Bus Voltage Change Research Articles

Particle Swarm Optimization for Directional Overcurrent Relay Coordination with Distributed Generation

The Directional Overcurrent Relays (DOCRs) Coordination with Distributed Generation (DG) optimization problem is addressed in this study using the optimization method Particle Swarm Optimization (PSO). Changes in fault current, bus voltages, power flow, and reliability may result from DG integration. Thus, it might have an impact on the current protection coordination system. The formulation is built on a Mixed Integer Non-Linear Programming (MINLP) problem to address this DOCR issue. MATLAB was used to validate the technique on the IEEE-14 bus system, and Electrical Test Transient Analyzer Programming (ETAP) version 2021 software was used to model the test system. According to the simulation results, the suggested PSO with DG for Case 2 has reduced power loss by 6.24% and relay operating time by 46.79% when compared to PSO without the presence of DG.

Design of Dynamic Voltage Restorer for Power Quality Improvement

Solutions for customers with delicate loads and quick voltage regulation are essential. Protect important loads from supply-side voltage disturbances with a power electronic converter-based Dynamic Voltage Restorer (DVR). In the case of severe sag and swell, DVR is a well-known, low-cost therapy option. On the basis of its maximum voltage injection and active power contribution, a DVR's mitigation ability is determined. Standard DVRs use batteries as their DC input, but batteries are cumbersome, expensive, and hazardous to dispose of after they've been used. This limits compensation for DVRs. It is recommended to increase the DVR's VA rating by 1.5 times by increasing the DC connection voltage to 1.5 times the micro grid voltage regulation and quality improvement methods are proposed in this study. As a series voltage compensator, these solutions incorporate a Dynamic Voltage Restorer (DVR) for regulation, quality improvement, and reduction of harmonic distortion. Continuous adjustment of the DVR output voltage is proposed to reduce harmonic distortions while minimizing network bus voltage changes. As a result of this strategy, the peak demand voltage loss is compensated for. In constant impedance loads, voltage rise reduces network demand, resulting in lower branch currents and losses

Joint Detection and State Estimate with GSAs in PMU-Based Smart Grids

The Phasor Measurement Unit (PMU) with a GPS signal receiver is a synchronized sensor widely used for power system state estimation. While the GPS receiver ensures time accuracy, it is vulnerable to network attacks. GPS spoofing attacks can alter the phase angle of PMU measurement signals and manipulate system states. This paper derives a power system state model based on PMUs under GPS spoofing attacks, according to the characteristics of changes in bus voltages and branch currents after GSA. Based on the characteristics of this model, a detection and correction algorithm for attacked data is proposed to detect GSA and correct attacked measurements. The corrected measurements can be used for power system state estimation. Simulation results on the IEEE 14-bus system show that the proposed algorithm improves the accuracy of state estimation under one or multiple GSAs, especially when multiple GSAs are present, compared to classical Weighted Least Squares Estimation (WLSE) and Alternating Minimization (AM) algorithms. Further research indicates that this algorithm is also applicable to large-scale networks.

Reduction of Power Losses and Voltage Profile Improvement in a Smart Grid Incorporated with Electric Vehicles

Governments worldwide have adopted energy-saving policies out of concern for the planet. System efficiency and renewable energy are needed to reduce greenhouse gas emissions, which cause climate change. Electricity generation is the biggest polluter, followed by transportation. Electric vehicles would strain electricity infrastructure without technical solutions. This study uses a hybrid genetic algorithm particle sworn optimization (HGAPSO) to find the optimal switching and feeder reconfiguration approach. Meet transmission constraints while reducing real power losses and improving system bus voltage. In the context of power system change, what are the benefits of employing the HGAPSO approach as opposed to the GA method and the PSO method, respectively. HGAPSO increases network power losses and voltage dispersion. Improved algorithms can help solve this crucial issue. It uses many heuristic optimization techniques to reconfigure transmission network connectivity and determine the best configuration. Limit bus voltage changes while maintaining the system’s radial structure and lowering power usage. MATLAB’s IEEE 33-bus communication network evaluated procedure reliability and performance. The results show that the proposed method reduces power waste during standalone runs and speeds up processing.

