Shunt Converter Research Articles

Three-Phase UPQC Topology Based on Quadruple-Active-Bridge

In this study, a three-phase unified power quality conditioner (UPQC) topology based on a quadruple-active-bridge (QAB) is presented as an attractive solution to power quality issues. It is composed of three single-phase series converters, a three-phase shunt converter and a QAB converter located at the common DC-link. Since the bulky low frequency isolation transformers are replaced by the high frequency ones in QAB, it leads to higher power density, reduced weight and volume. The QAB converter could function as an energy router to provide multiple DC-link voltage access ports in the UPQC, which increase the flexibility of the UPQC. Finally, the MATLAB/Simulink simulation results and hardware-in-the-loop testing verify the correctness and effectiveness of the proposed topology and control method.

WITHDRAWN: PV system integration with multilevel-UPQC for power quality improvement in distribution system

Abstract Now-a-day’s, power consumption is increasing day by day due to world industrialization. To conserve fossil fuels for future generations, distribution energy generations (DG) are the best alternative. Wind and PV play a key role on renewable power generation. The power quality is the main constraint while feeding power to distribution loads. In this paper, DG is used to feed power to Unified Power Quality Conditioner (UPQC) through a multi-level converter. The multilevel converter is used as shunt and series converters of UPQC, and by using this converter, the harmonic component presented in the output of the converter is reduced and compared to the conventional 2level converter output and also reduce %THD presented on the fundamental value. Due to this, the filter requirement to filter out harmonic component is less compared to conventional case. The inclusion of multilevel converters in UPQC can reduce the filtering requirement, power loss and reactive power consumed by the converter. All the results are simulated and presented.

RETRACTED: Unified power flow controller in grid-connected hybrid renewable energy system for power flow control using an elitist control strategy

Due to the intermittent nature of renewable sources, miss-matching between power generation and load power causes a deviation from the desired voltage and frequency in power supply. To solve this problem, a new control technique has been proposed for the power flow control with the unified power flow controller (UPFC) in grid-connected hybrid renewable energy systems such as photovoltaic-wind. The proposed control technique combines the binary version of the grey wolf optimization (bGWO) and recurrent neural network (RNN). Here, bGWO is utilized to generate the dataset of control signals for shunt and series converters of the UPFC. Based on the accomplished dataset, the RNN technique performs and predicts the optimal control signals of the UPFC. Likewise, the proposed control scheme regulates the voltage deviation and minimizes the power losses simultaneously. Then, the proposed model is executed in Matrix Laboratory/Simulink working stage and the execution is assessed with the existing techniques such as fuzzy logic controller, improved particle swarm optimization and grey wolf optimization. The optimized gain parameters and elapsed time of the proposed and existing technique is also analysed. The optimized gain parameters such as KpKiof the proposed hybrid technique are 2.5 and 150. The elapsed time of the proposed technique is 30.15sec. Overall, the comparison results demonstrate the superiority of the proposed technique and confirm its potential to solve the above-mentioned problems.

Stability of Isolated Microgrids With Renewable Generation and Smart Loads

This paper investigates the low frequency (<; 30 Hz) oscillations in isolated microgrids (IMGs) with smart loads (SLs) alongside converter-interfaced distributed generators (CDGs) fuelled by renewable energy resources (e.g. wind, solar) with battery energy storage. In an IMG with normal loads (active or passive), such oscillations are typically associated with the droop control of the CDGs operating in grid forming mode. This paper shows that SLs have marginal influence on these low frequency oscillations but introduce a new oscillatory mode at a slightly higher frequency (> 20 Hz). First, the stability analysis model (linearized state-space model) of an IMG is extended to include the dynamics of a smart load with a series-shunt converter arrangement in its voltage compensator. It is shown that the dynamics of the phase-locked loop (PLL), DC link along with the control loops of the series and shunt converters of the smart load dictates the lower limit of its droop gain for stable operation. This is not apparent from the simplified SL models (i.e. neglecting the dynamics of the shunt converter and DC link) reported previously. Impact of smart loads on low frequency oscillations in IMGs is demonstrated in this paper through stability analysis and time domain simulation.

