Compensation Of Voltage Disturbances Research Articles

Voltage disturbance compensation control of DFIG-based wind turbins during asymmetric faults in weak AC grid

Voltage disturbance compensation control of DFIG-based wind turbins during asymmetric faults in weak AC grid

Series APF based on Five and Seven-Level NPC Inverters using modified PQ Method

This paper presents the performance analysis of Series Active Power Filter (Series APF) based on five and seven-level neutral point clamped (npc) using modified instantaneous reactive power control strategy to use for harmonic and all voltage disturbances compensation. The conventional configuration based on standard voltage source inverter (VSI) with hysteresis controller presents several drawbacks such us uneven switching frequency and limited power applications. Multi-level inverters such us Five and seven-level are currently being investigated and used in various industrial applications; their advantages include the capability to reduce the harmonic content and decrease the voltage or current ratings of the semiconductors with low switching losses, low electromagnetic interference, and low acoustic noise. Fuzzy controllers are successfully employed in various industrial applications and are found more robust than conventional controllers; they represent a good alternative to classic control systems. To benefit of all these advantages two configuration of Series APF are presented in this paper adopting the same control scheme based on Phase Disposition-Sinusoidal Pulse Width Modulation (PD-SPWM) and fuzzy logic control (FLC). The proposed two series APF are evaluated using MATLAB-Simulink software and SimPowerSystem Toolbox for harmonic compensation and in case of all voltage disturbances compensation. The simulation results show the performance and the efficiency of the proposed Series APF based on seven-lever (npc) inverter in the improvement of the power quality.

Fuzzy logic controller of photovoltaic panel-unified power quality conditioner with voltage compensation and stability

<span lang="EN-US">The intensive use of non-linear loads is further contributing in the increase of power quality problems. They cause voltage distortions and current harmonics in an electrical distribution network. To minimize these problems, the unified power quality conditioner (UPQC) is used. The intermediate circuit voltage of this filter can deviate from its source during a transient event during a harmonic disturbance in voltage (voltage dip) or in current during the connection and disconnection of polluting loads. In a particular point in operating time, the stabilization of dc-bus and the compensation ability is necessary to maintain around its reference. The combination of a UPQC conditioner with a photovoltaic (PV) system connected to the intermediate element of the two converters of the DC bus (DC Link) is the adequate solution. The photovoltaic (PV) system is fitted with a fuzzy MPPT controller regulated by an algorithm (P and O) to control a boost converter. This converter is controlled by fuzzy logic related to the capacitor terminal of UPQC. The simulation results show that the UPQC conditioner based on the proposed photovoltaic system can be used for voltage disturbance compensation and the protection of non-linear loads connected to a distribution network.</span>

Simple Control Method for Unified Power Quality based on Five-level Inverter Topologies Operating under all Voltage Disturbances

This paper proposes a simple control scheme for UPQC (Unified Power Quality Conditioner) system based on five-level NPC (Neutral Point Clamped) inverter capable to compensate all disturbances under all voltage conditions. The proposed UPQC is designed by the integration of shunt and series APFs (Active Power Filters) sharing a common dc bus capacitor. The dc voltage is maintained constant using proportional integral voltage controller. To get the reference signals for shunt and series APFs, synchronous current detection method (SCD) and instantaneous reactive power (PQ) strategies are adopted. These reference signals are derived from the control algorithm and injected in LS-SPWM (Level Shifted-Sin Pulse Width Modulation) controllers to generate the switching signals. The performance of proposed UPQC system is evaluated using MATLAB-Simulink software and SimPowerSystem Toolbox for all voltage disturbances compensation. The simulation results demonstrate the effectiveness of proposed UPQC system to improve the power quality at the common connection point of the non-linear load in steady and transient conditions operation.

