J. Proboste

MRAS observer for sensorless control of standalone doubly fed induction generators

This paper presents an analysis of a model reference adaptive system (MRAS) observer for the sensorless control of a standalone doubly fed induction generator (DFIG). The analysis allows the formal design of the MRAS observer of given dynamics and further allows the prediction of rotor position estimation errors under parameter mismatch. The MRAS observer analysis is experimentally implemented for the vector control of a standalone DFIG feeding a load at constant voltage and frequency. Experimental results, including speed catching of an already spinning machine, are presented and extensively discussed. Although the method is validated for a standalone generator, the proposed MRAS observer can be extended to other applications of the doubly fed induction machine.

Sensorless Control of Doubly-Fed Induction Generators Using a Rotor-Current-Based MRAS Observer

This paper presents a new sensorless method for the vector control of doubly-fed induction machines (DFIMs) without using speed sensors or rotor position measurements. The proposed sensorless method is based on the model reference adaptive system (MRAS) estimating the rotor position and speed from the machine rotor currents. The method is appropriate for both stand-alone and grid-connected operation of variable speed DFIMs. To design the MRAS observer with the appropriate dynamic response, a small signal model is derived. The sensitivity of the method for variation in the machine parameters is also analyzed. Speed catching on the fly and synchronization of the doubly-fed induction generator with the utility are also addressed. Experimental results obtained from a 3.5-kW prototype are presented and fully analyzed.

MRAS Observers for Sensorless Control of Doubly-Fed Induction Generators

This paper addresses the analysis and performance of several model reference adaptive system (MRAS) observers for sensorless vector control of doubly-fed induction machines. Small signal models allow the formal analysis of the observers for a given dynamic. The performance of each MRAS observer is analyzed, considering grid-connected and stand-alone operation. The MRAS observers are implemented in a 3.5 kW experimental prototype composed of a doubly-fed induction generator and a wind turbine emulator. Experimental results validate the predictions of the small signal models and demonstrate the performance of the sensorless methods during both steady state and variable speed wind energy generation.

Wind–Diesel Generation Using Doubly Fed Induction Machines

In this paper, the modeling and control strategy of a wind-diesel generation system are discussed. In the proposed topology, the diesel engine and the wind turbine are both variable-speed machines, allowing maximum fuel efficiency and optimal energy capture from the wind. A vector-controlled doubly fed induction generator is used in each generation system to provide fixed voltage and frequency to the load. The diesel unit balances the system power and changes the speed according to the power demand in order to minimize the fuel consumption. The electrical torque of the wind system generator is regulated to maximize the energy capture of the wind turbine. The advantages of operating a diesel engine at variable speed are discussed. The dynamic and steady-state operation of the wind-diesel system, including voltage and frequency control, active power balancing, and control of the reactive power supplied to the grid/load are analyzed in this paper. Experimental results, from a 3-kW experimental prototype are presented in this paper.

Sensorless Control of a Slip Ring Induction Generator based on Rotor Current MRAS Observer

A sensorless control strategy of a slip ring induction generator supplying energy to an isolated load is presented. The position, needed for the vector control scheme, is estimated using an MRAS observer. The input to the observer is the rotor current both from direct measurements (reference model) and from stator voltage and current measurements (adaptive model). The scheme is validated in a six poles, 2.5 kW induction machine. Sub and super synchronous operation is allowed using a Scherbius scheme with two back-to-back PWM voltage source inverters. The generator is driven at variable speed by an AC drive. Results are presented for the speed/position estimation during steady state and transient conditions

A hybrid topology for a variable speed wind-diesel generation system using wound rotor induction machines

In this paper a energy system topology consisting of a diesel and wind turbine generation units is presented. Wound rotor induction machines are considered to provide energy to an isolated load at constant voltage and frequency. Both generator rotor currents are vector controlled and operate at variable speed. The scheme uses a common DC bus for the voltage source PWM rotor side inverter of each machine. Another vector controlled voltage source PWM inverter is connected between the DC bus and the stator to allow sub and super synchronous speed operation of both generators. The diesel generator unit balances the system power and changes the speed according to power demand in order to minimise the fuel consumption. The variable speed operation of the wind energy conversion system maximises the energy capture by controlling the generator electric torque. An experimental prototype has been set with the diesel engine and the wind turbine emulated with a AC and DC drive respectively. The system has been tested to load impacts and step changes in wind velocity and experimental results for optimum speed tracking are shown.