Shunt Compensation Research Articles

Adaptive Overhead Transmission Lines Auto-Reclosing Based on Hilbert–Huang Transform

This paper presents a reliable and fast index to detect the instant of arc extinction for adaptive single-pole automatic reclosing (ASPAR). The proposed method is a simple technique for ASPAR on shunt compensated transmission lines using the Hilbert–Huang Transform (HHT). The HHT method is a combination of the empirical mode decomposition (EMD) and the Hilbert transform (HT). The first intrinsic mode function (IMF1) decomposed by EMD, which contains high frequencies of the faulty phase voltage, was used to calculate the proposed index. HT calculates the first IMF spectrum in the time-frequency domain. The presented index is the sum of all frequency contents below 55 Hz, which remains very low until the fault clearance. The proposed method uses a global threshold level and therefore no adjustment is needed for different transmission systems. This method is effective for various system configurations including different fault locations, line loading, and various shunt reactor configurations, designs, compensation rates, and placement. The performance of the method was verified using 324 test cases simulated in electromagnetic transient program (EMTP) related to a 345 kV transmission line. For all the test cases, the algorithm successfully operated with an average reclosing time delay of 32 ms.

Shunt Compensaton of the Integrated Nigeria’s 330KV Transimission Grid System

The Nigerian Power system is complex and dynamic, as a result of this it is characterized by frequent faults and outages resulting to none steady supply of power to the teaming consumers. This has great effect on the activities and mode of living of Nigerians. The research work was carried out on contingency analysis on the existing integrated 330KV Nigeria grid system and to carry out a shunt compensation on the violated buses, the shutdown of Eket-Ibom line being the case study so as to determine the following; uncertainties and effects of changes in the power system, to recognize limitations that can affect the power reliability and minimize the sudden increase or decrease in the voltage profile of the buses through shunt compensation of buses. Determine tolerable voltages and thermal violation of +5% and -5% of base voltage 330 KV (0.95-1.05) PU and to determine the critical nature and importance of some buses. This is aimed at bridging the gap of proposing further expansion of the grid system which is not only limited by huge sum of finance and difficulties in finding right – of- way for new lines but also which faces the challenges of fixed land and longtime of construction. The data of the network was gotten and modeled. The power flow and contingency analysis of the integrated Nigeria power system of 51 buses (consisting of 16 generators and 35 loads) and 73 transmission lines were carried out using Newton-Raphson Load Flow (NRLF) method in Matlab environment, simulated with PSAT software. Shunt compensation of the weak buses were done using Static Var Compensator (SVC) with Thyristor Controlled Reactor- Fixed capacitor (TCR-FC) technique. Results obtained showed that the average voltage for base simulation was 326.25KV, contingency 323.67KV and compensation was 322.37 KV. Voltage violations for lower limit were observed at Itu as 309KV and Eket as 306.81 KV while violations for upper limit were recorded at Damaturu as 352.85KV, Yola as 353.62 KV, Gombe as 355.98KV, and Jos as 342.97 KV. However after shunt compensation there were improvements for the violations at lower limits and that of higher limit were drastically brought down as recorded below: Damaturu 329.93 KV, Jos 330 KV, Eket 327.2 KV, Gombe 333.55KV, Itu 330KV, and Yola 330.52KV

Mitigation of power quality issues using UPQC

Abstract Power quality has become major concern these days due to application of power electronic devices. Conventional equipment like passive filter, segregate series and shunt filters and synchronous condenser etc. have become inadequate to mitigate different power quality problems. Since, power quality mainly concerned with voltage quality and the current quality in the system. For voltage quality, series compensator is used and for current quality, shunt compensator is used. Further, when these two power quality problems are mitigated simultaneously, the device, which is used, called unified power quality conditioner (UPQC), in power distribution system. In this paper voltage related power quality problems such as (voltage sag, voltage swell, voltage and current distortion) are discussed and UPQC controller is simulated to mitigate these problems. There are different control techniques available for UPQC. Here one of them i.e., unit vector template generation (UVTG) is used to simulate UPQC controller. The considered system efficiently regulated the DC link voltage using properly tuned PI parameters. The proposed work is also validated using experimental results.

