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Showing papers on "Voltage sag published in 2020"


Journal ArticleDOI
TL;DR: The obtained results show that the proposed controller fulfilled the recent standard requirements in mitigating power quality (PQ) events, and can increase the effort towards the development of smooth PVPP integration by optimizing the design, operation and control strategies towards high PQ and green electricity.
Abstract: The generation and integration of photovoltaic power plants (PVPPs) into the utility grid have increased dramatically over the past two decades. In this sense, and to ensure a high quality of the PVPPs generated power as well as a contribution on the power system security and stability, some of the new power quality requirements imposed by different grid codes and standards in order to regulate the installation of PVPPs and ensure the grid stability. This study aims to investigate the recent integration requirements including voltage sag, voltage flicker, harmonics, voltage unbalance, and frequency variation. Additionally, compliance controls and methods to fulfill these requirements are developed. In line with this, a large-scale three-phase grid-connected PVPP is designed. A modified inverter controller without the use of any extra device is designed to mitigate the sage incidence and achieve the low-voltage ride-through requirement. It can efficiently operate at normal conditions and once sag or faults are detected, it can change the mode of operation and inject a reactive current based on the sag depth. A dynamic voltage regulator and its controller are also designed to control the voltage flicker, fluctuation, and unbalance at the point of common coupling between the PVPP and the grid. The voltage and current harmonics are reduced below the specified limits using proper design and a RLC filter. The obtained results show that the proposed controller fulfilled the recent standard requirements in mitigating power quality (PQ) events. Thus, this study can increase the effort towards the development of smooth PVPP integration by optimizing the design, operation and control strategies towards high PQ and green electricity.

66 citations


Journal ArticleDOI
TL;DR: A closed-loop detection platform based on real-time digital simulator (RTDS) for the converter controller of a permanent magnet synchronous generator (PWSG) set is introduced, to investigate the LVRT performance of the WT system under grid voltage sag conditions.
Abstract: The large-scale application of wind power and photovoltaic power solves the energy crisis and alleviates the environmental problems caused by the use of conventional energy. However, they are at risk of being randomly tripped from the network when faced to voltage sag and severe fault events, which will lead to a sudden reduction of active power output and also complicates fault recovery process of the whole system. Moreover, it may also aggravate failures and lead to large-scale power outages, which stimulates a growing interest in analyzing the low-voltage ride-through (LVRT) capabilities of the renewable energy systems (RES) and improving the performance through developing various mathematical models and analysis tools. In this paper, a systematical overview of cause, classification of voltage sag phenomena and voltage sag emulating techniques is presented, and four voltage sag generators (VSGs) are discussed and compared, which include generator based-VSG, shunt impedance based-VSG, transformer based-VSG and full converter based-VSG. Furthermore, a closed-loop detection platform based on real-time digital simulator (RTDS) for the converter controller of a permanent magnet synchronous generator (PWSG) set is introduced, to investigate the LVRT performance of the WT system under grid voltage sag conditions. Finally, the application of VSG in RES are presented and the future research directions are also discussed.

60 citations


Journal ArticleDOI
TL;DR: A novel artificial neural network (ANN) based control approach has been proposed which can control the power quality as per IEEE/IEC standards and the proposed control methodology is validated in a realistic microgrid structure.

57 citations


Journal ArticleDOI
TL;DR: A novel finite-set model predictive control (FS-MPC) based method for VSG was studied, which validates the superior current-limiting ability and fault ride-through (FRT) capability of the proposed strategy in comparison with the existing methods.
Abstract: Distributed generations are expected to be penetrated widely and largely in the future power grid. Virtual synchronous generator (VSG) control can play a vital role to support the frequency stability of such power grid due to its virtual inertia feature. However, power quality and current control are still challenging aspects of the VSG-based distributed generators (DGs) operation under transient disturbances, such as voltage sag. In this article, a novel finite-set model predictive control (FS-MPC) based method for VSG was studied. The proposed scheme allows a multiple-input–multiple-output (MIMO) system to control voltage and current simultaneously. Under these constantly placed voltage and current constraints, the controller displayed the ability to prevent the system from overcurrent condition and to ride through fault, whereas the injection of nonsinusoidal current under the conditions of unbalanced voltage sag was suppressed. Several simulation and experimental studies were conducted, which validates the superior current-limiting ability and fault ride-through (FRT) capability of the proposed strategy in comparison with the existing methods.

