Voltage Distribution Network Research Articles

Coordinated allocation of distributed generation, capacitor banks and soft open points in active distribution networks considering dispatching results

Distributed generation is being increasingly integrated into distribution networks. Controllable devices whose reactive power can be regulated, such as capacitor banks and soft open points, can be coordinately allocated to regulate the voltage of distribution networks to accommodate the high penetration of distributed generation. This paper proposes a coordinated optimal allocation method for distributed generation, capacitor banks and soft open points in active distribution networks. Time-sequence multistate models of renewable energies and loads are developed to obtain the operational scenarios of the active distribution networks and their probability of appearance in different periods. A bi-level programming model is established that embeds chance-constrained programming, in which the sitting and sizing of distributed generation, capacitor bank and soft open point are optimized in the upper level, whereas 24-hour dispatching is optimized in the lower level. Simulation results verify the proposed method.

Influence of Non-Sinusoidality of Voltage on Electricity Loss in Distribution Networks

The problem of electromagnetic compatibility in high-voltage distribution networks is considered, connected with the consumption of reactive power at the fundamental frequency and distortion of the current form in the feeding networks. The estimated indices of the calculation of power losses for non-sinusoidal supply voltage in the high-voltage distribution network for the PNS pump with a capacity of 50 MW are given. Methods for reducing the voltage non-sinusoidality.

A novel smart meter technique for voltage and current estimation in active distribution networks

For distribution network operators to make effective decisions about real-time applications, they should have complete knowledge of all system variables. However, measuring all variables is infeasible due to the large number of system buses and the consequently high cost of measurement devices. Network operators are thus in serious need of methods that can estimate system voltages and currents with only a few measuring devices. This paper presents a novel voltage, current, and power loss estimation technique for distribution networks characterized by a high level of distributed generation (DG) penetration. The proposed method is based on online measurements from smart meters (SMs) placed at a few selected locations in addition to the measurements from DGs production meters; the estimation is derived without any pseudo measurements. The ingenuity of the proposed technique is that the SM locations are dependent on the network topology only, which means that their locations remain unchanged regardless of penetration levels and/or DG injection points. The proposed technique also includes consideration of variations in X/R ratios and laterals. The developed algorithm was implemented and tested on three radial distribution feeders to show the capability of the proposed technique for estimation for balanced as well as unbalanced distribution networks. The results of a comparison with the actual load flow demonstrate the accuracy and effectiveness of the new technique.

Uncertainty Level of Voltage in Distribution Network: An Analysis Model With Elastic Net and Application in Storage Configuration

Quantitatively assessing the impact of uncertainties on node voltage in a distribution network is an important issue. This paper proposes a new model to analyze the uncertainty level of voltage from the perspective of the linear quantitative description with elastic net regression. To obtain the model parameters defined as the voltage influence coefficients, the procedures are as follows: first, estimate the expected values of node voltage by point-estimate method, and conduct the analysis sample collection; then determine the dominant factors and calculate their voltage influence coefficients for the above sample by elastic net regression. To further illustrate the practical application of the proposed model, a coordinated optimization configuration method for energy storage mounted on distributed generations is presented in detail. The verification results based on the modified IEEE 33-bus system and a modified practical 113-bus system demonstrate that the analysis model with elastic net has an excellent performance and is of high accuracy in assessing the influence of uncertainties on node voltage. Furthermore, the optimization results of multi-ESS for the test system illustrates that the proposed configuration method can produce a global and practical configuration scheme for the whole distribution system.

