A current sampling circuit and method for electric large construction machinery vehicles

Abstract

The present invention relates to the field of power electronics technology, and discloses a current sampling circuit and method applied to electric large engineering machinery vehicles. By adding secondary windings to three inductors in a three-phase motor, the three inductors are improved into three coupling transformers, so that when the direction, frequency and magnitude of the current flowing through the inductors in the three-phase motor change, the current is synchronously coupled to the corresponding secondary inductors, and the voltage signal induced by the secondary inductors of the coupling transformer in the three-phase motor is fed back to a control unit; based on the resistance value and voltage signal of the built-in resistor of the control unit, the induced current of the secondary inductor is calculated; the sampling current of the primary inductor is calculated by using the turns ratio of the primary inductor to the secondary inductor in the coupling transformer and the induced current of the secondary inductor. The present invention uses the method of increasing the secondary inductor, which has low cost, safe and reliable sampling, can avoid the component shedding caused by the electric large engineering machinery vehicle under harsh working conditions, and improves the stability and reliability of the sampling circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a current sampling circuit and method applied to electric large engineering machinery vehicles. Background Art

[0002] Large construction machinery vehicles are large in size, have complex working conditions, and carry heavy loads. They often use diesel as fuel. Traditional diesel engine construction machinery has low energy efficiency, large emissions, high costs, and large size. With the new round of energy revolution, various large-capacity, small-size, and low-cost batteries are being used on a large scale, and electric large construction machinery vehicles are becoming more and more popular.

[0003] The two core components of electric large-scale construction machinery vehicles are electric drive and motor; the electric drive is used to convert DC into AC to drive the motor, and the motor is used to convert electrical energy into mechanical energy; in the process of the electric drive controlling the motor, the motor provides temperature sampling signals, angle signals and input current to the electric drive, so that the electric drive can adjust according to external instructions based on the signals provided by the motor, and output signals to the motor to meet the requirements of the external instructions.

[0004] Reference Figure 1 As shown in the figure, it is a schematic diagram of the motor current collection circuit based on the traditional large engineering machinery vehicle drive circuit. At present, the electric drive mainly collects the motor current based on the following Figure 1 The circuit shown is used for collection. One method is to connect a resistor in series with the power device, collect the current passing through the MOS through the resistor, and then calculate the current flowing through the motor; this method is low-cost, but the resistor has high power consumption, low efficiency, and large size, and is not suitable for large current sampling. However, the motor current of large engineering machinery vehicles is often hundreds of amperes, so this method is not suitable for motor current collection of large engineering machinery vehicles. Another method is to connect a Hall sensor in series at the input end of the motor to directly sample the current flowing through the motor; this method can use the Hall sensor to sample large currents, and the sensor is small in size; but it is costly and not conducive to installation. Due to the complex working conditions of large electric mechanical engineering vehicles, the Hall sensor is very easy to fall off when the vehicle is in a bumpy state, causing accidents.

[0005] In summary, the existing motor current acquisition methods cannot be directly applied to the motor current acquisition of electric large engineering machinery vehicles because they cannot acquire large currents or are not suitable for the working environment of large engineering vehicles. Summary of the invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problem that the sampling circuit in the prior art is not suitable for large current sampling and cannot be directly applied to large electric engineering machinery vehicles.

[0007] In order to solve the above technical problems, the present invention provides a current sampling circuit applied to an electric large construction machinery vehicle, comprising:

[0008] Batteries;

[0009] The inverter has a positive input terminal connected to the positive terminal of the battery, a negative input terminal connected to the negative terminal of the battery, and a three-phase output terminal connected to the three-phase motor, and is used to convert the direct current output of the battery into three-phase alternating current output to the three-phase motor to drive the three-phase motor to rotate;

[0010] A three-phase motor comprising:

[0011] A first coupling transformer, wherein the pin 1 of the primary inductor is connected to the first phase output terminal of the inverter, and the pins 3 and 4 of the secondary inductor are both connected to the first input terminal of the control unit, so as to feed back the first induced voltage generated by the secondary inductor to the control unit;

[0012] A second coupling transformer, wherein the pin 1 of the primary inductor is connected to the second phase output terminal of the inverter, and the pins 3 and 4 of the secondary inductor are both connected to the second input terminal of the control unit, so as to feed back the second induced voltage generated by the secondary inductor to the control unit;

[0013] A third coupling transformer, wherein the primary inductor pin 1 is connected to the third phase output terminal of the inverter, the primary inductor pin 2 is connected to the primary inductor pin 2 of the first coupling transformer and the primary inductor pin 2 of the second coupling transformer, and the secondary inductor pins 3 and 4 are both connected to the third input terminal of the control unit, so as to feed back the third induced voltage generated by the secondary inductor to the control unit;

[0014] The control unit includes a current sampling module, which is used to calculate the induced current of the secondary inductor based on the induced voltage of the secondary inductor and the built-in resistance of the control unit in each coupling transformer, and calculate the sampling current of the primary inductor based on the induced current of the secondary inductor and the turns ratio of the coupling transformer, so as to obtain the three-phase sampling currents corresponding to the three coupling transformers.

