Control For Power Quality Improvement Research Articles

An SVC controller for Power Quality Improvement of a Heavily Loaded Grid

Pakistan is faced with energy crises from the last two decades. Generation cannot balance the load demands of the electricity consumers. Power delivery systems are generally old-fashioned and overloaded. They are unable to provide consistent and uninterrupted supply to commercial, industrial, and domestic loads. Generally speaking, the Power Systems consist of loads that are inductive and resistive in nature. Heavy machinery, induction motors, and arc furnaces are heavily inductive in nature. Inductive loads when operated in a weak power system results in lagging VARs (Volt Ampere Reactive) and poor voltage regulation, which must be balanced by the same number of leading VARs in order to ensure unity power factor and thus helps in improving the voltage profile. At times the reactive VARs injected may not be sufficient to balance the VARs requires by the system, but still the power factor is improved up to some extent. In hot and humid climatic conditions, air-cooling system and chillers greatly burdens the grids. Such loads require excessive reactive VARs, and if not offered with ample reactive power, causes severe voltage drops in distribution system. To manage low voltages and power-factor, household users use automatic voltage regulators while industries connect capacitor banks. Voltage regulators control output voltage within the required limits at the expense of excessive line current from transformer, which may overburden it. Moreover, with each operation of tap changer, current rises which further intensifies line losses. Static capacitors provide stable voltage but repeated variations in load demands reliable and vigorous voltage regulation. This investigation aims to come up with a power quality improvement scheme which would deliver instantaneous control of power (reactive) with SVC (Static VAR Compensator) thus overcoming the shortcomings of step-wise banks of capacitors and or voltage regulators. Simulation work is carried out in MATLAB/SIMULINK and the results are compliance with IEEE Standards for SVCs. The device can offer steady state as well as dynamic VAR compensation under changing load conditions. Result showed considerable improvement both in terms of response time and power factor. Switching time has been improved to less than 1/10th fraction of a second which in previous simulations was 0.7 seconds approximately. Initial power factor without disturbance and without compensation was recorded to be 0.6 lagging, which after compensation was improved to 0.95 lagging. Similarly, in presence of disturbance without compensation the power factor fluctuated between 0.55 and 0.9 lagging, which after compensation was improved to 0.95 lagging and above throughout the course of operation.

Fuzzy with Hysteresis Controller for Power Quality Improvement of Grid Interconnected System

The grid connected distribution systems are providing the energy to the load from the grid. During the period of energy transmission, the issues are occurred on the power quality in transmission line. In the power system, the power quality issues are occurred due to the following issues as instability of the system, voltage sag, harmonic distortion, over voltage, unbalanced voltage etc. In this paper, the power quality improvement is designed using the inverter which compensates the voltage and current when the fault occurred. This inverter is used to inject the power using a DC source. This improvement of power quality is controlled by the hysteresis controller with fuzzy logic control. The feedback is given to the controller which reduces the error from the system and provides the control variables to the inverter terms of switching gate signals.

BD‐VSS individual weighting factor sign based adaptive filter control for power quality improvement in weak distribution grid

This study presents the control of distribution static compensator (DSTATCOM) using band-dependent variable step size (BD-VSS) individual weighting factor with sign error based adaptive filter for power quality improvement in a weak distribution grid. Here, the proposed algorithm is used for estimation of fundamental active weight components from the distorted load currents in order to generate the reference grid currents to mitigate the grid currents power quality issues. This new control algorithm is proposed for fast and accurate estimation of active weight components with low steady-state error, without dynamic oscillation at fast convergence speed. Moreover, the frequency locked loop-double self-tuning second-order generalised integrator based voltage filter is used to extract the positive sequence voltages of the distorted grid voltages for estimating the harmonics, and noise-free voltage unit templates. Therefore, the DSTATCOM with the proposed control algorithm is capable of mitigating the harmonic currents, providing reactive power compensation and operating at unity power factor in a weak distribution grid. Test results demonstrate the viability and robustness of the proposed control algorithm under balanced and unbalanced non-linear load conditions.

Experimental Validation of Modified Adaptive Fuzzy Control for Power Quality Improvement

This study aims to present a modified adaptive fuzzy control (MAFC) for power quality improvement, whereby adaptive fuzzy control with parameter adaptive capability is employed to emulate optimal control. Different from conventional fuzzy control-based current control method without analytical tools to guarantee basic performance criteria, high-performance control system can be realized using Lyapunov-based adaptive fuzzy control. Also, in order to compensate the fuzzy approximation error (FAE) in conventional fuzzy control, a modified adaptive fuzzy control with adaptive compensator is developed. Unlike the existing approaches, adaptive compensator can estimate the optimal value of FAE with no need of upper bound of FAE. Simulation and experimental results verify that proposed control strategies reveal superior performance under different conditions.

