Reactive Power Compensation Units Research Articles

АНАЛІЗ РЕЖИМУ РОБОТИ ЕЛЕКТРИЧНОЇ МЕРЕЖІ З РОЗРОБКОЮ ЗАХОДІВ ПО КОМПЕНСАЦІЇ РЕАКТИВНОЇ ПОТУЖНОСТІ

The article identifies the main measures for energy saving, among which the need to develop and implement methods and devices for reactive power compensation. It was noted that the sign of energy systems of industrial enterprises is irrational management of reactive power flows, the presence of a wide range of harmonic oscillations in the network, violation of temperature modes of individual components of electrical equipment, which leads to reduced equipment life, increased costs. The main reasons for the low value of the power factor in energyintensive industries are the presence and use in technological processes of a large number of induction motors, the power factor of which according to passport data is 0.8 under nominal operating conditions. It is noted that in practice there are often cases when the engines run in modes other than nominal - they are underloaded or overloaded, there are frequent starts of engines under load and their long operation at idle. These modes of operation of induction motors are characterized by an increased level of reactive power. The low value of the power factor leads to increased losses in the conductors, which are directly proportional to the "square" of reactive power, which requires the use of conductors of increased cross-sectional area. The paper proposed design solutions for energy saving in existing technological schemes of power supply: by analyzing the existing situation and calculating the real value of the power factor were calculated and selected reactive power compensation units.

Hardware solutions for connecting static capacitor banks in high voltage electrical networks

This work is dedicated to finding effective hardware solutions for implementing the power part of reactive power compensation units for high voltage electric networks. It shows the possibility of cooperative usage of thyristor and electromechanical key elements for switching static capacitor batteries in high-voltage networks. Based on the suggested hardware solutions main technical and cost characteristics of thyristor capacitor units are determined. The rationality of their use in industrial high-voltage electrical networks of 6-10 kV is concluded. It is shown that the usage of hybrid thyristor capacitor units allows one to reduce the expenses, to provide the required range of accuracy of reactive power regulation, to cut power losses in the network, to guarantee normalized voltage level in the load nodes and to increase the reliability and duration of power equipment life cycle.

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.

Reduction of electric power losses by the reactive power compensation unit at the point of AC electric traction network sectioning

Changes of electric traction network with regulated and not-regulated reactive power compensation units (CU) are required due to switching on the reactive power static generators at the AC electric traction network sectioning points the specifying calculations of the reactive power. The method of calculation of power losses in the traction network with regulated and not-regulated cross capacity compensation units at the sectioning point was developed. The main positive effect of CU at the sectioning point is increasing of the carrying capacity of the railroad sections. However, calculation of CU effectiveness for reduction of electric power losses, as well as calculation of continuously controlled CU requires appropriate calculations. It is demonstrated that CU effectiveness at the sectioning points of reactive power compensation is reduced in connection with distribution of the draft load; CU regulation effectiveness is also reduced as a response to increase of the carrying capacity of the railroad section, which allows assessing the proposed calculation formulae. Presented examples of calculation for the actual baseline data demonstrate that full losses in the traction network (assumed as 100%) can be reduced by using of CU of the sectioning point up to 21% maximum with continuously controlled units and up to 13.4% with uncontrolled CU. As automatics of the reactive power static generator is designed for increasing the carrying capacity of the railroad, its operation frequently complies with the reactive power overcompensation regime when losses in the traction network are increased.

Swarm algorithms in dynamic optimization problem of reactive power compensation units control

Optimization of a power supply system is one of the main directions in power engineering research. The reactive power compensation reduces active power losses in transmission lines. In general, researches devoted to allocation and control of the compensation units consider this issue as a static optimization problem. However, it is dynamic and stochastic optimization problem that requires a real-time solution. To solve the dynamic optimization NP-hard problem, it is advisable to use Swarm Intelligence. This research deals with the problem of the compensation units power control as a dynamic optimization problem, considering the possible stochastic failures of the compensation units. The Particle Swarm Optimization and the Bees Algorithm were applied to solve it to compare the effectiveness of these algorithms in the dynamic optimization of a power supply system.

