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.

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.

This paper analyses the behavior of different active power filter (APF) control algorithms resulting from five formulations of the instantaneous power theory: p-q original theory, d-q transformation, modified or cross product formulation, p-q-r reference frame and vectorial theory are analyzed. A simulation platform with control + APF + load is built to test the different algorithms. The results obtained in an unbalanced and nonsinusoidal three-phase four-wire system are compared. The final analysis shows that from the five formulations, only the vectorial one allows balanced and sinusoidal source currents after compensation

There are several specific solutions for accessing sensors and actuators present in any process or system through a TCP/IP network, either local or a wide area type like the Internet. The usage of sensors and actuators of different nature and diverse interfaces (SPI, I2C, analogue, etc.) makes access to them from a network in a homogeneous and secure way more complex. A framework, including both software and hardware resources, is necessary to simplify and unify networked access to these devices. In this paper, a set of open-source software tools, specifically designed to cover the different issues concerning the access to sensors and actuators, and two proposed low-cost hardware architectures to operate with the abovementioned software tools are presented. They allow integrated and easy access to local or remote sensors and actuators. The software tools, integrated in the free authoring tool Easy Java and Javascript Simulations (EJS) solve the interaction issues between the subsystem that integrates sensors and actuators into the network, called convergence subsystem in this paper, and the Human Machine Interface (HMI)—this one designed using the intuitive graphical system of EJS—located on the user’s computer. The proposed hardware architectures and software tools are described and experimental implementations with the proposed tools are presented.

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.

Remote lab experiences are proliferating in higher education, although there are still few studies that manage to build a theoretical framework for educational assessment and design of this technology. In order to explore to what extent the use of facilitators of proximity to the laboratory and the autonomy of the experiment makes remote laboratories a technology accepted by students, two remote labs different yet similar educational conditions in laboratories are used. A sample of 98 undergraduate students from a degree course in Energy Engineering was used for this study; 57 of these students ran experiments in a laboratory of electrical machines and 41 in a photovoltaic systems laboratory. The data suggest using conditions that facilitate the proximity of the laboratory and the autonomy in the realisation of the experiment; in both laboratories the experience was positively valued by the students. Also, data suggest that the types of laboratory and experiment have influences on usability – autonomy and lab proximity – perceived by students.