Stability Assessment and Enhanced Control of DFIG-Based WTs During Weak AC Grid

According to the latest grid codes, wind turbines (WTs) are required to inject certain amount of reactive and active current into the faulty grid during voltage sags. However, studies have shown that the doubly fed induction generator (DFIG)-based WTs may lose stability under weak grid condition. So the impact of grid code requirement on DFIG system stability is worthy of investigation. To address such issue, a comprehensive small-signal admittance model of DFIG system is established in this paper. Then the influence of reactive/active current settings during grid fault is analyzed in detail. Furthermore, the stable operation region is derived, considering three key factors, i.e., the current demand of grid codes, capacity of WTs and stability constraint. Besides, in order to extend the stable operation region of the DFIG system, an enhanced control strategy based on voltage disturbance compensation is put forward. Finally, simulations and experiments are performed to validate the correctness of the theoretical analysis and effectiveness of the proposed control.

Mitigation of Harmonics and Unbalanced Voltage Disturbance Compensation by MSVPWM Based- DVR in the Distribution Net

Recent power distribution networks comprise abundant sensitive loads, which extremely impact the power quality of source in electrical power networks. Voltage dip, voltage rise, imbalanced voltage, line notching and distortion of harmonics are problems of power quality frequently take place. Pre-disturbance voltage compensation strategy and phase-locked-loop (PLL) based dq- space vector control are presented to improve a Dynamic Voltage Restorer (DVR), which restore the magnitude of voltage disturbance and displacement of phase angle to prior of voltage disturbance. 3-phase Multilevel strategy of Space Vector Pulse Width Modulation (MSVPWM) based- Multilevel Diode Clamped Converter (MDCC) is proposed as switching pulse signals employed low frequency, which creates high levels of voltage and fewer harmonics in the output waveform in comparison to 2-level SVPWM based- DVR. 3-level SVPWM based- DVR under balanced and imbalanced distortion voltage disturbances included sags and swells injected appreciated quantities of voltage, thereby attained ideal sinusoidal waveform with lower Total Harmonic Distortion THD% compared to 2-level SVPWM based- DVR. Furthermore, real and imaginary powers balanced effectively at sensitive load during various distortion voltage disturbance conditions via presented work. The proposed simulation model of multi-level SVPWM based- DVR is implemented by dedicating the software system of MATLAB/SIMULINK. The results of simulation exhibit the effectiveness and efficiency of the presented work under different distortion voltage disturbance conditions.

Voltage disturbance compensation based on impedance modeling of DFIG under weak grid

This paper proposes a grid voltage disturbance compensation control for the stability of the DFIG system under weak grid conditions. A detailed impedance model of the DFIG system, including the generator, the inner and outer control loops of the rotor side converter (RSC) and grid side converter (GSC), the DC-link and phase locked loop (PLL) dynamic, is developed in the d-q synchronous reference frame. Based on the proposed model, the relationship between the outputs of the controllers and the grid voltage disturbance at the point of common coupling (PCC) can be obtained. Then, the compensation control of the grid voltage disturbance is integrated to the current controllers of RSC and GSC to improve the stability of the DFIG system connected to the weak grid. In this paper, the effectiveness of the proposed compensation control strategy is proved using the generalized Nyquist criterion (GNC), which illustrates that the compensation control strategy implemented in RSC and GSC simultaneously has a better ability to maintain the stability of the DFIG system under weak grid conditions than only one side applied. The simulation results verify the analysis.

Dynamic Voltage Restorer Integrated with Photovoltaic-Thermoelectric Generator for Voltage Disturbances Compensation and Energy Saving in Three-Phase System

