Power Quality Improvement Features Research Articles

Power Quality Analysis by H-Bridge DSTATCOM Control by Icosθ and ESRF SOGI-FLL Methods for Different Industrial Loads

This work develops the analysis of power quality by the H-bridge Static Distribution Compensator (DSTATCOM) as well as its control techniques in different industry-based loading conditions. The function of DSTATCOM is to diminish power quality problems arising due to commercial as well as industrial loads. For reference current extraction, the novel Icosθ and proposed enhanced SRF SOGI-FLL (synchronous reference frame second-order generalized integrator frequency-locked loop) controller have been adopted in the H-bridge DSTATCOM. The Icosθ controller’s performance is dependent on the in-phase and quadrature-phase angle, which changes accordingly as load changes, whereas the proposed enhanced SRF SOGI-FLL controller works in synchronization with the grid with an inverter. The two control techniques were compared in terms of balancing, power factor improvement, DC-link voltage control, and harmonic minimization. The harmonics minimization of the proposed controller has been validated by IEEE 519 standards. The extracted reference currents are fed to the hysteresis current controller for the generation of pulses toward the inverter switches of DSTATCOM. The DSTATCOM system along with control algorithms have been tested on various loading conditions, i.e., voltage source- and current source-based non-linear loads, induction heating-based loads, and electric arc furnace. The complete DSTATCOM systems were implemented and executed in the MATLAB/Simulink platform and then power quality improvement features were investigated.

Design and implementation of model predictive control for microgrid energy system with power quality improvement features

ABSTRACT The harmful outcome of fossil fuel emission and growing concern about the deficiency of power resources has started a new requirement of cleaner, reliable, and sustainable energy resources. Thus, wind power and solar energy based systems are the best emerging energy sources amongst the various renewable energy resources. The proposed system involves a boost converter with an inverter circuit, where first solar and wind energy is regulated, and the inverter is employed for grid integration. In the proposed work, model predictive control is applied to a 3-phase inverter and it uses a model to estimate the predictions of upcoming values of the system voltage for a provided sequence of voltages. Further, the cosine firing angle arrangement is also used for adjusting the output voltage of the boost converter. The three-phase inverter is also employed as a harmonic reduction device, this allows the utility grid to continuously supply or absorb the good quality of power. The proposed approach escapes the use of nonlinear and linear controllers and it does not include the modulator, hence this is a simple method and the control algorithm is easy to implement. The outcomes show that the planned scheme has excellent performance.

Weak Grid Integration of a Single-Stage Solar Energy Conversion System With Power Quality Improvement Features Under Varied Operating Conditions

A three-phase single-stage solar energy conversion system (SECS) integrated into a weak distribution network is presented. The grid integration and maximum power point operation of the photovoltaic (PV) array are achieved by a voltage source converter. The SECS is capable of feeding distortion-free and balanced grid currents with power factor correction, even at adverse grid side, PV array side, and load side operating conditions. The integration of SECS into the weak grid having distorted, unbalanced, and varying grid voltages is achieved while maintaining the power quality. The dc offset introduced in the sensed grid voltages is also effectively eliminated. For swift system response to changes in load currents, their fundamental weights are swiftly extracted. In the absence of solar irradiance, the power is imported from the utility to supply the local loads, and the system continues to execute its power quality improvement functions. In case of loss of PV power or large voltage deviations, the dc-link voltage is adaptively varied according to the grid voltage changes, increasing system reliability, and reducing operating losses. The efficacy of the SECS is validated through test results at different operating scenarios.

Leakage Current Suppression in Double Stage SECS Enabling Harmonics Suppression Capabilities

This work deals with a harmonic control strategy for a transformerless double stage solar energy conversion system (SECS) to alleviate the leakage current in the presence of nonlinear loads enabling harmonics suppression capability. In this SECS, the PV module stray capacitance can elicit leakage current, which causes electromagnetic interferences and potential safety problems. To address these issues, the model predictive controller based adaptive harmonic compensation strategy is presented herein, which not only provides leakage current suppression but it also serves manifold ancillary power quality improvement features. The revised IEEE-519-2014 standard is incorporated in adaptive harmonic compensation strategy to achieve harmonics within recommended limits. The comparative response with a conventional control is exhibited to verify the capabilities of harmonic control strategy. Furthermore, a comparative harmonic suppression capability is analyzed herein to validate the competence of voltage controller. Various real-time simulated results are discussed to manifest capabilities of this control. The leakage current is restricted below 300 mA as per desirable safety requirements against leakage current of VDE-00126-01 and IEC-62109-2 standards. The total harmonic distortion (THD) of grid current and voltage, are achieved within permissible limits in compliance with the revised IEEE-519-2014 code.

