Introductory Chapter: Power Quality

1. Introduction

Traditionally, power quality has been a critical aspect of electrical engineering and energy management, focusing on the characteristics and reliability of the electrical power supply. The term encompasses a range of factors that collectively define the quality of electrical power as it is delivered from the generation source to end users. Over the years, the understanding and importance of power quality have evolved, reflecting changes in technology, industrial processes, and the increasing sensitivity of modern electronic equipment to variations in the electrical supply.

In the early stages of electrification, the emphasis was primarily on generating and distributing power over long distances. The key concern was to provide a steady and reliable supply of electrical energy to support the growth of industries and meet the increasing demand for electricity in homes and businesses. During this period, the concept of power quality was more centered on maintaining a stable voltage and frequency within acceptable limits. As technology advanced and the types of electrical loads diversified, power quality concerns expanded beyond just maintaining voltage and frequency. The proliferation of electronic devices and the integration of sophisticated control systems in industrial processes introduced new challenges. These challenges included issues related to harmonic distortions, voltage sags, transients, and other phenomena that could negatively impact the performance of sensitive equipment [1, 2]. The advent of information technology further elevated the importance of power quality. Computers, servers, and communication equipment became integral components of various industries, and these devices proved to be highly sensitive to fluctuations in the power supply [3, 4]. Even minor disturbances could lead to data corruption, system failures, and financial losses. This shift in the nature of loads necessitated a more comprehensive approach to power quality management.

Over time, advancements in technology have offered a myriad of solutions to address power quality issues. From the development of sophisticated power conditioning devices to the implementation of smart grid technologies, the field has seen continuous innovation. These technological solutions aim to enhance the resilience of power systems, mitigate disturbances, and ensure a more stable and reliable supply of electricity [2]. In the contemporary landscape, power quality faces new challenges, including the integration of renewable energy sources, the electrification of transportation, and the increasing complexity of interconnected systems [5, 6]. The future of power quality management lies in a holistic and adaptive approach, leveraging cutting-edge technologies like artificial intelligence for predictive maintenance, smart grids for dynamic load management, and energy storage for grid stabilization [7].

2. Traditional challenges

Over the years, traditional challenges related to power quality have persisted, requiring a comprehensive understanding of their causes, impacts, and effective solutions. They include a set of issues that stem from the dynamic nature of electrical systems, technological advancements, and the evolving needs of modern industries [8]. Sagging and swelling of grid voltage, which is also known as voltage variations, can occur due to various reasons such as grid faults, sudden load changes, or system disturbances. These variations can adversely affect sensitive equipment, leading to malfunctions or disruptions. Grid voltage swelling and overvoltage are commonly caused by changes in grid loads, especially large loads, and switching of power line. By conventional definition, a swell is defined as an increase in RMS voltage or current of between 1.1 and 1.8 pu at a duration of power quality ranging within a system frequency of 30 to 60 seconds event. Should the voltage reaches peak values, electrical devices are prone to damages and, in the worst case, permanent malfunction. By definition, an overvoltage is an operating condition where grid voltage is detected to increase and exceed its design limitation. The events that describe this phenomenon are transient, spikes, and so forth, and they can occur in either very short or long durations, depending on their severity of the condition. For example, switching overvoltage usually causes voltage oscillations with high value and high-frequency characteristics and often in short duration. In the cases of neutral conductor breakdown, overvoltage is produced in high voltage and results in long duration disruption, causing permanent damages to the grid. In both swell and overvoltage or sag conditions, the variations of voltage levels have been proven to adversely affect devices and equipment of power grid, whether at supply or load ends, or even at transmission lines. In most severe cases, power lines dielectric properties are compromised and could result in major breakdowns with energy being cut off, machines and motors are not working due to low supply, premature failures of systems’ capacitor, control circuits, and so on could disrupt the grid operations, and so forth. In solving the conditions of voltage varieties (whether they were by design or results of operational issues), voltage regulation exercise is very important. An AVR is an example of devices commonly used in regulating voltage at the grid as it used in generators to stabilize and maintain voltage within acceptable limit. Devices such as surge protector and transient suppressor are installed in many locations at grid system in order to divert overly high voltage to keep grid equipment safe and operational. Voltage regulation can also be achieved by using devices such as tap changers, reactors, static VAR compensators, and so on.

