A large-load electric engineering vehicle energy feedback circuit

Abstract

The present invention relates to an energy feedback circuit for a heavy-load electric engineering vehicle, comprising a circuit breaker, a DC bus filter capacitor, an energy conversion unit, a first common-mode transformer, a second common-mode transformer, a third common-mode transformer and a control unit; the control unit is communicatively connected with the energy conversion unit, and when it is necessary to reduce the actual motor speed of a three-phase motor, the control unit is used to control the duty ratio of a plurality of MOS tubes in the energy conversion unit, so that after the current value of the three-phase alternating current output by the energy conversion unit is reduced, the three-phase alternating current is input into the three-phase motor, and the three-phase feedback voltage generated by the three-phase motor is respectively fed back to a battery through three common-mode transformers to charge the battery, thereby saving power resources and avoiding the accumulation of feedback energy at both ends of a power device and one side of a circuit breaker, thereby avoiding damage to the circuit breaker and the power device, protecting the circuit, and improving the service life and safety of the heavy-load electric engineering vehicle.

Description

Technical Field

[0001] The invention relates to the technical field of engineering vehicle control, and in particular to an energy feedback circuit for a heavy-load electric engineering vehicle. Background Art

[0002] With the development of new energy, electric passenger cars are booming, and large-load electric engineering vehicles are becoming more and more popular. Compared with electric passenger cars, large-load electric engineering vehicles have the characteristics of low input voltage and large output current; their input voltage is generally 24V to 144V, and their output current can reach up to 600A. Common large-load electric engineering vehicles include 10-ton forklifts and 40-meter scissor lifts, which can all be driven by electric energy. Traditional mechanical brakes only use brake pads to brake large-load engineering vehicles, which consumes brake pads extremely, resulting in a short life of brake pads and unsatisfactory braking effect. Therefore, the energy feedback unit of the inverter used in the drive circuit is a special brake unit, which is mainly used in large-inertia and drag variable frequency speed regulation systems to help the motor feed back the regenerated electric energy generated during its deceleration to the power grid, and at the same time assist the system to achieve rapid braking function; but due to the large load of engineering vehicles, weighing several tons or even dozens of tons, in the deceleration, emergency stop and other working links, large inertia, large feedback energy, complex control, easy damage to equipment, and easy energy loss.

[0003] Reference Figure 1 As shown in the figure, it is a schematic diagram of the traditional working circuit of a large-load electric engineering vehicle; the energy is provided by the battery, and reaches the motor through the energy conversion unit, converting the electrical energy into mechanical energy, and a circuit breaker is set as a protection device to cut off the connection between the battery and the motor so as to cut off the power supply to the motor. Among them, the power devices Z1, Z2, Z3, Z4, Z5 and Z6 form an energy conversion unit to convert direct current into alternating current; the power devices Z1, Z2, Z3, Z4, Z5 and Z6 are turned on and off alternately to generate three-phase currents U, V, and W, which flow into the motor. In the process of emergency stop and deceleration, when the actual motor speed is greater than the preset speed, the control system controls the power device in the direction of flowing out of the motor, and the current flows to the circuit breaker through the diode in the power device. At this time, the current is too large and the circuit breaker is easily damaged; at the same time, the motor winding is inductive, and the current reverses in a very short time, generating overvoltage, which is applied to both ends of the power device. The voltage is too large, which is very easy to damage the power device. Similarly, during the actual operation of a heavy-load electric engineering vehicle, when faced with an emergency situation and the circuit breaker needs to be turned off, the connection between the energy conversion unit and the power supply is cut off, and control of the energy conversion unit is lost. At this time, the motor generates back electromotive force due to inertia, the circuit breaker is disconnected, and there is no discharge path. The back electromotive force accumulates at both ends of the power device and one end of the circuit breaker, which can easily damage the power device and the circuit breaker.

[0004] In summary, in the traditional control circuit used in heavy-load electric engineering vehicles, when the actual motor speed is greater than the corresponding preset speed, such as when the circuit breaker is turned off, the heavy-load engineering vehicle stops suddenly or decelerates, the energy at the motor will be fed back to the battery; at this time, if the circuit breaker is turned off, the energy will accumulate at both ends of the power device and on one side of the circuit breaker, which can easily damage the circuit breaker and the power device; if the circuit breaker is turned on, a large current will flow to the circuit breaker, which can easily damage the circuit breaker, and the reverse overvoltage generated at the same time will be applied to both ends of the power device, which can easily damage the power device. Therefore, when the actual motor speed is greater than the corresponding preset speed, the control circuit will be damaged, which will affect the service life and safety of the heavy-load electric engineering vehicle. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to overcome the problem that the prior art is unable to consume the energy feedback caused by the actual motor speed of a large-load engineering vehicle being greater than the corresponding preset speed, resulting in energy accumulation and damage to the control circuit.

[0006] In order to solve the above technical problems, the present invention provides an energy feedback circuit for a large-load electric engineering vehicle, comprising:

[0007] A circuit breaker, one end of which is connected to the positive terminal of the battery;

[0008] A DC bus filter capacitor, one end of which is connected to the other end of the circuit breaker, and the other end of which is connected to the negative electrode of the battery;

[0009] An energy conversion unit is connected in parallel to both ends of the DC bus filter capacitor to convert the DC power output by the battery into three-phase AC power, and output it to the three-phase motor through the three-phase output terminal;

[0010] A first common-mode transformer, wherein the primary side pin 1 is connected to the first phase output terminal of the energy conversion unit, the primary side pin 2 is connected to the first phase input terminal of the three-phase motor, the secondary side pin 3 is connected to the negative electrode of the battery, the secondary side pin 4 is connected to the anode of the first secondary side diode, and the cathode of the first secondary side diode is connected to the positive electrode of the battery;

