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DE-102020126208-B4 - ELECTRIC DRIVE SYSTEM

DE102020126208B4DE 102020126208 B4DE102020126208 B4DE 102020126208B4DE-102020126208-B4

Abstract

Electric drive system (15), comprising: a voltage bus with a positive bus rail (19+) and a negative bus rail (19-) and a DC bus voltage across the bus rails (19+, 19-); a battery pack (20) that is connected between the positive bus rail (19+) and the negative bus rail (19-) of the voltage bus and supplies a battery voltage (V bat + , V bat - ); a DC/DC converter (30) comprising a set of semiconductor switches (34) connected between the positive bus rail (19+) and the negative bus rail (19-) and having a bypass switch (S0, 32) connected to the positive bus rail (19+), wherein the DC/DC converter (30) is configured as a buck/boost converter; a traction power inverter module (40), TPIM (40), with a DC side connected to the DC-DC converter (30) at an inverter bus voltage (31+, 31-) and with an AC side, AC, wherein the TPIM (40) is configured to direct the inverter bus voltage (31+, 31-) and thereby generate an AC bus voltage at phase lines (48); a rotating electric machine (16) connected to the AC side of the TPIM (40) and powered via the AC bus voltage; and a controller (50) configured to calculate a required output power of the DC-DC converter (30) based on a requested operating mode, a target speed (N 16 ) and a target torque (T 16 ) of the electric machine (16) in order to compare the required output power with a calibrated power threshold, and: if the required output power exceeds the calibrated power threshold, close the bypass switch (S0, 32) and thereby bypass the DC-DC converter (30); and if the required output power is less than the calibrated power threshold, to determine a minimum loss voltage (V MIN-L ) from a loss map (52) and then to use the minimum loss voltage (V MIN-L ) as a target control voltage of the DC-DC converter (30) in order to optimize the efficiency of the electric drive system (15) with the bypass switch (S0, 32) open; where the bypass switch (S0, 32) is a mechanical relay or bidirectional semiconductor switch.

Inventors

  • Lei Hao
  • Chandra S. Namuduri
  • Suresh Gopalakrishnan
  • Chengwu Duan
  • Norman K. Bucknor

Assignees

  • GM Global Technology Operations LLC

Dates

Publication Date
20260513
Application Date
20201007
Priority Date
20191106

Claims (9)

  1. Electric drive system (15), comprising: a voltage bus with a positive bus rail (19+) and a negative bus rail (19-) and a DC bus voltage across the bus rails (19+, 19-); a battery pack (20) connected between the positive bus rail (19+) and the negative bus rail (19-) of the voltage bus and supplying a battery voltage (V bat + , V bat- ); a DC/DC converter (30), DC-DC converter (30) comprising a set of semiconductor switches (34) connected between the positive bus rail (19+) and the negative bus rail (19-), and a bypass switch (S0, 32) which is connected to the positive bus rail (19+), wherein the DC-DC converter (30) is configured as a buck/boost converter; a traction power inverter module (40), TPIM (40), having a DC side connected to the DC-DC converter (30) at an inverter bus voltage (31+, 31-), and an AC side, AC, wherein the TPIM (40) is configured to rectify the inverter bus voltage (31+, 31-) and thereby generate an AC bus voltage at phase lines (48); a rotating electric machine (16) connected to the AC side of the TPIM (40) and supplied via the AC bus voltage; and a controller (50) configured to calculate a required output power of the DC-DC converter (30) based on a requested operating mode, a target speed (N 16 ) and a target torque (T 16 ) of the electric machine (16) in order to compare the required output power with a calibrated power threshold, and: if the required output power exceeds the calibrated power threshold, to close the bypass switch (S0, 32) and thereby bypass the DC-DC converter (30); and if the required output power is less than the calibrated power threshold, to determine a minimum loss voltage (V MIN-L ) from a loss map (52) and then to use the minimum loss voltage (V MIN-L ) as a target control voltage of the DC-DC converter (30) in order to optimize the efficiency of the electric drive system (15), wherein the bypass switch (S0, 32) is open; wherein the bypass switch (S0, 32) is a mechanical relay or bidirectional semiconductor switch.
  2. Electric drive system (15) according to Claim 1 , where the controller (50) is configured, d-axis and q-axis commands ( i d * , i q * ) to generate control of the TPIM (40) and the electric machine (16) on the basis of the target torque, target speed and minimum loss voltage (V MIN-L ).
  3. Electric drive system (15) according to Claim 1 , wherein the controller (50) is configured to transmit pulse width modulation control signals, PWM control signals, to the pair of semiconductor switches (34) of the DC-DC converter (30) in order to balance the DC bus voltage with the battery voltage (V bat +, V bat - ) before opening or closing the bypass switch (S0, 32).
  4. Electric drive system (15) according to Claim 1 , wherein the semiconductor switches (34) in the DC-DC converter (30) are bidirectional gallium nitride or silicon carbide switches.
  5. Electric drive system (15) according to Claim 1 , wherein the loss map (52) contains a lookup table filled with calibrated loss values for each of a plurality of output voltages of the DC-DC converter (30), and wherein the minimum loss voltage (V MIN-L ) is one of the selected output voltages which has the smallest magnitude among the calibrated loss values.
  6. Electric drive system (15) according to Claim 1 , wherein the controller (50) contains a control logic with a first control loop (L1) in which the controller (50) controls the operation of the DC-DC converter (30) via the minimum loss voltage (V MIN-L ) and a second control loop (L2) in which the controller (50) controls the operation of the TPIM (40) via a proportional-integral current controller.
  7. Electric drive system (15) according to Claim 1 , wherein the DC-DC converter (30) is configured as a buck/boost converter or as a boost converter and the controller (50) is configured to increase the inverter bus voltage (31+, 31-) to the minimum loss voltage (V MIN-L ) when the operating mode is motor mode, the target speed is above a speed threshold and the required output power is less than the calibrated power threshold.
  8. Electric drive system (15) according to Claim 7 , wherein in a regeneration mode the controller (50) is configured to raise the inverter bus voltage (31+, 31-) to the battery voltage (V bat + , V bat - ) when the target speed is below a speed threshold and the required output power is less than a calibrated power threshold.
  9. Electric drive system (15) according to Claim 1 , wherein the DC-DC converter (30) is configured as a buck/boost converter or as a buck converter and in driving operation the controller (50) is configured to reduce the inverter bus voltage (31+, 31-) to the minimum loss voltage (V MIN-L ) when the target speed is below a speed threshold and the required output torque is less than a torque threshold.

