Location Optimisation of EVC Point of Coupling for Minimising Voltage Harmonic Levels of a UK Based LV Power Distribution Network

Despite an increase in electric vehicle chargers (EVCs) connecting to low-voltage (LV) power distribution networks managed by Distribution Network Operators (DNOs) and National Grid ESO [1] expecting approximately 33 million electric vehicles (EVs) on United Kingdom (UK) roads by 2050 under a ‘falling short’ scenario, the optimised location for installing EVCs on an LV DNO network with respect to harmonics has not been fully explored. The purpose of this paper is to investigate the optimal point of coupling for EVCs to minimise the steady-state voltage total harmonic distortion (THDv) on a radial LV DNO network under both normal and steady-state fault conditions. The conclusions will aid DNOs with future network planning and design. Minimising harmonics is important. Balda et al. [8] explains that harmonics can increase the risk of computer errors and cause communication interferences. Whilst Bhattacharyya et al. [9] explains that harmonics increase the risk of motor overheating and reduce the life of transformers, increasing the risk of power cuts. Using MATLAB, a simulation system for a radial 230m LV feeder based upon a suburban residential LV DNO network was created and was divided into eleven sections (busses) with base load connected, each with the capacity for an EVC to be connected to all three phases. Each two-buses were connected with impedance which represents cables. The first and last bus represents the first and last 5% of the network length. The remaining busses each represent 10% of the network length. A broad range of scenarios were generated by changing network parameters. These parameters include: Using two algorithms, the optimal bus for EVC point of coupling with respect to lowering the steady-state THDv was identified. The first algorithm is based on the Elephant Herding Optimisation (EHO) technique (Wang et al. [19] and Meena and Yang [18]). The second algorithm for comparison is based on the Monarch Butterfly Optimisation (MBO) technique (Wang et al. [19]). Alterations have been made to these scripts to allow them to solve the optimisation of EVC point of coupling with respect to THDv. It was found that for all scenarios except for the ’50 kVA transformer’ and ‘PV generation connected to all busses’ scenarios, the optimal EVC point of coupling was the 1st bus, representing the first 5% of the network fed from the 11 kV:400 V transformer. This aligns with what would be expected since the shorter the distance current harmonics need to travel, the lower the cable impedance and the lower the magnitude of harmonic voltage drop generated as per Ohms law.