DE-102025121783-A1 - ENGINE DRIVE SYSTEM AND METHOD FOR CONTROLLING THE SAME

DE102025121783A1DE 102025121783 A1DE102025121783 A1DE 102025121783A1DE-102025121783-A1

Abstract

A motor drive system and a method for controlling it are presented. The motor drive system comprises a motor with a plurality of windings, a first inverter with a plurality of branches, each connected to one end of each of the plurality of windings, a second inverter with a plurality of branches, each connected to the other end of each of the plurality of windings, and a controller configured to control the phase voltages of the motor based on a current command according to a required motor torque and a current limit preset according to the current specifications of the second inverter when a preset ultra-low speed condition is met.

Inventors

Joon Ha HWANG
HEE WON AN
Seong Min Kim
Ho Sun JANG

Assignees

HYUNDAI MOTOR COMPANY
KIA CORPORATION

Dates

Publication Date: 20260513
Application Date: 20250604
Priority Date: 20241113

Claims (20)

Motor drive system comprising: a motor with a plurality of windings; a first inverter comprising a plurality of branches, each connected to a first end of each of the plurality of windings; a second inverter comprising a plurality of branches, each connected to a second end of each of the plurality of windings; and a control unit configured to control the motor's phase voltages based on a current command according to a required motor torque and a current limit preset according to the current specifications of the second inverter, based on the fulfillment of a preset ultra-low-speed condition.
Motor drive system according to Claim 1 , whereby the control unit determines that the ultra-low speed condition is met, based on an engine speed that is equal to or less than a preset reference speed.
Motor drive system according to Claim 1 , wherein the control determines that the ultra-low speed condition is met, based on the drive of the motor, which is controlled by a compensated torque command, which is obtained by compensating a torque command according to the required torque of the motor based on an electrical frequency and a rotor position of the motor.
Motor drive system according to Claim 1 , where the current limit is preset based on the current specifications of each switching element connected to each of the multiple branches of the second inverter.
Motor drive system according to Claim 4 , wherein the control unit determines a current limit value by referring to a current limit map in which current limits are pre-stored according to the required torque and speed of the motor.
Motor drive system according to Claim 1 , whereby the control unit controls the phase voltages based on the current limit, based on a value of the current command that exceeds the current limit.
Motor drive system according to Claim 1 , in which the control unit controls the phase voltages based on the current setpoint, where the current setpoint value is smaller than the current limit value.
Motor drive system according to Claim 1 , whereby the control unit regulates the phase voltages based on the current setpoint if the ultra-slow speed condition is not met.
Motor drive system according to Claim 1 , furthermore with a plurality of switches, wherein one end of each switch is connected to the other end of each of the plurality of windings and the other ends of the switches are connected to each other to form a node, wherein the control unit controls a drive mode of the motor to switch to a first drive mode in which the motor is driven only using the first inverter or to a second drive mode in which the motor is driven using the first inverter and the second inverter by turning the plurality of switches on/off.
Motor drive system according to Claim 9 , whereby the control unit controls the phase voltages of the motor based on the current setpoint and the current limit, based on the fact that the ultra-low speed condition is met, while the drive mode of the motor is the second drive mode.
A method for controlling a motor drive system comprising a motor with a plurality of windings, a first inverter with a plurality of branches, each connected to a first end of each of the plurality of windings, and a second inverter with a plurality of branches, each connected to a different end of each of the plurality of windings, wherein the method includes: determining whether a preset ultra-low speed condition is met; and controlling the phase voltages of the motor based on a current setpoint corresponding to a required torque of the motor and a current limit preset according to the current specifications of the second inverter when the preset ultra-low speed condition is met.
Procedure according to Claim 11 , where determining includes determining that the ultra-low rotational speed condition is met, based on a rotational speed of the motor that is equal to or less than a preset reference speed.
Procedure according to Claim 11 , where determining includes determining that the ultra-low velocity condition is satisfied, based on the fact that the drive of the motor is controlled by a compensated torque command, which is obtained by compensating a torque command according to the required torque of the motor based on an electrical frequency and a rotor position of the motor.
Procedure according to Claim 11 , where the current limit is preset based on current specifications of each switching element connected to each of the multiple branches of the second inverter.
Procedure according to Claim 14 , which further includes the determination of a current limit value by reference to a current limit table in which current limits are stored in advance according to the required torque and speed of the motor.
Procedure according to Claim 11 , wherein the control includes the control of the phase voltages based on the current limit, based on a value of the current command that exceeds the current limit.
Procedure according to Claim 11 , where the control includes the control of the phase voltages based on the current setpoint, which is below the current limit.
Procedure according to Claim 11 , whereby the regulation includes the control of the phase voltages based on the current command, which is based on the fact that the ultra-slow speed condition is not met.
Procedure according to Claim 11 , wherein the motor drive system further comprises a plurality of switches, one end of each switch being connected to the other end of each of the plurality of windings and the other ends of the switches being connected to each other to form a node, wherein the method further comprises controlling a drive mode of the motor to switch into a first drive mode in which the motor is driven only using the first inverter or into a second drive mode in which the motor is driven using both the first inverter and the second inverter by turning the plurality of switches on and off.
Procedure according to Claim 19 , where the control includes controlling the phase voltages of the motor based on the current command and the current limit, based on the fact that the ultra-low speed condition is met, while the drive mode of the motor is the second drive mode.