Fault detection and protection in a meshed MMC[sbnd]HVDC grid based on bus-voltage change rate and fault component current

Fault protection for a modular multi-level converter (MMC)-based high voltage direct current (HVDC) grid with dc circuit breakers (DCCBs) is a great challenge, because faults need to be isolated fast to prevent the collapse of the grid and overcurrent damage to the equipment. Before clearing faults, faults must be detected as soon as possible. However, the fast rising speed of fault currents and the emerging fault between the DCCB and line reactor increase the difficulty of fault protection. A fast and reliable fault detection and protection method relying on bus-voltage change rate and fault component current is proposed in this paper. It requires the measurements with local sensors and makes use of a lower number of voltage sensors. The proposed algorithm is applied to a four-terminal MMCHVDC grid. Results show that the proposed method can identify the fault type and discriminate bus faults, line faults, and wall bushing faults. It can detect faults quickly and does not generate erroneous and unnecessary trip signals.

The research on Inertial Control Strategy of DC Distribution Network

The DC power grid has characteristics that the AC power grid does not have, and is becoming increasingly important in an environment where renewable energy sources are being connected to the power system in large numbers. It is of great importance to enhance the virtual inertia of the DC grid side for the whole distribution network. Using the subsequent addition of the improved layering strategy, the system inertia time is used to visually evaluate the DC system for inertia size analysis, and the conclusion that the capacitance value outside the system is too small to cope with the external disturbance changes is found. The virtual inertia analysis of the system is also performed to grasp the relationship between the increasing level of virtual inertia and the size of the applied capacitance. After test in mathematical simulation software, it was verified that the addition of virtual relational control can change the instantaneous absorbed power emitted by the system, thus ensuring that the bus voltage changes within a reasonable range.

A stability control way of bus voltage in DC microgrid with constant power load

During the operation of the independent DC microgrid, the bus voltage will fluctuate with the random changes of the load and source. To maintain the stability of the bus voltage, a control strategy needs to be introduced in the DC microgrid. According to the bus voltage change of DC microgrid, this paper establishes a large‐signal mathematical model of DC microgrid with constant power load. Taking the bidirectional DC‐DC converter as the control object, a sliding mode variable structure controller based on the washout filter is introduced, and the bus voltage is stabilized at the desired voltage value through the selection of control parameters. The simulation experiment results show that the control strategy proposed in this paper can effectively restrain the fluctuation of the bus voltage under the condition of random changes of the load and source and has strong robustness. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Decentralised power distribution and SOC management algorithm for the hybrid energy storage of shipboard integrated power system

In the medium voltage direct current (MVDC) shipboard grid, the inherent inertial support from the DC capacitors is too small to resist step changes or fluctuations from the high power pulse load and propulsion load, which results in lower DC voltage quality. This study proposes a decentralised control algorithm for the MVDC shipboard hybrid energy storage system (HESS) to enhance the onboard survivability. This algorithm adjusts the droop control coefficient based on the bus voltage change rate adaptively, meanwhile the voltage differential signal processing and filtering are implemented by the trace differentiator. In addition, the proposed algorithm also has state-of-charge (SOC) balancing and SOC recovery abilities between multiple groups of energy storage devices. The parameter selection principle are analysed, and a variety of working conditions are simulated and verified in PSCAD. Theoretical analysis and simulation show that, HESS can achieve good power distribution and SOC management performance without communication compared to fixed droop coefficient control strategies, and the dynamic characteristics of bus voltage have been significantly improved.

Research on Fast Determination of Feeder Fault Based on Intelligent Alarm

According to the present situation that it is difficult for power dispatcher to identify and handle different types of feeder faults in time. This paper analyses the relationship between different types of feeder faults and 10kV bus grounding signal, 10kV bus voltage changes, bus grounding signal frequency, feeder switch trip signal, load change of fault feeder. On this basis, the mathematical calculation model based on the calculation of alarm signal and Telemetry data calculation is established. Then sends out intelligent alarm based on calculation results. It can quickly distinguish all kinds of faults, the accuracy of judgment is over 98%. It greatly improves the accuracy and efficiency of fault judgment and handling, also reduces user outage and risk of personal electric shock.

