Reactive Power Compensation Control Research Articles

Development of a model of automatic regulation of reactive power compensation for the oil and gas industry

Reactive power has a significant impact on the parameters of the power supply system in the oil and gas industry; as a result, there is a decrease in the quality of the electric network. The relevance of the study is justified by the tasks of improving the quality of electricity in the load nodes consisting of asynchronous motors, one of which is the reactive power compensation, including the calculation and automatic regulation of compensating devices. The aim of the article is to design and research a reactive power compensation control system to improve the quality of electricity. The article proposes a solution to the actual problem of reactive power compensation based on the proposed power quality control algorithm. The system of automatic control of reactive power compensation developed in the Matlab and Simulink software package allows us to generate parameters according to current measurements and adjust the voltage when the load operation mode changes. The use of MOSFET transistors in the control system made it possible to create the necessary compensation currents with a low content of higher harmonics that create distortions in the supply voltage and ensure high speed of the reactive power compensation unit operation.

A novel protection scheme against turn-to-turn fault of MCSR based on equivalent magnetizing inductance

Magnetically controlled shunt reactor (MCSR) is one of the key equipments applied in EHV/UHV transmission systems for reactive power compensation and voltage control. Due to its special core structure and winding connection mode, the probability of occurrence of turn-to-turn faults is high and the detection is still a challenge. The existing protection schemes have problems of low reliability and sensitivity—the maloperation may happen when MCSR is pre-excited energized, and the fault with less short-circuited turns is difficult to detect. To solve these problems, a novel protection scheme based on equivalent magnetizing inductance (EMI) is proposed. The definition and calculation of EMIs of MCSR are introduced. Based on the parameters of 750 kV MCSR applied in Northwest China, a simulation model in MATLAB/Simulink is built. The variation of EMIs in different scenarios is analyzed through theoretical and simulation and an EMI-based protection is proposed through calculating unbalance level of EMIs of limb p and q (ULEMI) and average values of EMIs. The novel protection scheme provides an effective method for turn-to-turn fault detection and will not be affected by energization, which is of great significance for practical engineering application.

Adaptive Frequency-Based Reference Compensation Current Control Strategy of Shunt Active Power Filter for Unbalanced Nonlinear Loads

The shunt active power filter (SAPF) is an effective means for the modification of power quality. However, the compensation performance of SAPF would be deteriorated when the unbalanced nonlinear loads are present in the power system. To enhance the compensation performance of SAPF, the adaptive frequency-based reference compensation current control strategy is proposed in this paper. The proposed solution procedure can be divided into three stages including adaptive frequency detection, phase synchronization, and adaptive compensation. With the tracking of power system frequency, the phase synchronization for the SAPF compensation can be effectively modified under the power variation of unbalanced nonlinear loads. Based on the correct synchronization phase angle, the reference compensation current of SAPF can be accurately obtained with the adaptive linear neural network (ALNN) in the stage of adaptive compensation. In addition, the direct current (DC)-link voltage of SAPF can also be effectively regulated to maintain the compensation performance. To verify the effectiveness of the proposed adaptive frequency-based reference compensation current control strategy, the comprehensive case studies implemented with the hardware-in-the-loop (HIL) mechanism are performed to examine the compliance with the specification limits of IEEE Standard 519-2014. The experimental results reveal that the performance of proposed SAPF control strategy is superior to that of the traditional instantaneous reactive power compensation control technique (p-q method) and sliding discrete Fourier transform (DFT).