[0015] Preferably, the control unit further includes a three-phase current unbalance management module, which is used to:

[0016] Compare whether the three-phase sampling currents obtained by the current sampling module are equal:

[0017] If the three-phase sampled currents are equal, the three-phase AC output of the inverter is balanced;

[0018] If the three-phase sampling currents are not equal, the average value of the three-phase sampling currents is calculated. Based on the difference between the three-phase sampling currents and the average value, the conduction time of the two MOS tubes in each group of full-bridge bevels in the inverter is adjusted respectively, so that the three-phase sampling currents are equal to the average value.

[0019] Preferably, the control unit further includes a current regulating module, which is used to compare the sampled current of the primary inductor with a preset current value, so as to adjust the duty cycle of multiple MOS tubes in the inverter based on the comparison result, and further adjust the current of the three-phase alternating current input to the three-phase motor, including:

[0020] When the sampled current of the primary inductor is greater than the preset current value, the speed of the three-phase motor needs to be reduced. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the inverter is controlled to be reduced, thereby reducing the size of the three-phase AC output by the inverter, thereby reducing the output energy of the three-phase motor;

[0021] When the sampled current of the primary inductor is equal to the preset current value, the control signal output by the control unit remains unchanged;

[0022] When the sampled current of the primary inductor is less than the preset current value, the speed of the three-phase motor needs to be increased. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the inverter is controlled to increase, thereby increasing the size of the three-phase AC power output by the inverter, thereby increasing the output energy of the three-phase motor.

[0023] Preferably, the inverter comprises:

[0024] The upper arm includes:

[0025] A first MOS tube, a drain of which is connected to the positive electrode of the battery, and a gate of which is connected to the output end of the control unit;

[0026] a first body diode, an anode of which is connected to the source of the first MOS transistor, and a cathode of which is connected to the drain of the first MOS transistor;

[0027] A second MOS tube, a drain of which is connected to the positive electrode of the battery, and a gate of which is connected to the output end of the control unit;

[0028] a second body diode, an anode of which is connected to the source of the second MOS transistor, and a cathode of which is connected to the drain of the second MOS transistor;

[0029] A third MOS tube, a drain of which is connected to the positive electrode of the battery, and a gate of which is connected to the output end of the control unit;

[0030] a third body diode, an anode of which is connected to the source of the third MOS tube, and a cathode of which is connected to the drain of the third MOS tube;

[0031] The lower bridge arm comprises:

[0032] a fourth MOS tube, whose source is connected to the negative electrode of the battery, whose drain is connected to the source of the first MOS tube, and whose gate is connected to the output end of the control unit;

[0033] a fourth body diode, an anode of which is connected to the source of the fourth MOS tube, and a cathode of which is connected to the drain of the fourth MOS tube;

[0034] a fifth MOS tube, whose source is connected to the negative electrode of the battery, whose drain is connected to the source of the second MOS tube, and whose gate is connected to the output end of the control unit;

[0035] a fifth body diode, an anode of which is connected to the source of the fifth MOS tube, and a cathode of which is connected to the drain of the fifth MOS tube;

[0036] a sixth MOS tube, whose source is connected to the negative electrode of the battery, whose drain is connected to the source of the third MOS tube, and whose gate is connected to the output end of the control unit;

[0037] A sixth body diode, an anode of which is connected to the source of the sixth MOS tube, and a cathode of which is connected to the drain of the sixth MOS tube.

[0038] Preferably, it also includes:

[0039] A temperature sensor is fixed inside the three-phase motor and is in communication connection with the control unit, and is used to collect the temperature inside the three-phase motor in real time and send it to the control unit so that the control unit can issue an over-temperature warning based on a preset temperature threshold;

[0040] The electrical angle sensor is fixed inside the three-phase motor and is in communication connection with the control unit for real-time acquisition of the electrical angle of the three-phase motor so that the control unit can issue a fault warning based on a preset electrical angle threshold.

[0041] This embodiment provides a current sampling method based on the current sampling circuit applied to an electric large construction machinery vehicle as described above, and for each coupler in a three-phase motor, includes:

[0042] Feeding back the voltage signal induced by the secondary inductance of the coupling transformer in the three-phase motor to the control unit;

[0043] Based on the resistance value and voltage signal of the built-in resistor of the control unit, the induced current of the secondary inductor is calculated;

[0044] The sampling current of the primary inductor is calculated by using the turns ratio of the primary inductor to the secondary inductor in the coupling transformer and the induced current of the secondary inductor.

[0045] Preferably, the sampled current of the primary inductance is calculated by utilizing the turns ratio of the primary inductance to the secondary inductance in the coupling transformer and the induced current of the secondary inductance, which is expressed as:

[0046] ;

[0047] in, Represents the sampling current of the primary inductor, represents the induced current of the secondary inductor, It represents the turns ratio of the primary inductance to the secondary inductance in the coupling transformer.