48 citations


Journal ArticleDOI
TL;DR: This research work attempts to withstand and secure the effect of voltage fluctuation of grid connected hybrid PV-wind power system using Power System Computer Aided Design or Electro Magnetic Transient Design and Control software.
Abstract: Renewable energy sources; which are abundant in nature and climate friendly are the only preferable choice of the world to provide green energy. The limitation of most renewable energy sources specifically wind and solar PV is its intermittent nature which are depend on wind speed and solar irradiance respectively and this leads to power fluctuations. To compensate and protect sensitive loads from being affected by the power distribution side fluctuations and faults, dynamic voltage restorer (DVR) is commonly used. This research work attempts to withstand and secure the effect of voltage fluctuation of grid connected hybrid PV-wind power system. To do so battery and super magnetic energy storage (SMES) based DVR is used as a compensating device in case of voltage sag condition. The compensation method used is a pre-sag compensation which locks the instantaneous real time three phase voltage magnitude and angle in normal condition at the point of common coupling (PCC) and stores independently so that during a disturbance it used for compensation. Symmetrical and asymmetrical voltage sags scenario are considered and compensation is carried out using Power System Computer Aided Design or Electro Magnetic Transient Design and Control (PSCAD/EMTDC) software.

46 citations


Journal ArticleDOI
TL;DR: The transient analysis of DFIG with interval type-2 fuzzy-PI shows the improved results subjected to three-phase fault and voltage sag as desired by the grid codes.

45 citations


Journal ArticleDOI
TL;DR: It has been noted that the proposed DVR based strategy has effectively managed the voltage distortion, and a smooth compensated load voltage was achieved.
Abstract: Power Quality is an essential concern in the modern power system that can affect consumers and utility. The integration of renewable energy sources, smart grid systems and extensive use of power electronics equipment caused myriad problems in the modern electric power system. Current and voltage harmonics, voltage sag, and swell can damage the sensitive equipment. These devices are susceptible to input voltage variations created by interference with other parts of the system. Hence, in the modern age, with an increase in sensitive and expensive electronic equipment, power quality is essential for the power system's reliable and safe operation. Dynamic Voltage Restorer (DVR) is a potential Distribution Flexible AC Transmission System (D-FACTS) device widely adopted to surmount the problems of non-standard voltage, current, or frequency in the distribution grid. It injects voltages in the distribution line to maintain the voltage profile and assures constant load voltage. The simulations were conducted in MATLAB/Simulink to show the DVR-based proposed strategy's effectiveness to smooth the distorted voltage due to harmonics. A power system model with a programmable power source is used to include 3rd and 5th harmonics. The systems' response for load voltage is evaluated for with and without DVR scenarios. It has been noted that the proposed DVR based strategy has effectively managed the voltage distortion, and a smooth compensated load voltage was achieved. The load voltage THD percentage was approximately 18% and 23% with insertion 3rd and 5th harmonics in the supply voltage, respectively. The inclusion of the proposed DVR has reduced THD around less than 4% in both cases.

40 citations


Journal ArticleDOI
02 Dec 2020
TL;DR: In this article, a fault ride-through (FRT) control strategy for achieving low voltage ride through (LVRT) in single-phase grid-connected photovoltaic (PV) systems (GCPVS).
Abstract: This paper develops a fault ride-through (FRT) control strategy for achieving low voltage ride through (LVRT) in single-phase grid-connected photovoltaic (PV) systems (GCPVS). The proposed control system adapts a neural network (NN) classifier for islanding classification and model predictive control (MPC) for achieving the control of the two-stage PV system. This control scheme takes advantage of the nonlinear nature of the power converters and develops a cost function-based approach to achieve fast and efficient control. Besides, the proposed controller provides voltage support to the grid during voltage sags by injecting minimum reactive current within the threshold. The operation of the proposed control strategy is verified by performing simulation tests on a 4 kW GCPVS by creating a sag type of fault in the utility. Further, laboratory experiments were carried out with the developed controller. The results ensure that the proposed control system adheres to the grid requirements by enabling voltage support during grid faults.

