A system for feedback and discharge of motor back electromotive force energy

Abstract

The present invention relates to a system for feedback and discharge of motor back-electromotive force energy, comprising a power supply, a DC driver circuit, and a motor connected in sequence. The DC driver circuit comprises a voltage control unit, a bus current detection unit, a comparison and determination unit, an energy discharge unit, and a power inverter unit. The voltage control unit is respectively connected to the bus current detection unit, the comparison and determination unit, and the energy discharge unit. The bus current detection unit is respectively connected to the power supply, the comparison and determination unit, and the power inverter unit. The energy discharge unit is connected to the power inverter unit, and the power inverter unit is connected to the motor. Compared with the prior art, the present invention can not only effectively discharge energy to prevent excessive bus voltage, but also allow some energy to be fed back to the battery system for reasonable reuse.

Description

Technical Field

[0001] The present invention relates to a power system, and in particular to a system for feeding back and discharging back electromotive force energy of a motor. Background Art

[0002] With the rapid development of AGVs and RGVs in the warehousing and logistics industry, the use of power systems consisting of batteries and DC drive systems is becoming increasingly common. The back EMF energy generated by the high acceleration and deceleration movement of the DC drive system during the vehicle's operation will cause a series of difficult problems if not effectively handled:

[0003] (1) The back EMF energy is not released, but is absorbed by the battery itself. When a large current is fed back into the battery system, the internal management system of the power battery will have protective measures to suppress the influx of large current. This will cause the battery and driver bus voltage to increase instantly, which may cause the system to alarm due to overvoltage and fail to operate normally. In more serious cases, it may cause the driver components to have insufficient voltage resistance, resulting in damage and breakdown.

[0004] (2) The situation where the back EMF energy is completely discharged and absorbed. This ignores the fact that the battery system itself can also absorb and utilize energy from small currents. If all the energy is discharged in the form of heat generated by dissipative resistance, on the one hand, it will increase the ambient temperature and be detrimental to the reliable operation of the system, and on the other hand, it will also have a negative impact on the battery life.

[0005] In response to the above situation, there are currently several main measures to discharge the back EMF energy and reduce the risk of system operation:

[0006] The first method for dissipating back-EMF energy utilizes the reverse cutoff characteristics of power diodes to trap the generated back-EMF energy in a circuit storage element (such as a large electrolytic capacitor). The voltage difference between the front and rear sides of the diode is then used as a trigger. When the rear voltage exceeds the front voltage by a set fixed value, the discharge circuit is opened to release the energy. In battery applications, this method has the disadvantage that, due to the presence of the diode, the back-EMF energy cannot be returned to the battery system and is dissipated entirely by heat generated by the dissipation resistor. Normal operation of the DC drive also generates losses and temperature rise in the diode.

[0007] The common methods retrieved by the following technology are the methods described above:

[0008] (i) "A large magnetic torquer energy discharge control circuit" (CN103107718B) proposed by Fan Jiakun, Meng Haijiang, et al. The implementation principle is detailed in its specification and drawings. Due to the series connection of busbar diode D5, energy cannot return to VCC.

[0009] (ii) “A motor and motor protection method” (CN106549362A) proposed by Guan Hongxing. The implementation principle is detailed in its description and drawings. Due to the series connection of diode D1 on the busbar, energy cannot return to VCC.

[0010] A second common method is to set a fixed bus voltage trigger point through hardware circuitry or firmware. When the bus voltage is detected to be above the set value, the bleeder circuit is activated; when the bus voltage is below the set value, the bleeder circuit is closed. This method is frequently used in AC servo drives. However, within the conventional 12-70 VDC voltage range, it is difficult to set a fixed, uniform bleeder point to meet the varying battery voltage requirements of different customers.

[0011] The common methods retrieved by the following technology are the methods described above:

[0012] (i) Wang Xianwei, Xu Donggui, et al. proposed an “AC servo driver with intelligent discharge function” (CN205017242U). The discharge implementation principle is detailed in its specification and drawings. The bus sampling voltage is compared with the reference voltage, and the comparator result determines whether to trigger the discharge circuit.

