Reactive Power Compensation System Research Articles

THE STRUCTURE OF THE ADAPTIVE POWER COMPENSATION SYSTEM

The article is devoted to the construction of models of an adaptive reactive power compensation system. To solve the problem of synthesizing the system, a reactive power compensator circuit with analog calculation of the capacitance of the capacitors was chosen. The article reflects the following questions:  - the analysis of compensator circuits to reduce losses from reactive power in electrical networks was carried out;  - developed a graphical information model of the reactive power compensator with analog calculation of the capacitance of capacitors as an automatic control system;  - made a selection of system elements;  - an optimal structural diagram with optimization of parameters was created.     &nbsp

MATLAB Simulation Research on Static Var Compensator

TCR-TSC static reactive power compensator (SVC) is the most widely used in the field of power system reactive power compensation. This type of reactive power compensator can not only compensate the reactive power required in the power system, but also handle the over-compensation problem well. This paper will establish a MATLAB simulation model to simulate the TCR-TSC SVC, focusing on the dynamic reactive power compensation characteristics of the TCR-TSC SVC in suppressing voltage fluctuations. The simulation results show that the TCR-TSC SVC has a better dynamic reactive power compensation effect.

Research on Coordinated Control Strategy of ITER Power Supplies and Reactive Power Compensation System

The stable operation of the ITER power supply is inseparable from the optimal control of the reactive power compensation (RPC, consisting of thyristor controlled reactor and turned filters) system. However, the traditional RPC control scheme with high latency can no longer meet the actual reactive power demand from the load side under the severe working conditions of the plasma control system. A new control law has been proposed and analyzed for RPC system based on the Lyapunov’s theory by designing a Lyapunov function, which derivative is always negatively definite globally. With the help of the Lyapunov’s asymptotic stability analysis, a new controller, which called Q Lyapunov-function-based control (QLC), has been designed to realize good dynamic performance comparing to the existed solutions. The simulation results show that the reactive power consumption of the grid side controlled by QLC has been greatly reduced during the transient change of the reactive power generated by the loads. Hence, the AC busbar voltage will have strong robustness. Moreover, it is also shown that the RPC system can be stabilized globally for handling severe signal disturbances.

Reaktif Güç Kompanzasyonu için Gözetimli Kontrolör Tasarımı

The process of reducing the phase difference between current and voltage as much as possible by balancing the reactive power is known as reactive power compensation. With reactive power compensation, over currents and voltage drops in the transmission lines are prevented and higher quality, cheaper, and more efficient energy is provided. Reactive power compensation is done by switching capacitors with proper values. In a reactive power compensation system, capacitors are switched on and off by a controller. The switching behavior of this system can be characterized as a discrete event system (DES) that has discrete states and the state evolution depends on the occurrence of asynchronous events. In this paper, the control mechanism of a reactive power compensation system is considered in the sense of DES. The system is modeled by using automata and supervisory control structures are computed. The supervisors are obtained by using the supervisory control theory (SCT). Supervisors in the form of monolithic, reduced, and modular are synthesized to correct the power factor. The computed supervisors are also integrated with the system and simulated. The total size of supervisors, ie the total number of transitions and states of each, are compared. The computed supervisors in the form of modular ones have the smallest size. According to simulation results, it is demonstrated that the power factor is successfully corrected by all of the computed supervisors. The presented study shows how to calculate controllers for reactive power compensation systems by using the supervisory control theory. Since the supervisory control theory used in the study is a formal controller computation method, the presented approach enables the computation of formal controllers for reactive power compensation systems. The use of formal methods in the synthesis of controllers offers significant benefits in terms of realization and verification.

An Energy Storage Performance Improvement Model for Grid-Connected Wind-Solar Hybrid Energy Storage System.

This study introduces a supercapacitor hybrid energy storage system in a wind-solar hybrid power generation system, which can remarkably increase the energy storage capacity and output power of the system. In the specific solution, this study combines the distributed power generation system and the hybrid energy storage system, while using the static reactive power compensation system and the conductance-fuzzy dual-mode control method to increase output power in stages. At the same time, the optimal configuration model of the wind-solar hybrid power generation system is established using MATLAB/Simulink software. The output power of the microgrid to the wind-photovoltaic hybrid power generation system is calculated by simulation, and the optimization process of each component of the system is simulated. This study mainly uses the static reactive power compensation system and the conductance-fuzzy dual-mode control method to optimize the wind-solar hybrid power generation system. Using MATLAB software simulation verifies the feasibility and rationality of the optimal configuration of the system.

