Power Load Flow Research Articles

Techno-economic Analysis of New Wind Power Plant Development in Southern Sulawesi Electrical Power System

Global warming due to carbon emissions has resulted in climate change, which negatively impacts the lives of living things. On the other hand, electricity demand is increasing every year due to the increasing human population, economic growth and equipment electrification. At the moment, most of the electricity generation in Indonesia uses fossil energy power plants which produce carbon emissions. PT. PLN (Persero) is a State-Owned Enterprise tasked with managing the electricity system in Indonesia. PT. PLN (Persero) through the General Plan for Electricity Supply (RUPTL) for 2021-2030 is targeting the construction of New and Renewable Energy Power Plants. One of possible plan is the Wind Power Plant (WPP) construction in the Southern Sulawesi electrical power system. The use of WPP is expected to reduce carbon emissions. However, the integration of WPP causes other problems in the existing system such as dropped voltage, increased equipment loading, increased short circuit current and decreased stability. So, it is necessary to conduct a study on the effects of integrating WPP into the existing system. Using DIgSILENT Power Factory software, Load Flow, Short Circuit and Transient Stability simulations were carried out. Then an economic analysis was carried out including calculating net present value (NPV), internal rate of return (IRR), profitability index (PI), payback period (PBP) and levelized cost of energy (LCOE. The use of WPP at a certain capacity will not disrupt the stability of the system's power because it is still supported by the fast response generators in the system during variable WPP output. Also voltage drop, equipment loading and short circuit current will not exceed the design value of the system. From financial aspect, with certain assumptions, WPP development can be proven to be economically feasible.

Optimal Location and Sizing of Distributed Generators in Power System Network with Power Quality Enhancement Using Fuzzy Logic Controlled D-STATCOM

This article presents the selection of location and sizing of multiple distributed generators (DGs) for boosting performance of the radial distribution system in the case of constant power load flow and constant impedance load flow. The consideration of placing and sizing of DGs is to meet the load demand. This article tries to overcome the limitations of existing techniques for determining the appropriate location and size of DGs. The selection of DG location is decided in terms of real power losses, accuracy, and sensitivity. The size of DG is measured in terms of real and reactive power. Both positioning and sizing of DG are analyzed with the genetic algorithm and the heuristic probability distribution method. The results are compared with other existing methods such as ant-lion optimization algorithm, coyote optimizer, modified sine-cosine algorithm, and particle swarm optimization. Further, the power quality improvement of the network is assessed by positioning D-STATCOM, and its location is decided on the basis of the nearby bus having poor voltage profile and high total harmonic distortion (THD). The switching and controlling of D-STATCOM are assessed with fuzzy logic controller (FLC) for improving the performance parameters such as voltage profile and THD at that particular bus. The proposed analytical approach for the system is tested on the IEEE 33 bus system. It is observed that the performance of the system with the genetic algorithm gives a better solution in comparison to heuristic PDF and other existing methods for determining the optimal location and size of DG. The introduction of D-STATCOM into the system with FLC shows better performance in terms of improved voltage profile and THD in comparison to existing techniques.

인공신경망을 이용한 불안정 전력망에 접속된 발전기 변압기 OLTC 제어

The safe and economic operation of the nuclear power plant (NPP) requires that the plant be connected to a stable and reliable electric grid where the voltage and frequency can be controlled within predefined limits. For a country introducing NPP for the first time, such stable and reliable grid may not exist and the grid may experience voltage and frequency fluctuations beyond the acceptable limits for extended periods. This paper therefore analyzes the necessity of installing an on-load tap changer (OLTC) on the main transformer (MT) of the NPP for automatic and fine voltage control in the event of severe voltage degradation on the Nigeria’s electric grid. IEEE Std. C57.116-2014 power transfer equation and load flow analysis using the electrical transient analyzer program (ETAP®) approach were used for this study. The paper also proposes implementation of artificial neural network (ANN) as a control mechanism for the effective and efficient operation of the MT OLTC tap settings. The research is based on the hypothetical generator output voltage of the proposed advanced power reactor (APR1400) unit connected to the Nigerian electric grid. Implementing the ANN model for MT OLTC automatic control enables stable operation even for the large synchronous generators connected to highly fluctuating voltage grids exceeding the +/-5% voltage range.

