A review on techniques for improving power quality: research gaps and emerging trends

ABSTRACT


INTRODUCTION
Power quality (PQ) has emerged as a key issue in the power system in response to the increasing demand for electricity in modern society.Adjustable speed drives (ASD), energy-efficient lighting systems, and programmable logic controllers are examples of power electronics products that are increasingly in use and are blamed for degrading power quality [1]- [5].Power quality is enhanced in several ways: dynamic voltage stability, decrease of harmonics distortion, lessening of used reactive power and an increase in power factor [6]- [13].There are voltage waveform disturbances being generated because of the non-linearity of all these loads.Current harmonics are reduced by the filter and their efficiency is measured under both balanced & unbalanced nonlinear loads [14]- [20].Technological progress, along with globalisation of the corporate sector, has led to a decline in the profitability of many business operations.Power quality concerns are becoming a major factor for acceptability in each activity area due to the increasing sensitivity of the processes engaged in in businesses, residences, and services.Industries and IT services that rely on continuous processes are particularly vulnerable to poor power quality [21]- [24].In recent years, many solutions have been proposed to address power quality issues.Power conditioning systems, power filters, and other tools are used to improve the quality of the electricity [25]- [28].

METHOD REASONS FOR DEGRADATION IN POWER QUALITY
As we've seen, the non-linear load introduced into the power source by electronics and drives can cause problems with power quality, which in turn can cause electrical devices used by end users to malfunction, fail, or simply stop working.Therefore, power quality degradation impacts sensitive equipment for a variety of reasons.The few causes of poor power quality are as follows (as shown in Figure 1).The various reasons for degradation in power quality are depicted in Table 1 (in appendix).

SOLUTIONS TO POWER QUALITY PROBLEMS
Power quality problems can be solved by utilising distributed generation and energy storage technologies.Isolating the power disturbances can be aided by using the correct interface devices.Power conditioners, such as surge suppressors, power filters, and so on, are explored in more detail below.After a decade of study, scientists have developed a wide variety of PQ enhancement devices that are crucial in addressing the issues [17], [21], [29], [33].The solutions to power quality problems are listed in Surge suppressors for electric current are the cheapest and least complicated way to improve power quality.Transient voltage can be restrained by the suppression before it affects the load or equipment, which is why these devices are typically used to integrate with a power supply and other sensitive loads.Non-linear resistance in a transient voltage suppressor controls the surge and grounds the system.

Filters
Power quality is enhanced by using the filter, which is one of them.Filters for noise and harmonics are crucial in helping to eliminate interference from undesired currents and voltages of different frequencies.
The noise filter has a low impedance channel between frequencies thanks to its integrated circuit comprising a capacitor and an inductor, which prevents the undesired signal from reaching the equipment.

EXISTING RESEARCH METHODOLOGIES FOR POWER QUALITY IMPROVEMENT
Recently developed and introduced methods for improving power quality are highlighted.Recent journal papers are considered from IEEE publications to complete the review.Hybrid power filters (HPF) are being used in novel ways to solve the problem of poor power quality (PQ).Table 3 (in appendix) provides a summary of the methods employed and a review of the literature on power quality concerns.

RESEARCH GAP
After looking at the research that has been done and is being done in the field of improving power quality and reducing harmonics, several research gaps have been found.-Lack of adequate approaches: existing research in a variety of fields has been shown to be somewhat ineffective when subjected to nonlinear, dynamically fluctuating loads.-Insufficient use of methods based on fuzzy logic: the majority of the already published research is concerned with more conventional approaches, such as PI controllers.According to the survey findings, the use of fuzzy logic in the development of works is quite uncommon.-Insufficient use of neuro-fuzzy methods: a lot of focus in recent research has been placed on either fuzzy or neural network techniques.Recent studies have shown less interest in neuro-fuzzy methods.-More APF-based strategies: the focus of modern research has been on APFs, not hybrid power filters.
-Total harmonic distortion (THD) minimization is the subject of almost no research.-Hardware implementation using FPGA and the neuro-fuzzy logic approach is quite unusual.

