Janne Salomäki

Sensorless Control of Induction Motor Drives Equipped With Inverter Output Filter

This paper deals with the speed sensorless vector control of an induction motor in a special case where the output voltage of the PWM inverter is filtered by an LC filter. The system states are estimated by means of an adaptive full-order observer, and no additional voltage, current or speed measurements are needed. The rotor speed adaptation is based on the estimation error of the inverter output current. Dynamic analysis is used to find an observer gain that enables a wide operation region, including very low and very high speeds. A torque-maximizing control method is applied in the field-weakening region. Simulation and experimental results show that the performance is comparable to that of a drive without the LC filter

Signal Injection in Sensorless PMSM Drives Equipped With Inverter Output Filter

This paper proposes a hybrid observer for sensorless control of permanent-magnet synchronous motor drives equipped with an inverter output LC filter. An adaptive full-order observer is augmented with a high-frequency signal injection method at low speeds. The only measured quantities are the inverter phase currents and the dc-link voltage. The effects of the LC filter on the signal injection are investigated, and it is shown that the filter is not an obstacle to using signal injection methods. The proposed method allows sensorless operation in a wide speed range down to zero speed. Experimental results are given to confirm the effectiveness of the proposed method.

Sensorless Vector Control of PMSM Drives Equipped With Inverter Output Filter

The paper presents a sensorless vector control method for a permanent magnet synchronous motor when the output voltage of the PWM inverter is filtered by an LC filter. The dynamics of the LC filter are taken into account in the design of the controller and adaptive full-order observer. The use of the output filter does not require additional current or voltage measurements. The speed adaptation is based on the estimation error of the inverter output current. Linearization analysis is used to design an observer that enables a wide operation region. Simulation and experimental results show the functionality of the proposed control method

Vector Control of an Induction Motor Fed by a PWM Inverter with Output LC Filter

Abstract This paper introduces a control method for an induction motor that is supplied by a PWM voltage source inverter through an LC filter. A cascade control structure is employed and a full-order observer is used to estimate the system states. Thus no additional voltage or current measurements are needed for the vector control of the motor. Two alternative methods are presented for the observer gain selection. Simulation and experimental results confirm the functionality of the proposed control method.

Sensorless control of induction motor drives equipped with inverter output filter

This paper deals with the speed sensorless vector control of an induction motor in a special case where the output voltage of the pulsewidth-modulated inverter is filtered by an inductance-capacitance (LC) filter. The system states are estimated by means of an adaptive full-order observer, and no additional voltage, current, or speed measurements are needed. The rotor speed adaptation is based on the estimation error of the inverter output current. Quasi-steady-state and linearization analyses are used to design an observer that enables a wide operation region, including very low and very high speeds. A torque-maximizing control method is applied in the field-weakening region. Simulation and experimental results show that the performance is comparable to that of a drive without the LC filter

Influence of Inverter Output Filter on Maximum Torque and Speed of PMSM Drives

The paper deals with the maximum torque and speed of permanent magnet synchronous motor (PMSM) drives when the inverter output voltage is filtered by an LC filter whose cut-off frequency is well below the switching frequency. According to steady-state analysis, the filter affects the performance of the motor drive especially at high speeds. The stator current is not equal to the inverter current, and due to the inverter current and inverter voltage limits, the torque-maximizing stator current locus differs from that of a drive without the filter. A field-weakening method is proposed for PMSM drives with an inverter output filter. The method is implemented and tested in a 2.2-kW PMSM drive. The experimental results agree well with the analysis, and validate the high-speed performance of the proposed field-weakening method.

Influence of Inverter Output Filter on the Selection of PWM Technique

This paper deals with the suitability of various pulse-width modulation techniques for a variable-speed AC drive equipped with a sinusoidal differential-mode and common-mode filter at the inverter output. Simulations and experiments are used for the investigation. If the average common-mode voltage is changed abruptly, the filter resonance may be excited, and the common-mode voltage at the motor terminals may rise to values higher than those obtained without the filter. This phenomenon may cause difficulties when the modulation is started, and it also creates a fundamental problem when a two-phase modulation method is used. The resonance problem can be avoided by selecting a modulation technique that does not cause sudden changes in the average common-mode voltage. A starting algorithm is proposed, enabling a trouble-free start of the drive equipped with a sinusoidal common-mode filter

Cost-Effective Design of Inverter Output Filters for AC Drives

The paper deals with the minimization of output filter cost in inverter-fed AC drives. The LC Alter design is constrained by the total harmonic distortions of the stator voltage and inverter output current, the voltage drop in the filter inductor, and the system resonance frequency. The last constraint is important from the control point of view, because the vector control requires that the sampling frequency is sufficiently higher than the resonance frequency. The design takes into account the frequency dependence of the filter resistance and inductance due to the eddy currents in the laminated iron- core inductor. The design method is further enhanced by taking into account the inverter power stage cost as a function of the switching frequency. The design minimizes the total cost of the inverter and filter, and determines the optimal switching frequency. Simulations and experiments show that the filter designed according to the proposed design procedure fulfils the design constraints, and the speed-sensorless control works well with the cost-optimized filter.

Field-weakening method for v/f -controlled hoist drive

This paper presents a field-weakening control method for V/f-controlled hoist drives. The method is based on the power limitation, which enables a load-dependent maximum speed without load measurement. In order to avoid the pull-out point of the hoist motor, the acceleration is halted if the motor input power exceeds a predefined limit. In addition, an integral (I) controller is used to reduce the steady-state error of the power limiter. The advantage of the proposed method is that a load sensor is not needed. Simulation and experimental results show that power limitation is suitable field-weakening method for V/f-controlled hoist drives.