Power Quality Control Research Articles

Unified power quality control based microgrid for power quality enhancement using various controlling techniques

This research analyses the introduction of unified power quality control (UPQC) to mitigate the power quality problems, which is caused by using power electronics devices. In this article, the challenges in power quality, the suggested UPQC control approaches that are made by the distributed generation of dynamic voltage restorer (DVR) and static synchronous compensator (STATCOM) with the DC-link. The DVR is a series active power filter (APF) compensator and the STATCOM is a shunt APF compensator. In the meanwhile, DVR compensates voltage related issuesas well as STATCOM provides the needed reactive power supply by load and reducing the current issues associated with the unity power factor. The main objectives of the UPQC to mitigate voltage imbalance, harmonics, negative-sequence current and reactive power. To overcome the PQ issues the multifunction power conditioner is implemented. In addition, several proposed control approaches were employed and compared with series and shunt APFs. In MATLAB/Simulink software is used to illuminate the performance of the control strategies. Finally, the simulation will be evaluated and PQ problems in UPQC will be reduced by various techniques such as unit vector template generation technique (UVTGT), power balancing theory (BPT), proportional integral (PI) control technique and hysteresis control technique.

Suppression control strategy of MMC sub-module capacitor voltage in variable-frequency situation

Modular multilevel converter (MMC) topology has received widespread attention in flexible DC transmission, power quality control, and other fields because of its high modularity and malleability characteristics, and has become one of the most promising topologies. However, owing to the characteristics of the MMC itself, the fluctuation of the capacitor voltage of the MMC sub-module is inversely proportional to the MMC working frequency. One of the main technical challenges for MMC is effectively suppressing the fluctuation of the capacitor voltage of the MMC sub-module when working at low frequencies. This study first analyzes the reasons for the fluctuation of the MMC sub-module capacitor voltage at low frequency. Then, based on the results of this analysis, we propose a suppression control strategy for the capacitor voltage fluctuation of the MMC sub-module in variable-frequency working situations. Finally, an MMC module was built using the MATLAB/Simulink environment for simulation verification, and a five-level MMC physical experimental platform was built for experimental verification. The simulation and experimental results demonstrate that the proposed suppression control strategy for the MMC sub-module capacitor voltage effectively suppresses the fluctuation of the capacitor voltage under variable-frequency working situations.

Design Simulation of Improved Power Quality Conditioner System for Enhancement of Power Quality

The increased usage of power-sensitive electronic devices has prompted interest in power conditioning solutions, which is no surprise. As a result, some type of compensation must be supplied if power output remains below the standards' prescribed limitations. The UPQC (Unified Power Quality Controller) is one of numerous AC Transmission System families that can control voltage, impedance, and phase angle among other factors (FACTS). This study focuses on modern UPFC systems that have increased power quality efficiency to help utilities reduce voltage concerns. One of the FACTS controls for lowering stress sales effects is a unified power quality conditioner (UPQC). The quadrature voltage is specified using the UPQC series compensator. As a result, the compensator series never utilizes active power in a continuous scenario. As mentioned in the approach, a low power rating compensator injects voltage to remedy the system's power quality problem. The voltage is decreased and the power factor is raised when the fluid logic controller is used in conjunction with traditional UPQC. Furthermore, the load factor has been improved. The circuit is then imitated in MATLAB / SIMULINK using a fluctuating logo controller.

Harmonic suppression compensation of photovoltaic generation using cascaded active power filter

The wide spectrum of electromagnetism that explains current and voltage at specific time and location in a power system is referred to as power quality. Alternative energies are becoming more popular due to concerns about power quality, safety, and the environment, as well as commercial incentives. Moreover, photovoltaic (PV) energy is one of the most well-known renewable resources since it is free to gather, unlimited, and considerably cleaner. Active power filter (APF) is an effective means to dynamically suppress harmonics and solve power quality problems caused by the DC side voltage fluctuation. Therefore, this paper describes a substantial advancement in the harmonic suppression compensation algorithm, as well as the cascaded active power filter. Also, this paper focuses on compensating the error of photovoltaic grid-connected generation based on optimized H-bridge cascaded APF. The details of the working principle and topological structure of the APF used as the compensation device are analyzed. The H-bridge cascaded APF is optimized using the segmented variable step-length conductance increment (SVSLCI) algorithm. The overall cascaded APF control strategy is designed and simulated using MatLab/Simulink environment. By the simulation results comparing the existing traction network power quality control measures, before and after compensation, the effectiveness of the proposed control strategy is verified. The proposed controller strengthens the compensation of specific odd harmonics to improve the system work models and criteria to improve power quality. Moreover, the proposed algorithm showed positive significance for optimizing the quality of photovoltaic grid-connected power, reducing the current harmonic, and improving the equipment utilization of photovoltaic inverters.