[0013] (ii) Duan Tianfu et al. proposed a “servo driver with busbar discharge circuit detection function” (CN105978443B). The implementation principle is detailed in its specification and drawings. It compares the busbar voltage detection value with the reference value set by the firmware program, and its processor determines whether the discharge circuit is activated.

[0014] (iii) Liu Youhui and Zhou Quanbing proposed "A Brake Overpressure Relief Protection Device and Electronic Speed ​​Regulator" (CN206947942U). The discharge mechanism is detailed in its specification and accompanying drawings. The device compares the busbar sampled voltage with a reference voltage, and the result determines whether to trigger the discharge circuit. However, the reference voltage used in this battery system is difficult to adapt to different battery voltages within the 12-70 VDC range.

[0015] The above two methods of discharging back EMF energy with resistors are conventional and economical practices. Currently, some AC servo systems use the method of AFE front-end rectification feedback to directly feed back the back EMF energy to the AC grid without dissipating resistors, thus achieving energy saving. However, this solution is currently expensive and its circuit topology is as follows: Figure 1 As shown, it is generally used in AC variable frequency speed control systems with high power and large inertia. Summary of the Invention

[0016] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a system for feedback and discharge of motor back-EMF energy.

[0017] The purpose of the present invention can be achieved by the following technical solutions:

[0018] A system for feedback and discharge of motor back-electromotive force energy includes a power supply, a DC driver circuit, and a motor connected in sequence. The DC driver circuit includes a voltage control unit, a bus current detection unit, a comparison and determination unit, an energy discharge unit, and a power inverter unit. The voltage control unit is respectively connected to the bus current detection unit, the comparison and determination unit, and the energy discharge unit. The bus current detection unit is respectively connected to the power supply, the comparison and determination unit, and the power inverter unit. The energy discharge unit is connected to the power inverter unit. The power inverter unit is connected to the motor.

[0019] The bus current detection unit monitors the direction and magnitude of the current on the bus, and controls the closing of the energy discharge unit through the comparison and judgment unit, thereby effectively discharging energy to prevent the bus voltage from being too high, and also allowing part of the energy to be fed back to the power supply for reasonable reuse.

[0020] Preferably, the power supply is a battery or a supercapacitor.

[0021] Preferably, the DC driver circuit further includes a filter unit, which may be located between the power supply and the bus current detection unit.

[0022] Preferably, the DC driver circuit further includes a filter unit, which may be located between the bus current detection unit and the power inverter unit.

[0023] Preferably, the bus current detection unit is a current sensor device, or a current detection device with the same function, or detects current by connecting a resistor in series.

[0024] Preferably, the comparison and determination unit is a comparator hardware circuit.

[0025] Preferably, the specific implementation process of the comparator hardware circuit determination action is as follows:

[0026] (1) In the initial power-on state, the reference voltage of the comparator hardware circuit is higher than the voltage of the bus current detection unit, the output of the comparator hardware circuit is low, and the energy discharge unit remains off;

[0027] (2) When the DC driver circuit is running, if the reference voltage of the comparator hardware circuit is still higher than the voltage of the bus current detection unit, the comparator output is low and the energy discharge unit remains off;

[0028] (3) When the DC driver circuit is running, if the voltage of the bus current detection unit is higher than the reference voltage of the comparator hardware circuit, the output of the comparator hardware circuit flips to high, and the energy discharge unit is turned on to discharge energy;

[0029] (4) When the back electromotive force energy is gradually discharged and reduced, the reference voltage of the comparator hardware circuit is higher than the output voltage of the bus current detection unit, the output of the comparator hardware circuit flips to low, the energy discharge unit is turned off, and the process returns to step (2).

[0030] Preferably, the comparison and determination unit is a processor unit.

[0031] Preferably, the specific implementation process of the processor determination action is as follows:

[0032] (1) In the initial power-on state, the energy discharge unit remains off;

[0033] (2) When the DC driver circuit is running, the processor unit periodically detects the voltage output value of the bus current detection unit and compares it with the reference voltage value set by the program;

[0034] (3) If it is determined that the output voltage is greater than the reference voltage value, the energy discharge unit is turned on;

[0035] (4) In other cases, the energy discharge unit is shut down.