Fault Ride-Through Strategy for Two-Stage Grid-Connected Photovoltaic System Enabling Load Compensation Capabilities

This paper proposes an extended Kalman filter (EKF) based control strategy for fault ride-through operation in two-stage grid-connected photovoltaic (GPV) system. Unlike the conventional controllers for ride-through operation, the proposed strategy does not compromise with power quality improvement features in the system while enabling ride-through operation. The controller accounts for nonlinear loads in the system, grid harmonic-currents elimination, and grid-currents balancing even during the harmonic/distorted grid voltages. The IEEE Standard-1547.4 compels the distributed resource to ride-through during voltage disturbances caused by faults. For the ride-through operation, a limit is imposed on PV active power injection to prevent inverter overcurrents and dc-link energy aggregation, which reduces the lifetime of dc-link capacitor. The reactive power is fed to the grid, as per the depth in voltage-sag. The derated PV array power is supplied in cases where the inverter cannot handle the utmost PV-power. The power quality improvement is ensured using EKF state estimator, which precisely estimates the fundamental load currents. In distribution network with modern nonlinear loads, especially at far radial ends, the grid voltages are prone to huge diversions and the proposed controller provides a possible solution to maintain active/reactive power support and maintain power quality in the network. The effectiveness of the strategy is demonstrated through simulations and experiments. Under all disturbances, the harmonic content in grid currents is observed within limits, in accordance with the IEEE Standard-519.

Fixed- and variable-frequency sliding mode controller–maximum power point tracking converter for two-stage grid-integrated photovoltaic system employing nonlinear loads with power quality improvement features

This article presents a reliable and efficient photovoltaic sliding mode voltage-controlled maximum power point tracking DC-DC converter–active power filter integration system to supply real power to grid. This integrated active power filter system performs power quality enhancement features to compensate current harmonics to make distortion-free grid supply current and reactive power employing nonlinear loads. The proposed proportional–integral–derivative–based sliding mode controller is designed with fixed-frequency pulse-width modulation based on equivalent control approach. The main objective of this paper is to design a photovoltaic system with a new sliding surface to force the photovoltaic voltage to follow the reference maximum power point voltage with the alleviation of slow transient response and disadvantages of chattering effects of variable-frequency hysteresis modulation sliding mode controller–maximum power point tracking. The perturbations caused by the uncertainties in climatic conditions and converter output bulk oscillations during grid integration are also mitigated. The features of the proposed photovoltaic–active power filter integration system are confirmed at different operating conditions through PSIM simulation software, and its performance is also compared with a conventional variable-frequency sliding mode-controlled maximum power point tracking. The obtained simulation and experimental results give good dynamic response under various operating conditions of environmental and local load conditions.

Seamless Operation and Control of Single-Phase Hybrid PV-BES-Utility Synchronized System

This paper presents the control of a single-phase photovoltaic (PV) battery energy storage (BES) based hybrid system with seamless transfer and power quality (PQ) improvement features. The PV-BES based single-phase system provides uninterruptable power to the dedicated nonlinear loads even under utility outage by transferring smoothly to the islanding. Therefore, the smooth transfer from the grid integrated operation to the islanding and vice versa provides high reliability of the system than the conventional system. To control the proposed synchronized system in the grid integrated mode, a learning quantization (LQ) based current control with PV feed-forward (PVFF) loop is used. The LQ current control extracts the net active component of load current. Moreover, PVFF is included in the LQ control to reflect the PV power contribution in the utility, which also improved the fast tracking ability of the proposed control under variable climate conditions. In islanding operation, the load voltage is regulated by the voltage control. The effectiveness of the LQ-based current control for a single-phase PV-BES-utility synchronized system is demonstrated through the simulated as well as experimental results.

