Value Of Reactive Power Research Articles

Optimization of electrical networks modes by transformer ratios

The problem of optimization the modes of electrical networks pro- vides determination the optimal values of reactive power of sources, voltages of reference nodes and transformation ratios of controlled transformers. At pre- sent, methods and algorithms for optimization of reactive power and node volt- ages are sufficiently developed. However, the development of new efficient optimization algorithms of transformation ratios remains as a important topic. In this case, the issues of optimization of transformation ratios of transformers included in closed networks have a particular importance. This paper provides an effective algorithm for optimization the modes of electrical networks on transformation ratios of controlled transformers. The results of research of its efficiency in the presence of transformers with phase-rotary and longitudinal control in the circuit are presented. It is shown that minimization of losses in closed electrical networks when optimizing transformation ratios occurs due to the rational distribution of power flows in the branches.

The basic stages of improving the power grid complex functioning of the Chechen Republic

The article considers the state of the electric power industry functioning of the Chechen Republic. Comparative data on the reception in the network and useful electricity supply of the Chechen Republic in recent years are presented. The total transformer capacity structure of all substations, as well as the power lines total length of Chechenenergo JSC, is considered. The main electric power industry problems of the Chechen power system, which are the lack of own generating capacities, the transformer capacities shortage of substations 110 and 35 kV and the main production assets high level wear of the electric grid economy, are studied. The tasks to reduce the Chechen energy system electric energy losses are considered. The values and causes of the electric energy losses in different district electric networks (RES) of JSC "Chechenenergo" are determined. A comparative analysis of the electrical energy losses in recent years has been performed. Issues related to reactive power in electrical networks are considered. An analysis was carried out to determine the reactive power values in different district electric networks of Chechenenergo JSC. Measures are proposed that contribute to the reactive power normalization and the improvement of technical and economic indicators in electric networks. The networks electrical circuits improvement analysis was carried out to ensure the power supply stability and reliability to consumers in the republic. The production process control system and diagnostics is proposed, which will allow to regulate and coordinate the activities to manage the technical condition, as well as the power system reliability.

Models and methods of optimization of electricity consumption control in industrial enterprises

This article examines the development of models for determining and regulating the value of active and reactive power based on the analysis of the state of normal operation introduced into the system by the enterprise at the highest loads of consumers. In contrast to the methods existing in practice, when the energy characteristics of consumers of electrical energy exceed the standard values, an optimal method for controlling the modes of consumption of electrical energy is proposed. As an example, the energy characteristics of technological electrical installations of the production workshops of the Navoi Machine-Building Plant are given, in order to control the modes of electricity consumption, to maintain the maximum and minimum values of the active and reactive power of consumers of electrical energy.

Analysis of low-frequency oscillations of electrical quantities during a real black-start test in Slovakia

The article discusses the low-frequency oscillations of active power and reactive power recorded during real black-start testing in the power system in Slovakia. The occurrence of these oscillations is analyzed by the theory of calculating RMS values of voltage and current, as well as by measuring the mean value of active and reactive power. The mathematical analysis and theoretical simulations described in this paper confirmed the supposed cause of the measured low-frequency oscillations. These oscillations were caused by inappropriate time window for RMS values as well as active and reactive power evaluation because of two different dominant power frequencies existed. Mutual interconnections between power lines installed on one four-system power line were responsible for the occurrence of these two different dominant frequencies because one line was operated in anisland and three other lines were operated in the interconnected grid with frequency 50 Hz. Understanding the cause of low-frequency oscillations occurrence is necessary for the process of finding technical solutions for its elimination.

Optimized strategy for DFIG wind farm considering turbine fatigue

In wind farms, the fatigue of a wind turbine reduces its life cycle. Additionally, when turbines are subjected to non-uniform fatigue loads, they tend to fail at certain high fatigue loads, which weakens the reliability of the wind farm and increases operating running costs. To operate the wind farm economically, the concept of equivalent fatigue of wind turbines is proposed, based on which an optimal strategy of active and reactive power dispatching of the wind farm is established. This considers the active power output of the wind farm and the fatigue of the wind turbines simultaneously. The swarm intelligence algorithm is used to solve the global optimal problem. Focusing on the profits of the wind farm, the reference values of optimal active and reactive output power of each turbine are calculated. Simulation results under the condition of free output and limited output verify that the proposed strategy can reduce the fatigues of wind turbines and decrease the losses of the wind farm. Thus, the life span of each wind turbine is extended, and the wind farm profits are increased.

