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There is the view, widespread in the electrical engineering community, that the effectiveness of energy transfer in electrical systems, thus the power factor, is reduced by energy oscillations which, according to this view, are the cause of the reactive power. This view is challenged in this article. It demonstrates on a variety of circuits that this view is not right. Power factor can decline without energy oscillations, or energy oscillations do not cause its decline. In addition, the reactive power can occur in the absence of energy oscillations or their presence does not cause the reactive power. This observation has not only cognitive but practical merit as well. According to Instantaneous Reactive Power p-q theory, to improve the power factor, energy oscillations between the supply source and the load should be compensated. Because this conclusion is erroneous, an active power filter, controlled according to this recommendation in the presence of the supply voltage distortion or/and asymmetry, instead of improving the power factor can worsen it. The physical meaning of the reactive power is also investigated in this article, with the conclusion that there is no physical phenomenon in electrical systems that could be described in terms of reactive power.

An arc furnace (AF) transformer is extensively subjected to harmonics generated by furnace. To mitigate this, filters are installed usually at AF primary terminals. In this scenario, the harmful current components, namely, the furnace-generated harmonics, the unbalanced, and reactive current, contribute to the transformer energy loss. This loss can be reduced if the filter is installed at the secondary terminals of the AF transformer. This article investigates and validates the furnace performance when the reactive current compensation and harmonic mitigation is implemented on the secondary side of AF transformer. The studies were performed using a real-time simulator OPAL-RT. Results from these studies can significantly enhance our understanding of the impact of filter installed at the furnace terminals.

A method of calculating LC parameters of a reactive balancing compensator for AC arc furnaces at the supply voltage asymmetry is the subject of this paper. The developed method is illustrated numerically with the calculation of LC parameters of a balancing compensator for an AC arc furnace approximated by a linear model with fixed parameters. The presented method can be regarded as an initial step toward developing balancing compensation for ultra-high-power AC arc furnaces. The method of calculation of LC parameters of balancing compensators is based in this paper on the Currents' Physical Component (CPC) power theory.

The paper presents fundamentals of an adaptive balancing of three-phase loads supplied from a four-wire line with a nonsinusoidal voltage, with the use of reactive compensators. Parameters of the compensator are calculated using the Currents' Physical Components (CPC) - based power theory. Thyristor Switched Inductors (TSIs) are used to convert a fixed-parameters compensator into an adaptive one. The adaptive compensator is composed of two sub-compensators, one in the Y structure and the other in the $\Delta$ structure. The method is illustrated in the paper with a computer model.

The views that the energy oscillations between supply sources and loads are responsible for the degradation of the effectiveness of the energy transfer are very common in the power engineering community. A suggestion by the Instantaneous Reactive Power p-q Theory that such oscillations should be removed by a compensator, can result in an erroneous control of switching compensators. The paper shows that energy oscillations do not affect the energy transfer effectiveness, however. The roots of this major misinterpretation are discussed as well. The physical meaning of the reactive power is also investigated in the paper, with the conclusion that there is no physical phenomenon that could be described in terms of the reactive power.

The effectiveness of the energy delivery from its producers to customers is affected by a number of physical phenomena, but the nature of these phenomena is unclear and debated over a century. This debate has resulted in a number of power theories and a great variety of definitions of different power quantities. All of them are mathematically correct but differ as to the interpretation of the physical phenomena which accompany the energy transfer and affect the effectiveness of this transfer. These definitions and physical interpretations affect the method of the power factor improvement and unfortunately, they can cause a compensator malfunction. Presently, the most advanced power theory is based on the Currents' Physical Components (CPC) concept. Results of this theory are used in this paper for a discussion on physical phenomena which affect the effectiveness of the energy transfer in electrical systems.

