US-12620918-B2 - Method and device for controlling three-phase motor

US12620918B2US 12620918 B2US12620918 B2US 12620918B2US-12620918-B2

Abstract

A device and a method control a motor using a maximum torque per ampere field module and a direct flux vector control module. The method: determines by the direct flux vector control module reference voltages in a fτ framework; drives the motor with the summed voltages; measures a motor current vector; determines a high frequency injection voltage so that the high frequency current response of the motor to the high frequency injection voltages is perpendicular to the measured motor current vector; determines an estimated flux from the measured motor currents and the voltage references; and determines, from the estimated flux and the high frequency sinewave signal, the reference flux so that the high frequency flux response to the injected voltage is aligned with the measured current vector.

Inventors

Guilherme BUENO MARIANI
Nicolas Voyer
Gianmario Pellegrino
Anantaram VARATHARAJAN

Assignees

MITSUBISHI ELECTRIC CORPORATION

Dates

Publication Date: 20260505
Application Date: 20220601
Priority Date: 20210713

Claims (7)

1 . A method for controlling a motor using a maximum torque per ampere field module and a direct flux vector control module, characterized in that the method comprises: determining by the direct flux vector control module reference voltages in a fτ framework from an estimated flux norm, a reference flux, a measured current motor vector in a fτ framework using an estimated load angle and a reference current in a t axis that is obtained from a reference torque and the reference flux, summing the reference voltages transformed in a stator αβ framework with a high frequency injection voltage, driving the motor with the summed voltages, measuring a motor current vector, determining the high frequency injection voltage from the measured motor current vector and a high frequency sinewave signal, so that the high frequency current response of the motor to the high frequency injection voltages is perpendicular to the measured motor current vector, determining an estimated flux from the measured motor currents and the voltage references, determining, by the maximum torque per ampere field module, from the estimated flux and the high frequency sinewave signal, the reference flux to be provided to the direct flux vector control module so that the high frequency flux response to the injected voltage is aligned with the measured current vector.
2 . A device for controlling a three-phase motor using a maximum torque per ampere field module and a direct flux vector control module, characterized in that the device comprises circuitry for: determining by the direct flux vector control module reference voltages in a fτ framework from an estimated flux norm, a reference flux, a measured current motor vector in a fτ framework using an estimated load angle and a reference current in a t axis that is obtained from a reference torque and the reference flux, summing the reference voltages transformed in a stator αβ framework with a high frequency injection voltage, driving the motor with the summed voltages, measuring a motor current vector, determining the high frequency injection voltage from the measured motor current vector and a high frequency sinewave signal, so that the high frequency current response of the motor to the high frequency voltage is perpendicular to the measured motor current vector, determining an estimated flux from the measured motor currents and the voltage references, determining, by the maximum torque per ampere field module, from the estimated flux and the high frequency sinewave signal, the reference flux to be provided to the direct flux vector control module so that the high frequency flux response to the injected voltage is aligned with the measured current vector.
3 . The device according to claim 2 , characterized in that the circuitry for determining the high frequency injection voltage comprises circuitry for: determining a fundamental current vector, transforming the current vector measured in the stator framework into a current vector in a current framework aligned with the determined fundamental current vector, determining a filtered current vector by high frequency filtering of the current vector, subtracting a high frequency sinewave signal in the j axis of the current framework to the filtered current vector and for performing a proportional integral regulation in order to obtain a voltage injection signal in the current framework, transforming the voltage injection signal in the current framework into the high frequency voltage in the stator framework.
4 . The device according to claim 2 , characterized in that the maximum torque per ampere module comprises circuitry for: performing a heterodyne modulation of the estimated flux in a j axis and for performing a proportional integral regulation of the heterodyne demodulation result in order to provide the reference flux.
5 . The device according to claim 2 , characterized in that the direct flux vector control module comprises circuitry for: subtracting from the reference current in the t axis, the measured current i τ in the t axis and performing a first proportional integral regulation of the result of the subtraction, subtracting from the reference flux, the estimated flux norm, and performing a second proportional integral regulation of the result of the subtraction, executing a first summing of the results of the proportional integral regulations, summing the result of the first summing by a first value that is dependent of a stator resistance of the motor, an estimated motor speed and the reference current in the τ axis, executing a second summing of the result of the second proportional integral regulation to a second value that is dependent of the stator resistance of the motor and the reference current in a f axis.
6 . The device according to claim 2 , characterized in that the circuitry for determining the estimated flux comprise circuitry for: subtracting from a reference voltage in a α axis the motor currents in the α axis multiplied by the stator resistance, subtracting from the result of the subtracting of the reference voltage in the α axis of the current in the α axis multiplied by the stator resistance an estimated flux in the α axis by a coefficient and performing a third proportional integral regulation of the result of the subtraction in order to obtain the estimated flux in the α axis, subtracting from a reference voltage in the β axis the current in the β axis multiplied by the stator resistance, subtracting from the result of the subtraction of the reference voltage in the β axis of the current in the β axis multiplied by the stator resistance an estimated flux in the β axis by the coefficient and performing a fourth proportional integral regulation of the result of the subtraction in order to obtain the estimated flux in the β axis.
7 . The device according to claim 6 , characterized in that the flux estimation module further comprises circuitry for: dividing the estimated flux in the β axis by the estimated flux in the α axis in order to provide an estimated tangent of the load angle.