Grid interconnection of renewable energy sources at distribution level with power quality improvement features

As there is increase in load demand, the Renewable Energy Resources (RES) are increasingly connected in the distribution systems which utilizes power electronic Converters or inverters. In this project, grid interfacing inverter is installed in three phase four wire distribution systems. The use of non-linear loads in the power system will lead to the generation of current harmonics which in turn deteriorates the power quality. Hence, Active Power Filters (APF) (5) are extensively used to compensate the current harmonics and load unbalance. The inverter can be controlled to perform as a multi-function device by incorporating active power filter functionality. Thus the existing inverter acts as a Shunt Active Power Filter that is capable of simultaneously compensating problems like current unbalance current harmonics and also of injecting the energy generated by renewable energy source. The inverter is controlled on the basis of hysteresis control and thus it can be utilized as a power converter injecting power generated from renewable energy resource to the grid and as a shunt active power filter to compensate the load disturbances. KEYWORD: Renewable energy resources (RES), Active power filter (APF), distributed generation (DG), distribution system, grid interconnection, power quality (PQ), renewable energy.

Result Analysis of Power Quality Improvement Features for Grid-Connected Space Vector Pulse Width Modulation Features

Result Analysis of Power Quality Improvement Features for Grid-Connected Space Vector Pulse Width Modulation Features

Multifunctional Capabilities of Grid Connected Distributed Generation System with Non‐Linear Loads

AbstractThis paper deals with the integration of distribution energy resource (DER) connected to a three‐phase grid connected system feeding a variety of loads. The DER is controlled to provide power quality improvement capabilities viz. power factor correction, harmonic reduction, voltage regulation, and load balancing, and it is realized as a voltage source converter (VSC). The developed controller is based on Synchronous Reference Frame (SRF) Theory and an energy based controller that also includes additional features viz. filtration of fundamental voltage extracted from the polluted utility grid voltages. This new controller, realized as an energy controller, is implemented over the square of the DC link voltage of the DER. The control algorithm has been tested for several power quality improvement features and works well for power factor correction, voltage regulation, harmonic reduction, and operation under unbalanced load conditions. Extensive simulation and hardware results are demonstrated on a prototype developed in the laboratory.

A Grid-Connected Dual Voltage Source Inverter With Power Quality Improvement Features

This paper presents a dual voltage source inverter (DVSI) scheme to enhance the power quality and reliability of the microgrid system. The proposed scheme is comprised of two inverters, which enables the microgrid to exchange power generated by the distributed energy resources (DERs) and also to compensate the local unbalanced and nonlinear load. The control algorithms are developed based on instantaneous symmetrical component theory (ISCT) to operate DVSI in grid sharing and grid injecting modes. The proposed scheme has increased reliability, lower bandwidth requirement of the main inverter, lower cost due to reduction in filter size, and better utilization of microgrid power while using reduced dc-link voltage rating for the main inverter. These features make the DVSI scheme a promising option for microgrid supplying sensitive loads. The topology and control algorithm are validated through extensive simulation and experimental results.

Power Quality Improvement Features for a Distributed Generation System using Shunt Active Power Filter

Electric utilities and end users of electric power are becoming increasingly concerned about meeting the growing energy demand. Renewable energy source (RES) form an invincible part of electric power distribution. Wind energy which forms one of the major available renewable energy sources. In this paper a grid interfacing inverter is designed which acts as a power converter to inject power generating from RES to grid and also act as Shunt Active Power Filter (SAPF) to minimize the harmonics, load neutral current. A new control approach named Unit Vector Template Generation (UVTG) is designed for SAPF and presented in this paper. The simulation has been done for three phase four wire (3P4W) distribution system.

Grid Interconnection of Renewable Energy Sources at the Distribution Level With Power-Quality Improvement Features

Renewable energy resources (RES) are being increasingly connected in distribution systems utilizing power electronic converters. This paper presents a novel control strategy for achieving maximum benefits from these grid-interfacing inverters when installed in 3-phase 4-wire distribution systems. The inverter is controlled to perform as a multi-function device by incorporating active power filter functionality. The inverter can thus be utilized as: 1) power converter to inject power generated from RES to the grid, and 2) shunt APF to compensate current unbalance, load current harmonics, load reactive power demand and load neutral current. All of these functions may be accomplished either individually or simultaneously. With such a control, the combination of grid-interfacing inverter and the 3-phase 4-wire linear/non-linear unbalanced load at point of common coupling appears as balanced linear load to the grid. This new control concept is demonstrated with extensive MATLAB/Simulink simulation studies and validated through digital signal processor-based laboratory experimental results.