Powers of three-phase aggregates of single-phase static linear loads supplied with a nonsinusoidal voltage are the subject of this paper. It is demonstrated in this paper that the supply current of such systems with a nonsinusoidal voltage can be decomposed into six mutually orthogonal components associated with distinctive physical phenomena in the load, two of which do not exist at a sinusoidal voltage. Such decomposition enables evaluation of contribution of these phenomena to the supply-current rms value increase and the power factor decline. A power equation and definitions of powers in such systems in the presence of voltage harmonics are proposed. This paper shows that all powers can be expressed in terms of load parameters, which can be identified by a measurement at the load terminals.

A method of the design of an adaptive balancing reactive compensator in four-wire systems with linear loads and nonsinusoidal voltage is described in this article. The method of compensation is founded on the Currents’ Physical Components (CPC) – based power theory of three-phase systems with nonsinusoidal voltages and currents. The compensator is built of two sub-compensators of Y and  structure, respectively. The Y compensator reduces the reactive current and the zero sequence symmetrical component of the unbalanced current. The  compensator reduces the negative sequence symmetrical component of the unbalanced current. The positive sequence symmetrical component of the unbalanced current and the scattered current remain uncompensated. It is because shunt reactive compensators do not have any capability for that. Thyristor Switched Inductors (TSIs) enable the susceptance control of the compensator branches, referred to in the article as Thyristor Controlled Susceptance (TCS) branches. Periodic switching of thyristors in these branches causes the generation of harmonic currents, in particular the third-order harmonic. Moreover, in the presence of the supply voltage harmonics, a resonance of the equivalent capacitance of the compensator with the distribution system inductance can occur. These two harmful phenomena in the compensator suggested were reduced by the selection of a special structure of the TCS branches and their LC parameters. The presented method of the adaptive compensator synthesis was verified in the article with a numerical example and results of computer modeling of the load with an adaptive compensator.

The paper presents some observations and opinions for a discussion on a possibility of balancing ultra-high power ac arc furnace directly at the furnace terminals, i.e., on the secondary side of the furnace transformer. The negative effects of the furnace unbalance reveal themselves, first of all, in the furnace transformer. Therefore, balancing the furnace directly on its terminals could be beneficial for the transformer performance and, first of all, for reduction of the energy loss. Some technical issues have to be solved and several theoretical questions need to be clarified for that. Some of them are discussed in this paper.

Resonant harmonic filters are commonly installed on the primary side of the arc furnace transformer, and conse-quently, the transformer is exposed to the furnace generated current harmonics, the furnace reactive and unbalanced currents. The effectiveness of resonant harmonic filters installed directly at the furnace terminals, i.e., on the secondary side of the furnace transformer, is investigated in this paper. Such filters operate in conditions of fast varying parameters of the furnace. This can cause a decline in the filter effectiveness of harmonics reduction and a decline in the effectiveness of the power factor improvement. This paper investigates the effectiveness of resonant harmonic filters in an uneasy mode of an arc furnace operation. This study should enable us to draw some quantitative conclusions on the usefulness of resonant harmonic filters installed directly on the furnace.

The arcs in ac arc furnaces are stabilized by line inductors, at the cost of the power factor decline. It seems that in common opinions also the arc nonlinearity contributes to this decline. It occurs, however, that at the same parameters, the furnace, regarded as a linear device, has a lower power factor as compared to its value, when the arc nonlinearity is taken into account. The value of ac arc furnaces power factor (PF) is estimated in this paper at the assumption that the dc voltage on the arc has a constant value and a furnace is in a steady state. The PF of ac arc furnaces was evaluated for three states of the furnace operation, namely, for a balanced operation; for a two-arcs operation and for a furnace with a unidirectional arc. The analysis presented in the paper and modeling demonstrate that the arc nonlinearity improves the furnace power factor.

Studies on the power theory and studies on the supply quality and the loading quality refer to the same object, namely, to systems with nonsinusoidal and asymmetrical voltages and current, but from a different perspective and with different objectives. One would expect that the power theory, focused on power properties of electrical systems, will provide theoretical fundamentals for studies on the supply quality and the loading quality. It has occurred, that these studies were not supported substantially by the power theory, however. A major lag in the development of the power theory over the whole XX century was the main cause of it. Even worse than that, a number of misconceptions regarding power properties of electrical systems were disseminated in the electrical engineering community. An overview of such misconceptions that could have a detrimental effect on studies on the supply quality and loading quality in electrical systems is presented in this paper. A draft of the Currents' Physical Components (CPC) - based power theory of electrical systems, which provides interpretation of powers related physical phenomena, is presented as well.