DESIGN AND PERFORMANCE ANALYSIS OF THREE PHASE SOLAR PV INTEGRATED UPQC

The intrusion of unified power quality conditioner in power transmission line can compensate voltage compensation and it brings more attention among various compensation techniques. The incremental production of sustainable renewable energy resource becomes more popular because of its eco-friendly and nonpolluting nature. Advancement of power production interfaces power compensating technique due to various power quality problems like voltage sag, voltage swell, voltage flicker, large voltage spikes and voltage distortion, etc. Both series and shunt compensators are attached within this proposed topology. The system posses active power filtering and distributed generation. In most case the power production and increasing the voltage from solar system may employ Maximum Power Point tracking algorithm (MPPT); it tracks maximum power from the panel and improves the efficiency. The compensation technique eliminates the need of MMPT by shunt compensation at load current; other inequalities are performed through series compensator. The experimental verification is done through MATLAB software. The transformer fetched with inverter terminal can do active power filtering; DC link capacitor delivers power whenever it is necessary to functioning. The inequalities correction improves power factor more than 0.85 by inter combining DSTATCOM and dynamic voltage restorer (DVR).

Subcycle Overvoltage Dynamics in Solar PVs

In 2017 and 2018, bulk power system (BPS) connected solar photovoltaic (PV) inverters tripped after grid disturbances in South California, causing large-scale power loss. One cause of PV tripping is subcycle overvoltage experienced by PV inverters when the grid suffers voltage dip and PVs enter into momentary cessation. This paper examines the underlying mechanism of the subcycle overvoltage dynamics. A dq-frame analytical model is built for a PV grid-integration system with a focus on the grid side converter (GSC) and grid interaction. PV's dc circuit dynamics and controls are ignored. Eigenvalue analysis indicates that two modes cause the subcycle overvoltage. The modes are associated with shunt compensation, grid electromagnetic dynamics, and PV inverter controls. Furthermore, a more insightful explanation of subcycle overvoltage is offered relying on s-domain admittance models. The dq-frame admittance is derived for the PV viewed from the point of common coupling (PCC). A circuit model relying on the derived admittance can demonstrate subcycle overvoltage due to momentary cessation. Impacts of grid strength, phase-locked-loop (PLL) parameters and converter current control parameters are all examined. It is found that the inherent LC dynamics due to shunt compensation and grid inductance are the main dynamics that can cause overvoltage, and momentary cessation excites overvoltage dynamics.

Improvement of Power Quality WECS using AI Based STATCOM

The major concern in a growing power quality is harmonics distortion which is caused by the non-linear nature of the loads. This problem has drawn much attention from utilities, users and industries. To reduce the harmonic distortion for improving the power quality of the system a custom power devices has been proposed. A static compensator (STATCOM) is implemented at distribution level for overcoming several power quality problems. In this paper, new control technic i.e AI is proposed on shunt compensator to estimates the weight values of load currents. The control approach is based on the convergence of the load currents and property of the input signal. A working prototype of the STATCOM is implemented using three-phase VSC and AI control technique based PWM controller approach is developed in MATLAB/SIMULINK.

Fuzzy Logic based H-bridge STATCOM Controller to compensate Unbalanced Voltages

In this paper a new method four-leg topology is suggested for shunt compensation, the H-bridge multilevel converters based on the half-bridge converters, to achieve higher performance as a STATCOM in a distorted and unbalanced medium-voltage large-current system. Further, an extended Fuzzy based STATCOM is proposed in order to manage more accurate compensation for high-power applications. Both proposals can be controlled for various purposes such as reactive power and unbalance compensation, voltage regulation, and harmonic cancellation. One interesting application for the Fuzzy logic based STATCOM could be the improvement in power quality and performance of the electrified railway traction power supply system. Both the H-bridge based STATCOM along with their proposed control strategies were simulated.

