Instantaneous Reactive Power Theory: A Reference in the Nonlinear Loads Compensation

The instantaneous reactive power theory was published 25 years ago, in an IEEE Transactions. Since then, it has been the most used in nonlinear load compensation with active power filters. Its application allows constant source power to be obtained after compensation in a simple way. Moreover, some researches have showed up some limitations of the theory, i.e., it goes optimally with source voltage balanced and sinusoidal, but not so good with source voltage unbalanced and/or nonsinusoidal, since the source current obtained is not balanced and sinusoidal. This paper presents a new compensation strategy in phase coordinates, equivalent to the original theory's one. Its simplicity, due to the nonnecessity of coordinate mathematical transformation, makes easier the modifications necessary to obtain alternative compensation objectives. In this way, this paper presents those modifications and derives compensation strategies that obtain alternative compensation objectives: unity power factor or balanced and sinusoidal source current. Finally, compensation strategies are applied to a practical power system, and the results are presented

Practical Design of a Load Compensation Active Conditioner

This paper presents the obtained experimental results with a single-phase experimental prototype of a Load Compensation Active Conditioner, sLCAC. The sLCAC is composed by a series – parallel combination of active power filters, and its main objective is the global conditioning of a load against harmonic distortion. On the one hand, to isolate the load voltage vL from the harmonics in the supply voltage vS, as well as to regulate it to the nominal value. On the other hand, to improve the supply current iS, compensating the harmonic and reactive components of the load current iL. An experimental prototype has been implemented, and the obtained results are presented to support the performance of the proposed design

Non-Linear and Unbalanced Three-Phase Load Static Compensation with Asymmetrical and Non Sinusoidal Supply

P-q theory has been widely used to control active power filters since its formulation in 1983. The compensation strategy used by the p-q theory users has not suffered modification; so it is used the constant power compensation strategy. In this way, the supply instantaneous power after compensation is constant. This kind of compensation strategy has obtained good results in the case of balanced and sinusoidal voltages, however it has not been appropriate in the case of unbalanced or non sinusoidal voltages. In this paper it has been researched about the modifications necessary, into the p-q theory frame, to get control strategies which allow to attack the unit power factor compensation or the balanced and sinusoidal currents compensation

Instantaneous Reactive Power Theory in the Geometric Algebra Framework

In this paper, a new approach for instantaneous reactive power analysis in the geometric algebra (GA) environment is presented. The different formulations of the instantaneous reactive power theory (IRPT) proposed, to date, have been developed in three-phase systems. There, an instantaneous power variable, and two/three reactive power variables, all handled independently, were introduced. Thanks to GA, it is possible to carry out a global treatment where an instantaneous power multivector is defined. Thus, in the same multidimensional entity all the power variables are included. From the instantaneous power multivector, the instantaneous power current and the instantaneous reactive current are determined. It should be noted that in this mathematical framework there is no limitation on the number of phases, and the extension of the IRPT to the analysis of multi-phase systems appears in a natural manner. In this study, a systematic approach with the most relevant definitions and theorems corresponding to the proposed methodology has been established. Two practical cases of five-phase and three-phase systems have been included to apply the new established formulation

Apparent power and power factor in unbalanced and distorted systems. Applications in three phase load compensations

The apparent power and the derived power factor are two of the quantities of the biggest use and application inside the Electric Engineering. However, nowadays it continues staying the controversy on their definitions and more appropriate meaning in the most general situations in unbalance and distortion, and unequal resistances in the distribution lines. In the last years they have been distinguished two focuses concerning the functional definitions of apparent power: the European approach, more theoretical and better developed, and the American approach, more practical focus but with smaller rigor. Although from the point of view of their practical application, the use of a definition or another doesn't suppose important numeric differences, if present differ from the conceptual point of view. This is made notice in applications that suppose the use of modern equipments of static compensation. The apparent power of the European approach in its conception only permits parallel compensation, while the apparent power of the American approach admits the seriesparallel compensation. This paper introduces the definitions of apparent power of both approaches and it establishes a discussion on its application in the three-phases loads compensation

Hybrid Active Power Filter: Design Criteria

The configuration of a series active power filter (APF) and a parallel passive filter (PPF) has proven to be an efficient system for nonlinear load compensation. For this topology, different compensation strategies have been proposed to control the series APF. The most effective strategy determines the APF refrerence voltage as a proportion of the source current harmonics. The proportionality constant in the control algorithm implementation is related to the APF gain and the system dynamics. In this paper, the system state model has been obtained for three control strategies of series APF: voltage proportional to source current harmonics, voltage opposite to the load voltage harmonics and a hybrid strategy which combines both previous. The resulting model analyses provide the information needed to establish design criteria for each strategy, both in terms of harmonic filtering and the system stability. The three strategies were compared in two different situations: sinusoidal supply voltages and distorted supply voltages. Finally, results of an experimental prototype developed for this purpose allowed the proposed analysis to be verified

Assessment of Harmonic Distortion Sources in Power Networks with Capacitor Banks

The identification of distortion sources in a power system is a topic unsolved. The problem has a difficult solution because there are elements in the system that do not produce harmonic but amplifies the existing in the electrical network. The most common of those elements is the capacitor, very used to compensate power factor at fundamental frequency. The capacitor behaviour makes that the indices proposed up now to identify distorsion indices fail in the presence of this element. In this paper, a new one is presented: the load characterization index. Besides using an extended equivalent circuit to represent the load, this index calculates the distortion introduced by the load, evaluating, besides the current distortion at its input, the voltage distortion at its terminals. The introduction of voltage assesing makes the index suitable to identify the linear and nonlinear loads in the power system even in the presence of capacitors

Distortion Sources Identification in Electric Power Systems

.Distorted voltage and current waveforms is one of the problems associated to electric power quality. Continuous use of non-linear loads provokes the existence of voltage waveforms with a high distortion. Thus, it is necessary to know the responsible of this problem by means of the commonly named distortion sources identification. In this paper, the problem is analyzed through the harmonic power sign, with the objective of knowing the sense of harmonic power flow between source and one load in distorted systems. Nowadays, it has already been established in the Literature that an analysis of this kind does not solve the problem. Recently, new indices have been introduced to evaluate a specific consumer distortion level. In this paper, a comparative analysis of these indices is carried out, having as reference a practical case. The results obtained show that, in fact, these indices can help to valuate the harmonic distortion, although none of them solve the question definitively

Control strategy for hybrid power filter to compensate unbalanced and non-linear, three-phase loads

A control algorithm is proposed for a three-phase hybrid power filter constituted by a series active filter and a shunt passive filter. The control strategy is based on the dual formulation of the vectorial theory of electrical power, so that the voltage waveform injected by the active filter is able to compensate the reactive power, to eliminate harmonics of the load current and to balance asymmetrical loads. An experimental prototype was developed and experimental results presented