[0036] Preferably, the energy discharge unit includes a power tube Q1, a dissipation resistor R1 and a diode D1. The base of the power tube Q1 is connected to the comparison and judgment unit, the collector is connected to one end of the dissipation resistor R1 and the positive electrode of the diode D1, and the other end of the dissipation resistor R1 and the negative electrode of the diode D1 are respectively connected between the bus current detection unit and the power inverter unit.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] (1) Compared with the aforementioned solution that uses diodes to cut off energy backflow and uses voltage difference to trigger discharge, the present invention is more suitable for battery-powered power systems. It can not only effectively discharge energy to prevent the bus voltage from being too high, but also allow some energy to be fed back to the battery system for reasonable reuse. Moreover, since there are no diodes on the bus through which large currents flow, it can further reduce the power loss and heat generation of the entire power system, thereby extending the battery life.

[0039] (2) Compared with the aforementioned bus voltage discharge value solution that uses hardware or program to set a fixed value, the present invention is only related to the direction and magnitude of the bus current and has nothing to do with the absolute value of the bus voltage. It can be more widely applied to situations where different customers are powered by different battery voltages. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the prior art AFE front-end rectification feedback technology;

[0041] Figure 2 It is the principle topology diagram of the present invention;

[0042] Figure 3 This is a topological diagram of the principle of the battery-powered DC driver circuit of the present invention performing external work;

[0043] Figure 4 This is a principle topology diagram of the present invention in which the back electromotive force energy generated by motor deceleration is relatively small;

[0044] Figure 5 This is a principle topology diagram of the present invention in which the back electromotive force energy generated by motor deceleration is relatively large;

[0045] Figure 6 This is a topological diagram of the principle of a hardware comparator used in the comparison and determination unit of the present invention;

[0046] Figure 7 This is a schematic topology diagram of a processor used in the comparison and determination unit of the present invention;

[0047] Figure 8 A control flow chart of a processor used in the comparison and determination unit of the present invention;

[0048] Figure 9 This is a principle topology diagram of the filter unit of the present invention installed at the front end. DETAILED DESCRIPTION

[0049] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0050] The back-EMF energy feedback and discharge system of this invention focuses on applications where a battery system (or supercapacitor) powers a DC drive. Unlike conventional methods that use bus voltage monitoring to trigger the discharge circuit, this system uses the direction and magnitude of the bus current as a trigger to determine whether the discharge circuit is activated. When back-EMF energy is generated, it is effectively discharged internally to prevent the bus voltage from overshooting. It also allows some energy to be fed back to the battery system for rational reuse, significantly reducing power loss and heat generation throughout the power system and extending battery life.

[0051] The main innovations of the present invention are:

[0052] (1) The direction and magnitude of the current on the DC bus are used as the basis for determining whether the discharge should be activated;

[0053] (2) Allowing an appropriate amount of back-electromotive force energy to be fed back to the battery makes the entire power system more energy-efficient and can extend the battery life.

[0054] like Figure 2 As shown, a system for motor back-EMF energy feedback and discharge includes a power supply 1, a DC driver circuit 2, and a motor 3 connected in sequence. The DC driver circuit 2 includes a voltage control unit 202, a bus current detection unit 201, a comparison and determination unit 203, an energy discharge unit 204, and a power inverter unit 205. The voltage control unit 202 is respectively connected to the bus current detection unit 201, the comparison and determination unit 203, and the energy discharge unit 204. The bus current detection unit 201 is respectively connected to the power supply 1, the comparison and determination unit 203, and the power inverter unit 205. The energy discharge unit 204 is connected to the power inverter unit 205. The power inverter unit 205 is connected to the motor 3.

[0055] The bus current detection unit 201 monitors the direction and magnitude of the current on the bus, and controls the shutdown of the energy discharge unit through the comparison and judgment unit 203, thereby effectively discharging energy to prevent the bus voltage from being too high, and also allowing part of the energy to be fed back to the power supply for reasonable reuse.

[0056] The power supply is a battery or a supercapacitor. The energy dissipation unit includes a power tube Q1, a dissipation resistor R1, and a diode D1. The base of the power tube Q1 is connected to the comparison and determination unit, the collector is connected to one end of the dissipation resistor R1 and the positive electrode of the diode D1, and the other end of the dissipation resistor R1 and the negative electrode of the diode D1 are respectively connected between the bus current detection unit and the power inverter unit.

