Voltage Unbalance Mitigation in Distribution Networks
Summary
Voltage unbalance arises in three-phase distribution networks when phase voltages differ in magnitude or phase angle, typically due to uneven single-phase loads, high penetration of single-phase distributed generation and asymmetrical line impedances. Such unbalance can increase losses, exacerbate heating in rotating machines and transformers, provoke protective device misoperation and compromise power quality. Mitigation strategies span hardware solutions, control algorithms and system planning interventions. At the device level, static var compensators, phase-swapping switches and distribution transformers with on-load tap changers can rebalance phase voltages in real time. Control-based approaches include utilisation of smart inverters to inject active and reactive power tailored to reduce negative-sequence currents, decentralised current controllers employing fuzzy logic or model-predictive schemes, and coordinated optimisation of voltage regulators and distributed energy resources. On a system scale, phase-balancing algorithms based on smart-meter data and optimisation metaheuristics can reassign loads or adjust network configurations to minimise unbalance. Emerging research explores transactive energy frameworks for microgrids that exploit distributed scheduling of energy resources to address asymmetrical power flows. Together, these methods offer a multifaceted toolkit to safeguard reliability, efficiency and power quality in evolving distribution contexts with high renewable integration.
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Voltage Unbalance Mitigation in Distribution Networks publication trend
The graph below shows the total number of articles in voltage unbalance mitigation in distribution networks across all publications each year (not limited to Nature Index journals).
Technical terms
Voltage unbalance: A condition in three-phase systems where magnitudes or phase angles of voltages differ, leading to negative-sequence components.
Voltage Unbalance Factor (VUF): A metric defined as the ratio of the negative-sequence voltage magnitude to the positive-sequence magnitude, expressed as a percentage.
Negative-sequence current: The component of current that rotates in the opposite direction to the positive-sequence component, indicative of asymmetry in the system.
Symmetrical components: A mathematical transformation decomposing unbalanced three-phase quantities into positive-, negative- and zero-sequence sets for analysis.
Smart inverter: A power electronic interface for distributed generation capable of dynamic control of active and reactive power to support grid voltage and frequency regulation.
References
- Voltage imbalance mitigation in an active distribution network using decentralized current control. Protection and Control of Modern Power Systems (2023).
- Coordinated voltage control of three-phase step voltage regulators and smart inverters to improve voltage profile and energy efficiency in unbalanced distribution networks. Energy Reports (2023).
- A Distributed Framework for Minimizing the Asymmetrical Power Request in Multi-Agent Microgrids With Unbalanced Integration of DERs. IEEE Access (2024).
- Review of distribution network phase unbalance: Scale, causes, consequences, solutions, and future research directions. CSEE Journal of Power and Energy Systems (2020).
- Optimization of Voltage Unbalance Compensation by Smart Inverter. Energies (2020).
- Optimal Phase Load Balancing in Low Voltage Distribution Networks Using a Smart Meter Data-Based Algorithm. Mathematics (2020).
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