Naveed ur Rehman Malik

Induction machine at unity power factor with rotating power electronic converter

A new configuration for the self-excitation of the induction machine invented by Magnus Lindmark is presented. The power electronic converter using solid state switches is connected to the rotor while the stator is directly connected to the grid. Using appropriate control, the reactive power consumed by the motor can be generated in the rotor resulting in unity power factor operation. The rotor connected power electronic converter is also used for constant speed operation of the induction machine at variable torque.

Brushless doubly-fed induction machine with rotating power electronic converter for wind power applications

This paper introduces, simulates and analyzes a new topology of a brushless doubly-fed induction machine with rotating power electronic converter for wind power applications. Topology consists of two machines, one is the main machine which is directly connected to the grid while the second machine is the auxiliary machine which handles the slip power. The rotor of the two machines are connected via a power electronic converter which is mounted on the shaft and rotates with it. The steady state equivalent circuit of the two machine configuration is developed and analyzed. It is shown through simulations that the stator terminals of the machine can be operated at a unity power factor for variable speed range. Furthermore, it is shown that the presented system operates at a high efficiency at rated load and unity power factor.

Theoretical and experimental investigation of the self-excited rotating power electronic induction machine

This paper presents the theoretical model and analysis of a novel topology of the self-excited induction machine using rotating power electronic converters. The power electronic converters are connected to the rotor of the induction machine and it is shown that the machine operates at unity power factor at variable load conditions including rated load. Special control strategy of the two converters helps in magnetization of the induction machine from the rotor. The experimental analysis is conducted in the industry using 11kW induction machine and close agreement is found between the theoretical model and the experimental results. Besides, the rotor resistance is varied and its effect on the power factor and performance of the machine is studied and analyzed.

Consensus control for induction motors speed regulation

Cyber Physical Energy Systems (CPES) development requires the combination of distributed intelligence to fulfill the future complex tasks and reach the increase the energy demands. Electrical Industrial Systems (EIS) are in continuous evolving integrating new technologies allowing to a better performance and increase the efficiency. This paper applies the consensus protocol for Multi-Agent Systems (MAS) to control the speed of multiple induction motors. In this paper, the behaviour of the system under different disturbances and scenarios has been simulated, thus, confirming the suitability and simplicity of this method for coordinating the control actions.

Transient and steady-state 3-D electro-thermal design and analysis of the rotating power electronic IGBT converter

This paper deals with a 3-dimensional development of a thermal model of a power electronic converter mounted on the generator shaft and rotating with it. The dimensions of the heat sink are determined and the temperature gradients of the converter, its heat sink, and shaft during natural and forced convection are analyzed for variable rotor speeds. It is shown that the chosen sizes of the IGBT and heat sink offers compact design of the rotating converter, which is sufficient for its mounting in the limited space, offered by the generator shaft. Furthermore, transient temperature profile is also presented.

Extended vector control of a rotating power electronic brushless doubly-fed induction generator under unsymmetrical voltage sags

This paper presents the implementation of the extended vector control on a new type of brushless doubly-fed generator when subjected to unsymmetrical voltage dips. This new type of generator has partially rated power electronic converter and exciter mounted on the shaft and rotating with it. The unbalanced voltages introduce positive and negative sequence components in the generator. The negative sequence components gives rise to torque oscillations and extra heating in the generator and power electronics which could affect the life time of the shaft, gearbox and electronic equipment. Two separate synchronous reference frames are defined and standard PI controllers are implemented in the reference frames in order to control the positive and negative sequence currents independently. Through these means the effect of the negative sequence currents is mitigated and it is shown that the oscillations in the behavior of this new type of generator are considerably reduced.

Evaluation of the synthetic inertia control using active damping method

The current and massive deployment of non-synchronous generation is degrading the inertial response in power systems. The addition of an extra control loop, the so-called synthetic inertia, can contribute in the improvement of the frequency response, through an additional power injection. In this paper, the active damping method is used to enhance both, the closed-loop current control and the synthetic inertia control loop. A full aggregated model of a wind turbine generator (WTG) is integrated in a test system. The results obtained show an increase in the power injected into the grid, thereby improving the frequency response after a frequency disturbance. Moreover, the response of the closed current-control loop and voltage loop are presented, in order to show their interaction with the synthetic inertia control.

Construction of a rotating power electronic converter for induction machine operation

This paper describes the construction of the rotating power electronic converter. By mounting the power electronics on the rotor of an induction machine, the rotor winding can be made easily accessible without the use of slip-rings and brushes. This offers certain advantages regarding motor control. However, it is evident that the rotating mass, communication with the converter and maintaining the mechanical stability and reliability of the system are huge challenges that must be overcome. This paper describes some solution that are partly investigated and some solutions that still needs to be investigated in more detail.

Synchronous operation of a rotating power electronic brushless doubly-fed generator

This paper presents the synchronous operation of a novel generator termed as the rotating power electronic brushless doubly-fed induction generator (RPE-BDFIG). It is shown that the generator operates well at the synchronous speed of the main machine, delivering the desired power to the grid. Furthermore, it is illustrated that the RPE-BDFIG behaves similar to a synchronous generator in the synchronous mode. The closed-loop control of the generator is implemented in real-time, and the current and voltage waveforms of the stator and rotor of the RPE-BDFIG are experimentally analyzed. The paper highlights the stable operation and full control of the generator during synchronous mode.