Shunt Converter Research Articles

An Analysis of Case Study Utilizing Distributed Power Flow Controllers Which Improves and Mitigates Power Quality

Abstract—Providing high-quality electrical power should be taken into consideration in light of the rising demand for electricity and the rise in non-linear loads in power systems. This research examines power quality concerns related to voltage sag and swell and uses a distributed power flow controller (DPFC) to reduce voltage deviation and enhance power quality. A novel FACTS device, the DPFC shares structural similarities with the unified power flow controller (UPFC). Despite UPFC, DPFC separates the three-phase series converter into many single-phase series dispersed converters via the line and removes the common dc-link between the shunt and series converters. A DPFC located in a single-machine infinite bus power system with two parallel transmission lines is included in the case study. The MATLAB/Simulink environment was to model the system. The simulation findings that are shown confirm that DPFC may raise power quality.

Choke Anastomosis: A Key Element Acting as a Shunt Converter Between Adjacent Angiosomes.

Choke anastomosis is commonly recognized as a resistance factor that detrimentally affects the hemodynamics of the skin flap; however, its additional potential physiological roles in normal skin function are currently not fully understood. Ten cadaveric forehead flap specimens pedicled with unilateral STAs were perfused with lead oxide-gelatin mixture, and then dissected into 3 layers, including the super temporal fascia-frontalis-galea aponeurotica layer, the subcutaneous adipose tissue layer, and the "super-thin flap" layer. The forehead flap and stratified specimens underwent molybdenum target x-ray and subsequent transparent processing to effectively visualize the microscopic spatial architecture of arterial vessels across all levels. Based on the different anastomoses near the midline area of the flap, 2 types of arterial perfusion were identified: choke anastomosis type (8/10) and true anastomosis type (2/10). The former formed multiple choke anastomoses near the midline. In the "super-thin flap" layer, arterial perfusion density on the ipsilateral side was significantly higher compared to that on the contralateral side. The arterioles on the ipsilateral side exhibited a dense and uninterrupted distribution, whereas those on the contralateral side appeared sparse and dispersed. The latter exhibited an alternative perfusion pattern; the bilateral arterial vessels were connected with 3 to 5 true anastomoses near the midline. Furthermore, the microscopic architecture confirmed a uniform distribution of arterioles that remained continuous from ipsilateral to contralateral sides in the "super-thin flap" layer. This study demonstrated that choke anastomosis not only impairs blood perfusion in the adjacent angiosomes but also acts as a shunt converter to impact the blood supply of distal skin flaps at different levels through the "trans-territory diversion phenomenon." This results in necrosis of the superficial dermis while preserving survival of the deep subcutaneous adipose tissue.

Design of novel UPFC based damping controller for solar PV integrated power system using arithmetic optimization algorithm

Abstract Integrating renewable energy sources like solar power into traditional power systems poses challenges. One such challenge is the effect of renewable power plants, which use power electronics, on the grid’s stability. Specifically, these plants can impact small-signal stability by either damping or exacerbating low-frequency oscillations. This paper introduces a novel Unified Power Flow Controller (UPFC) based damping controller specifically designed for Solar Photovoltaic (PV) integrated power systems. It employs an Arithmetic Optimization Algorithm (AOA) to optimize the UPFC damping controller parameters and mitigate low-frequency oscillations in the power system. The objective function minimizes the Integral Time Absolute Error (ITAE) of speed deviations under varying loading conditions. The proposed technique is utilized simultaneously to control the modulation index of series and phase angle of shunt converters of UPFC. The MATLAB/simulation results obtained effectively from the proposed technique which is actualized and identify both detrimental and beneficial impacts of increased PV penetration for small signal stability performance. The study reveals both the small-signal stability of the system and its response to large disturbances that alter the active power balance and frequency stability. The results of the analysis demonstrated with single and multimachine environment by comparing with the other optimizations like PSO, DE, DE-PSO and GWO, the proposed one is effective for damping out the oscillations. The effectiveness of the proposed damping controller is further confirmed through real-time validation using the OPAL-RT setup.