[0011] A second common-mode transformer, wherein the primary side pin 1 is connected to the second phase output terminal of the energy conversion unit, the primary side pin 2 is connected to the second phase input terminal of the three-phase motor, the secondary side pin 3 is connected to the negative electrode of the battery, the secondary side pin 4 is connected to the anode of the second secondary side diode, and the cathode of the second secondary side diode is connected to the positive electrode of the battery;

[0012] A third common-mode transformer, wherein the primary side pin 1 is connected to the third-phase output terminal of the energy conversion unit, the primary side pin 2 is connected to the third-phase input terminal of the three-phase motor, the secondary side pin 3 is connected to the negative electrode of the battery, the secondary side pin 4 is connected to the anode of the third secondary diode, and the cathode of the third secondary diode is connected to the positive electrode of the battery;

[0013] The control unit is communicatively connected with the energy conversion unit. When the actual motor speed of the three-phase motor needs to be reduced, the control unit is used to control the duty cycle of multiple MOS tubes in the energy conversion unit, so that the current value of the three-phase alternating current output by the energy conversion unit is reduced and then input into the three-phase motor. The three-phase feedback voltage generated by the three-phase motor is fed back to the battery through three common-mode transformers respectively to charge the battery.

[0014] Preferably, when the actual motor speed of the three-phase motor needs to be reduced, the control unit is used to control the duty cycle of multiple MOS tubes in the energy conversion unit, so that the current value of the three-phase alternating current output by the energy conversion unit is reduced, so that the actual motor speed of the three-phase motor is reduced to the first preset speed. At this time:

[0015] The current flowing through the primary sides of the first common-mode transformer, the second common-mode transformer and the third common-mode transformer is reduced;

[0016] In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side 2 pin and the secondary side 4 pin is positive;

[0017] In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side pin 1 and the secondary side pin 3 is negative;

[0018] The secondary diodes of the first common-mode transformer, the second common-mode transformer and the third common-mode transformer are all forward-connected. Based on the electromagnetic characteristics of the inductance in the common-mode transformer, a reverse feedback current is generated and fed back to the battery through the common-mode transformer to charge the battery.

[0019] Preferably, the situations where the actual motor speed of the three-phase motor needs to be reduced include: a heavy-load engineering vehicle shuts down the circuit breaker to stop running, emergency braking and deceleration;

[0020] When a heavy-load engineering vehicle turns off the circuit breaker to stop running and performs emergency braking, the first preset speed is 0;

[0021] When the heavy-load engineering vehicle decelerates, the first preset speed is greater than or equal to 0 and less than or equal to the actual motor speed of the three-phase motor.

[0022] Preferably, when the actual motor speed of the three-phase motor needs to be increased, the control unit is used to control the duty cycle of multiple MOS tubes in the energy conversion unit, so that the current value of the three-phase alternating current output by the energy conversion unit increases and is then input into the three-phase motor. The electrical energy of the three-phase alternating current is converted into mechanical energy of the three-phase motor, driving the three-phase motor to accelerate.

[0023] Preferably, the situations where the actual motor speed of the three-phase motor needs to be increased include starting and accelerating operation of a heavy-load engineering vehicle.

[0024] Preferably, when the actual motor speed of the three-phase motor needs to be increased, the control unit is used to control the duty cycle of multiple MOS tubes in the energy conversion unit, so that the current value of the three-phase alternating current output by the energy conversion unit increases and is input into the three-phase motor, so that the actual motor speed of the three-phase motor increases to the second preset speed. At this time:

[0025] The current flowing through the primary sides of the first common mode transformer, the second common mode transformer and the third common mode transformer increases;

[0026] In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side pin 1 and the secondary side pin 3 is positive;

[0027] In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side 2 pin and the secondary side 4 pin is negative;

[0028] The secondary diodes of the first common-mode transformer, the second common-mode transformer and the third common-mode transformer are all reversely connected, and the three-phase AC current is converted into mechanical energy after entering the three-phase motor without energy feedback.

[0029] Preferably, it also includes a current control unit with adjustable equivalent resistance;

[0030] The current control unit with adjustable equivalent resistance includes multiple resistors connected in series, the free end of the first resistor in series is connected to the positive electrode of the battery, and the free end of the last resistor in series is connected to one end of the circuit breaker; each resistor is connected in parallel with a switch, and the control unit is communicatively connected with all the switches, and the equivalent resistance of the current control unit is adjusted by controlling the on and off of the switch, so as to adjust the current size of the direct current flowing into the energy conversion unit.

[0031] Preferably, the energy conversion unit comprises an upper bridge arm and a lower bridge arm;

[0032] The upper bridge arm comprises:

[0033] A first MOS tube, a drain of which is connected to the other end of the circuit breaker, and a gate of which is connected to the control unit;

[0034] a first body diode connected in parallel to both ends of the first MOS tube, with an anode connected to the source of the first MOS tube and a cathode connected to the drain of the first MOS tube;

[0035] A third MOS tube, a drain of which is connected to the other end of the circuit breaker, and a gate of which is connected to the control unit;

[0036] A third body diode is connected in parallel to both ends of the third MOS tube, an anode of the third body diode is connected to the source of the third MOS tube, and a cathode of the third body diode is connected to the drain of the third MOS tube;

[0037] a fifth MOS tube, a drain of which is connected to the other end of the circuit breaker, and a gate of which is connected to the control unit;

[0038] a fifth body diode, connected in parallel to both ends of the fifth MOS tube, with an anode connected to the source of the fifth MOS tube and a cathode connected to the drain of the fifth MOS tube;

[0039] The lower bridge arm comprises:

[0040] A second MOS tube, whose drain is connected to the source of the first MOS tube, and the connection point serves as the third output end of the energy conversion unit; whose source is connected to the negative electrode of the battery, and whose gate is connected to the control unit;