Bayesian estimation of copula parameters for wind speed models of dependence

Modelling the uncertainty of wind speed is essential in power flow analysis. Having abundant knowledge of the wind speed in an area is critical. A low volume of data can increase uncertainty in wind speed analysis. Spatial dependencies are often modelled before running probabilistic power flow and load flow analysis. Copulas are a popular way of capturing spatial dependence between multiple wind farms. Using NREL data from seven Northeastern United States wind farm sites, Bayesian inference will be used to determine the copula parameter uncertainty between weekly, daily, and hourly wind speed observations. This approach will be used on elliptical and single parameter Archimedean copulas. For each possible wind farm pair, an uninformative prior will be placed on the copula parameter. The resulting posterior will contain a distribution of copula parameter values based on the prior and the observed wind speed data. The posterior's credible interval is reviewed to determine the uncertainty in parameter estimation. The results show that using a data volume considerably more petite than 8760 hourly data points will result in more uncertainty in parameter estimation and inaccuracies in wind speed forecasting if using non-Bayesian methods for copula parameter estimation.

Optimal Placement of Capacitor Bank on Ondo 132/33KV Transmission Substation

Introduction: Relevancies of electrical power system to consumers cannot be overemphasized. This requires healthy operation of such system. 132/33KV network is an important network within the transmission system and its importance calls for effective and efficient operation. However, due to the long distance at which the transmission line span, the nature of the lay (either overhead or underground) and type of cable used, there are series of voltage instability and power loss along the transmission network which are threat both economically and technically to both electricity providers and consumers because of the cost implication of the losses and effect on the stability of the network.
 Aims: This research aims is to seek optimal placement of a capacitor bank to proffer solution to both voltage instability and power loss problem by simulating Ondo 132/33KV transmission network using NEPLAN software.
 Methodology: The network model was developed using NEPLAN software. The voltage profile and power loss with and without capacitor bank were determined from power load flow solutions using Newton-Raphson method.
 Results: Effects of optimal placements of capacitors along the studied transmission line is established.
 Conclusion: Proper installation of capacitor bank is also found to enhance performance with an accompanied improvement in voltage profile along the buses.

Short-Term and Mid-Term Load Forecasting in Distribution System Using Copula

Short-term and (Mid\Long)-term load prediction are needed for the efficient management of distribution system. An accurate load forecasting could help distribution operators to achieve a great control and flexibility on energy. In addition, a reliable prediction would have significant impact on load power flow problems, operation management, planning, automation, and search market. This paper proposes a new method based on copula for Short-term, and (Mid/Long)-term load forecasting. Proposed method was used less historical data to predict the load consumption then the other methods, so it is useful in distribution system due to scarce installed meters. Copula is a recently developed statistical theory for multivariate probability analysis that has been proposed by Sklar in 1958. Copulas are used in popularity for financial and reliability application. Numerical tests results using database of Iran system’s operation (ISO) shows that this method provides a much better prediction performance in comparison with other methods employing the same data.

Analisis Pemasangan Filter Pasif Untuk Mengurangi Harmonisa Pada Transformator Rectifier Di PT. Indah Kiat Pulp And Paper Perawang

The chlor-alkali process is an electrolysis process which plays an important role in the chemical industry such as the pulp industry. The process produces a product in the form of H2 gas, CL2 gas and NaOH (where the source of chloride ion used is NaCl). This electrolysis process requires a dirrect current with a large current and a low voltage. In this electrolysis process a three phase controlled 12 pulse rectifiers are used which a connected with multi-winding transformers. In the rectifiers process there will be harmonic distortion on the source side of the transformer which can reduce the power quality of the system. To overcome the harmonic problems that occur in the system, an installation analysis of the equipment in the form of a passive single tuned filter is aimed at reducing harmonic distortion of current and voltage and increasing the power factor (cos φ). From the result of harmonic analysis using ETAP software, after the installation of harmonic filters orde 11, 13 and 23, the harmonic current value (THDI) and harmonic voltage (THDV) has decreased, namely, before the filter installation, THDI value is 6,5% whereas after installation of filters, THDI value becomes 0,98%, thus there is a THDI decrease of 5,52%. Furthermore, for the voltage harmonic value (THDV) before filter installation is 1,48% while after filtering, THDV value becomes 0,26%, thus there is a THDV decrease of 1,22%. From the results of the simulation of the flow of power (load flow analysis), after installation of filters there is an increase in the value of the power factor (cos φ). Namely, before the filter installation, the value of power factor (cos φ) is 0,8 while after the filter installation the value of the power factor (cos φ) to 0,96, thus an increase in the power factor (cos φ) of 16%.
 
