Reactive Power Sources Research Articles

Implementasi Mikrokontroler Sebagai Pengendali Kapasitor Untuk Perbaikan Faktor Daya Otomatis pada Jaringan Listrik

With increasing electricity rates, the demands of efficiency in electric power consumption is a major consideration. Efficient use of electric power is affected by many factors. Among them is the quality of electric power. Power quality is strongly influenced by the use of certain types of expenses that resulted in the decline of efficiency. In the distribution of electric energy there are several problem sencountered include the voltage drop, low cos Φ, and the loss of power. Load on the network load distribution can be either capacitive or inductive, but in general is an inductive load. If the inductive reactive load the higher the voltage drop will produce a zoom in, zoom power loss, cos Φ lower and lower distribution of power capacity. To reduce the inductive reactive power load required capacitive reactive power sources, one of which is to be installed in parallel capacitors. In this study will be designing and manufacturing tools for controlling capacitor banks according to cos φ m, so that power quality will be better. From the results of this research tool was able to detect the value of voltage, current,and cos φ. The resulting values of the three sensors is quite good. This tool is able tocontrol the capacitor bank in accordance with the value of cos φ meters.

Reactive power control of wind farm made up with doubly fed induction generators in distribution system

In recent years, the number of small size wind farm made up with doubly fed induction generators (DFIG) located within the distribution system is rapidly increasing. DFIG can be utilized as the continuous reactive power source to support system voltage control by taking advantage of their reactive power control capability. In this paper, considering both reactive power control and distribution network reconfiguration can be used to reduce power losses and improve voltage profile, a joint optimization algorithm of combining reactive power control of wind farm and network reconfiguration is proposed to obtain the optimal reactive power output of wind farm and network structure simultaneously. The proposed algorithm has been successfully implemented on the 16 bus distribution network and the results obtained demonstrate the efficiency of the algorithm.

Hybrid Control System for Managing Voltage and Reactive Power in the JEJU Power System

This paper proposes a hybrid voltage controller based on a hierarchical control structure for implementation in the Jeju power system. The hybrid voltage controller utilizes the coordination of various reactive power devices such as generators, switched shunt devices and LTC to regulate the pilot voltage of an area or zone. The reactive power source can be classified into two groups based on action characteristics, namely continuous and discrete. The controller, which regulates the pilot bus voltage, reflects these characteristics in the coordination of the two types of reactive power source. However, the continuous type source like generators is a more important source than the discrete type for an emergency state such as a voltage collapse, thereby requiring a more reactive power reserve of the continuous type to be utilized in the coordination in order to regulate the pilot bus voltage. Results show that the hybrid controller, when compared to conventional methods, has a considerable improvement in performance when adopted to control the pilot bus voltage of the Jeju island system.

Optimal tracking secondary voltage control for the DFIG wind turbines and compensator devices

The optimal tracking secondary voltage control (OTSVC) is a new developed voltage control scheme for wind park based Doubly Fed Induction Generator (DFIG). The proposed controller is developed to achieve efficient voltage regulation and provided optimal reactive power compensation to the interconnected power system. The performance of the controller for enhancing the network voltage profile is compared with secondary voltage control, primary voltage control and optimal voltage profile obtained from the optimal power flow analysis. Furthermore, the OTSVC is employed for controlling wind park based DFIG and other sources of reactive power such as static var compensator ( svc). The dynamic performance of the controller for multiple sources of reactive power is tested for steady state operation and in response of system contingencies with considering the impact of communication time delays. Simulation results are presented and the capability of the controller in providing the desired reactive power compensation and voltage support for the power system are verified.

Variable speed DFIG wind energy system for power generation and harmonic current mitigation

This paper presents a novel approach for simultaneous power generation and harmonic current mitigation using variable speed WECS with DFIG. A new control strategy is proposed to upgrade the DFIG control to achieve simultaneously a green active and reactive power source with active filtering capability. To ensure high filtering performance, we studied an improved harmonic isolator in the time-domain, based on a new high selectivity filter developed in our laboratory. We examined two solutions for harmonic current mitigation: first, by compensating the whole harmonic component of the grid currents or second, by selective isolation of the predominant harmonic currents to ensure active filtering of the 5th and 7th harmonics. Simulation results for a 3 MW WECS with DFIG confirm the effectiveness and the performance of the two proposed approaches.

