Alternating current and direct current motor fusion feedback energy recycling system and control method

Abstract

The invention discloses an alternating current and direct current motor fusion feedback energy recycling system which comprises a circuit breaker Q1, a circuit breaker Q2, a transformer T1 and an AFE rectifier cabinet, the circuit breaker Q1, the circuit breaker Q2, the transformer T1 and the AFE rectifier cabinet are sequentially connected in series through a first wire, and the AFE rectifier cabinet is connected with an inverter unit, a power supply unit and a brake unit in parallel through a direct current bus. The invention further discloses an energy feedback control method, the control unit monitors a direct current bus voltage value, judges the type of a test motor and determines the working states of the AFE rectifier cabinet, the first inverter cabinet INV, the second inverter cabinet INV, the DC / DC conversion cabinet, the DC / DC excitation cabinet and the brake unit, and feedback energy cyclic utilization control is completed. According to the direct current motor fusion feedback energy recycling system and the control method, the total power absorbed from the power grid is only 20%-30% of the load power by adopting the alternating current and direct current motor fusion design, and all energy does not need to be obtained from the power grid.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor testing and measurement, and particularly relates to an AC-DC motor integrated feedback energy recycling system. The present invention also relates to a control method for energy feedback using the AC-DC motor integrated feedback energy recycling system. Background Art

[0002] Currently, when a motor undergoes a load test during factory production, the load of the motor under test is mostly simulated and applied using a dynamometer, a DC generator, a power resistor, a mechanical braking device, etc. The motor under test needs to obtain all the energy from the power grid. Since there is no actual load, this part of the energy needs to be discharged into the surrounding environment in the form of heat. The total power of the entire device is high, the transformer capacity is large, the equipment procurement cost is high, and substantial connection and capacity expansion fees need to be paid. During the test, motors with hundreds or thousands of kilowatts need to draw full power from the power grid, resulting in high test operation energy consumption and costs. Moreover, the AC-DC motor system is generally built independently. Summary of the Invention

[0003] The object of the present invention is to provide an AC-DC motor integrated feedback energy recycling system, which solves the problem in the prior art that the motor under test needs to obtain all the energy from the power grid due to the absence of an actual load.

[0004] Another object of the present invention is to provide a control method for energy feedback.

[0005] The technical solution adopted by the present invention is that the AC-DC motor integrated feedback energy recycling system includes a circuit breaker Q1, a circuit breaker Q2, a transformer T1, and an AFE rectifier cabinet. The circuit breaker Q1, the circuit breaker Q2, the transformer T1, and the AFE rectifier cabinet are connected in series in sequence through a first wire. The AFE rectifier cabinet is connected in parallel with an inverter unit, a power supply unit, and a braking unit through a DC bus. The AFE rectifier cabinet, the inverter unit, the power supply unit, and the braking unit are respectively connected to a control unit through a second wire. The inverter unit is connected to an AC auxiliary test motor M1 and an AC test motor M2 respectively through an AC bus. The power supply unit is connected to a DC test motor M3 and a DC excitation power supply respectively through a DC bus. The braking unit is connected to a braking resistor BR through a DC bus.

[0006] The characteristics of the present invention also lie in that:

[0007] The inverter unit includes a first inverter cabinet INV and a second inverter cabinet INV. The first inverter cabinet INV is connected to the AC auxiliary test motor M1 through an AC bus, and the second inverter cabinet is connected to the AC test motor M2 through an AC bus.

[0008] The power supply unit includes a DC / DC conversion cabinet and a DC / DC excitation cabinet. The DC / DC conversion cabinet is connected to the DC test motor M3 through a DC bus, and the DC / DC excitation cabinet is connected to the DC excitation power supply through a DC bus.

[0009] The first inverter cabinet INV and the second inverter cabinet INV are respectively connected to the control unit through the second wire. The power supply unit includes a DC / DC conversion cabinet and a DC / DC excitation cabinet, which are respectively connected to the control unit through the second wire.

[0010] The AC test motor M1 and the AC test motor M2 or the DC test motor M3 are flange-connected with a torque sensor.

