Phase Voltage Source Converter Research Articles

Voltage and Current Control Strategy for Grid Connected WECS Employing Two and Three Level Voltage Source Converters

This paper presents voltage and current control strategy for grid connected variable speed wind turbine induction generator employing two and three level voltage source inverters. Induction generators are widely used because of its low cost, robust construction and capability of feeding active power to load without getting reactive power from separate source. The mechanical energy required to drive the generator is obtained from a variable speed wind turbine. Three phase induction machine is excited from a three phase voltage source converter. The DC voltage of the capacitor is inverted and fed to the three phase grid using a current controlled voltage source inverter. Control strategy has been developed for maintaining the DC link voltage constant and also to feed the power at unity power factor to the grid, even though there is variation in wind speed. It is also shown that the harmonics are considerably reduced when a two level inverter is replaced by a three level inverter. The simulation study has been carried out using MATLAB/Simulink. Simulation results indicate the feasibility of control strategy.

Robust Integral Terminal Sliding Mode Control of three phase voltage source converter for PV Grid Connected System

This paper proposes a robust integral terminal sliding mode control (ITSMC) strategy for a three-phase two-level voltage source converter used in photovoltaic power generation systems. The main goal of the proposed controller is to steer the system state along a predefined sliding surface while mitigating the chattering phenomenon. This development aims to significantly improve system performance by reducing overshoots and solving real-world PV challenges such as irradiation fluctuations, all while achieving a faster dynamic response. To demonstrate the robustness of the ITSMC controller, it is subjected to varying irradiation levels and measurement noise. MATLAB/Simulink software is employed for simulation and validation of the proposed system. Comparative analysis reveals that the proposed controller outperforms conventional sliding mode controller in terms of current overshoots and dynamic response. These findings demonstrate compliance with the criteria outlined in IEEE Std 519-2014.

GRID INTEGRATION OF VOLTAGE SOURCE CONVERTER USING POWER SYNCHRONIZATION CONTROL

Renewable Energy Sources (RES) are integrated with electric power systems around the world at an accelerated pace. Due to their intermittent nature, integrating RES into the power grid is a challenging task. Because of their good controllability and superior performance in weak AC grids, the three phase Voltage Source Converters (VSCs) are generally used for this purpose. The grid connected converter has to correctly detect the grid voltage signal during voltage distortion and unbalance condition. In this research work, a control method using power synchronization for grid integration of VSC is developed and simulated. In this control technique, the electricity fed to AC grid from VSC is controlled using the internal synchronization mechanism as like in conventional synchronous machine. Utilizing this type of control, the instability of VSC affected by a standard Phase Locked Loop during weak grid condition can be avoided. Moreover, a VSC terminal could support a weak AC system with strong voltage, just similar to an ordinary synchronous machine organizer. Simulations are done in Matlab/Simulink to validate the system performance of grid attached VSC with the Power Synchronization Control.

A Switching Predictive Control Method of Three Phase VSCs Based on Switching Affine Model

The working process of three-phase voltage source converters (VSCs) can be treated as the switching between the different subsystems, which is a typical switched system. The switching control strategies based on the switching model achieve satisfactory control performance of three-phase VSCs with very simple control structure and less control parameters. However, two drawbacks restrict the flexible applications of the present switching control strategies, i.e. the unfixed switching frequency problem and the unstable subsystem switching problem caused by the system delay. In this paper, a current switching predictive control (CSPC) method based on the current switching affine error model is proposed to the three-phase VSCs. The proposed method, by remaining the advantages of traditional switching control methods, realizes the fixed switching frequency of three-phase VSCs in the framework of switched system and achieves desired performance under system delay conditions. The simulation and experiment results verify the effectiveness of the proposed methodology.

Grid tied solar PV system with power quality enhancement using adaptive generalized maximum Versoria criterion

A three phase grid tied solar photovoltaic (PV) system with power quality compensation features is presented in this paper. This system is operated to transfer power generated from solar PV array to feed linear and nonlinear loads along with compensation of several power quality (PQ) issues such as harmonics, redundant reactive power and load unbalancing. The generated DC power from PV array is converted into AC by implementing a three phase voltage source converter (VSC). In order to transfer active power and mitigate PQ problems, an efficient control technique is required for grid tied solar PV system. This work presents the use of adaptive generalized maximum Versoria criterion (AGMVC) controller for VSC used in solar PV energy conversion system. Efficient utilization of solar PV array is accomplished by using Perturb and Observe based maximum power point tracking (MPPT) algorithm. The experimental setup of grid integrated PV system is implemented in the laboratory using IGBT based VSC and DSP (dSPACE DS-1202). Performance of AGMVC control technique is verified experimentally using laboratory prototype. This control technique is compared with different conventional controllers such as synchronous reference frame theory (SRFT) and instantaneous reactive power theory (IRPT) along with recently developed weight based controllers viz. least mean square (LMS), least mean mixed norm (LMMN) and normalized kernel least mean fourth-neural network (NKLMF-NN). Numerous terms such as fundamental weight convergence, steady state error, computational complexity, phase lock loop (PLL) requirement and harmonic compensation capability are considered for comparison purpose of AGMVC with the above listed control techniques. The system performance is verified according to IEEE-519 standard.

