## 1 Introduction
However, in the case of the sinusoidal waveform, an alternative concept of the power analysis is rather suddenly offered, bringing to life such terms as effective values, reactive, apparent and complex power, power factor and power triangle. Although this concept serves well for describing a single frequency sinusoid, formidable obstacles emerge as soon as one attempts to apply a coherent generalization to arbitrary periodic waveforms. The law of instantaneous power conservation in an electric circuit, which is often referred to as [PERSON]'s theorem [10], is the electrical engineering adaptation of a more fundamental energy conservation law. It was explained in [11] that a balancing equation, due to [PERSON]'s theorem, will remain valid after such transformations of the currents and voltages in the entire circuit that do not violate [PERSON]'s laws. The representation of the varying power in the time domain, with an attempt at building a model with a clear physical meaning, is presented in [12]. The direct implementation of balancing instantaneous power is given in [13]. The second of the above mentioned power concepts is based on the theory proposed by [PERSON] [14], and its main points are thoroughly discussed in [15], where it is compared to an alternative power decomposition suggested by [PERSON] [16]. Some additional arguments in favor of the latter were also added in [17]. [PERSON]'s methodology has been dominant for the past century due to its relative simplicity, and has become extremely popular with electrical engineers dealing with sinusoidal waveforms. In particular, those engineers who are working within power delivery systems have developed a specific professional viewpoint on the topic, e.g., [18]. A possible way to generalize [PERSON]'s theory consists in finding a proper definition of reactive power. This definition must preserve the applicability of the concept to the case of an arbitrary periodic waveform. Moreover, such a definition is expected to have some physical meaning and, which is also important, obey some conditions, e.g., the power conservation law. The most prominent approaches being researched recently are based on functional space decomposition used for extracting so called power components. Examples are the vector space decomposition for reactive power presented in [19], the hyperspace decomposition in [20], and the more general geometric algebra approach proposed in [21]. All three show different ways of expressing partial power components. The third one appears to be developed further, into the multivector representation [22]. An attempt at power analysis using a basis different from a harmonic series was made in [23], in which the Haar wavelet was considered as a possible candidate. Among other possible approaches, there is the conservation power theory [24], which is originally based on the decomposition carried out in the time domain [25]. Despite the fact that this theory is gaining popularity, it was criticized in [26; 27] for its lack of a clear physical meaning and misguiding conceptualizations, such as energy taking on a negative value. The further development of [PERSON]'s ideas, which was carried out by [PERSON] [28], has led to [PERSON] physical components theory. The concept considers the current flowing through a one port as a sum of three components: active, reactive and scattered. They are in charge of instantaneous power distribution between three pairwise orthogonal components. Some arguments in favor of this theory were also discussed in [29]. In contrast to other approaches developed so far, this paper offers an alternative method for power analysis based on the theory of cyclostationarity (CS). The history of the focused investigation of CS phenomena spans about 65 years, starting from the pioneering works written by [PERSON] [30] and [PERSON] [31]; the latter called such random processes periodically correlated.