Fundamental Reactive Power Research Articles

Enhancement of power measurement using a modified method based on wavelet with preprocessing: electric arc furnace case study

In this paper, a new method is proposed for fundamental power calculation based on a wavelet transform with preprocessing by the Hilbert transform. The proposed method increases the frequencies of all harmonics by half of the main frequencies and locates both odd and even harmonics in the centres of the extracted frequency bands. Unlike the conventional method, there is no frequency interference and the fundamental power calculation is enhanced. In order to examine the proposed method, the steel electric arc furnace (EAF) of the Mobarakeh Steel Company, Esfahan, Iran is simulated in MATLAB software at the early stage of charging. Then the fundamental active, reactive and apparent power of the EAF are calculated using simulated and real data. Results confirm the effectiveness of the proposed method.

Application of Backstepping to the Virtual Flux Direct Power Control of Five-Level Three-Phase Shunt Active Power Filter

This paper proposes a virtual flux direct power control-space vector modulation combined with backstepping control for three-phase five-level neutral point clamped shunt active power filter. The main goal of the proposed active filtering system is to eliminate the unwanted harmonics and compensate fundamental reactive power drawn from the nonlinear loads. In this study, the voltage-balancing control of four split dc capacitors of the five-level active filter is achieved using five-level space vector modulation with balancing strategy based on the effective use of the redundant switching states of the inverter voltage vectors. The obtained results showed that, the proposed multilevel shunt active power filter with backstepping control can produce a sinusoidal supply current with low harmonic distortion and in phase with the line voltage. DOI: http://dx.doi.org/10.11591/ijpeds.v4i2.5621

Optimal multi-objective placement and sizing of passive and active power filters by a fuzzy-improved harmony search algorithm

Summary In this paper, the authors present a new method for simultaneous optimal placement and sizing (PLAS) of the passive power filters (PPFs) and active power filters (APFs) with acceptable standard levels. Total harmonic distortion of voltage, total harmonic distortion of current, harmonic transmission line loss and total cost of installed PPFs and APFs are the four objectives considered in the optimization, while individual and total harmonic distortion, fundamental reactive power compensation, parallel and series resonance, detuning of the PPFs and maximum allowable APF size are satisfied with predetermined trust levels. The proposed model is one of the non-convex optimization problems having a non-linear mixed-integer nature. Hence, a new improved harmony search algorithm (IHSA) is used and followed by a fuzzy satisfying method in order to obtain the final optimal solution. The IHSA is a recently developed optimization algorithm which imitates the music improvisation process. In this process, the Harmonists improvise their instrument pitches searching for the perfect state of harmony. The newly developed method has been implemented on the IEEE 18-bus test system by three cases to demonstrate the feasibility and effectiveness of the proposed method. Simulation results illustrate the sufficiency and profitableness of the newly developed method in the PLAS of the multiple passive and APFs, when compared with other methods. Copyright © 2013 John Wiley & Sons, Ltd.

Graphical Representation of the Instantaneous Compensation Power Flow for Single-Phase Active Power Filters

The conventional graphical representation of the instantaneous compensation power flow for single-phase active power filters(APFs) simply represents the active power flow and the reactive power flow which flowing between the power source and the active filter / the load. But, this method does not provide the information about the rectification mode and the compensation mode of APFs, especially, the loss for each mode was not considered at all. This is very important to understand the compensation operation characteristics of APFs. Therefore, this paper proposes the graphical representation of the instantaneous compensation power flow for single-phase APFs considering the instantaneous rectification mode and the instantaneous inversion mode. Three cases are verified in this paper - without compensation, with compensation of the active power 'p' and the fundamental reactive power 'q', and with compensation of only the distorted power 'h'. To ensure the validity of the proposed approach, PSIM simulation is achieved. As a result, we could confirm that the proposed approach was easy to explain the instantaneous compensation power flow considering the instantaneous rectification mode and the instantaneous inversion mode of APFs, also, Total Harmonic Distortion(THD)/Power Factor (P.F) and Fast Fourier Transform(FFT) analysis were compared for each case.

