A new voltage sensitivity-based distributed feedback online optimization for voltage control in active distribution networks

In order to meet the high permeability and the access of large scale distributed generation, at present and in the future, active distribution network becomes the trend of smart grid research. This paper introduces the influence of distribution network voltage distribution and stability of distributed energy access based on active distribution network; The reactive power and voltage optimization control method of active power distribution network is summarized from the aspects of optimal voltage regulation measure, voltage regulation measure of power network equipment, reactive power optimal dispatch of power system, and so on. Analysis of the current status of the research, and summarized the existing active distribution network with a distributed power pickup distribution network reactive power and voltage control of the existence of some problems and the insufficiency still some problems that must be solved in the study of reactive power and voltage optimization control of active distribution network are pointed out.

Advancements in data-driven voltage control in active distribution networks: A Comprehensive review

With increasing connection of distributed generations (DGs), the power flow in electric distribution network is no longer unidirectional and the network has become active distribution network. Thus, the connection of DGs in electric distribution networks has created a challenge for distribution network operators due to bidirectional power flow. One of the main technical challenges of an active distribution network is to maintain an acceptable voltage level in the system. This has initiated efforts in using various voltage control strategies to regulate the network voltage profile so that the voltage is maintained at its allowable voltage limits. A number of voltage control methods have been applied to solve voltage control problems associated with the connection of DGs in a distribution system. These voltage control strategies may be classified as decentralized or distributed and centralized or coordinated voltage control. From the literature, a number of coordinated voltage control strategies have been implemented to provide better and faster control to the system. This chapter presents an improved coordinated voltage control method in active electric distribution network by coordinating the three voltage control methods, namely, power factor control, on load tap changer control and generation curtailment control. These voltage control methods are coordinated using fuzzy logic by considering the load bus voltages and DG power as inputs and the voltage control actions as the outputs. The fuzzy logic if-then control rules which are generated to build the fuzzy logic control system are based on the simulations results as well as from the previous works. Results obtained using the fuzzy logic based coordinated voltage control has shown that the voltages are able to be kept within its permissible limits.

This paper proposes a hierarchical multi-stage approach based on a distributed level phasor measurement unit (µPMU) at local controllers and a phasor data concentrator (PDC) at the central control unit to restore system voltage when it exceeds the limits recommended by the IEEE 1547-2018 standard. The proposed algorithm does not need an accurate system model or employ optimization solutions. Therefore, it has less implementation complexity and would be popular among distribution network service providers (DNSPs) and distribution network operators (DNOs) as it does not suffer from cost and computational complexity limitations. A PMU-PDC-based communication platform has been developed as a more efficient alternative to the supervisory control and data acquisition (SCADA) system, and provides superior characteristics, including a higher sample rate, higher data resolutions, and faster communication. The proposed coordinated algorithm aims to postpone power generation curtailment in distributed energy resources (DERs) with overvoltage problems (local DERs) by incorporating all the DERs that are not subjected to voltage violation (remote DERs) by absorbing their maximum reactive power capacity. If the system voltage has not recovered after absorbing all of the reactive power capacity of all the DERs, a reduced active power curtailment proposed by the algorithm is then applied to the system to control the voltage. The proposed strategy has been simulated in MATLAB and applied to IEEE 13-bus and IEEE 33-bus radial distribution benchmark systems to validate the performance of the system, in terms of its ability to coordinate voltage control and the accuracy of the PMU-PDC-based communication interface.

Active Distribution Networks are Multi-Input Multi-Output (MIMO) systems with coupled dynamics, which cause interactions among the control loops of Distributed Energy Resources (DERs). This undesired effect leads to performance degradation of voltage control. To mitigate the effects of this unavoidable coupling, the present paper proposes a systematic design procedure based on the analysis of the interaction’s sources. In detail, each DER is equipped with a double-loop PI to control the active and reactive power output of the voltage source converter, which connects the DER to the network’s node. Furthermore, to guarantee ancillary services, the two loops are coupled by a simple mechanism of cooperation of the active power to voltage regulation realized by a filtered droop law. To achieve voltage regulation with reduced loop interactions, the PI parameters and the filter’s pulse are designed according to a procedure with two sequential steps based on the Internal Model Control (IMC) technique. Simulation studies are finally presented to demonstrate that the proposed design method achieves both reduction of the loop interaction and robust voltage control in the presence of model parameter uncertainty in the MIMO plant, modeling various operating conditions of the ADN, including a step connection of large loads, renewable energy source variations, and changes in the substation transformer ratio.

