Low Voltage Network Operation Research Articles

Decentralized P2P Energy Trading Under Network Constraints in a Low-Voltage Network

The increasing uptake of distributed energy resources in distribution systems and the rapid advance of technology have established new scenarios in the operation of low-voltage networks. In particular, recent trends in cryptocurrencies and blockchain have led to a proliferation of peer-to-peer (P2P) energy trading schemes, which allow the exchange of energy between the neighbors without any intervention of a conventional intermediary in the transactions. Nevertheless, far too little attention has been paid to the technical constraints of the network under this scenario. A major challenge to implementing P2P energy trading is ensuring network constraints are not violated during the energy exchange. This paper proposes a methodology based on sensitivity analysis to assess the impact of P2P transactions on the network and to guarantee an exchange of energy that does not violate network constraints. The proposed method is tested on a typical U.K. low-voltage network. The results show that our method ensures that energy is exchanged between users under the P2P scheme without violating the network constraints, and that users can still capture the economic benefits of the P2P architecture.

Accurate Assessment of Decoupled OLTC Transformers to Optimize the Operation of Low-Voltage Networks

Voltage control in active distribution networks must adapt to the unbalanced nature of most of these systems, and this requirement becomes even more apparent at low voltage levels. The use of transformers with on-load tap changers is gaining popularity, and those that allow different tap positions for each of the three phases of the transformer are the most promising. This work tackles the exact approach to the voltage optimization problem of active low-voltage networks when transformers with on-load tap changers are available. A very rigorous approach to the electrical model of all the involved components is used, and common approaches proposed in the literature are avoided. The main aim of the paper is twofold: to demonstrate the importance of being very rigorous in the electrical modeling of all the components to operate in a secure and effective way and to show the greater effectiveness of the decoupled on-load tap changer over the usual on-load tap changer in the voltage regulation problem. A low-voltage benchmark network under different load and distributed generation scenarios is tested with the proposed exact optimal solution to demonstrate its feasibility.

A Joint Electrical and Thermodynamic Approach to HVAC Load Control

Building energy management (BEM) systems can shift the heating, ventilation, and air conditioning (HVAC) demand of buildings in summer using pre-cooling. The physical and operational constraints of buildings directly impact the operation of low voltage networks (LVNs). There is a gap in the literature on the extent of the electricity consumption and the voltage profiles of LVNs are influenced by different wall constructions of BEM-enabled buildings. In this paper, a joint electrical and thermodynamic model is used to control residential BEMs, taking into account the constraints of the LVN and the buildings. As a case study, the electricity demand of an IEEE LVN with 55 residential buildings are modeled using four common wall constructions: 1) timber clad; 2) brick veneer; 3) reverse brick veneer; and 4) double brick walls. The results show the buildings with higher access to thermal inertia from inside provide enough thermal storage capacity to shift the entire peak-time cooling demand to off-peak periods. Furthermore, the location of a building in LVN affects its HVAC load shifting, with houses farthest from the transformer starting pre-cooling earlier to avoid exceeding the voltage limit. This paper shows the advantage of the joint electrical and thermodynamic model in capturing both the dynamics of HVAC demand for buildings and the electrical dynamics of LVN.

A Coordinated Droop Control Strategy for Overvoltage Mitigation in Active Distribution Networks

In this paper, a centralized control strategy for low-voltage networks is proposed, aiming to coordinate the droop characteristics of the distributed renewable energy sources. The main objectives are the overvoltage mitigation and the optimal network operation in terms of maximum power injection and uniform power curtailment. The distinct features of the proposed method are the incorporation of droop-based control techniques into the conventional optimal power flow formulation and the use of the sensitivity theory as a means to significantly decrease the computational burden. The validity of the developed method is justified using a genetic algorithm, while extensive comparisons with conventional centralized and decentralized control strategies indicate its superior performance in the operation of low-voltage networks.

Adopting smart meter events as key data for low-voltage network operation

This development is part of the UPGRID project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 646531 (http://upgrid.eu/)

Distributed Storage Capacity Reservations in Microgrid for LV Network Operation

Abstract This paper introduces a novel method for Low Voltage (LV) network management with diverse distributed energy storage batteries in microgrid. These batteries are used for demand response, allowing distributed network operators (DNOs) to reserve part of storage capacity for relieving network congestion by releasing stored energy. The major difficulty in carrying out storage capacity reservations among diverse customers is the reserved capacity quantification for each type of customers based on the identified network pressure degree and duration. To overcome this difficulty, the algorithm of storage capacity reservation can be considered from both technical and financial sides. In the proposed approach, the amounts of reserved storage capacities are basically evaluated following two criteria: contribution of customers to network pressure and operational cost of storage battery. Besides, an optimal solution for allocating reservation amount is put forward through an enhanced mixed reservation algorithm. A case study is carried out in a practical network in UK to implement the proposed method for network pressure mitigation and investment deferral.

A probabilistic framework for evaluating voltage unbalance mitigation by photovoltaic inverters

Abstract In three-phase Low Voltage (LV) networks, distributed photovoltaic (PV) units can contribute to voltage unbalance mitigation in case they are connected with the use of three-phase inverters integrating unbalance mitigation control schemes. This paper presents a probabilistic framework that simulates the time-varying action of voltage magnitude and unbalance mitigation schemes, locally implemented by PV inverters in LV feeders. The scope includes evaluating the effect of such strategies, in the context of a long-term techno-economic planning of the LV network, and characterizing LV network operation for increasing the observability of state estimation techniques applied in the Medium Voltage level. The presented framework evaluates the action of four distributed control schemes in an extensive range of possible network states assembled with the use of feeder-specific smart metering (SM) data. The simulation of a real LV feeder with distributed PV generation and historic SM measurements is presented. A control strategy that acts resistively towards the negative- and zero-sequence voltage components, without modifying the total nodal injected power (three-phase damping control strategy), results to be more effective compared with traditionally applied voltage control schemes.

Flexible Demand Control to Enhance the Dynamic Operation of Low Voltage Networks

Moving toward a carbon free energy system has become an objective for many countries nowadays. Among other changes, the electrification of strategic sectors, such as heating and transportation, is inevitable. As a consequence, the current power system load will substantially increase. In this context, the nature of the expected loads (heat pumps, plug-in electric vehicles, etc.) makes the low voltage (LV) networks specially targeted. A promising solution to overcome the challenges resulting from their grid integration is demand response (DR). This paper introduces a hierarchical structure for controlling the DR of a LV grid. This is designed to maximize the grid utilization, thereby reducing the need for reinforcement; accommodate the maximum number of flexible loads; and satisfy the power and comfort requirements from each of the consumers in the network. The validation of the proposed concept is made using a model of an LV network currently operative in Denmark. The results show that by using the proposed strategy a considerable improvement of the minimum system voltage and a better load distribution is obtained.

Impact of Non-Linear Small Power Receivers on Low Voltage Network Operation Conditions

Impact of Non-Linear Small Power Receivers on Low Voltage Network Operation Conditions