Compact Electric Power System for Fusion Reactor

The issue of the Tokamak fusion reactor is its large area occupied by its power supply, which is about half of the total building area for the International Thermonuclear Experimental Reactor (ITER), together with the compatibility between the site grid and Tokamak loads during the plasma operation period. ITER is now implemented with Tokamak, which requires about 1 GVar reactive power to compensate its power system for superconducting magnets where about 0.2 GVar is transferred from France Electrical Power Network, the other 0.75 GVar is generated by the system of reactive power compensation and harmonic filtering, the standard VSC configuration. ITER can experimentally generate 500-MW fusion thermal power in 400 s long pulse mode. It could only generate about 500 MW/3 = 167 MWe active electric power if it is to be configured with pressured water reactor due to the fact that it is only about 1/3 conversion efficiency from thermal energy to electric energy. For such fusion machine, the requirement for reactive power is much larger than the active power it generates. Based on this requirement, one efficiency and compact pulsed synchronous generator is suggested for this purpose. It can generate not only the fundamental reactive power to compensate and stabilize the power network with low internal impedance but also the active power for outputting power to the network with exciting controller of the generator. Due to its two purposes in one device configuration, it becomes compact and reliable by being implemented in the design of future fusion power plant for demonstration. Some consideration has been done to the special low impedance synchronous generator, which is intended for the concept design of Chinese Fusion Engineering Testing Reactor, targeting the compact electric power system for superconducting Tokamak fusion reactor.

The IEEE Standard 1459, the CPC Power Theory, and Geometric Algebra in Circuits With Nonsinusoidal Sources and Linear Loads

An alternative circuit analysis technique and its associated power theory is compared to the IEEE Standard 1459 and the current's physical components power theory. The comparison shows that elimination of the fundamental reactive power quantity Q1 as defined by the Standard does not ensure supply current reduction. In contrast elimination of the reactive current as defined by the CPC power theory ensures supply current reduction. However, the balance principle of the reactive power cannot be applied to the CPC power theory as the definition of the reactive power is not a signed quantity. The alternative method which uses geometric algebra instead of complex numbers, multivectors in place of phasors and the Euclidian N-dimensional space instead of the frequency domain succeeds in defining a decomposition that accounts for the total nonactive power, and also satisfies conservation. The alternative circuit analysis technique allows viewing the flow of currents and energy/powers in the circuits under examination. Additionally, the paper provides 4 reasons why the present definition of apparent power defined as the product of the magnitude of current and voltage is unsuitable for nonsinusoidal circuits in the GN domain.

Electronic load controller with power quality improvement of isolated induction generator for small hydro power generation

This study deals with an implementation of an instantaneous reactive power theory-based electronic load controller (ELC) for regulating the voltage and frequency of an isolated induction generator system (IG) that can supply electricity in remote areas. This ELC provides the fundamental reactive power and compensates harmonics of load currents. The proposed ELC is a combination of voltage source converter (VSC) with a dc link capacitor, a chopper and an auxiliary load at its dc bus. It controls active and reactive powers of the small hydro plant thus regulating the voltage and frequency of IG system. This ELC also balances the currents of the IG system under unbalanced load currents and eliminates the harmonics of the load currents thereby acting both as a load balancer and a harmonic eliminator. The zigzag/star transformer optimises the dc bus voltage of VSC and acts as a neutral current compensator. The proposed IG along with its ELC is implemented on a 3.7 kW IG system.