[0048] Preferably, after calculating the sampling current of the primary inductance, the method further includes comparing whether the three-phase sampling currents corresponding to the three coupling transformers are equal:

[0049] If the three-phase sampled currents are equal, the three-phase AC output of the inverter is balanced;

[0050] If the three-phase sampling currents are not equal, the average value of the three-phase sampling currents is calculated. Based on the difference between the three-phase sampling currents and the average value, the conduction time of the two MOS tubes in each group of full-bridge bevels in the inverter is adjusted respectively, so that the three-phase sampling currents are equal to the average value.

[0051] Preferably, after calculating the sampling current of the primary inductor, the method further includes adjusting the duty cycle of multiple MOS tubes in the inverter based on the relationship between the sampling current of the primary inductor and the preset current value to change the current value of the three-phase alternating current output by the inverter, including:

[0052] When the sampled current of the primary inductor is greater than the preset current value, the speed of the three-phase motor needs to be reduced. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the inverter is controlled to be reduced, thereby reducing the size of the three-phase AC output by the inverter, thereby reducing the output energy of the three-phase motor;

[0053] When the sampled current of the primary inductor is equal to the preset current value, the control signal output by the control unit remains unchanged;

[0054] When the sampled current of the primary inductor is less than the preset current value, the speed of the three-phase motor needs to be increased. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the inverter is controlled to increase, thereby increasing the size of the three-phase AC power output by the inverter, thereby increasing the output energy of the three-phase motor.

[0055] Preferably, it also includes:

[0056] Collect the real-time temperature inside the three-phase motor and compare it with the preset temperature threshold. If the real-time temperature exceeds the preset temperature threshold, an over-temperature warning is issued;

[0057] The real-time electrical angle of the three-phase motor is collected and compared with the preset electrical angle threshold. If the real-time electrical angle exceeds the preset electrical angle threshold, a fault warning is issued.

[0058] The above technical solution of the present invention has the following beneficial effects compared with the prior art:

[0059] The current sampling circuit applied to electric large engineering machinery vehicles described in the present invention is improved into three coupling transformers by adding secondary windings to the three inductors in the three-phase motor, so that when the direction, frequency and magnitude of the current flowing through the inductors in the three-phase motor change, it is synchronously coupled to the corresponding secondary inductors, and the secondary inductors send the induced voltage signal as feedback voltage to the control unit, so that the control unit calculates the induced current of the secondary inductors, and further calculates the sampling current of the primary inductors based on the turns ratio of the coupling transformer. The existing drive circuits of electric large engineering machinery vehicles mostly have the structure of inverters, three-phase motors and control units. The present invention only needs to add secondary inductors to the inductors in the three-phase motors based on the structure of the existing drive circuits, and convert them into coupling transformers to realize current sampling; and the coupling transformer has a low cost. By adding the secondary inductors, the sampling circuit based on the coupling transformer is fixed inside the three-phase motor, and the sampling is safe and reliable, and is not affected by the magnitude of the current. It can also sample large currents, and can avoid the component shedding caused by the electric large engineering machinery vehicles under harsh working conditions, thereby improving the stability and reliability of the sampling circuit;

[0060] After the three-phase sampling current is calculated based on the three coupling transformers, the present invention can also judge whether the three-phase alternating current output by the inverter is balanced, and adjust the conduction time of the MOS tube in the inverter according to the judgment result to balance the three-phase alternating current input to the three-phase motor, thereby improving the working efficiency of the three-phase motor and ensuring the safe and stable operation of the three-phase motor.

[0061] At the same time, the present invention can install a temperature sensor and an electrical angle sensor in a three-phase motor, which can be communicated with a control unit to provide over-temperature warning and abnormality warning without the need to design an additional circuit structure, thereby greatly improving the consistency of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] 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:

[0063] Figure 1 This is a schematic diagram of a motor current acquisition circuit based on a traditional large engineering machinery vehicle drive circuit;

[0064] Figure 2 This is a current sampling circuit diagram for electric large engineering machinery vehicles provided by the present invention;

[0065] Figure 3 is a schematic diagram of the inverter structure;

[0066] Figure 4 It is the electrical schematic diagram of the motor rotor;

[0067] Figure 5It is a wiring diagram of the coupling transformer provided by the present invention;

[0068] Figure 6 It is a complete circuit structure diagram of the current sampling circuit applied to electric large engineering machinery vehicles provided by the present invention. DETAILED DESCRIPTION

[0069] 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.

