Optimization of Active Distribution Network Operation with SOP Considering Reverse Power Flow

Because more distribution generations are added to the distribution network, the power flow of the distribution network is changed. The analysis and Research on the power flow of distribution network with distributed generation is an important means to analyze the influence of distributed generation on distribution network. First, Newton-Raphson algorithm is applyed to calculate the power flow of the distribution network with distributed generation. Then the optimal power flow model of the distribution network is set up based on the objective function of the minimum loss in the network. Finally, the optimization problem is solved by using the improved particle swarm optimization algorithm. The simulation is tested and verified by using IEEE14 node system in the MATLAB software. The test results show that the optimal power flow research on distribution network with distributed generation can reduce the loss of the network and improve the economy of the system.

Aiming at the problem of imbalance load of feeder lines and reverse photovoltaic power flow in distribution network, the flexible interconnection scheme based on full-power converter is the key to realize intelligent control of distribution network. In this paper, a power control strategy for flexible interconnection system is proposed, which including heavy-load limiting control for the rational power distribution when some feeder lines are heavy-loaded, and power balance control for that all feeders are heavy-loaded to relieve the power supply pressure of flexible interconnection devices (FIDs). Case study based on real load data verifies that the proposed strategy can cope with different seasonal distribution network scenarios with different load characteristics and different degrees of reverse photovoltaic power flow. The proposed can suppress forward and reverse heavy load flow, and improve the power supply safety and efficiency of the distribution network.

With rapid increase in wind power penetration into the power grid, unbalanced power flow in distribution network with distributed generators is becoming increasingly important to power sysytem. Due to the variability and uncertainty of wind, such traditional unbalanced power flow analysis method for distributed power supply limit the use of the existing tools for decision-making under uncertain conditions. As a result, unbalanced power flow analysis method, which provides information on uncertainty associated with wind power analysis, is gaining increased attention. This paper presents a novel hybrid intelligent algorithm for deterministic unbalanced power flow in distribution network with distributed generators that utilizes a combination of Cauchy particle swarm optimization(CPSO) and fuzzy ARTMAP (FA) network, which is optimized by using PSD-BPA. The performance of the proposed model is assessed utilizing wind power data from the Baolihua wind farm in Southern China. Unbalanced power flow in distribution network with distributed generators is researched. The typical static load model is established and the impact of distributed generators on feeder voltage profile is analyzed under unbalanced loads. The simulation results are given. References for the global planning of unbalance compensation in distribution network can be provided by the study.

The proliferation of distributed generation (DG) poses new challenges in management of voltages in distribution networks. Excess generation by DG systems can cause voltage rise and reverse power flows, changing the paradigm of unidirectional power flow in distribution networks. Among many mitigation strategies, volt/var control methods that utilise inverter-interfaced DG systems to rectify voltage issues would be beneficial not only because DG system are typically located closer to customers, but the inverters can also provide fast response in contrast to mechanically operating volt/var control devices. As yet, DG owners only generate revenues from the production of active power while no incentives are provided for reactive power import/export, signifying the need for an update in the market structure to follow the growth of inverter-interfaced DG systems in distribution networks. This paper aims to propose an economic incentive scheme for utilising the full capacity of photovoltaic (PV) systems in Australian distribution networks. A ‘lost opportunity’ market structure that considers non-unity power factor operation of PV inverters in volt/var control strategies is proposed. The results show that the proposed market structure can encourage participation of domestic PV systems in volt/var control by providing a win-win solution for all stakeholders in a distribution network.

Recently, the integration of distributed generation (DG) into distribution networks has grown significantly. As a result of this integration, optimal power flow (OPF) can be applied to the distribution network as an effective tool in order to enhance the control, operation and planning in the distribution grid. The nonlinearity of OPF problem in distribution networks requires the application of nonlinear optimization methods. This paper investigates how high penetration photovoltaic (PV) units impact the voltage regulation and power flow in active distribution networks. A multi-objective function is used to define the nonlinear power flow problem and Cuckoo Search (CS) algorithm is applied to solve the OPF problem. The proposed method was tested by using IEEE 123 nodes test case. Comparing the results of the PV unit with the traditional operation methods shows that locating PV units in the unbalanced distribution system would lead to better performance.

