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CN110596445B - Electric vehicle current measuring method - Google Patents

  • ️Tue Oct 19 2021

CN110596445B - Electric vehicle current measuring method - Google Patents

Electric vehicle current measuring method Download PDF

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Publication number
CN110596445B
CN110596445B CN201910846177.6A CN201910846177A CN110596445B CN 110596445 B CN110596445 B CN 110596445B CN 201910846177 A CN201910846177 A CN 201910846177A CN 110596445 B CN110596445 B CN 110596445B Authority
CN
China
Prior art keywords
current
driving
period
controller
motor
Prior art date
2019-09-09
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Active
Application number
CN201910846177.6A
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Chinese (zh)
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CN110596445A (en
Inventor
刘峰
周继华
薛祖播
李钢
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Nanjing Kuailun Intelligent Technology Co Ltd
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Nanjing Kuailun Intelligent Technology Co Ltd
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2019-09-09
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2019-09-09
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2021-10-19
2019-09-09 Application filed by Nanjing Kuailun Intelligent Technology Co Ltd filed Critical Nanjing Kuailun Intelligent Technology Co Ltd
2019-09-09 Priority to CN201910846177.6A priority Critical patent/CN110596445B/en
2019-12-20 Publication of CN110596445A publication Critical patent/CN110596445A/en
2021-10-19 Application granted granted Critical
2021-10-19 Publication of CN110596445B publication Critical patent/CN110596445B/en
Status Active legal-status Critical Current
2039-09-09 Anticipated expiration legal-status Critical

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  • 238000000034 method Methods 0.000 title claims abstract description 15
  • 238000005070 sampling Methods 0.000 claims abstract description 12
  • 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 4
  • 150000004706 metal oxides Chemical class 0.000 claims abstract description 4
  • 239000004065 semiconductor Substances 0.000 claims abstract description 4
  • 238000001914 filtration Methods 0.000 claims abstract description 3
  • 239000000956 alloy Substances 0.000 description 8
  • 229910045601 alloy Inorganic materials 0.000 description 8
  • 238000010586 diagram Methods 0.000 description 3
  • 230000000694 effects Effects 0.000 description 2
  • 238000004519 manufacturing process Methods 0.000 description 2
  • 238000010923 batch production Methods 0.000 description 1
  • 230000009286 beneficial effect Effects 0.000 description 1
  • 238000001514 detection method Methods 0.000 description 1
  • 238000012986 modification Methods 0.000 description 1
  • 230000004048 modification Effects 0.000 description 1

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Current Or Voltage (AREA)

Abstract

The invention discloses a current measuring method of an electric vehicle, which comprises the following steps: step 1, using the internal resistance of an MOS (metal oxide semiconductor) tube of a lower bridge arm of a phase line of a driving motor as a phase line sampling resistor, reserving a minimum time gap in each driving period of the motor, configuring a three-phase driving configuration into a lower tube to be opened by a controller in the time gap, and ensuring that the phase line current can be read in each driving period; step 2, calculating the average current of each period: the time of driving the motor and not driving the motor is divided into two parts in each driving cycle, the effective output time of the battery is the time period of driving the motor, and the average current of each driving cycle is the current value of the current average of the effective output time period to one cycle time; and 3, filtering by using a digital filter to obtain the current average current value: and multiplying the internal resistance of the MOS tube by a scaling coefficient, and storing the scaling coefficient in the singlechip.

Description

Electric vehicle current measuring method

Technical Field

The invention belongs to the field of power devices of new energy automobiles and the field of control of permanent magnet motors, and particularly relates to a current measuring method of an electric vehicle.

Background

The electric bicycle adopts a three-phase permanent magnet brushless direct current motor, in order to realize three-phase reversing operation, a control design adopts a three-phase upper and lower bridge driving structure, each phase of the motor is driven by an upper bridge arm and a lower bridge arm, and each bridge arm at least comprises an N-channel MOS (metal oxide semiconductor) tube; the controller needs to know the three-phase line current in order to meet the requirement of vector control, and the controller and the motor are damaged if the phase line current is too large, so that the phase line current also needs to be known from the perspective of protecting the motor and the controller so as to control the phase line current within a certain range.