[0011] Another technical solution adopted by the present invention is a control method for energy feedback, which uses the above AC-DC motor integrated feedback energy recycling system. The specific steps are as follows:

[0012] The control unit monitors the DC bus voltage value and judges the type of the test motor; determines the working states of the AFE rectifier cabinet, the first inverter cabinet INV, the second inverter cabinet INV, the DC / DC conversion cabinet, the DC / DC excitation cabinet and the braking unit according to the judged type of the test motor and the monitored DC bus voltage value, and completes the control of the feedback energy recycling.

[0013] Another characteristic of the technical solution of the present invention is also:

[0014] Step 1: The control unit monitors the DC bus voltage value and judges the type of the test motor. If it is judged as the AC test motor M2 and the monitored DC bus voltage value is less than 740V, then time for 3S. If the monitored DC bus voltage value is still less than 740V after 3S, then stop the first inverter cabinet INV and the second inverter cabinet INV, and report an under-voltage protection fault;

[0015] If it is judged as the DC test motor M3 and the DC bus voltage value is less than 740V, then time for 3S. If the monitored current bus voltage value is still less than 740V after 3S, then stop the first inverter cabinet INV, the DC / DC conversion cabinet and the DC / DC excitation cabinet, and report an under-voltage protection fault;

[0016] If the monitored DC bus voltage value is not less than 740V after 3S, then judge whether the DC bus voltage value is not less than 1000V. If it is not less than 1000V, the AFE rectifier cabinet feeds back energy to the power grid, and at the same time enters Step 3; if the DC bus voltage value is less than 1000V, then enter Step 2;

[0017] Step 2: If the DC bus voltage value is less than 1000V, the first inverter cabinet INV, the second inverter cabinet INV or the DC / DC conversion cabinet and the DC / DC excitation cabinet work according to the instructions of the control unit. The AC test motor M2 and the DC test motor M3 work in the VF separation or speed control mode through the control unit, and are in the electric state. The AC test motor M1 works in the torque control mode and is in the power generation state, feeding back energy to the DC bus;

[0018] Step 3: If the DC bus voltage value is not less than 1000V, the control unit determines whether the DC bus voltage value is not less than 1158V. If the DC bus voltage value is not less than 1158V, the braking unit and the braking resistor operate, and at the same time, it is determined whether the DC bus voltage value is not less than 1120V, and then Step 4 is entered; if the DC bus voltage value is less than 1158V, the process continues from Step 1.

[0019] Step 4: If the DC bus voltage value is not less than 1220V, time for 3s. If the DC bus voltage value is still not less than 1220V after 3s, stop the first inverter cabinet INV, the second inverter cabinet INV, or the DC / DC conversion cabinet and the DC / DC excitation cabinet, and report an overvoltage protection fault; if the DC bus voltage value is less than 1220V, the process continues from Step 1 to complete the control process of recycling the feedback energy.

[0020] The beneficial effects of the present invention are:

[0021] The AC-DC motor integrated test feedback energy recycling system and control method of the present invention adopt an AC-DC motor integrated design. When the test motor is loaded to 100% of the rated power, due to the energy recycling between the tested motor and the accompanying motor, the transformer capacity can be reduced by 50%, and the equipment cost is reduced by half; the total power absorbed from the power grid is only 20% - 30% of the load power, without obtaining all the energy from the power grid, the equipment operation energy consumption is reduced by 70% - 80%, and the operation cost is significantly reduced. Description of the Drawings

[0022] Figure 1 is a schematic structural diagram of the AC-DC motor integrated feedback energy recycling system of the present invention;

[0023] Figure 2 is a schematic flow diagram of the control method for energy feedback of the present invention. Detailed Embodiments