Evaluation of Quality Control Data of Hormones Using Six Sigma Metrics Tool in Clinical Laboratory

Background: In health care system it is necessary to provide high quality and reliable test results to the patients. Many clinical laboratories are using six sigma as a tool to improve the quality control in health care system. Keeping this in mind, the present study was conducted using the quality control data of hormones under NABL(National Accreditation Board for Testing and Calibration Laboratories) which were assayed in our clinical laboratory.
 Materials and Methods: In this retrospective study, both the internal and external quality control data of 11 hormones were collected for a period of 6 months from April 2020 to September 2020 and the six sigma analysis was done.
 Results: Testosterone level 1(6.8), level 2(6.5) and Folate level1(6.9), level 2(6.6) showed sigma level more than 6 and hence excellent performance. The hormones, FT3 level 1(3.7), level 2(4.8), HCG level 2(3.6), TSH level 1(4.8), level 2(4.7) and Vitamin B12 level 1(4.4), level 2(4.5) showed average performance with sigma level between 3.5 and 6. The hormones, FT4 level 1(1.7), level 2(2), HCG level 1(2.2), Prolactin level 1(3), level 2(3.3), FSH level 1(1.9), level 2(2.0), LH level 1(2), level 2(1.9) and Progesterone level 1(3.4), level 2(3.3) showed poor performance with sigma level less than 3.5.
 Conclusion: Stringent rules need not be applied for hormones with sigma>6. Moreover, control limits can be relaxed to 3S so that false rejections can be minimized. For hormones with sigma< 6, internal QC rules have to be strictly applied and the root cause analysis has to be done. To conclude, six sigma metrics is a powerful quality control tool which helps to improve the performance of the clinical laboratory and hence the efficiency of the health cares system.

Allocation Control of Multi-functional Grid Connected Inverter and the Power Quality between of Grid Connected Microgrid Based on PSCAD Simulation Platform

On the one hand, the application of microgrid can effectively cut down the effect of distributed generation on distribution network, on the other hand, it helps to improve the power quality of distribution network. However, for the distribution network, a single multi-functional inverter has limited effect on the improvement of its power quality. Therefore, the allocation control of power quality by decentralized multi-functional inverters can further improve the utilization of inverters. This paper proposes to calculate the output current of multiple multi-functional inverters according to the harmonic and reactive current of the parallel node and the residual capacity of the multi-functional inverter. The simulation results show that the allocation control strategy proposed in this paper can effectively control the compensation capacity of the multi-functional inverter, so as to control the harmonic at the grid connection in place.

Control of grid-connected residential solar-PV system using novel adaptive linear combiner filter for power quality improvement

ABSTRACT A grid-connected residential photovoltaic (PV) system has been proposed using novel adaptive linear combiner filter-based control for power quality (PQ) improvement. In the present work, novel adaptive linear combiner (ALC) filter-based control-based control has been proposed to generate reference current. MATLAB/Simulink software is used to develop the two-stage grid-connected residential PV. The proposed control is tested in MATLAB/Simulink2018(a) under nonlinear, linear load and variable input and validated experimentally on prototype hardware. The performance of the proposed ALC filter-based control has been analyzed and compared with that of conventional synchronous d-q control. It has been observed from results that THD in grid current using proposed control is 3.74% whereas using conventional d-q control THD is 4.75%. Proposed control provides more efficient performance by improving the PQ of the system by compensating the harmonics and reactive load demand. Harmonic distortion in the grid current is within the limits as per IEEE-1547. Furthermore, proposed control has better transient response viz. settling time, under shoot and overshoot in DC link voltage during grid connection of rooftop PV system and provides, reduced complexity due to absence of phase lock loop (PLL), thus less sampling time, better accuracy, ease of implementation, and adaptability.

Research on output power quality control technology of three-phase inverter

With the wide application of new energy and distributed generation system, high-performance inverter plays an important role as the key link of power system access. Its performance determines the quality of output power. Therefore, the output power quality control technology of three-phase inverter has become one of the important research directions in this field. This paper introduces the current main inverter power quality control methods, summarizes and compares the advantages and disadvantages of a single control method, and points out that the composite control method is the development trend of inverter output power quality control technology.