37 citations


Journal ArticleDOI
TL;DR: In this article, an original hybrid unified power quality conditioner (HUPQC) topology is introduced, which consists of the shunt hybrid active power filter (SHAPF), the dynamic voltage restorer (DVR), and the isolated bidirectional dc-dc converter (BiDC) located at the common link.
Abstract: This paper introduces an original hybrid unified power quality conditioner (HUPQC) topology as an alternative solution to electrical power quality problems. The proposed HUPQC consists of the shunt hybrid active power filter (SHAPF), the dynamic voltage restorer (DVR), and the isolated bidirectional dc–dc converter (BiDC) located at the common dc link. The SHAPF enables reduction in the voltage rating of the dc-link capacitor, helps to reduce the cost and the size of the dc link, and hence reduces switching losses of the voltage source inverter. Besides the novelty of its topology, dynamic reactive power compensation capability is realized for the first time in the literature within HUPQC concept by achieving adaptively controlling dc-link voltage. The BiDC not only provides isolation and bidirectional power flow between the DVR and the SHAPF but also operates to keep the dc-link voltage of DVR constant against adaptively changing dc-link voltage of the SHAPF. In addition to these, a new hybrid voltage sag/swell detection algorithm based on the combination of the improved Clarke transformation and the enhanced phase-locked loop is developed and introduced. In order to verify the viability and effectiveness of the proposed HUPQC topology, experimental studies are carried out.

36 citations


Journal ArticleDOI
TL;DR: The proposed scheme was shown to minimize rotor over-currents, optimize the converter's performance, reduce voltage, power and torque fluctuations and protect the hybrid wind/PV system during voltage disturbances.
Abstract: This article proposes a cost effective and simple design for hybrid wind/PV systems. Its main objective is to endow the system with fault ride through capabilities in accordance to the new grid code requirements while eliminating the need for inverters for the PV units. The proposed topology connects the PV system to the DFIG's DC-link via a DC-DC converter, thus reducing cost be eliminating the need for a dedicated inverter for PV power processing. During normal conditions, the DC-DC converter controls the active power of the hybrid wind/PV system. When grid faults occur, the GSC is operated as a STATCOM, thus injecting reactive power to the grid, while the DC-DC converter controls the DC-link voltage of DFIG. To ensure optimum performance, the gains of the controllers for the RSC, GSC and DC-DC converters were auto-tuned using a fuzzy PI approach. The performance of the proposed scheme was assessed in the presence of severe single and three phase voltage sag condition, three-phase grid faults and parameter variations. Its performance was also compared to that of conventional voltage ride through approaches. The proposed scheme was shown to minimize rotor over-currents, optimize the converter's performance, reduce voltage, power and torque fluctuations and protect the hybrid wind/PV system during voltage disturbances. Additionally, it was able to support the grid by injecting reactive power during voltage sags.

35 citations


Journal ArticleDOI
TL;DR: A DPFC-based integrated hybrid system model using a fractional order PID (FOPID) controller under the unbalanced voltage conditions in the MATLAB/Simulink environment and it is shown that the developed DPFC exhibits superior performance in terms of voltage compensation and harmonics reduction.

Journal ArticleDOI
TL;DR: The control algorithm guarantees safe operation of the inverter during voltage sags by calculating the appropriate reference currents according to the equivalent impedance and the voltage sag characteristics, avoiding active power oscillations, and limiting the injected current to the maximum allowed by the inverters.
Abstract: During grid faults, the stability and reliability of the network are compromised, and the risk of a widespread disconnection of distributed generation power facilities is increased. Distributed generation inverters must support the power system to prevent this issue. Voltage support depends substantially on the currents injected into the grid and the equivalent grid impedance. This article considers these two aspects and proposes an optimal voltage-support strategy in RL grids. The control algorithm guarantees safe operation of the inverter during voltage sags by calculating the appropriate reference currents according to the equivalent impedance and the voltage sag characteristics, avoiding active power oscillations, and limiting the injected current to the maximum allowed by the inverter. Consequently, the grid can be better supported since the voltage at the point of common coupling is improved and the voltage support objectives are achieved. The proposed control strategy is validated through experimental tests in different grid scenarios. Throughout this article, it is assumed that the grid impedance is known, but the proposed solution requires calculating the grid impedance angle.