[0024] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0025] The present invention provides an AC-DC motor integrated test feedback energy recycling system, as Figure 1As shown in the figure, it includes circuit breakers Q1 and Q2, transformer T1, AFE rectifier cabinet, inverter unit, power supply unit and braking unit. Circuit breaker Q1, circuit breaker Q2, transformer T1 and AFE rectifier cabinet are connected in series in turn through the first wire. The AFE rectifier cabinet is connected in parallel with the first inverter cabinet INV, the second inverter cabinet INV, the DC / DC conversion cabinet, the DC / DC excitation cabinet and the braking unit through the DC bus. The braking unit is connected to the braking resistor BR through the DC bus. The AFE rectifier cabinet, the first inverter cabinet INV, the second inverter cabinet INV, the DC / DC conversion cabinet, the DC / DC excitation cabinet and the braking unit are respectively connected to the control unit through the second wire. And the first inverter cabinet INV is connected to the AC test motor M1 through the AC bus, the second inverter cabinet is connected to the AC test motor M2 through the AC bus, the power supply unit is connected to the DC test motor M3 and the DC excitation power supply respectively through the DC bus, and the braking unit is connected to the braking resistor BR through the DC bus. The control unit and the AFE rectifier cabinet, the inverter unit and the power supply unit perform two-way data transmission through Ethernet communication to realize the torque adjustment of the AC test motor M1 and the voltage or speed adjustment of the test motor, so that the test motor outputs the expected power and voltage or frequency.

[0026] As Figure 1As shown in the figure, the transformer T1 boosts the AC 400V to AC 600V. The AFE rectifier cabinet rectifies the AC voltage into a DC voltage to supply power to the inverter unit and the power supply unit. The inverter unit includes the first inverter cabinet INV and the second inverter cabinet INV. The first inverter cabinet INV drives the AC test motor M1 by communicating with the control unit. The control unit monitors the status of the frequency converter in the first inverter cabinet INV. The second inverter cabinet INV drives the AC motor under test M2 by communicating with the control unit. The control unit monitors the status of the frequency converter in the second inverter cabinet INV. The power supply unit includes a DC / DC conversion cabinet and a DC / DC excitation cabinet. The DC / DC conversion cabinet drives the DC test motor M3 by communicating with the control unit. The control unit monitors the status of the converter in the DC / DC conversion cabinet. The DC / DC excitation cabinet supplies excitation or additional power for adding or subtracting feed to the DC test motor M3 by communicating with the control unit. The control unit is the control center of the entire system and has communication and logic judgment functions. It conducts two-way data transmission with the AFE rectifier cabinet, the inverter unit, the power supply unit, and the braking unit through Ethernet communication and two-way data exchange through communication. The control unit sends start / stop and rectification or feedback signals to the AFE rectifier cabinet, and start / stop and speed or torque control signals to the inverter unit, the power supply unit, and the braking unit. At the same time, it receives the working status signals sent by the AFE rectifier cabinet, the inverter unit, the power supply unit, and the braking unit, and detects the voltage of the common DC bus. The AC test motor M1 provides a simulated load for the AC test motor M2 and the DC test motor M3. The braking unit consumes the regenerative electric energy generated by the motor with rapid braking that exceeds 1220V through the braking resistor, which is a safety protection measure for the system.

[0027] The working principle of the AC / DC motor integrated feedback energy recycling system of the present invention is as follows: The AC 400V grid power is boosted to AC 600V by the transformer T1 to supply power to the AFE rectifier cabinet. The AFE rectifier outputs DC power to supply power to the first inverter cabinet INV, the second inverter cabinet INV, the DC / DC conversion cabinet, the DC / DC excitation cabinet and the braking unit, and drives the AC auxiliary test motor M1, the AC test motor M2 and the DC test motor M3 respectively. When the motor load test is carried out, the control unit controls the AC test motor M2 or the DC test motor M3 to work according to the set voltage and frequency, and controls the AC auxiliary test motor M1 to apply a load to the AC test motor M2 or the DC test motor M3 as required. The AC test motor M2 or the DC test motor M3 works in the electric work state, and the AC auxiliary test motor M1 works in the power generation feedback state, feeding back energy to the DC bus. When the AC test motor M2 or the DC test motor M3 and the AC auxiliary test motor M1 are in counter-rotation, energy is mutually fed between the AC auxiliary test motor M1 and the AC test motor M2 or the DC test motor M3 through the inverter cabinet and the common DC bus, and the energy is recycled. The motor test bench only absorbs the heat losses of the frequency converter and the motor from the power grid, reducing the required capacity of the plant transformer. At the same time, the use frequency of the braking resistor is reduced, and the heat loss is reduced. Most of the energy absorbed by the AC test motor M2 or the DC test motor M3 comes from the electric energy fed back by the AC auxiliary test motor M1, and a small part comes from the power grid.

