Power Quality: Infrastructures and Control

In this chapter, the different configurations of wind energy conversion system (WECS) are discussed. The permanent magnet synchronous generator (PMSG)-based WECS control is elaborated in detailed. The comprehensive modelling of wind turbine and permanent magnet synchronous generator is studied. The detailed control of machine side converter and grid side converter is explored to extract maximum power from wind turbine and to improve the power quality of the distribution grid, respectively. Various advanced control strategies are analysed including proportional-integral (PI) controller, phase-locked loop (PLL)-based technique, fuzzy logic-based controller, Kalman filter-based control, etc. The detailed implementation of these control strategies is discussed to adhere to the IEEE standard 519 and IEC standard 61,727. In addition, the robust algorithms are discussed to deal with abnormal grid scenarios and illustrative examples with MATLAB/Simulink models (version: 2020b) are also provided with this book.

Wind energy as DG from the wind farm is applied to the distribution system for loss minimization. In the wind farm, the downstream wind turbines experience a reduction in wind speed due to the upstream turbines ahead of them. Wind wake has a significant impact on wind turbine efficiency. Single and multi-wake effects are considered during the effective wind power calculation. A new irregular infrastructure of the wind farm is designed to have maximum wind power extraction with minimum wind wake loss and wind farm area. The hourly data distribution pattern of wind speed is non-parametric. This issue proceeds to the implementation of Kernel Density Estimation technique to the thesis work. Load Impedance Matrix method is implemented to the distribution system for load flow analysis. Daily load variation and air density are applied to the distribution system for an approach towards a practical system. IEEE-28 and IEEE-69 bus systems are studied for the active power loss reduction.

The problem of global climate change has intensified the efforts for minimizing the use of fossil fuels to reduce the associated carbon footprint.

Power quality (PQ) is an important issue in power systems that reflects a measure of quality of energy supply to the consumers. Power electronics-based equipment is increasing in power systems that cause voltage distortions which may damage a sensitive appliance in the distribution grid. Besides, many electrical and electronic equipment is susceptible to power supply disturbances in modern industrial establishments. The most vital power quality issues affecting large commercial and industrial customers are momentary power interruptions and voltage sags. Usually, these PQ issues are associated with the faults that occur in the supplying power systems. Voltage sags are very common since they can be associated with the faults that happen remotely to the customer. Further, these PQ problems with about 4–5 cycles may cause an extensive malfunction to the sensitive equipment. Therefore, an appropriate solution is necessary to handle this problem. A Dynamic voltage restorer (DVR) is a custom power device (CPD) that can protect sensitive equipment against voltage disturbances and improve power quality in electrical distribution systems. In recent years, many CPDs have been developed to meet the need of the industries and their critical load establishment. The DVR is one of the most promising CPDs used to improve the power quality before feeding it to the sensitive load to protect electric appliances from damage. DVR is the combination of a voltage source inverter (VSI), which can impose the voltage in series through a series injection transformer (SIT) with the power distribution system during voltage sag. The required voltage compensation can be achieved by adopting the pulse width modulation (PWM) technique for VSI. The DVR's performance mainly depends upon the control system that includes voltage disturbance detection, reference generation, voltage & current control and PWM switching strategy. The main objective of the control system is to compensate for the disturbance at the earliest using a fast detection technique, optimum control variables for the control circuit and a suitable PWM switching methodology. Many such compensation methods and control techniques are proposed in the literature along with various DVR topologies which are analysed and studied in this chapter.

In the distribution network, the power quality of an electrical supply plays a vital role for the satisfactory operation of home appliances. The electrical power network faces manifold challenges in the system as various kinds of local loads (e.g., constant impedance load, constant power load, constant current load, etc.) are tied at the common coupling point. In addition, the nonlinear loads pollute the supply currents by drawing the harmonic components from the source. This chapter deals with the classification, basic working principle, detailed discussion on various control strategies, and simulation results and analysis. The basic MATLAB model of the UPQC system is also provided in this chapter.

Variable-speed pumped storage power plants (VSPSPP), as opposed to fixed speed pumped storage power plants, use a DFIM in conjunction with a back-to-back converter. Electrical components' nominal equipment parameters are designed for a VSPSPP. Additionally, a traditional vector controller comprises three components: a machine-side controller, a grid-side controller, and a pump-turbine controller. Each path contains an external and an internal loop; therefore, the internal and outer loops are extracted, and the transfer function is extracted to tune the control coefficients; the open- and closed-loop transfer functions of various control sections are extracted from the machine, and grid-side converters, as well as the pump-turbine, and their stability is guaranteed by drawing the root locus diagram.

Renewable energy sources are receiving a lot of attention as a result of the exhaust of fossil fuels and the increase in carbon dioxide emissions. Wind energy and small hydro are popular clean energy sources for supplying electricity in inaccessible and remote areas where the power of the grid is unavailable. This chapter deals with three-phase three-wire and three-phase four- wire integrated voltage and frequency controllers (IVFCs) for isolated (off-grid) pico-hydro power generation. These IVFCs use star/delta, T-connected, zigzag/star, star/polygon, star/hexagon and zigzag/single-phase transformers for optimizing the DC bus voltage and converting three-wire system to four-wire system by connecting the neutral of the load to that of the transformer for neutral current compensation.