Power quality stabilization system for grid connected large-scale solar power system

This paper presents solution to power quality issues when integrating a 1.5 MW photovoltaic array (PVA) with a unified power quality conditioner (UPQC) into the power grid. A modified unit vector template control scheme is used to generate a reference load voltage signal, and a synchronous reference frame (SRF) is created using a low-pass filter to control UPQC. Furthermore, the PVA is interfaced with the grid through a common DC link of shunt and series converters. The series converter mitigates power quality problems allied with the grid side, such as 3rd, 5th, and 7th harmonics, voltage sag, and voltage swell, by introducing signals in phase and out of phase voltage, respectively, at the point of common coupling (PCC). The shunt converter mitigates nonlinear load current harmonics and compensates for reactive power using SRF. The suggested methodology is implemented using MATLAB Simulink with both linear and nonlinear loads under different power quality conditions. Total harmonic distortions are maintained below 5% at PCC, as per IEEE-519 standards.

The Design and Dynamic Control of a Unified Power Flow Controller with a Novel Algorithm for Obtaining the Least Harmonic Distortion

This study investigates the control and dynamic operation of the Unified Power Flow Controller made of shunt and series converters, a Static Synchronous Compensator, and a Static Synchronous Series Compensator, respectively, connected back-to-back through a common DC-link capacitor. The model of a 48-pulse Voltage Source Converter is constructed from a three-level Neutral Point Clamped converter, which allows the total harmonic distortion to be reduced. An optimal conduction angle tracking system of the three-level inverter is designed to minimize distortion by detecting proper harmonic component elimination. Starting from the six-step modulation strategy, the dq decoupled control schemes of both compensators in open and closed loops are presented. Finally, the MATLAB-Simulink model of the power flow controller is implemented and analyzed. The results show that the controller can track the power changes and apply a suitable voltage to the power system so that the power flow can be controlled. This way, the power flow controller dynamically improves the voltage and power quality across the power network while simultaneously improving the transient stability of the system. It can eliminate all system disturbances resulting from oscillations and harmonics in voltage and current within a very short time. The procedural approach used to model and simulate the Unified Power Flow Controller, as well as the new algorithm used to obtain the harmonic number that minimizes the total harmonic distortion, can be applied to any AC power system.

A new-fangled connection of UPQC tailored power device from wind farm to weak-grid

A significant portion of wind power conversion systems worldwide comprise wind farms (WFs) that use Squirrel Cage Induction Generator (SCIG) and are directly linked to the power grid. In facilities that generate electrical energy at a moderate level, WFs are connected by means of distribution systems that use medium voltage (MV). It is not uncommon for such a system to produce a scenario in which the amount of electricity generated corresponds to the grid’s transit volume. When a wind farm’s wind power generation system is connected to a weak grid, the lack of potential control of the Point of Common Coupling (PCC) is a primary issue. This strategy is called a “Wind Farm with Weak Grid Connection.” Therefore, the amalgamation of weak grids, fluctuating electricity from wind, and variations in load on the system cause disruptions in the PCC voltage, further degrading the Power Quality (PQ) and the WF stability. Either the control method at the production level or the compensating strategies at the PCC level can improve this situation. If wind farms are built on SCIG and are directly linked to the grid, it is essential to utilise the last substitute. The technology known as Custom Power Devices (CUPS), proved extremely helpful for this type of application. This study presents a compensation technique based on a specific CUPS device, known as the Unified Power Quality Compensator (UPQC), as a possible solution. The potential terminals of WF needed to be regulated, and the voltage fluctuations on the grid side required to be reduced, so a custom-made control strategy for the UPQC device was designed internally. The control of power, such as active and reactive in the UPQC’s series and shunt converters, as well as the transmission of power via the UPQC DC-Link between converters, are the foundation of the internal control strategy that has been developed. Compared to other bespoke tactics that use reactive power, this strategy increases the UPQC’s capability to provide compensation. The suggested study calculates THD using a FUZZY controller. The results are compared to PI controller results. Simulation findings show how the suggested compensating strategy can minimise THD values and improve wind farm power and stability. The simulations suggest that the proposed compensating strategy enhances WF power and stability.