Unbalanced power of three-phase stationary linear loads with a neutral conductor, supplied with sinusoidal symmetrical voltages and its reactive compensation, is the subject of this paper. A novel power equation of such loads is developed. The suggested power equation is based on the decomposition of the load current into Current Physical Components (CPC). This paper shows that all powers can be expressed in terms of the load parameters and this creates fundamentals for design of balancing reactive compensators capable of improving the power factor to unity. A reactive balancing compensator is composed, in general, of two compensators in the $\Delta$ and Y configuration. This paper presents a method of calculation of LC parameters of such a compensator using the CPC-based power theory.

The paper is focused on physical phenomena that degrade the effectiveness of the energy transfer in electrical systems when voltages and currents are nonsinusoidal. The Currents’ Physical Components (CPC) – based Power Theory, developed by L.S. Czarnecki, provides fundamentals for the analysis of the electric energy flow. This analysis identifies in electrical systems seven distinctive physical phenomena that affect this flow. Seven current components are associated with these phenomena. Only one of them contributes to the useful transfer of energy. Remaining six components only degrade the effectiveness of this transfer. They could be reduced by various compensators and the CPC-based power theory provides fundamentals for their synthesis and control. The results presented in the paper are valid for electrical systems of any complexity, meaning for single- and for three-phase systems and for any loads, meaning for linear and for nonlinear loads.

The instantaneous reactive power (IRP) p - q theory can be acknowledged as the first concept that provided fundamentals for switching compensator control and very often such a control is satisfactory. There are situations when this control can result in objectionable effects, however. Instantaneous active and reactive powers, p and q , defined in the IRP p - q theory, were introduced with the emphasis that the definitions of these powers are valid for any three-phase system, without any constraints as to the system properties with respect to the load structure and the supply voltages and load currents waveform. This may imply a conclusion that the instantaneous powers p and q specify the power properties of the three-phase systems regardless of such systems properties. This assurance regarding the lack of constraints has contributed to the dissemination of the IRP p - q theory, especially as a fundamental of the algorithms for switching compensator control. This study shows that such a conclusion has no ground, however. In fact, only at very specific properties of the three-phase system some conclusions on its power properties can be derived from the values of the instantaneous active and reactive powers. Also, it shows that the IRP p - q theory identifies the power properties of the three-phase loads correctly only on the condition that such loads are supplied with symmetrical and sinusoidal voltage.

The paper presents a short draft of history of the development of the power theory of systems with nonsinusoidal voltages and currents. It starts from the Steinmetz experiment run in 1892 and ends with the development of the Currents' Physical Components (CPC) — based power theory. A draft of the CPC and the major contributions to the power theory and methods of compensation are presented as well. The time-domain and frequency-domain as well as the instantaneous and the averaging approaches to the power theory and compensation are compared.

The Conservative Power Theory (CPT) is one of the latest approaches to definitions of powers and compensation in systems with nonsinusoidal voltages and currents. It is shown in this paper that the CPT misinterprets power phenomena in electrical systems, however, and it does not create right fundamentals for the power factor improvement by reactive compensation. In particular, capacitive compensation of the “reactive energy” W, as defined in the CPT, can even degrade the power factor. It is also demonstrated in the paper that the unbalanced current in the CPT is wrongly defined.

The instantaneous reactive power (IRP) p-q theory is one of the major theoretical tools for the development of algorithms for generating reference signals for control of switching compensators, commonly known as active harmonic or power filters. This paper presents results of study on how the supply voltage harmonics affect the reference signal that is generated using the IRP approach. According to this approach, the compensator should also compensate, apart from the IRP, the alternating component of the instantaneous active power of the load. The paper, however, demonstrates that in the presence of the supply voltage harmonics, an ideal, unity-power-factor load has an instantaneous active power with a nonzero alternating component. According to the IRP-based approach, it should be compensated, and this requires that a distorted current be injected into the distribution system. Thus, the conclusion of the IRP p-q theory that the instantaneous active power of ideally compensated loads should be constant is generally not true. The currents' physical components (CPC) power theory is the main theoretical tool for the presented analysis.