This chapter examines the control and design of hybrid off-grid configurations using renewable and non-renewable energy sources (R&NR-ESs). Details relating to power quality, voltage, frequency regulation, and synchronization between off-grid configuration elements are provided. Analyzing and testing a hybrid off-grid configuration based on a solar PV array (SPA) and a variable speed doubly fed induction generator (DFIG) is done to better understand this technology. A rotor side converter (RSC) is designed with improved vector control to vary the speed of the diesel engine accordingly to load power demand, generated power from SPA, and battery charge level. To achieve maximum power point tracking (MPPT) from SPA, an improved Perturb and Observe algorithm (IP&O) is used. Improved oriented stator flux control is designed to maintain constant the PCC voltage and frequency, as well as improve the power quality (PQ) at the point of common coupling (PCC) for load-side converters (LSC). An algorithm based on a proportional–integral controller that prevents the BES from overcharging is employed. Simulations are conducted using MATLAB/Simulink to evaluate the performance of selected hybrid off-grid configurations and their control strategies.

There is a progressive enhancement of sustainable energy sources with the electricity grid, the power converters play an important role to deliver power from sustainable energy sources to the utility grid. With increased penetration of uncertain sustainable energy sources and proliferation of large power electronics-based load on the electrical network, the power quality issues are introduced with the grid supply. The power quality issues such as impulsive, oscillatory, voltage sag, voltage swell, interruption, DC offset, harmonics, interharmonics, notching, etc. The extraction of grid synchronization signals from the grid voltage under these power quality disturbances is a big challenge. This chapter provides various control strategies for extracting the synchronization signals. These control strategies are based on orthogonal signal (OS) generator such as delay-based OS, second-order generalized integrator-based (SOGI), multilayer SOGI (mLSOGI), modified SOGI (mSOGI), enhanced SOGI (ESOGI). Third-order generalized integrator (TOGI), mixed second-order–third-order generalized integrator (MSTOGI), enhanced TOGI (ETOGI), fourth-order generalized integrator (F_oOGI), fifth-order generalized integrator (F_iOGI), multilayer F_iOGI (MLF_iOGI), and modified multilayer fifth-order generalized integrator (mMLF_iOGI). It is also shown that these generalized integrators can be used in proportional resonant (PR) controllers.

In this chapter, a 127-level multilevel inverter (MLI) which is designed for a solar photovoltaic energy unit is proposed and the configurations of 15, 31, and 63 MLIs are also compared with the same topology. The proposed technique while compared with other popular MLIs, it is clear that this model uses very less semiconductor switches to get the most number of steps in the output AC voltage. This topology uses a square wave switching in the place of pulse width modulation, which helps to reduce the switching losses. Since the switches used are minimum, the cost of the system is considerably reduced. The harmonics and the total harmonic distortion are found to be less in the output waveform. This 127-level MLI is simulated in MATLAB/SIMULINK R2009a and the results are compared with 15-level, 31-level, and 63-level MLIs.

The advancements in energy extraction from renewable energy sources as well as the continuous efforts for the electrification of the automobile sector reduces the issues regarding global warming. The reduction in the cost of photovoltaic modules and energy storage system, accelerate the usage of electric vehicles (EV) and energy extraction from solar power. Power electronic converters are required for charging, discharging, and energy management of EVs. Likewise, power converters are required for grid integration and extraction of maximum power from the photovoltaic systems (PVS). In the present work, improved hybrid three quasi z source converter (IHTQZSC) is utilized for grid integration of PVS in a single-stage system providing higher voltage gain. Penetration of PVS and EVs on large scale into the utility can reduce power system stability, security, and reliability. Meanwhile, EVs are encouraged to charge from PVS reducing burden on the utility. Further, EVs are encouraged to provide grid support during the vehicle idle condition (v4G operation), in addition to vehicle to grid (V2G) and grid to vehicle (G2V) operation. IHTQZSC is employed for supporting V2G, G2V, and V4G operations as well as charging EVs and injecting PV power into the grid. A constant switching frequency predictive controller is intended for the controlling of grid side operation of PVS and EV.

This paper presents frequency regulation in a microgrid consisting of wind turbine generator (WTG), photovoltaic (PV), and fuel cell (FC) along with the energy storage system such as flywheel energy storage (FESS) and battery energy storage (BESS). Here, the Ant lion optimization technique (ALOT) is applied to tune the parameters of the proportional–integral–derivative (PID) controller to minimize the frequency deviation in the microgrid system under different operating conditions, namely with and without energy storage elements. The comparative analysis reflects the improvements in frequency deviation in microgrids using the proposed ALOT-optimized PID controllers in the presence of an energy storage system. The different case studies like variations in the propagation delay and increment in load perturbation are performed on the system. The case study on propagation delay provides a more oscillatory response in frequency. The increment in load perturbation shows that the system response deteriorates slightly. The cost function of the system is found minimum when the energy storage system is incorporated.

In recent years, wind energy technology (WET) has been a promising alternative to meet the growing power demand worldwide. This technology is gaining popularity due to its cleanliness and economic attractiveness. Among the various turbine generators (TGs) in WET, the Type-3 doubly-fed induction generator (DFIG) and Type-4 permanent magnet synchronous generator (PMSG) is the most used and technically attractive TGs in large-scale wind power generation. The wind farm consists of several such TGs integrated into the main utility grid and the generated large power is injected through high voltage (HV) long transmission lines (TLs). Therefore, an adequate distance relaying is provided in the long TL for an uninterrupted power supply to the main utility grid. However, the impedance of the TL is greatly affected both during fault and normal conditions due to the nonlinear wind speed versus generated power characteristics, complex control action, and low voltage ride-through capability of the TGs. It confounds the operation of the traditional fixed impedance-based distance relay protecting the TL during fault. These motivate to develop the advanced relaying schemes to provide accurate protection to such TLs. For this purpose, numerous research works have been published over the last decade. The present paper discusses the various impacts of grid-integrated large-scale wind farms on distance relaying-based transmission line protection schemes first. Further, it provides a comprehensive chronological review of the relaying schemes available in the literature to mitigate the protection problems of such wind farm integrated crucial transmission lines. This study may be found useful for future research and to gain insight into the scope of protection of HV-TLs connected to large-scale wind farms for further development.