Reactive power pricing [The Business Scene

Reactive power is one of the least understood ancillary services in the competitive markets. Reactive power is necessary to balance the total demand with the least amount of power flowing in the transmission lines. The line limits and the line losses are a function of the total current, both the real and the imaginary. Minimal power factor correction at the demand increases the reactive source requirements on the transmission system as more distant reactive sources are used. Reactive power is a balance between the capacitance and the inductance of the system components as energy is alternatively stored in electric and magnetic fields. Thus, reactive power is a localized commodity, and the goal of any system is to reduce the size of the local community as much as possible. The goal is to enable real power flows without causing congestion and without increased losses. The selection of reactive power sources can cause congestion and thus can be used as a tool to increase the use of more expensive generation. Reactive power is an integrated market with the real power market as discussed in the following word. This work shows the dependency of real power on reactive power and discusses alternative implementations.

Dynamic optimal reactive power dispatch based on parallel particle swarm optimization algorithm

In this paper, Message Passing Interface (MPI) based parallel computation and particle swarm optimization (PSO) algorithm are combined to form the parallel particle swarm optimization (PPSO) method for solving the dynamic optimal reactive power dispatch (DORPD) problem in power systems. In the proposed algorithm, the DORPD problem is divided into smaller ones, which can be carried out concurrently by multi-processors. This method is evaluated on a group of IEEE power systems test cases with time-varying loads in which the control of the generator terminal voltages, tap position of transformers and reactive power sources are involved to minimize the transmission power loss and the costs of adjusting the control devices. The simulation results demonstrate the accuracy of the PPSO algorithm and its capability of greatly reducing the runtimes of the DORPD programs.

New reactive power sources dispatch applied to the IEEE 57 nodes

PurposeThe purpose of this paper is to deal with a new dispatching and optimization of reactive power sources in power systems.Design/methodology/approachThe methodology is first based on an optimal movement of existing reactive sources as a first phase, then an optimal investment in a second phase and finally a combination of the two previous phases as the third one. The methodology showed also the advantage of a two‐levels procedure, considering an initial minimal compensation before minimizing the active losses. The solution of the global non‐linear problem is performed using the projected and augmented Lagrange method associated with the reduced gradient and the DFP methods.FindingsIn waiting for new investment programs which are planned for limited periods, the study presents an alternative of optimizing the reactive power compensation by a movement of the power sources or some of them, satisfying all system constraints and minimizing also the active power losses.Originality/valueThe planners and operators are able to decide what cases are to be considered for reactive power dispatch; the proposed program gives a proposal solution to almost all changes that can occur to the power system (incident, contingency, load variation, development).

Modelling and control of cascaded multilevel converters for dynamic compensation

PurposeThis paper aims to integrate cascaded multilevel converters in the static compensator (STATCOM) systems in order to assure dynamic compensation of the reactive power absorbed by fixed speed wind turbines.Design/methodology/approachThe cascaded multilevel converter topology is incorporated as a variable source of reactive power required by the wind farm. The evaluation of reference reactive currents is assured by the technique of instantaneous power theory. Thus, the STATCOM, with its appropriate control strategy, continuously compensates the reactive currents.FindingsA developed non‐linear state representation makes possible the analysis of static and dynamic behaviour of the proposed system. The STATCOM‐based cascaded multilevel converter is able to provide continuous compensation and proves highly dynamic under steady state and transient operating conditions.Practical implicationsThe paper formulates a mathematical model which includes all parameters describing the system composed by a medium voltage network, a wind farm and a STATCOM‐based cascaded multilevel converter. The study may help to develop new control methods of such power systems containing non‐linearities and an extended number of parameters.Originality/valueSince there are few studies on comprehensive and complete models of power systems, the paper contributes to make both a study and a simulation based on a developed non‐linear state model which perfectly describes the state and transient behaviour of the proposed system.

