Voltage Regulation Performance Research Articles

Using Group Predictive Voltage and Frequency Regulators of Distributed Generation Plants in Cyber-Physical Power Supply Systems

The widespread use of distributed generation (DG) plants in cyber-physical power supply systems (CPPSS) requires solving the complex problem of setting their regulators. The presented study aimed to determine the performance of the group predictive voltage and frequency regulators of DG plants in CPPSS. These studies were conducted in the MatLab environment on the CPPSS models with gas turbine units and with a small-scale hydroelectric power plant. The proposed method for tuning group predictive regulators makes it possible to improve the quality control indices. The research has established that with an additional load connected, the maximum voltage dip is reduced by a factor of 3.5 compared to conventional control regulators. In addition, the time of a transient process for the generator rotor speed is decreased by a factor of 3. In the case of a short-term short circuit, predictive regulators can reduce the time of the transient process by a factor of 1.5 and the overshoot by more than 2 times. The simulation results have confirmed the efficiency of group predictive regulators when used in DG plants, i.e., improvement of the quality of control processes in various operating modes.

3Φ4W Hybrid Frequency Parallel Uninterruptable Power Supply for Reducing Voltage Distortion and Improving Dynamic Response

This article presents a three-phase four-wire ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\Phi 4\text{W}$ </tex-math></inline-formula> ) hybrid frequency parallel uninterruptable power supply (HbFPUPS) with ripple compensation to reduce output voltage distortion and improve dynamic response for high power UPS applications. An HbFPUPS is composed of a low-frequency-high-power uninterruptible power supply (LFUPS) and a high-frequency-low-power uninterruptable power supply (HFUPS) connected in parallel. LFUPS tracks the major load currents with lower frequency (LF) insulated gate bipolar transistors (IGBTs) while HFUPS regulates the output voltage and compensates the current ripples of LFUPS with higher frequency (HF) SiC MOSFETs. For multifrequency parallel inverters, ripple compensation control reduces LF ripples and mitigates multifrequency ripple issue in filter design when interleaved switching is not available. Compare with conventional single and parallel inverters with identical frequency and power, HbFPUPS provides a sufficient dynamic response without overdesigning the system with high-power-high-frequency costly SiC MOSFETs, or trading off efficiency for higher switching frequency operation on IGBTs. The remaining HF ripple and increased dynamic response reduce filter inductance and capacitance. In this article, control, parameter design, voltage regulation performance, and stability of HbFPUPS are analyzed. Voltage distortion, ripple, and transient error reductions are validated with the 300-kVA simulated and 10-kVA experimental results of a HbFPUPS in linear, rectified, and step-up/down load tests.

A Distributed Current Sharing Strategy for Islanded AC Microgrids Based on Low-Bandwidth Communication

Bus voltage regulation and current sharing are significant to ensure the normal operation of islanded microgrids. In this paper, a low-bandwidth communication (LBC)-based distributed current sharing strategy for islanded ac resistive microgrids is proposed, especially when the wire impedances of parallel-connected inverters are mismatched. In a general case, all the balanced, unbalanced and harmonic components of load current should be shared accurately. Therefore, in the local controller, those components of inverter output currents are extracted and regulated to follow the component average values generated based on LBC. To guarantee the bus voltage regulation, the influence of current sharing loops on voltage references is eliminated by subtracting the average voltage reference compensation from the current sharing controller outputs. A simplified inverter small-signal model is established, based on which the system stability is analyzed. Besides, the steady-state bus voltage regulation performance is discussed. The simulation in MatLab/Simulink is used to demonstrate the current sharing performance and bus voltage regulation ability. A hardware-in-loop platform of an ac microgrid prototype is built, where the power stage is in a real-time simulator and the controllers are implemented with DSPs. The results validate the effectiveness of the proposed strategy.