The dynamic voltage restorer (DVR) combined with a photovoltaic–thermoelectric generator (PV-TEG) system is proposed for voltage disturbance compensation in the three-phase four-wire distribution system. The PV-TEG hybrid energy source is used in the DVR system to improve the system ability for deep and long-period power quality disturbance compensation. In addition, the DVR will save grid energy consumption when the hybrid PV-TEG module generates sufficient power to meet the load demand. An enhanced variable factor adaptive fuzzy logic controller (VFAFLC)-based maximum power point tracking (MPPT) control scheme is proposed to extract the maximum possible power from the PV module. Since the PV and TEG combine a hybrid energy source for generating power, the DVR can work efficiently for the voltage sag/swell, outage compensation, and energy conservation mode with minimum energy storage facilities. The in-phase compensation method and the three-leg voltage source inverter (VSI) circuit are chosen in the present system for better voltage and/or power compensation. To confirm the effectiveness of the proposed hybrid PV-TEG integrated DVR system, a simulation-based investigation is carried out with four different operational modes with MATLAB software. The study results confirm that the proposed DVR system can compensate power quality disturbances of the three-phase load with less total harmonics distortion (THD) and will also work efficiently under energy conservation mode to save grid energy consumption. Moreover, the proposed VFAFLC-based control technique performs better to achieve the maximum power point (MPP) quickly and accurately, thereby improving the efficiency of the hybrid energy module.

Control and Operation of Dynamic Voltage Restorer With Online Regulated DC-Link Capacitor in Microgrid System

This article presents a dynamic voltage restorer (DVR) topology based on the adaptive noise canceling (ANC) technique, which can be used for both voltage compensation and harmonic mitigation. Furthermore, this article aims to investigate the DVR performance when installed in a microgrid (MG) during both normal operation of the utility and during utility disturbances. One of the main objectives of this article is to reduce the cost of inverter-based DVR by reducing both the size of the dc-link capacitor and rating of switching elements. The voltage of the dc-link capacitor is regulated to low voltage level using a transformer and a pulsewidth modulation (PWM) rectifier to achieve both effective voltage regulation and drawing a sinusoidal line current from the grid and thus not to contribute to the increase of the THD of the utility current. Furthermore, the voltage across the switches can be limited to low value by an adequate design of dc-link capacitor size, capacitor voltage, and sag level to be compensated. Finally, the effectiveness and fast response of the proposed DVR for the compensation of voltage disturbances and current harmonics is confirmed by simulation using MATLAB/Simulink during the steady-state and transient operations to analyze the performance of the scheme under different operating conditions.

Dynamic Voltage Restorer With Quasi-Newton Filter-Based Control Algorithm and Optimized Values of PI Regulator Gains

In this paper, a three-phase three-wire dynamic voltage restorer (DVR) system has been chosen with quasi-Newton (QN) filter-based control algorithm. It uses Hessian matrix iteratively which is also named as QN based on modified Broyden–Fletcher–Goldfarb–Shanno (MBFGS) in each phase. The main features of this algorithm are the fundamental frequency estimation, rejection of harmonics its components, and tracking of the peak value of voltage or current. As DVR in this application has been implemented for compensation of voltage disturbances like imbalance and distortions along with voltage sag and swell, the fundamental component (FC) of the supply voltage is essential components to design control algorithm. The QN technique using MBFGS has been used for exaction of the FC from each disturbed supply voltage, which has been utilized in generating the reference load voltage. For proportional integrator (PI) regulator gains estimation, the population-based optimization technique, called as multiverse optimization (MVO), has been introduced in this paper. The MVO algorithm has adaptive coefficients which gives the benefits of smoothly maximizing the possibility of wormholes in the universe and increases the accuracy of the local search. The validation of control algorithm with optimization techniques-based PI tuning for DVR has been done using MATLAB software and real-time implementation.

Dynamic voltage restorer (DVR) in a complex voltage disturbance compensation

<p>Nowadays, a distribution network is operating in a stressful manner because of a complex voltage disturbance stirred by its nonlinear, intensified, sensitive and complex loading condition with vast proliferation of electronic equipment required for the integration of renewable energy. A distribution network that mostly inflicted by the complex voltage disturbance can be referred to as the merge of stationary voltage disturbances with a short duration voltage disturbance under a nonlinear loading condition. Therefore, the dynamic voltage restorer (DVR) integrating with the battery bank will have enough energy storage to overcome long and deep complex voltage disturbance that occurs in a distribution network installed with the photovoltaic (PV) system. The results are obtained with satisfactorily findings in compensating the complex voltage disturbance using DVR.</p>

Estimation and compensation of DC-Link voltage disturbances in a DC–DC converter for battery emulation