A UPFC for Voltage Regulation in LV Distribution Feeders With a DC-Link Ripple Voltage Suppression Technique

The large-scale integration of distributed photovoltaic generation causes several power quality issues in low voltage (LV) distribution networks. Network voltage profile variations severely affect the LV distribution networks. The four-leg unified power flow controller (4L-UPFC) has series and shunt converters that can address the power quality issues. However, instantaneous power theory shows that second-order harmonic voltage (2ωHV) appears at the dc-link capacitor of the 4L-UPFC during any unbalanced operations. This article proposes control strategies for series and shunt converters that will simultaneously regulate the load voltages of a distribution feeder while suppressing the 2ωHV term on the dc-link of the UPFC. A controlled negative sequence current from the shunt converter is used to suppress the 2ωHV term on the dc-link. The active suppression of the 2ωHV term allows electrolytic capacitors to be replaced with small long life ceramic or film capacitors, and this does not require additional passive compensation. Stability analysis of the control loops demonstrates the overall stability of the converter system. The proposed control methods have been implemented on a Texas DSP (F28377D). An experimental demonstration on a laboratory scale prototype shows that the proposed control methods can effectively regulate the load voltages at LV distribution feeders and suppress the 2ωHV on the dc-link of UPFC during unbalanced loads and supply conditions.

Unified Power Quality Conditioner using PV Fed SVPWM based Multilevel Converters for Power Quality Improvement

This paper presents a solar photovoltaic based unified power quality conditioner (PV-UPQC). The proposed system consists of a shunt compensator (ShC), series compensator (SeC) and PV array connected in parallel to a common dc-link. A three-level diode clamped multilevel inverter configuration is used as shunt and series converters. The SVPWM technique provides reduction in the common mode voltage and the balancing of the dc link voltage. The shunt compensation converter extracts power from PV array and provides compensation for load harmonic currents. The series compensation converter compensates for the power quality (PQ) problems such as grid voltage sags/swells and source harmonic voltages. The proposed system utilizes space vector pulse width modulation (SV-PWM) in multilevel converter topology for the mitigating the power quality problems using PV-UPQC. The proposed system improves PQ and also utilize RES, it also simultaneously improves both current and voltage disturbances. The performance of the system is analyzed in MATLAB/Simulink for nonlinear load conditions.

RETRACTED: Applications of internet of things (IOT) to improve the stability of a grid connected power system using interline power flow controller

Abstract Using Internet of Things (IoT) technology in the clever network is an essential method to fast active the information of control Grid-system. Also, the grid system is valuable aimed at the compelling administration of the power framework foundation. This paper deals with a logical approach to design an Interline Power Flow Controller (IPFC) for a grid-connected several-line power scheme to improve the scheme strength and to improve the congestion management in a grid by considering the power flow among the multi-line, IPFC goes to a sequence of paying flexible alternating current transmission system (FACTS) device and it takes the capability toward control the power stream in multi-line transfer organizations.. The Distributed Interline Power Flow Controller involves the series and shunt converters in different transmission lines that are between related utilizing a run of the DC connector. In the transmission line, is the IPFC considered for the compensation and control of power flow in a multi-line transmission system. Every converter can give plan reactive compensation off its line also with the frequency. As the converters can exchange dynamic power through their essential DC interface, it can similarly give a frequency of the current. The highest objective is to improve the power flow in transmission lines and also to maintain the system stability at the buses, and it is achieved by developing an IPFC controller along with genetic algorithm. A Simulink model of an Interline Power Flow Controller based several-machine framework alongside genetic algorithm is developed, and its outcomes were compared with the conventional scheme for tuning the proposed controller to confirm their effectiveness and robustness. It also explains the optimization technique in multi-machine power system with an IPFC using GA. Concentrated on the normal for the development and improvement of the brilliant matrix, this paper presented the use of IoT in web-based checking framework of grid-connected power system using IOT.

Optimum sizing of PV based UPQC-DG with improved power angle control

Unified power quality conditioner with distributed generation (UPQC-DG) is a solution to the problems of power quality and integration of distributed renewable sources. UPQC, being a combination of series and shunt converters, can compensate for most power quality issues, but the use of two power converters increases the cost, and hence optimal sizing methods have been proposed in the literature. Sizing of UPQC-DG components, however, requires special consideration of power injected by DG. This paper proposes an optimum sizing method for UPQC-DG based on an improved power angle control (PAC) technique, which shares reactive power burden between series and shunt converters. Apart from optimal-sizing, this paper incorporates Volt-Ampere (VA) limits in the PAC method to ensure the operation of converters within designed ratings under all conditions. The performance of the proposed power angle control method has been tested for a case study system using Controller Hardware in Loop (CHIL), implemented with Opal-RT and Dspace/micro-labbox, and has been found superior to existing methods.