Harmonic Distortion Analysis of ANFIS controlled PV fed three phase Voltage Source Converter

Harmonic Distortion Analysis of ANFIS controlled PV fed three phase Voltage Source Converter

High Gain Converter Based Grid Connected Solar Water Pumping System

This paper presents a high gain converter based grid connected solar water pumping system. To improve the consistency of system, PV panel and BLDC motor made possible in full utilization. A Modified high gain boost converter is used for the water pumping system application. Single phase voltage source converter (VSC) with an unit vector template technique provide the bidirectional power control between the DC bus of the inverter and grid. The converter uses only a single power switch which is controlled for cost reduction and simplicity. This proposed topology is modelled in MATLAB/Simulink.

Interval Type 2 Fuzzy-Logic-Based Solar Power MPPT Algorithm Connected to AC Grid

In this article, an interval type-2 fuzzy logic controller (IT2FLC) is used as a Maximum Power Point Tracker (MPPT) to supply a large scale interconnected grid. The IT2FLC has the advantage of being able to regulate the MPP in case of severe variations of the weather conditions. A photovoltaic array is connected to AC grid via a DC-DC boost converter and a three-phase three-level Voltage Source Converter (VSC). The duty cycle of the boost converter is switched by the IT2FLC. A three phase VSC converts the VDC link voltage to AC and keeps unity power factor. The VSC control system uses two control loops: an external control loop which regulates DC link voltage to alternative current and an internal control loop which regulates the active and the reactive grid currents. Vd and Vq voltage outputs of the current controller are converted to three modulating signals used by the PWM Generator.

Grid interfaced solar photovoltaic system using ZA-LMS based control algorithm

Renewable energy sources such as solar photovoltaic can meet increasing energy demand in countries where there is sufficient availability of sun light. Intermittent nature of this kind of renewable energy sources demands a control which can handle fast dynamics of the system. This paper presents a grid coupled solar photovoltaic (SPV) system which includes solar photovoltaic array, incremental conductance based MPPT and boost converter. Grid integration of SPV array is performed using three phase voltage source converter (VSC) controlled with a fast and robust control algorithm. A Zero Attracting Least Mean Square (ZA-LMS) based controller is proposed to generate reference grid currents. These currents are compared along with sensed grid currents to generate switching pulses for three phase VSC. The proposed system is used to feed real power demand of load along with power quality refinement features such as suppression of harmonics, maintaining grid current at unity power factor and balancing of loads. Performance of the ZA-LMS controller is compared with conventional controllers such as normalized least mean square (NLMS) and dq0 frame theory. These controllers are compared for various characteristics concerning weight convergence, mathematical complexity, computational burden on real time controller and harmonic compensation. Proposed controller is implemented using dSPACE 1104 and tested on developed laboratory prototype of grid connected VSC working as shunt active power filter. Performance of the controller is observed and verified for steady state and dynamic load conditions.

PHC, Id-Iq and p-q Control Strategies for Mitigation of Current Harmonics in Three-Phase Three-Wire Shunt Active Filter with PI Controller

AbstractIn this research paper, the shunt active filter (SHAF) is used to improve the power quality of electrical network by mitigating the harmonics with the help of different control strategies (p-q control strategy, Id-Iqcontrol strategy, PHC control strategy) for three phase three wire system. It is quite difficult to optimize the performance of power system networks using conventional methods, because of complex nature of the systems that are highly non-linear and non-stationary. Three phase reference current waveforms generated by the proposed schemes are tracked by three phase voltage source converter in a hysteresis band control scheme. The performance of proposed control strategies has been evaluated in terms of harmonic mitigation and DC link voltage regulation under various source voltage conditions. The proposed SHAF with different control strategies is able to eliminate uncertainty in the system and SHAF gains outstanding compensation abilities. The detailed simulation results using MATLAB/Simulink software are presented to support the feasibility of the proposed control strategy.

SRF based control of single stage dual purpose three-phase grid integrated solar PV system

Solar Photovoltaic (SPV) offers alternative sources of energy which is in general pollution free, environment friendly, sustainable and unlimited in nature. The concerns of environment due to green house gases and global warming force research communities to develop a smart power system that has capability to integrate Solar Photovoltaic with the power grid. There are many challenges in integrating SPV generation with the grid like efficiency, power quality, stability, cost of the energy conversion, load management, reliability etc. Moreover, power quality problems at distribution level like harmonics, unbalanced supply, unbalanced loads, reactive power, load management etc. affect the operation of grid connected SPV systems. Single stage grid connected PV systems has the advantage of use of a single VSC for MPPT (Maximum Power Point Tracking) and inverter operation. The proposed grid interfaced SPV generating system consists of a SPV array, VSC (Voltage Source Converter), three-phase grid and linear/nonlinear loads. The SPV energy is injected in to the DC bus of VSC during sunshine hours. The DC bus voltage of a three- phase VSC is regulated for MPPT from the PV array. Secondly, this system serves to provide harmonics elimination, load balancing, power factor correction (PFC) and regulating the terminal voltage at the PCC (Point of Common Coupling). In this paper, a SRF (Synchronous Reference Frame) based control of a single stage dual purpose grid connected SPV system is proposed and simulation based on MATLAB and Simpower System Blockset demonstrates the dual purpose of the system.

