Iliya Ralev

Is acoustically oriented control always inefficient for an automotive switched reluctance machine

Recent publications have shown that the adverse acoustic behavior of automotive-size switched reluctance machines can be tackled by aid of Direct Instantaneous Force Control. The former work mainly focused on the functionality regarding acoustics. This paper, however, compares the drive losses between standard Hysteresis Current Control and Direct Instantaneous Force Control. Iron loss, copper loss and losses of the inverter were investigated by simulation. It turned out that iron loss decreases when applying Direct Instantaneous Force Control. Ohmic losses inevitably increase, though. Therefore, it depends on the load-cycle of the vehicle whether Direct Instantaneous Force Control or standard control is preferable.

Measuring SRM profiles including radial force on a standard drives test bench

Switched reluctance machines exhibit highly nonlinear characteristics which must be known to accurately model and control this machine type. These profiles are typically derived by finite-element analysis or measured on dedicated test benches. The aim of this paper is to propose a measurement procedure that requires only standard laboratory equipment. Moreover, a method is presented that allows the reconstruction of the radial-force characteristic, which has never been mentioned before in literature. A standard current source and a differential voltage probe were used to measure flux linkage. Afterwards torque was derived from the flux-linkage profile. Radial force was reconstructed by the aid of vibration excited under particular test circumstances. At the end the three fingerprint characteristics of the machine, i.e., flux linkage, torque and radial force, are known. The results are robust against measurement noise since they are obtained by averaging numerous electrical cycles.

Technology, research and applications of switched reluctance drives

Electrical drives are one of the major consumers of electrical energy and their penetration in the market is still growing. Hence, for many drive applications efficient, reliable and cost effective solutions have to be found. Switched reluctance drives (SRD) offer a potential solution when focus is mainly on cost and robustness. However, to benefit from the unique advantages of this machine type a deep understanding of its strongly non-linear behavior is required. After discussing some major differences to classic rotating field machines, this paper presents a broad overview of the state of the art of SRD taking into consideration all aspects relevant to machine modeling, design and control development process. Finally, applications on the market utilizing SRDs and the focus of current research is presented. After reading this paper the reader will be able to assess if this modern drive technology could be advantagous in a given application.

Impact of smooth torque control on the efficiency of a high-speed automotive SRM drive

Switched reluctance motors are an alternative to conventional rotating field machines due to their robust mechanical design and low-cost production. In automotive drives the application of a dedicated algorithm for torque ripple reduction is indispensable as otherwise mechanical resonances in the drive train are excited. In this paper an automotive-sized high-speed SRM drive is investigated for two different control schemes - hysteresis current control and pwm-based direct instantaneous torque control. The main focus of the study lies on the evaluation of both algorithms in terms of efficiency. An analytic loss analysis in selected operating points is carried out and confirmed by simulation. Furthermore a comparison of experimentally derived efficiency maps is presented.

Acoustic optimization using vibration sensor feedback to the controller

Switched reluctance machines have the drawback of a high acoustic excitation. This paper presents an acoustic optimization method that analyzes the signal of a vibration sensor in the control loop and is able to eliminate mode-0 borne vibrations. A search algorithm which determines the optimized control parameters is proposed. The potential of the control concept is described including measurement results.

Impact of Smooth Torque Control on the Efficiency of a High-Speed Automotive Switched Reluctance Drive

This paper examines the efficiency performance of an automotive-size high-speed switched reluctance drive. It investigates the impact of a smooth torque control algorithm on the efficiency and losses in the drive. In automotive drives, the application of a dedicated algorithm for torque ripple reduction at low to medium speed is indispensable to avoid excitation of mechanical resonances in the drive train. The predictive direct instantaneous torque control method is compared with efficiency optimized hysteresis current control in terms of efficiency. Dynamic finite-element loss analysis is employed to investigate the source of the efficiency deviation and the results are verified by measurements. The study shows that the requirement for smooth torque leads to a decrease in the drives efficiency and altered loss distribution. The efficiency map comparison reveals that the efficiency degradation amounts to 4–9% for this particular drive.

Adopting a SOGI filter for flux-linkage based rotor position sensing of switched reluctance machines

Position sensorless control of switched reluctance motors reduces the system cost and increases the drives overall reliability. The flux-linkage method is a commonly applied technique when sensorless control of switched reluctance motors is pursued. The sensing quality, though being sensitive to model errors and further effects, can be sufficient for a number of applications. However, sophisticated control algorithms like predictive direct instantaneous torque control and direct instantaneous force control require highly accurate rotor position estimation. Current profiling methods rely on accurate position sensing as well. The main objective of the present paper is the improvement of the conventional flux-linkage method by adopting a band pass filter and a self-characterization routine. As a result the estimation error can be crucially reduced and the operation area of the flux-linkage method can be expanded. The paper includes simulative and experimental validation of the algorithm.

Wide speed range six-step mode operation of IPMSM drives with adjustable dc-link voltage

Driving a synchronous machine in overmodulation region and six-step mode is a common way to reduce switching losses in the inverter and fully utilize inverter output voltage. Main issues concerning this operating area in combination with state of the art field oriented control are saturation of the current controller and reduced torque dynamics. This paper presents a strategy that is based on a voltage angle control in order to improve dynamics and overcome stability problems of the PI-controller. An additional dc-link voltage control loop for drive trains including a dc/dc converter gives the designer a new degree of freedom to improve the drives overall efficiency. Precise control of both dc-link and inverter output voltages creates the possibility to shift six-step mode to an arbitrary operating region including base speed.