[0028] When the AC auxiliary test motor M1 and the AC test motor M2 or the DC test motor M3 are in counter-rotation, the AC test motor M2 or the DC test motor M3 obtains energy from the DC bus for driving, and the AC auxiliary test motor M1 feeds back energy to the DC bus. When the driving of the AC test motor M2 or the DC test motor M3 and the AC auxiliary test motor M1 is in a balanced state,

[0029] W 试验电机 =W 陪试电机 +W 热损耗 ;

[0030] Where: W 试验电机 ------ The active power required to drive the test motor;

[0031] W 陪试电机 ------ The active power generated by the regenerative power generation of the auxiliary test motor;

[0032] W 热损耗 ------ The active power required for the heating and mechanical wear of the test motor, the auxiliary test motor, the frequency converter, etc.

[0033] The AC test motor M2 or the DC test motor M3 absorbs the electric energy generated by the AC accompanying test motor M1 to realize the recycling of energy. When the AC test motor M2 or the DC test motor M3 and the AC accompanying test motor M1 are in the process of decelerating and reducing torque, the power generation of the AC accompanying test motor M1 is not less than the energy demand of the AC test motor M2 or the DC test motor M3, and the DC bus voltage rises. When the DC bus voltage is higher than 1000V, the AFE rectifier cabinet feeds back energy to the power grid. When the DC bus voltage is between 740V and 1000V, the AFE rectifier cabinet absorbs a small amount of energy from the power grid. In special cases where the AFE rectifier cabinet cannot feed back energy or the fed-back energy cannot be consumed in time, the DC bus voltage will continue to rise. When it reaches 1158V, the braking unit works and the braking resistor is put into operation.

[0034] The present invention also provides a control method for energy feedback, which adopts the above AC-DC motor integrated energy feedback recycling system, as Figure 2 shown. The specific steps are as follows:

[0035] Step 1: Start. The control unit judges whether the AFE rectifier cabinet is operating. If not, it continues to judge whether the rectifier cabinet is operating. If so, it proceeds to the next step.

[0036] Step 2: The control unit judges whether the motor under test is an AC motor or a DC motor. If it is an AC motor, it judges whether the second inverter cabinet INV is operating. If it is a DC motor, it judges whether the DC / DC conversion cabinet and the DC / DC excitation cabinet are operating.

[0037] Step 3: The control unit judges whether the first inverter cabinet INV is operating. If not, it continues to judge whether the first inverter cabinet INV is operating. If so, it proceeds to the next step.

[0038] Step 4: The controller judges whether the DC bus is less than 740V. If so, it starts timing for 3s. If the DC bus is still less than 740V after 3s, the second inverter cabinet INV or the DC / DC conversion cabinet and the DC / DC excitation cabinet stop working, and the first inverter cabinet INV stops working, reporting an under-voltage protection fault. If not, it judges whether the DC bus voltage is not less than 1000V.

[0039] Step 5: The control unit judges whether the DC bus is not less than 1000V. If so, the AFE rectifier cabinet feeds back energy to the power grid, and at the same time enters Step 7. If not, it proceeds to the next step.

[0040] Step 6: The first inverter cabinet INV, the second inverter cabinet INV or the DC / DC conversion cabinet and the DC / DC excitation cabinet work according to the instructions of the control unit. The AC test motor M2 or the DC test motor M3 works in the VF separation or speed control mode and is in the electric state. The AC accompanying test motor M1 works in the torque control mode and is in the power generation state, feeding back energy to the DC bus.