State-Feedback Control of a Hybrid Distribution Transformer for Power Quality Improvement of a Distribution Grid

A Hybrid Distribution Transformer (HDT) combines a power converter and a conventional Low-Frequency Transformer (LFT) in a single device. The most recurrent configuration consists of a shunt converter fed by the Auxiliary Winding (AW) of the LFT and a series converter connected to the low-voltage grid. Nonetheless, load harmonics circulate through the power converter and LFT, affecting their lifetime. In this work, an HDT composed of a series converter connected to the primary side through Coupling Transformers and a shunt converter directly connected to the secondary side is presented. The HDT model and discrete-time state-feedback control are presented. The results show that the HDT can improve the power quality of the grid, focused on extending the LFT lifetime.

Three-Phase Four-Wire Transformerless Unified Power Quality Conditioner Based on AC-DC-AC Nine-Leg Converter and Shunt Converter

Three-Phase Four-Wire Transformerless Unified Power Quality Conditioner Based on AC-DC-AC Nine-Leg Converter and Shunt Converter

A coordinated modelling and control of modified pumped storage governor with unified power flow controller to damp low frequency oscillations in power system for stochastic renewable penetrations

A modern power system network is more susceptible to oscillatory instability problem due to power oscillations caused by uncertain penetration of renewable sources. Also, pumped storage hydro power generation (PSHPG) is going to take important role for energy storage and management with varying renewable penetrations, but their governors need to be utilized efficiently for power oscillation damping. In this work a coordinated modified pumped storage governor with fractional parallel unified power flow controller (FPUPFC) has been modelled and controlled to damp angular frequency variations in power system. The prime objective of this work is to enhance efficacy of pumped storage hydro turbine governors integrated into an expert system with UPFC to take part in electromechanical oscillation damping. Here the governor is modified by fractional order PID action with additional phase compensation and in FPUPFC both series and shunt converters are controlled simultaneously by parallel fractional lead-lag based control action. The power system considered here consists of hydro generators of 100 MVA with 90.94 MW rated turbine output power with different operating conditions for two area 4 generators and 39 bus 10 generators multimachine renewable integrated system. It has been observed that efficacy of pumped storage hydro turbine governor action has been much improved when coordinated with FPUFC control action. A new hybridized modified differential evolution with fractional particle swarm optimization (MDEFPSO) is proposed to tune the parameters of proposed controller, with a multi-objective function considering variation in speed and real power deviations, settling time, overshoot and undershoot of system response.

Control Strategies for Enhancing Power Quality with Unified Power Quality Conditioner in a Solar-PV Integrated Utility System

The electrical utility systems are well-liked as local energy systems because of their capacity to incorporate renewable energy, enhance energy effectiveness and strengthen the resilience of the power system. These benefits do, however, come with specific complications regarding control and power quality (PQ). PQ within a utility system is paramount to ensure the appropriate operation of connected devices and the well-being of the overall system. As a result, both voltage quality & current quality are significant. Control strategies in conjunction with cutting-edge power electronics devices (PED) offer a solid framework to handle PQ challenges. Hence, this paper’s proposed work discusses the application of a Solar-Photovoltaic (PV) fed Unified Power Quality Conditioner (UPQC) for power quality enhancement towards the supply grid network. The Solar-PV fed UPQC enhances PQ and maximizes solar energy utilisation, leading to an eco-friendly and cost-effective solution while injecting clean, renewable energy into the grid. In this paper, the control strategies for UPQC are based primarily on the Adaptive Leaky Least Mean Square (AL_LMS) algorithm as compared with the Synchronous Reference Frame (SRF) based theory for switching of series and shunt active converters of UPQC. This AL_LMS approach extracts reference signals to switch UPQC’s shunt and series voltage source converters (VSCs) by iteratively updating the weights. Thus, the control strategy applied to Solar-PV fed UPQC mitigates voltage problems like voltage sag and swell, current harmonic distortions and other PQ issues. The work is done in MATLAB/ Simulation software and simulation outcomes show the effectiveness of Solar-PV fed UPQC in improving power quality by maintaining within the IEEE-519 Standards.

