CN112737301B - Direct current bus capacitor discharging method - Google Patents
Direct current bus capacitor discharging method Download PDFInfo
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- CN112737301B CN112737301B CN202011596073.3A CN202011596073A CN112737301B CN 112737301 B CN112737301 B CN 112737301B CN 202011596073 A CN202011596073 A CN 202011596073A CN 112737301 B CN112737301 B CN 112737301B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
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Abstract
The invention provides a direct current bus capacitor discharging method, when a direct current bus capacitor has a discharging requirement, one switching tube on any one bridge arm of a bridge inverter is conducted, a first pulse width modulation signal is input to the other switching tube on the bridge arm, so that one switching tube is switched between a conducting state and a cut-off state, and because the switching tube is in a linear region in the switching process, great switching loss can be generated, energy on the direct current bus capacitor is dissipated on the switching tube in a hot mode, so that the bridge arm can quickly complete discharging of the direct current bus capacitor under the condition of not increasing extra cost.
Description
Technical Field
The invention relates to the technical field of new energy automobiles, in particular to a direct current bus capacitor discharging method.
Background
Along with the continuous promotion of new energy automobile power level, the voltage level of dc-to-ac converter dc bus also constantly improves, and higher dc bus voltage will certainly bring the safety problem, and too high dc bus voltage is a very big potential safety hazard under trouble and the shut down state. For example, after a vehicle breaks down, a vehicle owner may open the cover to repair the vehicle, and after the vehicle has a collision or other accidents, the high-voltage bus may be exposed, and under these working conditions, the vehicle owner has an opportunity to touch the direct-current bus, thereby causing personal safety problems. How to rapidly and safely complete the discharge of the direct current bus capacitor after the shutdown fault or even after an accident occurs is a problem that needs to be paid more and more attention and considered in the design of new energy vehicles. The traditional scheme has respective advantages and disadvantages, and no matter which scheme is selected, the application occasion, the discharge speed, the price cost and the like cannot be considered.
Disclosure of Invention
The invention aims to provide a direct current bus capacitor discharging method to solve the problem that the existing direct current bus capacitor discharging method cannot give consideration to application occasions, discharging speed and price cost.
In order to solve the above technical problem, the present invention provides a dc bus capacitor discharging method, where the dc bus capacitor is connected in parallel with an input end of a bridge inverter, the bridge inverter has at least one bridge arm, and each bridge arm has two switching tubes, and the dc bus capacitor discharging method includes:
when the direct current bus capacitor has a discharging requirement, one switching tube on any one bridge arm of the bridge inverter is conducted, and a first pulse width modulation signal is input to the other switching tube on the bridge arm so as to discharge the direct current bus capacitor.
Optionally, the dc bus capacitor discharging method further includes:
sequentially judging whether the bridge inverter and the direct current bus capacitor meet a discharging condition;
when the bridge inverter and the direct current bus capacitor both meet the discharge condition, one switching tube on any bridge arm of the bridge inverter is conducted, the first pulse width modulation signal is input to the other switching tube on the bridge arm, one switching tube on any bridge arm of the bridge inverter is conducted, and the first pulse width modulation signal is input to the other switching tube on the bridge arm.
Optionally, when the junction temperature of at least one switching tube on any bridge arm of the bridge inverter is less than or equal to a safe discharge junction temperature, it is determined that the bridge inverter meets the discharge condition, and the bridge arm that discharges the dc bus capacitor is the bridge arm in which the junction temperature of at least one switching tube is less than or equal to the safe discharge junction temperature.
Optionally, the step of determining whether the bridge inverter satisfies the discharging condition includes:
obtaining junction temperature of a switching tube on each bridge arm of the bridge inverter as comparison junction temperature, and comparing the comparison junction temperature of each bridge arm with the safe discharge junction temperature;
when the comparative junction temperature of any bridge arm is less than or equal to the safe discharge junction temperature, judging that the bridge inverter meets the discharge condition; and when the comparative junction temperatures of all the bridge arms are greater than the safe discharge junction temperature, after waiting for a first set time, judging that the comparative junction temperatures of all the bridge arms are less than or equal to the safe discharge junction temperature, and enabling the bridge inverter to meet the discharge condition.