Description

Electric drive systems rely on torque generated by one or more rotating electric machines and transmitted to a coupled load. Electric machines are often configured as multiphase alternating current (AC) devices powered by a DC bus and a battery pack. A power converter module is therefore used as part of the electric drive system to either invert or rectify an input voltage, with the operation performed by the power converter module depending on the specific operating mode. During regenerative operation, for example, the control of the ON/OFF states of individual inverter switches located within the inverter module is used to rectify an AC input voltage from the electric machine when operating as a generator, with the inverter module producing a DC output voltage. This DC output voltage is then used to recharge the individual battery cells of the aforementioned battery pack. The control of the same inverter switches during drive/motor operation is used to invert an input DC voltage from the DC bus/battery pack, thereby providing an AC output voltage suitable for powering the electric machine. Additionally, the voltage level on the DC bus can be regulated with a DC-DC converter. Such a device contains another group of semiconductor switches whose ON/OFF line states are controlled in response to a DC input voltage to achieve a required DC output voltage. Electric drive systems can operate at relatively low torque/power levels for a significant portion of a drive cycle, for example, in electric vehicle applications. A miniaturized DC/DC converter is therefore a viable hardware option for such applications, with one such approach being described, for example, in United States Patent No. US 10 110 103 B1 according to Hao et al., which is hereby incorporated in its entirety by reference. While the torque characteristics in the upper speed range are sacrificed to some extent as a result of using such a miniaturized converter, the reduced torque characteristics have the associated advantage of improving the overall efficiency of the electric drive system. The DE 11 2009 000 549 T5 This describes an electric motor control device. The electric motor control device comprises a power conversion device for generating an alternating voltage via a switching actuator of a power semiconductor device, an electric motor with a coil winding to which the alternating voltage from the power conversion device is applied, and a control device for controlling the switching actuator of the power conversion device. The control device controls the switching actuator of the power conversion device such that the voltage change rate during the reversal of the polarity of the alternating voltage is relatively low when the alternating voltage exceeds a predetermined value. The DE 10 2015 102 410 A1 This document describes a traction battery module for supplying energy to a traction inverter for an electric drive motor of a vehicle, comprising at least one battery module and a battery module inverter connected to the battery module to provide a supply voltage for the traction inverter. Furthermore, an electric powertrain for a vehicle and a method for supplying energy to a traction inverter for an electric drive motor of a vehicle using a traction battery module comprising at least one battery module are disclosed, wherein a battery module inverter is connected to the battery module to provide a supply voltage for the traction inverter. The DE 10 2018 114 740 A1 This describes an electric drive system. The drive system includes bus rails carrying a voltage, an energy storage system, and an inverter. The system includes a voltage converter connected to the bus rails, comprising an inductor, semiconductor switches, a bypass switch connected to a positive rail, and a capacitor. A multiphase electric machine is electrically connected to the inverter. A controller executes a procedure in which the operation of the converter is regulated based on the power, torque, and speed values of the electric machine. The converter is selectively bypassed by closing the bypass switch under predetermined high-power/high-torque conditions, adjusting the bus voltage until it equals the battery output voltage. The bypass circuit is then opened, and the bus voltage is subsequently regulated to a predetermined voltage. The US 10 110 103 B1 describes an electric drive system. The drive system includes The system consists of bus lines carrying a bus voltage, an energy storage system, and a power inverter. It includes a voltage converter connected to the bus lines, an inductor, semiconductor switches, a bypass switch connected to a positive bus line, and a capacitor. A multiphase electric machine is electrically connected to the power inverter. A controller performs a procedure in which the operation of the converter is regulated based on the power, torque, and speed values of the electric machine. The converter is selectively bypassed by closing the bypass switch unde