Distorted Source Voltage Research Articles

전원 전압 왜곡과 주파수 변동 시 단상 PWM 컨버터의 전류 제어

This paper presents a current control strategy in the synchronous reference frame for a single-phase PWM converter, which ensures sinusoidal input current control under the distorted source voltage and frequency condition. Given that the distorted source voltage distorts the phase angle for PWM converter control, the input current contains the same harmonics as the source voltage. Aside from the distorted voltage, the variation in source frequency reduces the performance of input current control. To achieve sinusoidal input current control under the distorted source voltage and frequency condition, this paper proposes a compensation strategy of current reference with the distortion component extracted from the phase angle and a detection strategy of frequency variation from the output of a synchronous reference frame phase-lock loop. The experimental results confirm the validity of the proposed method under the distorted source voltage and frequency condition.

Neural Network Based Control Strategy for Hybrid DSTATCOM in Three Phase Four Wire Distribution System Under Non-Ideal Voltage Source Conditions and Varying Load Conditions

In this paper the choice of power quality compensator is a DSTATCOM which constitutes a four leg voltage source converter (VSC) and a DC capacitor. An artificial neural network (ANN) based synchronous reference frame (SRF) theory is proposed for the generation of gating pulse of the DSTATCOM to balance the source current, eliminate harmonics and to compensate neutral current and reactive power in three phase four wire (3P4W) distribution system. In the proposed control strategy ANN controllers replace the PI controllers and low pass filters of conventional method. ANN controllers are also implemented to keep up the voltage across the capacitor and as a compensator to compensate neutral current under unbalanced load conditions. Various transformer topologies are simulated and compared with the proposed control strategy for compensation of neutral current. The DSTATCOM performance is adjudged under balanced, unbalanced and/or distorted voltage source conditions through simulation using MATLAB software. Data extracted from the experiment conducted in the laboratory to study the effect of non-linear load are used in the simulation to prove the efficacy of the proposed control strategy in power quality improvement.

A NOVEL CONTROL STRATEGY FOR SERIES-SHUNT POWER QUALITY COMPENSATOR

Advancement and extensive use of power electronic devices such as, fast switching uncontrolled/controlled convertors, invertors and cyclo-converters, high voltage power convertors used in HVDC, high voltage drives in traction system, arc furnaces, modern single phase electronic equipments like Compact Fluorescent Lamps (CFLs), Uninterruptible Power Supply (UPS), Personal Computers (PCs), printers, battery chargers, fax machines, photocopiers etc. creates power quality problems, the measure of it was voltage and current harmonics, poor power factor, imbalance, reactive power compensation, voltage regulation etc. Ideally power system network must be electrically clean, harmonics free, balanced, sinusoidal with unity power factor and regulated. This work deals with the performance of Series-Shunt Power Quality Compensator (SSPQC) under distorted source voltages and load currents. In this work a novel control strategy of Synchronous Reference Frame (SRF) used to extract the fundamental reference voltage component and the ICC based technique used to predict source current which simplifies the computation and amplifies the system performance.

Review of predictive control methods to improve the input current of an indirect matrix converter

The experimental implementation and performance analysis of control techniques applied to an indirect matrix converter are presented here, to improve the input current behaviour under resonances and harmonics distortions. The control strategies are based on model predictive control, which uses the commutation state of the converter in the subsequent sampling time, according to an optimisation algorithm given by a simple cost function and the discrete system model. Experimental results with a laboratory prototype are provided in order to validate the different control schemes, and the effects of a distorted source voltage and filter resonance are analysed.

Performance Comparison of Control Algorithms for Load Compensation Using D-STATCOM under Abnormal Source Voltage

 Ab stract—Distribution Static Compensator (D-STATCOM) is a custom power device which compensates reactive power and mitigates unbalances caused by various loads in distribution system when it is operated in current control mode. When D-STATCOM is used for load comprehensive compensation, the precision in detecting the compensation current required by the system is very important for compensation effects. There are many detection methods at present. This paper evaluates and analyses three different conventional and extensively used methods of determining the compensating current for a D-STATCOM under abnormal voltage conditions i.e. asymmetric and distorted source voltages and makes comparison of the performance of each one. The algorithms compared are instantaneous reactive power theory (IPRT), synchronous reference frame theory (SRF) and I-cosф algorithm. All three algorithms are simulated under MATLAB environment using Simulink. The theoretical analysis and simulated results illustrate the performance and correctness of these algorithms under asymmetric and distorted source voltages. Finally, the comparison of simulated results has been done to show the accuracy in detecting the harmonics and effectiveness of compensation under abnormal voltage conditions.