THE STATE OF THE ART IN THE RELATED AREA OF RESEARCH
An in-depth analysis of the latest advances in power quality improvement and harmonics reduction is conducted using metadata from IEEE Xplore publications between 2010 and the present.The results of an investigation using the keywords "power quality + harmonics" and "power quality + active power filter" are presented in Table 4. Figure 3 provides a graphical depiction of the computed research status, which may be seen in Table 4 as an abundance of journals, conferences, early access articles, standards, books, magazines, and courses.devoted to IEEE-published research.The current state of the art in the area of power quality is outlined in Table 4.

CONCLUSION AND FUTURE WORK/SCOPE
The current global power supply is inadequate and cannot keep up with the ever-increasing demand for electricity.Furthermore, complexity at the load end is becoming more of an issue as electronic gadgets become increasingly commonplace.The poor quality of the electricity also causes power equipment to malfunction or the power system to fail.It is crucial for customers to take preventative measures to overcome these issues and avoid financial losses due to PQ issues.This paper presents several contributors to power quality deterioration, as well as recent studies aimed at improving power quality, the research gaps revealed by this analysis, and the existing state of the art in this research domain, which includes many issues that have yet to be adequately addressed.In addition, this review paper might be used as a springboard for further study in the future: i) applying analytic techniques to the design of a hybrid power filter, ii) a neuro-fuzzy based controller has been designed for a hybrid power filter to improve power quality, lower THD, and suppress harmonics, iii) a FPGA with the neuro-fuzzy logic method may be used to develop a prototype of hardware.

Power quality issue Remarks Voltage spikes or surges
Non-linear loads can cause a spike in demand that lasts for a short period of time (known as a surge) Huge power equipment may be shut off if the voltage suddenly rises over the standard.Surge suppressors, voltage regulators, and power conditioners can be used to mitigate the damaging effects of such spikes and surges.

Voltage swell
Voltage swell is a phenomenon when voltage increases rapidly, beyond the typical range in a matter of seconds.Due to inefficient management, this increase in demand has resulted in a few related problems.It's possible that the system will malfunction, resulting in broken sensors, and lost data.

Voltage dips
Voltage sags and dips describe temporary periods of low voltage.Consumers may notice annoying things like lights that flicker or loads that trip.Voltage sags occur when the supply voltage drops and then quickly recovers.These drops originate from the beginning of large loads and the provision of inductive loads.Power quality issue Remarks High-voltage spikes Surge suppressors, voltage regulators, and power conditioners may all be used to dampen down these spikes.It's possible that the fault in the electrical system may cause data loss and malfunction.

Harmonic distortion
Welding equipment, DC brush motors and other high-intensity loads are major contributors to harmonic distortion.Increased distortion results from the usage of nonlinear load producing devices, such as electronic equipment.This might lead to cable overheating, performance degradation, erroneous metre reading, and other undesirable outcomes.

Frequency variation
Frequencies vary from 50 Hz-60 Hz in different parts of the world.Devices like surge suppressors, voltage regulators, power conditioners, and so on can mitigate this.Frequency drift is the result of incorrect frequency sources or the unexpected behaviour of generators.Electrical line noise Electromagnetic interference (EMI) and radio frequency interference (RFI) are to the circuits of electronic devices what static electricity is to electrical wiring.EMI and RFI can be tamed with surge suppressors, voltage regulators, power conditioners, and other similar tools.

Power sag
System failures are the most common cause of sages, which can trigger load switching that requires substantial starting currents.Surge suppressors, voltage regulators, power conditioners, and other similar tools are all good ways to stop this kind of power change in a PQ.

Very short interruptions
The opening and shutting of protective devices during the decommissioning of a malfunctioning network causes brief interruptions that, on the great scale of things, can be deemed negligible.Since this happened, we've had insulation problems, lightning strikes, and so on.This disruption might cause problems with the protection system, and data integrity.