Optionally, the dc bus capacitor is connected to a power module through a contactor, and when the contactor is not adhered, the dc bus capacitor meets a discharging condition.
Optionally, the step of determining whether the dc bus capacitor meets the discharging condition includes:
after the direct current bus capacitor is pre-discharged for a second set time, acquiring a voltage drop value of the direct current bus capacitor;
when the voltage drop value of the direct current bus capacitor is larger than or equal to a first threshold value, judging that the direct current bus capacitor meets a discharging condition; when the voltage drop value of the direct current bus capacitor is smaller than the first threshold value, the direct current bus capacitor is pre-discharged for the second set time again, and when the voltage drop value of the direct current bus capacitor is larger than or equal to the first threshold value, the direct current bus capacitor is judged to meet the discharge condition.
Optionally, when the number of times of pre-discharging of the dc bus capacitor is greater than a second threshold, the discharging process of the dc bus capacitor is ended.
Optionally, the step of pre-discharging the dc bus capacitor includes:
and enabling one switching tube on any one bridge arm of the bridge inverter to be conducted, and inputting a second pulse width modulation signal to the other switching tube on the bridge arm so as to pre-discharge the direct current bus capacitor.
Optionally, the first pwm signal and the second pwm signal are the same pwm signal.
Optionally, when the voltage drop value of the dc bus capacitor is smaller than the first threshold, the dc bus capacitor is pre-discharged after waiting for a third set time.
Optionally, the discharge time is calculated when it is determined whether the bridge inverter meets the discharge condition, and the discharge process of the dc bus capacitor is ended when the discharge time is greater than a third threshold.
In the direct current bus capacitor discharging method provided by the invention, when the direct current bus capacitor has a discharging requirement, one switching tube on any bridge arm of the bridge inverter is conducted, and a first pulse width modulation signal is input to the other switching tube on the bridge arm, so that one switching tube is switched between a conducting state and a switching-off state.
Drawings
FIG. 1 is a schematic diagram of an inverter DC bus system provided by an embodiment of the present invention;
fig. 2 is a flowchart of a dc bus capacitor discharging method according to an embodiment of the present invention;
fig. 3 is another flowchart of a dc bus capacitor discharging method according to an embodiment of the present invention;
c1-dc bus capacitance; k1-contactor; q1, Q2, Q3, Q4, Q5, Q6-switch tube; and E-a power supply module.
Detailed Description
The following three methods for discharging the direct current bus capacitor are provided:
firstly, completing discharge of a direct current bus capacitor by using a DC-DC converter: the discharge scheme has the advantages of high discharge speed and high discharge reliability. However, the application occasions have great limitations, the DC-DC converter is not standard, inverters connected with the direct current bus capacitor in many application occasions are not integrated with the DC-DC converter, and the direct current bus capacitor discharge can not be completed in the occasions.
Secondly, passive discharge is carried out on the direct current bus capacitor by utilizing a static load: the advantage of this discharge scheme is that it is low cost and simple to implement. However, because the static load also generates discharge loss during normal operation, the discharge power cannot be designed to be too large, so that the discharge speed of the discharge mode is relatively slow, the required discharge time is very long, and the requirement of functional safety of an automobile system cannot be met.
Thirdly, an additional discharging loop is added to rapidly discharge the direct current bus capacitor: the scheme adds an extra discharge loop, so that the power of the discharge resistor can be selected to be large, and the discharge speed is high. But because a high-power resistor and a contactor are added, the system cost is increased; and because the power resistor and the contactor with large volume are added, the volume of the product is increased.
Therefore, the three direct current bus capacitor discharging methods can complete direct current bus capacitor discharging, but cannot take the problems of application occasions, discharging speed and price cost into consideration.
Based on the above, the invention provides a direct current bus capacitor discharging method, when a direct current bus capacitor has a discharging requirement, one switching tube on any one bridge arm of a bridge inverter is conducted, and a first pulse width modulation signal is input to the other switching tube on the bridge arm, so that one switching tube is switched between a conducting state and a turning-off state, and because the switching tube is in a linear region in a switching process, a large switching loss can be generated, and energy on the direct current bus capacitor is dissipated on the switching tube in a thermal mode, so that the bridge arm can rapidly complete discharging of the direct current bus capacitor under the condition of not increasing extra cost.