Power Quality Improvement Using Three-Phase Solar PV Integrated UPQC

This paper proposes the application of a Dynamic Voltage Restorer (DVR) to enhance the power quality and analyzed the solar PV integrated unified power quality conditioner (PV-UPQC).The PV-UPQC is employed to maintain power quality under various current and voltage distortion. The PV-UPQC consists of a shunt and series compensators connected back to back with common DC-link. The shunt compensator performs the dual function of extracting power from PV array apart from compensating for load current harmonics. The series compensator compensates for the grid side power quality problems such as grid voltage sag and swell. In proposed system Dynamic Voltage Restorer (DVR) is used as a series compensator and also it enhance the power quality. The UPQC is eliminate power quality issues like unbalanced grid voltage with harmonics and load harmonics. The performance of the system are evaluated by simulating in MATLAB/Simulink environment under a nonlinear load.

Voltage stability analysis of the Nigerian Power System using annealing optimization technique

The paper addresses the means of overcoming the challenge posed by voltage collapse to the stability of the Nigerian electric power system. The technique applied is based on time identification algorithm elaborating, at a given grid bus, the local phasor measurements at fast sampling rate. Elements such as adjustable shunt compensation devices, generator reactive generation, transformer tap settings are optimally adjusted at each operating point to reach the objective of minimizing the voltage stability index at each individual bus as well as minimizing the global voltage stability indicator. The control elements setting were optimized and the maximum possible MVA voltage stable loading has been achieved and a best voltage profile was obtained. Results of tests conducted on a 6-bus IEEE system and a typical 28-bus Nigerian power distribution network are presented and discussed.
 Keywords: Special protection systems, voltage stability analysis, voltage stability limit, voltage collapse mechanism, system security

Wide-Area Measurement-Based Adaptive Backup Protection for Shunt Compensation Environment

In this paper, the localization issue associated with distance relay protecting a transmission line with static synchronous compensator (STATCOM) is discussed. Generally, distance relay is mal-operated due to the dynamic behaviour of STATCOM during its inductive and capacitive modes of operation. Because, STATCOM operation creates the problem of correct measurement of fault distance and is responsible of under-reach and over-reach of distance relay. Furthermore, high fault resistance is also the reason of under-reach along with STATCOM operation. To overcome aforementioned challenges, an adaptive wide-area backup protection scheme (WABPS) is addressed which compares the calculated impedance and referenced impedance. Calculated impedance is the difference between impedance measured by relay and impedance contributed by fault resistance. Referenced impedance is the sum of fault impedance and impedance contributed by STATCOM. If calculated impedance is less than referenced impedance, then the relay will generate a trip signal. Proposed WABPS is inherent directional and provides information about fault detection, fault distance, and fault resistance during dynamic operation of STATCOM. The performance of the proposed WABPS is evaluated using technology of synchronize phasor measurement and communication channel. A 230 kV, 50 Hz system with a 24-pulse STATCOM is simulated and validated using PSCAD/EMTDC software package.

A Graphical Probabilistic Representation for the Impact Assessment of Wind Power Plants in Power Systems

Traditional methods used for the analysis and design of power systems, like power flow studies (PFS), do not consider any uncertainties. For example, when there is a high penetration of wind power plants (WPPs), whose raw material is intermittent. In this paper is proposed a graphical probabilistic representation (GPR) based on multi-objective performance index (MPI) to assess the impact of the WPPs penetration in power systems. This representation is applied to the southeastern network of Mexico, where there is increasing penetration of WPPs. Besides, a comparative study is presented, with and without a static var compensator (SVC) device connected to the mentioned network, to evaluate the effects of shunt compensation in the point of common coupling (PCC) with WPPs. The results of this comparison are discussed using the GPR proposed. The results show that GPR can be utilized as a useful tool to represent a considerable amount of information in a clear, compact, and single visual representation.