A novel discrete multi-objective particle swarm optimisation (MOPSO) technique for optimal hybrid power filter compensator schemes

This paper presents a novel algorithm for a discrete search optimisation and an approach to solve the problem of the hybrid power filter compensator with the design of C-type filter and fixed capacitor bank using discrete multi-objective particle swarm optimisation (MOPSO) method. This novel optimisation approach, a multi-objective particle swarm optimisation (MOPSO) method is implemented to tackle a number of conflicting search goals that define the complex optimal filter design problem. The paper presents the selection with conflicting objective functions and a compromising selection criterion: 1) minimum change in the fundamental frequency load bus voltage under steady state conditions, 2) minimum feeder current for maximum AC system grid capacity release, 3) minimum fundamental frequency utilisation feeder active and reactive power losses, due to reduced fundamental RMS current magnitude, 4) minimum dominant harmonic current penetration into the host electric grid system, 5) maximum harmonic current absorption by the hybrid harmonic power filter with the fixed capacitor bank, 6) minimum harmonic voltage distortion at the point of common coupling or load bus.

New Control Method of Active Power Quality Compensator with Reduced-Capacity Three-Leg Inverter for Electrified Railways

This paper proposes a new control method for reducing the capacity of an active power quality compensator with a three-leg inverter used in electrified railways. In the proposed control method, the fundamental reactive and unbalanced-active components of the load currents are detected. The non-active and unbalanced-active components are compensated on the source side with the fundamental reactive power control. This reactive power control reduces the capacity of the three-leg inverter, which performs the active power quality compensator. The basic principle of the proposed control method is discussed in detail, and then confirmed by digital computer simulation using the PSIM software. A reduced-scale experimental model is constructed and tested. Experimental results demonstrate that the balanced sinusoidal source currents with the power factor of 0.9 are obtained, reducing the capacity of the three-leg inverter by 13% as compared to the already proposed control method.

Flicker Mitigation With a Hybrid Compensator

This paper concentrates on a solution for the voltage flicker problem caused by a resistance spot welding process. Resistance spot welding is characterized by high currents lasting for a few mains voltage periods and followed by idle time lasting several cycles. This causes repetitive voltage changes and creates a phenomenon called flicker. Voltage fluctuations are difficult to compensate since the length of the welding period, the delay time between cycles, and the amplitude of currents may vary substantially. In the literature, active compensators such as active filters have been found effective in compensating changing loads, providing fast compensating responses. However, they should be rated on the basis of the maximum compensating power needed. This paper examines a solution based on a hybrid compensator. The system consists of an active compensator and a fixed detuned filter. The main task of the active part is to compensate changes in the fundamental reactive power, whereas the passive part provides a reduction in the ratings of the active compensator. Since the active part incorporates an active filter, load current harmonics are also compensated as a "by-product." The system stability is analyzed, and the performance is examined in simulations and practical experiments. The resulting flicker severity indices are also assessed. The results show that with the proposed system, voltage fluctuations and flicker levels can be greatly reduced. The dynamics of the combination are found to be fast enough to compensate the rapid variations in the reactive power of the plant. A further benefit is smoothed instantaneous active power drawn from the mains.

Employing stochastic models for prediction of arc furnace reactive power to improve compensator performance

The time-varying nature of electric arc furnace (EAF) gives rise to voltage fluctuations, which produce the effect known as flicker. The ability of a static VAr compensator (SVC), a widely used method for flicker reduction, is limited by delays in reactive power measurements and thyristor ignition. To improve the SVC performance in flicker compensation, a technique for the prediction of EAF reactive power for a half cycle ahead is presented. This technique is based on a new procedure for stochastic modelling of EAF reactive power at an SVC bus. This procedure uses huge field data, collected from eight arc furnaces, to determine the most suitable signal among several candidate signals in view of EAF reactive power prediction. In addition, appropriate orders of autoregressive moving average models are found for reactive power time series. For this purpose, various model adequacy checking methods and some other stochastic analysis methods have been applied on data records. The performance of the compensator in the case of employing predicted fundamental reactive power of an EAF is compared with that of the conventional method by using three new indices that have been defined based on concepts of flicker frequencies and the power spectral density.