Journal ArticleDOI
TL;DR: This paper deals with a delta-bar-delta neural network (NN) control for operating optimally by feeding active power to the loads and remainingPower to the grid as a function of distribution static compensator capabilities, such as mitigating harmonics, balancing of load, and improving power factor.
Abstract: A serious concern regarding deterioration in power quality has emerged with the increasing integration of solar photovoltaic (PV) energy sources to the utility primarily in the scenario of a weak distribution grid. Therefore, power quality improvement of the grid-tied solar energy conversion system is paramount by implementation of a robust control technique. This paper deals with a delta-bar-delta neural network (NN) control for operating optimally by feeding active power to the loads and remaining power to the grid as a function of distribution static compensator capabilities, such as mitigating harmonics, balancing of load, and improving power factor. The control algorithm provides the ability to adjust weights adaptively in an independent manner, and hence, it offers alleviation in model complexity predominant during abnormal grid conditions along with reduction in computational time. Moreover, the NN-based control technique offers enhanced accuracy due to the combinational neural structure in the estimation process. In addition, the system performance according to the IEEE-519 standard has been verified; hence, it is proficient in maintaining the power quality. The solar-PV-array-efficient utilization is accomplished through an incremental-conductance-based maximum power point tracking technique. For validating the behavior of the proposed system, its performance is studied using simulation results. Moreover, a prototype is developed for validation, and experimental results corroborate reliable operation under nonideal grid conditions comprising of a wide range of load variations, voltage sag, and varying solar insolation conditions.

Journal ArticleDOI
TL;DR: The obtained results demonstrate the effectiveness of the proposed algorithms in mitigating voltage-sag and voltage-deviation problems at the system level using BESSs.

Journal ArticleDOI
TL;DR: An Artificial Neural Network controller of Dynamic Voltage Restorer (DVR) to improve the performance of a stand-alone hybrid renewable energy system that is feeding a new community located in Egypt and increases the low voltage ride through (LVRT) capability.
Abstract: This article proposes an Artificial Neural Network (ANN) controller of Dynamic Voltage Restorer (DVR) to improve the performance of a stand-alone hybrid renewable energy system that is feeding a new community located in Egypt. The hybrid system consists of three renewable energy sources, namely, solar PV cells, a wind turbines based-permanent magnet synchronous generator, and fuel cells. These three sources are tied to a common DC link by three boost converters, one for each source. The common DC link is connected to the AC side via a DC/AC inverter. The optimal size of the three proposed renewable sources is calculated using the HOMER software package. The DVR control is attained through regulating the load voltage at different anomalous working conditions. These conditions are three-phase fault, voltage sag/swell, and unbalanced loading. Two ANNs are utilized to adjust the IGBT pulses of the voltage source inverter (VSI) used to control DVR by regulating the D-Q axes voltage signals. These D-Q axes components at any loading condition represent the inputs to the two ANNs. The outputs of the two ANNs represent the IGBT pulses. The input/output data used for training ANNs are obtained by two optimized PI controllers, introduced for regulating the load voltage through DVR-VSI pulses at different abnormal operating conditions, and accordingly convert the static optimized PI controller into adaptive one based ANN. The system performance with the proposed ANN-DVR controller is enhanced through improving the current, voltage, and power waveforms of each generating source. With compensation of the faulty line voltage, the system retains an uninterrupted operation of the three renewable sources during fault events and consequently increases the low voltage ride through (LVRT) capability. Moreover, the total harmonic distortion is reduced.

Journal ArticleDOI
TL;DR: The simulation results demonstrate that the IH-UPQC is effective to perform grid voltage regulation, load harmonic current suppression and reactive power compensation.
Abstract: Voltage sag and harmonic pollution have a serious impact on the medium-voltage premium-power-supply-required park represented by optical semiconductors, data storage, precision instruments and biopharmaceuticals. Which makes existing equipment require higher voltage capacity of power electronics, higher economic cost and compensation performance. In this paper, an Inductive Hybrid Unified Power Quality Conditioner (IH-UPQC), which is characterized as high integration, reduced DC-link voltage and satisfactory harmonic isolation of transformer, is presented to realize the bi-directional power quality improvement for medium-voltage premium-power-supply-required park. First, the three-phase equivalent circuit and mathematical model are established to reveal the mechanism of harmonic suppression and voltage regulation. Based on the theoretical analysis, the compound control strategy of series and shunt Hybrid Active Power Filter (HAPF) as well as the synchronous method sliding Goertzel discrete Fourier transformation-pre-filtering Phase Lock Loop (PLL) are designed. Then, the main circuit components design including Double Resonant Passive Filter (DRPF), L-C-R low pass filter and the special designed filtering winding for implementing inductive filtering method are described. Finally, the performance of IH-UPQC is validated in 10kV distribution network by MATLAB/Simulink. The simulation results demonstrate that the IH-UPQC is effective to perform grid voltage regulation, load harmonic current suppression and reactive power compensation.

