Daniel G. Forchetti

Adaptive Observer for Sensorless Control of Stand-Alone Doubly Fed Induction Generator

A sensorless control strategy for a doubly fed (wound rotor) induction machine working in variable-speed stand-alone power systems without using mechanical sensors is presented in this paper. Stator voltage magnitude and frequency are regulated using two field-oriented control loops. A Luenberger observer is used to estimate the stator flux, while an adaptive scheme modifies the rotor position required in the stator flux estimation. Stator voltage magnitude and frequency control loops behave very well for steady state as well as for transient states like startup, speed variations, or electric load changes. Experimental results are presented to validate this proposal.

Vector control strategy for a doubly-fed stand-alone induction generator

A voltage and frequency control for a stand-alone doubly-fed induction generator is presented in this paper. The control strategy consists of a simple vector control with impressed rotor currents. This strategy allows generating constant frequency and voltage with variable mechanical speed. Experimental results where obtained using a 5.5 kW induction machine. The behavior of the voltage and frequency, under variable speed and load, are shown. The experimental results confirm the feasibility of this proposal.

Comparison of positive sequence detectors for shunt active filter control

The influence of using different methods to detect the positive sequence of the grid voltage fundamental component on shunt active filter control is analyzed in this work. Three kind of positive sequence detectors are considered: detectors based on the pq Teory, EPLL-based detectors and those based on SOGI. Shunt active filter behavior is analyzed through simulation results using each one of these positive sequence detectors on balanced grid voltage, unbalanced grid voltage and unbalanced and distorted grid voltage conditions.

Non-linear control of a three-phase front end converter

The design of a non-linear controller for a three-phase front end converter used to connect renewable energy sources to the grid is presented in this paper. The objectives of this controller are the injection of all the generated power into the grid and the control of the reactive power exchanged with the power system. The system is represented through Park coordinates and port controlled Hamiltonian models. The controller is designed by interconnection and damping assignment (IDA), and feedback linearization (FL). It is demonstrated that for the particular case of selecting interconnection and damping matrixes, then coupling can be eliminated from the system model and therefore the controller designed using interconnection and damping assignment results the same as that using feedback linearization. The control strategy proposed in the present work is validated through simulation.

Power Flow Maximization in Permanent-Magnet Generators

The main hypothesis proposed in this paper is that by controlling the harmonic and zero-sequence components of the current in nonsinusoidal permanent-magnet synchronous generators (PMGs), additional energy can be obtained, thereby increasing the machine power density without increasing the Joule effect losses. Two different strategies are proposed for three- and four-wire topologies; therefore, four different cases are analyzed. The strategies consist in controlling the PMG stator currents, following a function that depends on the waveform of the back electromotive force (EMF). The current function is obtained from the instantaneous reactive power theory. An experimental system was built to validate the proposal. Experimental results prove that it is possible to increase power in a tested PMG by 7% using the four-wire topology in comparison with the conventional block commutation and same losses. Higher power gain can be obtained for machines with almost rectangular-shaped EMF waveforms.

Energy transference maximization in permanent magnet synchronous generators

A control method is proposed with the objective of maximizing the energy transference in permanent magnet synchronous generators (PMSG). Such control is based on the evaluation of instantaneous power components as well as of the optimization strategies to obtain the generator reference currents. Two possibilities are studied in the present work: with connection and without connection to neutral, for generators with three different EMF waveforms. In addition, two possibilities for each connection type are also presented in this effort. The first strategy has the main objective of generating at constant power and with minimum losses. On the other hand, the main objective of the second strategy is to get the maximum power while preserving the generator thermal limits. Simulation results are presented and analyzed to validate the proposed strategies. From these results, it can be concluded that when neutral is connected, it is possible to take advantage of the homopolar components of the generator EMF by imposing and adequate current with the objective of maximizing the generator power.

Application of the modified IDA‐PBC for shunt active power filters control

Summary The design of a passivity-based nonlinear controller for a shunt active power filter to be used for the compensation of harmonic currents consumed by nonlinear loads is presented in this paper. The main objective of designed controller is to inject the necessary compensation current into the system so that the grid current is sinusoidal and balanced, regardless of whether the grid voltage is unbalanced and/or distorted. The references for the compensation currents are obtained from applying the pq theory. The controller is designed on the basis of a modified interconnection and damping assignment technique, which allows solving a tracking control problem. An integral action controller is added to the proposed controller using the same design technique, in order to eliminate the errors produced by parameter variations or uncertainties. The behavior of the proposed control strategy is validated through simulation using a realistic model, which includes converter switching and losses, grid distortion, and parameter variations. Copyright

Passivity Based Control of a Three-Phase Front End Converter

A new controller aimed to regulate voltage and frequency of a Front-End Converter used in stand-alone wind generation systems is proposed. Control objective is to maintain the output voltage with constant amplitude and frequency, independently of the load supplied. Controller is designed using the Interconnection and Damping Assignment technique. System stability is ensured through a proper choice of the energy function of the system in closed-loop. The behavior of the proposed control strategy is validated through simulations using a realistic converter model.

Passivity-based control of a three-phase Front End Converter for stand alone wind generation system

A new controller aimed to regulate voltage and frequency of a Front-End Converter used in stand-alone wind generation systems is proposed. Control objective is to maintain the output voltage with constant amplitude and frequency, independently of the load supplied. Controller is designed using the Interconnection and Damping Assignment technique. System stability is ensured through a proper choice of the energy function of the system in closed-loop. The behavior of the proposed control strategy is validated through simulations using a realistic converter model.

Power flow control with losses minimization and fault tolerance for PMSG

This paper proposes a loss minimization control including fault tolerance for variable-speed permanent magnet synchronous generators, for which it is required that power flows stays constant and the generated energy processed through a AC/DC/AC power converter. It propose and compare two different 4-wires topologies. In the first topology, the neutral point of the generator is connected to a fourth leg of the inverter, and in second topology, it is connected to the midpoint of the DC bus capacitor bank. The main advantage of both options is that once fault occurs, is not necessary to reconfigure the inverter topology which means no need for additional switches. In addition, there is no need for modifying the control algorithm during fault. Another characteristic of the proposed control algorithm is that it allows limiting the generator losses to its maximum admissible value during operation, even under fault conditions. Simulation results are also presented to validate the proposed control strategies.