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ABSTRACT: The instantaneous reactive power theory has been the most used in nonlinear load compensation with active power filters (APF). Its application to APF control allows constant source power to be obtained after compensation in a simple way. It works optimally with balanced and sinusoidal source voltage, but not so good with unbalanced or non-sinusoidal source voltage. Although the p - q theory obtains constant source power in all the cases, in the second one the source current obtained is not balanced and sinusoidal. On the other hand, some researches argue that it is not a complete power theory because it does not assign a physical meaning to the power terms. Necessary modifications in the original formulation to treat compensation under any condition of voltage supply are discussed. Moreover, here, it is reformulated in phase coordinates, which allows a simpler treatment for analysing the different compensation strategies. On the other hand, from the power point of view, it is proved that the introduction of instantaneous imaginary power makes p - q formulation a formal theory of electric power in three-phase system. Finally, compensation strategies are applied to a practical power system and the results are presented.
IET Power Electronics 10/2009; · 1.62 Impact Factor
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ABSTRACT: 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.
IEEE Transactions on Industrial Electronics 07/2009; · 5.16 Impact Factor
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ABSTRACT: In this paper, the five main formulations of the instantaneous reactive power theory have been chosen to study nonlinear load compensation. They are p-q original theory, d-q transformation, modified or cross-product formulation, p-q-r reference frame, and vectorial theory. The obtention of the compensation current according to each formulation has been established. Next, the behavior of an active power filter (APF) that is implemented with those different control algorithms has been studied. On one hand, a simulation platform with control, APF, and load has been built to test them. Results obtained in an unbalanced and nonsinusoidal three-phase four-wire system have been compared by means of the most adequate indexes. On the other hand, the APF control strategies have been implemented in an experimental platform constituted by a 20-kVA power inverter and a 400-MHz digital signal processing controller board. The final analysis shows that, in general, the five theories present a different behavior, which depends on supply voltage, with respect to distortion. However, all of them widely decrease the waveform distortion. Moreover, a more general compensation objective is possible. It obtains balanced and sinusoidal source current in any conditions of the supply voltage.
IEEE Transactions on Industrial Electronics 02/2008; · 5.16 Impact Factor
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ABSTRACT: The original instantaneous reactive power or p-q theory has been used in a systematic way in the control of active power niters (APFs). When the APF is switched in parallel to a nonlinear and unbalanced load, the application of p-q theory allows a constant power compensation strategy. This means that after the APF connection, the supply instantaneous power is constant and presents the same value as the load average power. The use of other compensation strategies such as unity power factor, sinusoidal or balanced supply currents, among others, is also possible, as the development of another compensation strategy is possible within the p-q theory frame. A p-q theory reformulation without using mapping matrices is presented, which makes obtaining compensation currents easier. Finally, an exhaustive analysis of practical cases has been carried out at simulation and experimental levels through a laboratory prototype that has allowed verification of the proposed approach.
IET Electric Power Applications 10/2007; · 1.17 Impact Factor
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ABSTRACT: The control strategy derived from the instantaneous reactive power theory is one of the most commonly used in the Active Power Filters (APFs). For the last decades other formulations have been developed in order to achieve compensation objectives different to the proposed in the original one. Nevertheless, all of them can be only applied to three-phase systems, i.e.: in those formulations frameworks, they can not be used to obtain the control strategy for a polyphase system. This paper presents a new approach which can be applied to n wire systems. The powers and currents expressions derived from the formulations presented up now can be obtain applying this new approach. In this paper, the original p-q and the modified p-q formulation expressions are obtain in the new approach framework.
Industrial Electronics, 2007. ISIE 2007. IEEE International Symposium on; 07/2007
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ABSTRACT: 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 has not suffered modification; so it used the constant power compensation strategy. In this way, the supply instantaneous power after compensation is constant. This kind of compensation strategy presents good results in the case of balanced and sinusoidal voltages; however, it is not appropriate in the case of unbalanced or nonsinusoidal voltages. This paper extends the p-q theory to get control strategies which allow to attack the unity power factor compensation or the balanced and sinusoidal currents compensation.
IEEE Transactions on Power Delivery 08/2006; · 1.35 Impact Factor
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ABSTRACT: A combined system of passive and active filters for a four-wire three-phase system has been designed and simulated with Matlab/Simulink. A new control method based in the power vectorial theory and symmetrical components has been applied. The combined system mitigates the source current harmonics, compensates unbalance voltages, voltage harmonics, eliminates sags and reduces the problems of using only a shunt passive filter. The system is subjected to different voltage sources in accord to the IEC 61000. Simulation results are presented and discussed
Electrotechnical Conference, 2006. MELECON 2006. IEEE Mediterranean; 06/2006
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ABSTRACT: In this paper, the five main formulations of the instantaneous reactive power theory have been chosen to study a nonlinear load compensation. They are p-q original theory, d-q transformation, modified or cross product formulation, p-q-r reference frame and vectorial theory. The obtention of the compensation current according to each formulation has been established. Next, the behavior of an active power filter (APF) implemented with those different control algorithms have been studied. The APF control strategies have been implemented in an experimental platform constituted by a 20 kVA power inverter and a 400 MHz digital signal processing (DSP) controller board. Results got from an unbalanced and non-sinusoidal three-phase four-wire system have been compared. The final analysis shows that, in general, the five theories present a different behavior, depending on the supply voltage, respect to the distortion. However, all of them widely decrease the waveforms distortion. Moreover, a more general compensation objective is possible. It obtains balanced and sinusoidal source current in any conditions of supply voltage
Electrotechnical Conference, 2006. MELECON 2006. IEEE Mediterranean; 06/2006
