Voltage and reactive power control via inverter-based distributed generators (DGs) is necessary for distribution networks to mitigate voltage violations. This article presents an accelerated alternating direction method of multiplier (ADMM)-based reactive power optimization algorithm in a fully distributed manner. In the proposed method, each area optimizes its own subproblem with limited boundary information communicating with neighbors to protect information privacy. Based on the distributed quasi-Newton technique, the second-order curvature of the dual function is estimated and applied to improve the convergence property of the ADMM. Simulation results have verified the effectiveness of the proposed method compared with other gradient-based methods, such as ADMM and dual decomposition. The proposed acceleration strategy can also be extended to other gradient-based distributed optimization in power systems.

Accelerated ADMM-Based Fully Distributed Inverter-Based Volt/Var Control Strategy for Active Distribution Networks

This paper presents a fully distributed algorithm for the stochastic Volt/VAr control (VVC) problem in active distribution networks. Exact convexification of the VVC problem is achieved through the use of second-order cones on the continuous relaxation of the original optimization structure. The global optimum solution of the relaxed problem is obtained through the application of the alternating direction method of multipliers (ADMM). In order to minimize the effect of rounding off on the final solution, an adaptive threshold discretization technique is used. A two-stage control strategy is adopted where the discrete controllers, like load tap changers and switched capacitors, are dispatched at the beginning of the optimization interval and the continuous controllers, like distributed generation (DG) inverters, are adjusted in real time according to an optimized decision rule. The superiority of the proposed algorithm is demonstrated through numerical simulations on the UKGDS-95 and the IEEE-123 bus systems.

Distributed Solution of Stochastic Volt/VAr Control in Radial Networks

This article addresses the problem of optimizing voltage profiles in distribution networks. The voltage optimization is split into two stages; the former is performed offline and the latter online. First, the network is partitioned into several weakly coupled voltage control zones (VCZs) with pilot nodes (PNs). Then, the partitioning is used to optimize the voltage profiles of the distribution systems on the frame of a two time-scale-based coordinated approach. At the first level, a centralized voltage optimization problem (VOP), minimizing the distance of bus voltages at the PNs from their reference values and subject to linearized power flow equations, is solved to fix the positions of the on-load tap changer and of step-voltage regulators, and the reactive powers provided by capacitor banks. At the second level, the VOP is implemented according to a decentralized approach, in which the solution is obtained by applying a distributed algorithm based on the alternating direction method of multipliers. It optimizes in each VCZ the voltage at the PN by acting on the active and reactive powers provided by the distributed energy resources present in the VCZ; the VCZ solutions are driven to the global optimum of the whole distribution system by a limited data exchange between the PNs. The proposed approach reduces the complexity and computational burden typical when solving the VOP on a large scale system. The proposed strategy is tested on the modified IEEE 123-bus system; various load and generation scenarios are analyzed proving the effectiveness of the proposed approach in achieving the objective of voltage regulation. 

Coordinated Optimization for Zone-Based Voltage Control in Distribution Grids

With a high proportion of renewable distributed generation and time-varying load connected to the distribution network, great challenges have appeared in the reactive power optimization control of the active distribution networks. This paper first introduces the characteristics of active distribution networks, the mechanism and research status of wind power, photovoltaic, and other renewable distributed generators, and time-varying loads participating in reactive power and voltage optimization. Then, the paper summarizes the methods of reactive power optimization and voltage regulation of active distribution network, including multi-timescale voltage optimization, coordinated optimization of network reconfiguration and reactive power optimization, coordinated optimization of active and reactive power optimization based on model predictive control, hierarchical and zoning control of reactive power, and voltage and power electronic switch voltage regulation. The pros and cons of the reactive power optimization algorithms mentioned above are summarized. Finally, combined with the development trend of the energy Internet, the future directions of reactive power and voltage control technology in the active distribution network are discussed.

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Review on Reactive Power and Voltage Optimization of Active Distribution Network with Renewable Distributed Generation and Time-Varying Loads

Nowadays, the energy storage system (ESS) deployment is a promising solution for various perspectives of grid support. In particular, photovoltaic (PV) penetration is being increased rapidly in a present distribution network, causing voltage variation and violation issues. Hence, ESS has widely been utilized to mitigate voltage issues in distribution networks. This paper presents a study on the management of state of charge (SoC) of ESS for voltage regulation application in distribution networks. The voltage regulation strategy is proposed incorporating with SoC management. The SoC management strategy is applied to maintain the SoC of ESS within the desired value. In this paper, the SoC management issue has been investigated and analyzed by DIgSILENT Powerfactory software, according to the technical limitations of ESS. The simulation results show that the ESS requires appropriate SoC management to maintain simultaneously both aspects associated with the capability for voltage regulation and its energy availability.

A Study on SoC Management of Energy Storage System for Voltage Regulation Application in Distribution Network

With the increasing penetration of distributed photovoltaics (PVs), the operation and control of distribution networks (DNs), especially voltage control, have become more complicated. To deal with the voltage violation problem caused by large-scale PV access, this paper presents a fully distributed optimization method that combines the alternative direction multiplier method (ADMM) with the branch and bound method (BBM) for regional DNs. The total cost of active power losses and PV generation losses is minimized by making full use of the voltage regulation resources, e.g., reactive power compensators, step voltage regulators (SVR), and PV inverters, and the ADMM is employed to realize the intra-regional optimization and inter-regional coordination. To overcome the non-convex problem that is introduced by the SVR, the constraints of real-value tap positions are reformulated as linear inequality constraints of boundary voltages and added to the original problem, then the integer optimal solutions of SVR tap positions are obtained by BBM. The effectiveness of the proposed method is verified via numerical simulations on a practical 32-bus DN in China and a modified IEEE123-bus system.

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A Fully Distributed Voltage Optimization Method for Distribution Networks Considering Integer Constraints of Step Voltage Regulators

The invention relates to a scene analysis method and considerable voltage adjustment strategy based distributed photovoltaic optimization planning method. The method comprises the steps of 1, carrying out scene analysis by utilizing the scene analysis method, adopting a high-dimensional vector to represent the real running states of a distributed power source and a load, and realizing scene compression through a clustering method; and 2, building a distribution network distributed power source double-layer optimization planning method, wherein the step 2 comprises the sub-steps of (1) planning to build multiple targets by using minimum network damage of a distribution network and the maximum profits of a distributed power source operator at the upper layer, and planning the access capacity of the distributed power source; and (2) adopting different scheduling strategies in a scheduling model in the lower layer, comparing unused voltage adjustment strategies, the adopted voltage adjustment strategy and a voltage adjustment strategy with reactive compensation, and planning the distributed power source.

Network topology identification based high-permeability photovoltaic distributed voltage control method

The invention relates to a distributed photovoltaic cluster classification method based on a modular index. The method comprises the steps of: calculating the electrical distance between nodes; calculating an adjacent matrix between the nodes; calculating the degree of the nodes; calculating the modular index; calculating the solving ability of reactive power resources in clusters on overvoltage; calculating the solving ability of stored energy in the clusters on remaining overvoltage; calculating the solving ability of photovoltaic in the clusters on the remaining overvoltage; calculating a cluster voltage adjusting ability index; calculating a comprehensive performance index of distributed photovoltaic power generation clusters based on the modular index and the regional voltage adjusting ability; and performing cluster classification according to the indexes.

Xu Bin

Papers

A Fully Distributed Voltage Optimization Method for Distribution Networks Considering Integer Constraints of Step Voltage Regulators

Network topology identification based high-permeability photovoltaic distributed voltage control method

Distributed photovoltaic cluster classification method based on modular index