Improving Fault Ride-Through Capability of Fixed-Speed Wind Turbine Using Combined Shunt and Series Compensation Scheme

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RETRACTED ARTICLE: An effective compensation of power quality issues using MPPT-based cuckoo search optimization approach

Power quality becomes the most significant concerns for many reasons as the dependence of electricity is increasing in this modern society. In fact that less quality of power will generate some considerable losses in terms of economy in few moments. The potential power quality issues were flicker, voltage dips, supply and harmonic interruptions. The quality of power might be enhanced with the use of some filtering approaches and some compensators. This work presents a unique framework of optimal utilization of the unified power flow controller (UPFC). The UPFC’s inverter series is then controlled so as to perform the following functions: load reactive power sharing with the shunt inverter and compensation of voltage sag/swell. A cuckoo search optimization-based maximum power point tracking algorithm is employed for providing best fitness function for varying duty cycles. The approach of active power filter is widely employed in the harmonic compensation of voltage swell/sag. The proposed system also provides low rate of total harmonic distortion. MATLAB/Simulink-based simulation results are discussed to support the developed concept.

Unified Power Quality Conditioner using PV Fed SVPWM based Multilevel Converters for Power Quality Improvement

This paper presents a solar photovoltaic based unified power quality conditioner (PV-UPQC). The proposed system consists of a shunt compensator (ShC), series compensator (SeC) and PV array connected in parallel to a common dc-link. A three-level diode clamped multilevel inverter configuration is used as shunt and series converters. The SVPWM technique provides reduction in the common mode voltage and the balancing of the dc link voltage. The shunt compensation converter extracts power from PV array and provides compensation for load harmonic currents. The series compensation converter compensates for the power quality (PQ) problems such as grid voltage sags/swells and source harmonic voltages. The proposed system utilizes space vector pulse width modulation (SV-PWM) in multilevel converter topology for the mitigating the power quality problems using PV-UPQC. The proposed system improves PQ and also utilize RES, it also simultaneously improves both current and voltage disturbances. The performance of the system is analyzed in MATLAB/Simulink for nonlinear load conditions.

A New PV-Open-UPQC Configuration for Voltage Sensitive Loads Utilizing Novel Adaptive Controllers

In this article, a novel topology for photovoltaic (PV) fed open unified power quality conditioner has been proposed focusing on the requirement of voltage sensitive loads. It has incorporated the advantages of open unified power quality conditioner (UPQC) and grid connected PV systems by providing a possible solution towards the demand of different power quality levels at end user. Increasing the system robustness for various voltage and current distortions, adaptive controllers have been implemented for series and shunt compensators of UPQC. Adaptive notch filter based improved Syncronous Reference Frame (SRF) scheme has been utilized for the control of series compensator. An adaptive logarithmic absolute algorithm has been implemented for shunt part of proposed system. The utilization of moving average filter (MAF) instead of low pass filter (LPF) for dc bus voltage regulation has neglected the chance of high as well as low frequency ripples. A feed forward component has been added to the shunt controller to regulate the grid current at constant level in presence of grid disturbances. The proposed controllers are verified on a developed prototype of proposed system in the laboratory. The system performance is found satisfactory under various grid conditions like voltage sags, voltage swells, voltage unbalance, voltage harmonics, sudden load addition and removal, and variation in solar irradiation.

Comparison of Estimated Power Transfer in Transmission Line With and Without Shunt Compensator Using Different Line Models

In power systems, compensation techniques are used to improve the power transfer capacity in the transmission lines. Controlling the voltage profile along the line helps to control the transmittable power and this is achieved through compensation techniques. In this paper, different line models are used for the estimated power transmitted in the line both with and without shunt compensation. It is observed that with the Bergeron line model and PI-section model the estimated power is higher compared to that with the series RL model both with and without shunt compensation. PSCAD is used for the simulation.

