无功功率补偿中英文资料外文翻译文献本科论文.doc
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1、无功功率补偿毕业论文中英文资料外文翻译文献HARMONIC DISTORTION AND REACTIVE POWER COMPENSATION IN SINGLE PHASE POWER SYSTEMS USING ORTHOGONAL TRANSFORMATION TECHNIQUE W. Hosny(1)and B. Dobrucky(2) (1) University of East London, England (2) University of Zilina, Slovak Republic ABSTRACT This paper reports a novel strategy
2、 for analysing a single phase power system feeding a non-linear load. This strategy is based on a new theory to transform the traditional single phase power system into an equivalent two-axis orthogonal system. This system is based on complementing the single phase system with a fictitious second ph
3、ase so that both of the two phases generate an orthogonal power system. This would yield a power system which is analogous to the three phase power system but with the phase shift between successive phases equal to /2 instead of 2/3. Application of this novel approach makes it possible to use the co
4、mplex or Gauss domain analytical method in a similar way to the well known method of instantaneous reactive power for three phase power system instigated by Akagi et al in 1983. Thus, for the fictitious two-axis phase power system, the concept of instantaneous active and reactive power could be inst
5、igated. Moreover, the concept of instantaneous power factor could be defined. The novel strategy of power system analysis outlined in this paper is applied to a single phase power system feeding a non-linear load in conjunction with an active power filter. The latter serves the purpose of compensati
6、ng for either of the instantaneous reactive power or the harmonic current distortion in the single phase power system under investigation or for compensating of both. Experimental results demonstrated the effectiveness of the novel single phase power system analysis reported in this paper. Keywords:
7、 single phase power systems, orthogonal transformation technique, harmonic distortion and reactive power compensation 1 INTRODUCTION In this section the orthogonal transformation technique applied to a single phase power system instigated by Akagi et al, reference 1, is described. By adopting this t
8、echnique expressions for the reference currents used in an active power filter for the compensation of harmonic distortion or reactive power or both, are derived. Consider a single phase power system which is defined by its input voltage and input current as follows: vRe(t) = V Cos t (1) iRe(t) = I
9、Cos (t ) Where V and I respectively are the peak values of the voltage and current, is the angular frequency of the power supply and is the phase shift between voltage and current. The power system described by Eq.(1) is termed as the real part in a complex power system and iscomplemented by a ficti
10、tious/imaginary phase defined as follows: Vim(t) = V Sin t (2) Iim(t) = I Sin ( t ) Comparing Eqs (1) and (2), it is obvious that the imaginary or fictitious phase of the voltage or current in a single phase power supply can be created in the time domain by shifting the real component on the time ax
11、is to the right by an equivalent phase shift of /2. According to Eqs(1) and (2), the - orthogonal co-ordinate systems for both of the voltage and current are defined as follows: v = vRe(t) and v = vim(t) (3) i = iRe(t) and i = iim(t) According to reference 1, each of the and components of the voltag
12、e and current are combined to form a vector, x(t). This vector can be represented by the following equation: This vector is represented in the Gaussian complex domain as a four sided symmetrical trajectory, Fig.1. Because of the symmetry of the x(t) trajectory shown in Fig.1, it is evident that the
13、voltage and current investigation for the complex power system (including both of real and imaginary voltage and current components), could be carried out within quarter of the periodic time of the voltage and current waveforms (T/4). Thus, Fourier transforms applied for the harmonic analysis of non
14、-sinusoidal waveforms could be carried out during this time interval only as it will be shown later. Fig.2 shows the arrangement of the real and fictitious/imaginary circuits of the complex single phase power system under investigation. As it is shown on this Figure, the real and fictitious circuits
15、 should be synchronised by the so called “SYNC” signal. This implies that the x(0) is a priori zero.2 p-q-r INSTANTANEOUS REACTIVE POWER In this section the use of the p-q-r instantaneous reactive power method, described in references 2, 3 and 5, for compensating of the reactive power and harmonic f
16、iltering is explained. Consider a single phase power system with a cosinusoidal voltage supplying a solid state controlled rectifier, thus yielding a non-sinusoidal supply current waveform. The supply current is assumed to have a square waveform. Thus, the supply voltage and the fundamental componen
17、t of the supply current could be written as: vRe(t) = V Cos t (5) i1Re(t) = I1 Cos (t /3) The supply voltage and current waveforms as well as the fundamental current waveform are depicted in Fig.3. The voltage and fundamental current components are given as: vim(t) = V Sin t (6) iim(t) = I1 Sin (t /
18、3) The instantaneous active and reactive power equations for the complex power system under consideration are given in the - domain, as described in references 1, 3 and 5, as follows: Fig.5 depicts the time variation of p and q for the complex single phase power system under consideration. In this f
19、igure PAV and QAV respectively are the average values of the active and reactive power. The instantaneous power factor, , is defined as: It is important to point out that the values of p, q and in Eqs (7) and (8) are instantaneous values. The p-q-r theory is introduced in reference 3, where the curr
20、ent, voltage and power equations are projected in p-q-r rotating frame of reference. Fig.6 shows the voltage components in both of the fixed - and rotating p-q frame of reference for a single phase power system. The r-axis is considered to be identical to the zero axis, hence the voltage transformat
21、ion equation from the fixed frame of reference - to the rotating frame of reference p-q-r, can be written as: The currents in the rotating frame of reference, ip, iq and ir are related to the currents in the stationary frame of reference, i and i by similar equations as the voltage equations in Eq.1
22、1. Moreover, the following relations can be derived in the p-q-r rotating frame of reference: 3 DERIVATION OF REFERENCE CURRENT EXPRESSIONS FOR THE ACTIVE FILTER In this section instantaneous expressions for the reference currents for an active power filter to compensate for the harmonic distortion
23、or reactive power or both in the single phase power system under investigation are derived. Because of the symmetry of the complex voltage and current vectors trajectories, Fig.1, the average value of the active and reactive powers for both of the real and imaginary/fictitious phases can be evaluate
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