Recursive Digital Filter Based Control for Power Quality Improvement of Grid Tied Solar PV System

This article deals with the implementation of a control approach for an active power transfer between solar photovoltaic (PV) array and the grid/ load along-with power quality (PQ) improvement by eliminating harmonics and compensating reactive power required by the load in the distribution network. The PQ problems at the point of intersection, are increasing preeminently with respect to voltage and current harmonics due to integration of renewable sources. The recursive digital filter control implemented here for PV grid interfaced system is efficient in improving PQ indices by operating round the clock and ensuring power transfer between utility grid and connected loads. The prominence of the control algorithm lies in the efficient switching of voltage source converter (VSC), by generating reference grid currents, which are obtained through indirect current control technique. The recursive digital filter is utilized for processing the load currents and extracting the active power component of them. These active power components of load currents are used for generating the reference grid currents in this system. A prototype of the system is developed in the laboratory and its performance is studied for varying loads, changing solar insolation, and voltage swell, voltage sag and voltage distortion conditions.

Kalman filter variant intelligent control for power quality improvement in photovoltaic active power filter system

Kalman filter variant intelligent control for power quality improvement in photovoltaic active power filter system

LMMN-Based Adaptive Control for Power Quality Improvement of Grid Intertie Wind–PV System

A new topology comprising of wind-turbine-driven synchronous generator (SG) and solar photovoltaic (PV) array for renewable energy harvesting is proposed in this paper. The stochastic inputs for the proposed system are agitated using nonlinear time-dependent parameters such as varying wind speed and changing solar insolation. The speed variations are absorbed using back-to-back interfaced power electronic converters (PECs), namely, SG side converter (SGC) and utility grid side converter (UGC) with a common dc link where a solar PV array is tied directly. The power injection into the utility grid is leveled by the optimal utilization of the PECs. The SGC uses vector control (VC) for speed control of the SG and maintains unity power factor (UPF) at stator terminals. UGC acquires its switching pulses with proper application of least mean mixed-norm (LMMN) control technique. The new application of LMMN control scheme is used for the compensation of harmonics and for the extraction of fundamental load component. The dc-link voltage is regulated using a proportional integral controller. A prototype is developed and tested under different conditions of sudden changes in load, wind-velocity variations, and varying solar PV insolation. The power sharing scheme proves to be effective. The power quality issues are also addressed and mitigated effectively. The performance is exhibited for the validation of the proposed system and its control.

Unbiased Circular Leakage Centered Adaptive Filtering Control For Power Quality Improvement of Wind–Solar PV Energy Conversion System

The hybrid renewable energy conversion systems and their increased penetration into the utility grid are intensifying the power quality (PQ) issues especially in the form of increased total harmonic distortion of voltages and currents at point of common coupling. The objective of the proposed grid-tied wind–solar photovoltaic (PV) energy conversion system is to analyze PQ issues and to mitigate them by utilizing the unbiased circular leakage centered (UCLC) adaptive filtering control. An implementation of UCLC adaptive control improves the PQ indices and system performance by overcoming the intermittency issues associated with solar and wind energies. UCLC adaptive control effectively extracts the fundamental load current component and mitigates the grid current harmonics. It has simple structure, enhanced convergence rate, and better performance with noise corrupted input and output signals. It effectively resolves the weight drift problem depicted by the conventional least mean square (LMS) control and leaky LMS control algorithm by avoiding biased estimates. The averaging theory and the deterministic stability analysis provide the relying facts of the performance of UCLC adaptive control. The extraction of maximum power from solar PV array energy and wind generation is carried out by perturb and observe scheme. A prototype is made in the laboratory and verified for environmental variations of solar insolation level, wind speed, and perturbing load demand. The PQ issues are effectively alleviated. Test results confirm the effective performance of the proposed system.

An Intelligent Battery Energy Storage-Based Controller for Power Quality Improvement in Microgrids

Modern power systems rely on renewable energy sources and distributed generation systems more than ever before; the combination of those two along with advanced energy storage systems contributed widely to the development of microgrids (MGs). One of the significant technical challenges in MG applications is to improve the power quality of the system subjected to unknown disturbances. Hence innovative control strategies are vital to cope with the problem. In this paper, an innovative online intelligent energy storage-based controller is proposed to improve the power quality of a MG system; in particular, voltage and frequency regulation at steady state conditions are targeted. The MG system under consideration in this paper consists of two distributed generators, a diesel synchronous generator, and a photovoltaic power system integrated with a battery energy storage system. The proposed control approach is based on hybrid differential evolution optimization (DEO) and artificial neural networks (ANNs). The controller parameters have been optimized under several operating conditions. The obtained input and output patterns are consequently used to train the ANNs in order to perform an online tuning for the controller parameters. Finally, the proposed DEO-ANN methodology has been evaluated under random disturbances, and its performance is compared with a benchmark controller.