Coordination of Transformer On-Load Tap Changer and PV Smart Inverters for Voltage Control of Distribution Feeders

The increasing penetration of photovoltaic (PV) generation in distribution systems has entailed dramatic deterioration of distribution system voltage quality due to power injection by PV systems. This paper presents a coordinating control strategy of on-load tap changer (OLTC) of the main transformer in a substation and PV smart inverters to maintain good service voltage quality for the distribution network with high penetration of PV systems. The voltage level at the end-point of each distribution feeder and the power generation by each PV system are collected via a renewable management system. The hourly tap position of OLTC is then derived based on the daily profiles of feeder voltage variation and the injected power generated by all PV systems along the feeder. The PV smart inverters execute an autonomous control of reactive power compensation so that the voltage at the point of common coupling (PCC) can be fixed at the specified voltage level. A main transformer, which serves six feeders with high PV penetration in Taiwan Power Company (Taipower), was selected for this case study. With the proposed coordinating control of OLTC and PV smart inverters, the impact of service voltage quality due to the high penetration of PV systems in the distribution system can be effectively mitigated.

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.

Design and Implementation of Novel Multi-Converter-Based Unified Power Quality Conditioner for Low-Voltage High-Current Distribution System

This paper introduces a novel multi-converter-based unified power quality conditioner (MCB-UPQC). Three optimization methods are proposed based on the traditional UPQC: (1) The shunt converter is substituted with multi-modular parallel converters. Hence, the reactive power and harmonic currents can be increased greatly, which are suitable for low-voltage high-current distribution systems. (2) The series converters consist of three H-bridge inverters, and each of the H-bridge inverters is controlled separately. The control strategy is easier to achieve and can improve the control performance of voltage regulation under unbalanced voltage sag or swell. (3) A three-phase four-leg (3P4L) converter is connected to the common DC bus of the proposed UPQC to connect the renewable energy and energy storage system. The detailed mathematical models of shunt and series converters are analyzed, respectively. A multi-proportional resonant (PR) controller is presented in the voltage regulation and reactive power compensation control algorithms. The simulation results verify the feasibility of the control algorithms. Finally, the experimental platform is established, and the experimental results are presented to verify the validity and superiority of the proposed topology and algorithms.

Active and Reactive Power Compensation Control Strategy for VSC-HVDC Systems under Unbalanced Grid Conditions

This paper presents a power compensation strategy to suppress the double frequency power ripples of Voltage source converter high-voltage direct current (VSC-HVDC) systems under unbalanced grid voltage conditions. The mathematical control equations of the double frequency ripple power of VSC under unbalanced operating conditions are firstly derived and established, where the dynamic behaviors of the double frequency ripples in active and reactive power are regarded as being driven by current-relevant components and voltage-relevant components, respectively. Based on the equations, a power compensation control strategy of VSC-HVDC is proposed via the passivity-based control with disturbance observer to suppress both the current-relevant and voltage-relevant components in the power ripples. With this control strategy, the double frequency ripples in active and reactive power are suppressed simultaneously and system performance is significantly enhanced with the implementation of the disturbance observer in the passivity-based control. Theoretical stability analysis and simulation cases show the effectiveness and superiority of the proposed strategy.

Adjustable VAr compensator with losses reduction in the electric system

Among the existing power quality problems, the reactive power compensation plays a key role once it helps to maintain the system stability and increases the efficiency. Currently, there are many solutions for reactive power compensation, which unfortunately present a wide variety of problems as large inrush currents, non-continuous compensation and harmonics injection in the system. The application of devices like static VAr compensator, static synchronous compensator or unified power flow controller has demonstrated to be an effective solution for reactive power compensation. However, it is important to note that these options are rarely used in distribution systems by companies that prefer to assimilate the drawbacks of switched capacitor banks instead of investing in more expensive, sophisticated and complex solutions. Despite the large number of proposed devices in distribution systems, there is a lack of solutions with emphasis on cost reduction. Therefore, this paper presents a new topology for reactive power compensation and voltage control in distribution systems. The proposed topology has several interesting features as reduced switching losses, small capacitors and simple control scheme. In addition, the proposed solution uses already existing capacitor banks which makes possible its usage in distribution companies with minimum modifications. Experimental results have been obtained on a 6-kVA prototype to demonstrate the feasibility of the proposed solution.