Compensation objectives in three-phase asymmetrical systems with non-sinusoidal voltages and currents, from the perspective of the loading and/or supply quality improvement, are discussed and classified. Fundamentals of generation of the reference signal for shunt switching compensator (SSC) control with the Currents' Physical Components (CPC) power theory are also presented. The CPC enables to fit the control algorithms to various objectives of Compensation and to the load properties. This is because the CPC power theory, being founded on power phenomena in electrical systems, provides clear insight into power properties of electrical loads. In spite of the fact that the CPC power theory represents a frequency-domain approach to the identification of the power properties, the CPC-based algorithms are not very computationally demanding and make a quasi-instantaneous control of switching compensators possible.

Unbalanced and/or harmonic generating loads have to be supplied with a working active power, which is higher than the active power measured at the load terminals. Consequently, energy providers of such loads are under paid for the energy delivered. The difference between the working active power and the common active power is referred to as the reflected active power. The reflected active power increases with the decline of the short circuit to load power ratio. Therefore, the reflected active power could be easily visible in weaker power systems, such as micro-grids in islanded mode or on terminals of very high power industrial loads, such as pulsing loads or arc furnaces. The load generated harmonics and/or load imbalance are the causes for the reflected active power. The paper presents results of studies on the dependence of the reflected active power on the relative short circuit power of the supply source.

Main features of the Conservative Power Theory (CPT) are examined in the paper. It was concluded that the “reactive energy” as defined in CPT cannot be regarded as a physical quantity. It was demonstrated that separation of the void reactive current can lead to wrong conclusions at a reactive compensator design. It was shown that distortion power defined in the CPT has no relation to mutual distortion of the load voltage and current. The meaning of the term “conservative” as used in the CPT, is discussed as well. It is emphasized that the conservative property of the “reactive energy” is only mathematical, but not physical property of that “energy”.

The paper presents fundamentals of design of reactive compensators for total compensation of the reactive and unbalanced currents of linear time invariant (LTI) loads supplied with asymmetrical sinusoidal voltage in three-wire systems. Theoretical fundamentals for the presented method are provided by the Currents' Physical Components (CPC) based power theory. Development of the reactive compensator equation is the very core of the method presented. A draft of the CPC-based power theory of LTI loads in three-wire systems with asymmetrical, but sinusoidal supply voltage is also presented in the paper.

Resonant harmonic filters (RHFs) are effective devices for reducing supply current harmonics when only those load generated harmonics for which they are tuned are present. Other current harmonics as well as supply voltage harmonics may reduce the effectiveness of RHFs in harmonic suppression. To counter such reductions in effectiveness, an optimization based method for selection of filter branch parameters is developed for the conventional RHF. It takes into consideration the interaction of the filter with the distribution system and provides filter parameters that give the maximum effectiveness with respect to harmonic suppression. To accomplish this, a cost function is developed, its behavior examined, and appropriate constraint functions are developed. The results for optimized filters, applied in a test case, are given.

This paper investigates how power phenomena and properties of three-phase systems are described and interpreted by the Instantaneous Reactive Power (IRP) p-q Theory. This paper demonstrates that this theory misinterprets power properties of electrical systems or provides some results that at least defy a common sense or meaning of some notions in electrical engineering. For example, it suggests the presence of an instantaneous reactive current in supply lines of purely resistive loads and the presence of an instantaneous active current in supply lines of purely reactive loads. Moreover, it suggests that line currents of linear loads with sinusoidal supply voltage contain a nonsinusoidal component. This paper shows, moreover, that the IRP p-q Theory is not capable to identify power properties of three-phase loads instantaneously. A pair of instantaneous values of p and q powers does not allow us to conclude whether the load is resistive, reactive, balanced, or unbalanced. It is known that a load imbalance reduces power factor. However, the IRP p-q Theory does not identify the load imbalance as the cause of power factor degradation.