A novel ANN-based harmonic extraction method tested with ESN, RNN and MLP in shunt active power filters

With the wide use of power conversion devices - 'nonlinear loads' - many harmonic currents are being injected into the power grid. Shunt Active Power Filters SAPF are the power electronic equipment to compensate the harmonic currents caused by nonlinear loads. As the foundation of the harmonics recognition and compensation, harmonic extraction is the key technology in SAPF. Artificial Neural Networks ANN method has the features of parallel computation and satisfactory results for distorted source voltages over traditional extraction methods. This paper proposes a new harmonic extraction method based on ANN. To test the feasibility of different types of neural networks in this application, this paper compares the performances of three types of ANN: Echo State Networks ESN, Recurrent Neural Networks RNN and Multilayer Perceptron Networks MLP.

Front-End Buck Rectifier With Reduced Filter Size and Single-Loop Control

This paper presents a transformerless solution for front-end rectification, which is particularly suitable for traction applications, requiring high voltages to be stepped down to appropriate dc voltage. The proposed topology is based on pulsewidth-modulation buck rectifier (current source inverter topology) and is capable of rectification and stepping down of single-phase ac supply, in a single stage. A new control scheme is proposed to achieve constant dc output voltage and sinusoidal source current, irrespective of large ripples in the dc inductor current. The proposed scheme is configured in single-loop voltage control mode. The relevant small-signal model is derived from the large-signal model using multiorder decomposition. An elaborate procedure of dc filter design is discussed, for circuit operation with minimum energy storage. All analytical results are validated by numerical simulation for sinusoidal and distorted source voltage. Experimental verification is achieved through a 1.2-kW grid-connected laboratory prototype.

A Novel Algorithm of Fundamental Positive Sequence Voltage Detector under Unbalanced and Distorted Voltages

This paper presented a new algorithm for the performance improvement of fundamental positive sequence voltage extraction under unbalanced and distorted conditions. In this algorithm, an improved software phase-locked loop (SPLL) with a second order low-pass filter was proposed and analyzed, completely eliminating the phase detection errors of the unbalanced and distorted source voltages. The paper began with a description of the proposed fundamental positive sequence extraction method, and then a detailed analysis of the designed SPLL was introduced. The proposed algorithm improved the sinusoidal current control strategy of active power filter (APF) which was based on the classical power theories for obtaining an optimal extraction of the fundamental positive sequence current. To verify the feasibility of the algorithm in real-time applications, the simulation model was established in MATLAB-Simulink environment. Then, the algorithm was implemented in DSP using the TMS320F28335 development board. The results indicated that the proposed algorithm is feasible and effective, and it could be directly used in the practical applications.

A Comparative Assessment of Model Predictive Current Control and Space Vector Modulation in a Direct Matrix Converter

Matrix converters (MCs) are a very attractive alternative to conventional back-to-back converters with dc links. In this paper, a performance comparison between the well-established space vector modulation (SVM) technique and model predictive control (MPC) is presented for the current regulation in a direct MC. Both methods are analyzed and contrasted through simulation and experimental results. In order to establish their strengths and weaknesses, the assessment is made by measuring and comparing output and input currents and voltages with the same voltage source and load current conditions. Our results show that MPC is simpler than SVM from a conceptual point of view and provides better source current behavior, particularly with a distorted source voltage.

A Novel Load-Balancing Method and Device by Intelligent Grouping Compound Switches-Based Capacitor Banks Shunt Compensation

A novel compensator topology is proposed for three-phase unbalanced loads in the distribution networks. The negative and zero sequence compensation networks are proposed using delta-connected and star-connected capacitor banks. The compensation networks are paralleled with the unbalanced load to achieve a perfect balancing of active power and a complete compensation of reactive power of the unbalanced load. Intelligent grouping compound switches are implemented to control the capacitors, where, therefore, each capacitor can be switched between phases or phase and ground. Wireless sensors are also applied to acquire the load quantities. The compensation method proposed is based on symmetrical component theory. In addition, the load compensation based on instantaneous symmetrical component theory with positive sequence online extraction is proposed under unbalanced and distorted source voltages. The proposed load-balancing method and device are applied to Liaoning, Neimenggu, and Jilin provinces. The application results are provided to validate the performance of the proposed compensator topology and compensation method.

Instantaneous Reactive Power Minimization and Current Control for an Indirect Matrix Converter Under a Distorted AC Supply

This paper presents a current control scheme with instantaneous reactive power minimization for an indirect matrix converter. The strategy uses the commutation state of the converter in the subsequent sampling time according to an optimization algorithm given by a simple cost function and the discrete system model. Using this strategy, harmonics in the input current generated by the resonance of the input filter are strongly reduced. Simulation and experimental results with a laboratory prototype are provided in order to validate the control scheme, and the effects of a distorted source voltage and filter resonance are analyzed.

