This paper deals with discrete-time models and current control methods for synchronous motors with a magnetically salient rotor structure, such as interior permanent-magnet synchronous motors and synchronous reluctance motors (SyRMs). The dynamic performance of current controllers based on the continuous-time motor model is limited, particularly if the ratio of the sampling frequency to the fundamental frequency is low. An exact closed-form hold-equivalent discrete motor model is derived. The zero-order hold of the stator-voltage input is modeled in stationary coordinates, where it physically is. An analytical discretetime pole-placement design method for two-degrees-of-freedom proportional-integral current control is proposed. The proposed method is easy to apply: only the desired closed-loop bandwidth and the three motor parameters (R s , L d , L q ) are required. The robustness of the proposed current control design against parameter errors is analyzed. The controller is experimentally verified using a 6.7-kW SyRM drive. Index Terms-Current control, delay, discrete-time model, interior permanent-magnet synchronous motor (IPM), saliency, synchronous reluctance motor (SyRM), zero-order hold (ZOH). I. INTRODUCTIONS YNCHRONOUS motors with a magnetically salient rotor-such as interior permanent-magnet synchronous motors (IPMs), synchronous reluctance motors (SyRMs), and permanent-magnet (PM)-assisted SyRMs-are more and more applied in hybrid (or electric) vehicles, heavy-duty working machines, and industrial applications. In these applications, the maximum speeds and, consequently, the maximum operating frequencies can be very high (e.g., 12 000 r/min corresponding to the frequency of 1000 Hz for a ten-pole machine). Since the switching frequency of the converter feeding the motor Manuscript
In high-performance control of ac machines through variable frequency drives, the knowledge of machine parameters plays a decisive role. The accuracy with which machine parameters can be known is directly related to the time and effort put in testing and commissioning process. In the ever-demanding industrial environments, the time spent on parameter identification translates into loss of production. To reduce commissioning times, research in this direction has focused on automatizing the identification procedure without loss of accuracy. This paper reviews different lines of research adopted over the past few decades for machine parameter identification. Parameter estimation of ac machines is considered because of their widespread applications from servomechanisms to traction to aviation. The surveyed works include self-commissioning schemes that have become an integral part and salient feature of modern electric drives. This feature enables the drives to automatically identify machine parameters and tune the control loops.
Abstract-This paper deals with the speed and position estimation of interior permanent-magnet synchronous motor (IPMSM) and synchronous reluctance motor (SyRM) drives. A speedadaptive full-order observer is designed and analyzed in the discrete-time domain. The observer design is based on the exact discrete-time motor model, which inherently takes the delays in the control system into account. The proposed observer is experimentally evaluated using a 6.7-kW SyRM drive. The analysis and experimental results indicate that drastic performance improvements can be obtained with the direct discrete-time design, especially if the sampling frequency is relatively low compared to the fundamental frequency.
Tuovinen, T. (2018)Abstract-This paper deals with the speed and position estimation for synchronous reluctance motors (SyRMs) and interior permanent-magnet synchronous motors (IPMs). A unified design and analysis framework for a class of back-electromotive-force (back-EMF)-based observers is developed and the links between apparently different estimation methods are brought out. State observers equipped with a speed-adaptation law are shown to be mathematically equivalent to voltage-model-based flux observers equipped with a position-tracking loop. The error signal driving the adaptation law or the tracking loop is presented in a generalized form. Using the framework, a stabilizing gain design is reviewed and detailed design guidelines are given. Selected observer designs are experimentally evaluated using a 6.7-kW SyRM drive and a 2.2-kW IPM drive.
Electric drive trains have a torsional rigid-body vibration mode at a small, non-zero frequency. If an excitation occurs close to this frequency, the vibration amplitude may grow large and the electrical machine may suffer from significant additional losses. Standards set constraints on the oscillating torque in the shaft coupling and on the harmonics of line current. They indirectly limit the vibration amplitude and losses of the machines.Time-discretized finite-element analysis was used to study the losses of six induction and six synchronous machines under torsional vibration restricted by the constraints above. All the machines were supplied from sinusoidal voltage sources. In the worst cases of the induction motors, the vibration increased the electromagnetic total loss by about 20%. The constraints on synchronous machines are milder than those for induction machines. In this case, the maximum increase of the loss was 75%. The limit on the harmonic currents is essential from the loss point of view. Without this limit, the additional loss at the rigid-body resonance would lead to a temperature rise high enough to destroy the insulation system of the machine.The method of loss analysis was validated by measured results.
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