ABSTRACT Battery emulation is essential for reliable testing of powertrains of electric and hybrid vehicles under repeatable conditions. For that purpose, a DC voltage controller provides fast reference tracking capabilities. Due to imperfect conversion of AC current to DC current, the DC voltage source of the battery emulator does not provide constant voltage but is subject to periodic fluctuations. This disturbance is propagated through the system to the battery emulator's output. In this paper, an observer-based compensation strategy is deployed. As the structure of the multiplicative perturbation is known, it is integrated into the battery emulator model yielding a state-affine system. An appropriate observer provides asymptotically correct estimates of the disturbance, which are then used to adequately manipulate the control variable without interfering with stability properties of the closed-loop system. Simulation and experimental results show the improvements achieved by the disturbance rejection.

Compensation of Voltage disturbances in hybrid AC/DC Microgrids using series converter

In this paper a series power electronic converter is proposed to improve power quality of AC/DC hybrid microgrids. An injection transformer which is series with AC microgrid is used beside the series converter to inject voltage for the purpose of voltage disturbances compensation. The series converter by using a simple and effective control system in stationary reference framework of d-q-0 is proposed to compensate voltage sag and swell, source unbalanced voltages, voltage harmonics of the utility. In these types of micrigrids a lot of voltage disturbances have occurred due to large number of converters. Moreover, it is not required to use a storage energy system like battery; the required power is supplied by DC microgird, so the proposed system is very efficient. Simulation results in the MATLAB/Simulink environment have verified the appropriate performance of the proposed method.

Unified power quality conditioner based on a three-level NPC inverter using fuzzy control techniques for all voltage disturbances compensation

This paper presents a novel and efficient control scheme for unified power quality conditioner (UPQC) based on three-level neutral point clamped (NPC) inverter using fuzzy logic techniques. The proposed UPQC is capable of mitigating source current harmonics and compensate all voltage disturbances such as voltage sags, swells, unbalances and harmonics. It is designed by the integration of series and shunt active filters (AFs) sharing a common DC bus capacitor. The DC voltage is maintained constant using proportional integral voltage controller. The synchronous reference frame (SRF) theory is used to get the reference signals for shunt active power filters (APFs) and the power reactive theory (p-q theory) for series APFs. The shunt and series APF reference signals derived from the control algorithm and sensed signals are injected in two controllers to generate switching signals. To improve the UPQC capability, fuzzy logic techniques are introduced to control the series APF. The performances of the proposed UPQC system are evaluated in terms of power factor correction, mitigation of voltage or current harmonics and all other voltage disturbances compensation using Matlab-Simulink software and SimPowerSystem toolbox. The simulation results illustrate the performance of the proposed UPQC at the common connection point of the nonlinear load to improve the power energy quality.

Simplified Control Scheme of Unified Power Quality Conditioner based on Three-phase Three-level (NPC) inverter to Mitigate Current Source Harmonics and Compensate All Voltage Disturbances

This paper proposes a simplified and efficient control scheme for Unified Power Quality Conditioner (UPQC) based on three-level (NPC) inverter capable to mitigate source current harmonics and compensate all voltage disturbances perturbations such us, voltage sags, swells, unbalances and harmonics. The UPQC is designed by the integration of series and shunt active filters (AFs) sharing a common dc bus capacitor. The dc voltage is maintained constant using proportional integral voltage controller. The shunt and series AF are designed using a three-phase three-level (NPC) inverter. The synchronous reference frame (SRF) theory is used to get the reference signals for shunt and the power reactive theory (PQ) for a series APFs. The reference signals for the shunt and series APF are derived from the control algorithm and sensed signals are injected in tow controllers to generate switching signals for series and shunt APFs. The performance of proposed UPQC system is evaluated in terms of power factor correction and mitigation of voltage, current harmonics and all voltage disturbances compensation in three-phase, three-wire power system using MATLAB-Simulink software and SimPowerSystem Toolbox. The simulation results demonstrate that the proposed UPQC system can improve the power quality at the common connection point of the non-linear load.

