# US 11,309,818 B2 · Motor variable frequency driving system and multi-split central air conditioner

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- Number: US 11,309,818 B2
- Document ID: US11309818B2
- Status: Granted
- Kind: B2
- Application number: 17/172,024
- Filed: 2021-02-09
- Published: 2021-06-03
- Granted: 2022-04-19
- Earliest claimed: 2018-08-20
- Assignees: Gd Midea Heating & Ventilating Equipment Co., Ltd.; Midea Group Co., Ltd.
- Applicants: GD Midea Heating & Ventilating Equipment Co., Ltd.; Midea Group Co., Ltd.
- Inventors: Chao Zhou; Takeshi Kokura; Xiong Qian
- Web page: https://patentgrep.com/patent/US11309818B2

## CPC

- H02P 6/10: Arrangements for controlling torque ripple, e.g. providing reduced torque ripple
- H02P 21/22: Current control, e.g. using a current control loop
- H02P 21/05: specially adapted for damping motor oscillations, e.g. for reducing hunting
- H02P 21/18: Estimation of position or speed
- H02P 27/08: with pulse width modulation
- H02P 29/50: Reduction of harmonics
- H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS

## Abstract

Disclosed are a motor variable frequency driving system and a multi-split central air conditioner. The motor variable frequency driving system includes: a three-phase alternating-current input, a rectification module, a thin-film capacitor, an inverter, a vector control module, an A/D sampling module and a steady state processing module. The rectification module is connected to the three-phase alternating-current input; the thin-film capacitor is arranged between output ends of a direct current output; an input end of the inverter is connected to an output end of the direct current output; an output end of the inverter is connected to a three-phase alternating current motor; the vector control module is connected to the inverter; the A/D sampling module is used for collecting direct current bus voltages of two ends of the thin-film capacitor; and the steady state processing module is connected to the A/D sampling module.

## Claims

### Claim 1

A motor variable frequency driving system, comprising:
a three-phase alternating-current input;
a rectification module connected to the three-phase alternating-current input and used for converting the three-phase alternating-current input into a direct current output;
a thin-film capacitor arranged between output ends of the direct current output;
an inverter, with an input end of the inverter connected to the output end of the direct current output and an output end of the inverter connected to a three-phase alternating current motor;
a vector control module connected to the inverter and used for generating a control instruction for controlling the inverter;
an A/D sampling module used for collecting direct current bus voltages of two ends of the thin-film capacitor; and
a steady state processing module connected to the A/D sampling module and used for carrying out steady state processing on the direct current bus voltage and outputting a compensation parameter to the vector control module, wherein
the vector control module further comprises: an SVPWM unit used for outputting a control instruction to the inverter; and
the steady state processing module further comprises: a high-frequency component processing unit, with one end of the high-frequency component processing unit connected to the A/D sampling module and the other end of the high-frequency component processing unit connected to the SVPWM unit, used for correcting the control instruction output by the SVPWM unit, and wherein the high-frequency component processing unit is configured to extract and reprocess a high-frequency component of the direct current bus voltage.

### Claim 2 (depends on 1)

The motor variable frequency driving system according to claim 1, wherein the steady state processing module comprises:
a low-pass filter with one end of the low-pass filter connected to the A/D sampling module, used for low-pass filtering the direct current bus voltage;
a high-pass filter arranged in parallel with the low-pass filter, with one end of the high-pass filter connected to the A/D sampling module, used for high-pass filtering the direct current bus voltage; and
a torque instruction correction unit respectively connected with the other end of the low-pass filter and the other end of the high-pass filter, used for outputting a compensation instruction.

### Claim 3 (depends on 1)

The motor variable frequency driving system according to claim 1, wherein the vector control module comprises:
a rotation speed estimation unit used for estimating a rotation speed of the motor according to input voltage and current and determining the rotation speed as a feedback rotation speed instruction; and
a rotation speed regulator used for converting a difference between a rotation speed control instruction to the motor and the feedback rotation speed instruction into an initial instruction so as to generate an adjustment instruction according to the initial instruction and the compensation instruction.

### Claim 4 (depends on 3)

The motor variable frequency driving system according to claim 3, wherein the vector control module further comprises:
a Clarke coordinate conversion unit used for converting input three-phase currents Ia, Ib and Ic under a three-phase static coordinate system into currents Iα_fbk and Iβ_fbk a two-phase static coordinate system; and
a Park coordinate conversion unit used for converting Iα_fbk and Iβ_fbk under the two-phase static coordinate system into feedback currents Id_fbk and Iq_fbk under a two-phase rotation coordinate system.

### Claim 5 (depends on 4)

The motor variable frequency driving system according to claim 4, wherein when the three-phase alternating current motor is a permanent magnet synchronous motor,
the rotation speed estimation unit is a first rotation speed estimation unit, and an input end of the first rotation speed estimation unit is used for receiving collected Id, Iq, Ud and Uq of the motor and outputting an estimated rotation speed according to Id, Iq, Ud and Uq of the motor, thus determining the estimated rotation speed as the feedback rotation speed instruction.

### Claim 6 (depends on 4)

The motor variable frequency driving system according to claim 4, wherein the vector control module further comprises:
an integration unit used for converting the feedback rotation speed instruction into an angle instruction and inputting the angle instruction to the Park coordinate conversion unit.

### Claim 7 (depends on 5)

The motor variable frequency driving system according to claim 5, wherein the compensation instruction is a torque compensation instruction while the initial instruction is a torque initial instruction to determine the adjustment instruction as a torque control instruction, and the vector control module further comprises:
a maximum torque per Ampere unit, with an input end of the maximum torque per Ampere unit used for inputting the torque control instruction and an output end of the maximum torque per Ampere unit used for outputting torque current control instructions Id_ref and Iq_ref under the two-phase rotation coordinate system.

### Claim 8 (depends on 7)

The motor variable frequency driving system according to claim 7, wherein the vector control module further comprises:
a current regulator, an input end of the current regulator respectively inputting a difference value between Id_ref and Id_fbk and a difference value between Iq_ref and Iq_fbk, an output end of the current regulator being used for outputting control voltages Vd and Vq to the SVPWM unit.

### Claim 9 (depends on 4)

The motor variable frequency driving system according to claim 4, wherein when the three-phase alternating current motor is an alternating current asynchronous motor,
the rotation speed estimation unit is a second rotation speed estimation unit, and an input end of the second rotation speed estimation unit is used for receiving collected Iα, Iβ, Uα and Uβ of the motor and outputting an estimated rotation speed according Iα, Iβ, Uα and Uβ of the motor, thus determining a sum of the estimated rotation speed and a spin differential rotation speed as the feedback rotation speed instruction.

### Claim 10 (depends on 9)

The motor variable frequency driving system according to claim 9, wherein the compensation instruction is a torque current compensation instruction while the initial instruction is a torque current initial instruction to determine the adjustment instruction as a torque current control instruction Id_ref and Iq_ref.

### Claim 11 (depends on 1)

A multi-split central air conditioner, comprising:
the motor variable frequency driving system according to claim 1.