The method generally adopted is that an alloy sampling resistor is connected in series in a phase line current loop, the voltage drop proportional to the current is generated when the current flows through the resistor, the voltage drop voltage is amplified by an operational amplifier chip and then output to an AD port of a singlechip, and the current value can be calculated by reading the voltage drop value by the singlechip; the average current consumed by the controller must be limited within a certain range, otherwise, the motor and the controller are damaged due to excessive output power, and the battery is possibly damaged, so the controller must also know the consumed average current, a common method for detecting the average current is similar to a phase line current detection method, and a special alloy resistor is connected in series at the end to the ground of an average current loop to detect the average current.

Disclosure of Invention

Aiming at the technical problems, the invention discloses a current measuring method of an electric vehicle, which simplifies the design of a controller mainboard, reduces the number of components, increases the miniaturization space of the controller, reduces the cost and increases the easy productivity of the controller.

In order to achieve the purpose, the invention adopts the technical scheme that:

an electric vehicle current measuring method comprising the steps of:

step 1, using the internal resistance of the MOS tube of the lower bridge arm of the phase line of the driving motor as a phase line sampling resistor, and reserving a minimum time gap in each driving period of the motor, wherein the controller configures the three-phase driving into that the lower tube is opened, namely the MOS tube for sampling the phase line current is fully opened, thereby ensuring that the phase line current can be read in each driving period. Therefore, the MOS tube can replace a common alloy resistor, has no obvious influence on the performance, and achieves a good current control effect.

Step 2, calculating the average current of each period, specifically: the time of dividing each driving period into two parts of driving the motor and not driving the motor, the effective output time of the battery is the time period of driving the motor, the average current of each driving period is the current value of the current average of the effective output time period to one period time, and the calculation formula is as follows:

Iavg=Iphase×Ton÷Tperiod

wherein Iavg is average current, Iphase: phase line current, Ton: active drive time in drive cycle, Tperiod: a drive period.

And 3, filtering by using a digital filter to obtain the current average current value.

In order to obtain a more accurate average current value, a controller is internally provided with a calibration program, the calibration principle is that a scaling coefficient is multiplied by the internal resistance of an MOS tube, the coefficient is stored in a nonvolatile memory of a singlechip, and the coefficient can be kept after the calibration is finished. The voltage value representing the magnitude of the current read by the controller is formulated as follows:

Vad=I×Rmos×Aamp

vad: voltage value indicating the magnitude of current, I: the current value flowing through the MOS tube, Rmos: the internal resistance of the mos tube, Aamp, is a coefficient that varies with current.

The controller controls the current to be a voltage value that the control Vad does not exceed the set current value, and the final current changes when the Rmos changes in the same set voltage value, so that the actual current limit value can be adjusted by adjusting Rmos.

Furthermore, the controller is operated to a current limiting value during production test, an adjusting module is externally connected to a brake port of the controller, different signals are sent to the controller, a real current value is read through external equipment, the value of Rmos is adjusted until the real current value is compared with the current limiting value and falls into a preset current tolerance range, and the controller memorizes the resistance value in the mos tube. By adjusting the internal resistance of the mos transistor to an accurate value, not only the average current but also the phase current is calibrated, because only the phase current is accurate to the average current calculated on the basis.

The invention has the following beneficial effects: current sampling resistor string is more serious in current loop among the controller commonly used, and the non-alloy resistance scheme that this patent provided has increased the reliability of board, has improved energy efficiency, has reduced controller mainboard complexity, and the cost is reduced has increased the miniaturized space of controller, changes in batch production.

Drawings

Fig. 1 is a circuit diagram of a sampling circuit of the resistance current in a MOS tube of the method for measuring the current of an electric vehicle according to the embodiment of the present invention.