HARDWARE Implementation of Step-Switched SVCs to Correct Power factor and Mitigate Harmonics for Large DC Variable Loads

The objective of this paper is to develop and implement a complete system for reactive power compensation in railways or high DC power consuming industries. Very high current harmonics are generated, when AC supply is converted to DC to run DC machines, e.g., railway locomotives. Generally, for such applications, static VAr compensators (SVC) are used in combination with passive harmonics filters for mitigating different orders of harmonics. By default, such systems take power factor to high leading side, which must be corrected. To achieve acceptable results, manufacturers switch large inductors and feed chopped voltage waveform to achieve required inductive reactive power to compensate the leading reacting power present at any time in the SVC. This is done at high voltage using thyristors or GTOs, i.e., 11 kV or 33 kV. It is technically a complicated, very expensive technology and needs highly skilled engineers to run and maintain such system. Looking at those problems, better, reliable and technically superior solution is developed to give desired results at much reduced cost. A hardware prototype is developed for 433 V, three phase, 20 A load to obtain satisfactory experimental results.

THE ROLE OF STATIC VAR COMPENSATOR AT REACTIVE POWER COMPENSATION

The need for electricity is increasing and the cost of energy generation is arising. For this reason, it is important to use the generated energy in good quality, safely and efficiently. Reactive power compensation is one of the most effective application to reduce transmission losses, prevent voltage drops, prevent consumers from paying for reactive energy, facilitate operating, increase efficiency and save energy in energy systems. However, due to improvements in semiconductor technology, reactive power compensation systems have gained a new dimension. The power compensation made by the use of semiconductor power elements is called Static VAr Compensation. This compensation is used for the compensation of loads such as arc furnaces, elevators, automotive; paper packaging, food and textile, point welding machines, port cranes, flat welds. Transient events are minimized, losses are reduced, back up possibility, control flexibility and reliability are ensured by using Static VAr Compensation systems in power network. In this study, thyristor triggering angles and power factor values of a system, that contains reactive loads and controlled by Static VAr Compensation, were obtained by using the computer software developed by Microsoft C Sharp (C#) programming language. The results were discussed in terms of importance of using such controlling structures in power networks.

Research on Dynamic Hybrid Compensation Technology and Device in Low Voltage Distribution area of Transformer

In order to solve the problem of three-phase unbalance and low power factor caused by distributed power supply to low-voltage distribution network, a hybrid reactive power compensation system based on “intelligent capacitor +SVG” is designed. The system is composed of a small capacity Static Var Generator (SVG) with high precision compensation and several smart capacitors. Firstly, the structure of three-level SVG in the hybrid compensation system is analyzed, and the two-level SVPWM vector synthesis method is applied to three-level compensation. The control mode of intelligent capacitor is analyzed. Then the principle of reactive power distribution in hybrid compensation system is analyzed. Finally, a hybrid reactive power compensation system is designed with TMS320F28335 as the core controller of the hybrid system. The experimental results show that the hybrid reactive compensation system can effectively compensate the reactive current dynamically.

Voltage and Loss Control for Long Range 10kV Power Transmission Based on Virtual-gap Controlled Reactor

The reactive power compensation problem prevalent in modern power systems makes the power distribution performance not fully utilized and the load power consumption of the equipment increases. According to the operation of the Yulin substation line and the load, the theoretical calculation of the reactive power compensation scheme is developed. The installation capacity, installation position, control scheme of the intelligent magnetic control reactive power compensation system are researched. Through the coordinated control at the beginning and the end of the line, the real-time regulation of the reactive power in the substation and the transmission line can achieve the effect of stabilizing the whole area voltage, improving the power supply radius and power quality. The system finally implemented the stability of the substation voltage and reduced the line loss, made the voltage of the power system stable within the utility required range.

Optimal Allocation of Capacitor Bank for Loss Minimization and Voltage Improvement Using Analytical Method

An electric distribution system plays an important role in achieving satisfactory power supply. The quality of power is measured by voltage stability and profile of voltage. The voltage profile is affected by the losses in distribution system. As the load is mostly inductive on the distribution system and requires large reactive power, most of the power quality problems can be resolved with requisite control of reactive power. Capacitors are often installed in distribution system for reactive power compensation. This paper presents two stage procedures to identify the location and size of capacitor bank. In the first stage, the load flow is carried out to find the losses of the system using sweep algorithm. In the next stage, different size of capacitors are initialized and placed in each possible candidate bus and again load flow for the system is carried out. The objective function of the cost incorporating capacitor cost and loss cost is formulated constrained with voltage limits. The capacitor with the minimum cost is selected as the optimized solution. The proposed procedure is applied to different standard test systems as 12-bus radial distribution systems. In addition, the proposed procedure is applied on a real distribution system, a section of Sallaghari Feeder of Thimi substation. The voltage drops and power loss before and after installing the capacitor were compared for the system under test in this work. The result showed better voltage profiles and power losses of the distribution system can be improved by using the proposed method and it can be a benefit to the distribution networks.