Autonomous operation and control of photovoltaic/solid oxide fuel cell/battery energy storage based microgrid using fuzzy logic controller

In this paper, development and simulation of photovoltaic (PV), solid oxide fuel cell (SOFC) and battery energy storage system (BESS) based microgrid is presented. The microgrid system is operating in autonomous mode to serve the loads. To effectively control the microgrid voltage and frequency and to achieve smoother power flow control between the generation and consumption, voltage–frequency (V/F) control based on fuzzy logic controller (FLC) is proposed in this paper. Even though when there are sudden load variations in the system and fluctuations in PV output power, the microgrid voltage and frequency is effectively maintained within the limits by the proposed FLC. The main function of the BESS is to absorb/supply the excess/deficit power from the PV system and to keep the dc-link voltage of the voltage source converter (VSC) constant. SOFC is used as a backup generator and it is controlled to generate its rated power when the state of charge (SOC) of the BESS reaches its lower limit. The PV, SOFC and BESS are connected to a common dc bus through dc–dc power electronic converters. A three phase VSC is used to convert the dc to ac and to supply various ac loads. The PV, BESS and SOFC based microgrid system is simulated using Matlab/Simulink. To show the effectiveness of the proposed FLC over the conventional proportional-integral (PI) controller, the same system is simulated using PI controller and the necessary results are compared.

Comparison between an Interleaved Boost Converter and CUK Converter Fed BLDC Motor

There is a great concern of torque ripple and power quality of three phase voltage source converter fed Permanent Magnet Brushless DC Motor (PMBLDCM). In this paper, two control strategies for BLDC motor drive has been investigated. One of the control strategies is based on PFC - CUK converter fed PMBLDCM drive and another one is PFC- interleaved boost converter fed BLDC motor drive. Comparison has been made between the two control stragies in terms of Torque ripple, Total harmonic distortion (THD) and power factor for different operating speeds. The proposed work as been implemented under MATLAB/simulink environment. Simulation results are presented to validate proposed work. From the results, it is observed that PFC interleaved Boost converter fed BLDC motor drive is more effective compared to CUK converter fed BLDC motor drive.

Research on Discontinuous Pulse Width Modulation Algorithm for Single-phase Voltage Source Rectifier

Abstract - Single phase voltage source converter (VSC) is an important power electronic converter (PEC), including single-phase voltage source inverter (VSI), single-phase voltage source rectifier (VSR), single-phase active power filter (APF) and single-phase grid-connection inverter (GCI). As the fundamental part of large scale PECs, single-phase VSC has a wide range of applications. In the paper, as first, on the basis of the concept of the discontinuous pulse-width modulation (DPWM) for three-phase VSC, a new DPWM of single-phase VSR is presented by means of zero-sequence component injection. Then, the transformation from stationary frame (abc) to rotating frame (dq) is designed after reconstructing the other orthogonal current by means of one order all-pass filter. Finally, the presented DPWM based single-phase VSR is established analyzed and simulated by means of MATLAB/SIMULINK. In addition, the DPWMs presented by D. Grahame Holmes and Thomas Lipo are discussed and simulated in brief. Obviously, the presented DPWM can also be used for single-phase VSI, GCI and APF. The simulation results show the validation of the above modulation algorithm, and the DPWM based single-phase VSR has reduced power loss and increased efficiency.

Robust current control design of a three phase voltage source converter

In this paper, a robust design method for current control is proposed to improve the performance of a three phase voltage source converter (VSC) with an inductor-capacitor-inductor (LCL) filter. The presence of the LCL filter complicates the dynamics of the control system and limits the achievable control bandwidth (and the overall performance), particularly when the uncertainty of the parameters is considered. To solve this problem, the advanced H∞ control theory is employed to design a robust current controller in stationary coordinates. Both control of the fundamental frequency current and suppression of the potential LC resonance are considered. The design procedure and the selection of the weight functions are presented in detail. A conventional proportional-resonant PR controller is also designed for comparison. Analysis showed that the proposed H∞ current controller achieved a good frequency response with explicit robustness. The conclusion was verified on a 5 kW VSC that had a LCL filter.

Voltage space vector‘s computation for current control in three phase converters

This work presents two current loop techniques, for three phase voltage source converters (VSC) used as controlled rectifiers (CR) operating at unity power factor. The first one is based on choosing the best natural vector, among the natural space vectors produced by two level voltage source inverters, with the use of a cost function. The second one is based on computing and synthesizing a space vector such that an absolute minimum in the cost function is obtained. The first algorithm is a simple method that presents power factor correction and good total harmonic distortion compensation. The second algorithm provides a novel and closed form formula to calculate the optimum voltage vector applied by the converter. In this method, pulse width modulation (PWM) is required to modulate the voltage vector that controls directly the line current, to follow the current reference. The simulations and experimental results show the advantages of the proposed control algorithm.