[0041] a second body diode connected in parallel to both ends of the second MOS tube, with an anode connected to the source of the second MOS tube and a cathode connected to the drain of the second MOS tube;

[0042] A fourth MOS tube, whose drain is connected to the source of the third MOS tube, and the connection point serves as the second output end of the energy conversion unit; whose source is connected to the negative electrode of the battery, and whose gate is connected to the control unit;

[0043] a fourth body diode, connected in parallel to both ends of the fourth MOS tube, with an anode connected to the source of the fourth MOS tube and a cathode connected to the drain of the fourth MOS tube;

[0044] A sixth MOS tube, whose drain is connected to the source of the fifth MOS tube, and the connection point serves as the first output end of the energy conversion unit; whose source is connected to the negative electrode of the battery, and whose gate is connected to the control unit;

[0045] A sixth body diode is connected in parallel to both ends of the sixth MOS tube, an anode of the sixth body diode is connected to the source of the sixth MOS tube, and a cathode of the sixth body diode is connected to the drain of the sixth MOS tube.

[0046] Preferably, any MOS tube in the upper bridge arm of the energy conversion unit and any MOS tube in the lower bridge arm that does not belong to the same phase as the MOS tube are used as a group of MOS tube units, and the duty ratio of the two MOS tubes in each group of MOS tube units is adjusted to control the size of the three-phase alternating current output by the energy conversion unit.

[0047] Preferably, it includes:

[0048] The primary pin 1 of the first common-mode transformer is connected to the source of the first MOS tube in the third bridge arm, and the primary pin 2 is connected to the first phase input terminal of the three-phase motor; the secondary pin 3 is connected to the negative electrode of the battery, the secondary pin 4 is connected to the anode of the first secondary diode, and the cathode of the first secondary diode is connected to the positive electrode of the battery;

[0049] The primary pin 1 of the second common-mode transformer is connected to the source of the first MOS tube in the second bridge arm, and the primary pin 2 is connected to the second phase input terminal of the three-phase motor; the secondary pin 3 is connected to the negative electrode of the battery, the secondary pin 4 is connected to the anode of the second secondary diode, and the cathode of the second secondary diode is connected to the positive electrode of the battery;

[0050] The primary pin 1 of the third common-mode transformer is connected to the source of the first MOS tube in the first bridge arm, and the primary pin 2 is connected to the third phase input terminal of the three-phase motor; the secondary pin 3 is connected to the negative electrode of the battery, and the secondary pin 4 is connected to the anode of the third secondary diode, and the cathode of the third secondary diode is connected to the positive electrode of the battery.

[0051] The above technical solution of the present invention has the following beneficial effects compared with the prior art:

[0052] The energy feedback circuit of the heavy-load electric engineering vehicle described in the present invention is equipped with three common-mode transformers between the energy conversion unit and the three-phase motor, the primary sides of the three common-mode transformers are respectively arranged on the connection lines between the energy conversion unit and the three-phase input ends of the three-phase motor, and the secondary sides are connected in parallel to the two ends of the battery through diodes; when it is necessary to reduce the actual motor speed of the three-phase motor, the three-phase feedback voltage generated by the three-phase motor is respectively fed back to the battery through the three common-mode transformers to charge the battery, thereby realizing the feedback of excess energy at the three-phase motor, and using the feedback energy to charge the battery, saving power resources, and avoiding the accumulation of feedback energy at the two ends of the power device and one side of the circuit breaker, thereby avoiding damage to the circuit breaker and the power device, protecting the circuit, and improving the service life and safety of the heavy-load electric engineering vehicle.

[0053] At the same time, the present invention sets a current control unit with an adjustable equivalent resistance between the positive electrode of the battery and the circuit breaker, and adjusts the equivalent resistance of the current control unit according to the actual motor speed of the three-phase motor and the preset speed under different operating conditions, so as to more quickly adjust the three-phase alternating current output by the control unit, so as to further adjust the actual motor speed of the three-phase motor, so that the actual motor speed reaches the preset speed as soon as possible, and completes the change of the operating state of the heavy-load engineering vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

[0055] Figure 1 This is a schematic diagram of the traditional working circuit of a heavy-load electric engineering vehicle;

[0056] Figure 2 It is a circuit diagram of the energy feedback circuit of the heavy-load electric engineering vehicle provided by the present invention;

[0057] Figure 3It is a schematic diagram of the connection relationship of the energy feedback circuit of a large-load electric engineering vehicle based on the energy conversion unit provided by the present invention;

[0058] Figure 4 It is a connection diagram of an energy feedback circuit based on a current control unit provided by the present invention;

[0059] Figure 5 It is a specific circuit diagram of the energy feedback circuit based on the current control unit provided by the present invention. DETAILED DESCRIPTION

[0060] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0061] Heavy-load engineering vehicles are electrically driven, with high battery charging and discharging efficiency, abundant raw materials, low cost, and more environmentally friendly and pollution-free than traditional diesel engineering vehicles. However, their shortcomings are equally obvious. When heavy-load electric engineering vehicles need to brake quickly, the motor will inevitably have a power generation process, that is, the motor rotor is dragged by an external force or maintained by the load's own rotational inertia, so that the actual speed of the motor is greater than the synchronous speed output by the inverter. The excess electrical energy generated by the motor will be stored in the DC bus filter capacitor of the inverter; if this part of the energy is not consumed, the DC bus voltage will rise rapidly, affecting the normal operation of the inverter. Therefore, the present invention realizes the consumption and reuse of feedback electrical energy by changing the connection relationship in the drive circuit and adding a common-mode transformer.