Abstract: In recent decades, the integration of distributed energy resources (DER), primarily solar and wind, has transformed distribution grids from passive to active systems, creating challenges for grid controllability and asset utilization. Due to the intermittent and unpredictable nature of DER, expectations of improved voltage stability and profiles are often unmet in real-world operations. This has introduced significant issues for Distribution System Operators, particularly concerning voltage control and asset aging. Traditionally, voltage regulation relied on transformer tap changers, which are not equipped to handle the fast, dynamic changes caused by DER. Frequent tap adjustments accelerate transformer aging, while weak grid connections, such as in rural or mountainous areas, can lead to voltage collapse. Additionally, mismatches between generation and demand often cause active power flow to exceed infrastructure limits, leading to renewable energy curtailment or restricted grid connections. This study examines a weakly connected distribution grid in a mountainous region of Georgia, integrating 200 kW rooftop solar photovoltaic (PV) systems, a 200 kW ground-mounted solar plant, and a 200 kW hydropower plant. Due to the high costs and geographical constraints associated with network reinforcements in such regions, the study explores the deployment of distribution Flexible alternating current (AC) Transmission Systems (FACTS) devices, specifically Static Volt-Ampere-Reactive (VAR) Compensator (SVC) devices, as an effective solution. The study focuses on how improvements can be achieved through reactive power compensation and advanced voltage regulation, addressing voltage instability, and enhancing power flow management. Multidomain analysis highlights the effectiveness of SVC devices in managing the challenges of DER integration while deferring costly grid reinforcements.Cite this article as: G. Arziani and T. Elizarashvili, “FACTS for effective DER integration into the Georgia distribution grids,” Turk J Electr Power Energy Syst., 2025; 5(2), 105-113.

This paper highlights the importance of chronology on voltage protection and control apparatuses in studies of voltage security in active distribution networks with high generation capacity. This paper presents simulation results of a real-life example of a long rural distribution feeder having three voltage regulators in cascade, and a customer whose demand accounts for a large percentage of the total feeder load. The customer is also an independent power producer and its location at the far end of the feeder yields an intricate voltage protection coordination when the customer ramps up and down its own generation at the peak-demand period.

The transition from big conventional bulk generation to small dispersed renewable electricity production coupled at medium and lower voltage levels resulted in bi-directional power flow and an active distribution network, which was previously considered to be a passive network. This paradigm shift brings many challenges for protection performances and coordination. As a result, this paper first investigates the impacts of Distributed Energy Resource (DER) integration on distribution protection and then applies the hardware SEL 451 relay for validation. Two of the most common protection failures with DER integration, namely, reverse power flow and sympathetic tripping cases, are examined for a microgrid in this study. Firstly, the system is modeled in PowerFactory for short circuit calculation and protection coordination study. With the help of PowerFactory simulation, coordinated relay settings are subsequently extracted for validation in hardware in the loop testing with SEL 451 relay in real-time digital simulation (RTDS). Both simulation case studies and hardware tests have shown that the DER contribution in healthy conditions as well as during the fault can result in maloperation of the relay. Different from the traditional power amplifier-based testing, the hardware in the loop testing in this work uses Low Energy Analog (LEA) signals output from the GTAO card of RTDS feed directly to SEL 451 relay. Two different feedback methods with Digital Input (DI) and IEC GOOSE signal are tested to compare the time of operation in each case.

Protection schemes are essential in active distribution networks and microgrids’ reliable, efficient, and flexible operation. However, the protection of these networks presents significant challenges due to operational changes, such as variations in topology, distributed energy resources connection/disconnection, and microgrid operating modes, among others. This paper proposes an adaptive protection scheme based on overcurrent devices with several setting groups based on artificial intelligence algorithms. The developed strategy is composed of two stages. In the off-line stage, a clustering technique is employed to group the active distribution network operating scenarios exhibiting similarities. The optimal settings for the protection devices are determined for each set of scenarios. On the other hand, in the on-line stage, the protection strategy’s implementation and operation, considering the active distribution network’s existing communication system, are defined. Furthermore, the approach formulates the overcurrent relay coordination as a mixed-integer non-linear optimization problem, and as a result, the optimal setting of the overcurrent protection devices is obtained. It aims to minimize the operating time, considering the transformers’ thermal limits, fuse operating curves, and overcurrent relay settings. The solution is determined by using an Augmented Lagrangian genetic algorithm. The presented protection scheme is validated on the modified IEEE 34 node test feeder, considering the main operating scenarios of the active distribution networks, such as topology changes, distributed energy resource connection/disconnection, and microgrid operating modes (on-grid and off-grid). The results obtained and its easy implementation indicates the high potential for real-life applications.

Reliable voltage control of active distribution network can reduce line loss, improve the voltage quality of the power grid and ensure the safe, economic and high-quality operation of the power grid. Access of DG changes the distribution of feeder voltage, which has an impact on traditional voltage regulation measures. However, different location of DG has a different effect on the voltage distribution of the distribution network. Moreover, after multiple DG access, their reactive power and on-load tap changer ( OLTC ) access also directly affect the effect of voltage regulation. Therefore, this paper proposes a voltage regulation scheme of active distribution network. Firstly, the best access location of DG is determined by analyzing the sum of the absolute value of voltage offset of each node and the power loss of the line; secondly, the local voltage regulation domain of DG and OLTC is divided; finally, the model of IEEE 33-node active distribution network is constructed, and the simulation results verify the effect of the proposed voltage regulation scheme.