[0070] Reference Figure 2 As shown, the current sampling circuit diagram provided by the present invention for electric large engineering machinery vehicles includes:

[0071] Batteries;

[0072] The inverter has a positive input terminal connected to the positive terminal of the battery, a negative input terminal connected to the negative terminal of the battery, and a three-phase output terminal connected to the three-phase motor, and is used to convert the direct current output of the battery into three-phase alternating current output to the three-phase motor to drive the three-phase motor to rotate;

[0073] A three-phase motor comprising:

[0074] A first coupling transformer, wherein the pin 1 of the primary inductor is connected to the first phase output terminal of the inverter, and the pins 3 and 4 of the secondary inductor are both connected to the first input terminal of the control unit, so as to feed back the first induced voltage generated by the secondary inductor to the control unit;

[0075] A second coupling transformer, wherein the pin 1 of the primary inductor is connected to the second phase output terminal of the inverter, and the pins 3 and 4 of the secondary inductor are both connected to the second input terminal of the control unit, so as to feed back the second induced voltage generated by the secondary inductor to the control unit;

[0076] A third coupling transformer, wherein the primary inductor pin 1 is connected to the third phase output terminal of the inverter, the primary inductor pin 2 is connected to the primary inductor pin 2 of the first coupling transformer and the primary inductor pin 2 of the second coupling transformer, and the secondary inductor pins 3 and 4 are both connected to the third input terminal of the control unit, so as to feed back the third induced voltage generated by the secondary inductor to the control unit;

[0077] The control unit includes a current sampling module, which is used to calculate the induced current of the secondary inductor based on the induced voltage of the secondary inductor and the built-in resistance of the control unit in each coupling transformer, and calculate the sampling current of the primary inductor based on the induced current of the secondary inductor and the turns ratio of the coupling transformer, so as to obtain the three-phase sampling currents corresponding to the three coupling transformers.

[0078] In this embodiment, the control unit further includes a three-phase current unbalance management module, which is used to:

[0079] Compare whether the three-phase sampling currents obtained by the current sampling module are equal:

[0080] If the three-phase sampled currents are equal, the three-phase AC output of the inverter is balanced;

[0081] If the three-phase sampling currents are not equal, the average value of the three-phase sampling currents is calculated. Based on the difference between the three-phase sampling currents and the average value, the conduction time of the two MOS tubes in each group of full-bridge bevels in the inverter is adjusted respectively, so that the three-phase sampling currents are equal to the average value.

[0082] After the three-phase sampling current is calculated based on three coupling transformers, the present invention can also judge whether the three-phase alternating current output by the inverter is balanced, and adjust the conduction time of the MOS tube in the inverter according to the judgment result to balance the three-phase alternating current input to the three-phase motor, thereby improving the working efficiency of the three-phase motor and ensuring the safe and stable operation of the three-phase motor.

[0083] In this embodiment, the control unit further includes a current regulating module, which is used to compare the sampled current of the primary inductor with a preset current value, so as to adjust the duty cycle of multiple MOS tubes in the inverter based on the comparison result, and then adjust the current of the three-phase alternating current input to the three-phase motor, including:

[0084] When the sampled current of the primary inductor is greater than the preset current value, the speed of the three-phase motor needs to be reduced. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the inverter is controlled to be reduced, thereby reducing the size of the three-phase AC output by the inverter, thereby reducing the output energy of the three-phase motor;

[0085] When the sampled current of the primary inductor is equal to the preset current value, the control signal output by the control unit remains unchanged;

[0086] When the sampled current of the primary inductor is less than the preset current value, the speed of the three-phase motor needs to be increased. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the inverter is controlled to increase, thereby increasing the size of the three-phase AC power output by the inverter, thereby increasing the output energy of the three-phase motor.

[0087] Among them, in the control unit, the three-phase current unbalance management module and the current regulation module are both communicated with the current sampling module, so as to obtain the three-phase sampling current corresponding to the three coupling transformers and perform three-phase current unbalance management or current regulation.

[0088] Specifically, refer to Figure 3 As shown, it is a schematic diagram of the structure of an inverter; the inverter comprises:

[0089] The upper arm includes:

[0090] A first MOS tube, a drain of which is connected to the positive electrode of the battery, and a gate of which is connected to the output end of the control unit;

[0091] a first body diode, an anode of which is connected to the source of the first MOS transistor, and a cathode of which is connected to the drain of the first MOS transistor;

[0092] A second MOS tube, a drain of which is connected to the positive electrode of the battery, and a gate of which is connected to the output end of the control unit;

[0093] a second body diode, an anode of which is connected to the source of the second MOS transistor, and a cathode of which is connected to the drain of the second MOS transistor;

[0094] A third MOS tube, a drain of which is connected to the positive electrode of the battery, and a gate of which is connected to the output end of the control unit;

[0095] a third body diode, an anode of which is connected to the source of the third MOS tube, and a cathode of which is connected to the drain of the third MOS tube;

[0096] The lower bridge arm comprises:

[0097] a fourth MOS tube, whose source is connected to the negative electrode of the battery, whose drain is connected to the source of the first MOS tube, and whose gate is connected to the output end of the control unit;

[0098] a fourth body diode, an anode of which is connected to the source of the fourth MOS tube, and a cathode of which is connected to the drain of the fourth MOS tube;

[0099] a fifth MOS tube, whose source is connected to the negative electrode of the battery, whose drain is connected to the source of the second MOS tube, and whose gate is connected to the output end of the control unit;

[0100] a fifth body diode, an anode of which is connected to the source of the fifth MOS tube, and a cathode of which is connected to the drain of the fifth MOS tube;

[0101] a sixth MOS tube, whose source is connected to the negative electrode of the battery, whose drain is connected to the source of the third MOS tube, and whose gate is connected to the output end of the control unit;

[0102] A sixth body diode, an anode of which is connected to the source of the sixth MOS tube, and a cathode of which is connected to the drain of the sixth MOS tube.

