Strategies Comparison for Voltage Unbalance Mitigation in LV Distribution Networks Using EV Chargers

Abstract

The increasing penetration of Electric Vehicles (EVs) in LV distribution networks can potentially cause voltage quality issues such as voltage unbalance and under-voltage conditions. According to the EV charger characteristics, some strategies can be adopted to mitigate the aforementioned effects. Smart decentralized charging controls seem to be a more practical solution than centralized controls, since there is no need for communication because they rely only on local measurements. The four most relevant decentralized charging strategies, two for single-phase and two for three-phase EV chargers, have been implemented in a typical three-phase four-wire European LV distribution network. Simulations have been carried out for scenarios with single-phase EV chargers, three-phase EV chargers, and a combination of both. Single-phase controls are aimed at under-voltage regulation, while three-phase controls are focused on mitigating voltage unbalance. Results show that the implementation of a decentralized EV charging control is an adequate solution for Distribution System Operators (DSOs) since it improves the reliability and security of the network. Moreover, even though decentralized charging control does not use any communication, the combination of three-phase and single-phase controls is able to mitigate voltage unbalance while preventing the under-voltage condition.

Review of Distribution Network Phase Unbalance: Scale, Causes, Consequences, Solutions, and Future Research Direction

“…Phase unbalance is also widespread in continental Europe. European LV distribution networks are mainly three-phase four-wire networks, where the three phases have uneven load connections [4]. For example, in Denmark where domestic customers are mainly supplied with three-phase power, distribution system operators do not have control over which phase each appliance is connected to [22].…”

“…For instance, it is common that one phase has a peak current of 300A and another phase only has 150A. Main causes for phase unbalance are: 1) an uneven allocation of single-phase loads/customers across the three phases [2], [3], [4]; 2) random load behavior [2], [5]; 3) network structural asymmetries, e.g. the existence of single-phase laterals [6] and unequal phase impedances [7], [8]; and 4) the occurrence of unbalanced faults [9].…”

Review of Distribution Network Phase Imbalance: Scale, Consequences, Solutions, and Future Research Direction

“…Phase imbalance is also widespread in continental Europe. European LV distribution networks are mainly three-phase four-wire networks, where the three phases have uneven load connections [4]. For example, in Denmark where domestic customers are mainly supplied with three-phase power, distribution system operators do not have control over which phase each appliance is connected to [22].…”

“…For instance, it is common that one phase has a peak current of 300A and another phase only has 150A. Main causes for phase imbalance are: 1) an uneven allocation of single-phase loads/customers across the three phases [2], [3], [4]; 2) random load behavior [2], [5]; 3) network structural asymmetries, e.g. the existence of single-phase laterals [6] and unequal phase impedances [7], [8]; and 4) the occurrence of unbalanced faults [9].…”

Review of Distribution Network Phase Unbalance: Scale, Causes, Consequences, Solutions, and Future Research Direction

“…For instance, it is common that one phase has a peak current of 300A and another phase only has 150A. Main causes for phase unbalance are: 1) an uneven allocation of single-phase loads/customers across the three phases [2], [3], [4]; 2) random load behavior [2], [5]; 3) network structural asymmetries, e.g. the existence of single-phase laterals [6] and unequal phase impedances [7], [8]; and 4) the occurrence of unbalanced faults [9].…”