Long interruptions
Disruptions that last longer than two seconds fall under this category.Power outages can occur for a variety of reasons, including mechanical failure, the contact of foreign items with electrical wiring, human error, and many others.Power quality APF Better PQ [3] Voltage profile + power losses

Distribution generation units
Reduction in voltage deviation and faults [4] Power quality RL algorithm The current-base controller sends signals through the q-axis and zero-axis of VSC current controllers to compensate for uneven DR load current, while the voltage controller monitors PCC voltage magnitude and DSTATCOM's reactive power setting point.[5] Power quality Fuzzy logic After compensating for the non-linearity of the load, the source current is sinusoidal, and the DC link voltage is stable, as demonstrated by the steady-state response of the suggested filter.[6] Harmonics Fuzzy based vector PI controller Comparing the results of the three schemes presented in this paper-one without a filter, one with a hybrid power filter, and one with a fuzzy interface.[7] Power quality Solar-DSTATCOM Overvoltage, VU, Dip, swell, and harmonics were all identified as being negatively impacted by PV units.[8] Power quality DVR Load voltage remained stable at its nominal value.[9] Power quality D-FACTS Dynamic voltage stability [10] Power quality FACTS technologies This study provides a complete review of FACTS/D-FACTS technology as well as its implementation in new electric utilities that integrate RESs using power electronic converters.[11] Power quality Fault current limiter (FCL) and a dynamic voltage restorer (DVR) The FCL is able to keep the DG-short-circuit grid's magnitude at a safe level.When it comes to supplemental compensation, the proposed DVR is a cost-effective compensator.[12] Power quality Dual voltage source inverter The suggested approach can correct for local imbalanced and nonlinear load in addition to exchanging power between DGs. [13] Power quality custom power devices such as D-STATCOM, UPQC, UPS, TVSS, and DVR.
Issues with DC power quality are the primary topic of this study, along with related standards, potential solutions, and a brief history of the subject.[14] Power quality PI controlled SAPF Harmonic reduction in balanced & unbalanced nonlinear loads.[15] Power quality Hysteresis current control technique Adaptive reduction of higher cognitive harmonics and suppression of dominant harmonics make HAPF one of the most effective methods for delivering clean electricity to end users.[16] Power quality Power electronic generation Better power quality [17] Power quality Unified power quality conditioner Enhanced power quality

Figure 1 .
Figure 1.Causes of poor power quality

Table 2 .
Solutions to power quality problems

AC Mains Non- Linear Loads Series Active Power Filter Vdc IL IS VAF AC Mains Shunt Active Power Filter IL,abc LS PCC Non-Linear Loads IS,abc IC,abc AC Mains Shunt Active Power Filter IL,abc LS PCC Non- Linear Loads IS,abc IC,abc Passive Filter Hybrid (a) Shunt Active Power Filter (c) Hybrid Filter (b) Series Active Power Filter AC Mains Non- Linear Loads Series Active Power Filter Vdc IL IS VAF AC Mains Shunt Active Power Filter IL,abc LS PCC Non-Linear Loads IS,abc IC,abc AC Mains Shunt Active Power Filter IL,abc LS PCC Non- Linear Loads IS,abc IC,abc Passive Filter Hybrid (a) Shunt Active Power Filter (c) Hybrid Filter (b) Series Active Power Filter AC Mains Non- Linear Loads Series Active Power Filter Vdc IL IS VAF AC Mains Shunt Active Power Filter IL,abc LS PCC Non-Linear Loads IS,abc IC,abc AC Mains Shunt Active Power Filter IL,abc LS PCC Non- Linear Loads IS,abc IC,abc Passive Filter
 ISSN: 2302-9285 Bulletin of Electr Eng & Inf, Vol.11, No. 6, December 2022: 3099-3107 3102

Table 4 .
Current state of the art in the research domain

Table 1 .
Reasons for degradation in power quality (continue) Under voltagesUndervoltage is an electrical problem where equipment needs to draw more current to keep the output voltage constant.Problems with overloading are caused by low voltage, which is caused by loads with low power factors.This can be caused by improper tapping of transformers and a faulty voltage regulator.

Table 3 .
Summary of existing research