Multi-source residual capacity collaborative dynamic compensation strategy based on robust residual generator

In this paper, a dynamic compensation strategy based on a residual generator was proposed to solve the problem of the power quality of the bus in an isolated AC microgrid. Firstly, the disturbance analysis of power quality problems such as voltage fluctuation, three-phase imbalance, harmonic wave is carried out, and the disturbance current is converted into the time domain function in the dq rotating coordinate system. Secondly, the inverter establishes the state space model under the dq rotation coordinate system. Then, the control structure based on residual generator is proposed, the voltage compensator is solved by model matching method, and the current loop secondary compensator is designed to eliminate the influence of the voltage compensator on the current loop. Thirdly, the residual capacity calculation method of the inverter is analysed, and the residual capacity is used to achieve the power quality collaborative governance on the parallel inverter system with the perturbation allocation method. Finally, the control strategy proposed in this paper is verified by the simulation built in PSCAD/EMTDC, and the results can be effectively applied to the low-level control of microgrid, and the power quality control effect of voltage fluctuation, three-phase unbalance and harmonics is good, which improves the robustness of the system to a certain extent.

Conservative power theory and its applications in modern smart grid: Review and prospect

As the worldwide trend of “carbon neutrality” action spreads, renewable energy substitution for fossil fuels in the electricity sector is inevitable. The traditional power system is updating to a new paradigm of smart grid to promote the consumption of renewable energy and phasing out of fossil fuels. However, this transition would bring about new tremendous challenges on power quality and operation & control of the power system. As the traditional power theories may not be able to handle the non-sinusoidal voltages, unbalanced and/or non-linear loads that are prevalent in evolving smart grid, a novel time-domain Conservative Power Theory (CPT) was proposed in the early 2000 s. So far, more than 190 papers have been published focusing on this attractive theory. This paper gives a summative and comparative overview of CPT and its innovative applications in modern smart grids. Horizontal comparisons among CPT and other common non-sinusoidal power theories are briefly performed and then the mile-stones in CPT’s development are highlighted. Basic power and current definitions under the CPT framework for both single-phase and three-phase systems are described in detail, and four main applications of CPT are discussed, which are load characteristic identification, accountability and revenue, filter and compensation, and power converters. Based on the review, the motivations, definitions, developments, and applications of CPT are comprehensively presented, some possible research aspects of CPT are itemized, and a future vision of CPT-based smart grid scenario is then conclusively predicted.

Mobile GPS Application Design Based on System-Level Power and Battery Status Estimation

Mobile systems such as smartphones require accurate estimation of the battery-related features including the remaining energy and operating time, especially as the the power consumption of user applications is growing continuously these days. We present an energy-aware smartphone application design framework that considers the battery’s state of charge (SOC), energy depletion rate, as well as the service quality of the target application. We use a verified-accurate battery energy estimation method in an Android-OS-based mobile computing system. The battery model considers the rate-capacity effect. We apply regression-based models for the power estimation of the major subsystems in the smartphone, and then aggregate the result to yield the whole system’s power. We first determine the quality of service for the location device (GPS), the display device (LCD), and the overall system (application). Then, we control the error rate of the GPS and the brightness of the display to acquire the maximum service quality of the system for a given car trip. We show the advantage of the proposed method with a case study of a trip. In this case, the smartphone guides a user’s car trip using its GPS navigation capabilities; to do this, we propose an adaptive algorithm that exploits our improved SOC estimation and considers the car’s variable velocity. This proposed adaptive power and service quality control of the GPS application improves the quality of service in this example case and ensures there is enough remaining battery for the trip to be completed. In contrast, conventional approaches to this task provide a lower quality of service and run out of battery before the trip finishes. In conclusion, if a trip plan is provided, an application using our method delivers the maximum quality of service, such as system endurance time, location error, and display brightness.