Analysis, Design and Control of a Unified Power-Quality Conditioner Based on a Current-Source Topology

This paper presents a three-phase unified power-quality conditioner based on current source converters (CSC-UPQC), including the design guidelines of the key components, an appropriate control scheme, and a selection procedure of the dc current level. Particularly, the ride through capability criterion is used to define a minimum dc current level so that the CSC-UPQC achieves the same characteristics as a UPQC based on voltage-source converters in terms of voltage disturbance compensation in the point of common coupling (PCC) and load power factor compensation. A 1.17 MVA load fed from a 3.3 kV system is used to show the proposed design procedure, and a laboratory prototype is implemented to show the system compensating sags and swells using low switching frequency in the CSC and maintaining a unitary displacement power factor in the PCC.

DC-Bus Voltage Control Technique for Parallel-Integrated Permanent Magnet Wind Generation Systems

This paper presents a dc-bus voltage control technique for a new power conversion topology feasible for parallel-integrated permanent magnet (PM) wind generation systems. This technique is based on a master-slave hysteresis control scheme in order to solve discrepancy problems that could happen between the controllers. A three-phase semicontrolled rectifier topology is proposed here as an effective interface circuit between each wind generator and the dc-bus. The proposed system provides interconnection extension ability of multiwind converter units sharing the same dc-bus and more economic utilization of the wind generator; by ensuring unity power factor operation. More advantages include voltage disturbance compensation capability, robustness: since a short circuit through a leg is not possible and high efficiency: due to the reduced number of switching elements. The rectifier topology concept, the principle of operation, the control scheme, and test results are presented. The developed technique is also implemented on a 12 kW parallel-connected PM laboratory setup in order to confirm the effectiveness of the proposed system.

Voltage quality improvement by a dynamic voltage restorer based on a direct three-phase converter with fictitious DC link

In this study, a new topology for a three-phase dynamic voltage restorer (DVR) has been proposed. The proposed topology uses direct three-phase to three-phase converter with fictitious DC link to compensate for the balanced and unbalanced voltage sags/swells and voltage flickers. The used converter in the structure of the proposed DVR has two inverter and rectifier parts with an intermediate fictitious DC link. The converter is directly connected to the grid and takes the required compensation power from the grid. As a result, the DC link capacitor and energy-storage elements have been eliminated in the proposed topology. Therefore the voltage compensation can be accomplished for any long time interval. This topology has less volume, weight and cost owing to the elimination of the energy storage elements. Unlike other direct AC/AC converter-based topologies, the proposed topology uses unidirectional switches instead of bidirectional switches, which results in the reduction in the number of switching devices. The computer simulation using PSCAD/EMTDC software and a laboratory-scale experimental prototype verify the capabilities of the proposed DVR in voltage disturbances compensation.

Compensation of voltage disturbances in distribution systems using single-phase dynamic voltage restorer

In this paper, a new topology is proposed for a single-phase dynamic voltage restorer (DVR) using direct ac/ac converter. This topology does not require dc-link energy storage elements. The proposed topology has a simple structure and can compensate several types of voltage disturbances such as voltage sags, swells, harmonics and flickers. This topology will not face any problem in long time compensation due to the fact that it provides the required energy directly through grid. The proposed topology can be easily extended to n-phase systems such as three-phase based on the same principle of the operation. In n-phase systems, the voltage sags and swells can be properly compensated regardless of the balanced or unbalanced operation. A new control method is also proposed for direct ac/ac converter in the proposed topology. The simulation and experimental results verify the effectiveness of the proposed topology and its control method in voltage restoration.

Feedforward pulse-width modulator forboost DC-DC power converters

The authors describe a novel pulse-width modulator with feedforward compensation of input voltage disturbances in boost DC-DC switched mode power converters. The modulator transforms an open-loop boost converter into a linear DC voltage amplifier. It is suitable for simple integrated-circuit implementation using the same building blocks as existing PWM controllers for switched mode power supplies.