Methods for the complementary design of the machine and the control in electric drive systems

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Electric drives are being used in an increasing number of applications, providing efficient energy conversion and allowing for control of motion. They can be found in industrial machinery, electric vehicles, renewable energy generators, home appliances, among other application fields.The targets for designing a drive system include high torque density, high efficiency, low manufacturing/maintenance costs, high reliability and high performance motion control. The research and development of the drives are mainly split in the electric machines on one side and in the control and power electronic systems in the other. In the usual approaches, the control system is designed assuming a given standard electrical machine or machine type. The machine on his part is designed assuming a standard control algorithm, like the field oriented control. The design of the machine and the design of the controller is generally performed by unrelated teams.In the case of permanent magnet synchronous machines (PMSM), the machine is usually designed for obtaining a sinusoidal back electromotive force (EMF), as it is assumed that the control supplies sinusoidal current. The control on his side is designed for supplying sinusoidal current assuming the back EMF is sinusoidal. In this way, a ripple free torque is obtained. However, these assumptions constrain the design of the machine and does not make use of all the potential of the power electronic and control system.It is expected that by designing the machine and the control in a complementary way, better characteristics can be obtained than when designed separately. This approach is rarely investigated and will be covered by the present proposal. There is a special potential to reach a simpler, however, still efficient drive system.Machines designed with purposeful nonsinusoidal EMF will be investigated in relation with a three phase four wire inverter i.e. with connected neutral, and with a new non-sinusoidal reference frame transformations for the control. With the aim of obtaining a simpler drive system without position sensor, the self sensing control will also be investigated. As the performance of self sensing techniques depend specially on characteristics of the machine, method for improving the self sensing capability of the machine and the suitable self sensing methods will be researched.The research will be performed based on modelling, simulation, and experimental tests on prototypes of the machine and the control system. Even though the research is focused on the PMSM, it is expected that the results can be at least partially used for other machine types.