[0041] Step 7: The control unit determines whether the DC bus voltage is not less than 1158V. If so, three operations are synchronously completed. One is that the braking unit and the braking resistor are put into operation. The second is to determine whether the DC bus voltage is not less than 1120V, and simultaneously enter Step 8. The third is to enter Step 6. If not, continue to execute from Step 4.

[0042] Step 8: The control unit determines whether the DC bus voltage is not less than 1220V. If so, start timing for 3s. If the DC bus voltage is still not less than 1220V after 3s, the second inverter cabinet INV or the DC / DC conversion cabinet stops working, and the first inverter cabinet INV stops working, reporting an overvoltage protection fault. If not, continue to execute from Step 5 to complete the control process of recycling the feedback energy.

[0043] Embodiment 1

[0044] This embodiment provides a test bench for a system for recycling feedback energy by integrating AC and DC motors, as Figure 1 shown, which includes a circuit breaker Q1, a circuit breaker Q2, a transformer T1, and an AFE rectifier cabinet. The circuit breaker Q1, the circuit breaker Q2, the transformer T1, and the AFE rectifier cabinet are connected in series in sequence through a first wire. The AFE rectifier cabinet is connected in parallel with an inverter unit, a power supply unit, and a braking unit through a DC bus. The AFE rectifier cabinet, the inverter unit, the power supply unit, and the braking unit are respectively connected to a control unit through a second wire. The inverter unit is connected to an AC test motor M1 and an AC test motor M2 respectively through an AC bus. The power supply unit is connected to a DC test motor M3 and a DC excitation power supply respectively through a DC bus. The braking unit is connected to a braking resistor BR through a DC bus.

[0045] Embodiment 2

[0046] This embodiment provides a system for recycling feedback energy of a test bench for integrating AC and DC motors, as Figure 1As shown, it includes circuit breaker Q1, circuit breaker Q2, transformer T1 and AFE rectifier cabinet. Circuit breaker Q1, circuit breaker Q2, transformer T1 and AFE rectifier cabinet are connected in series in turn through the first wire. The AFE rectifier cabinet is connected in parallel with an inverter unit, a power supply unit and a braking unit through a DC bus. The AFE rectifier cabinet, the inverter unit, the power supply unit and the braking unit are respectively connected with a control unit through the second wire. The inverter unit is respectively connected with an AC test motor M1 and an AC test motor M2 through an AC bus. The power supply unit is respectively connected with a DC test motor M3 and a DC excitation power supply through a DC bus. The braking unit is connected with a braking resistor BR through a DC bus. The inverter unit includes a first inverter cabinet INV and a second inverter cabinet INV. The first inverter cabinet INV is connected with the AC test motor M1 through an AC bus. The second inverter cabinet is connected with the AC test motor M2 through an AC bus. The power supply unit includes a DC / DC conversion cabinet and a DC / DC excitation cabinet. The DC / DC conversion cabinet is connected with the DC test motor M3 through a DC bus. The DC / DC excitation cabinet is connected with the DC excitation power supply through a DC bus.

[0047] Embodiment 3

[0048] This embodiment provides a system for recycling feedback energy of an AC-DC motor integrated test bench. As Figure 1 shown, it includes circuit breaker Q1, circuit breaker Q2, transformer T1 and AFE rectifier cabinet. Circuit breaker Q1, circuit breaker Q2, transformer T1 and AFE rectifier cabinet are connected in series in turn through the first wire. The AFE rectifier cabinet is connected in parallel with an inverter unit, a power supply unit and a braking unit through a DC bus. The AFE rectifier cabinet, the inverter unit, the power supply unit and the braking unit are respectively connected with a control unit through the second wire. The inverter unit is respectively connected with an AC test motor M1 and an AC test motor M2 through an AC bus. The power supply unit is respectively connected with a DC test motor M3 and a DC excitation power supply through a DC bus. The braking unit is connected with a braking resistor BR through a DC bus. The inverter unit includes a first inverter cabinet INV and a second inverter cabinet INV. The first inverter cabinet INV is connected with the AC test motor M1 through an AC bus. The second inverter cabinet is connected with the AC test motor M2 through an AC bus. The power supply unit includes a DC / DC conversion cabinet and a DC / DC excitation cabinet. The DC / DC conversion cabinet is connected with the DC test motor M3 through a DC bus. The DC / DC excitation cabinet is connected with the DC excitation power supply through a DC bus. The first inverter cabinet INV and the second inverter cabinet INV are respectively connected with the control unit through the second wire. The power supply unit includes a DC / DC conversion cabinet and a DC / DC excitation cabinet which are respectively connected with the control unit through the second wire. The AC test motor M1 and the AC test motor M2 or the DC test motor M3 are flange-connected with a torque sensor.