 Keywords : harmonic filter, single tuned filter, power factor, transformer rectifier

Improved newton-raphson with schur complement methods for load flow analysis

<p>The determination of power and voltage in the power load flow for the purpose of design and operation of the power system is very crucial in the assessment of actual or predicted generation and load conditions. The load flow studies are of the utmost importance and the analysis has been carried out by computer programming to obtain accurate results within a very short period through a simple and convenient way. In this paper, Newton-Raphson method which is the most common, widely-used and reliable algorithm of load flow analysis is further revised and modified to improve the speed and the simplicity of the algorithm. There are 4 Newton-Raphson algorithms carried out, namely Newton-Raphson, Newton-Raphson constant Jacobian, Newton-Raphson Schur Complement and Newton-Raphson Schur Complement constant Jacobian. All the methods are implemented on IEEE 14-, 30-, 57- and 118-bus system for comparative analysis using MATLAB programming. The simulation results are then compared for assessment using measurement parameter of computation time and convergence rate. Newton-Raphson Schur Complement constant Jacobian requires the shortest computational time.</p>

Economic Load Dispatch in Power System by Hybrid Swarm Intelligence

Conserving energy and efficient power systems are very important for us to reduce pollution levels and also reduces wasted fuel resources which are already depleting on the planet. In power operation system, the potential of energy conservation and also much less emission of greenhouse gas because of the wise usage of cleaner non-renewable fuels burned in combined heat and power (CHP) models like the natural gas which provide them benefit from the usual electric power systems. Mixed generator systems have been widely employed by the industry. The industry which requires both power and heat can supply the demands with cogeneration of heat-power systems. Co-generation (CHP) systems could be constructed in cities and used in the form of distributed electricity sources. To get the optimal usage of CHP devices, economic load dispatch (ED) should be requested more for the process of energy conservation. Economic load dispatch plays a vital role and a large number of different approaches and methods have been used in solving such kind of problems. The methods like lambda-iteration and Gradient are used for finding out the optimized solution of non-linear problem. The purpose of this thesis is to utilize the algorithmic optimization approaches like particle swarm optimization (PSO), genetic algorithm (GA) and PSO-GA. In this work, the method of PSO-GA Optimization is used to find out the minimized cost at four of the generating units of heat and power. The base of the work is already published where in the loss coefficients are also presented with max-min cost function and power limit. This work is implemented in the MATLAB simulation environment. The work starts by initializing the load/power and then generators load power flow. The generators are allocated to initialize the cost and this cost is optimized by PSO with GA. At the end the experimental results of GA ,PSO and PSO-GA algorithm is equated with each other and it seems better convergence is achieved by PSO-GA Algorithm.

The effect of different membership functions in power load flow

The effect of different membership functions in power load flow

A Novel Dynamic Index of Voltage Instability Expectation with Power System Contingency

This paper proposes a novel dynamic voltage instability expectation index which takes into account dynamic voltage stability characteristics, the long-term phenomena and probability state of power system contingency. This index is a meter to measure the general robust power system under critical cases which are identified by contingency analysis. The critical contingencies are precisely analyzed by steady-state power load flow in perturbations to figure out violation cases, the weakness of the power system. The probability states of each of violation cases are calculated through availability and unavailability values of devices. The degree of voltage instability is estimated newly by the smallest determinant of dynamic load flow Jacobian matrix in evolution time of power system simulation. The variables of dynamic devices such as under load tap changer of the transformer, excitation limiters of generator unit, affected on a long-term characteristic of the power system, are considered in dynamic load flow Jacobian matrix. Combining the voltage instability rate and the probability state, a novel index, namely voltage instability expectation in dynamic index, is proposed. This index reflects the mutual correlation between the voltage instability rate and probable contingency cases which result in either voltage violation, overload flow, or voltage instability. The new index is demonstrated in IEE 9-bus test system and actual Vietnam power system. It should be a new measure to make a decision of transmission system expansion planning.