A smart charging algorithm-based fast charging station with energy storage system-free

With the growing popularity of electric vehicles (EV), there is an urgent demand to solve the stress placed on grids caused by the irregular and frequent access of EVs. The traditional direct current (DC) fast charging station (FCS) based on a photovoltaic (PV) system can effectively alleviate the stress of the grid and carbon emission, but the high cost of the energy storage system (ESS) and the under utilization of the grid-connected interlinking converters (GIC) are not very well addressed. In this paper, the DC FCS architecture based on a PV system and ESS-free is first proposed and employed to reduce the cost. Moreover, the proposed smart charging algorithm (SCA) can fully coordinate the source/load properties of the grid and EVs to achieve the maximum power output of the PV system and high utilization rate of GICs in the absence of ESS support for FCS. SCA contains a self-regulated algorithm (SRA) for EVs and a grid-regulated algorithm (GRA) for GICs. While the DC bus voltage change caused by power fluctuations does not exceed the set threshold, SRA readjusts the charging power of each EV through the status of the charging (SOC) feedback of the EV, which can ensure the power rebalancing of the FCS. The GRA would participate in the adjustment process once the DC bus voltage is beyond the set threshold range. Under the condition of ensuring the charging power of all EVs, a GRA based on adaptive droop control can improve the utilization rate of GICs. At last, the simulation and experimental results are provided to verify the effectiveness of the proposed SCA.

A Novel Double-Quadrant SoC Consistent Adaptive Droop Control in DC Microgrids

This brief uses a double-quadrant state-of-charge (SoC) consistent adaptive droop control method for extending the service life of distributed energy storage units (DESUs). During charging, the power absorbed by DESU is inversely proportional to its SoC. On the other hand, during discharging, the power emitted by DESU is proportional to its SoC. The SoC of DESUs and the power absorbed or emitted by the DESUs tend to be consistent under charging and discharging conditions. To compensate for the direct-current (DC) bus voltage change caused by droop control during charging and discharging of DESUs, this brief proposes a novel double-quadrant SoC consistent adaptive droop control method which is based on multi-agent approach and considers the real-time capacities of DESUs. The reliability of the proposed novel control design method is confirmed by simulations.

Adaptive and Exact Linearization Control of Multicellular Power Converter Based on Shunt Active Power Filter

Most research work on active power filter (APF) uses constant DC bus voltage. However, variable nonlinear load might affect the stability of these APFs and increase the power switching loss and voltage stress on switches. In this work, the contribution is twofold. First, regulate the DC bus voltage of APF, adaptively, with the nonlinear load variations and generate the reference of the harmonic currents based on the instantaneous power theory. Second, track this reference to mitigate harmonics of the grid-side current by the exact linearization control of three-phase multicellular power converter with reduced rating power switches and reduced power switching loss under variable nonlinear load. Simulation results with comparison study with classical topology of power converter demonstrate that the adaptive exact linearization control enhances the power quality with a minimum power switching loss and reduces the total harmonic distortion of grid-side current to a value that satisfies the limits of IEEE standard. Moreover, the DC bus voltage changes, adaptively, according to different values of nonlinear load power.

FLiER: Practical Topology Update Detection Using Sparse PMUs

In this paper, we present a Fingerprint Linear Estimation Routine to identify topology changes in power networks using readings from sparsely deployed phasor measurement units (PMUs). When a power line, load, or generator trips in a network, or when a substation is reconfigured, the event leaves a unique “voltage fingerprint” of bus voltage changes that we can identify using only the portion of the network directly observed by the PMUs. The naive brute-force approach to identify a failed line from such voltage fingerprints, though simple and accurate, is slow. We derive an approximate algorithm based on a local linearization and a novel filtering approach that is faster and only slightly less accurate. We present experimental results by using the IEEE 57-bus, IEEE 118-bus, and Polish 1999-2000 winter peak networks.

Fault Location Using Wide-Area Measurements and Sparse Estimation

This paper describes a fault location method which uses sparsely located wide-area synchronized phasor measurements. The main contribution is the way fault location is reformulated as a sparse estimation problem. Faulted system is modeled by equivalent terminal bus injections which would cause the same changes in bus voltages with the fault current drawn at any point along the faulted line. Once these injections are estimated, the fact that the ratio between equivalent injections at the two terminal buses depends only on the ratio of serial impedances on each side of the fault point can be used to locate the fault. It is shown that this formulation applies to both two terminal lines as well as teed lines regardless of fault type or resistance. Assuming availability of an accurate three-phase network model and a sufficient number of phasor measurements over the entire network, an underdetermined set of linear equations can be formed and then solved for the sparse equivalent bus injections. This is accomplished by applying two $L_{1}$ norm regularization optimization methods namely Lasso and overlapping group Lasso. Effectiveness of these methods are verified by extensive simulations.