Superior transient and stability performance of voltage regulation by battery-fed bidirectional converter for supporting various operational modes of PMDC machine

This paper presents a systematic procedure to design a voltage controller for achieving superior dynamic performance of a battery-fed bidirectional converter for supporting both motoring and regenerative operations of a permanent magnet direct current (PMDC) machine. In this respect, derivation of a small signal model of overall system is given. Next, the condition for absolute stability is calculated from the model on the basis of the Routh-Hurwitz criterion. Then, gains of the proportional-integral (PI) controller have been tuned using the Ziegler-Nichols tuning chart as per the conventional approach. But, the calculated gains from Ziegler-Nichols tuning chart do not provide satisfactory dynamic performance and sound stability margin under variable voltage conditions. Thus, performance of voltage regulation is deeply investigated and redesign of the voltage controller is emphasised through further mathematical analysis for achieving both superior dynamic performance and significantly stronger stability margin. Superiority of this proposed approach is verified in MATLAB-SIMULINK software based modelling of the physical system and also, in experimental platform.

Superior transient and stability performance of voltage regulation by battery-fed bidirectional converter for supporting various operational modes of PMDC machine

Superior transient and stability performance of voltage regulation by battery-fed bidirectional converter for supporting various operational modes of PMDC machine

Fault Tolerant Sliding Mode Controller Design Subject to Sensor Faults for Output Voltage Regulation of a Self-Excited Induction Generator

This paper aims to improve the performance of the output voltage regulation of the Self-Excited Induction Generator (SEIG) with fixed capacitor-thyristor controlled reactor (FC-TCR) structure in case of sensor faults. A sliding mode controller (SMC) is designed to generate the triggering angle of the FC-TCR to regulate the output voltage. The performance of proposed SMC is firstly tested without sensor faults and high success in tracking the reference is obtained. Since an additive fault occurs on the sensor, SMC performs well tracking dynamic but is on the incorrect reference. Therefore, Radial Basis Function Neural Network (RBFNN) is trained accurately with the 2% mean squared error (MSE) by taking the stator currents, triggering angle and generator speed as inputs, whereas the output voltages of the SEIG are outputs. Further, fault detection architecture is well designed with a voltage error index calculated by subtracting the sensor output from the estimated output. The threshold based selector reconfigures the controller well. The simulation results show that in case of sensor faults and various loading conditions, proposed fault tolerant SMC remains the actual output voltage of the SEIG at real reference with maximum 2.2% steady state error in a finite time.

An adaptive power split strategy with a load disturbance compensator for fuel cell/supercapacitor powertrains

Electric vehicles powered by fuel cell and supercapacitor hybrid power sources are of great interest. However, the power allocation between each power source is challenging and the DC bus voltage fluctuation is relatively significant in cascaded PI control schemes. This paper develops a power control strategy with an adjustable cut-off frequency, using an artificial potential field, to adaptively split the load current between the fuel cell and the supercapacitor under various load conditions. The adaptive cut-off frequency is calculated by cutting the load frequency spectrum with an allocation ratio that changes with the supercapacitor state of charge. Therefore, the relatively lower frequency portion of the load current is provided by the fuel cell and the supercapacitor handles the higher frequency portion. To enhance the control performance of the DC bus voltage regulation against the load disturbance, a load disturbance compensator is introduced to suppress the DC bus voltage fluctuation when the load variation occurs, which is implemented by a feed-forward controller that can compensate the load current variation in advance. The effectiveness of the proposed strategy is validated by extensive experiments.

Voltage Regulation Performance Evaluation of Distributed Energy Resource Management via Advanced Hardware-in-the-Loop Simulation

This paper evaluates the performance of coordinated control across advanced distribution management systems (ADMS), distributed energy resources (DERs), and distributed energy resource management systems (DERMS) using an advanced hardware-in-the-loop (HIL) platform. This platform provides a realistic laboratory testing environment, including accurate dynamic modeling of a real-world distribution system from a utility partner, real controllers (ADMS and DERMS), physical power hardware (DERs), and standard communications protocols. One grid service—voltage regulation—is evaluated to show the performance of the coordinated grid automation system. The testing results demonstrate that the coordinated DERMS and ADMS system can effectively regulate system voltages within target operation limits using DERs. The realistic laboratory HIL testing results give utilities confidence in adopting the grid automation systems to manage DERs to achieve system-level control and operation objectives (e.g., voltage regulation). This helps utilities mitigate potential risks (e.g., instability) prior to field deployment.