[0103] Specifically, the two MOS tubes at the full-bridge oblique angle refer to a MOS tube in the upper bridge arm and another MOS tube in the lower bridge arm that is not on the same arm as the MOS tube; Figure 3In the embodiment, three groups of MOS tubes are included at full-bridge bevel angles, namely: a first MOS tube M1 and a fifth MOS tube M5, a second MOS tube M2 and a sixth MOS tube M6, and a third MOS tube M3 and a fourth MOS tube M4.

[0104] Specifically, the duty cycle of each group of two MOS tubes at the full-bridge bevel angle is proportional to the current size of the corresponding single-phase current controlled by it; therefore, by adjusting the duty cycle of the two MOS tubes at the full-bridge bevel angle, the size of each phase of the three-phase AC output by the inverter can be controlled.

[0105] In an embodiment of the present invention, the current sampling circuit further includes:

[0106] A temperature sensor is fixed inside the three-phase motor and is in communication connection with the control unit, and is used to collect the temperature inside the three-phase motor in real time and send it to the control unit so that the control unit can issue an over-temperature warning based on a preset temperature threshold;

[0107] The electrical angle sensor is fixed inside the three-phase motor and is in communication connection with the control unit for real-time acquisition of the electrical angle of the three-phase motor so that the control unit can issue a fault warning based on a preset electrical angle threshold.

[0108] The present invention can install a temperature sensor and an electrical angle sensor in a three-phase motor, which is communicatively connected with a control unit to provide over-temperature warning and abnormality warning without the need to design an additional circuit structure, thereby greatly improving the consistency of the product.

[0109] Specifically, the embodiment of the present invention is also provided with a safety device, whose input end is connected to the positive electrode of the battery, and whose output end is connected to the drain of the MOS tube in the upper bridge arm of the inverter and the negative electrode of the body diode, so as to perform overload protection and short circuit protection to ensure the safe and stable operation of the circuit.

[0110] The present invention replaces the three inductors in the original electrical structure of the motor with three coupling transformers, and feeds back the changes in the direction, frequency and size of the current flowing through the motor to the control unit after being amplified by the coupling transformer, so as to achieve the function of sampling the motor current; the coupling transformer has low cost and is fixed inside the motor as a sampling circuit, which is safe and reliable and avoids the separation of components caused by harsh working conditions.

[0111] Based on the above embodiment, in an embodiment of the present invention, based on the current sampling method of the current sampling circuit applied to the electric large engineering machinery vehicle as described above, current sampling is performed, and for each coupler in the three-phase motor, it includes:

[0112] Feeding back the voltage signal induced by the secondary inductance of the coupling transformer in the three-phase motor to the control unit;

[0113] Based on the resistance value and voltage signal of the built-in resistor of the control unit, the induced current of the secondary inductor is calculated;

[0114] The sampling current of the primary inductor is calculated by using the turns ratio of the primary inductor to the secondary inductor in the coupling transformer and the induced current of the secondary inductor.

[0115] Specifically, the three inductors in the motor are added with a secondary winding, and the original inductor is changed into a coupling transformer. The turns ratio of the coupling transformer is N, the ratio of the primary voltage to the secondary voltage is N, and the ratio of the primary current to the secondary current is the reciprocal of N. The primary current is converted by sampling the secondary current. , expressed as:

[0116] ;

[0117] in, represents the induced current of the secondary inductor, It represents the turns ratio of the primary inductance to the secondary inductance in the coupling transformer.

[0118] Specifically, after calculating the sampling current of the primary inductor, it also includes comparing whether the three-phase sampling currents corresponding to the three coupling transformers are equal:

[0119] If the three-phase sampled currents are equal, the three-phase AC output of the inverter is balanced;

[0120] If the three-phase sampling currents are not equal, the average value of the three-phase sampling currents is calculated. Based on the difference between the three-phase sampling currents and the average value, the conduction time of the two MOS tubes in each group of full-bridge bevels in the inverter is adjusted respectively, so that the three-phase sampling currents are equal to the average value.