Battery‐supported unified power quality controller for small hydro‐based isolated power generation

In this paper, a battery-supported unified power quality controller (UPQC) for a small hydro-based isolated power generation is investigated as a voltage and frequency controller. The self-excited squirrel cage induction generator driven by constant power prime mover (small hydro turbine) has unacceptable voltage, frequency and power quality under non-linear loads. The battery-supported UPQC-based voltage controlled-voltage source converter is designed, modelled and simulated in MATLAB environment. Here UPQC has series and shunt converters with a battery and it is used to feed the local loads. This small distributed power generation system is capable to feed unbalanced non-linear loads because a shunt converter is used to take care the compensation of unbalanced loads and it always maintains the source currents balanced and sinusoidal. Moreover, a series converter is used to inject the series voltages in the self-excited squirrel cage induction generator terminals to regulate the common coupling point voltage during unbalanced non-linear loads. Performance of a battery-supported UPQC is also validated experimentally using a laboratory prototype of a 3.7 kW, 230 V, 50 Hz capacitor excited induction generator.

Comprehensive power quality evaluation method of microgrid with dynamic weighting based on CRITIC

The power quality assessment provides a reference for power quality management and control of microgrid operation. In terms of reflecting the correlation of power quality indexes and the dynamic changes of microgrid operating conditions, the traditional power quality assessment methods need to be improved. A power quality comprehensive evaluation based on CRITIC and dynamic coefficient is proposed in this paper. In this method, the objective weight of power quality indicators in single node is determined by using the intensity of conflict and contrast firstly. For the node weight calculation, the dynamic coefficient is proposed to reflect the different influence degree of node with different connected load. The proposed method in this paper can reflect both the internal characteristic of data sequence and the relationship between different data sequences. In addition, it also can reflect the dynamic changes of microgrid. Finally, an example is used to verify the feasibility of the proposed method.

High‐Throughput Quality Control Assay for the Solid‐Phase Synthesis of DNA‐Encoded Libraries of Macrocycles**

AbstractThere is considerable interest in the development of libraries of scaffold‐diverse macrocycles as a source of ligands for difficult targets, such as protein–protein interaction surfaces. A classic problem in the synthesis of high‐quality macrocyclic libraries is that some linear precursors will cyclize efficiently while some will not, depending on their conformational preferences. We report here a powerful quality control method that can be employed to readily distinguish between scaffolds that do and do not cyclize efficiently during solid‐phase synthesis of thioether macrocycles without the need for tedious liquid chromatography/mass spectrometry analysis. We demonstrate that this assay can be employed to identify linear impurities in a DNA‐encoded library of macrocycles. We also use the method to establish a useful quality control protocol for re‐synthesis of putative macrocyclic screening hits.

YYPO-PSO Algorithm Based Power Quality Control in a Grid-Connected Hybrid System

Micro-grid is a potential solution for the integration and management of renewable energy generation. Power generation through renewable energy sources has become more preferential and cost-effective, by articulating small scale distributed energy resources, micro-grids are becoming an alternative method in electrical power generation at the distribution voltage level. The increment of nonlinear loads and power electronic interfaced distribution generation system (DG) in the grid creates power quality issues like harmonic distortions in the distributed power system [6] [18]. The microgrid proposed in this paper consists of a photovoltaic array which represents the main generation unit and a three-phase induction generator that supplements the variable power generated by the photovoltaic array; a battery bank is included in the micro-grid to reduce the burden of the power generated by the micro-grid during the peak period [19] [20]. The power electronic interface maintains the necessary adaptability, security and reliability of operation between renewable sources and the distribution system [18]. In this paper, a comprehensive survey on micro-grid to improve the power quality parameters like THD is taken as the main objective with the help of suitable hybrid optimization algorithm, harmonic filters, controllers and battery storage.

Design of Z-Source Inverter-Based Dynamic Voltage Restorer Circuitry with R-SOGI Control Scheme for Enrichment of Power Quality

Increased utilization of nonlinear loads in the power distribution system with profound integration of renewable energy requires improved power quality control. This paper proposes a Reformed Second Order Generalized Integrated (R-SOGI) control scheme for enhancing the output of the Dynamic Voltage Restorer (DVR) for the objective of achieving the desired sinusoidal voltage wave shape at the common point of services and harmonic reduction. The DVR incorporates a Solar Photovoltaic (SPV) system using the Z-source Inverter (ZSI), providing the necessary active power to mitigate the voltage sag/swell and power demand. ZSI offers step-down as well as step-up abilities, it makes the converters to operate in the conditions of shoot-through. Therefore, the application of ZSI-based DVR topology seems very promising. The compensating reference voltage is generated by the R-SOGI algorithm, which offers superior output under conditions for grid voltage irregularities, including voltage sag/swell and unbalanced and distorted utility grid voltages. In comparison to DVR based on the VSI voltage inverter (VSI), the response from ZSI-DVR to a reduction of voltage distortions and harmonics is investigated. An experimental SPV ZSI-DVR prototype is developed in the laboratory to check the effectiveness of the controller and is tested under balanced and unbalanced supply and dynamic load conditions.

