Voltage Test System Research Articles

Three‐phase four‐wire power flow solution for multi‐grounded distribution networks with non‐bolted grounding

AbstractThis study proposes a direct three‐phase four‐wire power flow method to accurately analyse the neutral line and multiple grounding characteristics. In particular, the proposed grounding impedance building‐based solution method was used to analyse the neutral grounding impedance in power flow studies based on the slack bus grounding impedance. The accuracy of the proposed method was verified using a neutral‐to‐earth voltage test system. IEEE 13‐bus and 123‐bus test systems were used to compare the advantages and disadvantages of the proposed method. Compared to the current injection full Newton and forward–backward sweep methods, the proposed method achieves a significant reduction in iteration numbers of up to 76.92% and 77.78%, respectively. For different grounding scenarios, stable convergence characteristics were exhibited by the proposed method after six to seven iterations.

An Extra-High Voltage Test System for Transmission Expansion Planning Studies Considering Single Contingency Conditions

This paper presents an extra-high voltage synthetic test system that consists of 500 kV and 765 kV voltage levels, specifically designed for transmission expansion planning (TEP) studies. The test network includes long transmission lines whose series impedance and shunt admittance are calculated using the equivalent π circuit model, accurately reflecting the distributed nature of the line parameters. The proposed test system offers technically feasible steady-state operation under normal and all single contingency conditions. By incorporating accurate modeling for long transmission lines and EHV voltage levels, the test system provides a realistic platform for validating models and theories prior to their application in actual power systems. It supports testing new algorithms, control strategies, and grid management techniques, aids in transmission expansion planning and investment decisions, and facilitates comprehensive grid evaluations. Moreover, a TEP study is conducted on this test system and various scenarios are evaluated and compared economically.

Experimental study on the influence of rock pore structure on pressure stimulated voltage variations based on nuclear magnetic resonance

Since rocks will generate voltage under load, studying their voltage characteristics is of prime importance for the prevention and control of mine dynamic disasters and the corresponding secondary disasters. In this study, a pressure stimulated voltage (PSV) test system for rock materials under uniaxial compression was constructed to explore the law of PSV variations of rocks. Meanwhile, a nuclear magnetic resonance test system was employed for investigating the influence mechanism of pore structure changes on PSV variations. The following beneficial results were obtained. A “double-peak” phenomenon is observed on the PSV curves of granite and sandstone, whereas, for marble, the phenomenon only appears under high loading rates. The T2 spectra of different types of rock differ greatly. After granite fractures under load, some primary micro-pores are converted into meso-pores and macro-pores, accompanied by the generation of substantial new micro-pores. These micro-pores activate more rock defects (dislocation and grain boundary), resulting in a higher average PSV and peak PSV. After marble fractures, numerous primary micro-pores are transformed into meso-pores and macro-pores, and the proportion of new micro-pores falls. Consequently, its electricity generation capacity weakens. In contrast, sandstone contains a higher proportion of micro-pores. After it fractures, despite the conversion of some micro-pores into meso-pores and macro-pores, abundant micro-pores are generated again, bringing about a relatively high voltage. In short, the changes in overall porosity cannot represent the electricity generation capacity of rock, and the changes in bound cracks exert a profoundly influence on it. The key to the electricity generation capacity of rock lies in the increase and connection of micro-cracks.

Statistical analysis of PV penetration impact on residential distribution grids

This paper presents a comprehensive approach to the probabilistic analysis of residential distribution grid injected by distributed PV sources. The approach is data-driven and is able to deal with the general scenario that includes the uncertainty of correlated PV sources and of statistically independent consumer loads. The novel method adopts a Gaussian-Mixture-Model for correctly representing PV sources correlation and a fresh probabilistic analysis technique employing Multi-Expansion polynomial chaos. Numerical experiments carried out on the Non-Synthetic European low voltage test system, highlight the importance of the comprehensive modeling strategy in order to realistically quantify uncertainty impact on the grid.

Local voltage control in distribution networks using PI control of active and reactive power

Overvoltage is becoming increasingly prevalent in distribution networks with high penetration of renewable distributed energy sources (DERs). Local control of converter-based resources is a flexible and scalable method to prevent this growing issue. Reactive power is used for voltage control in many local control schemes. However, the typical range of R/X ratios for distribution power lines indicates that mitigation of overvoltage often requires excessive amounts of reactive power. Complete reliance on reactive power thus limits the effectiveness of local control strategies. In this work we instead propose a method that combines enhanced power factor voltage control with upper voltage limit tracking using PI control. We develop a modelling framework and demonstrate the stability of the proposed method. We then simulate the nonlinear operation of two parallel PI controllers in a medium voltage test system.

Survey and Comparison of Optimization-Based Aggregation Methods for the Determination of the Flexibility Potentials at Vertical System Interconnections

The aggregation of operational active and reactive power flexibilities as the feasible operation region (FOR) is a main component of a hierarchical multi-voltage-level grid control as well as the cooperation of transmission and distribution system operators at vertical system interconnections. This article presents a new optimization-based aggregation approach, based on a modified particle swarm optimization (PSO) and compares it to non-linear and linear programming. The approach is to combine the advantages of stochastic and optimization-based methods to achieve an appropriate aggregation of flexibilities while obtaining additional meta information during the iterative solution process. The general principles for sampling an FOR are introduced in a survey of aggregation methods from the literature and the adaptation of the classic optimal power flow problem. The investigations are based on simulations of the Cigré medium voltage test system and are divided into three parts. The improvement of the classic PSO algorithm regarding the determination of the FOR are presented. The most suitable of four sampling strategies from the literature is identified and selected for the comparison of the optimization methods. The analysis of the results reveals a better performance of the modified PSO in sampling the FOR compared to the other optimization methods.