Distribution Network Voltage State Assessment with Distributed Generation Based on Improved Probabilistic Power Flow Method

Distribution Network Voltage State Assessment with Distributed Generation Based on Improved Probabilistic Power Flow Method

Voltage and reactive power control in distribution network considering optimal network configuration and voltage security constraints

In order to reduce energy losses and improve voltage stability index in distribution system, two different approaches have been proposed and employed including voltage and reactive power control (volt/var control) and distribution network reconfiguration. In the present paper, volt/var control and network reconfiguration in distribution system considering voltage security constraints is modelled as a multi-objective optimization problem. Total electrical energy losses, voltages deviations and voltage stability have been considered as objectives. Also, a new method for distribution network reconfiguration has been utilized for implementation of these two problems simultaneously. In this way, the two problems can be solved in less time. In addition, different nature of loads in each bus is considered in network load modelling. Non-dominated sorting genetic algorithm-II is used to solve this problem. Finally, the effectiveness of the proposed method is evaluated by implementation on the IEEE 33-bus system and a real 77-bus distribution system.

Distribution Network Voltage Control Based on Coordinated Optimization of PV and Air-Conditioning

This paper proposes a coordinated optimal control strategy of PV generators and air-conditioning loads, in order to handle the possible voltage beyond limit issues resulting from high penetration of PV generators in the distribution networks. This strategy is achieved via coordinately considering the node voltage sensitivity and the adjustment-compensation bid model, to improve the economy of the whole system. As a result, the shortage of the PVs’ reactive power control capability is compensated by the adjustable air-conditioning loads, so that the waste of the photovoltaic power can be reduced or even avoided. The case study using an IEEE standard 33-node system, which is further updated with the installation of 5 PV generators and 5 air-conditioning loads, validates the correctness and effectiveness of the proposed control strategy.

Reactive power and voltage control strategy based on dynamic and adaptive segment for DG inverter

The inverter of distributed generation (DG) can support reactive power to help solve the problem of out-of-limit voltage in active distribution network (ADN). Therefore, a reactive voltage control strategy based on dynamic and adaptive segment for DG inverter is put forward to actively control voltage in this paper. The proposed strategy adjusts the segmented voltage threshold of Q(U) droop curve dynamically and adaptively according to the voltage of grid-connected point and the power direction of adjacent downstream line. And then the reactive power reference of DG inverter can be got through modified Q(U) control strategy. The reactive power of inverter is controlled to trace the reference value. The proposed control strategy can not only control the local voltage of grid-connected point but also help to maintain voltage within qualified range considering the terminal voltage of distribution feeder and the reactive support for adjacent downstream DG. The scheme using the proposed strategy is compared with the scheme without the reactive support of DG inverter and the scheme using the Q(U) control strategy with constant segmented voltage threshold. The simulation results suggest that the proposed method has a significant improvement on solving the problem of out-of-limit voltage, restraining voltage variation and improving voltage quality.

Influence of Distributed Residential Energy Storage on Voltage in Rural Distribution Network and Capacity Configuration

Large-scale access of distributed residential photovoltaic (PV) in rural areas has solved the voltage problem to a certain extent. However, due to the intermittency of PV and the particularity of rural residents’ power load, the problem of low voltage in the evening peak remains to be resolved. This paper proposes to solve the problem by accessing residential energy storage. Firstly, the influence of access location and capacity of energy storage on voltage distribution in rural distribution network is analyzed. Secondly, the relation between the storage capacity and load capacity is deduced for four typical load and energy storage cases when the voltage deviation meets the demand. Finally, the optimal storage position and capacity are obtained by using PSO and power flow simulation.

Load forecasting for diurnal management of community battery systems

This paper compares three methods of load forecasting for the optimum management of community battery storages. These are distributed within the low voltage (LV) distribution network for voltage management, energy arbitrage or peak load reduction. The methods compared include: a neural network (NN) based prediction scheme that utilizes the load history and the current metrological conditions; a wavelet neural network (WNN) model which aims to separate the low and high frequency components of the consumer load and an artificial neural network and fuzzy inference system (ANFIS) approach. The batteries have limited capacity and have a significant operational cost. The load forecasts are used within a receding horizon optimization system that determines the state of charge (SOC) profile for a battery that minimizes a cost function based on energy supply and battery wear costs. Within the optimization system, the SOC daily profile is represented by a compact vector of Fourier series coefficients. The study is based upon data recorded within the Perth Solar City high penetration photovoltaic (PV) field trials. The trial studied 77 consumers with 29 rooftop solar systems that were connected in one LV network. Data were available from consumer smart meters and a data logger connected to the LV network supply transformer.