An Efficient PV - Integrated UPQC System for Power Quality Enhancement Using Improved Chicken Swarm Optimization

In today’s world, the power distribution system's problems with Power Quality (PQ) are not unfamiliar. However, customer awareness of these issues has also risen. Likewise, there are many conventional solutions to improve the power quality. However, these traditional solutions rely on passive elements and frequently fail to respond effectively as the nature of the power system changes. Custom power devices provide adaptable solutions for many issues. Therefore, a Unified Power Quality Conditioner (UPQC) Coupled with a PV system is proposed in this paper to improve the PQ problems, including fluctuations, voltage sag and swell etc. The deployment of an Interleaved Zeta converter aids in maintaining the constant DC link voltage. In order to derive the maximum desirable power from PV system, STATCOM with Adaptive Neuro- Fuzzy Interference System (ANFIS) is used, which is fine-tuned with the help of the Improved Chicken Swarm (ICS) algorithm. In addition, UPQC with series and shunt converter is employed to decrease the current and voltage harmonics, thereby enhancing the power factor. For controlling the working of UPQC, the d-q theory-based Proportional Integral (PI) is proposed. The suggested design of PV-UPQC is evaluated and the simulation results are obtained in the MATLAB platform with a reduced THD of 2.01%.

Comparison of Intelligent Control Methods Performance in the UPFC Controllers Design for Power Flow Reference Tracking

The Unified Power Flow Controller (UPFC) is one of such emerging FACTS devices that can manage the power flow in Transportation System. Based on the control system associated with the management of UPFC, both the controllers of shunt and series converters of UPFC are controlled conventionally using PIs controllers. However, the PI system alone cannot control the UPFC in the presence of uncertainty of system parameters and disturbances. For this reason, the use of novel robust techniques based on artificial intelligence theory in the design control of UPFC is very efficient for improving its performances. In this regard, four approaches have been used in this study to replace the conventional PI controller and enhance the performance of the UPFC for power flow reference tracking. In the first approach, the fuzzy logic technique (Mamdani and Sugeno types) has been employed to provide dynamic control of series and shunt converters of UPFC, whereas in the second method, the controllers of UPFC are performed through the optimization techniques such as: PSO, PSO_SQP, and GA techniques. The proposed techniques based UPFC are tested in MATLAB/Simulink software by using UPFC with a 48-pulse voltage source converter (VSC) equipping a High Voltage (HV) electrical network. In terms of dynamic performance, the simulations’ results and the comparative analysis clearly show the superiority of the intelligent controllers regardless of the variation of powers that affecting the model plant. Compared to PI controller, they ensure good performance in terms of tracking and decoupling.

Design and simulation of monarch butterfly optimized SP-UPFC for power quality compensation

The super smart gridsare a kind of broad-area transmission network, which makes use of Flexible AC transmission system (FACTS)and helps to reduce greenhouse gas emissions while also maintaining the electricity infrastructure of various nations. The six-phase unified power flow controller (SP-UPFC) is a FACTS device that offers total stability to power system networks in the form of series and shunt compensations. The power quality compensation (PQC) operation using SP-UPFC is achieved by adopting the monarch butterfly optimization (MBO) algorithm. Here, shunt converters and series converters of parallel and series connection units are kept in sync with the help of master-slave synchronization. In addition, a coordination strategy is created for the SP-UPFC control protection system and the power grid protection, which improves the ride-through capability during a failure. In comparison to state-of-the-art methods, the simulation results reveal that the proposed MBO-optimizedSP-UPFC decreases total harmonic distortion (THD) and increases power factor.