A Decentralized Dynamic Load Power Allocation Strategy for Fuel Cell/Supercapacitor-Based APU of Large More Electric Vehicles

In this paper, an enhanced mixed droop control strategy is proposed for a fuel cell/supercapacitor-based auxiliary power unit (FC/SC-APU), which is usually used in large electric vehicles, to achieve the dynamic load power allocation in a decentralized way. By applying an adjustable virtual impedance droop scheme to the SC converter and a virtual resistor droop scheme to the FC converter, the SC is able to buffer the fast-changing or pulsating load power flow, leaving the FC only providing the average load power. Since this method is fully decentralized, it features high flexibility and scalability. Furthermore, the proposed strategy is very suitable for extending the system's service life because the recovery and operational limit of the state-of-charge of SC have been considered in the power allocation. The operational principle of the proposed control strategy and the system design are elaborated, followed by which real-time simulations are conducted to verify theoretical analyses.

Grid Compliance and Power Quality Comparison of Wind Plants with Different Turbine and Grid Types

In this paper, different grid integration and generators used for wind plants is compared by means of quality of the power generated in plant and impact to the power system. Annual energy production and cost of a given wind plant are basis of the comparison. Technical and economical values of different type wind turbine generators are quantitatively evaluated by providing necessary electrical and cost calculations. In technical examination, grid compliance of a 30 MW wind plant with 13 units of asynchronous geared type turbine is investigated by using power system analysis software as per Turkish Grid Code. Steady state conditions of the wind power plant are evaluated by calculating the reactive power capability, load flow and short circuit analysis at first part of the paper. Secondly, low voltage ride through capability, system frequency and voltage test of the wind park are assessed. Similarly, same plant is considered to be equipped with 3.0 MW direct drive type turbines and technical study repeated with different grid type by means of electrical balance of plant. Finally, levelized cost of electricity calculation is done to observe economic effect of plant parameters in order to obtain maximum wind energy.

UPFC based transmission line power load flow control under different operating methods

In this paper the methods to control operation of shunt and series inverters using power flow controller (UPFC) is analyzed with real power flow in power system transmission line. These operation mode using UPFC are executed to reduce Swaying in the control framework transport. The execution about every system may be resolved toward the predefined administrative control. Those arrangement What's more shunt converter working under four separate blending from claiming working modes may be used to ponder An example force framework organize. The line flow in MW oscillation damping is predicated with various modes of operations and verified same with MATLAB/ SIMULINK.

A Modular Multilevel Generic Pulse-Waveform Generator for Pulsed Electric Field Applications

High-voltage (HV) pulses are used in pulsed electric field (PEF) applications to provide an effective electroporation process, a process in which harmful microorganisms are disinfected when subjected to a PEF. Depending on the PEF application, different HV pulse specifications are required such as the pulse-waveform shape, the voltage magnitude, the pulse duration, and the pulse repetition rate. In this paper, a generic pulse-waveform generator (GPG) is proposed, and the GPG topology is based on half-bridge modular multilevel converter (HB-MMC) cells. The GPG topology is formed of four identical arms of series-connected HB-MMC cells forming an H-bridge. Unlike the conventional HB-MMC-based converters in HVdc transmission, the GPG load power flow is not continuous which leads to smaller size cell capacitors utilization; hence, smaller footprint of the GPG is achieved. The GPG topology flexibility allows the controller software to generate a basic multilevel waveform which can be manipulated to generate the commonly used PEF pulse waveforms. Therefore, the proposed topology offers modularity, redundancy, and scalability. The viability of the proposed GPG converter is validated by MATLAB/Simulink simulation and experimentation.