[0121] Specifically, after calculating the sampling current of the primary inductor, the duty cycle of multiple MOS tubes in the inverter is adjusted based on the relationship between the sampling current of the primary inductor and the preset current value to change the current value of the three-phase alternating current output by the inverter, including:

[0122] When the sampled current of the primary inductor is greater than the preset current value, the speed of the three-phase motor needs to be reduced. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the inverter is controlled to be reduced, thereby reducing the size of the three-phase AC output by the inverter, thereby reducing the output energy of the three-phase motor;

[0123] When the sampled current of the primary inductor is equal to the preset current value, the control signal output by the control unit remains unchanged;

[0124] When the sampled current of the primary inductor is less than the preset current value, the speed of the three-phase motor needs to be increased. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the inverter is controlled to increase, thereby increasing the size of the three-phase AC power output by the inverter, thereby increasing the output energy of the three-phase motor.

[0125] Specifically, this embodiment collects the real-time temperature inside the three-phase motor and compares it with the preset temperature threshold. If the real-time temperature exceeds the preset temperature threshold, an over-temperature warning is issued; this embodiment collects the real-time electrical angle of the three-phase motor and compares it with the preset electrical angle threshold. If the real-time electrical angle exceeds the preset electrical angle threshold, a fault warning is issued.

[0126] Specifically, refer to Figure 4 The figure is a schematic diagram of the electrical structure of the motor rotor; the present invention is based on Figure 4 The structure of the secondary winding is added to transform the three inductors at the three-phase input end into three coupling transformers. Figure 5 As shown, it is a schematic diagram of the coupling transformer wiring. At this time, the primary inductance (pin 1 and pin 2) remains consistent with the original one, with fewer turns and smaller inductance, and can pass large current. The secondary inductance (pin 3 and pin 4) can pass small current and has more turns, which can amplify the current change of the primary inductance, and the amplification factor is the ratio of the number of turns of the secondary inductance to the primary inductance. By coupling the changes in the current frequency, amplitude and flow direction of the primary inductance to the secondary side, it is converted into a feedback signal and sent to the control unit, so that the control unit can determine the changes in the current frequency, amplitude and flow direction on the primary inductance according to the feedback signal, and after adjustment, the input current of the three-phase motor is adjusted.

[0127] Reference Figure 6 As shown, it is a complete circuit structure diagram of the current sampling circuit applied to electric large engineering machinery vehicles provided by this embodiment, including:

[0128] One end of the battery is connected to the fuse, and the other end is connected to one end of the inverter, using the battery to provide energy for the inverter;

[0129] The other end of the fuse is connected to the other end of the inverter. The three-phase output of the inverter is connected to the primary windings of the three coupling transformers respectively, including:

[0130] The first output U of the inverter is connected to the pin 1 of the primary winding of the first coupling transformer T1, and the pins 3 and 4 of T1 are connected to the control unit as a signal VF1;

[0131] The second output V of the inverter is connected to the pin 1 of the primary winding of the second coupling transformer T2, and the pins 3 and 4 of T2 are connected to the control unit as a signal VF2;

[0132] The third output W of the inverter is connected to the pin 1 of the primary winding of the third coupling transformer T3, and the pins 3 and 4 of T3 are connected to the control unit as a signal VF3;

[0133] The 2 pins of T1, T2 and T3 are connected together, so that the three signals VF1, VF2 and VF3 generated by the three-phase motor are given to the control unit, so that the control unit generates a control signal according to VF1, VF2 and VF3 to control multiple MOS tubes in the inverter;

[0134] Specifically, the first-phase current U flowing from the inverter into the three-phase motor enters the primary side of the first coupling transformer T1. Since the winding composed of pins 1 and 2 of T1 is the primary inductance L1, due to the inductance characteristics, pin 1 of T1 is positive and pin 2 is negative; pins 1 and 3 are the same-name terminals. After the transformer is coupled, pin 3 is positive and pin 4 is negative. The current flowing into the motor is converted into a voltage signal and fed back to the control unit; the first-phase feedback current U' flowing from the motor into the inverter is reversed in direction. Since the winding composed of pins 1 and 2 of T1 is the primary inductance L1, due to the inductance characteristics, pin 2 of T1 is positive and pin 1 is negative; pins 1 and 3 are the same-name terminals. After the transformer is coupled, pin 4 is positive and pin 3 is negative. The current flowing into the inverter is converted into a voltage signal and fed back to the inverter; as mentioned above, the currents flowing in and out can be converted into voltage signals and fed back to the control unit.

[0135] At the same time, the control unit of the embodiment of the present invention includes a current sampling module, a three-phase current imbalance control module and a current regulation module to realize the sampling, current imbalance control and current regulation of the three-phase current in the three-phase motor.

