Power Quality Improvement in Solar Powered Standalone System using D-STATCOM

Power is an essential source for daily life. The way time is progressing, our power needs also increasing but the main concern in the power system is the reliability of supply which means continuity of power supply with improved power quality. Maintaining the sinusoidal bus voltage at the requisite magnitude and frequency improves power quality, and FACT's (Flexible ac-transmission system) devices are effective in improving power quality with good power transfer capacity. Overvoltage, voltage swell, harmonic distortion, and other issues with power quality exist. The power quality issues can be addressed with the use of FACT devices. The paper's main goal is to analyse the performance of a grid- connected hybrid solar photovoltaic power system with UPFC (Unified Power Flow Controller). A grid-connected solar power system is configured with a PV array, boost converter, voltage source inverter (VSI), UPFC, etc. The Unified Power Flow Controller (UPFC) is utilised with MATLAB/SIMULINK to fix the power quality issue and improve the output of the proposed model.

This paper addresses two issues in operation of a unified power flow controller (UPFC), enhancement of fault recovery and controller design accounting for filter dynamics. Performance of a UPFC is improved by a temporary modification of the UPFC into double static synchronous series compensator (SSSC) in order to double its capability in fault recovery mode. A battery is required as an energy source in the DC link of the double SSSC. The size of the battery for the SSSC has been be investigated. It was found that the double SSSC in fault recovery mode has almost twice the performance of the UPFC and the size of battery for the UPFC is reasonable for grid scale use. With the double SSSC in fault recovery mode, a combination control mode is suggested for the UPFC. One of the important parts of the UPFC is the filter at the output of the inverter. The function of the UPFC filter is to attenuate the harmonics generated by the inverter. In this paper a harmonic trap filter together with a low-pass filter are applied to the UPFC and investigated. Single-phase models are used to design cut-off frequencies whilst the d-q model is included in the UPFC controller design. It was found that if the filter dynamics are neglected in the control design, then the controllers response will be different. The test system used is a one-machine, two transmissions lines and an infinite busbar. All of the simulations were implemented using the EMTP. Additionally Matlab and Simulink programming environment were used to provide transfer function simulation for the controller design. The simulation results from both programs are compared.

This paper addresses two issues: enhancement of fault recovery and controller design accounting for filter dynamics. Performance of the unified power flow controller (UPFC) is improved by a proposed modification of the UPFC into a double static synchronous series compensator (SSSC) in order to double its capability in fault recovery mode. A battery is required as an energy source in the DC link of the double SSSC during the recovery. The battery will be charged during normal operation of the UPFC. The size of the battery for the SSSC has been investigated. It was found that the double SSSC in fault recovery mode has almost twice the performance of the UPFC and the size of battery for the UPFC is reasonable for grid scale use. One of the important parts of the UPFC is the filter at the output of the inverter. The function of the UPFC filter is to attenuate the harmonics generated by the inverter. In this paper, a harmonic trap filter, together with a low-pass filter, are applied to the UPFC and investigated. Single-phase models are used to design cut-off frequencies whilst the d-q model is included in the UPFC controller design. It was found that if the filter dynamics are neglected in the control design, as is often seen in simulation studies, then the controller's response will be different. The test system used in this work is a one-machine, infinite bus bar system. All of the simulations were implemented using the Electromagnetic Transients Program (EMTP) which is a powerful simulation tool for power system simulation. In additional, the Matlab and Simulink programming environment were used to provide transfer function simulation for the controller design. The simulation results from both programs are compared.

The Electronic based FACTS controllers are static equipment. Its principle purpose is to control AC transmission. The parameters of FACTS are enhancement of controllability, ability of power transfer, control of line impedance, load angle and the magnitude of bus voltage. A unified power controller is to be a static device and this system device should have quick reactive transmission. This paper focuses on the issues like voltage sag and swell of power quality. HPFC is used to moderate the voltage variation and improve power quality and also used tocouple the phase controllable bridges to produce current which is injected into a transmission line by using series of transformers. The UPFC is a combination of a static synchronous compensator (STATCOM) and a static synchronous series compensator (SSSC)which is coupled with common DC link. The HPFC eliminates the common dc link between the shunt and series converters and alsoit performs in transmission line to exchange real power between converters at the 3 rd harmonic frequency. The HPFC employs. Several 1-phase converters like D-FACTS concepts as the seriescompensator .These concepts reduce the rating of the components and offer a high reliability. Since the HPFC can immediately control the active and reactive power flow and the voltage magnitude, it implies a great potential for power oscillation damping. The case study contains a HPFC located in an exceedingly single-machine infinite bus power grid with 2 parallel transmission lines that simulated in MATLAB/Simulink. Keywords— Power Quality, voltage Sag and voltage Swell, Unified Power Flow Controller, Hybrid Power Flow Controller.