Isolated H‐bridge DC–DC converter integrated transformerless DVR for power quality improvement

This study presents a new H-bridge DC-DC converter-based transformerless dynamic voltage restorer topology (DVR). The proposed system can compensate balanced and unbalanced voltage sag/swell that are the most common electrical power quality problems and offers advantages over conventional DVR topologies by providing the isolation with high-frequency transformer (HFT) rather than bulky injection transformers and by employing shunt converter to eliminate the requirement of an energy storage unit. The system is composed of H-bridge DC–DC converter equipped with a HFT with one primary and three secondary windings and transformerless DVR. The single-phase shift modulation method is used for each series converter independently to provide the bidirectional power flow control of DC–DC converter, whereas in-phase compensation method with a hybrid detection algorithm is used to mitigate voltage sag/swell. An LC filter is employed to attenuate the switching ripple harmonics on the output of the DVR. The performance of the proposed system is verified experimentally on a three-phase, three-wire, 380 V, 10 kVA prototype.

MITIGATION OF VOLTAGE SAGS AND STABILITY ANALYSIS OF DISTRIBUTION SYSTEM BASED ON UPQC USING SUBSTANTIAL TRANSFORMATION INTRINSIC ALGORITHM (STIA)

The quality of power is important one of the distribution system, and it identify the voltage and current based distribution system power quality problem. The Voltage sag and swell is also to create power quality problem. In this power quality problem creates the frequency oscillation in the distribution system, so the output stability is affected. Because of this limitation, design of these improved model of controlling are properly required. The UPQC (Unified Power Quality Conditioner) is utilized to compensate the power quality problem and reduce the unbalanced voltage of this system. The proposed Substantial Transformation Intrinsic Algorithm (STIA) based UPQC is used to analysis the unbalanced voltage of this power distribution system. This proposed UPQC system is inject the real power to the transmission line, so the unbalanced voltage is compensate. Such that the injected voltage is controlled with help of series nd shunt active filter, and the angle of voltage injection is also controlled. The proposed STIA technique is used to give the proper pulse of this shunt and series converter to optimize the power quality problem with help of injecting the real power in this transmission line. The proposed Substantial Transformation Intrinsic Algorithm (STIA) method has run through the SIMULINK model, and this system attain the good performance, reduce the losses and increase the stability of power transmission line.

Mathematical modelling and application of generalized unified power flow controller (GUPFC) steady state model for power system network

Unified power flow controller (UPFC) is a unique kind of flexible alternating current transmission system device which can adjust power system parameters like active power, reactive power, and voltage magnitude as well as phase angle. Power transmission network is going to be more and more complex because of increase in multi-machine systems. In multi-machine systems, there is a need to adjust the power system parameters of two or more bus. In such cases, power system requirements are achieved by multiple UPFC. A reformed form of unified power flow controller which is defined as generalized UPFC comprises of one shunt converter and one then one series converter. Generalized UPFC is able to adjust the power system parameters for two or more bus or a subsystem. This paper provides the mathematical modeling of generalized UPFC in details. A novel approach based on a controlled current source employed for the scheming of phasor model of generalized UPFC in MATLAB. A comprehensive assessment is done between a phasor generalized UPFC model and multiple UPFC for congestion management of power system. The results establish the supremacy of generalized UPFC over multiple UPFC. This is the only work that brings forth for the first time, the time scheming of the phasor model of GUPFC in MATLAB/ Simulink.