[0057] The busbar current detection unit is a current sensor chip, or a current detection chip with the same function and capable of withstanding high common mode voltage, or a combination circuit with the same function.

[0058] Energy flow diagram of the system of the present invention in different states:

[0059] (i) When the battery-powered DC driver circuit is working externally, the internal discharge circuit does not operate, and the battery provides energy to the motor to work, such as Figure 3 As shown:

[0060] (ii) When the back EMF energy generated by motor deceleration is small and the outflow current is less than the set threshold, the internal discharge circuit does not operate and the energy is fed back to the battery. Figure 4 As shown:

[0061] (iii) When the back EMF energy generated by motor deceleration is large and the outflow current exceeds the set threshold, the internal discharge circuit is activated, part of the energy is absorbed by the dissipation resistor to generate heat, and part of the energy is fed back to the battery system, such as Figure 5 As shown:

[0062] The present invention is implemented by comparing a comparator hardware circuit or a processor firmware program.

[0063] The comparator circuit (or processor unit) compares the output voltage value of the bus current detection unit with the reference voltage value to obtain the direction and magnitude of the bus current and performs the following actions based on the comparison result:

[0064] (1) If the current flows in the positive direction or flows out in the reverse direction but does not exceed the set threshold, the internal discharge unit of the driver will not operate;

[0065] (2) If the outflow current is in the reverse direction and exceeds the set threshold voltage range, the internal discharge unit of the driver will be activated.

[0066] like Figure 6 As shown, the comparison and determination unit is a comparator hardware circuit 2031.

[0067] The specific implementation process of the comparator hardware circuit determination action is as follows:

[0068] (1) In the initial power-on state, the reference voltage of the comparator hardware circuit is higher than the voltage of the bus current detection unit, the output of the comparator hardware circuit is low, and the energy discharge unit remains off;

[0069] (2) When the DC driver circuit is running, if the reference voltage of the comparator hardware circuit is still higher than the voltage of the bus current detection unit, the comparator output is low and the energy discharge unit remains off;

[0070] (3) When the DC driver circuit is running, if the voltage of the bus current detection unit is higher than the reference voltage of the comparator hardware circuit, the output of the comparator hardware circuit flips to high, and the energy discharge unit is turned on to discharge energy;

[0071] (4) When the back electromotive force energy is gradually discharged and reduced, the reference voltage of the comparator hardware circuit is higher than the output voltage of the bus current detection unit, the output of the comparator hardware circuit flips to low, the energy discharge unit is turned off, and the process returns to step (2).

[0072] like Figure 7 As shown, the comparison and determination unit is a processor unit.

[0073] like Figure 8 As shown, the specific implementation process of the processor determination action is as follows:

[0074] (1) In the initial power-on state, the energy discharge unit remains off;

[0075] (2) When the DC driver circuit is running, the processor unit periodically detects the voltage output value of the bus current detection unit and compares it with the reference voltage value set by the program;

[0076] (3) If it is determined that the output voltage is greater than the reference voltage value, the energy discharge unit is turned on;

[0077] (4) In other cases, the energy discharge unit is shut down.

[0078] Note: The reference voltage refers to the voltage value output by the bus current detection unit when the bus current outflow is the set threshold.

[0079] like Figure 9 As shown, the DC driver circuit 2 further includes a filter unit 206, which is located between the power supply 1 and the bus current detection unit 201. Figure 2 As shown, the DC driver circuit 2 also includes a filter unit 206, which is located between the bus current detection unit 201 and the power inverter unit 205, that is, the filter unit can be located at the front end or the rear end of the bus current detection unit, and the voltage control unit is responsible for voltage conversion for use by each module.

[0080] Therefore, this back-EMF energy feedback and discharge system refers to a DC drive system that monitors the bus current size and direction as a basis for whether to initiate discharge. It can be mainly used in application scenarios with DC power supply such as batteries (or supercapacitors).