Real‐time implementation of active shunt compensator with adaptive SRLMMN control technique for power quality improvement in the distribution system

In this work, the development of sign regressor least mean mixed norm (SRLMMN) control technique for a distribution static compensator (D-STATCOM) is presented. This control technique extracts fundamental weight components from the non-sinusoidal load currents and generates reference grid currents. D-STATCOM is developed for harmonics eradication, reactive power injection and load balancing and its performance is investigated in several operating modes. The performance of SRLMMN control is compared with recursive least square (RLS) and variable step least mean square (VSLMS) control techniques in terms of convergence, steady-state error, harmonics elimination, sample time and computation complexity. The major advantages of SRLMMN control technique, are fast convergence, less steady-state error, low total harmonic distortion (THD) and offers less computation complexity when compared with RLS and VSLMS. A laboratory-scale prototype of compensator is realised using a voltage source converter with the controller implemented in the dSPACE-MicroLabBox. Both MATLAB simulation and experimental results are included to demonstrate the performance of shunt compensator under steady-state and dynamic loadings. The developed SRLMMN control technique mitigates power quality problems and effectively suppresses THD observed in the grid current with reference to IEEE Standard 519-2014.

Performance of Interline Unified Power Quality Conditioner IUPQC With PI, Fuzzy and ANFIS Controllers

Several artificial intelligent control schemes are highly used in several applications, in that ANFIS controller has been greatly recognized due to enhanced performance over the classical PI and Fuzzy controllers. At present the multi-feeder power distribution system is deteriorated with continuity of supply and poor power quality standards. In this multi-feeder distribution system, it is a regular consumer related issue which is acquired due to malfunctioning of massive non-linear loads. These loads create the voltage or current imperfections on distribution networks which disrupts the power quality of distribution system. An efficient and reliable active compensation scheme is used for attaining enhanced power quality features at PCC of multi-feeder distribution system with effective control functions. The Multi-Feeder Unified Power Quality Compensator (MF-UPQC) is optimal choice for attaining enhanced power quality features and it is a combined shunt or series compensator driven by common DC-link. This paper recommends the Adaptive Neuro-Fuzzy Intelligent Controller (ANFIS) based prediction technique for generation of optimal switching states to enhance performance of proposed MF-UPQC to compensate all voltage-current PQ imperfections. The performance of proposed MF-UPQC is verified by classical PI, Fuzzy and proposed ANFIS control functions by using MATLAB/SIMULINK tool and results are conferred with proper comparisons.

A Machine Learning Approach for Coordinated Voltage and Reactive Power Control

Increasing penetration of renewable energy sources in form of distributed generators has brought many technical challenges to distribution networks. Among those, voltage and reactive power control should be revised and improved. Existing and new control resources should be coordinated based on real-time information and in closed loop. To achieve this, machine learning (ML) can be used to map the relationship between the selected network information and the desired control output. In this paper, setting of the shunt compensator operating in capacitive or inductive modes is coordinated with the tap position of substation transformer by the developed ML. Dataset emulating network behaviour during a year operation is constructed for training ML. A multi-class classification problem is formulated. Simulation results show satisfactory accuracy for some classes.

Mitigation of power quality issues for grid connected photo voltaic system using soft computing techniques

Now a days Alternating Current distribution and transmission systems are suffering from many power qualities issues, mainly due to the presence of complex equipment in the residential, commercial, industrial applications. Power quality issues in distribution systems are classified as current-based and voltage-based quality problems. Complex Power Devices and distribution static compensators (D-STATCOM) are used to compensate for current-based power issues. The number of current-based power quality problems are unbalanced currents, undesired power factor, increased neutral current, and poor voltage regulation. Therefore, depending upon the problem, the configuration of the DSTATCOM is selected in the practice. This paper focuses on the control algorithms: Lorentzian adaptive filter, discrete adaptive filter, neural network least mean square and quasi newton control algorithms, for controlling shunt compensator (D-STATCOM) for compensating power issues, reactive power, unity power factor and load balancing under linear and non-linear load conditions with zero voltage regulation by maintaining constant capacitor voltage (VDC) and eliminate harmonic currents at point of common coupling by proportional-integral controller. In the proposed system MPPT is obtained by DC converter and the power quality issues are further analyzed in the existence of harmonics either in the currents or voltages. The DSTATCOM-control algorithms based solar Photo Voltaic system is simulated in MATLAB along with SIMULINK.