Reactive Power Management in Renewable Rich Power Grids: A Review of Grid-Codes, Renewable Generators, Support Devices, Control Strategies and Optimization Algorithms

Power electronic converter (PEC)-interfaced renewable energy generators (REGs) are increasingly being integrated to the power grid. With the high renewable power penetration levels, one of the key power system parameters, namely reactive power, is affected, provoking steady-state voltage and dynamic/transient stability issues. Therefore, it is imperative to maintain and manage adequate reactive power reserve to ensure a stable and reliable power grid. This paper presents a comprehensive literature review on the reactive power management in renewable rich power grids. Reactive power requirements stipulated in different grid codes for REGs are summarized to assess their adequacy for future network requirements. The PEC-interfaced REGs are discussed with a special emphasis on their reactive power compensation capability and control schemes. Along with REGs, conventional reactive power support devices (e.g., capacitor banks) and PEC-interfaced reactive power support devices (e.g., static synchronous compensators) play an indispensable role in the reactive power management of renewable rich power grids, and thus their reactive power control capabilities and limitations are thoroughly reviewed in this paper. Then, various reactive power control strategies are reviewed with a special emphasis on their advantages/disadvantages. Reactive power coordination between support devices and their optimal capacity are vital for an efficient and stable management of the power grid. Accordingly, the prominent reactive power coordination and optimization algorithms are critically examined and discussed in this paper. Finally, the key issues pertinent to the reactive power management in renewable rich power grids are enlisted with some important technical recommendations for the power industry, policymakers, and academic researchers.

Research on the protection coordination of permanent magnet synchronous generator based wind farms with low voltage ride through capability

To coordinate the protection of PMSG (permanent magnet synchronous generator), collector circuits and outgoing lines, a comprehensive and improved protection method of PMSG based wind farms with LVRT (low voltage ride through) capability is proposed. The proposed method includes adding a short time delay to the collector network current protection zone I and a directional protective relaying to the collector network protection, installing grounding transformers and zero sequence current protection, and generator low-voltage protection action improvement. A LVRT scheme consisting of variable resistance dumping circuit, grid side dynamic reactive power control and reactive power compensation control is proposed. The fault characteristics of PMSG based wind farms are analyzed, and a PMSG based wind farm in Dabancheng, Xinjiang, is used as an example to analyze typical wind farm protection configuration, the setting values considering LVRT requirements, and the coordination problems. Finally, an improved wind farm protection coordination methodology is proposed and its validity is verified by simulation.

Mitigation of Voltage Variation by REMS for Distribution Feeders

This study develops a renewable energy management system (REMS) for the control of photovoltaic (PV) smart inverters to mitigate the voltage violation of distribution systems with high penetration of PV installation. The impact analysis of distribution feeders with the PV system integration for decision making of smart inverter control has been embedded in REMS to solve the voltage violation problem. To verify the effectiveness of the proposed REMS to enhance the system voltage quality, a PV system installed in a distribution feeder of Taiwan Power Company (Taipower) has been selected for field testing. The real power, reactive power, and voltage of the studied PV system have been collected. The impact analysis of PV integration is performed to solve the mitigation of voltage variation by the control of reactive power compensation of smart inverters. It is found that the voltage at the test PV system is very consistent with the field test results. The computer simulation of a distribution feeder with a large PV farm has been executed to illustrate that the control of smart inverters can enhance the utilization of solar energy by reducing the curtailment of renewable power generation dramatically for a distribution system with high penetration of PV systems.

Research on Intelligent Control Technology of Reactive Power Compensation

In the distribution network, reactive power is an important factor influencing voltage stability, and it is related to the safe and stable operation of whole power system. Reactive power compensation is to improve the reactive power, and it is one of the effective measures to ensure the high-efficiency and reliable operation of the power system. In order to improve the power supply capacity of equipment, improve the voltage quality, improve the power factor, reactive power compensation scheme is designed. The realization of reactive power compensation uses the parallel compensation capacitor and takes the ways of low-voltage centralized compensation. To the compensation control strategy, an improved Nine–zone diagram is used. Then choose a reasonable capacity of parallel capacitor according to the calculation of formula. Thus capacitor switching is controlled by software to complete real-time control of the transformer reactive power compensation.