An Improved Electronic Load Controller for an Isolated Asynchronous Generator Feeding 3-Phase 4-Wire Loads

This paper deals with a voltage and frequency control of an isolated asynchronous generator feeding 3-phase 4-wire loads in constant power applications where terminal voltage, excitation capacitor, speed and generated power of the generator remain constant under all operating conditions. The proposed controller is functioning as an improved electronic load controller (IELC) to regulate the frequency and as a source of reactive power to regulate the terminal voltage. Three single-phase voltage source converters (VSCs) are connected to each phase of the generator through three single-phase transformers and there is an auxiliary load with a chopper at the self-regulated DC bus of the IELC. These VSCs along with transformers provide their function as a voltage regulator, a harmonic eliminator, a load balancer and a neutral current compensator whereas the chopper and the auxiliary load at the DC bus are used to regulate the frequency. The complete system is modelled and simulated in MATLAB along with Simulink and Power system Block set toolboxes. The simulated results are presented to demonstrate the capability of an isolated generating system driven by uncontrolled pico hydro turbine and feeding 3-phase 4-wire linear/non-linear balanced/unbalanced loads.

A Hybrid Approach Toward Security-constrained Reactive Power Planning in Electricity Markets

In this article, a hybrid approach for reactive power planning has been proposed that makes use of both numerical and analytical methods. Optimal power flow formulations with four different objectives have been solved for a system-intact and for a few severe contingency cases with the help of mixed-integer non-linear programming. For each objective, ranking of optimal bus locations for reactive power sources have been obtained. The results, so obtained, have been used to arrive at an overall performance sensitivity factor for locating reactive power sources employing an analytic hierarchical process algorithm. The proposed method for reactive power planning has been demonstrated on a IEEE 24-bus reliability test system.

Inverse Source Problem in the Spheroidal Geometry: Vector Formulation

A formulation based on Lagrangian optimization and spheroidal vector wave functions is presented for the vector electromagnetic inverse source problem of deducing a time-harmonic current distribution that is confined within a spheroidal volume, that generates a prescribed radiation field, and that is subject to given constraints on the source functional energy, which characterizes antenna current level, and the source's reactive power, which models antenna resonance matching. The paper includes computer simulation results illustrating the derived inverse theory.

Use of Local Information to Determine the Distance to Voltage Collapse

This paper proposes a simple method of determining the distance to voltage collapse using some local information such as bus voltage magnitude and load current magnitude. First the voltage and current information are carefully processed to establish a voltage stability index (VSI) that varies almost linearly with load. The VSI is then used to estimate the distance to voltage collapse using linear extrapolation. The effects of generator reactive power limits, line tripping, non-uniform increase in load and additional shunt reactive power sources on the VSI are also investigated. The effectiveness of the proposed method of determining the distance to voltage collapse is then tested on the IEEE 30-bus system. The results obtained by the proposed method are also compared with the corresponding actual values found through repetitive power flow simulations and are observed to be in very good agreement.

Towards reactive power markets. Part 2: Differentiated market reactive power requirements

Two major contributions are discussed in this part of a two-part set. first, it presents a new concept of market reactive power requirement (qreq) for every participant in both bilateral and pool markets. this qreq is defined as the reactive power loss allocation to each bilateral transaction using current adjustment factor (CAF) method that has been proposed in part 1. when a transaction is allowed to provide reactive power more than its qreq, it contributes to system reactive power needs and it is considered a reactive power provider. on the other hand, if it cannot produce its qreq, it relies on other reactive power sources to ship its contracted power and it is considered a reactive power consumer even though it may generate some reactive power. the concept then is extended to participants in a pool market. secondly, this paper proposes a new general concept of differentiated reactive power requirements for every participant in electricity markets. it assumes that qreq of a participant depends on its allocated losses using any appropriate loss allocation method. the proposals help system operators and market participants to trade reactive power as well as real power effectively and fairly. the simulation results show validity and consistency of the proposals.