[0136] The current sampling circuit applied to electric large engineering machinery vehicles described in the present invention is improved into three coupling transformers by adding secondary windings to the three inductors in the three-phase motor, so that when the direction, frequency and magnitude of the current flowing through the inductors in the three-phase motor change, it is synchronously coupled to the corresponding secondary inductors, and the secondary inductors send the induced voltage signal as feedback voltage to the control unit, so that the control unit calculates the induced current of the secondary inductors, and further calculates the sampling current of the primary inductors based on the turns ratio of the coupling transformer. The existing driving circuits of large electric engineering machinery vehicles mostly have the structure of an inverter, a three-phase motor and a control unit. The present invention only needs to add a secondary inductance to the inductance in the three-phase motor based on the structure of the existing driving circuit, and modify it into a coupling transformer to realize current sampling. The coupling transformer has a low cost. By increasing the secondary inductance, the sampling circuit based on the coupling transformer is fixed inside the three-phase motor. The sampling is safe and reliable, and is not affected by the current size. It can also sample large currents. At the same time, it can avoid the component shedding caused by the large electric engineering machinery vehicle under harsh working conditions, thereby improving the stability and reliability of the sampling circuit. After the present invention calculates the three-phase sampling current based on three coupling transformers, it can also judge whether the three-phase alternating current output by the inverter is balanced, and adjust the conduction time of the MOS tube in the inverter according to the judgment result to make the three-phase alternating current input to the three-phase motor balanced, thereby improving the working efficiency of the three-phase motor and ensuring the safe and stable operation of the three-phase motor. At the same time, the present invention can install a temperature sensor and an electrical angle sensor in the three-phase motor, which are connected to the control unit for communication, and perform over-temperature warning and abnormal warning. No additional circuit structure needs to be designed, which greatly improves the consistency of the product.

[0137] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0138] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0139] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0140] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0141] 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 current sampling circuit applied to electric large construction machinery vehicles, characterized in that: include: Batteries; The inverter has a positive input terminal connected to the positive terminal of the battery, a negative input terminal connected to the negative terminal of the battery, and a three-phase output terminal connected to the three-phase motor, and is used to convert the direct current output of the battery into three-phase alternating current output to the three-phase motor to drive the three-phase motor to rotate; A three-phase motor comprising: A first coupling transformer, wherein the pin 1 of the primary inductor is connected to the first phase output terminal of the inverter, and the pins 3 and 4 of the secondary inductor are both connected to the first input terminal of the control unit, so as to feed back the first induced voltage generated by the secondary inductor to the control unit; A second coupling transformer, wherein the pin 1 of the primary inductor is connected to the second phase output terminal of the inverter, and the pins 3 and 4 of the secondary inductor are both connected to the second input terminal of the control unit, so as to feed back the second induced voltage generated by the secondary inductor to the control unit; A third coupling transformer, wherein the primary inductor pin 1 is connected to the third phase output terminal of the inverter, the primary inductor pin 2 is connected to the primary inductor pin 2 of the first coupling transformer and the primary inductor pin 2 of the second coupling transformer, and the secondary inductor pins 3 and 4 are both connected to the third input terminal of the control unit, so as to feed back the third induced voltage generated by the secondary inductor to the control unit; The control unit includes a current sampling module, which is used to calculate the induced current of the secondary inductor based on the induced voltage of the secondary inductor and the built-in resistance of the control unit in each coupling transformer, and calculate the sampling current of the primary inductor based on the induced current of the secondary inductor and the turns ratio of the coupling transformer, so as to obtain the three-phase sampling currents corresponding to the three coupling transformers.

2. The current sampling circuit for electric large construction machinery vehicles according to claim 1 is characterized in that: The control unit further includes a three-phase current unbalance management module for: Compare whether the three-phase sampling currents obtained by the current sampling module are equal: If the three-phase sampled currents are equal, the three-phase AC output of the inverter is balanced; If the three-phase sampling currents are not equal, the average value of the three-phase sampling currents is calculated. Based on the difference between the three-phase sampling currents and the average value, the conduction time of the two MOS tubes in each group of full-bridge bevels in the inverter is adjusted respectively, so that the three-phase sampling currents are equal to the average value.

3. The current sampling circuit for electric large construction machinery vehicles according to claim 1 is characterized in that: The control unit further includes a current regulating module, which is used to compare the sampled current of the primary inductor with a preset current value, so as to adjust the duty cycle of multiple MOS tubes in the inverter based on the comparison result, and further adjust the current of the three-phase alternating current input to the three-phase motor, including: When the sampled current of the primary inductor is greater than the preset current value, the output energy of the three-phase motor needs to be reduced. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the inverter is controlled to be reduced, thereby reducing the size of the three-phase AC output of the inverter and thus reducing the speed of the three-phase motor; When the sampled current of the primary inductor is equal to the preset current value, the control signal output by the control unit remains unchanged; When the sampled current of the primary inductor is less than the preset current value, the output energy of the three-phase motor needs to be increased. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the control inverter is increased, thereby increasing the size of the three-phase AC power output by the inverter and thereby increasing the speed of the three-phase motor.

