Voltage-Based Droop Control of Electric Vehicles in Distribution Grids under Different Charging Power Levels

Muhandiram Arachchige Subodha Tharangi Ireshika,Peter Kepplinger,Ruben Lliuyacc-Blas

doi:10.3390/en14133905

Muhandiram Arachchige Subodha Tharangi Ireshika, Peter Kepplinger + Show 1 more

Open Access

https://doi.org/10.3390/en14133905

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Abstract

If left uncontrolled, electric vehicle charging poses severe challenges to distribution grid operation. Resulting issues are expected to be mitigated by charging control. In particular, voltage-based charging control, by relying only on the local measurements of voltage at the point of connection, provides an autonomous communication-free solution. The controller, attached to the charging equipment, compares the measured voltage to a reference voltage and adapts the charging power using a droop control characteristic. We present a systematic study of the voltage-based droop control method for electric vehicles to establish the usability of the method for all the currently available residential electric vehicle charging possibilities considering a wide range of electric vehicle penetrations. Voltage limits are evaluated according to the international standard EN50160, using long-term load flow simulations based on a real distribution grid topology and real load profiles. The results achieved show that the voltage-based droop controller is able to mitigate the under voltage problems completely in distribution grids in cases either deploying low charging power levels or exhibiting low penetration rates. For high charging rates and high penetrations, the control mechanism improves the overall voltage profile, but it does not remedy the under voltage problems completely. The evaluation also shows the controller’s ability to reduce the peak power at the transformer and indicates the impact it has on users due to the reduction in the average charging rates. The outcomes of the paper provide the distribution grid operators an insight on the voltage-based droop control mechanism for the future grid planning and investments.

Highlights

The electrification of the transportation sector provokes many challenges in the power system operation, most notably in the low voltage (LV) distribution networks [1,2,3]
Our goal is to find, if the LV distribution grids are able to comply with the voltage magnitude standards with droop controlled electric vehicles (EV) charging for all combinations of penetrations and currently available residential charging power levels
The European standard EN50160 specifies that the 10-min rms value of the supply voltage in LV distribution networks should not deviate from the nominal value more than 10% for 95% of the time within a week

Summary

Introduction

The electrification of the transportation sector provokes many challenges in the power system operation, most notably in the low voltage (LV) distribution networks [1,2,3]. Demand side management (DSM) strategies exploit the flexibility of EV charging to reduce these adverse impacts on the grid operation [9,10,11,12] In this manner, DSM approaches enable the efficient use of existing network capacity and reduce the cost-sensitive grid reinforcements even at high EV penetrations. In contrast to other approaches, a voltage dependent control mechanism demands no communication infrastructure [17]. It can be integrated into the existing network at low costs and is robust as it is not subject to potential communication failures

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Results

Conclusion