Optimal reactive power dispatch in a large power system with AC–DC and FACTS controllers

With the increased loading of existing power system, the problem of voltage stability and voltage collapse has become a major concern in power system planning and operation. The dependence of the system voltage profile on reactive power distribution forms the basis for reactive power optimisation. The technique attempts to utilises fully the reactive power sources in the system to improve the voltage profile and also to meet the reactive power requirements at the AC-DC terminals to facilitate the smooth operation of DC links. The method involves successive solution of steady-state power flows and optimisation of reactive power control variables with unified power flow controllers using linear programming technique. The proposed method has been tested on a real life equivalent 96-bus AC and a two terminal DC system.

Review of Reactive Power Planning: Objectives, Constraints, and Algorithms

The key of reactive power planning (RPP), or Var planning, is the optimal allocation of reactive power sources considering location and size. Traditionally, the locations for placing new Var sources were either simply estimated or directly assumed. Recent research works have presented some rigorous optimization-based methods in RPP. This paper will first review various objectives of RPP. The objectives may consider many cost functions such as variable Var cost, fixed Var cost, real power losses, and fuel cost. Also considered may be the deviation of a given voltage schedule, voltage stability margin, or even a combination of different objectives as a multi-objective model. Secondly, different constraints in RPP are discussed. These different constraints are the key of various optimization models, identified as optimal power flow (OPF) model, security-constrained OPF (SCOPF) model, and SCOPF with voltage-stability consideration. Thirdly, the optimization-based models will be categorized as conventional algorithms, intelligent searches, and fuzzy set applications. The conventional algorithms include linear programming, nonlinear programming, mixed-integer nonlinear programming, etc. The intelligent searches include simulated annealing, evolutionary algorithms, and tabu search. The fuzzy set applications in RPP address the uncertainties in objectives and constraints. Finally, this paper will conclude the discussion with a summary matrix for different objectives, models, and algorithms.

Investigation of the Normal Working Mode of the Nigerian 330-132 kV Network in View of Perspective Load Growth Forecast up to 10 years

In this paper the normal regimes of the Nigerian 330-132 kV power grid at 2003-2005 year levels were analyzed. The load flow studies were also carried out at perspective load growth forecast up to 10 years based on exponential trend using a program (Newton’s method). An analysis of results shows that with existing available generation and maximum load estimate by the utility there is a deficit which will persist if generation, commensurate with load growth, is not immediately reinforced. The network lacks adequate reactive power sources to maintain permissible bus voltages and the power transfer capability due to thermal constraints.

Proportional–Integral Regulator-Based Approach to Wind Farm Reactive Power Management for Secondary Voltage Control

A PI-based control algorithm to govern the net reactive power flowing between wind farms composed of doubly fed induction generators (DFIG) and the grid is proposed in this paper. The motivation underlying consists in demonstrating that secondary voltage control strategies may take advantage of such wind farms as if they were continuous reactive power sources. For that purpose, the local control structure of DFIGs is first described in some detail. The open-loop behavior of a 33 660-kW DFIG wind farm regarding the net power factor is then analyzed via simulation. Based on this study, a net reactive power control algorithm is devised for wind farms made up exclusively of DFIGs. Experimental results obtained by testing it both local and remotely, over a real wind farm located in Navarre-northern Spain-are also provided. In particular, net reactive power set-points supplied remotely to the wind farm are derived by an Optimal Power Flow (OPF) algorithm running at the operation central office of the utility company.

PRICING OF REACTIVE POWER SERVICE

Reactive power service is one of the most important ancillary services in electricity market. In this article the combined reactive power market model is proposed, encompassed with regulated financial compensation of the costs for reactive power sources and value-based reactive power pricing. The methodology of calculation of costs of generators, synchronous condensers and static reactive power sources for economical evaluation of reactive power service was created. In the investigational part the reactive power market model was applied for Lithuanian power system to determine the amount of compensation for reactive power sources.

REACTIVE POWER COMPENSATION ASSESSMENT USING SELF-ORGANIZING FEATURE MAP

In the present work a self-organizing neural network is used for reactive power compensation assessment. The optimal reactive power sources planning are solved using a genetic algorithm. A genetic algorithm is proposed to optimize an objective function which is a linear combination of several factors, such as, overall system active power loss, cost incurred from the installation and use of VAR devices, enhance voltage profile. A self-organizing feature map is trained to compare the power system state once without optimization, then with optimization, first taking account of voltage constraints, and secondly without voltage constraints.