[0081] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A system for feedback and discharge of motor back-EMF energy, characterized in that: The device comprises a power supply, a DC driver circuit and a motor connected in sequence, wherein the DC driver circuit comprises a voltage control unit, a bus current detection unit, a comparison and determination unit, an energy discharge unit and a power inverter unit, wherein the voltage control unit is respectively connected to the bus current detection unit, the comparison and determination unit and the energy discharge unit, wherein the bus current detection unit is respectively connected to the power supply, the comparison and determination unit and the power inverter unit, wherein the energy discharge unit is connected to the power inverter unit, and wherein the power inverter unit is connected to the motor; The bus current detection unit monitors the direction and magnitude of the current on the bus, and controls the shutdown of the energy discharge unit through the comparison and judgment unit, thereby effectively discharging energy, preventing the bus voltage from being too high, and allowing part of the energy to be fed back to the power supply for reasonable reuse; This is achieved by comparing a comparator hardware circuit or a processor firmware program; The comparator circuit or processor unit compares the output voltage value of the bus current detection unit with the reference voltage value to obtain the direction and magnitude of the bus current and performs the following actions based on the comparison result: (1) If the current flows in the positive direction, the internal discharge unit of the driver does not operate, and the battery provides energy to the motor to work; or if the current flows out in the reverse direction but does not exceed the set threshold, the internal discharge unit of the driver does not operate, and energy is fed back to the battery; (2) If the outflow current is in the reverse direction and exceeds the set threshold voltage range, the internal discharge unit of the driver will be activated, part of the energy will be absorbed by the dissipation resistor to generate heat, and part of the energy will be fed back to the battery system; The comparison and determination unit is a comparator hardware circuit or a processor unit.

2. The motor back-EMF energy feedback and discharge system according to claim 1, characterized in that: The power supply is a DC power supply system.

3. The motor back-EMF energy feedback and discharge system according to claim 1, characterized in that: The DC driver circuit further includes a filter unit, which may be located between the power supply and the bus current detection unit.

4. The motor back-EMF energy feedback and discharge system according to claim 1, characterized in that: The DC driver circuit further includes a filter unit, which may be located between the bus current detection unit and the power inverter unit.

5. The motor back-EMF energy feedback and discharge system according to claim 1, characterized in that: The busbar current detection unit is a current sensor device, or a current detection device with the same function, or detects current by connecting a resistor in series.

6. The motor back-EMF energy feedback and discharge system according to claim 1, characterized in that: The specific implementation process of the comparator hardware circuit determination action is as follows: (1) In the initial power-on state, the reference voltage of the comparator hardware circuit is higher than the voltage of the bus current detection unit, the output of the comparator hardware circuit is low, and the energy discharge unit remains off; (2) When the DC driver circuit is running, if the reference voltage of the comparator hardware circuit is still higher than the voltage of the bus current detection unit, the comparator output is low and the energy discharge unit remains off; (3) When the DC driver circuit is running, if the voltage of the bus current detection unit is higher than the reference voltage of the comparator hardware circuit, the output of the comparator hardware circuit flips to high, and the energy discharge unit is turned on to discharge energy; (4) When the back electromotive force energy is gradually discharged and reduced, the reference voltage of the comparator hardware circuit is higher than the output voltage of the bus current detection unit, the output of the comparator hardware circuit flips to low, the energy discharge unit is turned off, and the process returns to step (2).

7. The motor back-EMF energy feedback and discharge system according to claim 1, characterized in that: The specific implementation process of the processor determination action is as follows: (1) In the initial power-on state, the energy discharge unit remains off; (2) When the DC drive circuit is running, the processor unit periodically detects the voltage output value of the bus current detection unit and compares it with the reference voltage value set by the program; (3) If the output voltage is greater than the reference voltage, the energy discharge unit is turned on; (4) In other cases, the energy discharge unit is shut down.

8. The motor back-EMF energy feedback and discharge system according to claim 1, characterized in that: The energy discharge unit includes a power tube Q1, a dissipation resistor R1 and a diode D1. The base of the power tube Q1 is connected to the comparison and judgment unit, the collector is connected to one end of the dissipation resistor R1 and the positive electrode of the diode D1, and the other end of the dissipation resistor R1 and the negative electrode of the diode D1 are respectively connected between the bus current detection unit and the power inverter unit.

Images