Distribution Locational Marginal Pricing by Convexified ACOPF and Hierarchical Dispatch

This paper proposes a hierarchical economic dispatch (HED) mechanism for computing distribution locational marginal prices (DLMPs). The HED mechanism involves three levels: 1) the top level is the national (regional) transmission network; 2) the middle level is the distribution network; and while 3) the lowest level reflects local embedded networks or microgrids. Each network operator communicates its generalized bid functions (GBFs) to the next higher level of the hierarchy. The GBFs approximate the true cost function of a network by a series of affine functions. The concept of Benders cuts are employed in simulating the GBFs. The ac optimal power flow (ACOPF) is convexified and then used for dispatching generators and calculating GBFs and DLMPs. The proposed convexification is based on the second order cone reformulation. A sequential optimization algorithm is developed to tighten the proposed second order cone relaxation of ACOPF. The properties of the sequential tightness algorithm are discussed and proved. The HED is implemented in the GAMS grid computing platform. The GBFs and DLMPs are calculated for the modified IEEE 342 node low voltage test system. The numerical results show the utility of the proposed HED and GBF in implementing DLMP.

Development of a Novel 30 kV Solid-state Switch for Damped Oscillating Voltage Testing System

This paper describes the design and development of a novel semiconductor-based solid-state switch for damped oscillating voltage test system. The proposed switch is configured as two identical series-connected switch stacks, each of which comprising 10 series-connected IGBT function units. Each unit consists of one IGBT, a gate driver, and an auxiliary voltage sharing circuit. A single switch stack can block 20 kV-rated high voltage, and two stacks in series are proven applicable to 30 kV-rated high voltage. The turn-on speed of the switch is approximately 250 ns. A flyback topology-based power supply system with a front-end power factor correction is built for the drive circuit by loosely inductively coupling each unit with a ferrite core to the primary side of a power generator to obtain the advantages of galvanic isolation and compact size. After the simulation, measurement, and estimation of the parasitic effect on the gate driver, a prototype is assembled and tested under different operating regimes. Experimental results are presented to demonstrate the performance of the developed prototype.

Experimental Study on Effect of Contamination on Electric Field Distribution of 330kV Composite Insulator

330kV transmission line in the northwest region of China is much complex while pollution flashover is a major threat to the safe operation of the system. In this paper, experimental study on effect of contamination on electric field distribution of 330kV composite insulator is presented. High voltage test system of 330kV composite insulator is established according to the ratio of 1:1. Surface electric field and potential of the insulator is measured using GDC-100 optical fiber voltage electric field measuring instrument. Potential, electric field distribution of the two kinds of 330kV composite insulator are tested in different environment of clean, dry and uniform pollution layer. The test and simulation result is also compared.

Domain structure of ferroelectric ceramics

PZT ceramics were statically and dynamically evaluated to examine the relationship between domain structures and electrical properties. We investigated the domain structures of tetragonal, M.P.B. and rhombohedral PZT ceramics at various poling fields to measure the poling field dependence of the crystal orientations and electrical properties as a statical evaluation. Furthermore, responses to repeated voltage pulses applied to the ceramics were measured by a high voltage test system as a dynamical evaluation. Through these evaluations, we could clarify the domain behavior for the 90° (71° or 109°) domain rotation, switching and clamping of 180° domain, and transient phenomena on the domain orientation.

Pulse response measurement of transient phenomena on ferroelectric domains in PZT ceramics

Lead zirconate titanate ceramics were evaluated to examine the relationship between domain structures and ferroelectric properties. Responses to repeated voltage pulses applied to the ceramics were measured by a high voltage test system as a dynamical evaluation. Through the evaluation, it was clarified the domain behavior for the 90° (71° and 109°) domain rotation, 180° domain switching and clamping, and transient phenomena on the domain orientation.

Poling Field Dependence of Ferroelectric Properties and Crystal Orientation in Rhombohedral Lead Zirconate Titanate Ceramics

Rhombohedral lead zirconate titanate (PZT) ceramics were evaluated statically and dynamically to examine the relationship between domain structures and electrical properties. The poling field dependence of the electrical properties and crystal orientation was investigated as a statical evaluation. When the poling field was varied, maximum dielectric constant, minimum planar coupling factor, minimum frequency constant and minimum relative intensity of the X-ray diffraction (222) peak were obtained at the poling fields of ±0.5, ±1.0, ±0.5 and ±0.75 kV/mm, respectively. Since 180° domain switching was the dominant factor affecting the coupling factor, it was thought that the electrical domain clamping occurred at ±1.0 kV/mm. Furthermore, responses to repeated voltage pulses applied to the ceramics were measured by a high voltage test system as a dynamical evaluation. From these evaluations, we could clarify the domain behavior for the switching and clamping of 180° domain, 71° and 109° domain rotations and transient phenomena on the domain orientation.