Extension of the reactive power compensation for the pulsed power supply of ASDEX Upgrade

ASDEX Upgrade (AUG) is an essential element of the European Medium Sized Tokamak (MST) program towards a fusion power plant. It investigates plasma control and performance from plasma core (e.g. current drive and central heating) up to plasma-wall interaction (e.g. plasma confinement and heat exhaust). In order to improve the possibilities and flexibility of the experiment, the heating (ECRH, ICRF and NBI) and power supply systems will be extended and optimized (Käsemann et al., 2017). For plasma ignition and current ramp up of the poloidal field coils high DC voltage is required. During plasma flattop only the ohmic losses of the copper made coils have to be covered. This partial load operation of the high current converters results in high reactive power demand. The power supply of AUG is based on flywheel generators with limited power and energy. To reduce the current load to the generator, a 90 Mvar static reactive power compensation unit has been installed at flywheel generator EZ4 with 2 × 15 Mvar and 2 × 30 Mvar switched compensation modules.

Arrangement of Reactive Power Compensation Units in the Radial Distribution Network of Moscow Oblast

Distribution networks are the direct end-consumer connection part of an electric power system. With the development of technology, advent of new current-using equipment, and increasing population density, these networks are becoming increasingly more and more complex, elements more loaded, and power and voltage losses on the line more significant, which leads to violations of standard requirements. These problems are considered using the example of a section of the Moscow oblast network. The study presented in this article is part of the research project aimed to improve the quality of electric power in the distribution network by analyzing the current state and elaborating corrective steps. The measurements were taken using electric power quality analyzers at maximal and minimal loads. To overcome a high negative voltage deviation, the reactive power compensation unit is proposed. The procedure proposed in this article to solve the given problem consists of two phases. In phase one, loss sensitivity factors (LSFs) are defined and candidate nodes selected for installing the compensation units. This makes it possible to considerably reduce the area of searching for the optimization algorithm and, therefore, cut down the calculation time and improve the algorithm’s convergence. In phase two, the hybrid particle swarm technique is applied to optimally arrange the compensation units among the selected nodes, and choose their capacity. The hybrid optimization technique includes the particle swarm technique (PST) and the quasi-Newtonian algorithm applied after meeting the PST stopping criterion. The quasi-Newtonian algorithm is applied to cut down the time for executing iterations and making the PST more convergent. Numerical modelling is performed in the MATLAB software environment. The measurements in the distribution network of the Moscow oblast served to construct a design model with 111 nodes. According to the measurement results, the voltage level in the consumer coupling nodes considerably overrides the limits defined by GOST (State Standard) 32144–2013. Serious problems with electric power in the mains are connected with inadmissible values of established voltage deviation. The proposed hybrid algorithm of arranging reactive power compensation units makes it possible to reduce the losses of electric power in the mains, reduce the voltage deviation, and increase the line power factor.

Анализ электромагнитных процессов в устройстве компенсации реактивной мощности с переменной индуктивностью

Objective: To analyze transient processes when activating reactive power compensation unit with variable inductance and load bounce in electric traction alternating current network. To determine reactive power control range for possible structural variations of a unit. To choose the most power efficient variant of mutual connection of controlled reactor and capacitor bank with uncontrolled capacity in reactive power compensation unit. To make a conclusion, concerning feedback device application in control system. Methods: Connection diagrams of a unit to an alternating current monophase network. Mutual connection diagrams of controlled reactor and capacitor bank were chosen. Structural variations’ control range analysis of reactive power compensation unit was conducted. In MATLAB Simulink software package, simulation of different bucking out system circuitry was fulfilled. Simulation of compensation unit functioning was carried out for one variant with load bounce in electric traction. Results: It was established that, in case of series connection of controlled reactor and capacitor bank, control range may comprise no more than 15 % of nominal capacity. Starting current of a unit reaches twofold value. Parallel connection makes it possible to control reactive power in a broad band. Starting current in this case reaches fourfold excess of value. It is suggested to use uncontrolled reactor successively with capacitor bank as an additional unit. Such a variant makes it possible to reduce starting current and simultaneously provide filtration of the third current harmonics. Practical importance: A series-parallel variant of compensation unit circuitry seems to be the most perspective for application in electric traction alternating current network.