The dc bus capacitor discharging method proposed by the present invention is further described in detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
Referring to fig. 1-2, the dc bus capacitor C1 is connected in parallel with an input end of a bridge inverter, the bridge inverter has at least one bridge arm, each bridge arm has two switching tubes (IGBTs), the present embodiment is described by taking the bridge inverter as a three-phase full-bridge inverter, the three-phase full-bridge inverter has three parallel bridge arms, each bridge arm has two switching tubes, and an output end (U, V, W) led between each switching tube can be used to connect an input end of a three-phase motor. For convenience of description, the switching tubes of each of the bridge arms are numbered, two switching tubes of the first bridge arm are respectively Q1 and Q2, two switching tubes of the second bridge arm are respectively Q3 and Q4, and two switching tubes of the third bridge arm are respectively Q5 and Q6. It is to be understood that the bridge inverter in the present invention is not limited to a full bridge inverter, and may also be a half bridge inverter, and the bridge inverter is also not limited to a three-phase inverter, and may also be a two-phase inverter, a four-phase inverter, etc., as long as there is at least one bridge arm and there are two switching tubes on each bridge arm.
Further, as shown in fig. 2, the dc bus capacitor discharging method includes:
step S1: judging whether the direct current bus capacitor has a discharging requirement or not;
step S2: when the direct current bus capacitor has a discharging requirement, one switching tube on any one bridge arm of the bridge inverter is conducted, and a first pulse width modulation signal is input to the other switching tube on the bridge arm so as to discharge the direct current bus capacitor.
Specifically, for convenience of description, the present embodiment divides the discharging of the dc bus capacitor into three stages, namely, a discharging preparation stage, a pre-discharging stage, and a formal discharging stage. Referring to fig. 1 and 3, first, it is determined whether the dc bus capacitor has a discharging requirement, that is, whether the voltage on the dc bus capacitor C1 is too high (e.g., greater than a predetermined safety voltage U)1In time), if the voltage on the direct current bus capacitor C1 is too high and needs to be discharged, the whole system is closed to enter the discharge standardThe standby stage performs discharge preparation. After the discharge preparation phase is entered, a first counter starts to count to calculate a discharge time T1, in the whole discharge process of the dc bus capacitor, once the discharge time T1 calculated by the first counter is greater than a third threshold T1, the discharge process of the dc bus capacitor needs to be ended, the third threshold T1 is a specified total discharge time, and when the discharge time T1 is overtime, the discharge state needs to be exited, and a discharge overtime fault is reported.
Further, if one switching tube of any one of the bridge arms of the bridge inverter is turned on and the first pulse width modulation signal is input to the other switching tube of the bridge arm, the switching tube to which the first pulse width modulation signal is input is switched between an on state and an off state to generate a pulse current, and because the switching tube is in a linear region in a switching process, a large switching loss is generated, and energy on the dc bus capacitor C1 is dissipated on the switching tube in a hot manner. The higher the frequency of the first pulse width modulation signal is, the larger the duty ratio is, the larger the energy dissipated on the switch tube in unit time is, and the faster the high-voltage direct-current bus capacitor C1 discharges. But at the same time, the switching tube is a very temperature-sensitive device, and a large amount of heat accumulation in a short time can cause the junction temperature of the switching tube to be too high, and finally the switching tube is damaged. Therefore, in order to ensure the thermal safety of the switching tubes, the junction temperature of the two switching tubes on the discharging bridge arm needs to be within the safe discharging junction temperature Tj _ limit in the whole discharging process (the safe discharging junction temperature Tj _ limit may be different depending on different packaging of the switching tube chips and modules).