It is less intelligent to calculate the closed-loop power flow of the distribution network by manually inputting the closed-loop power flow parameters. Therefore, it is necessary to study the real-time calculation method of the loop power flow in the distribution network. In this paper, a real-time calculation method is put forward based on the Thévenin’s Theorem. Forward/backward sweep algorithm is used to calculate the power flow of the closed-loop distribution network with the aid of the equivalent impedance and the maximum inrush current. A real-time automatic analysis tool for the closed-loop power flow is developed as well, based on the autonomous decentralized concept. The closed-loop power flow calculation is embedded in the DSCADA system to evaluate the feasibility of the loop-closing operation. Test results show that the proposed method can effectively identify the limit violation conditions within the distribution network, and that the calculation error in closed-loop power flow is small.

Reverse Power Flow in Distribution Networks: Impacts, Challenges, Issues, and Technologies

Volt/Var Optimization (VVO) function is a key element in operation of distribution networks and major part of advanced Distribution Management Systems (DMS). From planning prospective, VVO function can be used to optimize reactive power flow in distribution network to recommend the best operating condition for the control equipment in a predefined period of time in future (i.e. 24 hour). In fact VVO minimizes the total system loss for a forecasted set of load and computes the optimized setting for transformer on-load tap changers (OLTC), Voltage Regulators (VR), and Capacitor Banks (CB), while system voltage profile is maintained within its limits. In this paper we use a full mixed integer linear programming (MILP) model for solving VVO problem for a planning application. The objective of this paper is to develop a planning VVO engine which can calculate the most probable expected loss of the network for the next 24 hours, and can recommend the best expected operating condition for the control equipment. To model the uncertainty of load, an ARMA model is applied to create several forecasted load scenarios to feed them into the VVO engine (which is implemented in a commercial solver GAMS (General Algebraic Modeling System). The implemented models have been tested on a real distribution network in southern Sweden and results are presented.

Volt/VAR Optimization (VVO) function is an important element in real time operation of distribution networks and major part of advanced Distribution Management Systems (DMS). From planning prospective, VVO function can be used to optimize reactive power flow in distribution network to recommend the best operating condition for the control equipment in a predefined period of time in future (i.e. 24 hour). The typical objective function of VVO functions are minimizing the total system loss for a certain system load level. VVO function computes the optimized setting for transformer on-load tap changers (OLTC), Voltage Regulators (VR), and Capacitor Banks, while system voltage profile is maintained within its limits. In this paper the objective is to develop a planning VVO engine which can calculate the most probable expected loss of the network for the next 24 hours, and can recommend the best expected operating condition for the control equipment. For the VVO algorithm a full mixed integer linear programming (MILP) model is used to solve the loss objective of VVO problem for a planning application. The load uncertainty is modeled by an ARMA model which can create any arbitrary number of forecasted load scenarios to be used by VVO engine (implemented in a commercial solver GAMS, “General Algebraic Modeling System”). The implemented models have been tested on a real distribution network in southern Sweden and the results are presented.

In order to meet the demand of prosumer for power quality and new load in distribution network, an open capacity expansion model of distribution network with mobile energy storage system (MESS) is proposed in this paper. The model gives priority to the problem of voltage violation of prosumer group on feeders. Combined with the mobile energy storage path model, the open capacity of distribution network is calculated. Firstly, the actual distribution network geographic information and traffic routes are combined to establish the distribution network model based on mesh generation. Secondly, the traffic route model of the mobile energy storage system is established on the distribution network model based on mesh generation. Then, the optimal power flow of distribution network is calculated with the optimal network loss, and the mobile energy storage system is scheduled according to the situation of voltage violation. And the specific vehicle model and its scheduling are determined, which can better deal with the problem of distributed energy consumption and make prosumer operate safely and economically. Finally, according to the proposed N-1 security check constraint of distribution network with mobile energy storage system, the maximum open capacity of distribution network is calculated after the voltage regulation is completed. The example shows the practicability and correctness of the model in this paper. This paper formulates a mobile energy storage operation strategy to improve the open capacity of distribution network. The strategy not only fully meets users' needs, but also better guides the operation of power grid. It is conducive to releasing more potential power supply space of distribution network and improving asset utilization.