Optimal Allocation of Static Var Compensators in Electric Power Systems

In the current age, power systems contain many modern elements, one example being Flexible AC Transmission System (FACTS) devices, which play an important role in enhancing the static and dynamic performance of the systems. However, due to the high costs of FACTS devices, the location, type, and value of the reactive power of these devices must be optimized to maximize their resulting benefits. In this paper, the problem of optimal power flow for the minimization of power losses is considered for a power system with or without a FACTS controller, such as a Static Var Compensator (SVC) device The impact of location and SVC reactive power values on power system losses are considered in power systems with and without the presence of wind power. Furthermore, constant and variable load are considered. The mentioned investigation is realized on both IEEE 9 and IEEE 30 test bus systems. Optimal SVC allocation are performed in program GAMS using CONOPT solver. For constant load data, the obtained results of an optimal SVC allocation and the minimal value of power losses are compared with known solutions from the literature. It is shown that the CONOPT solver is useful for finding the optimal location of SVC devices in a power system with or without the presence of wind energy. The comparison of results obtained using CONOPT solver and four metaheuristic method for minimization of power system losses are also investigated and presented.

Load Flow-Based Method for Nontechnical Electrical Loss Detection and Location in Distribution Systems Using Smart Meters

This work presents an innovative load flow-based approach that uses measurement data from smart meters to detect and locate nontechnical losses (NTL). This approach is focused on identifying loads illegally connected to the distribution system and requires measurements potentially available from smart meters: voltage magnitude, active and reactive powers. For the application of the proposed load flow-based approach, the load buses are modeled as QV buses, i.e., buses in which the reactive power and voltage magnitude values are specified. The buses with noticeable difference between the measured and calculated active powers are indicated as possible NTL locations. The proposed method is tested in unbalanced distribution systems and the results are promising mainly considering its application in secondary distribution systems.

New PQ Controller for Interconnected Microgrids

Distributed Generation Sources are becoming an inseparable part of modern electrical grids. Finding the control strategies which can help them to be as much as possibly beneficial for the grid has been a big concern among the researchers. In this work, a PQ controller for connecting A DC source simulates the effect of a Distributed Generation to the grid based on the decoupling of Active and Reactive powers has been proposed. The Simulation results which have been in the MATLAB/Simulink environment show the effectiveness of this control technique for injecting the defined value of active and reactive power to the grid.

Merenje trofaznih električnih veličina nesinusoidnog oblika pomoću mikroračunarskog merača

In the paper is describing a procedure for measuring the three-phase electrical quantities used in power grids. Measuring the three-phase electrical quantities used in power grids was done with formulas that were implemented in the diagnostic block scheme using the Quartus II 13.0sp1 software package. A discrete (digital) algorithm was developed to obtain the effective values of voltage, current, active and reactive power. The results obtained are programmatically simulated, presented on the monitor or printed, and are applicable in practice.

Solution of the problem of optimum power distribution of individual compensating devices for a group of asynchronous motors for a stable operating mode and for a smoothly changing load

Residential and industrial buildings with large territorial dimensions, have mainly radial power supply schemes, which feed a large number of small and medium capacity 0.4 kV induction motors. For their power supply copper or aluminum cables of small cross-section (with high active resistance) are used. Calculations of electricity losses in such lines show significant values. In order to reduce active power losses in 0.4 kV cable lines, the optimization problem of minimizing active power losses in the radial power supply circuit is solved by optimal distribution of reactive power of a given value between compensating devices. The single-line scheme of power supply of a group of pumps of technological installation of petrochemical production is considered, the mathematical model of the optimization problem on criterion of minimum of active losses in power lines from reactive power flow is made, which limitations are presented as a system of linear algebraic equations. Results of distribution of optimum values of reactive power between compensating devices of asynchronous motors at maintenance of the set tg φ are received. The quantitative estimation of active power loss reduction in power lines at use of capacitor units, which reactive power is optimally distributed, is given.

Direct Power-Based Three-Phase Matrix Rectifier Control with Input Power Factor Adjustment

In a current source rectifier such as a matrix rectifier, input voltage and current cannot be in phase unless an additional input power factor control technique is implemented. This paper proposes such a technique for a matrix rectifier using power-based space vector modulation (SVM). In the proposed method, the modulation index and phase required in order to apply the SVM are calculated based on the active and reactive power of the rectifier for intuitive power factor control. The active power that the rectifier should generate for the regulation of the output inductor current is obtained by the PI (proportional-integral) controller. The reactive power, which is supplied by the rectifier for adjustment of the power factor, is assigned differently depending on the output condition: for the output condition capable of unity power factor, it is set to a negative value of reactive power of the input capacitor, and when the unity power factor is not achievable, it is set with the maximum reactive power the rectifier can generate under the given condition to attain the maximum possible input power factor. It is determined whether the given condition is the light load condition by comparing the absolute value of the reactive power supplied by the input capacitor with the maximum rectifier reactive power that can be produced under the given condition. The SVM based on the active and reactive power of the rectifier in this technique allows the input power factor control to be intuitive and simple. The performance and feasibility of the technique were proved by simulation and experimentation.