Comparison of control strategies for DSTATCOM in three-phase, four-wire distribution system for power quality improvement under various source voltage and load conditions

This paper presents comparison of three different control strategies to generate reference current components for Distribution Static Compensator (DSTATCOM). Reference currents are tracked by a three-phase voltage source converter in a hysteresis band control scheme. These methods are instantaneous reactive power (IRP) theory, symmetrical component (SC) theory and an improved instantaneous active and reactive current component (IARCC) theory. The performance of three methods has been evaluated under various source voltage and load conditions with new IEEE Standard 1459 power definitions. A comparative study of their performance in terms of rms value of source current, Total Harmonic Distortion (THD), supply power factor and compensator ratings is also presented. A three-phase, four-wire distribution system supplying linear as well as non-linear load is considered for simulation study which is carried out using MATLAB/SIMULINK software. Under balanced and sinusoidal source voltage conditions, all three control strategies similar performance while an improved IARCC theory outperforms, particularly, under unbalanced and distorted source voltage conditions.

Control strategies for harmonic mitigation and power factor correction using shunt active filter under various source voltage conditions

This paper gives a new insight into the concept of load compensation using shunt active filter (SAF) under ideal and non-ideal source voltage conditions. A novel approach based on an improved instantaneous active and reactive current component method is proposed. The performance of the proposed control strategy has been compared with instantaneous reactive power theory, symmetrical component theory and dq theory. SAF has been realized by three-phase voltage source converter. Reference currents generated by control strategies has been tracked by a SAF in a hysteresis band control scheme. The performance of the proposed scheme is evaluated in terms of reactive power compensation, reduction in magnitude of source currents, compensator currents, and harmonic compensation as per IEEE-519 standard. To ascertain the viability of the proposed control algorithm, the performance is evaluated under different source voltage conditions with the IEEE Standard-1459 power definitions. Variation in magnitude as well as harmonic content of source voltage has been considered. Under balanced sinusoidal source voltage condition, all control strategies congregate to similar results. Under unbalanced sinusoidal source voltage condition, dq theory and proposed theory have shown similar performance. However, under distorted source voltage conditions, an improved instantaneous active and reactive current component theory presents superior performance. A three-phase, three-wire distribution system supplying non-linear load is considered for simulation study. Simulation results from a complete model of SAF are presented to validate and compare the control strategies.

Load compensation using DSTATCOM in three-phase, three-wire distribution system under various source voltage and delta connected load conditions

This paper deals with a Distribution STATic COMpensator (DSTATCOM) for balancing of source currents, power factor correction and harmonic mitigation in three-phase, three-wire distribution system supplying delta connected load under various source voltage conditions. The control strategy applied to the DSTATCOM play a major role in its performance. A novel approach based on an improved instantaneous active and reactive current component (IARCC) theory is proposed for generation of three-phase reference currents for DSTATCOM. A three-phase voltage source converter with a dc bus capacitor is employed as DSTACOM which will track the reference currents in a hysteresis band scheme. The performance of DSTATCOM is evaluated under sinusoidal, unbalanced sinusoidal and unbalanced distorted source voltage conditions. Variation in load current, variation in magnitude and harmonic content in source voltage has been considered. Delta connected linear as well as non-linear load conditions have been considered. The performance of the DSTATCOM using the proposed control strategy is demonstrated using simulation results in MATLAB/SIMULINK software. Simulation results demonstrate the feasibility of proposed scheme for the control of DSTACOM.

Three Phase Multicarrier PWM Switched Cascaded Multilevel Inverter as Voltage Sag Compensator

This paper presents a cascaded H–bridge multilevel inverter based series active filter intended for installation on industrial and utility power distribution systems. The control strategy based on Synchronous Reference Frame theory is designed so that the voltage injected by active filter is able to mitigate the voltage sag, imbalance in the source voltage and reduce the harmonic content. The active power filter which can be used under the condition of voltage sag and unbalanced or distorted source voltages can compensate the harmonics, reactive and negative sequence currents.Simulations have been carried out on MATLAB/Simulink platform with various types of loads. The analysis and simulation results under unbalanced load and dynamic loading are presented in this paper.