[0062] Reference Figure 2 As shown in the figure, the circuit diagram of the energy feedback circuit of the heavy-load electric engineering vehicle provided by the present invention includes:

[0063] A circuit breaker, one end of which is connected to the positive terminal of the battery;

[0064] A DC bus filter capacitor, one end of which is connected to the other end of the circuit breaker, and the other end of which is connected to the negative electrode of the battery;

[0065] An energy conversion unit is connected in parallel to both ends of the DC bus filter capacitor to convert the DC power output by the battery into three-phase AC power, and output it to the three-phase motor through the three-phase output terminal;

[0066] A first common-mode transformer, wherein the primary side pin 1 is connected to the first phase output terminal of the energy conversion unit, the primary side pin 2 is connected to the first phase input terminal of the three-phase motor, the secondary side pin 3 is connected to the negative electrode of the battery, the secondary side pin 4 is connected to the anode of the first secondary side diode, and the cathode of the first secondary side diode is connected to the positive electrode of the battery;

[0067] A second common-mode transformer, wherein the primary side pin 1 is connected to the second phase output terminal of the energy conversion unit, the primary side pin 2 is connected to the second phase input terminal of the three-phase motor, the secondary side pin 3 is connected to the negative electrode of the battery, the secondary side pin 4 is connected to the anode of the second secondary side diode, and the cathode of the second secondary side diode is connected to the positive electrode of the battery;

[0068] A third common-mode transformer, wherein the primary side pin 1 is connected to the third-phase output terminal of the energy conversion unit, the primary side pin 2 is connected to the third-phase input terminal of the three-phase motor, the secondary side pin 3 is connected to the negative electrode of the battery, the secondary side pin 4 is connected to the anode of the third secondary diode, and the cathode of the third secondary diode is connected to the positive electrode of the battery;

[0069] The control unit is communicatively connected with the energy conversion unit. When the actual motor speed of the three-phase motor needs to be reduced, the control unit is used to control the duty cycle of multiple MOS tubes in the energy conversion unit, so that the current value of the three-phase alternating current output by the energy conversion unit is reduced and then input into the three-phase motor. The three-phase feedback voltage generated by the three-phase motor is fed back to the battery through three common-mode transformers respectively to charge the battery.

[0070] Specifically, when the actual motor speed of the three-phase motor needs to be reduced, the control unit is used to control the duty cycle of multiple MOS tubes in the energy conversion unit, so that the current value of the three-phase alternating current output by the energy conversion unit is reduced, so that the actual motor speed of the three-phase motor is reduced to the first preset speed. At this time:

[0071] The current flowing through the primary sides of the first common-mode transformer, the second common-mode transformer and the third common-mode transformer is reduced;

[0072] In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side 2 pin and the secondary side 4 pin is positive;

[0073] In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side pin 1 and the secondary side pin 3 is negative;

[0074] The secondary diodes of the first common-mode transformer, the second common-mode transformer and the third common-mode transformer are all forward-connected. Based on the electromagnetic characteristics of the inductance in the common-mode transformer, a reverse feedback current is generated and fed back to the battery through the common-mode transformer to charge the battery.

[0075] In an embodiment of the present invention, situations in which the actual motor speed of the three-phase motor needs to be reduced include: a heavy-load engineering vehicle shuts off the circuit breaker to stop running, emergency braking, and deceleration; when the heavy-load engineering vehicle shuts off the circuit breaker to stop running and emergency braking, the first preset speed is 0; when the heavy-load engineering vehicle decelerates, the first preset speed is greater than or equal to 0 and less than or equal to the actual motor speed of the three-phase motor.

[0076] Specifically, the control unit also includes using the control unit to control the duty cycle of multiple MOS tubes in the energy conversion unit when it is necessary to increase the actual motor speed of the three-phase motor, so that the current value of the three-phase alternating current output by the energy conversion unit increases and is input into the three-phase motor. The electrical energy of the three-phase alternating current is converted into mechanical energy of the three-phase motor, driving the three-phase motor to accelerate.

[0077] When the actual motor speed of the three-phase motor needs to be increased, the control unit is used to control the duty cycle of multiple MOS tubes in the energy conversion unit, so that the current value of the three-phase alternating current output by the energy conversion unit increases and is input into the three-phase motor, so that the actual motor speed of the three-phase motor increases to the second preset speed. At this time:

[0078] The current flowing through the primary sides of the first common mode transformer, the second common mode transformer and the third common mode transformer increases;

[0079] In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side pin 1 and the secondary side pin 3 is positive;

[0080] In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side 2 pin and the secondary side 4 pin is negative;

[0081] The secondary diodes of the first common-mode transformer, the second common-mode transformer and the third common-mode transformer are all reversely connected, and the three-phase AC current is converted into mechanical energy after entering the three-phase motor without energy feedback.

[0082] In this embodiment, the situations where the actual motor speed of the three-phase motor needs to be increased include starting and accelerating operation of a heavy-load engineering vehicle.

[0083] Reference Figure 3 As shown, it is a schematic diagram of the connection relationship of the energy feedback circuit of a large-load electric engineering vehicle based on the energy conversion unit provided by the present invention;

[0084] The energy conversion unit comprises an upper bridge arm and a lower bridge arm;

[0085] The upper bridge arm comprises:

[0086] A first MOS tube, a drain of which is connected to the other end of the circuit breaker, and a gate of which is connected to the control unit;

[0087] a first body diode connected in parallel to both ends of the first MOS tube, with an anode connected to the source of the first MOS tube and a cathode connected to the drain of the first MOS tube;

[0088] A third MOS tube, a drain of which is connected to the other end of the circuit breaker, and a gate of which is connected to the control unit;

[0089] A third body diode is connected in parallel to both ends of the third MOS tube, an anode of the third body diode is connected to the source of the third MOS tube, and a cathode of the third body diode is connected to the drain of the third MOS tube;