On Coordinated Control of OLTC and Reactive Power Compensation for Voltage Regulation in Distribution Systems With Wind Power

Active management strategies such as coordinated on load tap changer (OLTC) voltage control and reactive power compensation (RPC) are frequently suggested for voltage regulation in a distribution system with a high level of distributed generation (DG). This paper proposes a control and coordination algorithm for these two active management strategies. Voltage control through OLTC is achieved by using state estimation (SE) to determine the voltage in the network. To lower the implementation cost of the proposed control strategy, pseudo-measurements are used together with real-time measurement data in the SE. Moreover, the deadband of the automatic voltage control (AVC) relay is relaxed so that the AVC relay acts on the network’s maximum or minimum voltage obtained through the SE. This is found to be simpler to realize than adjusting the set point of the AVC relay. Voltage control through RPC is actualized by using integral controllers implemented locally at the wind turbine site. Furthermore, RPC from the local wind turbine is also used to mitigate an overvoltage at a remote bus on the same feeder when the remote wind turbine reaches its regulation limit. The applicability of the proposed voltage regulation algorithm is successfully demonstrated using a case study system.

A Shunt Active Power Filter Based on Instantaneous Reactive Power Compensation and Direct Voltage Control for Medium-Voltage Applications

High power and medium voltage (MV) applications need Controlled rectifiers such as 12-pulse converters, because of the high reliability, low complexity, robustness and low power losses. But having the drawback of harmonics generation causes power quality problem. Power quality can be improved with passive filters but having disadvantages such as dependency on the source impedances, parallel and series resonance, aging of passive components. Active power filtering (APF) is used as compensation technique in order to improve thepower quality at the line side. Hence APF becomes a promising compensator solution. This paper presents the APFfor a Medium-Voltage applications using Open Loop Control Compensation.

Reactive power compensation control for three phase grid-connected photovoltaic generator

The high development of renewable energies research field has noticeably led to growing interest to connect such as devices of the electric distribution network. In this work an effectiveness power control strategy adapted on photovoltaic generation system is employed, whereas the performances of the global system are analyzed using MatLab/Simulink environment software. The employed strategy is the decoupling power technique based on the d-q currents components control using the proportional integral controllers. Moreover, a dc/dc boost converter adopted by MPPT control is proposed for the PV generated power enhancement. The main objective of the proposed structure is the improvement of the grid parameters under the power injection of photovoltaic generators. The simulation results confirm the global system ability for dc power control inside the PV generation system, transfer of the generated power to the distribution network and separately control of active and reactive powers. Inside grid, the proposed control enables to compensate the reactive power.

Hierarchical reactive power regulation strategies for high-penetration photovoltaic distribution systems

This paper proposes a hierarchical reactive power regulation system for distribution systems with photovoltaics (PV) connected. The proposed approach includes both central control level and local control level for decisions involving optimal reactive power compensation and dynamic control of reactive power regulation, respectively. Through local control level, based on the PV inverter controllers and central control level compensation command, the overvoltage and voltage variation problems can be highly relieved. In addition to possible reductions in PV generation curtailment, the grid voltage can also be well regulated with minimal line loss via the proposed PV system operation strategies. Accordingly, added value for PV systems is created, conferring win-win solutions for both PV system owners and utilities. Numerical results tested on a practical Taipower company distribution system verified the proposed approach. Copyright © 2015 John Wiley & Sons, Ltd.

Research on Automatic Controlling Method of TSC+TCR Typed Dynamic Reactive Power Compensation

A simulation model of 230kV substation primary system and TSC+TCR typed dynamic reactive power compensation control system was constituted with RTDS, and the feasibility of control system with a case was validated. The control system was to monitor the variation of power system equivalent susceptance with sampling the power system voltage, established the relationships between power system susceptance and the firing angle of TCR, adjusted TSC switch and TCR firing angle to dynamically compensate the reactive power of power system. The simulation results demonstrate that the control system can guarantee power system voltage stability and real-time adjust power factor.