Integrations of renewable energy (RE) sources like wind energy and solar energy to utility grid affects quality of electrical power. Utility operators have to ensure a good quality power supply and their services to retain the existing consumers or attract the new consumers. An effective system for monitoring and improvement of power quality (PQ) can help to achieve this task. The improvement of PQ can be achieved by using the distribution static compensator (DSTATCOM) in utility grid. This research work presents a control design using synchronous reference frame (SRF) theory to provide efficient control to the DSTATCOM for PQ improvement in utility grid in the presence of solar PV energy. A capacitor and battery bank is used as the DC bus in the design of DSTATCOM. The DSTATCOM has been implemented for improvement of PQ with solar PV energy during various operational events. The events considered include the tripping/reclosing of feeder, switching ON/OFF of capacitor bank, switching ON/OFF of inductive-resistive (LR) load. Proposed study is carried out using MATLAB/Simulink software with the help of an IEEE-13 bus test system. Proposed study is performed using a test system comprising of voltage source and load integrated on point of common coupling (PCC).

Proportional and Integral (PI) controllers are usually accustomed for the control operation of Distribution Static Compensator (DSTATCOM) for the distribution system. However, since the system is very nonlinear and subject to numerous disturbances, the PI controlled DSTATCOM cannot offer optimum performance for various operation points. Additional controllers like the Instant Power Theory (IPT) supported fuzzy logic approach is needed for the DSTATCOM to supply adequate dynamic current control and to enhance power quality and stability of the distribution system. This paper presents the planning of fuzzy logic Controllers (FLC) of a DSTATCOM for improving power quality for a distribution system. The IPT based FLC for the DSTATCOM is used for improving the power quality and the dynamic performance of a distribution system is compared with a DSTATCOM controlled IPT based PI controller. The performances of the DSTATCOM controllers are evaluated throughout grid-side currents with linear and non-linear loads of the distribution system. Simulation results show that the DSTATCOM with IPT based FLC will improve the power quality by reducing reactive currents and harmonic currents with higher system dynamic performance than the DSTATCOM with IPT based standard PI controller.

Power quality improvement in distribution network using DSTATCOM with battery energy storage system

The flexible ac-transmission system (FACTS) family called distributed power flow controller (DPFC). The DPFC is derived from the unified power flow controller (UPFC) with eliminated common dc link. The active power exchange between the shunt and series converters, which is through the common dc link in the UPFC, is now through the transmission lines at the third-harmonic frequency. The DPFC is to use multiple small size single phase converters instead of large size three phase series converter in the UPFC. The large number of series converters provides redundancy, thereby increasing the system reliability. As the D-FACTS converters are single phase and floating with respect to the ground, there is no high voltage isolation required between the phases. The cost of the DPFC system is lower than the UPFC. The DPFC has the same control capability as the UPFC, which comprises the adjustment of the line impedance, the transmission angle, and the bus voltage. Due to the high control capability DPFC can also be used to improve the power quality and system stability, such as low frequency power oscillation damping, voltage sag restoration or balancing asymmetry.

Flexible Alternating Current Transmission Systems (FACTS) got in the recent years a well known term for higher controllability in power systems by means of power electronic devices. FACTS devices can effectively control the load flow distribution, improve the usage of existing system installations by increasing transmission capability, compensate reactive power, improve power quality, and improve stabilities of the power network. However, the location and settings of these devices in the system plays a significant role to achieve such benefits. This work presents the application of Real Coded Genetic Algorithm (RGA) and Particle Swarm Optimisation (PSO) for finding out the optimal locations, and the optimal parameter settings of multi type FACTS devices to achieve maximum system loadability (MSL) in the power system. The FACTS devices used are Thyristor Controlled Series Capacitor (TCSC) and Unified Power Flow Controller (UPFC). The reactance model of TCSC and the decoupled model of UPFC are considered in this work. The thermal limits of the line and voltage limits of the buses are taken as constraints during the optimization. Simulated Binary Crossover (SBX) and Non-uniform polynomial mutation are employed to improve the performance of the Genetic Algorithm used. Simulations are performed on IEEE 6 bus and 30 bus power systems. The obtained results are encouraging and show the effectiveness of RGA over PSO algorithm