[0090] a fifth MOS tube, a drain of which is connected to the other end of the circuit breaker, and a gate of which is connected to the control unit;

[0091] a fifth body diode, connected in parallel to both ends of the fifth MOS tube, with an anode connected to the source of the fifth MOS tube and a cathode connected to the drain of the fifth MOS tube;

[0092] The lower bridge arm comprises:

[0093] A second MOS tube, whose drain is connected to the source of the first MOS tube, and the connection point serves as the third output end of the energy conversion unit; whose source is connected to the negative electrode of the battery, and whose gate is connected to the control unit;

[0094] a second body diode connected in parallel to both ends of the second MOS tube, with an anode connected to the source of the second MOS tube and a cathode connected to the drain of the second MOS tube;

[0095] A fourth MOS tube, whose drain is connected to the source of the third MOS tube, and the connection point serves as the second output end of the energy conversion unit; whose source is connected to the negative electrode of the battery, and whose gate is connected to the control unit;

[0096] a fourth body diode, connected in parallel to both ends of the fourth MOS tube, with an anode connected to the source of the fourth MOS tube and a cathode connected to the drain of the fourth MOS tube;

[0097] A sixth MOS tube, whose drain is connected to the source of the fifth MOS tube, and the connection point serves as the first output end of the energy conversion unit; whose source is connected to the negative electrode of the battery, and whose gate is connected to the control unit;

[0098] A sixth body diode is connected in parallel to both ends of the sixth MOS tube, an anode of the sixth body diode is connected to the source of the sixth MOS tube, and a cathode of the sixth body diode is connected to the drain of the sixth MOS tube.

[0099] Specifically, any MOS tube in the upper bridge arm of the energy conversion unit and any MOS tube in the lower bridge arm that does not belong to the same phase as the MOS tube are taken as a group of MOS tube units, and the duty ratio of the two MOS tubes in each group of MOS tube units is adjusted to control the size of the three-phase alternating current output by the energy conversion unit.

[0100] Specifically, in this embodiment, a bus voltage UDC is collected between the circuit breaker and the first MOS tube; the bus voltage UDC is a voltage value obtained by subtracting the voltage across the circuit breaker from the battery voltage, and is used to monitor the voltage on the DC bus in real time to ensure circuit safety.

[0101] Based on the above energy conversion unit, the connection relationship between the three common mode transformers and the energy conversion unit is respectively:

[0102] The primary pin 1 of the first common-mode transformer is connected to the source of the first MOS tube in the third bridge arm, and the primary pin 2 is connected to the first phase input terminal of the three-phase motor; the secondary pin 3 is connected to the negative electrode of the battery, the secondary pin 4 is connected to the anode of the first secondary diode, and the cathode of the first secondary diode is connected to the positive electrode of the battery;

[0103] The primary pin 1 of the second common-mode transformer is connected to the source of the first MOS tube in the second bridge arm, and the primary pin 2 is connected to the second phase input terminal of the three-phase motor; the secondary pin 3 is connected to the negative electrode of the battery, the secondary pin 4 is connected to the anode of the second secondary diode, and the cathode of the second secondary diode is connected to the positive electrode of the battery;

[0104] The primary pin 1 of the third common-mode transformer is connected to the source of the first MOS tube in the first bridge arm, and the primary pin 2 is connected to the third phase input terminal of the three-phase motor; the secondary pin 3 is connected to the negative electrode of the battery, and the secondary pin 4 is connected to the anode of the third secondary diode, and the cathode of the third secondary diode is connected to the positive electrode of the battery.

[0105] The energy feedback circuit of the heavy-load electric engineering vehicle described in the present invention is equipped with three common-mode transformers between the energy conversion unit and the three-phase motor, the primary sides of the three common-mode transformers are respectively arranged on the connection lines between the energy conversion unit and the three-phase input ends of the three-phase motor, and the secondary sides are connected in parallel to the two ends of the battery through diodes; when it is necessary to reduce the actual motor speed of the three-phase motor, the three-phase feedback voltage generated by the three-phase motor is respectively fed back to the battery through the three common-mode transformers to charge the battery, thereby realizing the feedback of excess energy at the three-phase motor, and using the feedback energy to charge the battery, saving power resources, and avoiding the accumulation of feedback energy at the two ends of the power device and one side of the circuit breaker, thereby avoiding damage to the circuit breaker and the power device, protecting the circuit, and improving the service life and safety of the heavy-load electric engineering vehicle.

[0106] Based on the above embodiment, in the embodiment of the present invention, a current control unit with adjustable equivalent resistance can also be used to control the magnitude of the three-phase current output by the energy conversion unit. The current control unit with adjustable equivalent resistance includes a plurality of resistors connected in series, the free end of the first resistor in series is connected to the positive electrode of the battery, and the free end of the last resistor in series is connected to one end of the circuit breaker; each resistor is connected in parallel with a switch, and the control unit is connected to all switches in communication, and the equivalent resistance of the current control unit is adjusted by controlling the on and off of the switch, so as to adjust the magnitude of the current of the direct current flowing into the energy conversion unit.

[0107] Reference Figure 4 The figure shows the energy feedback circuit connection diagram based on the current control unit; refer to Figure 5As shown, it is a specific circuit diagram of the energy feedback circuit based on the current control unit; Figure 4 and Figure 5 It can be seen that the present invention utilizes a current control unit with an adjustable equivalent resistance to adjust the equivalent resistance of the current control unit according to the actual motor speed of the three-phase motor and the preset speed under different operating conditions, thereby realizing the regulation of the three-phase alternating current output by the control unit, so as to further adjust the actual motor speed of the three-phase motor, so that the actual motor speed reaches the preset speed as soon as possible, thereby completing the change of the operating state of the heavy-load engineering vehicle.