Description

TECHNICAL FIELD The present invention relates generally to a method and a device for controlling a three-phase motor. BACKGROUND ART Electrical machines are widely used on the industry either for factory automation or transportation. Many control techniques for machines as Permanent Magnet Synchronous Machines (PMSM), Synchronous Reluctance Machines (SyncRM), Wounded Rotor Synchronous Machines (WRSM) often use a rotary encoder for obtaining the speed and the position of the machine as feedback. The demand for low-cost and robust motor drives has increased the development of sensorless control. Without those sensors the machine drives become less expensive and more robust to dusty and harsh environments. Many techniques for sensorless control are proposed. These techniques are based on the estimation of the position and the speed of the machine but one aspect that is often neglected on the sensorless controller is the strategy for choosing the current references of the FOC (Field-Oriented Control) controller from a given desired torque reference. In CVC controllers (Current Vector Control), the reference quantities are the current levels in dq axis, in the rotor reference frame, which position has to be estimated. In DFVC (Direct Flux Vector Control), the reference quantities are the norm of flux and one current component. The latter technique is attracting, as it also applies to the stator flux reference frame, which needs no position estimate. Best current trajectory is the MTPA (Maximum Torque per Ampere), which chooses the combination of references in order to maximise the torque for a given current level (and given copper losses). In the bibliography, different techniques to track the MTPA are proposed using one or more Lookup Tables (LUTs) or injection based. With lookup tables, the torque is measured as function of Idq current in order to derive the ideal MTPA trajectory. This trajectory can be stored and used dynamically with varying torque levels. However specific measurement is needed prior to operating MTPA mode. This is the most common way to track MTPA trajectory. These methods have serious limitations. It is generally difficult for a General-Purpose Inverter (GPI) to establish a lookup table of MTPA for an unknown motor. The alternative to the direct measurement of the MTPA LUTs is the manipulation of the flux linkage or inductance map LUTs, which again requires dedicated tests or a self-commissioning session. For CVC controllers, MTPA expression requires the knowledge of incremental and chord inductances in both d and q axis. Generally, MTPA control tends to require the knowledge of inductance LUTs. Uncertainty in inductances results in position error and risk of instability and deviation from MTPA, which causes misuse of energy besides the possible loss of control. Techniques for tracking the MTPA and MTPV for DFVC controller are proposed in the bibliography. However, they rely on measured inductances LUT, for the MTPA tracking. Injection methods to track the MTPA online were already proposed in the bibliography, but they are commonly used for CVC controllers and not applicable for DFVC controllers. SUMMARY OF INVENTION The present invention aims to provide a sensorless control method and device using DFVC control technique and reaches MTPA optimal operation conditions without any prior information on the motor to be controlled. To that end, the present invention concerns a method for controlling a motor using a maximum torque per ampere field module and a direct flux vector control module, characterized in that the method comprises the steps of: determining by the direct flux vector control module reference voltages in a ft framework from an estimated flux {circumflex over (λ)} norm, a reference flux λM⁢T⁢P⁢A*, a measured current motor vector ifτ in in a fτ framework using an estimated load angle {circumflex over (δ)}s and a reference current iτ* in a τ axis that is obtained from a reference torque T* and the reference flux λMTPA*,summing the reference voltages transformed in a αβ stator framework v*αβ with a high frequency injection voltage vαβinj driving the motor with the summed voltages,measuring a motor current vector iαβ,determining the high frequency injection voltage vαβinj from the measured motor current vector iαβ and a high frequency sinewave signal iδ sin(ωht), so that the high frequency current response of the motor to the high frequency injection voltage is perpendicular to the measured motor current vector,determining an estimated flux {circumflex over (λ)}αβ from the measured motor currents iαβ and the voltage references v*αβ,determining, by the maximum torque per ampere field module, from the estimated flux {circumflex over (λ)}αβ and the high frequency sinewave signal sin(ωht), the reference flux λMTPA* to be provided to the direct flux vector control module so that the high frequency flux response to the injected voltage is aligned with the measured motor current vector. T