Power System Stabilizers and Control of Reactive Power Compensator in Multi-Machine by Particle Swarm Optimization Algorithm

The purpose of this article is to increase the stability and synchronization of multi-machine power system through power system stabilizers 3 band (pss3b). This new stabilizer system indicates better performance by changes in operating conditions and on the other hand, by setting Flexible AC Transmission System device (FACTS) this system can play a key role in limiting fluctuations. All system variables including pss3b and svc are designed by PSO algorithm in the article. The designed stabilizer has been used in a grid of 11 bus bar with two areas and four machines, and the pss and pss3b performances on increase of low frequency oscillation damping have been compared by applying three-phase fault at different working conditions. Finally the comparison between responses obtained from simulations with the same reference system response can prove advantage of this stabilizer and the newly designed system over previous ones in damping vibrations and stability increase. Keywords: Dynamic System, PSO (Particle Swarm Optimization), PSS (Power System Stabilizer), PSS3B (Power System Stability)

Wind Power Integration to the Transmission Grid: The Egyptian Perspective

The Government of Egypt has recognized that the availability of reliable power supply is essential for economic and social prosperity and human development as well as for attracting private sector investments in the country. Egyptian Economic reform and growth have triggered a rapid increase in electricity demand. Peak load growth rate averaged 7 % p.a. in 2005–2008 and reached as high as 12% in 2008/09. In response to the rapid growth in demand, the supply capacity has expanded through an ambitious power sector investment program that has been under implementation since 2002. The Government's new energy strategy is aiming to increase the share of renewable energy to 20 % by the year 2020. 12% of this value, i.e 7200 MW, is from wind resources. The complexity of the interconnection of wind farms to the power grid stems from the fact that wind energy is rather unstable and available only during certain hours of the day. By its nature the wind power generation may drop suddenly. To keep the grid operation stable, there is a need to ensure that other power generation sources are available to compensate for the drop. Another common characteristic of the wind farms is that they are located somewhat remote from the power grid. Therefore, the utility has to ensure the sufficiency of power transmission capacity. A rather unique feature of wind power in Egypt is that most of the wind resources are concentrated in the Gulf of Suez and Eastern and Western bank of Nile River areas. This raises the additional issue of the impact on the system when large amount of wind power are interconnected at certain points of the network and not distributed over along the country. The effects of having 3000 MW in Gulf of Suez and 4200 MW at Western Nile River areas depend very much on the local wind climate and the typical hour-to-hour load curve (electricity demand). Some important issues needed to be considered are therefore: how should wind farms be expected to behave and perform, and which requirements should be imposed in order to expect wind farms to support the system? Is it realistic to expect wind turbines and wind farms to behave as any other power plant? What is the Impact on thermal loading of lines/transformers? What are the Power Quality Aspects should be mitigated? What is the behaviour during grid faults/Fault ride through? Reactive power compensation and voltage control…..etc. Grid codes are set up to specify the relevant requirements which have to be met in order to integrate wind turbines into the grid. This paper will focus on The Egyptian approach to integrate wind power to the Egyptian Power System and the important issues related to system operation, stability, protection and the associated technical issues. Grid code requirements for large scale integration of wind power will also be illustrated.

Research on TSC Type Reactive Power Compensation Control System for Coal Mine Based on STM32

As the increasing equipment of high power and motor load put into coal mine enterprise, the quality of power supply is decreasing, such as low power factor and large voltage fluctuation, etc. After analyzing the theory and algorithm of reactive power compensation in details, studying a system based on STM32 thyristor switched capacitor (TSC) reactive power compensation control system, which includes compensation, control algorithms of nine zone diagram, controller hardware design and software design. The experimental results show that, this TSC system can realize a faster and more accurate measurement and switching, which have an obvious effect of compensation, and a safe and efficient automatic operation of the system.