Based on this, in this embodiment, after entering the discharge preparation stage, it is required to determine whether the bridge inverter meets a discharge condition, that is, determine whether a junction temperature Tj of at least one switching tube of a bridge arm on the bridge inverter is less than or equal to the safe discharge junction temperature Tj _ limit, and when the junction temperature Tj of at least one switching tube of any bridge arm of the bridge inverter is less than or equal to the safe discharge junction temperature Tj _ limit, it may be determined that the bridge inverter meets the discharge condition, and the bridge arm that completes discharging the dc bus capacitor is the bridge arm in which the junction temperature Tj of at least one switching tube is less than or equal to the safe discharge junction temperature Tj _ limit. It can be understood that, since one switching tube of the bridge arm discharging the dc bus capacitor is turned on (basically, no heat is generated), and the other switching tube inputs the first pwm signal (the heat is mainly dissipated in this switching tube), the bridge arm can discharge as long as the junction temperature Tj of the switching tube inputting the first pwm signal is less than or equal to the safe discharge junction temperature Tj _ limit. If the junction temperature Tj of only one switching tube on one bridge arm is less than or equal to the safe discharge junction temperature Tj _ limit, the first pulse width modulation signal needs to be input to the switching tube to enable the other switching tube to be conducted; and if the junction temperature Tj of two switching tubes on one bridge arm is less than or equal to the safe discharge junction temperature Tj _ limit, inputting the first pulse width modulation signal to any one switching tube to enable the rest one switching tube to be conducted.
Further, because there are many switching tubes on the bridge inverter, it is difficult to measure the junction temperature Tj of each switching tube in real time, but when the bridge inverter stops operating, the junction temperature Tj of the switching tube on each bridge arm of the bridge inverter can be estimated, and because the operating states of two switching tubes on one bridge arm of the bridge inverter are substantially the same, it can be considered that the temperatures of two switching tubes on the same bridge arm are the same (or approximately the same). Therefore, in this embodiment, whether the bridge inverter satisfies the discharge condition may be determined by: firstly, calculating junction temperature Tj of a switching tube on each bridge arm of the bridge inverter as comparison junction temperature, and comparing the comparison junction temperature of each bridge arm with the safe discharge junction temperature Tj _ limit; when the comparative junction temperature of any one bridge arm of the bridge inverter is less than or equal to the safe discharge junction temperature Tj _ limit, it is indicated that at least one bridge arm can be discharged, the bridge inverter is determined to meet the discharge condition, the bridge arm meeting the condition can be used for discharging, when the comparative junction temperatures of all bridge arms of the bridge inverter are greater than the safe discharge junction temperature Tj _ limit, it is indicated that the temperatures of the switching tubes of all bridge arms are too high, the discharging cannot be performed, after waiting for a first set time T2, it is determined that the comparative junction temperatures of all bridge arms are less than or equal to the safe discharge junction temperature Tj _ limit, after waiting for the first set time T2, the temperatures of the switching tubes of all bridge arms are reduced to a safe range, and the bridge inverter meets the discharge condition, and can be used for discharging by any bridge arm.
It is understood that the first set time T2 is the calibrated cool-down time, and the switching tube can be lowered to be less than or equal to the safe discharge junction temperature Tj _ limit at a higher temperature through the first set time T2.
Further, as shown in fig. 1, one end of the dc bus capacitor C1 is connected to a positive electrode of a power module E (e.g. a high voltage battery) through a contactor K1, and the other end is connected to a negative electrode of the power module E. In the actual discharging process, due to the reasons of response time delay or damage of the contactor K1 and the like, the contactor K1 may be stuck, once the contactor K1 is stuck, the power module E is directly hung on the high-voltage direct-current bus, and discharging corresponds to discharging energy on the power module E. Compared with the energy on the direct current bus capacitor C1, the energy on the power supply module E is much larger, and the voltage on the direct current bus capacitor C1 hardly drops in the process of discharging by using a switch tube. In this case, the switching tube may continue to discharge, and eventually, the switching tube may be damaged due to overheating.