Fig. 2 is a controller current curve diagram of the electric vehicle current measuring method according to the embodiment of the invention.

Fig. 3 is a graph of phase line current for an embodiment of the present invention.

Detailed Description

In order to facilitate understanding of those skilled in the art, the present invention will be further described with reference to the following embodiments and accompanying drawings.

And (3) sampling the three-phase current to remove the alloy resistance, and using the internal resistance of an MOS (metal oxide semiconductor) tube of a lower bridge arm of a phase line of the driving motor as a phase line sampling resistance. The internal resistance of a common N-channel MOS tube is about 3-8 milliohms when the N-channel MOS tube is conducted, the internal resistance is equivalent to the resistance of a common alloy resistor for sampling phase line current, the internal resistance of the MOS tube is stable after the MOS tube is opened for a short period, the phase line current flowing through the MOS tube is read, the time of about 100 nanoseconds for just opening is avoided, the state of the MOS tube is just switched from closing to opening in the period, the voltage has short jitter, the flowing current cannot be correctly reflected in the period, and the flowing current can be correctly reflected by the voltage drop on the MOS tube after the unstable period is avoided; the driving period of the motor is usually about 64us, a minimum time gap is ensured to be reserved in each period, the controller configures the three-phase driving to open the lower tube in the time gap, namely the MOS tube for sampling the phase line current is fully opened, and the phase line current can be read in each driving period, so that the MOS tube can replace a common alloy resistor, the performance is not obviously affected, and a good current control effect is achieved, and the partial circuit diagram is shown in fig. 1.

The average current in the scheme of the patent does not need to be sampled by an independent alloy resistor, but is calculated by the phase line current obtained in the previous step, the calculation principle is that the time of driving the motor and the time of not driving the motor are divided into two parts in each driving period, the effective output time of the battery is the time period of driving the motor, the average current in each driving period is the current value of the current average in the effective output time period to one period time, and the calculation formula is as follows:

Iavg=Iphase×Ton÷Tperiod

iavg average current, Iphase: phase line current, Ton: active drive time in drive cycle, Tperiod: a drive period.

The average current of each period is calculated and then filtered by a digital filter to obtain the current average current value.

In order to obtain a more accurate average current value, a controller is internally provided with a calibration program, the calibration principle is that a scaling coefficient is multiplied by the internal resistance of an MOS tube, the coefficient is stored in a nonvolatile memory of a singlechip, and the coefficient can be kept after the calibration is finished. The voltage value representing the magnitude of the current read by the controller is formulated as follows:

Vad=I×Rmos×Aamp

vad: voltage value indicating the magnitude of current, I: the current value flowing through the MOS tube, Rmos: internal resistance of mos tube.

The controller controls the current to be a voltage value that the control Vad does not exceed the set current value, and the final current changes when the Rmos changes in the same set voltage value, so that the actual current limit value can be adjusted by adjusting Rmos.

The method comprises the steps that a controller is operated to a current limiting value during production test, an adjusting module is externally connected to a brake port of the controller, the adjusting module is provided with two buttons, different signals are respectively sent to the controller when the two button modules are pressed down, a tester reads a real current value through external equipment, if the real current value exceeds a preset current tolerance range and is normally set to be plus or minus 0.5A, the buttons respectively representing larger or smaller actual current on the external module are pressed down, the modules send corresponding signals to the controller, the controller adjusts the value of Rmos after receiving the real current value, the actual average current limiting value can be immediately changed, the tester can immediately see current change on an external ammeter, the current limiting value is adjusted until meeting requirements, and the controller automatically memorizes the resistance value in a mos tube. By adjusting the internal resistance of the mos transistor to an accurate value, not only the average current but also the phase current is calibrated, because only the phase current is accurate to the average current calculated on the basis.