Research on Active Management Strategy of Distributed Power Supply Access to Distribution Network

With the wide access of distributed power supply, the planning and operation mode of distribution network becomes more and more complex, and the economy and the mode of supervision of distribution network have also been greatly affected. Based on the active management of distribution network fault management level, voltage control and power flow management (Active Management AM) technology, from the current, voltage and power loss are analyzed in terms of DG electrical characteristics, proposed to cut active, reactive power control and active management strategy of load transformer regulation. It has positive significance for model analysis and Strategy Research of distributed power supply access to distribution network, and has certain reference and application value.

Study of Non-Contact and Non-Ground Voltage Signal Measurement System in Medium Voltage

The measurement of current and voltage (as well as the indexes derived from them) in the electricity distribution network becomes more and more necessary in the present day. The power concessionaires seek to distribute to their customers, reliability and stability in the supply of this energy with admissible levels of quality established by the regulatory body of the electric system. In order to carry out a study of a signal measurement system without the need to disconnect medium voltage electrical conductors and without using a ground reference, the present work describes a methodology based on the analysis of the electric field generated by these Conductors to store energy and infer a voltage in a capacitor of parallel plates with certain characteristics, situated at a certain distance from them. With the use of computational simulation through software based on the Maxwell equations, it is possible to obtain values of the potential difference for systems with single-phase topology and to correlate it with the voltage that generated these electric fields. For a network with two-phase and three-phase topology, it was not possible to perform this correlation, however there is room to apply digital seeding techniques of sources with the purpose of discriminating the contribution of each phase in the sensor element.

Coordinated control for voltage regulation of distribution network voltage regulation by distributed energy storage systems

With more and more distributed photovoltaic (PV) plants access to the distribution system, whose structure is changing and becoming an active network. The traditional methods of voltage regulation may hardly adapt to this new situation. To address this problem, this paper presents a coordinated control method of distributed energy storage systems (DESSs) for voltage regulation in a distribution network. The influence of the voltage caused by the PV plant is analyzed in a simple distribution feeder at first. The voltage regulation areas corresponding to DESSs are divided by calculating and comparing the voltage sensitivity matrix. Then, a coordinated voltage control strategy is proposed for the DESSs. Finally, the simulation results of the IEEE 33-bus radial distribution network verify the effectiveness of the proposed coordinated control method.

A Distributed Voltage Control Strategy for Multi-Microgrid Active Distribution Networks Considering Economy and Response Speed

This paper presents a novel distributed voltage control strategy to maintain the voltage of active distribution networks containing multiple microgrids. Local voltage regulation characteristics, such as power reserve, adjustment cost, and regulating speed, are identified first. According to a neighbors’ voltage regulation characteristics, the microgrid coordinates neighborhood resources and asks them for coordination as soon as voltage problems occur. Microgrids schedule local resources based on a cooperative distributed model predictive control algorithm scheme with neighbor-to-neighbor communication. Tests are performed in an active distribution network with three microgrids. The numerical studies have shown that the proposed strategy mitigates the voltage fluctuation rapidly and efficiently with minimum operating cost.

Reactive Power Control of DGs for Distribution Network Voltage Regulation Using Multi-Agent System

Nowadays, with increase the installation of distributed generation (DG) sources in the distribution networks (DNs), the traditional voltage regulation devices with their conventional control abilities face several difficulties to solve the voltage regulation problems. The DG sources that have reactive power capability can greatly help to reduce the stress on the voltage regulation devices in DNs. This paper proposes an effective control strategy for voltage regulation in DNs with high DG penetration based on a multi-agent system (MAS). The proposed strategy is a simple and efficient method for managing the reactive power capability of various types of DG in DNs. The proposed control strategy utilizes voltage/reactive power sensitivity analysis to reduce the overall system voltage deviation. Comprehensive case studies on IEEE 33 test feeders are carried out to demonstrate the effectiveness of the control strategy. The numerical results show that the proposed strategy can significantly mitigate the voltage violation problems in a simple manner.