Ever since inventors found alternating current (AC) electrical systems, Harmonics has been a concerning matter, impacting the grid and the electrical devices such as power cable, power transformer, protection relays, and so forth. Harmonics in power system are defined as sinusoidal components of a waveform that have frequencies that are integer multiples of the fundamental frequency of the system. Typically, in most power system, the fundamental frequency is either 50 or 60 Hz. Harmonics are additional frequencies that can be present due to types of loads that are nonlinear in nature. During the early days of AC system, harmonics existed due to the usage of arc furnaces and lightings due to industrialization. As the time goes, the types of loads evolved with more electronics are used in many systems be it at residential, offices, or commercial sites [6, 9]. The impacts of harmonics become more noticeable and significant due to these nonlinear types of loads [6, 8, 10]. In recent times where automations are taking central roles in the world, these nonlinear loads have been used even more such as rectifiers in electric vehicle (EV) applications, inverters in cooling systems, and variable drive systems such as VFD and VSD in machines and motor operations. Industrial processes, commercial operations, and quality of life at homes are undoubtedly improved and efficient; however, these devices draw current in a nonsinusoidal manner, contributing to greater harmonics distortion in power system. The effects of harmonics are profound as they exist in both voltage and current, which result in distortions in voltage or current. This can lead to increased losses in power grid, affecting performance of electronic-based equipment especially. With increases in loss, for example, Eddy current loss, equipment tend to operate with higher temperature than they were ever designed for in the first place. This overheating operation happens at power transformers, capacitors, and power cables and for a prolonged time without interventions; breakdowns of insulation may occur and result in permanent malfunction and breakdown of services [4, 10, 11, 12]. Mitigations on harmonics issues are well-defined over the years, with measures such as installation of harmonic filters and improved design of power transformer, sizing of cables, scheduling of load, and so forth being used. Passive and active filters are often designed to either minimize or simply filter out altogether the harmonics components in the system [4, 9]. By doing this, the nonsinusoidal waveforms are returned to the initial sinusoidal shape or reduced to specific desired threshold values, to be used as input to other devices without the risk of harmonics effects. To control the impact of harmonics to transformers, the design and sizing of the unit are configured to be able to withstand harmonic components. Special winding configuration, heat absorption or heat rejection mechanism, and improved insulations keep transformers operating without the risk of overheating and minimize the impact of harmonics. Several other measures include the scheduling of loads where loads that contribute to harmonics are distributed systematically throughout operational hours to reduce the concentration of harmonics component in the power system. By applying this method, losses due to harmonics are kept at a minimum and at an acceptable threshold value; hence, the risk of thermal overloading is reduced significantly.

3. Challenges in modern times

The advancements in science, technology, and engineering have no doubt contributed immensely to the world. Innovation and inventions through these fields have been the driving force behind solutions to address challenges that were never here before. Globally, discovery of knowledge allows human and societies to gain access to energy, sanitation, water, education, and so forth, which are crucial to transform the lives of billions and propel humanity forward in a sustainable nature.

A sustainable world includes the integration of renewable energy sources in the power system grid. Sources generating power through solar photovoltaic, wind power, and so on produce power into the conventional sourced power system grid, and the numbers are growing in large. These processes are complex and require the use of power electronics, which are loads that are nonlinear in nature. The electronics are used for converting variable outputs of renewable energy sources into a power system for consumption. Converters, rectifiers, and so on are producing distortions in power system current and voltage waveforms, thus causing harmonics to exist and impacting other devices. Renewable energy sources offer numerous benefits to sustainability in life and environment, but their widespread integration into power system grid produces great challenges in the context of power quality. Rapid switching of power electronic devices within inverters, for example, results in distortions and injection of nonsinusoidal current into a power system grid. Of course, the advantages of these applications to the world and people are far more than their advantages. Thus, it is essential for the systems to be designed and understood to ensure stable integration of renewable energy into a power system grid.