FIG. 2 is measured data of the dynamometer machine by the controller, wherein the green color is the average current curve, 14A is set, it can be seen that the set value is well reached, and the curve is relatively stable and good in performance in the whole dynamometer process.

Fig. 3 is a graph of two phase line currents, and it can be seen that the currents are better sinusoidal in shape, which illustrates that the phase line currents are accurately fed back by MOS transistor internal resistance sampling proposed by the patent, and the FOC control is better achieved.

The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical solution according to the technical idea of the present invention falls within the protection scope of the present invention.

Claims (2)

1. An electric vehicle current measuring method is characterized by comprising the following steps:

step 1, using the internal resistance of an MOS (metal oxide semiconductor) tube of a lower bridge arm of a phase line of a driving motor as a phase line sampling resistor, reserving a minimum time gap in each driving period of the motor, configuring a three-phase driving configuration into a lower tube to be opened by a controller in the time gap, and ensuring that the phase line current can be read in each driving period;

step 2, calculating the average current of each period, specifically: the time of dividing each driving period into two parts of driving the motor and not driving the motor, the effective output time of the battery is the time period of driving the motor, the average current of each driving period is the current value of the current average of the effective output time period to one period time, and the calculation formula is as follows:

Iavg=Iphase×Ton÷Tperiod;

wherein, Iavg: average current, Iphase: phase line current, Ton: active drive time in drive cycle, Tperiod: a drive period;

and 3, filtering by using a digital filter to obtain a current average current value, which specifically comprises the following steps:

the controller is internally provided with a calibration program, and the calibration principle is that a scaling coefficient is multiplied by the internal resistance of the MOS tube, the scaling coefficient is stored in a nonvolatile memory of the singlechip, and the scaling coefficient can be kept all the time after the calibration is finished; the voltage value representing the magnitude of the current read by the controller is formulated as follows:

Vad=I×Rmos×Aamp

vad: voltage value indicating the magnitude of current, I: the current value flowing through the MOS tube, Rmos: the internal resistance of the mos tube, Aamp, is a coefficient that varies with current;

the controller controls the current to be a voltage value that the control Vad does not exceed the set current value, and the final current changes when the Rmos changes in the same set voltage value, so that the actual current limit value can be adjusted by adjusting Rmos.

2. The electric vehicle current measuring method according to claim 1, characterized in that:

the method for determining the scaling coefficient comprises the following steps: the controller is operated to a current limiting value, an adjusting module is externally connected to a brake port of the controller, the adjusting module sends different signals to the controller, real current values are read through external equipment, Rmos values are adjusted until the real current values are within a preset current tolerance range compared with the current limiting value, and the controller memorizes the Rmos values.

CN201910846177.6A 2019-09-09 2019-09-09 Electric vehicle current measuring method Active CN110596445B (en)

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CN116599001B (en) * 2023-04-23 2024-08-20 珠海芯烨电子科技有限公司 Protection method and system for stepping motor of printing terminal

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GB9015199D0 (en) * 1990-07-10 1990-08-29 Polymeters Response Internatio Improvements in and relating to electricity meters using current transformers
US5488284A (en) * 1992-09-30 1996-01-30 Dallas Semiconductor Corporation Battery charger systems and methods
JPH09233827A (en) * 1996-02-26 1997-09-05 Matsushita Electric Ind Co Ltd Pwm inverter output circuit
CN202102070U (en) * 2011-05-12 2012-01-04 新安乃达驱动技术(上海)有限公司 Phase current sampling circuit for electric vehicle motor controller
CN102681531B (en) * 2012-05-10 2014-02-05 四川金网通电子科技有限公司 Method for implementing self-calibration of current-limiting current value of motor controller
CN105515472B (en) * 2016-01-25 2018-05-25 南京凌鸥创芯电子有限公司 Motor drive current detection circuit and control system
CN106370912B (en) * 2016-08-18 2020-02-11 李鹏 Method and system for improving current sampling precision of MOSFET (metal oxide semiconductor field effect transistor) tube and motor driving system
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