A novel harmonic-free power factor corrector based on T-type APF with adaptive linear neural network (ADALINE) control

A novel harmonic-free power factor correction (PFC) topology based on T-type active power filter (APF) is proposed in this paper. The proposed system has better stability characteristics compared to conventional shunt APF topologies and it is a natural filter for the non-linear load harmonic disturbances. The tuned passive filters are connected at the ac-side of the rectifier load, which are designed to provide fundamental reactive power compensation and eliminate majority of load harmonics in order to minimize the power rating and heat dissipation of the voltage source inverter (VSI). The control scheme is based on a decoupled state-space equations of the T-type APF using separate proportional-integral controllers in d-axis and q-axis of rotating reference frame synchronized with grid voltages, respectively. The fundamental components of load-side currents are feed-forwarded in the current control loop using two groups of synchronous frame adaptive linear neural networks (ADALINEs) to ensure a fast dynamic response. A proportional-integral controller is adopted in the outer voltage loop for balancing the active power flow of the dc-side capacitor of the VSI. The proposed power factor corrector topology is studied analytically and by simulation under various scenarios using Matlab/Simulink. The validity and effectiveness of the proposed topology as well as its control schemes are substantially confirmed by the simulation results.

Shunt active power filter implementation for induction heating applications

PurposeThis paper aims to present the prototype of a 140 kVA shunt active power filter (APF) for current harmonics and fundamental reactive power compensation of a 200 kW induction heating system.Design/methodology/approachDesign issues of the power components, of the switching ripple filter and of the digital control are addressed and discussed. The APF control algorithm has been implemented on the 16‐bit, fixed‐point, TMS320LF2407 A DSP controller. The current control is based on proportional‐sinusoidal signal integrators with good performance in current harmonic elimination and power factor compensation.FindingsThe experimental tests, performed in real industrial environment for a 200 kW induction heating plant, show that the performance goals are fulfilled.Practical implicationsThe sinusoidal signal integrators (for consistency with the other plural forms of acronyms) of the current controller are implemented in the rotating reference frame aligned with the voltage vector at the point of common connection. This allows the compensation of two harmonics with a single SSI, thus halving the computational effort of the DSP.Originality/valueIn industrial induction heating, the need for harmonic and reactive power compensation lasts a few seconds per minute, making passive solutions not suitable. The presented APF is a valid solution for this application, where only a few tailored implementations are available on the market.

A new design method of passive tuned filters for harmonic mitigation and reactive power compensation

AbstractThis paper presents a new method for designing passive filters by using a minimization technique. The proposed procedure takes into account the non‐convex behavior of any objective function based on the system current, in case of considering harmonics below the tuned frequencies of the filters. In this sense, it is always assured that the optimal filter is obtained with respect to an optimization criterion. The method is completed with additional restrictions, which consider the position of the resonances introduced by the filters and the injected fundamental reactive power. Applying these restrictions, the designed filters are immunized against the parameter changes. Moreover, the facility including the passive filters does not inject fundamental reactive power to the power system. Finally, an example of application is presented. Copyright © 2005 John Wiley & Sons, Ltd.

Optimal multiobjective planning of large-scale passive harmonic filters using hybrid differential evolution method considering parameter and loading uncertainty

This paper is used to investigate the optimal multiobjective planning of large-scale passive harmonic filters for a multibus system under abundant harmonic current sources using the hybrid differential evolution (HDE) method. The migrant and accelerating operations embedded in HDE are used to overcome traps of local optimal solutions and problems of time consumption. The design purposes are to minimize the total demand distortion of harmonic currents and total harmonic distortion of voltages at each bus. Filters loss, fundamental reactive power compensation, and constraints of individual harmonics are also considered. The search for the global optimal solution is applied to the harmonic problems in a steel plant, where both ac and dc arc furnaces are used and a static var compensator is installed. Three design schemes are compared to demonstrate the performance of HDE. Finally, expectations of objective function are used to present the effects of filter parameter detuning and furnace loading uncertainty.