왜곡된 전원 전압하에서 Composite 관측기를 이용한단상 PWM 컨버터의 정현파 전류 제어

본 논문에서는 composite 관측기를 이용하여 전원전압 왜곡시 단상 PWM 컨버터의 고성능 전류제어를 제안한다. composite 관측기를 적용함으로써 전원 전압 및 전류의 기본파와 고조파 성분을 시간지연 없이 추출할 수 있다. 추출된 기본파 성분은 전원단의 페이저 각을 찾는 PLL시스템에 이용된다. 멀티 비례-공진 제어기로 단상 입력전류를 정현파로 제어하고 고조파 성분을 제거한다. 시뮬레이션과 실험 결과로 제안된 방법의 타당성을 검증한다. In this paper, a high-performance current control for the single-phase PWM converter under distorted source voltages is proposed using a composite observer. By applying the composite observer, the fundamental and high-order harmonic components of the source voltage and current are extracted without a delay. The extracted fundamental component is used for a phase-lock loop (PLL) system to detect the phase angle of the source voltage. A multi-PR (proportional-resonant) controller is employed to regulate the single-phase line current. The high-order harmonic components of the line current are easily eliminated, resulting in the sinusoidal line current. The simulation and experimental results have verified the validity of the proposed method.

A four-leg unified series–parallel active filter system for periodic and non-periodic disturbance compensation

This paper presents a three-phase four-leg (3P4L) unified series–parallel active filter (USPAF) system, compensating for both periodic and non-periodic disturbances using a generalized non-active power theory (GNAP) based control strategy. The 3P4L USPAF system is realized by the integration of series and parallel active filters (AFs), composed of the two 3P4L voltage source inverters (VSIs) sharing a common dc-link capacitor. The GNAP theory was implemented previously in the parallel AF. In this study, the theory is proposed for the 3P4L USPAF system to compensate non-sinusoidal periodic and non-periodic currents and voltages. Distorted source voltages and unbalanced non-linear load currents compensation were verified simultaneously through the 3P4L USPAF system experimental prototype. Sub-harmonic and stochastic non-periodic current/voltage compensations were analyzed through simulations with Matlab/Simulink software. The simulation and experimental results showed that the theory proposed for the 3P4L USPAF system was applicable to non-active power compensation in three-phase four-wire (3P4W) systems under periodic and non-periodic disturbances.

A unified series-parallel active filter system for nonperiodic disturbances

This paper presents a 3-phase, 4-wire unified series-parallel active filter (USPAF) system for periodic and nonperiodic disturbance compensation using a generalized nonactive power theory. The USPAF system consists of a series active filter (AF), parallel AF, and split DC-link capacitors with the midpoint of the DC-link connected to the neutral wire. The generalized nonactive power theory is applicable to single-phase or multiphase, sinusoidal or nonsinusoidal, periodic or nonperiodic, and balanced or unbalanced electrical systems. The theory was implemented previously in a parallel AF. In this study, the USPAF system is proposed to compensate for the nonsinusoidal and nonperiodic currents and voltages. Distorted source voltages, source voltage sag, and unbalanced nonlinear load current compensation were simultaneously tested in the experiments. Subharmonic and stochastic nonperiodic current and voltage compensation were simulated in MATLAB/Simulink. Simulation and experimental results verified the validity of the generalized nonactive power theory for the compensation of periodic (nonsinusoidal) and nonperiodic current and voltage disturbances with the USPAF system.

Power quality enhancement utilising single-phase unified power quality conditioner: digital signal processor-based experimental validation

This study is based on a single-phase unified power quality conditioner (UPQC) to enhance power quality problem in single-phase systems. A simple control approach is implemented and validated through simulation as well as experimental studies. A laboratory prototype of UPQC is designed and developed using a digital signal processor. The performance of UPQC is validated experimentally under several operating conditions. It is found that the UPQC in single-phase system effectively compensates the important power quality issues, such as the load reactive power, load current harmonics, voltage harmonics, voltage sag, voltage swell and voltage flicker. Under distorted source voltage having total harmonics distortion (THD) of 14.1% with a non-linear load producing a distorted current (THD of 30.98%), the UPQC simultaneously compensates these harmonics resulting sinusoidal source current (THD of 3.77%) and load voltage (THD of 2.54%).

A Novel Fuzzy—Adaptive Hysteresis Controller Based Three Phase Four Wire-Four Leg Shunt Active Filter for Harmonic and Reactive Power Compensation

This paper presents a fuzzy logic based three phase four wire four-leg shunt active power filter to suppress harmonic currents. Modified instantaneous p-q theory is adopted for calculating the compensating current. Fuzzy-adaptive hysteresis band technique is applied for the current control to derive the switching signals for the voltage source inverter. A fuzzy logic controller is developed to control the voltage of the DC capacitor. Computer simulations are carried out on a sample power system to demonstrate the suitability of the proposed control strategy, for harmonic reduction under three different conditions namely, ideal, unbalance, unbalance and distorted source voltage conditions. The proposed control strategy is found to be effective to reduce the harmonics and compensate reactive power and neutral current and balance load currents under ideal and non-ideal source voltage conditions.