An Anti-Fluctuation Compensator Design and Its Control Strategy for Wind Farm System

Large-scale wind farms in commercial operations have demonstrated growing influence on the stability of an electricity network and the power quality thereof. Variations in the output power of large-scale wind farms cause voltage fluctuations in the corresponding electrical networks. To achieve low-voltage ride-through capability in a doubly fed induction generator (DFIG) during a fault event, this study proposes a real-time reactive power control strategy for effective DFIG application and a static synchronous compensator (STATCOM) for reactive power compensation. Mathematic models were developed for the DFIG and STATCOM, followed by the development of an indirect control scheme for the STATCOM based on decoupling dual-loop current control. Moreover, a real-world case study on a commercial wind farm comprising 23 DFIGs was conducted. The voltage regulation performance of the proposed reactive power control scheme against a fault event was also simulated. The simulation results revealed that enhanced fault ride-through capability and prompt recovery of the output voltage provided by a wind turbine generator could be achieved using the DFIG along with the STATCOM in the event of a three-phase short-circuit fault.

Automatic voltage regulator performance enhancement using a fractional order model predictive controller

In this paper, a new design method for fractional order model predictive control (FO-MPC) is introduced. The proposed FO-MPC is synthesized for the class of linear time invariant system and applied for the control of an automatic voltage regulator (AVR). The main contribution is to use a fractional order system as prediction model, whereas the plant model is considered as an integer order one. The fractional order model is implemented using the singularity function approach. A comparative study is given with the classical MPC scheme. Numerical simulation results on the controlled AVR performances show the efficiency and the superiority of the fractional order MPC.

Automatic voltage regulator performance enhancement using a fractional order model predictive controller

Automatic voltage regulator performance enhancement using a fractional order model predictive controller

Enhancement of power system transient stability and voltage regulation performance with decentralized synergetic TCSC controller

In this paper, a new nonlinear control approach for thyristor-controlled series capacitors (TCSCs) has been proposed to schedule TCSC line active power transfer, improving transient stability, and obtain acceptable voltage regulation performance of the power system. This control method for the TSCS has been presented based on synergetic control theory. According to the control targets, a linear combination of the TCSC voltage variation, generator rotor speed, TCSC active power, and TCSC reactance is chosen to design a decentralized synergetic TCSC controller (DSTC). A dynamic parameter adaption approach is also presented for updating the DSTC parameters to satisfy control objectives under different power system operating conditions. In the studied system, each generator is equipped with a decentralized improved synergetic excitation controller (ISEC). Dynamic characteristic of the presented DSTC is studied in a single machine infinitive bus and a WSCC-type 3-machine 9-bus power system. A restructured improved synergetic excitation controller (RISEC) has also been formulated to investigate the impact of ISEC on the multi-machine system. Simulation results show that the proposed controller can provide better transient stability, active power flow of the TCSC line, and voltage regulation performance than the ISEC with or without conventional TCSC controller and conventional power system stabilizer without any TCSC controller.

Design and Simulation of a Capless Low Drop Out Voltage Regulator

Portable electronic devices mostly used battery as their primary source for operation hence longer running batteries or Power resources or vital for any portable device need for stable voltage supplies have led to the development of low dropout voltage regulators low dropout regulators provide stable regulated output voltage in various operating conditions which makes it useful in portable devices that design of high performance and stable low dropout voltage regulator is a challenge nowadays with decreasing device size and increasing power densities. The proposed circuit used a 5pack architecture of error amplifier. This paper proposes the study of behavior of the LDO voltage regulator with internal capacitors i.e., capless. The regulated voltage of 1.8V is obtained using the typical power supply of 2.2V obtained dropout voltage of 400mv with the delay of 12.77micro sec, power consumed 1.816W. The proposed design produced DC gain of 31.77db,with the load current variation of 0 to 20mA. The capless LDO architecture is verified in the Cadence 180nm technology. The architecture provides a stable gain and plot for both Temperature and Load Variations. The stability issues are overcome using the compensation techniques which uses a current amplifier and a capacitor in the differentiator configuration. The current amplifier implemented uses current mirror with current copying ratio of unity.