Reactive Power Management System for Wind Power Plant

This paper deals with the study of reactive power management system for wind power plant. In the wind power plant, there is a need of reactive power for the process of developing rotating magnetic field in the induction generator. If the value of reactive power provided to the wind power plant is not sufficient than there occurs a voltage collapse in the electric power system and the occurrence of voltage collapse results in blackout. Therefore, this paper focus on the management of reactive power needs by the wind power plant in such a way that it could fulfil the requirement of power plant in a most efficient way without undergoing into voltage collapse.

Minimization of active capacity losses in cable power lines of 0.4 kV using optimally distributed compensating devices at petrochemical and oil refining enterprises

We propose a solution for optimization problem of minimizing active power losses for radial power supply scheme by optimal distribution of a given amount of reactive power between the compensating devices. We considered a single-line power supply scheme for a group of pumps of technological installation at a chemical plant. A mathematical model of the optimization problem is compiled by the criterion of active losses minimum in power lines depending on the reactive power flow. We obtained the distribution of optimal values of reactive power between the compensating devices of asynchronous motors for the specified tg φ. Quantitative and cost estimations are given for reducing the active power losses in power transmission lines when using capacitor plants, the reactive power of which is optimally distributed. We investigated the influence of starting currents on a circuit when asynchronous motor and capacitor installation are simultaneously turned on. We established the absence of an additional dynamic load on the supply lines.

Fractional Order Sliding Mode Control of PMSG-Wind Turbine Exploiting Clean Energy Resource

The extensive application of permanent magnet synchronous generator (PMSG) based wind energy conversion system (WECS) has attracted growing interests of power researchers on its control and operation. This paper aims to propose a kind of fractional order sliding mode based (FOSM) power output control scheme of PMSG based WECS with fast exponential reaching law (FERL). The FERL based FOSM control technique proves to be better capable of attenuating the level of the chattering phenomenon with faster convergence speed. The boost converter and the neutral point clamped inverter, both of which are utilized to connect the PMSG and the power grid, are controlled with the proposed FOSM control scheme. Furthermore, the direct and quadrature grid current are tracked, which leads to the control of the active and reactive power output. The effectiveness of the proposed method is verified with an 8kW wind turbine simulation and the test results indicate that the proposed method can better track the reference value of active and reactive power. In addition to that, the total harmonic distortion level of the grid current is largely mitigated.©2019.CBIORE-IJRED. All rights reservedArticle History: Received June 2nd 2018; Received in revised form October 6th 2018; Accepted January 7th 2019; Available onlineHow to Cite This Article: Khan, M.W., Wang, J., Xiong, L. and Ma, M. (2019). Fractional Order Sliding Mode Control of PMSG-Wind Turbine Exploiting Clean Energy Resource. International Journal of Renewable Energy Development, 8(1), 81-89.https://doi.org/10.14710/ijred.8.1.81-89

Using smart meters for checking the topology and power flow calculation of a secondary distribution network

The paper analyzes options of using smart meters for power flow calculation and for assessing the state of a real three-phase four-wire secondary distribution network based on measurements of average values of active and reactive power and of voltages. The work is based on the authors’ research on allocation of measurements to ensure secondary distribution network observability and on selection of the most efficient method for linear and non-linear state estimation. The paper illustrates solution of a problem on identification composition of load nodes in the phases and reveals challenges related to voltage account in the neutral wire and in its grounding.

An Amorphous Alloy Magnetic-Bus-Based SiC NPC Converter With Inherent Voltage Balancing for Grid-Connected Renewable Energy Systems

This paper presents an amorphous alloy magnetic-bus-based neutral point clamped (NPC) converter for grid-connected renewable generation systems. In the proposed system, the amorphous alloy high-frequency high-power density multi-winding magnetic bus generates balanced dc supplies for the five-level (5L) NPC converter for high-quality power conversion. Compared to the traditional NPC converter topologies, the proposed magnetic-bus-based architecture does not require any control circuit for voltage balancing of the series connected capacitors. The magnetic bus inherently overcomes galvanic isolation issues and may reduce the size of the boosting inductor. In this paper, a finite control set model predictive control algorithm is derived to control the grid-connected 5L-NPC inverter for multilevel voltage synthesizing, while achieving the user-defined active and reactive power values. To verify the proposed concept, a simulation model is developed and analyzed in MATLAB/Simulink environment. To validate the technology, a scale d-down prototype test platform is developed in the laboratory with silicon carbide switching devices, which achieves high blocking voltage, low power dissipation, high switching frequency, and high-temperature operation. Based on the simulation and the experimental results, it is expected that the proposed converter will have a great potential for widespread application in renewable generation systems including superconducting generator-based wind turbines.