Assessment and Damping of Low Frequency Oscillations in Hybrid Power System Due to Random Renewable Penetrations by Optimal FACTS Controllers

This paper presents a detail investigation on low frequency oscillations of a variable solar and wind penetrated power system. An optimized UPFC controller is proposed for damping low frequency oscillations to enhance small signal stability of such a power system. The modulation index of series converter and phase angle of shunt converters are controlled simultaneously in proposed UPFC controller there by incorporating the advantage of SSSC and STATCOM. The squirrel search algorithm (SSA) is proposed for tuning controller gains. The proposed UPFC controller has been compared with SSSC and STATCOM controllers to damp oscillations. Random variation of SPV, wind energy and their integration with varying synchronous generations has been considered in this work. It has been observed that increasing solar, variable wind and their interaction with variable synchronous power generation put more detrimental effect on low frequency power system oscillations. The detail time domain simulation and system eigen values predicted that proposed controller is able to damp these oscillations much efficiently for enhancing stability of such a critical power system.

Power Quality Improvement in DG System using BOA based Interlined Unified Power Quality Conditioner

To improve the power quality of multi-feeder distribution system, this paper proposes a concept of Interline Power Flow Controller (IUPQC). IUPQC is a structure of two filters such as, series and shunt filters. The causes for poor power quality of system is due to harmonics, power factor variations and changes in system voltage. The purpose of these converters is to mitigate the PQ issues. The reference signals required for series and shunt converters of iUPQC system is generated with the help of conventional controllers and PWM controllers. The PLL used to match the phase sequence of converters. For obtaining better improvement in Power Quality this paper is implemented with one of the optimization technique such as Bull Optimization Technique (BOA). The purpose of BOA is used to control the DC Link Voltage of iUPQC. With the help of this BOA technique, the variations in voltage and current are reduced to enhance the power quality. The effectiveness of this proposed system with BOA technique is tested and verified using Matlab/ Simulink environment.

Control of dual converter‐based grid‐tied SPV system with series–shunt compensation capabilities

This study deals with the control and implementation of a dual converter-based grid-tied three-phase solar photovoltaic (SPV) system with series and shunt compensation capabilities. The SPV system consists of two back-to-back-connected voltage-source converters, namely neutral and shunt converters. The purpose of neutral converter is to provide voltage compensation services. The neutral converter does not use any series transformer to provide voltage compensation and makes use of the distribution transformer available at the site. The shunt converter delivers the solar power to the utility grid and the local loads. Moreover, the shunt converter provides the compensation of harmonic and reactive currents generated by the local loads. A new harmonics detection method and control algorithm are developed using adaptive noise suppression-based adaptive filters and implemented for the control of dual converter-based SPV system. The performance and efficacy of the dual converter-based SPV system and its control are demonstrated using MATLAB-based simulations and hardware-in-the-loop-based experiments.

Applying analysis of power quality enhancement by using UPQC

The current power sector is dealing with the weak power quality issues and the main reasons hiding behind the weak power quality are harmonics, fluctuations of voltage, transients and reactive power consume. These problems are caused by arising trends in our consume. Nowadays, the share of supply from power electronic devices has greatly increased among our consume. Coupling of the grid to a symbiosis of wind farms and PV parks has also raised matter of weak power quality. There is no doubt that shunt and series compensation is efficient but if they are utilized as a single unit simultaneously, this will increase the efficiency of the device and become a greater beneficiary of the power sector, which together serve as UPQC (Unified Power Quality Conditioner). Therefore, to improve the power quality is the main task of UPQC and through compensation to the above problems proves that it has considerable advantages in improving power quality. So UPQC is considered to be an effective method to solve power quality problems. Since UPQC is used for both shunt and series compensators, it contains two inverters to provide this service. They are voltage source inverters with a common DC link, which are called shunt and series converters. These controllers can be controlled by various techniques such as PI controllers, Fuzzy controllers, Neural Networks etc. The series converter is in charge of the smoothing of the voltage, and the shunt converter compensates for the distorted load current.

Unified power quality conditioner with reduced switch topology for distributed networks

A unified power quality conditioner (UPQC) is a combination of shunt and series converter used to mitigate various power quality issues. In this work the shunt and series converters are designed with reduced number of switches. The new UPQC with reduced switches is controlled using SRF based Carrier Double Zero Sequence Signal Modulation (CDZSSM) technique to mitigate the various power quality issues like voltage sag, current ripples and Total Harmonic Distortion in voltage and current waveforms. This reduced switch UPQC with CDZSSM control inherits all the merits of the conventional UPQC system, but the proposed UPQC system has better utilization of DC link voltage and moreover the voltage stresses across the switches are reduced. The results obtained from simulation and hardware of the reduced switch UPQC are compared and presented.