Power Quality Enhancement in Solar PV and Battery Integrated UPQC Grid Connected System

This paper discusses a distributed generation system consisting of grid-connected solar PV and a battery-integrated Unified Power Quality Conditioner (UPQC). Embedded in the PV array, the UPQC consists of a series and shunt converter connected back through a common DC link. In this system, power quality problems of clean energy, such as harmonics, voltage drops, ripples, are compensated by injecting active energy into the power grid. The shunt converter is controlled to maintain a constant DC link voltage and harmonic compensation of the load current. The main voltage problem is compensated by a series converter that injects the voltage during sag and swell. The advantages of integrating renewable energy sources and enhancing power quality are brought together in this system. The performance of the system is analyzed during voltage sag, swell condition and under unbalance condition for nonlinear load along with power flow analysis through the enhancement of dc bus voltage. Finally, the simulation results are shown for the estimation of dynamic performance of PV, battery integrated UPQC system during unbalanced condition

Fuzzy induced controller for optimal power quality improvement with PVA connected UPQC

Abstract The major power quality issues in grid are voltage fluctuations and harmonics. For better power quality of the power system during disturbances on the grid, the UPQC device is utilized to maintain voltage magnitude and reduced harmonics. At the DC link of UPQC along with the capacitor, a renewable PV source is connected which contributes in voltage compensation by the series VSC and harmonics compensation by the shunt VSC. For stable DC voltage generation from PV source a modified P&O MPPT with DC reference is included controlling the boost converter connected to PV source. The controllers of VSCs are operated by feedback loop synchronized schematics with voltage reference generation in series VSC control and current reference generation in shunt VSC control. The shunt control is updated with hybrid Fuzzy-PI controller replacing the traditional PI controller further improving the power quality of the grid. The hybrid Fuzzy-PI varies the K p and K i gains as per the error generated by the DC voltage comparison concerning 25 rule-base for each gain. A comparative performance analysis is done with both the controllers in the shunt converter and the results are generated using MATLAB Simulink software.

Transformer‐less unified power flow controller in medium voltage distribution networks

AbstractA transformer‐less unified power flow controller (UPFC) is a power electronic device consisting of series and shunt voltage source converters (VSCs) that are not connected to a common DC bus. It can control power flow in medium voltage (MV) distribution networks without the need for interfacing transformers. Hence there is a significant reduction in size and cost compared to a conventional UPFC. This paper investigates the operating range of a transformer‐less UPFC in an MV distribution network and the required power ratings of the series and shunt converters. The results showed that a transformer‐less UPFC is able to provide active power control using partially rated converters. However, its ability to control reactive power is limited by the current ratings of the converters. The analysis was verified using software simulation and hardware experiment.

An Enhancement of Power Quality With Efficient Active Power Transfer Capability in a PV–BSS-Fed UAPF for Microgrid Realization

This article investigates the enhancement of power quality with an efficient active power transfer capability in a universal active power filter (UAPF) integrated with a photovoltaic (PV) and battery storage system (BSS). The UAPF operates as a bidirectional interface between the PV–BSS and point of interconnection for microgrid realization. A new control strategy is proposed to extract fast and accurate voltage and current reference signals to operate the system in a desired manner. Here, the extraction of load voltages and calculation of load and reference powers are used to generate the reference signals, thereby comparing with actual signals with hysteresis controller to produce switching pulses of converters. As a result, the shunt and series converters form a robust system by acting as a current-controlled voltage source and voltage-controlled current source, respectively. It eliminates the need for adaptive filters and low-pass filters to extract the fundamental component of the load current. Furthermore, it increases the conversion efficiency of converters and improves the static and dynamic performance of the system. The proposed system is developed with a 1-kVA prototype laboratory setup using a field-programmable gate array controller and extensively tested with various test conditions such as grid voltage fluctuations, nonlinear and imbalanced load, and change in irradiance.