Modernization also involves massive use of an integrated system that can seamlessly provide high quality of life in a sustainable way. Transportation sector, which is among the biggest contributors of emissions in the world, opened opportunities for electric vehicles some time ago [13]. Now, the adaption of EV is at the highest peak, where the global EV outlook points to a 35% year-on-year increase with respect to new purchases in 2023 alone [14]. This also means that a wider charging network is being implemented, which, coupled with limit of traveling range and performance of the batteries, poses greater threat to power system grid in general [15]. Demand in electricity, especially during peak charging times, is rising exponentially at a rate never seen before. This means power system authorities and grid owners must manage this massive additional load, probably to allow more generation at the critical duration, and upgrade their transmission lines, transformers, and other infrastructures to cater more power and at the same time operate efficiently and profitably. Proper management of EV charging, perhaps in distributed evenly way can help reducing power system stress, to ensure stability and reliability [16, 17]. EV charging devices are becoming a major source of harmonics in transportation, due to power electronic converters used to convert AC to DC for charging the batteries. It also being extensively used to convert DC to AC, should the charging points utilize solar or wind or any other renewable sources. These converters generate harmonics current during the switching components during their operation. In some studies, there have been suggestions that to balance the need of EV and the negative impact of EV toward power quality, both EV owner and power system authorities/owner habits on this subject need to be adjusted accordingly. For example, charging EV battery with higher SOC could cause less distortion in a power system grid and the vehicle battery, locations of EV charging stations should not be in proximity to power transformers, the numbers of EV charging points are also to be limited to certain extent, and so forth.

4. Power quality – new insight

Researchers and industries have been exploring producing advanced inverter operational methodologies and strategies to control the impact of harmonics. Among others is the development of actively harmonic-blocking inverters, which are strategically distributed along a power system grid for mitigation processes [9, 18]. Monitoring power system parameters such as voltage and current state, power factor, transient conditions, and so on is done continuously to help identify potential issues way before their occurrences for implementing proactive mitigation measures. These measures are already in place nowadays with electrical devices such as relays and transformers being equipped with modern power quality analyzers with advanced capabilities for harmonic analysis, including artificial intelligence (AI) [18, 19, 20, 21, 22]. These are also known as advanced metering infrastructure (AMI), where deployments of smart meters communicate in two ways—collecting information and transferring it to a centralized center and also receiving information from the center for them to execute. AMI is one part of a wider surveillance capacity of a wide area monitoring system (WAMS), which is made of a strategic and synchronized system to view and provide action about dynamics of power system. WAMS provides comprehensive monitoring capability to facilitate greater active maintenance work. AI technologies are increasingly positioned in the field of power quality to enhance the monitoring, analysis, and management of a power system grid. Several contributions of AI into solutions of power quality include data analysis and pattern recognition, fault detection and diagnostics, predictive maintenance, power quality event classification and severity assessment, anomaly detection, and so on [18, 23, 24]. AI algorithms can analyze large datasets—including types of data and number of data—measurements, and pattern and trends are identified to recognize the potential of issues and produce predictions of the likelihood of power-quality events. AI can not only provide future event prediction; it can also be used for real-time fault diagnostics, where signals from sensor and instrument are measured and compared and provide insights of the causes [21, 22, 25]. In short, AI gives an edge of spotting and identifying the anomalies of power system operation parameters, quickly and accurately, round the clock and independently. Prompt investigation and resolution can be carried out, hence ensuring a more resilient and adaptive action. All these characteristics of AI operation give power system grid managers a great capacity, where the system can be made reliable and ready of any eventualities through sophisticated and automated solutions [21, 22, 25].