Jesús R. Vázquez

Compensation in nonsinusoidal, unbalanced three-phase four-wire systems with active power-line conditioner

For three-phase four-wire circuits, two compensation criteria have been established: one based on the instantaneous value concept and the other on the average value concept. Thus, according to the instantaneous value concept the non instantaneous power current is reduced, without altering the instantaneous active power. According to the average value concept, the nonactive average-current is reduced, without altering the average power. When the zero-sequence voltage component exists, both compensation types would not enable the zero-sequence (neutral) source current elimination. Then, two approaches are marked in this paper. The first one is for eliminating the non instantaneous power current or the nonactive average-current but the neutral current can still flow. The second one for eliminating the modified non instantaneous power current or the modified nonactive average-current, thus the neutral current component is compensated. According to recent recommendations in this work three-phase systems are considered as four-conductor systems. Experimental results are obtained to confirm the theoretical properties and to show the compensator performance.

Active Power-line Conditioners

Nowadays, the active power filters, APFs, can be used as a practical solution to solve the problems caused by the lack of electric power quality, EPQ. The emerging technology of power-electronic devices and the new developments in digital signal processing, DSP, have made possible its practical use. These power filters can fully compensate the nonlinear loads of electrical power systems: harmonics, reactive power, unbalances, etc. So, they can be called active powerline conditioners (APLCs). There are many configurations of APLCs, from shunt and series connection to hybrid passive-active filters. The target is to optimize the design using the advantages of each filter with the different load configurations.

Three-phase active power filter control using neural networks

A new control method for active power filters (APF) using neural networks is presented. It is pulse width modulation control (PWM) designed with two blocks that include neural networks. The first one includes adaptive networks that estimate the reference compensation current; adaptive linear neurons (Adaline) were used. The second one includes a feedforward network that works as a hysteresis band comparator; this network is multilayer and it has been trained by a backpropagation algorithm. A practical case with Matlab-Simulink is presented to check the proposed control performance.

A series-parallel configuration of active power filters for VAr and harmonic compensation

A new design method for the control implementation of a combined series-shunt active power filter (load compensation active conditioner, LCAC) for electrical power quality improvement is proposed. This active conditioner allows to cancel source voltage harmonics, to symmetrize the supply voltage, and to eliminate current harmonics and reactive/unbalanced load currents. The study of the higher harmonics passive filtering behaviour has permitted an enhancement of the compensating performance of the active conditioner. Practical case results are presented to support the performance of the new control design.

Practical design of a three-phase active power-line conditioner controlled by artificial neural networks

Today, there is an increase of harmonic pollution in electrical systems due to the use of nonlinear loads. Thus, the current and voltage waveforms are nonsinusoidal. The active power-line conditioners (APLCs) are used to compensate the generated harmonics and to correct the load power factor. In this paper, a new APLC control design based on artificial neural networks is developed. Adaptive networks estimate the control reference compensation currents, and a feedforward network (trained by a backpropagation algorithm) implements the pulsewidth-modulation (PWM) control method used. An experimental prototype was built to test the proposed design. The practical results confirm the possibility and usefulness of controlling an APLC by means of artificial neural networks.

Backstepping Control of Smart Grid-Connected Distributed Photovoltaic Power Supplies for Telecom Equipment

Backstepping controllers are obtained for distributed hybrid photovoltaic (PV) power supplies of telecommunication equipment. Grid-connected PV-based power supply units may contain dc-dc buck-boost converters linked to single-phase inverters. This distributed energy resource operated within the self-consumption concept can aid in the peak-shaving strategy of ac smart grids. New backstepping control laws are obtained for the single-phase inverter and for the buck-boost converter feeding a telecom equipment/battery while sourcing the PV excess power to the smart grid or to grid supply the telecom system. The backstepping approach is robust and able to cope with the grid nonlinearity and uncertainties providing dc input current and voltage controllers for the buck-boost converter to track the PV panel maximum power point, regulating the PV output dc voltage to extract maximum power; unity power factor sinusoidal ac smart grid inverter currents and constant dc-link voltages suited for telecom equipment; and inverter bidirectional power transfer. Experimental results are obtained from a lab setup controlled by one inexpensive dsPIC running the sampling, the backstepping and modulator algorithms. Results show the controllers guarantee maximum power transfer to the telecom equipment/ac grid, ensuring steady dc-link voltage while absorbing/injecting low harmonic distortion current into the smart grid.

Instantaneous Reactive Power Theory to N Wire Systems

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.

Practical implementation of a three-phase active power line conditioner with ANNs technology

In this paper, a new method to control an active power line conditioner (APLC) using neural networks is presented. Actually, there is an increase of voltage and current harmonics in power systems, caused by nonlinear loads. The APLCs are used to compensate the generated harmonics and to correct the load power factor. The proposed control design is a pulse width modulation control (PWM) with two blocks that include neural networks. Adaptive networks estimate the reference compensation currents. On the other hand, a multilayer feedforward network (trained by a backpropagation algorithm) works as hysteresis band comparator. An experimental prototype was built to check the proposed control performance. The practical results confirm the possibility and usefulness of controlling an APLC by means of artificial neural networks.

A New Control for a Combined System of Shunt Passive and Series Active Filters

A new control algorithm for a hybrid filter formed by a series active filter and a passive filter connected in parallel with the load is proposed. The new control strategy is based on the dual formulation of the vectorial theory of electric power, so that the signal injected by the active filter is able to compensate the reactive power and the harmonics of the load current. To verify the developed theoretical analysis, the proposed control scheme has been simulated in the platform MATLAB-Simulink and applied to a three-phase three-wire system. The simulation results to verify the effectiveness of the proposed control algorithm are presented.

Practical application of the instantaneous power theory in the compensation of four-wire three-phase systems

For three-phase four-wire circuits, two compensation criteria are possible: one based on the instantaneous value concept and the other on the average value concept. Thus, according to the first method the noninstantaneous power current is reduced, without altering the instantaneous active power (time-instantaneous compensation, TIC). On the other one, according to the second method the nonactive current is reduced, without altering the average power (time-average compensation, TAC). When the zero-sequence voltage component exists, both compensation types, would not enable the zero-sequence (neutral) source current elimination. Then, two approaches are marked in this paper. The first one, is for eliminating the noninstantaneous power current or eliminating nonactive current component but neutral current can still flow. The second one for eliminating the modified noninstantaneous power current or the modified nonactive current, thus the neutral current components is compensated. Experimental results are obtained to confirm the theoretical properties and show the compensator performance.