[0049] Embodiment 4

[0050] This embodiment provides a control method for energy feedback, which adopts an AC-DC motor integrated energy feedback recycling system. The specific steps are as follows:

[0051] Step 1: The control unit monitors the DC bus voltage value and determines the type of the test motor. If it is determined that the test motor is an AC test motor M2 and the monitored DC bus voltage value is less than 740V, then time for 3S. If the monitored DC bus voltage value is still less than 740V after 3S, stop the first inverter cabinet INV and the second inverter cabinet INV, and report an under-voltage protection fault;

[0052] If it is determined that the test motor is a DC test motor M3 and the DC bus voltage value is less than 740V, then time for 3S. If the monitored current bus voltage value is still less than 740V after 3S, stop the first inverter cabinet INV, the DC / DC conversion cabinet, and the DC / DC excitation cabinet, and report an under-voltage protection fault;

[0053] If the monitored DC bus voltage value is not less than 740V after 3S, determine whether the DC bus voltage value is not less than 1000V. If it is not less than 1000V, the AFE rectifier cabinet feeds back energy to the power grid, and at the same time enter Step 3; if the DC bus voltage value is less than 1000V, enter Step 2;

[0054] Step 2: If the DC bus voltage value is less than 1000V, the first inverter cabinet INV, the second inverter cabinet INV, or the DC / DC conversion cabinet and the DC / DC excitation cabinet work according to the control unit instructions. The AC test motor M2 and the DC test motor M3 work in the VF separation or speed control mode through the control unit and are in the electric state. The AC auxiliary test motor M1 works in the torque control mode and is in the power generation state, feeding back energy to the DC bus;

[0055] Step 3: If the DC bus voltage value is not less than 1000V, the control unit determines whether the DC bus voltage value is not less than 1158V. If the DC bus voltage value is not less than 1158V, the braking unit and the braking resistor work, and at the same time determine whether the DC bus voltage value is not less than 1120V, and enter Step 4; if the DC bus voltage value is less than 1158V, continue to execute from Step 1;

[0056] Step 4: If the DC bus voltage value is not less than 1220V, time for 3s. If the DC bus voltage value is still not less than 1220V after 3s, stop the first inverter cabinet INV, the second inverter cabinet INV, or the DC / DC conversion cabinet and the DC / DC excitation cabinet, and report an over-voltage protection fault; if the DC bus voltage value is less than 1220V, continue to execute from Step 1 to complete the energy feedback recycling control process.

Claims

1. AC-DC motor integrated feedback energy recycling system, Characterized in that, It includes circuit breaker Q1, circuit breaker Q2, transformer T1 and AFE rectifier cabinet. The circuit breaker Q1, circuit breaker Q2, transformer T1 and AFE rectifier cabinet are connected in series in turn through the first wire. The AFE rectifier cabinet is connected in parallel with an inverter unit, a power supply unit and a braking unit through a DC bus. The AFE rectifier cabinet, inverter unit, power supply unit and braking unit are respectively connected to a control unit through a second wire. The inverter unit is respectively connected to an AC test motor M1 and an AC test motor M2 through an AC bus. The power supply unit is respectively connected to a DC test motor M3 and a DC excitation power supply through a DC bus. The braking unit is connected to a braking resistor BR through a DC bus.

