Simultaneous Decoupling Voltage Amplitude and Frequency Control of Self-Excited Induction Generators 1=Engineering 2=Electrical Motors and Drive

Background. Self-excited induction generators (SEIG) have found wide application in autonomous (off-grid) electricity generating systems with prime movers based on renewables (wind- and hydro-turbines) or combustion engines. The main advantage of SEIGs compared to synchronous generators is that they are relatively inexpensive and possess natural short-circuit protection properties. The main drawback of SEIGs is their poor voltage regulation due to the change of both generated voltage amplitude and frequency with the change of load in addition to their dependence on the prime mover's velocity and excitation capacitance. In many cases this drawback results in a lot of engineers prefer to use permanent magnet synchronous generators instead of the SEIG. Whereas the solutions for the voltage amplitude control of the SEIG are widely presented in the literature, the problem of the simultaneous dynamic control of the voltage amplitude and frequency has not been analytically solved till now. There are some intuitive solutions feasible in steady states based on additional controllable dump loads [1] or useful controllable loads like water supply pumps [2], [3] which reduces the efficiency of the generating system and not suitable for dynamic control.

Goal of the research. To develop a systematic approach based on control theory for the design of decoupled control of the voltage amplitude and frequency of the SEIG leading to independent regulation of the voltage amplitude and frequency.

Objectives
To develop a control oriented model of SEIG with two outputs: voltage amplitude and frequency.
To design decoupling control of the voltage amplitude and frequency.
To develop a block diagram of the control system including STATCOM for amplitude regulation and voltage optimiser for the frequency regulation.
To set up an experimental test bench and determine parameters of the block diagram.
To simulate the control system in Matlab/Simulink.
To prototype rapidly the control system using dSpace or OPAL-RT.
To do the experimental research of the decoupled control.
To explore the case of single phase induction generator driven by air scroll motor.

Key methodologies. Linearisation of the nonlinear model of SEIG in the synchronous reference frame [4] performed for the frequency and voltage amplitude channels. Decoupling interconnected frequency and amplitude control channels.

Novelty of the research. For the first time, the solution of simultaneous dynamic decoupling control of the voltage amplitude and frequency will be found. Applicability of the voltage optimisation technique for the frequency control will be tested.

Practical value. The proposed system should make autonomous induction generators comparable with permanent magnet synchronous generators in sense of the voltage control quality. The voltage optimisation for the frequency control leads to no power dissipation in dummy loads.