Journal ArticleDOI
TL;DR: To detect and segment, Independent Component Analysis is used, with the advantage of being fast and with low computational effort in the operational stage, once it uses only 1/8 cycle of the fundamental component.

Journal ArticleDOI
TL;DR: A detailed study on DVR with the different possible configurations of its power circuit and control techniques encircling major power quality issues is presented, ensuring optimal recital of DVR in satisfying a required quality.
Abstract: Controlled and improved power quality is one of the fundamental and essential needs in any industry driven by electric power for optimal exploitation of resources. However, in power quality, some crucial problems have been recognized as harmonic distortion, interruption, sag, swell and transient. Out of these, sag and swell are predominantly seen and cause stern impact on the electrical devices or machines and therefore require to be mitigated at an earliest to protect from any failure or mal-operation. As an ultimate key to crack these problems, some custom power devices such as distribution STATCOM (DSTATCOM), dynamic voltage restorer (DVR) and unified power quality conditioner are unanimously procured. A prominent custom power device DVR is apparently suggested in the literature for the mitigation of voltage sag and swells, with the benefit of active or/and reactive power control. The DVR is reported as being a high-performance solution to compensate voltage disturbances, since it provides both a cost-effective solution and very fast dynamics. In recent years, a bulk amount of the literature accounts for DVR on different configurations of its power circuit and various control techniques employed in it. This review article presents a detailed study on DVR with the different possible configurations of its power circuit and control techniques encircling major power quality issues. The informative object covered in the paper, articulate choice of control strategy and power circuit ensuring optimal recital of DVR in satisfying a required quality. This paper also furnishes the valued information for the investigator in this field.

Journal ArticleDOI
TL;DR: The proposed control technique makes it feasible to obtain such high-power-quality system using a conventional two-level three-phase converter composed of 12 IGBTs, with no need of extra switches, while maintaining the usual high efficiency and low cost inherent to the DFIG configuration.
Abstract: This article presents the modeling and experimental validation of a recently presented DFIG wind power system driven by a two-level three-phase converter in which the grid-side converter is connected in series with the grid. The series-grid-side converter is able to compensate for stator-voltage sags, unbalance and harmonic distortion resulting in a high-power-quality system with considerable low-voltage-ride-through capability. The proposed control technique makes it feasible to obtain such high-power-quality system using a conventional two-level three-phase converter composed of 12 IGBTs, with no need of extra switches, while maintaining the usual high efficiency and low cost inherent to the DFIG configuration. Moreover, using the proposed linear model, one can design the dc-link-voltage controller's parameters according to the desired dynamic behavior. Experimental results are presented using a 15 kW test bench, which validate the proposed control technique.

Journal ArticleDOI
TL;DR: An intelligent islanding detection method (IIDM) using an intrinsic mode function (IMF) feature-based grey wolf optimized artificial neural network (GWO-ANN) is proposed that is capable of differentiating between islanding and non-islanding events without any sensitivity under noise conditions in the test signal.
Abstract: The integration of distributed energy resources (DERs) into distribution networks is becoming increasingly important, as it supports the continued adoption of renewable power generation, combined heat and power plants, and storage systems. Nevertheless, inadvertent islanding operation is one of the major protection issues in distribution networks connected to DERs. This study proposes an intelligent islanding detection method (IIDM) using an intrinsic mode function (IMF) feature-based grey wolf optimized artificial neural network (GWO-ANN). In the proposed IIDM, the modal voltage signal is pre-processed by variational mode decomposition followed by Hilbert transform on each IMF to derive highly involved features. Then, the energy and standard deviation of IMFs are employed to train/test the GWO-ANN model for identifying the islanding operations from other non-islanding events. To evaluate the performance of the proposed IIDM, various islanding and non-islanding conditions such as faults, voltage sag, linear and nonlinear load and switching, are considered as the training and testing datasets. Moreover, the proposed IIDM is evaluated under noise conditions for the measured voltage signal. The simulation results demonstrate that the proposed IIDM is capable of differentiating between islanding and non-islanding events without any sensitivity under noise conditions in the test signal.