In the current distribution network’s energy structure, photovoltaic (PV) occupies a high proportion. However, the access of a high proportion of PV will lead to the phenomenon of reverse power flow in the distribution network, and then the problem of line overvoltage. When the reverse power flow increases, the problem of line overvoltage also worsens, which endangers the normal operation of power system. To solve this problem, this paper starts with the voltage rise theory of distribution network lines. Firstly, through strict mathematical derivation, it compares the influence of main network line parameters and distribution network line parameters on the voltage rise, and summarizes a simple calculation equation for the voltage rise of the distribution network with high proportion PV. Then, according to the mechanism of voltage rise and the principle of inverter control, considering the economy and practicability of the overvoltage suppression strategy, a reverse power flow overvoltage suppression strategy of a system with high proportion PV is proposed. Finally, a PV system model simulating a small village is used to verify the effectiveness of the proposed overvoltage suppression strategy.

The penetration level of renewable energy (RE) including distributed generation (DG) integrated in the distribution network has been increasing in many countries. This follows widespread encouragement to use renewable energy to minimize reliance on conventional power plants to achieve net zero emissions. Malaysian energy transition targets and carbon neutral goals set by the government, lower cost of ownership of solar PV systems, and more efficient government renewable energy initiatives including Net Energy Metering (NEM) 3.0, Green Investment Tax (GITA), Large Scale Solar (LSS), and most recently the Corporate Green Power Program (CGPP) have driven the rapid development of renewable energy in the country. However, the high penetration level of distributed generation including solar PV, mini- hydro, and bio-energy has introduced several technical impacts on the operation of the distribution network including increased fault levels, voltage limit violation, reverse power flow, distribution network losses, and transformer losses. This paper analyzes the technical impacts of the high penetration level of distributed generation in medium voltage (MV) substations of the distribution network using DigSILENT PowerFactory simulation software. From the results obtained through the simulation analysis, the impact factors of fault level, voltage limit violations, reverse power flow, distribution network losses, and transformer losses have been formulated. The optimal distributed generation penetration level in distribution networks is then determined based on the highest score value of the normalized impact factor from all penetration levels.

Driven by the goal of carbon peaking and carbon neutralization, the development of green energy has experienced a blowout growth. The problems such as reverse power flow and voltage quality of distribution network caused by the grid connection of a large number of distributed energy have brought many challenges to the safe and stable operation of large power grid, which has seriously affected and limited the development of distributed energy. In order to solve the problems of economic consumption and efficient utilization of a large-scale distributed energy and reduce the negative impact of large-scale distributed energy connection to power grid, this paper analyzes and studies the cluster control technology of large-scale distributed energy. Firstly, it analyzes the problems and challenges faced by large-scale power grid, distribution network, energy aggregators and power load terminal under the large-scale grid connection of distributed energy; Secondly, according to the different control demands of power grid companies and energy aggregators, different distributed energy cluster control solutions are given. The solutions deeply analyze the Data Acquisition scheme, control architecture and cluster division principle of cluster control, then introduce the application case of Xiangtan distributed energy management and control project. Finally the paper summarize and point out the development direction of cluster control system in the future.

This paper proposes a sufficient condition for the convex relaxation of ac optimal power flow (OPF) in radial distribution networks as a second order cone program (SOCP) to be exact. The condition requires that the allowed reverse power flow is only reactive or active, or none. Under the proposed sufficient condition, the feasible sub-injection region (power injections of nodes excluding the root node) of the ac OPF is convex. The exactness of the convex relaxation under the proposed cond $\bar{s}$ ition is proved through constructing a group of monotonic series with limits, which ensures that the optimal solution of the SOCP can be converted to an optimal solution of the original ac OPF. The efficacy of the convex relaxation to solve the ac OPF is demonstrated by case studies of an optimal multi-period planning problem of electric vehicles in distribution networks.

Due to environmental and fuel cost concerns more and more wind- and solar-based generation units are embedded in distribution networks (DNs). However, a part of such an embedded generation would be curtailed due to system constraints and variations of the energy penetration. This part of energy can be recovered by introducing energy storage systems (ESSs) and an optimal dispatch of both active and reactive powers. Therefore, we propose a combined problem formulation for active-reactive optimal power flow (A-R-OPF) in DNs with embedded wind generation and battery storage. The solution provides an optimal operation strategy which ensures the feasibility and enhances the profit significantly. Results of a 41-bus distribution network are presented. It can be demonstrated that more than 12% of energy losses and a large amount of reactive energy to be imported from the transmission network (TN) can be reduced using the proposed approach in comparison to the operation strategy where only active OPF is considered.