The Poynting vector (PV) and Poynting theorem (PT) are fundamental mathematical tools for calculating energy flow, its dissipation, and storage in electromagnetic fields. Therefore, there are opinions that power properties of power systems should be described in terms of the PV and PT. This paper investigates whether or not the PV and PT provide an explanation of power properties and whether or not they enable calculation of powers in three-phase systems. It is demonstrated in this paper that only the instantaneous power and active power can be expressed in terms of the PV but not the reactive, apparent, and unbalanced powers as well as the power factor. Consequently, the PV and PT do not provide information useful for physical interpretations of power properties of power systems. Also, they are useless for practical applications of power theory to power system problems, such as compensation.

Distribution voltage harmonics and load current harmonics other than harmonics to which a resonant harmonic filter (RHF) is tuned, deteriorate the filter efficiency in reducing harmonic distortion. The paper presents results of a study on dependence of this deterioration on the method of the filter design. The study was confined to four-branch RHFs of the 5th, 7th, 11th, and 13th order harmonics, installed on buses that predominantly supply six-pulse ac/dc converters or rectifiers. The filters under investigation were designed according to two different approaches: a traditional approach and an approach based on an optimization procedure. In the traditional approach, the reactive power allocated to particular branches of the filter and their tuning frequencies are selected at the designer's discretion, according to recommended practices. In the optimization based approach, the reactive power allocated to particular branches and tuning frequencies are resultants of an optimization procedure that minimizes the bus voltage and the supply current THD in the system with the filter under design.

The main features of the instantaneous reactive power (IRP) p-q theory, considered as a power theory of three-phase systems, are analyzed in this paper using the theory of the currents' physical components (CPC). This analysis shows that the p and q powers are not associated with separate power phenomena, but with multiple phenomena. Moreover, the results of the IRP p-q theory contradict some common interpretations of power phenomena in three-phase circuits. Namely, according to the IRP p-q Theory the instantaneous reactive current can occur even if a load has zero reactive power, Q. Similarly, the instantaneous active current can occur even if a load has zero active power, P. Moreover, these two currents in circuits with a sinusoidal supply voltage can be nonsinusoidal even if there is no source of current distortion in the load. The analysis shows that a pair of values of instantaneous active and reactive p and q powers does not enable us to draw any conclusion with respect to the power properties of three-phase unbalanced loads even in a sinusoidal situation. Thus, the instantaneous reactive power p-q theory does not identify power properties of such loads instantaneously. This conclusion may have an importance for control algorithms of active power filters. The paper reveals the relationship between the p and q powers and the active, reactive and unbalanced powers, P, Q, and D and specifies the required energy storage capability of active power filters operated under sinusoidal unbalanced conditions.

The effectiveness of resonant harmonic filters (RHFs) in harmonic suppression is the resultant of two different types of resonance that affect the filters' effectiveness in an opposite manner. They are the resonance of the filter branches and the resonance of the entire filter with the distribution system inductance. Damping these resonances by reduction of the filter Q-factor affects the filter performance in a complex way. There are suggestions in the literature on RHFs that such a damping would improve the filter effectiveness. Unfortunately, no quantitative information to support such a suggestion is available. This paper presents the results from a study of the effect of the Q-factor on the filter effectiveness and on the loss of active power in the filter.

The comparison of the instantaneous reactive power (IRP) p–q theory with the theory of the current's physical components (CPC) presented in this paper provides the relationship between powers in both theories applied to three-phase, three-wire circuits with sinusoidal voltages and currents. It shows that results of the instantaneous reactive power p–q theory are inconsistent with power phenomena in such circuits. Namely, the IRP q may occur in circuits with linear, purely resistive loads thus, with zero reactive power, Q, and the instantaneous active power p may occur in circuits with purely reactive loads, thus, with zero active power, P. Consequently, the IRP p–q theory fails to identify the power properties of three-phase circuits with unbalanced loads. Moreover, in spite of sinusoidal supply and the lack of distortion, the IRP p–q theory suggests that the active and reactive currents contain a third-order harmonic. Also the IRP p–q theory is not capable of providing information on power properties of the load instantaneously.