Active distribution network is an effective solution to realize the optimizing operation of integrating large-scale distributed energy into distribution network. The intermittency of distributed energy makes the traditional PI control dissatisfying the requirement on the active distribution network control, this paper proposed a method based on model predictive control to apply to the coordination control of active distribution network according to the multi-layer coordination control characteristics of the active distribution network. And uses the dynamic matrix control algorithm to simulate the regional autonomous control in active distribution network with Matlab/Simulink, the simulation results show the effectiveness of the model predictive control method.

In recent years, the penetration rate of intermittent distributed generation (DG) in active distribution networks has been steadily increasing, leading to prominent issues such as voltage violations and network congestion. Coordinated operation of soft open points (SOPs) and distributed energy storage systems (DESSs) enable flexible resource management in both spatial and temporal dimensions, allowing real-time voltage regulation and flow control. This enhances the controllability, sustainability, and economic efficiency of the distribution network, ultimately improving user satisfaction. The optimization of this coordinated configuration has become a central challenge in research. Taking the different characteristics of DESSs and SOPs into account, this paper proposes a coordinated configuration method by introducing local marginal price (LMP) under the configuration scheme. The framework is modeled as a three-level problem, including planning and operation levels. Initially, typical scenarios are generated to address the uncertainty of distributed generation operation. At the upper level, the DESS configuration is optimized to minimize annual operational costs, while at the middle level, SOPs are planned based on the annual comprehensive operational cost of the distribution network. At the lower level, the objective is set as social welfare maximization to reflect user satisfaction by incorporating LMP as a planning indicator. It is then transformed and solved as a mixed-integer second-order programming model with a hybrid optimization algorithm. The model is established with the modified IEEE 33-node distribution system as a case study to validate the feasibility of the proposed configuration method. The case study results demonstrate the effectiveness of the proposed approach in optimally configuring SOPs with DESSs to reduce overall annual operating costs and enhance the economic efficiency of the system.

High penetration of distributed renewable energy introduces significant uncertainties to active distribution networks. Optimal control methods accounting for inherent uncertainties are needed to facilitate economic and reliable operation of active distribution networks. This paper proposes a stochastic receding horizon control method based on modified stochastic model predictive control framework to integrate high penetration of distributed generation. Multiple controllable resources are jointly optimized over a finite prediction horizon while ensuring relevant security restrictions. The simplified Z-bus sensitivity for active distribution networks is developed for computationally efficient estimation of system nonlinearity with high accuracy, and is combined with the sequential linear programming to iteratively derive the linear state space model for compensation of cumulative modeling errors. Furthermore, the voltage limitations are reformulated as chance constraints to indicate the probabilistic reliability index of voltage qualification rate, and achieve tradeoffs between cost reduction and voltage regulation. The affine-disturbance feedback control policy is leveraged here to enforce close-loop control performance and analytically transform intractable chance constraints into second-order cone constraints. Comprehensive case studies based on 33-bus and 123-bus distribution systems are carried out to demonstrate the capability and effectiveness of the proposed approach in terms of modeling accuracy, control performance, cost reduction, and method scalability. The proposed approach can effectively enforce voltage regulation against uncertainties with the prescribed probability level. Control costs and constraint violation can be reduced compared with deterministic model predictive control and open-loop control strategies.

Towards a transactive energy system for integration of distributed energy resources: Home energy management, distributed optimal power flow, and peer-to-peer energy trading

Smart grids have benefits such as high reliability and availability due to distributed energy resources (DERs) which are integrated to the power transmission and distribution grid. These DERs will maintain an uninterrupted power supply for electricity consumers in a case of isolation from the primary electricity grid due to failure of the system. The integration of DERs into the transmission and distribution grid introduces new consequence for distributed network operators (DNOs). In traditional electricity grid, power flow is happening normally from the bulk generation stations to consumers and all control operations are done at the centralized control station. In the modern electricity grid with DERs, the energy follows in both directions via substations due to randomly spread energy sources at the lower voltage side. Although distribution network was considered as a static system without major control operations or reconfiguration requirements. For a smart grid, distribution network can be considered as a dynamic system due to DERs. Power routing is an emerging concept. Its main purpose is to make the distribution network more flexible which will help to solve the technical issues related to DERs. With the introduction of DERs, DNOs have faced many challenges. Communication is one of major challenges in DNO Technology. Nowadays most of the communication architectures are based on the Internet that creates major security issues with the system. Cyber-security Enabled Communication Architecture is the most important concept for Power Routing. In this paper we introduce a cyber-security enabled communication architecture that facilitates the security for the information of an electricity grid.