A reactive power control relay design with a new approach

In this study, the design and implementation of a mixed-signal microcontroller based reactive power control relay that is superior to existing reactive power control relays is presented. This device measures the fundamental reactive power of the system and determines the switching pattern of the capacitor banks which brings the measured fundamental reactive power to the desired value. During measurement, it yields minimal computational load for the fundamental reactive power measurement by employing the Goertzel algorithm instead of the fast Fourier transform (FFT). Consequently, measurement accuracy can be increased without increasing the time required for the FFT-based power measurement by a running average using the last five measured values of the fundamental reactive power. Possible mechanical and electrical failures in capacitor banks are detected by using a simple feedback loop and the user is warned. It has all the other classical features such as P, Q, I, V, and power factor measurement, harmonic analysis, and failure warning signals that a relay should possess.

A full compensating system for general loads, based on a combination of thyristor binary compensator, and a pwm-igbt active power filter

A full compensating system for distribution networks, able to eliminate harmonics, correct unbalanced loads, and generate or absorb reactive power, is presented. The system is based on a combination of a thyristor binary compensator (TBC), and a pulsewidth-modulation insulated gate bipolar transistor active power filter (APF) connected in cascade. The TBC compensates the fundamental reactive power and balances the load connected to the system. The APF eliminates the harmonics and compensates the small amounts of load unbalances or power factor that the TBC cannot eliminate due to its binary condition. The TBC is based on a chain of binary-scaled capacitors and one inductor per phase. This topology allows, with an adequate number of capacitors, a soft variation of reactive power compensation and a negligible generation of harmonics. The capacitors are switched on when the line voltage reaches its peak value, avoiding inrush currents generation. The inductor helps to balance the load, and absorbs reactive power when required. The APF works measuring the source currents, forcing them to be sinusoidal. The two converters (TBC and APF) work independently, making the control of the system simpler and more reliable. Simulations show that the system is able to respond to many kinds of transient perturbations in no more than a couple of cycles. The paper analyzes the circuit proposed, the way it works and shows some experimental results obtained under operation.

A new hybrid active power filter (APF) topology

In this paper, a new hybrid active power filter topology is presented. A higher-voltage, low-switching frequency insulated gate bipolar transistor (IGBT) inverter and a lower-voltage high-switching frequency metal oxide semiconductor field effect transistor (MOSFET) inverter are used in combination to achieve harmonic current compensation. The function of the IGBT inverter is to support utility fundamental voltage and to compensate for the fundamental reactive power. The MOSFET inverter fulfills the function of harmonic current compensation. To further reduce cost and to simplify control, the IGBT and MOSFET inverters share the same DC-link via a split capacitor bank. With this approach harmonics can be cancelled over a wide frequency range. Compared to the conventional APF topology, the proposed approach employs lower dc-link voltage and generates less noise. Simulation and experimental results show that the proposed active power filter topology is capable of compensating for the load harmonics.

A Novel 3-Phase Hybrid Harmonic and Reactive Power Compensator

The application of shunt active filters for the harmonic and reactive power compensation in the high power range is mainly restricted because of their low efficiency and the high cost of inverters with high switching frequency. Moreover; the compensation effect is completely lost in case of internal fault in active filter. Hybrid active filters as the combination of a low power PWM inverter and passive filters have been researched and developed to overcome the limitations of shunt active filter. However, they do not have control over fundamental reactive power. This paper proposes a new hybrid active compensator for harmonic and fundamental reactive current compensation, which consists of two small-rated active filters and one bank of passive filters. Simulation and experimental results are presented to show the advantages of the proposed compensator topology.

Parallel active power filter for single- and three-phase non-linear loads

A parallel active power filter for non-linear loads, its signal processing unit for single-and three-phase application, control principle and power stages are described. The filter current reference determination method, which provides reduction of the fundamental displacement reactive power and non-active distortion power for variable non-linear loads, is based on the combined analogue and digital signal processing. First, the load current is filtered by a precision analogue circuit. Further calculation of the filter current references in a single-and three-phase application is accomplished by microcontrollers. The implemented discrete-time triggering method and selected reactive elements in the filter's power stage provide fast response of the actual filter current to its reference. The results, obtained from experimental circuits, illustrate the active filter performance in steady state and during load current transients.