4. The current sampling circuit for electric large construction machinery vehicles according to claim 1, characterized in that: The inverter comprises: The upper arm includes: A first MOS tube, a drain of which is connected to the positive electrode of the battery, and a gate of which is connected to the output end of the control unit; a first body diode, an anode of which is connected to the source of the first MOS transistor, and a cathode of which is connected to the drain of the first MOS transistor; A second MOS tube, a drain of which is connected to the positive electrode of the battery, and a gate of which is connected to the output end of the control unit; a second body diode, an anode of which is connected to the source of the second MOS transistor, and a cathode of which is connected to the drain of the second MOS transistor; A third MOS tube, a drain of which is connected to the positive electrode of the battery, and a gate of which is connected to the output end of the control unit; a third body diode, an anode of which is connected to the source of the third MOS tube, and a cathode of which is connected to the drain of the third MOS tube; The lower bridge arm comprises: a fourth MOS tube, whose source is connected to the negative electrode of the battery, whose drain is connected to the source of the first MOS tube, and whose gate is connected to the output end of the control unit; a fourth body diode, an anode of which is connected to the source of the fourth MOS tube, and a cathode of which is connected to the drain of the fourth MOS tube; a fifth MOS tube, whose source is connected to the negative electrode of the battery, whose drain is connected to the source of the second MOS tube, and whose gate is connected to the output end of the control unit; a fifth body diode, an anode of which is connected to the source of the fifth MOS tube, and a cathode of which is connected to the drain of the fifth MOS tube; a sixth MOS tube, whose source is connected to the negative electrode of the battery, whose drain is connected to the source of the third MOS tube, and whose gate is connected to the output end of the control unit; A sixth body diode, an anode of which is connected to the source of the sixth MOS tube, and a cathode of which is connected to the drain of the sixth MOS tube.

5. The current sampling circuit for electric large construction machinery vehicles according to claim 1, characterized in that: Also includes: A temperature sensor is fixed inside the three-phase motor and is in communication connection with the control unit, and is used to collect the temperature inside the three-phase motor in real time and send it to the control unit so that the control unit can issue an over-temperature warning based on a preset temperature threshold; The electrical angle sensor is fixed inside the three-phase motor and is in communication connection with the control unit for real-time acquisition of the electrical angle of the three-phase motor so that the control unit can issue a fault warning based on a preset electrical angle threshold.

6. A current sampling method based on the current sampling circuit applied to an electric large construction machinery vehicle according to any one of claims 1 to 5, characterized in that: For each coupler in a three-phase motor, include: Feeding back the voltage signal induced by the secondary inductance of the coupling transformer in the three-phase motor to the control unit; Based on the resistance value and voltage signal of the built-in resistor of the control unit, the induced current of the secondary inductor is calculated; The sampling current of the primary inductor is calculated by using the turns ratio of the primary inductor to the secondary inductor in the coupling transformer and the induced current of the secondary inductor.

7. The current sampling method according to claim 6, characterized in that: The sampled current of the primary inductor is calculated by using the turns ratio of the primary inductor to the secondary inductor in the coupling transformer and the induced current of the secondary inductor, which is expressed as: ； in, Represents the sampling current of the primary inductor, represents the induced current of the secondary inductor, It represents the turns ratio of the primary inductance to the secondary inductance in the coupling transformer.

8. The current sampling method according to claim 6, characterized in that: After calculating the sampling current of the primary inductance, it also includes comparing whether the three-phase sampling currents corresponding to the three coupling transformers are equal: If the three-phase sampled currents are equal, the three-phase AC output of the inverter is balanced; If the three-phase sampling currents are not equal, the average value of the three-phase sampling currents is calculated. Based on the difference between the three-phase sampling currents and the average value, the conduction time of the two MOS tubes in each group of full-bridge bevels in the inverter is adjusted respectively, so that the three-phase sampling currents are equal to the average value.

9. The current sampling method according to claim 6, characterized in that: After calculating the sampling current of the primary inductor, the duty cycle of multiple MOS tubes in the inverter is adjusted based on the relationship between the sampling current of the primary inductor and the preset current value to change the current value of the three-phase alternating current output by the inverter, including: When the sampled current of the primary inductor is greater than the preset current value, the speed of the three-phase motor needs to be reduced. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the inverter is controlled to be reduced, thereby reducing the size of the three-phase AC output by the inverter, thereby reducing the output energy of the three-phase motor; When the sampled current of the primary inductor is equal to the preset current value, the control signal output by the control unit remains unchanged; When the sampled current of the primary inductor is less than the preset current value, the speed of the three-phase motor needs to be increased. At this time, the duty cycle of each group of two MOS tubes at the full-bridge bevel in the inverter is controlled to increase, thereby increasing the size of the three-phase AC power output by the inverter, thereby increasing the output energy of the three-phase motor.

10. The current sampling method according to claim 6, characterized in that: Also includes: Collect the real-time temperature inside the three-phase motor and compare it with the preset temperature threshold. If the real-time temperature exceeds the preset temperature threshold, an over-temperature warning is issued; The real-time electrical angle of the three-phase motor is collected and compared with the preset electrical angle threshold. If the real-time electrical angle exceeds the preset electrical angle threshold, a fault warning is issued.

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