Common opinions respective to the nature of the reactive power, energy flow and oscillations, as well as the notion of the apparent power in single- and in three-phase systems are discussed in this paper. It is shown that some interpretations of powers and energy flow in linear, single-phase circuits are often generalized for more complex situations where these interpretations are not longer valid. Consequently, power phenomena in electrical systems are often misinterpreted. This relates to the reactive power which occurs in three-phase systems without energy oscillation between the supply source and the load, as well as it occurs in time-variant systems without energy storage capability. Also, it was demonstrated in the paper that the arithmetic and geometric apparent powers, commonly used in three-phase systems, do not characterize the supply loading correctly when the load is unbalanced.

The development of power theory of circuits with nonsinusoidal voltages and currents was shaped for several decades by two different approaches introduced, separately, by Budeanu and Fryze in the nineteen thirties. This paper investigates these two power theories from the present perspective and up to date comprehension of power phenomena in circuits with distorted voltages and currents. It shows the reasons for which Budeanu's power theory misinterprets power phenomena and why it does not provide fundamentals for the power factor improvement. This paper shows that a number of concepts introduced to power theory by Fryze are still alive and are very important for developing that theory, but it also has a number of serious limitations. Because of that, some issues, important theoretically, and a number of practical problems in systems with distorted waveforms were not solved within Fryze's power theory. This was the reason for further developing the power theory of systems with nonsinusoidal voltages and currents. This process is not completed yet and a lot can be learned from the history of this theory's development.

With the introduction of renewable energy sources and the technological revolution known as smart grid, a review of the traditional energy accounts based on current standards needs to be addressed. The energy delivered to customers by distorted and asymmetrical voltages and currents has not only a useful component, but it can also have a harmful one. Unfortunately, traditional energy meters are not capable of distinguishing them. These components can be identified using a new concept of working, detrimental, and reflected energy meters. Measurement of these three components of energy delivery to the customers enables identification of the party responsible for waveform distortion and asymmetry in distribution systems and consequently, losses of revenue. This may create economic incentives for both the energy provider and customers aimed at the reduction of harmonics and asymmetry.

Pricing of electric energy is based on the value of the integral of the load active power P measured by energy meters. At such a pricing, the electric power utilities waste some revenue for the energy delivered to current harmonic generating customers and/or customers causing current asymmetry. This is because the load generated current harmonics and unbalanced currents cause an increase in the active power loss in the distribution system. At the same time, the customers that do not generate harmonics but are supplied with distorted and/or asymmetrical voltage are billed not only for the useful energy but also for the energy which may cause only harmful effects on their equipment. It is shown in the paper that these two disadvantages of the tariff in single-phase systems could be eliminated if the energy account based on the value of the integral of the active power of only fundamental harmonic, P/sub I/, rather than on the integral of the whole active power P was used. These disadvantages could be eliminated in three-phase systems if the energy account is based on the integral of the active power of the positive sequence component of the fundamental harmonic.

A method is discussed for on-line measurements of parameters of a power distribution system and its associated load. Four parameters are measured: the complex impedances of the distribution system and the load for harmonic frequencies; the complex rms (crms) values J/sub n/ of the harmonics of the load current j and the crms values E/sub n/ of the harmonics of the distribution system voltage e. The measurements are performed on two states of the system before and after it is disturbed by either connecting to it a capacitor or a harmonic generating device. The results of physical measurements are compared with those calculated from a model.