Journal ArticleDOI
01 Mar 2020
TL;DR: The employment of Static Synchronous Compensator (STATCOM) in reactive power compensation to enhance the Fault Ride-Through (FRT) capability and improve the dynamic performance of a grid-connected PV/wind hybrid power system during the transient grid disturbances is proposed.
Abstract: This paper proposes the employment of Static Synchronous Compensator (STATCOM) in reactive power compensation to enhance the Fault Ride-Through (FRT) capability and improve the dynamic performance of a grid-connected PV/wind hybrid power system during the transient grid disturbances. The hybrid power system consisting of 9 MW Doubly Fed Induction Generator (DFIG)-based wind farm and 1 MW PV station is integrated with 100 MVAR STATCOM at the Point of Common Coupling (PCC) bus. The dynamic performance of the PV/wind hybrid power system with the proposed STATCOM controller is analyzed and compared with another FRT control strategy during a grid voltage sag. The FRT control strategy is based on the injection of reactive power from the hybrid system to enhance the FRT capability during the grid faults, and also activation of the outer crowbar protection system to protect the DFIG. On the other hand, the proposed STATCOM controller adjusts the PCC bus voltage during the grid disturbances by dynamically controlling the amount of reactive power injected to or absorbed from the electrical grid. Modeling and simulation of the proposed hybrid power system have been implemented using MATLAB/SIMULINK software. The effectiveness of both the proposed STATCOM controller and the FRT control strategy is evaluated during a 50% grid voltage sag. The simulation results illustrate that the STATCOM controller decreases significantly the level of voltage drop during the voltage sag, maintains the injected active power from the PV station at its rated value, and protects effectively the PV DC-link voltage from overvoltage. Moreover, when the STATCOM controller is employed, the injected active power from the wind farm is improved considerably and the oscillations of the DFIG rotor speed are reduced efficiently during the fault. Furthermore, the comparison confirms the superior dynamic performance of the STATCOM controller in enhancement the FRT capability as compared with the FRT control strategy.

Journal ArticleDOI
TL;DR: An advanced reference current generator employing a combination of novel dual multi-layer fifth-order generalized integrator and adaptive differentiation frequency locked loop scheme (DMFOGI-dFLL) is proposed for mitigation of harmonics present in a grid-tied photovoltaic (PV) system.
Abstract: In this article, an advanced reference current generator employing a combination of novel dual multi-layer fifth-order generalized integrator and adaptive differentiation frequency locked loop scheme (DMFOGI-dFLL) is proposed for mitigation of harmonics present in a grid-tied photovoltaic (PV) system. The proposed DMFOGI reference current generator is utilized to separate the fundamental constituents from grid voltage distortions, sag, swell, unbalance, frequency variation, and dc offset conditions. In addition, a dFLL is implemented to estimate the system frequency adaptively at grid transient conditions, which is fed as feedback to the pre-filtering unit. Similarly, a fuzzy tuned proportional integral derivative (FPID) voltage controller is incorporated in the proposed controller to maintain the power balance between dc and ac sides by controlling the dc-link voltage. An incremental conductance (IC) control technique is additionally utilized to generate maximum power from the PV source through a boost converter. The proposed system is simulated on MATLAB/SIMULINK under various transient conditions, such as steady state, voltage sag, swell, distorted, unbalance, dynamic load, and load shedding conditions. Moreover, the overall system is developed on a laboratory prototype experimental setup. The simulation outcomes are validated through an experimental platform under above said conditions in respect of total harmonic distortion (THD) of grid current and voltages. Results of the system are found well and also maintained within the standard limits of IEEE-519.