Real-Time Supervisory Control for Power Quality Improvement of Multi-Area Microgrids

In this paper, the power quality (PQ) improvement of multi-area microgrids (MAMGs) is addressed. To this aim, mitigation of voltage harmonics and unbalance is considered by using distributed generators (DGs) and active power filters (APFs) in a proper way. As a novel approach, the main goal of the proposed method is to pick out redundant APFs and/or significantly reduce of DGs and APFs compensation workload by making collaboration between areas toward integrated PQ improvement of the MAMG. To achieve the desired PQ indices of different areas, supervisory control is planned for proper utilization of available compensators in time. By supervisory control, harmonic propagation between areas and the system unbalance are dealt with and systemic PQ improvement of the MAMG is provided. To this aim, scheduling framework is used to track the PQ situation of each area. Evaluation of the proposed control is carried out by a comprehensive simulation study in MATLAB/Simulink.

Photovoltaic tied unified power quality conditioner topology based on a novel notch filter utilized control algorithm for power quality improvement

Nonlinear loads and grid side disturbances in the power distribution network cause harmonic rich currents and voltage perturbations such as voltage harmonics, voltage sags and voltage swells. The unified power quality conditioner (UPQC) with shunt inverter and series inverter are usually employed for elimination of current and voltage related power quality issues. However, elimination of voltage and current quality issues in a grid connected Photovoltaic (PV) system is essential. Therefore, PV integrated UPQC topology is proposed in this paper with a novel controller for power quality improvement. The control algorithm based on notch filter Phase Locked Loop (PLL) is utilized for proper phase detection and elimination of voltage and current disturbances. PV tied UPQC controller based on notch filter PLL has the capability to avoid multiple zero crossing during highly distorted grid voltage condition. Conventional control algorithms such as synchronous reference frame theory, unit vector controller based on traditional PLL are also analyzed for the control of PV tied UPQC. The proposed system is developed in Matlab/Simulink and the results obtained are evaluated to measure the performance. A real-time hardware prototype is developed using dSPACE processor. The obtained experimental results validate the efficiency of the proposed controller for PV tied UPQC.

A Distribution Static Compensator Using a CFNN-AMF Controller for Power Quality Improvement and DC-Link Voltage Regulation

A distribution static compensator (DSTATCOM) is proposed in this study to improve the power quality, which includes the total harmonic distortion (THD) of the grid current and power factor (PF), of a mini grid with nonlinear and linear inductive loads. Moreover, the DC-link voltage regulation control of the DSTATCOM is essential especially under load variation conditions. Therefore, to improve the power quality and keep the DC-link voltage of the DSTATCOM constant under the variation of nonlinear and linear loads effectively, the traditional proportional-integral (PI) controller is substituted with a new online trained compensatory fuzzy neural network with an asymmetric membership function (CFNN-AMF) controller. In the proposed CFNN-AMF, the compensatory parameter to integrate pessimistic and optimistic operations of fuzzy systems is embedded in the CFNN. Furthermore, the dimensions of the Gaussian membership functions are directly extended to AMFs for the optimization of the fuzzy rules and the upgrade of learning ability of the networks. In addition, the network structure and online learning algorithm of the proposed CFNN-AMF are introduced in detail. Finally, the effectiveness and feasibility of the DSTATCOM using the proposed CFNN-AMF controller to improve the power quality and maintain the constant DC-link voltage under the change of nonlinear and linear inductive loads have been demonstrated by some experimental results.

Fuzzy‐supervisory control of a hybrid system to improve contractual grid support with fuzzy proportional–derivative and integral control for power quality improvement

This paper investigates on an additional active power compensation of a microgrid to a weak grid using fuzzy-supervisory control. This reduces the economic penalty of microgrid for going over-contract with the grid in terms of power demand. The objectives of this work are (a) to maximise grid support during periods of over-contract, (b) to minimise distortions and increase dynamic stability of dc link voltage and (c) to improve the total harmonic distortion (THD) of the dispatched power. The microgrid comprises of a wind energy conversion system (WECS) and Li-ion battery energy storage system (BESS). During variations in wind speed, power feed into the point of common coupling (PCC) depends upon deviations in the wind power, dc link voltage, violations in grid contract power and the state of charge (SOC) of the battery. The deviations in these inputs are utilised by the supervisory controller to compute additional power support to the grid, by discharging the battery. Performances of the fuzzy-supervisory controller are compared with a classical-supervisory controller with similar power dispatch parameters. Further, inverter currents are regulated using a fuzzy proportional-derivative and integral (FPD + I) controller to reduce distortions and improve dynamic response of the dispatched power.

