/discharging active power based on the demand of EV battery/network or load. Also, it controls reactive power and harmonic current based on the characteristics of the non-linear and linear loads. The topology of the proposed charger consists of the bidirectional AC/DC and buck-boost DC/DC converters, where it can operates in four quadrants in the active-reactive power plane with the capability of harmonic compensation. In the next step, this paper presents a suitable control strategy for the bidirectional charger according to the instantaneous active and reactive power (PQ) theory. Based on the PQ theory, the active and reactive power that include average and oscillatory components obtained based on the demand of non-linear/linear loads and EV battery. Then, the reference current of AC/DC converter of the charger and battery is obtained, and in the next step, the situation of the charger switches is determined using output signals of the proportional-integral and proportional-resonant controllers and pulse width modulation. Finally, the proposed approach is validated and implemented in the OPAL-RT to integrate the fidelity of the physical simulation and the flexibility of the numerical simulations.
Abstract-This study proposes combined framework for proactive operation, i.e. bidirectional active and reactive power 14 management, of the smart distribution network as well as harmonic compensation of non-linear loads using electric vehicles 15 (EVs) equipped with bidirectional chargers. The problem is in the form of non-linear programming (NLP) where the objective 16 function is to minimise the voltage deviation at the fundamental frequency and the total harmonic distortion. The harmonic load 17 flow equations, EVs constraints, system operation and harmonic indexes limits are formulated as problem constraints. The 18 proposed NLP problem is converted to an equivalent mixed integer linear programming (MILP) model using Taylor series and 19 linearisation techniques for AC power flow formulation. Also, the Benders decomposition (BD) algorithm is used to solve the 20proposed MILP problem that is tested on different distribution test networks to demonstrate its efficiency and performance. The 21 results show that the NLP model can be substituted with the high-speed linear programming model. Moreover, the computation 22 speed is improved by using the BD method. Finally, the network and harmonic indexes improved and charging cost reduced 23 using the proposed idea. 24 25
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