[0108] Based on the above embodiments, in the embodiments of the present invention, referring to Figure 1 and Figure 2 As shown, the present invention adds common mode transformers T1, T2, T3, and secondary diodes D7, D8, D9 to the traditional circuit; the specific circuit connection relationship includes:

[0109] The positive electrode B+ of the battery is connected to one end of the circuit breaker, the other end of the circuit breaker is connected to one end of the DC bus filter capacitor C1, and is connected to the drain of the first MOS tube Z1, the cathode of the body diode D2 of the first MOS tube Z1, the drain of the third MOS tube Z3, the cathode of the body diode D4 of the third MOS tube Z3, the drain of the fifth MOS tube Z5, and the cathode of the body diode D5 of the fifth MOS tube Z5;

[0110] The source of the first MOS tube Z1 is connected to the anode of D2, the drain of the second MOS tube Z2, the cathode of D1, and the pin 1 of the third common mode transformer T3;

[0111] The source of the third MOS tube Z3 is connected to the anode of D4, the drain of the fourth MOS tube Z4, the cathode of D3, and the pin 1 of the second common mode transformer T2;

[0112] The source of the fifth MOS tube Z5 is connected to the anode of D5, the drain of the sixth MOS tube Z6, the cathode of D6, and the pin 1 of the first common mode transformer T1;

[0113] The negative electrode B- of the battery is connected to the other end of the DC bus filter capacitor C1, the source of the second MOS tube Z2, the anode of D1, the source of the fourth MOS tube Z4, the anode of D3, the source of the sixth MOS tube Z6, and the anode of D6;

[0114] Pin 2 of the first common mode transformer T1 is connected to the first phase input terminal of the three-phase motor; Pin 2 of the second common mode transformer T2 is connected to the second phase input terminal of the three-phase motor; Pin 2 of the third common mode transformer T3 is connected to the third phase input terminal of the three-phase motor;

[0115] Pin 3 of the first common-mode transformer T1 is connected to pin 3 of the second common-mode transformer T2, pin 3 of the third common-mode transformer T3, and the negative electrode B- of the battery;

[0116] The 4th pin of the first common mode transformer T1 is connected to the anode of the diode D7, and the cathode of D7 is connected to the positive electrode B+ of the battery; the 4th pin of the second common mode transformer T2 is connected to the anode of the diode D8, and the cathode of D8 is connected to the positive electrode B+ of the battery; the 4th pin of the third common mode transformer T3 is connected to the anode of the diode D9, and the cathode of D9 is connected to the positive electrode B+ of the battery;

[0117] The gates of the first MOS tube Z1, the second MOS tube Z2, the third MOS tube Z3, the fourth MOS tube Z4, the fifth MOS tube Z5 and the sixth MOS tube Z6 are respectively connected to the control unit.

[0118] Specifically, based on the above connection relationship, in the embodiment of the present invention, the circuit states during normal operation, emergency stop and shutdown of the circuit breaker are respectively:

[0119] ①The control unit controls the switches of power devices Z1, Z2, Z3, Z4, Z5, and Z6, and the directions of the three-phase currents U, V, and W output by the energy conversion unit, such as Figure 3 As shown, it flows into the motor and converts electrical energy into mechanical energy. According to the inductance characteristics, the primary side 1 pin of the first common mode transformer T1 is positive, the secondary side 3 pins and 1 pins are the same-name terminals, 3 pins are also positive, 4 pins are negative, and the diode is reversely connected. At this stage, no energy feedback is formed. All electrical energy is converted into mechanical energy

[0120] ② The control system controls the power devices Z1, Z2, Z3, Z4, Z5, and Z6 to stop suddenly. During this process, the motor currents U, V, and W are as follows: Figure 3 The reverse direction of the direction shown. According to the inductance characteristics, the inductance hinders the current change. The primary side 2 pin of the first common mode transformer T1 is positive, the same-name end 4 pin of 2 pin is positive, and the 3 pin is negative. The diode D7 is positively connected to charge the battery and feed the energy back to the battery. In this process, part of the energy output by the battery is fed back to the battery through the transformer without passing through the circuit breaker, reducing the current impact on the circuit breaker and reducing the loss. Similarly, transformers T2 and T3 charge the battery, reduce the current impact on the circuit breaker, and reduce the loss.

[0121] ③ During the actual operation of heavy-load electric engineering vehicles, due to emergencies and safety considerations, the circuit breaker needs to be turned off. During this process, the currents U, V, and W flowing through the motor are weakened. According to the inductance characteristics, the inductance hinders the current change. The primary side 2 pin of the first common-mode transformer T1 is positive, the same-name end 4 pin of 2 pin is positive, and the 3 pin is negative. The diode D7 is positively connected, and the first common-mode transformer T1 charges the battery. Similarly, transformers T2 and T3 charge the battery, and the feedback energy flows into the battery to avoid energy loss. At the same time, the feedback energy is avoided from being added to both ends of the power device and the circuit breaker, reducing the voltage stress of the power device and the circuit breaker.

[0122] In summary, when heavy-load engineering vehicles stop suddenly or encounter unexpected situations, the circuit breaker is cut off and the energy feedback circuit can feed the feedback energy back to the battery, preventing the power devices and circuit breakers from being subjected to excessive voltage stress and reducing power consumption.

[0123] Specifically, the control signal of the control unit to the power devices Z1, Z2, Z3, Z4, Z5, and Z6 is a square wave with a fixed period and an adjustable duty cycle. The product of the fixed period and the duty cycle is the corresponding MOS conduction time. The magnitude of the current flowing into the motor is controlled by controlling the conduction time of a group of MOS on the upper and lower bridge arms that are not on the same phase. According to the formula , Indicates the motor inductance, which is a fixed value; Indicates the MOS conduction time, It represents the current corresponding to the on-time. The change of on-time is proportional to the change of current. In this process, the current flowing into the motor can be adjusted while adjusting the on-time of MOS.