Performance Comparison of L-UPQC and R-UPQC with FUZZY logic Controller for Power Quality Improvement

Performance Comparison of L-UPQC and R-UPQC with FUZZY logic Controller for Power Quality Improvement

A multi-function grid-connected PV system based on fuzzy logic controller for power quality improvement

A multi-function grid-connected PV system based on fuzzy logic controller for power quality improvement

Robust control of shunt active power filter using interval type-2 fuzzy logic controller for power quality improvement

Robust control of shunt active power filter using interval type-2 fuzzy logic controller for power quality improvement

Simulation and performance evaluation of shunt hybrid power filter using fuzzy logic based non-linear control for power quality improvement

This paper deals with design and simulation of a three-phase shunt hybrid power filter consisting of a pair of 5th and 7th selective harmonic elimination passive power filters connected in series with a conventional active power filter with reduced kVA rating. The objective is to enhance the power quality in a distribution network feeding variety of non-linear, time-varying and unbalanced loads. The theory and modelling of the entire power circuit in terms of synchronously rotating reference frame and leading to a non-linear control scheme is presented. This work involves introduction of individual fuzzy logic controllers for d and q axis current control and for voltage regulation of the DC link capacitor. The simulation schematic covering the power and control circuits have been developed taking into account severe harmonic distortion caused by non-linear and unbalanced loads. The effectiveness of the fuzzy logic controller for the compensation of harmonics and reactive power has been verified by successive simulation runs and analysis of the results. The proposed controller is also able to compensate the distortion generated by the voltage- and current-fed non-linear loads, unbalanced and dynamically varying loads. Further, excellent regulation of the DC link voltage is accomplished, which significantly contributes to improvement of power quality.

Implementation of Echo-State Network-Based Control for Power Quality Improvement

This paper proposes a new control algorithm for mitigation of power quality problems at the distribution level. The control algorithm is designed on the basis of echo-state network, which is a type of recurrent neural network. This technique is used to extract fundamental weight components from nonsinusoidal load currents. These weight components are used to evaluate reference grid currents and consequently generate switching logic for the voltage source converter used in the active filter. The shunt-connected active filter with the proposed control algorithm is used to overcome several current-related power quality problems and provides the load compensation. Problems such as the presence of lower order harmonics, insufficient reactive power, and load unbalancing are corrected using a shunt filter in both the power factor correction and voltage regulation modes. The proposed control algorithm is validated on a real time system which is a prototype of a shunt filter. The algorithm is tested in MATLAB using Sim Power Systems and SIMULINK and implemented on a digital signal processor.

A New Real Time Lyapunov Based Controller for Power Quality Improvement in Unified Power Flow Controllers Using Direct Matrix Converters

This paper proposes a Direct Matrix Converter operating as a Unified Power Flow Controller (DMC-UPFC) with an advanced control method for UPFC, based on the Lyapunov direct method, presenting good results in power quality assessment. This control method is used for real-time calculation of the appropriate matrix switching state, determining which switching state should be applied in the following sampling period. The control strategy takes into account active and reactive power flow references to choose the vector converter closest to the optimum. Theoretical principles for this new real-time vector modulation and control applied to the DMC-UPFC with input filter are established. The method needs DMC-UPFC dynamic equations to be solved just once in each control cycle, to find the required optimum vector, in contrast to similar control methods that need 27 vector estimations per control cycle. The designed controller’s performance was evaluated using Matlab/Simulink software. Controllers were also implemented using a digital signal processing (DSP) system and matrix hardware. Simulation and experimental results show decoupled transmission line active (P) and reactive (Q) power control with zero theoretical error tracking and fast response. Output currents and voltages show small ripple and low harmonic content.

A Power Factor-Oriented Railway Power Flow Controller for Power Quality Improvement in Electrical Railway Power System

Focusing on the freight-train dominant electrical railway power system (ERPS) mixed with ac–dc and ac–dc–ac locomotives (its power factore[0.70,0.84]), this paper proposes a power factor-oriented railway power flow controller (RPFC) for the power quality improvement of ERPS. The comprehensive relationship of the primary power factor, converter capacity, and the two-phase load currents is built in this paper. Besides, as the main contribution of this paper, the optimal compensating strategy that suited the random fluctuated two-phase loads is analyzed and designed based on a real traction substation, for the purposes of satisfying the power quality standard, enhancing RPFC's control flexibility, and decreasing converter's capacity. Finally, both the simulation and the experiment are used to validate the proposed conceive.