Dynamic modelling and small signal stability analysis of voltage source converter-based HVDC system

In this paper, the modelling of the entire VSC-HVDC system is presented based on d-q axis decomposition and state space modelling is formulated for analysis. Eigenvalues analysis is used for optimal tuning of PI controller based on PSO technique. The system is simulated under most of the frequently occurring faults and abnormal operating conditions such as three-phase fault, parameter variation, frequency variation and change in active and reactive power, change in short circuit ratio and bus voltage reduction and change in converter parameters through MATLAB simulation. The results are presented for the proposed controller with comparison to conventional PI controller under various fault condition.

Initial Voltage Change on Capacitor Switching

This letter presents field measurements of capacitor switching transients with initial bus voltage changes different from widely used assumptions. Instead of being pulled toward zero in all three phases, initial voltage changes in both directions are seen in grounded capacitor switchings. Electromagnetic Transients Program simulation shows that the reason could be pole spread in breaker closing and mutual coupling between the three phases. The letter suggests that this transient pattern be considered in capacitor switching research.

Fault Location for Single-Circuit Line Based on Bus-Impedance Matrix Utilizing Voltage Measurements

Diverse transmission line fault location algorithms have been proposed in the past depending on measurements available. Existing algorithms usually require measurements captured from buses of a faulted line. By taking advantage of the bus-impedance matrix technique, this paper presents a possible fault location approach for single-circuit lines utilizing only voltage measurements from one or two buses, which may be distant from the faulted line. With the addition of a fictitious bus where the fault occurs, the transfer impedances of this bus and other buses are revealed as a function of the fault location. Based on the relationship between the bus voltage change due to fault and the transfer impedance, the fault location can be derived. Shunt capacitance of the line is ignored first and then fully considered based on distributed parameter line model. Electromagnetic transients program simulation studies have shown quite encouraging results.

A Novel Approach for Sensitivity Calculations in the Radial Distribution System

In this paper, a novel approach for calculating the sensitivities of active/reactive power loss and voltage magnitudes with respect to active/reactive power injection at any bus in the radial distribution system is presented. In a radial distribution system, the changes in bus voltages and branch flows due to active/reactive power injection at any bus depend on the network topology. The key to the present method is the formation of a matrix whose structure is dependent only on the network topology. The proposed method is able to calculate the various sensitivity indices for single as well as multiple sources in the system. It is also able to handle all possible radial distribution system structures regardless of the system size proficiently. The results obtained by the proposed method have been compared with the simulated (conventional load flow) and the adjoint network approach results

Identification of the vulnerable transmission segment and cluster of critical machines using line transient potential energy

When a power system is subjected to a large disturbance, effective identification of vulnerable transmission segment and generator groupings in the electric network contribute to the effective analysis of power system dynamic behaviour and the determination of optimal locations of FACTS devices. Also, computational simple and reliable identification of critical machines is of primary importance in the successful application of direct or hybrid transient stability assessment methods such as TEF, EEAC and hybrid methods. In the paper, a new approach is proposed for identifying the transmission vulnerable segment (the weakest cutset), and then classifying machines into critical cluster and remaining cluster, using a quantitative transmission line vulnerability assessment index derived from the post-fault line transient potential energy and bus voltage changes. The calculation of the index is simple and fast, as only the line flow and bus voltage along the post-fault trajectory are required. Case studies using the IEEE 10-generator and 50-generator test systems are given to illustrate the validity of the proposed method.

Minimum/maximum excitation limiter performance goals for small generation

Small generators connected to the electric utility system often act as followers as they tend to follow power system bus voltage variations. For the lack of kVA capacity, small machines tend to be susceptible to becoming over or underexcited (excessive VArs in or VArs out of the generator) as the voltage regulator tries to maintain its setpoint with variations in system bus voltage. Minimum and maximum excitation limiters are utilized to limit the voltage regulator characteristic response to system bus voltage changes, that can otherwise result in machine overheating and/or pulling out of synchronization. This paper reviews the operating performance of minimum and maximum excitation limiters used on small machines, and provide the user typical performance expectations. The examples shown by the authors highlight both main field and exciter field applications.