[0124] In an embodiment of the present invention, there is also provided an application of the energy feedback circuit of a heavy-load electric engineering vehicle as described above in a heavy-load electric engineering vehicle drive circuit. By setting the energy feedback circuit provided in this embodiment in the heavy-load electric vehicle drive circuit, when it is necessary to reduce the actual motor speed of the three-phase motor, the three-phase feedback voltage generated by the three-phase motor is fed back to the battery through three common-mode transformers to charge the battery, which saves power resources and avoids the accumulation of feedback energy at both ends of the power device and one side of the circuit breaker, thereby avoiding damage to the circuit breaker and the power device, protecting the circuit, and improving the service life and safety of the heavy-load electric engineering vehicle.

[0125] The energy feedback circuit of the heavy-load electric engineering vehicle described in the present invention is equipped with three common-mode transformers between the energy conversion unit and the three-phase motor, the primary sides of the three common-mode transformers are respectively arranged on the connection lines between the energy conversion unit and the three-phase input ends of the three-phase motor, and the secondary sides are connected in parallel to the two ends of the battery through diodes; when it is necessary to reduce the actual motor speed of the three-phase motor, the three-phase feedback voltage generated by the three-phase motor is respectively fed back to the battery through the three common-mode transformers to charge the battery, thereby realizing the feedback of excess energy at the three-phase motor, and using the feedback energy to charge the battery, saving power resources, and avoiding the accumulation of feedback energy at the two ends of the power device and one side of the circuit breaker, thereby avoiding damage to the circuit breaker and the power device, protecting the circuit, and improving the service life and safety of the heavy-load electric engineering vehicle. At the same time, the present invention utilizes a current control unit with an adjustable equivalent resistance to adjust the equivalent resistance of the current control unit according to the actual motor speed of the three-phase motor and the preset speed under different operating conditions, thereby realizing the regulation of the three-phase alternating current output by the control unit, so as to further adjust the actual motor speed of the three-phase motor, so that the actual motor speed reaches the preset speed as soon as possible, thereby completing the change of the operating state of the heavy-load engineering vehicle.

[0126] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A large-load electric engineering vehicle energy feedback circuit, characterized in that: include: A circuit breaker, one end of which is connected to the positive terminal of the battery; A DC bus filter capacitor, one end of which is connected to the other end of the circuit breaker, and the other end of which is connected to the negative electrode of the battery; An energy conversion unit is connected in parallel to both ends of the DC bus filter capacitor to convert the DC power output by the battery into three-phase AC power, and output it to the three-phase motor through the three-phase output terminal; A first common-mode transformer, wherein the primary side pin 1 is connected to the first phase output terminal of the energy conversion unit, the primary side pin 2 is connected to the first phase input terminal of the three-phase motor, the secondary side pin 3 is connected to the negative electrode of the battery, the secondary side pin 4 is connected to the anode of the first secondary side diode, and the cathode of the first secondary side diode is connected to the positive electrode of the battery; A second common-mode transformer, wherein the primary side pin 1 is connected to the second phase output terminal of the energy conversion unit, the primary side pin 2 is connected to the second phase input terminal of the three-phase motor, the secondary side pin 3 is connected to the negative electrode of the battery, the secondary side pin 4 is connected to the anode of the second secondary side diode, and the cathode of the second secondary side diode is connected to the positive electrode of the battery; A third common-mode transformer, wherein the primary side pin 1 is connected to the third-phase output terminal of the energy conversion unit, the primary side pin 2 is connected to the third-phase input terminal of the three-phase motor, the secondary side pin 3 is connected to the negative electrode of the battery, the secondary side pin 4 is connected to the anode of the third secondary diode, and the cathode of the third secondary diode is connected to the positive electrode of the battery; The control unit is communicatively connected with the energy conversion unit. When the actual motor speed of the three-phase motor needs to be reduced, the control unit is used to control the duty ratio of multiple MOS tubes in the energy conversion unit, so that the current value of the three-phase alternating current output by the energy conversion unit is reduced and then input into the three-phase motor, so that the actual motor speed of the three-phase motor is reduced to a first preset speed. The three-phase feedback voltage generated by the three-phase motor is respectively fed back to the battery through three common-mode transformers to charge the battery. At this time: The current flowing through the primary sides of the first common-mode transformer, the second common-mode transformer and the third common-mode transformer is reduced; In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side 2 pin and the secondary side 4 pin is positive; In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side pin 1 and the secondary side pin 3 is negative; The secondary diodes of the first common-mode transformer, the second common-mode transformer and the third common-mode transformer are all forward-connected. Based on the electromagnetic characteristics of the inductance in the common-mode transformer, a reverse feedback current is generated and fed back to the battery through the common-mode transformer to charge the battery.

2. The energy feedback circuit for a heavy-load electric engineering vehicle according to claim 1 is characterized in that: The situations where the actual motor speed of the three-phase motor needs to be reduced include: shutting down the circuit breaker of a heavy-load engineering vehicle to stop running, emergency braking and deceleration; When a heavy-load engineering vehicle turns off the circuit breaker to stop running and performs emergency braking, the first preset speed is 0; When the heavy-load engineering vehicle decelerates, the first preset speed is greater than or equal to 0 and less than or equal to the actual motor speed of the three-phase motor.

3. The energy feedback circuit for a heavy-load electric engineering vehicle according to claim 1 is characterized in that: When the actual motor speed of the three-phase motor needs to be increased, the control unit is used to control the duty cycle of multiple MOS tubes in the energy conversion unit, so that the current value of the three-phase alternating current output by the energy conversion unit increases and is input into the three-phase motor. The electrical energy of the three-phase alternating current is converted into mechanical energy of the three-phase motor, driving the three-phase motor to accelerate.