The reactive power demand in DEMO: Estimations and study of mitigation via a novel design approach for base converters

In the present pre-conceptual design, the base converters to supply the main DEMO poloidal magnets are rated for 45 kA and about 10 kV. If the traditional design approach, based on thyristor bridges, was adopted, this would result in very large reactive power exchanged when low voltage values are required by the load. To satisfy the limitations imposed by National Grid Operators, the reactive power should be compensated inside the DEMO Plant Electrical System by means of a Reactive Power Compensation and Harmonic Filtering system. This could represent an additional cost and takes up a large area of the plant. This paper shows that the reactive power demand, estimated with an analytical model starting from the current/voltage waveforms foreseen in DEMO magnets, is huge. Therefore, an innovative approach, based on Active Front End converters, is proposed and compared with the traditional solution for coil power supplies.

Continuous state space model of the ITER pulsed power electrical network for stability analysis

The ITER large power supplies of the superconducting magnets and heating and current drive systems, fed by the Pulsed Power Electrical Network, can absorb from the grid active and reactive power up to 500 MW and 950 Mvar respectively. In this paper, a new analytical approach based on the state space formulation is proposed to investigate the dynamic stability of such complex system, including the main power components and their control, with the aim of identifying possible instability phenomena due to interactions among the ac/dc converters, reactive power compensation systems and related controllers. This model describes the dynamics of the main components of the ITER pulsed power supply systems and it is based on small signal approach to tackle the non linearity of the ac/dc conversion and reactive power compensation systems; the discrete phenomena have been approximated by continuous transfer functions, so the linear control theory can be applied for the stability analysis, making this method very effective and fast. Moreover a modular approach is adopted; thus this analytical model can be also easily adapted to other similar electrical power systems.

Strategy Design and Transient Analysis of ITER PPEN Transformer On-Load Tap Changer During Converter Operation

Three identical three-winding main step down transformers rated at 300/250/150 MVA are installed in ITER Pulsed Power Electrical Network (PPEN) to distribute power to three independent 66 kV and 22 kV busbars for feeding Coil Power Supply System (CPSS). The On-load Tap Changer (OLTC) is installed in primary side of PPEN main step down transformer to limit the voltage in required range under the control of Reactive Power Compensation and Harmonic Filter (RPC&HF) system. A comprehensive OLTC tap changer strategy has been proposed to maintain the 66 kV busbar voltage with consideration of hysteresis band to avoid strategy instability. The circuit models of OLTC tap changer transient processes have been built to analyze the terminal voltage transients quantitatively in both amplitude and phase. And the dynamic performance during OLTC tap transition has been verified to be in accordance with the analysis by simulation. And during future campaign, the most critical situation for CPSS is that the plasma operation system would give step voltage reference from minimum to maximum or vice versa to CPSS according to the operation scenarios. Hence, the converter system operation robustness has been verified by simulation on MATLAB/SIMULINK during PPEN OLTC tap changer transition in the case of this most critical situation during plasma operation.

The Influence of LED Lighting Sources on the Nature of Power Factor

This article presents measurements of electric power absorbed by a newly built facility for office and scientific research activities. These measurements highlighted the need for compensation of capacitive reactive power—not predicted by the designer—due to the vast use of LED lighting in the facility. The article also describes a reactive power compensation system, designed on the basis of the above-mentioned measurements, and the introduced control and measurement system that enables on-site monitoring and online analysis of consumed energy and power. The research was carried out using popular LED lighting sources available on the local market (Poland). Basic electrical parameters of the locally available LEDs were measured as a function of the changes in harmonic levels occurring in the supply voltage. The test illustrated that samples were characterized by a very low power factor, which decreased as the level of harmonic disturbances increased. On the basis of the measurements, the authors suggest that obligatory requirements should be introduced in regard to the minimum power factor at the level of 0.9 for popular LED lighting sources (below 25 W).