Journal ArticleDOI
TL;DR: A hybrid multi-resonant generalized integrator-frequency locked loop (HMRGI-FLL) control structure is presented in this paper to deal with the abnormalities in grid voltage and makes the SWP system operational even under weak grid condition.
Abstract: Owing to the intermittency issue associated with renewable energy sources, a solar photovoltaic (PV) array fed grid interfaced encoder-less permanent magnet synchronous motor (PMSM) based solar water pumping (SWP) system is presented in this paper. The grid integration enables a continuous water flow regardless of available solar insolation. However, it has been observed that the grids in developing and underdeveloped countries are mostly weak. Moreover, as SWP systems are typically established at remote locations, which are generally the grid radial ends, therefore, prone to various grid abnormalities. Such abnormalities affect the SWP system performance. Therefore, a hybrid multi-resonant generalized integrator-frequency locked loop (HMRGI-FLL) control structure is presented in this paper to deal with the abnormalities in grid voltage and makes the SWP system operational even under weak grid condition. The proposed structure not only rejects the dc-offset but it also eliminates the dominant lower order harmonic with its selective harmonic elimination capability. A boost converter is used on the grid side to facilitate the power transfer from the grid. In condition of grid failure, the output water flow is regulated in accordance with available solar insolation. The speed of the PMSM is regulated using sensor-less vector control. Performance of the proposed system is experimentally validated using a laboratory prototype under varying solar insolation, during grid failure, during voltage sag, voltage swell, and distorted grid voltage conditions.

Journal ArticleDOI
TL;DR: The effectiveness of the proposed control strategy for UPQC based on dq0 detection method has been shown in maintaining load side voltage stability, maintaining power side current sinusoidal, and enhancing the power quality of the distribution network.

Journal ArticleDOI
TL;DR: The performance of the LMMN-based control of the SPV-UAPF system with series shunt compensation capabilities is demonstrated using MATLAB/Simulink-based computer simulations and hardware-in-the-loop-based experimental results under various operating conditions such as solar irradiance variation, voltage sag, swell, and current harmonics.
Abstract: This paper deals with the control of a single-phase grid-tied solar photovoltaic (SPV) power generation system with an universal active power filter (UAPF) capabilities. The SPV-UAPF system consists of series and shunt voltage-source inverters (VSIs). The shunt VSI exports the real power extracted from the photovoltaic panels to the grid and local loads. In addition to handling the real power, the shunt VSI provides compensation of reactive and harmonic currents generated by the loads. The reference signals required for the control of the shunt and series VSIs of the SPV-UAPF system are estimated using the least mean mixed-norm (LMMN) adaptive identification algorithm. The performance of the LMMN-based control of the SPV-UAPF system with series shunt compensation capabilities is demonstrated using MATLAB/Simulink-based computer simulations and hardware-in-the-loop-based experimental results under various operating conditions such as solar irradiance variation, voltage sag, swell, and current harmonics.

Journal ArticleDOI
TL;DR: The hybrid generalized integrator control is proposed for switching UGVSC and providing dc offset rejection and immunity against oscillatory errors due to subharmonics, thereby improving the power quality (PQ) and meeting the requirement of IEEE-519 standard.
Abstract: The wind energy generating system (WEGS) in this paper, aims to provide the required active peak power without high frequency fluctuations even under variable wind speed conditions. The generator speed is adjusted according to the intermittent wind speeds through two voltage source converters (VSCs) connected back to back, namely, machine-side VSC (MSVSC) and utility grid side VSC (UGVSC) across the dc-link capacitor. In this paper, the hybrid generalized integrator control is proposed for switching UGVSC and providing dc offset rejection and immunity against oscillatory errors due to subharmonics, thereby improving the power quality (PQ). Fuzzy logic controller (FLC) is implemented for the speed control of the salient pole synchronous generator (SG) driven by the wind turbine. The FLC provides the tracking of the reference speed under high overshoot transient conditions and narrow bandwidth. The switching of MSVSC is obtained by field oriented control. The dynamic performance is improved by the wind feed-forward term, which reduces the oscillation, ensuring balanced and sinusoidal grid currents. The generated power from the WEGS is fed to the grid. The weak grid conditions, namely, grid voltage unbalance, voltage sag, voltage swell, and grid voltage distortion, are considered. The performance of the system is tested on a laboratory prototype. Test results provide the effectiveness of the system with increased wind penetration and performance under weak grid conditions. Moreover, improving the PQ, the grid current total harmonic distortion meets the requirement of IEEE-519 standard, and is found to be less than 5%.