4. The energy feedback circuit for a heavy-load electric engineering vehicle according to claim 3 is characterized in that: Situations where the actual motor speed of a three-phase motor needs to be increased include starting and accelerating operation of a heavy-load engineering vehicle.

5. The energy feedback circuit for a heavy-load electric engineering vehicle according to claim 3 is characterized in that: When the actual motor speed of the three-phase motor needs to be increased, the control unit is used to control the duty cycle of multiple MOS tubes in the energy conversion unit, so that the current value of the three-phase alternating current output by the energy conversion unit increases and is input into the three-phase motor, so that the actual motor speed of the three-phase motor increases to the second preset speed. At this time: The current flowing through the primary sides of the first common mode transformer, the second common mode transformer and the third common mode transformer increases; In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side pin 1 and the secondary side pin 3 is positive; In the first common mode transformer, the second common mode transformer and the third common mode transformer, the reference polarity of the same-name terminal formed by the primary side 2 pin and the secondary side 4 pin is negative; The secondary diodes of the first common-mode transformer, the second common-mode transformer and the third common-mode transformer are all reversely connected, and the three-phase AC current is converted into mechanical energy after entering the three-phase motor without energy feedback.

6. The energy feedback circuit for a heavy-load electric engineering vehicle according to claim 1 is characterized in that: It also includes a current control unit with adjustable equivalent resistance value; The current control unit with adjustable equivalent resistance includes multiple resistors connected in series, the free end of the first resistor in series is connected to the positive electrode of the battery, and the free end of the last resistor in series is connected to one end of the circuit breaker; each resistor is connected in parallel with a switch, and the control unit is communicatively connected with all the switches, and the equivalent resistance of the current control unit is adjusted by controlling the on and off of the switch, so as to adjust the current size of the direct current flowing into the energy conversion unit.

7. The energy feedback circuit for a heavy-load electric engineering vehicle according to claim 1 is characterized in that: The energy conversion unit comprises an upper bridge arm and a lower bridge arm; The upper bridge arm comprises: A first MOS tube, a drain of which is connected to the other end of the circuit breaker, and a gate of which is connected to the control unit; a first body diode connected in parallel to both ends of the first MOS tube, with an anode connected to the source of the first MOS tube and a cathode connected to the drain of the first MOS tube; A third MOS tube, a drain of which is connected to the other end of the circuit breaker, and a gate of which is connected to the control unit; A third body diode is connected in parallel to both ends of the third MOS tube, an anode of the third body diode is connected to the source of the third MOS tube, and a cathode of the third body diode is connected to the drain of the third MOS tube; a fifth MOS tube, a drain of which is connected to the other end of the circuit breaker, and a gate of which is connected to the control unit; a fifth body diode, connected in parallel to both ends of the fifth MOS tube, with an anode connected to the source of the fifth MOS tube and a cathode connected to the drain of the fifth MOS tube; The lower bridge arm comprises: A second MOS tube, whose drain is connected to the source of the first MOS tube, and the connection point serves as the third output end of the energy conversion unit; whose source is connected to the negative electrode of the battery, and whose gate is connected to the control unit; a second body diode connected in parallel to both ends of the second MOS tube, with an anode connected to the source of the second MOS tube and a cathode connected to the drain of the second MOS tube; A fourth MOS tube, whose drain is connected to the source of the third MOS tube, and the connection point serves as the second output end of the energy conversion unit; whose source is connected to the negative electrode of the battery, and whose gate is connected to the control unit; a fourth body diode, connected in parallel to both ends of the fourth MOS tube, with an anode connected to the source of the fourth MOS tube and a cathode connected to the drain of the fourth MOS tube; A sixth MOS tube, whose drain is connected to the source of the fifth MOS tube, and the connection point serves as the first output end of the energy conversion unit; whose source is connected to the negative electrode of the battery, and whose gate is connected to the control unit; A sixth body diode is connected in parallel to both ends of the sixth MOS tube, an anode of the sixth body diode is connected to the source of the sixth MOS tube, and a cathode of the sixth body diode is connected to the drain of the sixth MOS tube.

8. The energy feedback circuit for a heavy-load electric engineering vehicle according to claim 7 is characterized in that: Any MOS tube in the upper bridge arm of the energy conversion unit and any MOS tube in the lower bridge arm that does not belong to the same phase as the MOS tube are used as a group of MOS tube units, and the duty ratio of the two MOS tubes in each group of MOS tube units is adjusted to control the size of the three-phase alternating current output by the energy conversion unit.

9. The energy feedback circuit for a heavy-load electric engineering vehicle according to claim 7, characterized in that: include: The primary pin 1 of the first common-mode transformer is connected to the source of the first MOS tube in the third bridge arm, and the primary pin 2 is connected to the first phase input terminal of the three-phase motor; the secondary pin 3 is connected to the negative electrode of the battery, the secondary pin 4 is connected to the anode of the first secondary diode, and the cathode of the first secondary diode is connected to the positive electrode of the battery; The primary pin 1 of the second common-mode transformer is connected to the source of the first MOS tube in the second bridge arm, and the primary pin 2 is connected to the second phase input terminal of the three-phase motor; the secondary pin 3 is connected to the negative electrode of the battery, the secondary pin 4 is connected to the anode of the second secondary diode, and the cathode of the second secondary diode is connected to the positive electrode of the battery; The primary pin 1 of the third common-mode transformer is connected to the source of the first MOS tube in the first bridge arm, and the primary pin 2 is connected to the third phase input terminal of the three-phase motor; the secondary pin 3 is connected to the negative electrode of the battery, and the secondary pin 4 is connected to the anode of the third secondary diode, and the cathode of the third secondary diode is connected to the positive electrode of the battery.

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