Power control in centralized distributed AC load for wind energy system

In electrical power systems, isolated energy system is a more challenging task to fulfill the active power demand as well as reactive power demand under the fluctuating wind at different load conditions. In this paper, a centralized AC load, centralized distributed hybrid system (CDHS), is analyzed. CDHS has the following features in place of the DC centralized grid system, which is focused on controlling of a permanent magnet synchronous generator, a bi-directional DC-AC converter (BDC) with battery energy storage, and a wind energy conversion system with a single-stage, 3-phase 4-wire AC-AC converter connected to a common AC bus. Non-isolation of the input terminals, multi-stage operation, size and cost of the circuits, and efficient working of the AC-AC converter has been resolved using a 3-phase 4-wire AC-AC converter. A specific triggering pattern of variable frequencies to a constant frequency has been generated for the switching devices in the AC-AC converter to achieve a desired polarity of the output voltage. A BDC connects the isolated load using a natural frame instantaneous current control technique to manage the active and reactive load power flow among the parallel connection AC hybrid systems. Different conditions such as a constant load and a variable load for variable source supplies are demonstrated for the architecture of CDHS in MATLAB/Simulink. The modelling of CDHS and performance analysis have been disseminated out that the proposed CDHS is capable of managing the active power demand with reactive power for voltage variations.

Direct Backward/Forward Sweep Algorithm for Solving Load Power Flows in AC Droop-Regulated Microgrids

We propose an algorithm capable of solving the load power flow problem in ac droop-regulated microgrids. Based on radial distribution networks, these systems lack a slack bus for facilitating the computation by means of conventional methods. Rather than having the stiff bus that provides a voltage reference and supplies the necessary power, the voltage and power regulation must be shared among the distributed resources as a function of their frequency and voltage droop functions. The proposed algorithm is based on the well-known backward/forward sweep algorithm, conventionally employed to solve grid-connected radial load power flows, with the interesting property that they are derivative-free. We have expanded the algorithm to cope with the lack of slack bus. In this paper, we show the theoretical foundation and provide some tests with ex-post computations to investigate the coherence of the results.

Risk‐based optimal distribution of power reserves in wind power plants

AbstractThis paper employs the Conditional Value‐at Risk, largely used in financial risk management, to specify the power reserve capacity of a wind power plant (WPP) under a risk metric. Evidences are shown here that other popular, simpler measure, the Value‐at Risk, is inappropriate for that specification. Under this risk‐based reserve metric, two programs are approached to optimally distribute a reserve request in a WPP subject to a given confidence level in the commitment. The most exhaustive of the two is a two‐level formulation including a solution to the load power flow (LPF) in the WPP. By solving these two programs, for comparison with interior‐point and heuristic solvers, conclusions are drawn. Notably, that a Pareto optimality occurs for stringent reserve requests; that putting off‐line generators is financially more profitable than partial curtailments to respond to low reserve requests; and that in these cases accounting for losses through LPF‐based optimization seems unnecessary. Copyright © 2016 John Wiley & Sons, Ltd.

Power Load Flow by Fuzzy Sets and Different Membership Functions

Abstract. Fuzzy concept is one of the new and efficient tools in many applications. In last decade’s fuzzy logic have vastly applied in control systems, pattern recognition problems, prediction problems, noise cancellation, function approximation and many other problems. The fuzzy logic tools have excellent capabilities in function approximation and solving of nonlinear problems. Therefore, in this study application of fuzzy logic tools have been proposed for power flow solution. There are some methods and algorithms for power flow solution, such as Newton method. But this methods and algorithms are very sensitive to initial solutions of problem. Therefore the algorithm simply traps to local minima. For evaluate the proposed intelligent method, the one real world power system is applied. The mentioned power system has ten generators and thirty nine terminals. The obtained results show that the proposed hybrid system has good performance and capability in solving of power flow problem.

Transient Stability Improvement of IEEE 9 Bus System Using Power World Simulator

The improvement of transient stability of power system was one of the most challenging research areas in power engineer.The main aim of this paper was transient stability analysis and improvement of IEEE 9 bus system. These studies were computed using POWER WORLD SIMULATOR. The IEEE 9 bus system was modelled in power world simulator and load flow studies were performed to determine pre-fault conditions in the system using Newton-Raphson method. The transient stability analysis was carried out using Runga method during three-phase balanced fault. For the improvement transient stability, the general methods adopted were fast acting exciters, FACT devices and addition of parallel transmission line. These techniques play an important role in improving the transient stability, increasing transmission capacity and damping low frequency oscillations.