This paper proposes an observer-based volts-perhertz (V/Hz) control method for synchronous motors. The method is applicable to any synchronous motor type, from permanentmagnet (PM) motors to synchronous reluctance motors (SyRMs). The method consists of a state-feedback control law and a state observer, both of which are designed to be inherently sensorless. The gains can be selected using simple closed-form expressions, resulting in a locally stable and passive system in the whole feasible operating range. Unstable regions and heuristic tuning of conventional V/Hz control are thus avoided. Compared to sensorless field-oriented control, neither speed controller nor separate field-weakening method is needed, the full inverter voltage can be utilized, and the sensitivity to parameter errors is reduced. For the majority of industrial drive applications, the dynamic performance of the proposed method is adequate.
This paper deals with standstill identification of an induction motor drive for sensorless self-commissioning purposes. The proposed identification method is based on an advanced model of a squirrel-cage induction motor. The model includes the deep-bar effect and the magnetic saturation characteristics. The excitation signals are fed to the stator using a standard inverter without compensating for its nonlinearities. The saturable stator inductance is first identified by means of a robust flux-integration test, where unknown voltage disturbances are canceled with suitably selected current pulses. Then, the deep-bar characteristics are identified by means of a DC-biased sinusoidal excitation using different frequencies. Finally, the cross-saturation characteristics of the rotor leakage inductance are identified by altering the DC bias of the excitation signal. The identified characteristics are transformed to the parameters of the advanced motor model taking into account the interrelations of the above-mentioned phenomena. Since the physical phenomena affecting the standstill identification process are properly included in the identified model, less approximations are needed and more accurate parameter estimates are obtained. The identification procedure is validated by means of experiments using two different induction motors (5.6 kW and 45 kW).
This paper proposes an observer-based volts-perhertz (V/Hz) control method for induction motors. The proposed method consists of a state-feedback control law and a flux observer, both of which are designed to be inherently sensorless. The gains can be selected using simple closed-form expressions, resulting in a locally stable and passive system in the whole feasible operating range. Unstable regions and heuristic tuning of conventional V/Hz control are thus avoided. Compared to sensorless field-oriented control, no speed controller or separate field-weakening method is needed, the full inverter voltage can be utilized, and the sensitivity to parameter errors is reduced.
This paper deals with the parameter identification of an induction motor at standstill. A comprehensive identification procedure is analyzed, describing a robust flux-integration method for main-flux saturation characteristics and transient tests for rotor-side parameters. The influence of the main-flux saturation on the transient test results and on the identified rotorside parameters is studied, and improvements are suggested. The identification procedure is validated by means of experiments using 2.2-kW and 5.6-kW induction motors. Index Terms-Induction motor drives, parameter identification, saturation characteristics.
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