The paper deals with the power properties of three-phase circuits with unbalanced loads supplied from a three-wire line. It discusses various definitions of the apparent power in such circuits and shows that they cannot be interpreted in terms of any physical phenomena. The paper shows that the unbalanced power does not occur as an effect of the power oscillations and explains why this power does occur. The paper presents a decomposition of the supply current into the active, reactive, and unbalanced currents and shows that this decomposition can be considered as a fundamental for the comprehension of the power phenomena in such circuits and for the power factor evaluation. >

Reactive power compensators with thyristor switched inductors and shunt capacitors enable adaptive compensation at the price of an harmonic distortion increase. This distortion is even higher if the compensator is controlled asymmetrically to reduce the effects of the load unbalance. Harmonic distortion may increase, moreover, because of the compensator resonance with the supply system reactance. This paper suggests a modification of the balancing compensator structure that reduces the harmonic currents injected by the compensator into the supply. The structure suggested also reduces the possibility of the compensator resonance with the supply source inductance. The paper discusses the required control range of the compensator susceptances and their frequency properties and suggests an efficient method of measuring the load parameters needed for VAr compensator control. >

There is a tendency to operate power grids with renewable sources of energy, such as wind generators and/or photovoltaic panels, as islanded micro-grids. Due to low short-circuit power in such grids, harmonic distortion and asymmetry could be higher than in common distribution systems, however. The paper shows that conventional accounts for energy, based on the amount of active energy delivered from a power utility to customers, do not contain any economic incentives for reducing harmonic distortion and asymmetry. Such incentives can be created when instead of the amount of active energy the amount of the working energy delivered to a customer is used as the base for energy accounts.

It might be expected that the meaning of the apparent power S, a quantity of innumerable everyday applications for almost a century, is well understood. It occurs, however, that this meaning is still a matter of discussion and some interpretations hard to accept are published. Also it is suggested in some papers published recently that only oscillations of the instantaneous power may cause an increase of the apparent power S, which is not true. Misinterpretations that refer to fundamental notions such as powers could be particularly harmful for electrical engineering and should be eliminated as much as possible. Therefore, this paper shows that the apparent power does not have the physical meaning suggested recently. Also it shows that load unbalance in three-phase power systems does not cause any oscillation of the instantaneous power. The conclusion that load unbalance causes oscillations of the instantaneous power is a consequence of a substantial misinterpretation of this quantity in three-phase power systems. >

A method of describing the power properties of circuits with nonsinusoidal waveforms of voltage and current is discussed. The method is based on the source current decomposition into orthogonal components dependent on different power phenomena. The active power transmission, current shift, the load conductance variance with frequency, nonlinearity, and time-variance of the load parameters, as well as symmetry of three-phase loads, can be considered as phenomena that contribute to the source current value as separate current components. The author suggests a modification of the decomposition discussed, to a form that may be more appropriate for describing the power flow in circuits with rotating loads. >

There is some level of confusion upon goals of compensation in systems with nonsinusoidal voltages and currents (NV&C), especially considering that compensation with switched compensators is a recursive process. This recursive nature of compensation is often ignored in discussions on compensation. This paper presents results of studies on recursive compensation with a switching compensator, aimed at reducing the supply current to its active component, defined according to Fryze, according to CPC power Theory, and to its working component. The paper also shows that the instantaneous reactive power p–q theory-based algorithm for switching compensator control, does not provide, in the presence of the supply voltage harmonics and/or asymmetry, right control of such compensators.

Properties of the current and power decomposition into the active, scattered and reactive components are discussed. The relative character of this decomposition is analyzed along with orthogonal decomposition of the load voltage. It is shown that this relative character emphasizes the change of the power flow with the cross section observed. The difference in the efficiency of the source apparent power compensation that can be obtained with a shunt and with a series compensator is emphasized. It is also shown that not only the reactive power Q/sub r/, but also the scattered power D/sub s/ can be wholly compensated by a linear reactive compensator, so that the apparent power S of the load can be minimized to its active power P. >

The paper introduces readers to currently the most advanced power theory of electrical systems with non-sinusoidal voltages and currents, along with fundamentals of their compensation, based on the concept of currentspsila physical components (CPC). It includes single-phase systems and unbalanced three-phase systems with linear, time-invariant (LTI) and harmonic generating loads (HGLs).