Flexible AC Transmission System (FACTS) controllers are advanced power electronic devices employed in electrical power systems to enhance system stability, reliability, and power transfer capabilities. These controllers enable dynamic and flexible control of various transmission parameters such as voltage, current, impedance, and phase angle, thereby improving the overall power system performance. FACTS devices are broadly classified into series, shunt, series- series, and series-shunt configurations, each designed to manage reactive power and regulate voltage either by injecting voltage in series or current in shunt with the transmission line. Well-known FACTS devices include Static Var Compensators (SVC), Static Synchronous Compensators (STATCOM), Thyristor Controlled Series Capacitors (TCSC), Static Synchronous Series Compensators (SSSC), and Unified Power Flow Controllers (UPFC), each serving specific roles in power flow control, voltage regulation, and transient stability enhancement. The integration of these controllers provides significant benefits such as increased transmission line capacity, improved voltage stability, minimized transmission losses, and damping of power system oscillations. They are capable of rapid response during transient disturbances, effectively mitigating voltage collapses and enhancing system resilience against faults and contingencies. FACTS controllers not only improve steady-state operational parameters but also address dynamic stability and transient conditions, enabling power systems to operate closer to their stability limits while maintaining security. Their deployment helps avoid costly infrastructural expansions by optimizing existing transmission assets, which is critical given environmental and economic constraints. Recent advances in semiconductor technologies and control algorithms have made FACTS devices more reliable, efficient, and adaptable to modern grids, including renewable integration and deregulated power markets. In summary, FACTS controllers play a vital role in modern power systems by providing flexible, efficient, and reliable solutions for power flow management, voltage control, and system stability enhancement, thereby supporting the evolving demands of today's complex electrical networks.

Most of the pollution issues created in power system is due to the power quality problems like faults, harmonics etc. In this paper a grid connected fixed speed wind turbine induction generator subjected to asymmetric fault gets attenuated by unified power flow controller (UPFC) as it compensates the positive and negative sequence voltages thereby reducing the torque oscillations and improving the life time of the drain. It is the combination of static compensator (STATCOM) and static synchronous series compensator (SSSC). The control theory is based on vector control- dq(direct quadrature axis) reference frame fed PI, hysteresis control and fuzzy logic control using DSOGI-PLL(Dual second order generalized integrator- Phase locked loop). The proposed system is implemented using MATLAB / SIMULINK platform with and without Unified power flow controller. The effect of UPFC for fixed speed windturbine under faults is analysed using the above three controllers and its performance is evaluated.

Today, there is a large increase in the demand for electricity. The transmission and distribution networks, however, cannot fulfill unbound demands due to the scarcity of resources. Power lines have losses which make the situation more unfavorable for maximum power transfer. Implementing a flexible AC transmission system (FACTS) is one of the best ways to reduce line losses. This paper proposes a FACTS-based method for minimizing the fault current in the system. Switchgear and protection equipment also perform better when this is done. Moreover, due to the reduced fault current of the switched system, a larger amount of power can be transmitted. Static synchronous series compensator (SSSC), static synchronous compensator (STATCOM), and unified power flow controller (UPFC) are evaluated in this case. With STATCOM and UPFC, fault currents are significantly reduced. Furthermore, STATCOM and UPFC can also reduce the fault currents in the power system in addition to voltage regulation and power flow control. A MATLAB/Simulink model is used to evaluate the model’s feasibility.

<b>Problem statement:</b> Modern power system consists of the complicated network of transmission lines and carries heavy demand. Thus they cause in the stability problem. <b>Approach:</b> Static Synchronous Series Compensator (SSSC) is a power electronic based device that has the capability of controlling the power flow through a line. The series voltage injection model of SSSC is modeled into power flow equation and thus it is used to determine its control strategy. This study applies the fuzzy logic applies the SSSC to improve stability of power system. The mathematical model and control strategy of a SSSC are presented. The SSSC is represented by variable voltage injection with associate transformer leakage control to derive control strategy of SSSC. The swing curves of the three phase faulted power system without and with a SSSC is tested and compared in various cases. <b>Results:</b> The swing curve of the system with SSSC based fuzzy logic control has the less amplitude during the dynamic period. <b>Conclusion:</b> It was found from simulation results that SSSC can improve the power system oscillation after disturbance.