A novel fractional order PID plus derivative (PIλDµDµ2) controller for AVR system using equilibrium optimizer

PurposeThe purpose of this paper is to improve transient response and dynamic performance of automatic voltage regulator (AVR).Design/methodology/approachThis paper proposes a novel fractional order proportional–integral–derivative plus derivative (PIλDµDµ2) controller called FOPIDD for AVR system. The FOPIDD controller has seven optimization parameters and the equilibrium optimizer algorithm is used for tuning of controller parameters. The utilized objective function is widely preferred in AVR systems and consists of transient response characteristics.FindingsIn this study, results of AVR system controlled by FOPIDD is compared with results of proportional–integral–derivative (PID), proportional–integral–derivative acceleration, PID plus second order derivative and fractional order PID controllers. FOPIDD outperforms compared controllers in terms of transient response criteria such as settling time, rise time and overshoot. Then, the frequency domain analysis is performed for the AVR system with FOPIDD controller, and the results are found satisfactory. In addition, robustness test is realized for evaluating performance of FOPIDD controller in perturbed system parameters. In robustness test, FOPIDD controller shows superior control performance.Originality/valueThe FOPIDD controller is introduced for the first time to improve the control performance of the AVR system. The proposed FOPIDD controller has shown superior performance on AVR systems because of having seven optimization parameters and being fractional order based.

Security-Constrained Optimal Sizing and Siting of BESS in Hybrid AC/DC Microgrid Considering Post-Contingency Corrective Rescheduling

Hybrid AC/DC microgrids allow the integration of diverse renewable energy resources. However, the security and the reliability of hybrid AC/DC microgrid systems are challenged by various contingencies. In this paper, we propose a BESS sizing and siting approach which uses a combined stochastic programming and robust optimization method to cope with uncertainties of loads, wind power generation, and BESS charging/discharging efficiency. The proposed iterative solution enhances voltage and frequency regulation performances in an islanded hybrid AC/DC microgrid which is subject to post-contingency corrective rescheduling. A successive linear power flow approximation method is adopted to simulate post-fault power flows and represent static frequency characteristics of loads and generators. The proposed iterative solution for the mixed-integer linear programming (MILP) formulation can achieve computational tractability for determining pre-fault and post-fault initial operation points. Case studies corroborate the effectiveness of the proposed model and the solution method.

Autonomous Voltage Regulation by Distributed PV Inverters With Minimal Inter-node Interference

The reactive power capability of distributed photovoltaic (PV) inverters could be exploited to mitigate voltage violations under high PV penetration in the distribution grid. Coordinating the reactive power dispatch of individual PV inverters to obtain desired voltage regulation performance is a major challenge. In this article, a decentralized method is proposed to enable PV inverters to autonomously regulate terminal node voltages. The proposed method minimizes the effect of a terminal node's reactive power contribution on the voltage profile of its respective parent-to-terminal node. This ensures that the interference between the voltage regulation of terminal nodes by individual PV inverters is minimized. The performance of the proposed decentralized scheme is verified by extensive powerflow simulations on the EPRI Circuit 24 test feeder in open-source distribution system simulation platform OpenDSS.

배전계통 전압 측정오차가 분산전원 출력 제어에 미치는 영향 분석

In this paper, effect of error in voltage measurement on output control of distributed generations(DGs) for voltage regulation in distribution systems is analyzed. Volt-Var and Volt-Watt control of a smart inverter which is regarded as one of the typical voltage regulation algorithms based on voltage measurement is considered and characteristics of active/reactive power control and performance of voltage regulation are theoretically evaluated. For verification of the analyzed effect, simulations based on the Korean distribution system are performed by using MATLAB/Simulink. Based on the simulation results, we can confirm that output control of DGs based on the voltage measurement at point of common coupling (PCC) is highly affected by even small error in voltage measurement.