Performance of Electrical Power Distribution Network Under Dynamic Loading

This paper presents the performance of the electrical power distribution network under dynamic loading. The performance of a distribution system can be seen from the power losses generated by the network. If the power losses are low, then it can be said that network performance is excellent. Another parameter is the distribution network voltage profile. The voltage profile is significant in the distribution network. A very long distribution line will cause a voltage drop at the end of the network. This condition is very undesirable, so efforts must be made to improve the distribution network voltage profile. The method for correcting the voltage profile is by installing capacitors or reconfiguring the network. In this study, an evaluation of the performance of the distribution network at PLN Temanggung was conducted. The results showed that several network points experienced below-standard voltage drops. Therefore it is recommended to install power capacitors or reconfigure the networks.

A Novel Multi-Parallel Power Frequency Communication Technology

Power line frequency communication technology using the small distortion about the grid voltage and current waveform to carry information, and cross the transformer remote communication, suitable for line structure and load characteristics in distribution network. It has the advantages of low cost, easy installation, free communication and so on. But the power line frequency communication there is a low rate of defects, and the traditional modulation and demodulation are based on the local voltage zero, because the transceiver system voltage phase difference caused by receiving time domain deviation, which seriously affect the communication performance. This paper established a multi-channel signal transmission model based on the technical mechanism of frequency communication. We use single-phase multi-channel, three-phase transmission, multi-feeder parallel transmission and other means to improve the communication rate, At the same time, this paper based on time-frequency analysis to determine the frequency domain communication signal modulation time domain, combined with a variety of anti-jamming measures, which can adapt to the distribution network voltage difference between nodes, thereby enhancing communication performance.

Investigation of the voltage quality at PCC of grid connected PV system

In this paper, we present and discuss the behavior of the voltage in the Algerian Low-Voltage distribution network and the influence of the PV generation. This intermittent availability characteristic will have a local impact on the power quality. Hence, a statistical analysis of the voltage characteristics is shows to evaluation the grid at Point of Common Coupling (PCC) according to the EN 50160 and IEC 61000-2-2 standards. The voltage variation, unbalance, flicker severity, total and individual harmonic are presented. It has been found that the voltage at the PCC is in accordance with standards requirement.

Optimal Allocation of Distributed Generation Based on Adaptive Genetic Algorithm

Distributed generation (DG) has attracted extensive attention for the emergence of new energy, environmental protection requirements, and flexible and reliable. The addition of DG will have a great impact on the loss and voltage of distribution network .This paper changes the traditional way which makes the optimal power flow, voltage deviation minimum as target, using genetic algorithm, having large data theory to generate fault .When random failure occurred, with the islanding effect of DG, making the minimum economic loss caused by the lack of power supply as the objective function, to optimize the configuration of DG from the viewpoint of reliability, proven to reduce the economic losses significantly.

Self-healing reconfiguration scheme for distribution network with distributed generations based on multi-agent systems

More and more distributed generations are connected in the distribution network. Intermittent output and different locations have a significant impact to the distribution network voltage, current, power flow, the traditional forward and backward substitution is unable to solve PV-type node and meshed network, the distributed generations increase the number of network constraints and increase the difficulty of searching the optimal solution. To solve the problem of classic self-healing method failure, based on the multi-agent system, a novel self-healing reconfiguration scheme is proposed for distribution network with distributed generations in this study. Multiple objectives are considered for minimum distributed generation output loss, minimum power loss, load balancing among the feeders and branch current constraint violation, improved forward-backward weep method is used to get power flow solution for different node types of distributed generations, a self-adaptive differential evolution algorithm with improved strategies is proposed to solve problem. The performance of proposed algorithm is analyzed for several case studies on IEEE 33-bus system. The simulation results show that the approach can improve the self-healing reconfiguration performance and adapt to the changes of dynamic conditions.