2. The AC-DC motor integrated feedback energy recycling system according to claim 1, Characterized in that, The inverter unit includes a first inverter cabinet INV and a second inverter cabinet INV. The first inverter cabinet INV is connected to the AC test motor M1 through an AC bus. The second inverter cabinet is connected to the AC test motor M2 through an AC bus.

3. The AC-DC motor integrated feedback energy recycling system according to claim 2, Characterized in that, The power supply unit includes a DC / DC conversion cabinet and a DC / DC excitation cabinet. The DC / DC conversion cabinet is connected to the DC test motor M3 through a DC bus. The DC / DC excitation cabinet is connected to the DC excitation power supply through a DC bus.

4. The AC-DC motor integrated feedback energy recycling system according to claim 3, Characterized in that, The first inverter cabinet INV and the second inverter cabinet INV are respectively connected to the control unit through a second wire. The power supply unit includes a DC / DC conversion cabinet and a DC / DC excitation cabinet which are respectively connected to the control unit through a second wire.

5. The AC-DC motor integrated feedback energy recycling system according to claim 4, Characterized in that, The AC test motor M1 and the AC test motor M2 or the DC test motor M3 are flange-connected with a torque sensor.

6. Control method for energy feedback, Characterized in that, Using the AC-DC motor integrated feedback energy recycling system as described in claim 5, the specific steps are as follows: The control unit monitors the DC bus voltage value and judges the type of test motor; determines the working states of the AFE rectifier cabinet, the first inverter cabinet INV, the second inverter cabinet INV, the DC / DC conversion cabinet, the DC / DC excitation cabinet and the braking unit according to the judged type of test motor and the monitored DC bus voltage value, and completes the control of feedback energy recycling.

7. The control method for energy feedback according to claim 6, Characterized in that, The specific steps of the control method for energy feedback are as follows: Step 1: The control unit monitors the DC bus voltage value and determines the type of the test motor. If it is determined that the test motor is the AC test motor M2 and the monitored DC bus voltage value is less than 740V, then time for 3S. If the monitored DC bus voltage value is still less than 740V after 3S, then stop the first inverter cabinet INV and the second inverter cabinet INV, and report an under-voltage protection fault; If it is determined that the test motor is the DC test motor M3 and the DC bus voltage value is less than 740V, then time for 3S. If the monitored current bus voltage value is still less than 740V after 3S, then stop the first inverter cabinet INV, the DC / DC conversion cabinet and the DC / DC excitation cabinet, and report an under-voltage protection fault; If the monitored DC bus voltage value is not less than 740V after 3S, then determine whether the DC bus voltage value is not less than 1000V. If it is not less than 1000V, then the AFE rectifier cabinet feeds energy back to the power grid and simultaneously enters Step 3; if the DC bus voltage value is less than 1000V, then enter Step 2; Step 2: If the DC bus voltage value is less than 1000V, the first inverter cabinet INV, the second inverter cabinet INV or the DC / DC conversion cabinet and the DC / DC excitation cabinet work according to the control unit instructions. The AC test motor M2 and the DC test motor M3 work in the VF separation or speed control mode through the control unit and are in the electric state. The AC accompanying test motor M1 works in the torque control mode and is in the power generation state, feeding energy back to the DC bus; Step 3: If the DC bus voltage value is not less than 1000V, the control unit determines whether the DC bus voltage value is not less than 1158V. If the DC bus voltage value is not less than 1158V, then the braking unit and the braking resistor work, and at the same time determine whether the DC bus voltage value is not less than 1120V, and enter Step 4; if the DC bus voltage value is less than 1158V, then continue to execute from Step 1; Step 4: If the DC bus voltage value is not less than 1220V, time for 3s. If the DC bus voltage value is still not less than 1220V after 3s, then stop the first inverter cabinet INV, the second inverter cabinet INV or the DC / DC conversion cabinet and the DC / DC excitation cabinet, and report an over-voltage protection fault; if the DC bus voltage value is less than 1220V, then continue to execute from Step 1 to complete the control process of recycling the feedback energy.

Images