Optimized neural network and adaptive neuro-fuzzy controlled dynamic voltage restorer for power quality performance

Abstract In this article, a hybrid approach is implemented namely, neural network training (NNT) based machine learning (ML) estimator inspired by artificial neural network (ANN) and self-adaptive neuro-fuzzy inference system (ANFIS) to tackle the voltage aggravations in the power distribution network (DN). In this work, potential of swarm intelligence technique namely particle swam optimization (PSO) is analysed to obtain an optimum prediction model with certain modifications in training algorithm parameters. In practice, when the systems are continuously subjected to parametric changes or external disturbances, then ample time is dedicated to tune the system to regain its stable performance. To improve the dynamic performance of the system intelligence-based techniques are proposed to overcome the shortcomings of conventional controllers. So, gain tuning process based on the intelligence system is a desirable choice. The statistical tools are used to proclaim the effectiveness of the controllers. The obtained MSE, RMSE, ME, SD and R were evaluated as 0.0015959, 0.039949, −0.00089838, 0.039941 and 1 in the training phase and 0.0015372, 0.039207, −0.0005657, 0.039203 and 1 in the testing phase, respectively. The results revealed that the ANFIS-PSO network model could accomplish a better DC voltage regulation performance when it is compared to the conventional PI. The proposed intelligence strategies confirm that the predicted DVR model based on NNT-ML and ANFIS has faster convergence speed and reliable prediction rate. Moreover, the simulation results show that the dynamic response is improved with proposed PSO based NNT based ML and ANFIS (Takagi-Sugeno) that significantly compensates the voltage based PQ issues. The proposed DVR is actualized in MATLAB/SIMULINK platform.

Highly isolated switching mode power supply for solid-state transformers in railway vehicles

This paper discusses an isolated switching mode power supply (SMPS) with an AC 30 kVrms insulation capability for application to the solid-state transformers (SSTs) in railway vehicles. The insulation capability of the SMPS should be higher than AC 25 kVrms for application at the SSTs in railway vehicles. The proposed highly isolated SMPS is superior to commercial isolated power supplies with low insulation capability, which is normally less than 20 kV. The input side of the proposed isolated SMPS is physically separated from its output side by a specially designed miniature high-frequency (HF) transformer to obtain high insulation capability. The core of the miniature HF transformer is separated by insulation material. The primary and secondary coils are wound around each separated core. A CLLC resonant converter that consists of a primary resonant capacitor (C), two inductors (LL), and a secondary resonant capacitor (C) is applied as the proposed isolated SMPS topology to improve the output voltage regulation performance, which varies due to a large leakage inductance derived from the airgap of the proposed miniature HF transformer. Experiments are carried out to verify the CLLC resonant converter of the proposed isolated SMPS. Electrostatic finite element method (FEM) simulations and high potential (HiPot) tests are carried out to verify the AC 30 kVrms insulation capability of the proposed isolated SMPS. The electrostatic FEM simulations demonstrate the DC 42.43 kV insulation capability, and the HiPot tests verify the insulation capability from AC 5 kVrms to AC 30 kVrms.

Multivariable Unconstrained Pattern Search Method for Optimizing Digital PID Controllers Applied to Isolated Forward Converter

Most of the traditional PID tuning methods are heuristic in nature. The heuristic approach-based tuned PID controllers show only nominal performance. In addition, in the case of a digital redesign approach, mapping of the heuristically-designed continuous-time PID controllers into discrete-time PID controllers and in case of the direct digital design approach, mapping of the continuous-time plant (forward converter) into the discrete-time plant, results in frequency distortion (or warping). Besides this, nonlinear elements such as ADC and DAC, and delay in the digital control loop deteriorate the control performance. There is a need to tune conventionally-designed digital controllers to enhance performance. This paper proposes optimized discrete-time PID controllers for a forward DC–DC converter operating in continuous conduction mode (CCM). The considered conventional digital PID controllers designed on the basis of the digital redesign and direct digital approaches are tuned by one of the multivariable unconstrained pattern search methods named Hooke–Jeeves (H–J) search method to ensure excellent output voltage regulation performance against the changes in input voltage and load current. Numerical results show that the H–J-based optimized PID compensated forward converter system shows tremendous improvement in performance compared to its unoptimized counterpart and simulated annealing (SA)-based compensated system, thus justifying the applicability of the H–J method for enhancing the performance.