Journal ArticleDOI
TL;DR: In this article, a photovoltaic (PV) system for reliable interconnection of a PV array to the grid is presented, where a boost converter ensures operation of the PV array at its maximum power point, and it also enables the adaptive adjustment of the dc link voltage of the interfacing voltage source converter according to the variations in the grid voltages.
Abstract: A photovoltaic (PV) system for reliable interconnection of a PV array to the grid is presented in this article. A boost converter ensures operation of the PV array at its maximum power point, and it also enables the adaptive adjustment of the dc link voltage of the interfacing voltage source converter according to the variations in the grid voltages. This prevents system tripping during the voltage sag, and helps to maintain the grid current power quality at voltage swell conditions. Even in the weak grid scenarios of unbalanced or distorted voltages, the grid currents are maintained distortion free and balanced. Furthermore, the system eliminates the dc offset in the sensed grid voltages, and ensures absence of dc offset in the grid currents. The fast dynamic response of the system to sudden load variations is obtained by employing a total least squares-based control technique, which swiftly extracts the fundamental active weights from the distorted load currents. Moreover, the PV system performs grid power quality conditioning, such as neutral current mitigation, harmonics reduction, power factor correction, and balancing of grid currents, even under the absence of PV power, such as during nights. The system performance is validated by test results at unbalanced load currents, unbalanced grid voltages, distorted grid voltages, grid voltage sag and swell, PV power variations, and dc offset in the sensed grid voltage.

Journal ArticleDOI
TL;DR: A synchronous reference frame (SRF) theory based versatile control technique is presented for DVR to mitigate voltage sag problem for sensitive loads in distribution system and results show the effectiveness.

Journal ArticleDOI
TL;DR: Results show that both detection and segmentation methods have better performance than existing typical methods, and multi-dimension characteristics can be extracted from waveforms accurately, and can be implemented in power quality monitoring system to support further sag studies.
Abstract: Voltage magnitude and sag duration are known as acknowledged basic voltage sag characteristics in the last decades. However, these values cannot meet the demands of waveform analysis in the modern smart grid. Therefore, voltage sag multi-dimension characterisation is required to extract more essential information from measured waveforms. This study focuses on the unsolved issue that how to obtain required characteristics from voltage sag waveforms effectively. Overall, multi-dimension characterisation method contains several parts: voltage sag detection, segmentation and characteristics calculation. Fundamental voltage magnitude and phase angle, obtained by the proposed adaptive generalised morphology filter, are segmented in several parts. Then, a set of characteristics are calculated to characterise the voltage sag waveform in a multi-dimensional way. Performance of the proposed method is validated by synthetic and measured waveforms. Results show that both detection and segmentation methods have better performance than existing typical methods, and multi-dimension characteristics can be extracted from waveforms accurately. Moreover, the proposed method can be implemented in power quality monitoring system to support further sag studies.

Journal ArticleDOI
TL;DR: An improved multi-objective evolutionary algorithm called SPEA2+SDE (Strength Pareto Evolutionary Algorithm with shifting density estimation) is utilized to solve the proposed MOP model, so a set of Pare to optimal STATCOM allocations for voltage sag mitigation can be derived demonstrating the trade-off between two objectives and better supporting the decision-making.
Abstract: Voltage sags mitigation has become a significant concern for utilities due to the pressure from both customers and regulators recently. This paper proposes a novel multi-objective optimization formulation for STATCOM allocation problem to mitigate voltage sags. The allocation of STATCOM is formulated as a multi-objective optimization problem (MOP) with two conflicting objectives including the voltage sag performance and annual investment costs of STATCOM. To analytically evaluate the voltage sag performance in the optimization process, a mathematical voltage sag profile calculation model of power system with multiple STATCOMs is proposed and solved by nonlinear programming method. System Average RMS Variation Frequency index-X index is chosen to quantify the voltage sag performance for optimization. Sensitivity-based candidate bus selection is also performed as an essential step to reduce problem size. An improved multi-objective evolutionary algorithm (MOEA) called SPEA2+SDE (Strength Pareto Evolutionary Algorithm with shifting density estimation) is utilized to solve the proposed MOP model, so a set of Pareto optimal STATCOM allocations for voltage sag mitigation can be derived demonstrating the trade-off between two objectives and better supporting the decision-making. IEEE 30-bus system and IEEE 118-bus system are tested to demonstrate the effectiveness and feasibility of proposed method.