Real-Time Implementation of High Performance Control Scheme for Grid-Tied PV System for Power Quality Enhancement Based on MPPC-SVM Optimized by PSO Algorithm

This paper proposes a high performance control scheme for a double function grid-tied double-stage PV system. It is based on model predictive power control with space vector modulation. This strategy uses a discrete model of the system based on the time domain to generate the average voltage vector at each sampling period, with the aim of canceling the errors between the estimated active and reactive power values and their references. Also, it imposes a sinusoidal waveform of the current at the grid side, which allows active power filtering without a harmonic currents identification phase. The latter attempts to reduce the size and cost of the system as well as providing better performance. In addition, it can be implemented in a low-cost control platform due to its simplicity. A double-stage PV system is selected due to its flexibility in control, unlike single-stage strategies. Sliding mode control-based particle swarm optimization (PSO) is used to track the maximum power of the PV system. It offers high accuracy and good robustness. Concerning DC bus voltage of the inverter, the anti-windup PI controller is tuned offline using the particle swarm optimization algorithm to deliver optimal performance in DC bus voltage regulation. The overall system has been designed and validated in an experimental prototype; the obtained results in different phases demonstrate the higher performance and the better efficiency of the proposed system in terms of power quality enhancement and PV power injection.

Scheduling of PV inverter reactive power set-point and battery charge/discharge profile for voltage regulation in low voltage networks

In recent years, renewable energies and storage systems are bringing a significant contribution to power system. Due to the high penetration of non-predictable power sources, especially in the distribution networks, new challenges related to the integration and management of these new resources also combined with storage systems arose in power system research. Accordingly, the aim of this paper is to propose an innovative scheduling method for voltage regulation in low voltage networks. A simple type of contract for ancillary services that foresees the participation of active users endowed with a storage system coupled with a PV system is considered. The method allows to regulate the voltage in a distribution system by using a combined PV and storage system. The voltage regulation is achieved by setting the value of the inverter reactive power on the basis of sensitivity coefficients of the considered node, taking into account the capability curve constrains, as required by new grid codes. A possible tariff policy is also proposed for the ancillary service and for the operation of the realization of the scheduling algorithm. Simulation results demonstrate the effectiveness of the proposed method for the scheduling of the power system.

Design and Experimental Investigation of Predictive Direct Power Control of Three-Phase Shunt Active Filter with Space Vector Modulation using Anti-windup PI Controller Optimized by PSO

This paper presents a robust control scheme for shunt active power filter based on predictive direct power control with space vector modulation. The proposed control strategy solves the problem of variable switching frequency of predictive control strategy, and it offers simple and robust hardware implementation. It uses a discrete model of the system based on time domain to generate the average voltage vector, at each sampling period, with the aim of canceling the errors between the estimated active and reactive power values and their references. Concerning the DC-side voltage of the inverter, anti-windup PI controller is tuned offline using particle swarm optimization algorithm to deliver an optimal performance in DC bus voltage regulation. The overall system has been designed, simulated and validated experimentally; the obtained results in different phases demonstrate the higher performance and the better efficiency of the proposed system in terms of power quality enhancement.

MODELLING AND ANALYSIS FUEL CELL WITH BATTERY STORAGE MICROGRID SYSTEM BASED ON GREEN ENERGY

Objectives: This study is aimed at analyzing the characteristics of an 11 kV microgrid system when connected to a combination source of fuel cell and battery storage. Methods/Statistical Analysis: To do so, Matlab Simulink software was used as simulation platform. Three types of connection were simulated which are first; fuel cell to grid, second; battery storage to grid and lastly; combination of fuel cell and battery storage to grid1 . Findings: For each connection type, parameters such voltage, current, active power and reactive power are recorded when the grid is either in connected or disconnected mode. Simulation results have shown positive values of active power and reactive power which flows from the source to the grid side in both modes. Application/Improvements: This implies that the combination of fuel cell and battery storage is a reliable source for a particular constructed microgrid system to be successful. If implemented in real application, the suggested microgrid system will be a dependable alternative to supply electricity to rural areas which are too remote and unfeasible to be connected to a conventional grid system. Keywords: Battery Storage, Fuel Cell, Microgrid, Matlab Simulink, Renewable Energy