A Novel DROGI-Based Detection Scheme for Power Quality Improvement Using Four-Leg Converter Under Unbalanced Loads

In three-phase four-wire systems, the four-leg converter has been an attractive solution for mitigating power quality problems, such as reactive power compensation, load balancing, neutral current reduction, etc. However, its conventional control algorithms based on instantaneous reactive power theory (IRPT) and synchronous reference frame theory (SRFT) have relatively slow dynamic response and unstable operation during transient conditions. Thus, a novel control algorithm using double reduced-order generalized integrators for a four-leg shunt converter is presented in this article. The first integrator is adopted to extract required reference compensation currents for power quality improvement, and the second one is to decouple compensation currents and rectification currents of the converter side. The reference rectification currents are generated using an outer-loop dc-link voltage controller and are synchronized to the three-phase voltages. Since the compensation mode (dc–ac) and rectification mode (ac–dc) of converter are decoupled and regulated separately, the four-leg converter operation with fast dynamic response, robust performance, and flexible controllability is achieved. The effectiveness of the proposed algorithm is validated using both simulation and experimental results for a 1.1-kW rated system. Experimental results for the proposed scheme are presented and compared with that of existing IRPT and SRFT detection methods in the literature.

A 3P4SW Based UPQC to Improve Power Quality in Medium Voltage Distribution System

The adverse effect of power quality issues on power distribution system due to power electronics based controllers has tremendously increased in the modern power system; therfore, it is highly desired to design a novel power quality conditioner with a minimum number of switches to compensate voltage and current distortions. This proposed configuration reduces switching losses and also effectively alleviates the performance of the power quality conditioner. This paper introduces a configuration of 3P4SW (Three Phase Four Switch) UPQC (Unified Power Quality Conditioner) for both shunt and series APF (Active Power Filter) which can be implemented in medium voltage power grid. The major challenge of phase balance with only four switches in UPQC is accomplished by adaptive Self-tuning PID using neuro-fuzzy logic control and adaptive reference current generation scheme. This controller improves sag and swells compensation with better angle control via shunt and series converter performance and passive components design. The efficacy of proposed topology is tested on MATLAB/Simulink software and results are compared with the existing three phase six switch configuration (3P6SW).

Sensitivity-based coordination to controllable ranges of UPFCs to avoid active power loop flows

With its power setting decided by power system conditions, the unified power flow controller (UPFC) changes the direction of the power flow of the transmission branches, possibly yielding or intensifying the active power loop flows (APLFs). This paper studies the controllable range of the active power setting of the UPFC to avoid the APLF. The sensitivity between the active power setting of the UPFC and the active power flow of the critical branch is proposed, and iteratively solved to find the marginal power setting yielding zero active power flow of the critical branch. The controllable range of the active power setting to avoid the APLFs is decided by the max/min marginal power settings. The coordinated model between the series and shunt converters is newly proposed to determine corresponding controllable ranges with the change of the voltage setting, and the coordinated model of multiple UPFCs is proposed to decide active power settings of multiple UPFCs. The Floyd-Warshall algorithm is improved to satisfy the rule of rectangular algorithm, thus to find the APLFs and the critical branches. The numerical results on the New England 39-bus system show the feasibility and effectiveness of the proposed models.

Performance analysis of ANN-based multilevel UPQC under faulty and overloading conditions

ABSTRACT This study presents Levenberg–Marquardt back propagation (LMBP)-based artificial neural network controlled UPQC. The proposed power distribution system includes LMBP, back-to-back connected 5-level diode clamped converter (DCC), three-phase three wire distribution system, sinusoidal PWM, Hysteresis current controller and Power Angle Adjustment (PAA). Various abnormal faults like L–G, L–L–G and L–L–LG faults are considered as the major challenging issues for analysis. ANN-based PAA control is developed in this work to share reactive power between shunt and series converters without increasing the converter rating of UPQC and hence reduces the overall cost of the system. Simulation models of back-to-back connected 5-level DCC-based UPQC, Synchronous Reference Frame (SRF) and proposed ANN-based power angle control schemes are developed using SPS toolbox in Matlab/Simulink. ANN control scheme demonstrates more effective solution compared to SRF-based control, under the system subjected to different states.