A Novel Control Scheme Using UAPF in an Integrated PV Grid-Tied System

This article investigates the photovoltaic fed universal active power filter (PV-UAPF) system for enhancing power quality indices. A novel comb filter together with second-order generalized integrator (CFSOGI) based instantaneous power balance theory with power angle (IPBTPA) control scheme is implemented. Under distorted or adverse grid conditions, the CFSOGI effectively extracts the phase angle, frequency, and fundamental positive and negative sequence components (FPNSC) to overcome the limitations of adaptive notch filters. Here, a comb filter constitutes a cluster/group of zeros at multiple harmonic frequencies to achieve notch peaks thereby providing superior harmonic rejection ability. Whereas, IPBTPA generates the reference signals to operate the system at dual compensation strategy with or without solar PV. The power angle is used to extract the desired load voltages under grid voltage fluctuations thereby reducing the burden on the shunt converter. Moreover, the hysteresis controller generates the switching pulses based on the calculation of reference and load powers which improves the dynamic performance by maintaining system power balance and effective DC voltage regulation. Besides, reactive power compensation, suppression of harmonic currents and mitigation of grid voltage fluctuations is also carried out to strengthen the system further. The system is also tested in grid voltage interruption for islanding mode to realize a microgrid system. The overall system performance is also validated using simulation and in a real-time experimental set-up, and results are demonstrated under various conditions.

Power Planning for a Reliable Southern African Regional Grid

Southern Africa has suffered from multiple power disruptions in the past decade due to inadequate electrical generation capacity, as well as load developments in locations that were not suitably planned for. Southern African countries are able to have reliable, sustainable, and efficient electrical power grids. The use of power interconnections for exchange power, especially for long-distance transmission networks, is important. Installing a suitable high-voltage alternating current (HVAC) with a high-voltage direct current (HVdc) will improve the active–reactive power compensation when transmitting electrical power over long distances (when transmitting bulk power is possible). Flexible alternating current transmission system (FACTS) devices are typically combinations of shunt and series converters. These approaches are capable of improving the power stability and voltage while allowing power to be transferred with minimal losses to an alternating current transmission system for the power exchange. In this article, two HVDC line-commutated converter (LCC) links, i.e., Angola–Namibia and Aggeneys–Kokerboom, were applied to minimize losses from 2657.43 to 2120.91 MW, with power setpoints of 1000 and 600 MW, respectively. The 2500 and 475 MVAr SVCs were used to control the voltage instabilities at Namibia and Mozambique substations, respectively. The use of HVdc to reduce losses and FACTS devices to enhance controllability and power transfer is extremely effective, particularly in long transmission lines transporting bulk power.

Model Predictive Controlled Four‐Bus System Employing Hybrid Power Flow Controller

A fuzzy logic‐ (FL‐) based control technique for unified power flow controller (UPFC) to resolve the power quality issues in transmission network is presented in this paper. MATLAB/Simulink is used to design the FL‐based controllers for shunt and series converters of UPFC, which is validated on 4‐bus system. In addition, the performance of the suggested FL‐based UPFC is compared with PI (proportional integral), HC (hysteresis controller), MPC (model predictive controller), and FLC (fuzzy logic controller), and the outcomes are compared in terms of settling time and steady‐state error. The consequences characterize that the higher enactment of closed loop hybrid power flow controller (HPFC) 4‐bus system with FLC UPFC controller’s (FL based) robustness is ensured from the simulation results as it has overcome the power quality issues like reactive power compensation, voltage sag mitigation, and THD reduction of transmission line current below 5% as per IEEE standard. Settling time of CL FBS is abridged from 0.87 to 0.62 sec, and steady‐state error of voltage in CL FBS is abridged from 0.9 to 0.1 V using FLC.