Reactive Power Compensation and Negative-Sequence Current Suppression System for Electrical Railways With YNvd-Connected Balance Transformer—Part I: Theoretical Analysis

This paper presents a new system for reactive power compensation and suppression of negative-sequence current for power quality improvement in electrical railways and the feeding three-phase utility grid, based on YNvd-connected balance transformer. Different from the conventional railway static power conditioner based compensation systems, this system integrates multiplex back-to-back converters (MBTBC) into phase- β side flexible taps through a cascade connection instead of into phase- β side feeder via a coupling transformer, thus the installation space and initial costs are reduced significantly. In addition, a new power distribution strategy with simple implementation is adopted in this paper, by which the compensation capacity of MBTBC can be decreased by 25%, compared with the commonly used full compensation scheme. As the first part of this topic, this paper focuses on the theoretical analysis, including the system topology, basic and partial compensation principles and its implementation method. While, the controller design on converter-level, stability analysis, and simulation and experimental verification are the main tasks of the second part of this topic.

Reactive Power Compensation and Negative-Sequence Current Suppression System for Electrical Railways With YNvd-Connected Balance Transformer—Part II: Implementation and Verification

This part mainly focuses on the implementation and verification of the reactive power compensation and negative-sequence current suppression system with YNvd-connected balance transformer, by means of simulation and experiment. The system model is presented, and a current control method, which explores the dissipation characteristic of the proposed system under two-phase rotating frame, is analyzed. Then, a stability analysis of this control is made, considering the deviations of system parameters and the time delay caused by the low-pass filter. Besides, dc-link overall control and balance control are investigated, and the self-balance ability of multiple dc links is briefly discussed. Both the simulation and experimental results verify the effectiveness of the proposed system topology, compensation strategy, and control method.

The Power Characteristic Results According to the Superconducting Magnet Coil Load Tests of the Motor Generator System

When the poloidal field (PF) magnet power supplies (MPSs) of 11 units are operated, maximum power of 200 MVA is required to achieve long pulse operation of Korea superconducting tokamak advanced research (KSTAR). Motor generator (MG) system was installed to resolve the power shortage because the available grid power is only 100 MVA at the National Fusion Research Institute site. MG system is composed of mechanical devices (stator, rotor, bearings, etc.), power control devices (variable voltage variable frequency and exciter), power facilities (transformers, switchboard, uninterruptible power system, filter, dynamic brake, etc.), utilities (cooling water pump, heat exchangers, cooling fans, oil circulation pump, mechanical brake, etc.), and control systems. MG system supplies power to the PF MPS of 11 units. And we configure the reactive power compensator (RPC) and harmonic filter (HF) system to stabilize the MG power system. After installing the MG system, individual tests and dummy coil tests were conducted to determine the safety and performance of MG system. And we completed the commissioning of the MG system by carrying out the superconducting magnet coil load tests for the 2014 KSTAR experiment. MG system was operated up to 150 MVA of PF MPS with the RPC and HF system. And the maximum operating duration was about 100 s. In this paper, we discuss about the power characteristic results of the MG system according to the superconducting magnet coil load tests.

Stochastic optimal allocation of reactive power banks for system loss minimization

In this paper, the problem of power losses minimization is carried out with the aim of attaining minimum power losses in an electrical power system. The current industry practice is to locally install reactive power compensation systems. Using capacitor banks, it can help to maintain bus voltages and power factors as well as reduce the power cable losses, and it can help to meet any future load increase. Currently, due to huge uncertainties affecting some relevant input variables, their accurate evolution forecasting is almost an unfeasible task, with the result that expansion plans frequently are subject to continuous reviews and modifications. In addition, probabilistic analysis, specifically with the application of the Monte Carlo method, is exploited for assessing the attributes of different capacitor banks. Finally, exhaustive numerical results on a real sub-transmission system demonstrate that the proposed formulation and approach are effective. Comparisons of different control techniques are shown, and conclusions are derived.

Research on the Application of Improved Fuzzy-PI Control in STATCOM

According to some shortcomings that Fuzzy PI Control strategy can not meet certain occasions where higher control accuracy is required, the improved Fuzzy-PI control is applied to the static synchronous compensator (STATCOM). Simulating and analyzing the compensation effects of Fuzzy-PI control strategy, improving the membership function of the Fuzzy-PI control strategy, and testing the compensation performances of the improved Fuzzy-PI control with the MATLAB/SIMULINK simulation experiments. The simulation and experimental results show that the improved Fuzzy-PI control can improve the control precision, and can meet the requirements of power system for reactive power compensation better.

Research of Magnetic Bias Control System Based on STATCOM

As the most important style of reactive power compensation system, the research and design control system of static synchronous compensator (STATCOM) is an important aspect of keeping stable and normal operation. This paper analyzes the influences of bias magnetic to STATCOM, and proposes an effective magnetic bias control method and program realization, so reduced to producing two harmonics. It improves the quality and reliability of STATCOM output voltage; Finally, the tests are conducted in the ±500 kVar STATCOM, and the results show the validity and necessity of this compensation method.