The modeling and analysis of the parameters of the non-sinusoidal modes

The article is devoted to the analysis of the parameters of the non-sinusoidal modes. These parameters include the components of the total apparent power in the presence of the voltage and current harmonics such as the voltage distortion power, the current distortion power, the harmonic distortion power, the fundamental apparent power. These components should be used to determine the primary source of the non-sinusoidal mode formation during the proper selection of the filter devices. For this purpose the five ways of non-sinusoidal mode formation are detected and for each of them the mathematical model has been created. The dependences of the total apparent power components changing under the variation of non-sinusoidal ways are determined by means of the mathematical modeling. These dependences should be considered as the theoretical basis for the choosing and proving of the type and structure of the filter device as the part of the automated power quality control and improvement system and also for the tuning of the parameters of the existing filter devices to improve their performance.

A Computationally Efficient Harmonic Extraction Algorithm for Grid Applications

The ability of an algorithm to extract power quality parameters on a low-end digital controller with constrained resources and computational capacity can promote comprehensive adoption of power quality control and monitoring infrastructure because of reduced cost and thus improve operational ability in a microgrid or distribution grid and support more in-depth integration of renewable energy. Since conventional harmonic extraction for single-phase grid mostly operate on Fourier transform, lock-in amplifier and their derivative algorithms, they demand large memory and computational power which are available with high-end application-specific processors, digital signal processors (DSPs) and field programmable gate arrays (FPGAs). In this paper, a computationally efficient harmonic extraction algorithm is proposed, which can be implemented on commercially available microcontrollers with ease, without compromising accuracy. A detailed theoretical analysis of the proposed method, along with various simulation and the experimental results are presented. Workarounds for minor implementation issues on digital controllers are discussed as well.

ANFIS‐fuzzy logic based UPQC in interconnected microgrid distribution systems: Modeling, simulation and implementation

This study focuses on the improvement of the power quality in interconnected power distribution systems using connected microgrids. The power quality issues at the secondary distribution level are addressed using a unified power quality conditioner, which aids in controlling voltage imbalances and current harmonics. Further, a power control method, adaptive network-based fuzzy inference system, is proposed as a global solution by installing independent compensating devices at the point of common coupling. The proposed strategy can improve the power quality in traditional installations because the proposed unified power quality conditioner method maximizes power utilization and improves the efficiency of the system. The microgrids integrate renewable energy sources, which generate green energy with low loss. Case studies, a prototype, and simulations via MATLAB/Simulink are used to validate the proposed method, and the results prove the enhancement in power quality control. The proposed control strategy had a response time of 0.3 s, reduced peak voltage distortions, and restored the voltage at the interconnecting point to a normal level. The total harmonic distortion of currents decreased from 21.13% to 14.74% when a PI technique was used to control the UPQC-P, and the proposed adaptive network-based fuzzy inference system-based UPQC-P reduced the harmonic content to 2.43% from 21.13%.

Sequence Measurement-Based Islanding Detection of DGs in Microgrid With Enhanced Power Quality

Maintaining the power quality (PQ) of supply in a microgrid is a challenge due to the massive integration of inverter interfaced distributed generators (IIDGs). Supply’s PQ and IIDG controller’s transient performance degrade due to continuous, uncontrolled, and nondecaying injections in active methods for islanding detection. Also, active methods have limited application due to increased total harmonic distortion (THD) of current during microgrid’s operation. In this article, a novel sequence measurement-based identification of grid disturbance by sensing voltage and current is proposed to control the disturbance injection cycle in the IIDG controller during islanding detection. The disturbance is a low-frequency decaying current injection in the IIDG controller with controlled input. The proposed method is experimentally verified in controller hardware in loop (CHIL) with real-time digital simulator (RTDS) using the TMSF28335 microcontroller and compared with several previous methods. The impact on PQ due to change in the injection points with controlled and uncontrolled injections is also analyzed. The results indicate that the islanding detection time is low. Also, the proposed closed-loop method is effective and reliable due to two-stage screening. The nondetection zone (NDZ) is eliminated with negligible impact on the PQ of supply.