The electrical power is transmitted through a high-voltage transmission system to low-voltage consumers on the distribution side. Because of the high R/X ratio, high current, and low voltage in distribution systems, active power loss (TPL) is much higher as compared to transmission systems. The economic incentive for distribution power utilities is to reduce losses in their networks. This inducement is generally the cost differential between actual and standard losses. As a result, when actual losses exceed standard losses, the utilities are economically penalized, while when the reverse happens, they are getting benefitted. As a result, the loss minimization problem in distribution systems is an excellent research subject for academics. All the methods for the loss minimization are different from each other by the means of formulation of the problem, tools used to minimize the losses, constraints taken, solution methods, and results are obtained. In most of the cases, the distribution system is interconnected and due to increment in load demand and limitations of loading capacity of distribution lines, the idea of distribution side generation came to maintain the system parameters like voltage profile, power loss, cost of operation, etc. To minimize losses, several methods are available like distributed generation (DG) using renewable energy sources and combined heat and power systems, capacitor allocation, reconfiguration of the network, and D-FACTS devices like dynamic voltage restorer (DVR), distribution static compensator (D-STATCOM), unified power quality conditioner (UPQC) allocation, etc. In this chapter, 33 and 69 bus mesh distribution system analysis is proposed with implementation of multiple wind turbines (WT) and multiple D-STATCOM. Advantages of WT are cost-effective generation, clean fuel source, sustainability, and less land requirement. Here, the Artificial Bee Colony (ABC) algorithm is used for finding optimal size and location of WG and D-STATCOM. ABC is an optimization technique that offers population-based search procedure in which artificial bees change individual food locations over time, with the aim of the bees being to locate the places of food supply with the most nectar and recognize it as the one with the greatest nectar. Here direct approach-based load flow method is used to find load flow parameters like bus voltage, branch currents, and power loss. The outcome verifies effective improvement in the system voltage profile, reduction in distribution feeder line loss, and increment in cost savings.

Modern electric power systems are large and complicated, and, in many regions, the generation and transmission systems are operating near their limits. Eigenanalysis is one of the tools used to analyze the behavior of these systems. Standard eigenvalue methods require that simplified models be used for these analyses; however, these simplified models do not adequately model all of the characteristics of large power systems. Thus, new eigenanalysis methods that can analyze detailed power system models are required. The primary objectives of the work described in this report were I) to determine the availability of eigenanalysis algorithms that are better than methods currently being applied and that could be used an large power systems and 2) to determine if vector supercomputers could be used to significantly increase the size of power systems that can be analyzed by a standard power system eigenanalysis code. At the request of the Bonneville Power Administration, the Pacific Northwest Laboratory (PNL) conducted a literature review of methods currently used for the eigenanalysis of large electric power systems, as well as of general eigenanalysis algorithms that are applicable to large power systems. PNL found that a number of methods are currently being used for the this purpose, and all seem to work fairly well. Furthermore, most of the general eigenanalysis techniques that are applicable to power systems have been tried on these systems, and most seem to work fairly well. One of these techniques, a variation of the Arnoldi method, has been incorporated into a standard power system eigenanalysis package. Overall, it appears that the general purpose eigenanalysis methods are more versatile than most of the other methods that have been used for power systems eigenanalysis. In addition, they are generally easier to use. For some problems, however, it appears that some of the other eigenanalysis methods may be better. Power systems eigenanalysis requires the computation of eigenvalues of nonsymmetric matrices. Such computations are fairly difficult, however, and they constitute an area of active research. Thus, research in this area should be closely monitored, and, as new methods become available, they should be tested on large power systems. PNL also investigated the use of vector supercomputers to enlarge the size of power systems that can be analyzed by MASS, a standard power system eigenanalysis code. MASS was converted to run on a Cray supercomputer. On a conventional computer, MASS is limited to power system problems with about 500 states because of computer time constraints. Running MASS on a Cray X-MP EA/232, however, PNL found that a problem with about 2200 states could be solved in about 26 minutes. Furthermore, by moving to a larger Cray, it should be possible to use MASS to analyze power systems with 5,000 to 10,000 states. Problems with 5,000 states would probably take about 5 Cray hours, while a problem with 10,000 states would probably take about 43 Cray hours, though the actual execution times will depend on the type of Cray used. Problems requiring 5 Cray hours are not uncommon. Problems requiring 43 Cray hours, however, would be fairly expensive. Thus, power systems with about 5000 states probably represent an upper limit on the size of problems that one would want to routinely solve using a Cray version of MASS.