Description

BACKGROUND 1. Area The present disclosure relates to a motor drive system capable of preventing damage to an inverter in an ultra-low speed range, and to a method for controlling the same. 2. Description of the state of the art Generally, one end of each winding of the phases of a motor is connected to an inverter, and the other ends of the windings are connected to form a Y-connection. When the motor is driven, a switching element in the inverter is switched on and off by pulse width modulation and applies a mains voltage to the Y-connected windings of the motor to generate alternating current, thereby creating a torque. The fuel efficiency (or power efficiency) of an environmentally friendly vehicle, such as an electric vehicle that uses the torque generated by such a motor as power, is determined by the power conversion efficiency of the inverter motor, and therefore it is important to maximize the power conversion efficiency of the inverter and the efficiency of the motor to improve fuel efficiency. The efficiency of an inverter-motor system is mainly determined by the voltage utilization rate of the inverter, and if an operating point of a vehicle, which is determined by the ratio between the engine speed and the torque, is formed in a range where the voltage utilization rate is high, the fuel consumption of the vehicle can be improved. However, as the number of motor winding loops increases to raise the motor's maximum torque, the high-voltage load range moves further and further away from the low-torque range, the vehicle's main operating point, and fuel efficiency can therefore decrease. If the main operating point is designed to fall within the high-voltage load range for fuel efficiency purposes, the motor's maximum torque is limited, which can reduce the vehicle's acceleration and starting performance. Since a motor drive technology is required that improves the efficiency of the system and simultaneously covers both the low and high power ranges with one motor, a technology for driving a single motor in two different modes using two inverters and a mode switch was introduced. The facts described above as background technology serve only to provide a better understanding of the background of the present disclosure and should not be considered to be in accordance with the prior art, which is already known to those skilled in the art. SUMMARY The present disclosure provides a motor drive system and a method for controlling the same, which can prevent damage to an inverter in a very low speed range. The objective to be achieved in the present disclosure is not limited to the objective mentioned above, and other, unmentioned objectives will be clearly understood by those skilled in the field to which the present disclosure belongs, based on the description below. According to one aspect of the present disclosure, the above and other objectives can be achieved by providing a motor drive system comprising a motor with a plurality of windings, a first inverter with a plurality of branches, each connected to one end of each of the plurality of windings, a second inverter with a plurality of branches, each connected to another end of each of the plurality of windings, and a controller configured to control the phase voltages of the motor based on a current command according to a required torque of the motor and a current limit preset according to the current specifications of the second inverter when a preset ultra-low-speed condition is met. According to another aspect of the present disclosure, a method for controlling a motor drive system is provided, comprising a motor, a plurality of windings, a first inverter with a plurality of branches, each connected to one end of each of the plurality of windings, and a second The inverter comprises a plurality of branches, each connected to a different end of each of the plurality of windings, wherein the method includes determining whether a preset ultra-low-speed condition is met and controlling the phase voltages of the motor based on a current command according to a required torque of the motor and a current limit preset according to the current specifications of the second inverter when the preset ultra-low-speed condition is met. BRIEF DESCRIPTION OF THE DRAWINGS The above and other tasks, features and other advantages of the present disclosure will be more clearly understood from the following detailed description in conjunction with the accompanying drawings, in which: 1 a circuit diagram of a motor drive system according to an embodiment of the present disclosure; 2 a diagram illustrating the switching of a motor drive mode according to an embodiment of the present disclosure; 3 a diagram illustrating a control process of a controller according to an embodiment of the present disclosure; and 4 a flowchart illustrating a method for controlling the motor drive system according to an embodiment of the present disclosure. DETAILED DESCRIPTION Specific stru