Design and experimental analysis of an advanced static VAR compensator with computer aided control

This study presents integration of a real-time energy monitoring and control system with an advanced reactive power compensation unit based on fixed capacitor-thyristor controlled reactor (FC-TCR). Firing angles of the thyristors located in the FC-TCR are controlled by a microcontroller in order to keep the power factor within the limits. Electrical parameters of the system are measured by specially designed circuits and simultaneously transferred to the computer via a data acquisition board. Thus, real time data of the system can be observed through a visual user interface. The data obtained is not only analyzed for control process, but also regularly saved into a database. The system has been tested in laboratory conditions under different load characteristics and experimental results verified that the system successfully and accurately achieves compensation process against the all operational conditions.

Experience with voltage control from large offshore windfarms: the Danish case

AbstractThis paper gives an overview of the state of the art and lists future challenges to reactive power and voltage control in the Danish transmission system in relation to large offshore windfarms. Today, the reliable and stable operation of the Danish transmission system is based on the voltage and frequency control carried out at central, conventional power plants. Moreover, the control of some larger decentralized combined heat and power units is activated for voltage control and system balancing, which is specific for the Danish system. In the years to come, according to the government's goal of increasing the share of renewable energy sources in the Danish power system, the share of large offshore windfarms in the Danish power generation mix will increase greatly, replacing central power plants, including their control characteristics during periods of strong winds. Large offshore windfarms must therefore provide the transmission system with the necessary voltage and frequency control, e.g. ancillary services, and ensure secure operation of the power system through their contribution to system service. Danish experience, based on the operation of a system with two large offshore windfarms and several smaller ones, has shown that the efficient use of windfarms' reactive power and voltage control for the on‐land transmission system might be limited by several factors. Among such limiting factors are the reactive power and current capability limits of the electronic power converters and switchable capacitor banks of the offshore wind turbines, which are smaller than those of central power plants measured per unit of the active power rating. Combine this with the use of AC cables, tens of kilometres long, to connect the large offshore windfarms to the on‐land transmission system, the reactive power range available to the transmission system gets poor. The Transmission System Operator should already take such limiting factors and alternative solutions for efficient reactive power and voltage control, such as incorporation of a reactive power compensation unit at the on‐land point of connection or evaluation of a Voltage Sourced Converter‐High Voltage Direct Current instead of an AC connection, into consideration during the planning phase for a windfarm connection. Copyright © 2009 John Wiley & Sons, Ltd.

A Single-Stage Three-Phase Grid-Connected Photovoltaic System With Modified MPPT Method and Reactive Power Compensation

Single-stage grid-connected photovoltaic (PV) systems have advantages such as simple topology, high efficiency, etc. However, since all the control objectives such as the maximum power point tracking (MPPT), synchronization with the utility voltage, and harmonics reduction for output current need to be considered simultaneously, the complexity of the control scheme is much increased. This paper presents the implementation of a single-stage three-phase grid-connected PV system. In addition to realize the aforementioned control objectives, the proposed control can also remarkably improve the stability of the MPPT method with a modified incremental conductance MPPT method. The reactive power compensation for local load is also realized, so as to alleviate grid burden. A DSP is employed to implement the proposed MPPT controller and reactive power compensation unit. Simulation and experimental results show the high stability and high efficiency of this single-stage three-phase grid-connected PV system.