To avoid this, in this embodiment, after the bridge inverter satisfies the discharging condition, the dc bus capacitor C1 is pre-discharged in the pre-discharging stage to determine whether the dc bus capacitor C1 satisfies the discharging condition, that is, whether the contactor K1 is stuck. Specifically, after the pre-discharge stage is entered, the dc bus capacitor C1 starts to be pre-discharged, and a second counter starts to count the time to calculate the voltage of the dc busThe capacitor C1 is pre-discharged for time t 2. After the direct current bus capacitor C1 is pre-discharged for a second set time T3, acquiring a voltage drop value of the direct current bus capacitor C1; when the voltage drop value of the direct current bus capacitor is greater than or equal to a first threshold value U2If the contactor K1 is not adhered, the direct-current bus capacitor C1 is judged to meet the discharge condition, and the formal discharge stage can be directly started; when the voltage drop value of the direct current bus capacitor C1 is smaller than the first threshold value U2When the voltage drop value of the direct current bus capacitor C1 is larger than or equal to the first threshold value U, the contactor K1 is indicated to be adhered, the second counter is cleared, the direct current bus capacitor C1 is pre-discharged for the second set time T3 again (T2 is equal to T3), then the voltage drop value of the direct current bus capacitor C1 is obtained to be judged, and the steps are repeated until the voltage drop value of the direct current bus capacitor C1 is larger than or equal to the first threshold value U2And if so, indicating that the contactor K1 is not adhered, and judging that the direct current bus capacitor meets the discharge condition.
Optionally, when the number of times of pre-discharging of the dc bus capacitor C1 is greater than a second threshold N, where the second threshold N may be a specified bus capacitor voltage diagnosis number, which indicates that the contactor K1 may be damaged, and the contactor K1 may stick even after waiting for a long time, the discharging process of the dc bus capacitor is ended.
Further, in this embodiment, the step of pre-discharging the dc bus capacitor may be similar to the step of performing formal discharging, that is, one switching tube of any one bridge arm of the bridge inverter is turned on, and a second pulse width modulation signal is input to another switching tube of the bridge arm, so that the bridge arm completes pre-discharging the dc bus capacitor C1. It is understood that the pre-discharging arm of the dc bus capacitor C1 is also a discharging arm (an arm in which the junction temperature Tj of any switching tube is less than or equal to the safe discharging junction temperature Tj _ limit). Moreover, when the pre-discharge method is adopted, if the voltage of the direct current bus capacitor C1 is less than or equal to the safe voltage U in the pre-discharge process1Then the discharging of the dc bus capacitor C1 is completed during the pre-discharging processAt this time, the discharge process may be exited without performing the subsequent formal discharge phase.
Optionally, when the contactor K1 is adhered, the energy of the dc bus capacitor C1 pre-discharging each time is very high, in this embodiment, when the voltage drop value of the dc bus capacitor is smaller than the first threshold, pre-discharging needs to be performed again, and after the dc bus capacitor C1 pre-discharges each time, the dc bus capacitor C1 may be pre-discharged for the second set time T3 after waiting for a third set time T3, so that the switching tube on the discharge bridge arm is cooled. Or, in the discharge preparation stage, if it is determined that all the bridge arms of the bridge inverter can be discharged (the junction temperature Tj of one switching tube on all the bridge arms is less than or equal to the safe discharge junction temperature Tj _ limit), at this time, one bridge arm may be replaced to pre-discharge the dc bus capacitor C1, so as to prevent the temperature of the switching tube on the bridge arm from being too high due to the fact that the same bridge arm is used for discharging all the time.
After the bridge inverter and the dc bus capacitor C1 both satisfy a discharging condition (the bridge arm capable of discharging and the contactor K1 are not adhered), entering a formal discharging stage, turning on one switching tube on any bridge arm (the bridge arm capable of discharging) of the bridge inverter, and inputting a first pulse width modulation signal to another switching tube on the bridge arm to enable the bridge arm to complete discharging of the dc bus capacitor C1, wherein in the formal discharging process, energy on the dc bus capacitor C1 is gradually dissipated on the switching tube, voltage on the dc bus capacitor C1 is gradually reduced, and when the voltage on the dc bus capacitor C1 is less than or equal to the safety voltage U11The discharge process may then be exited.
In this embodiment, the first pwm signal and the second pwm signal are the same pwm signal (the frequency, the duty ratio, etc. are the same), but the first pwm signal may also be different pwm signals, which is not limited in the present invention.
It should be understood that during the formal discharging process of the dc bus capacitor C1, one of the switching tubes in the discharging bridge arm is turned on, and the other switching tube in the other bridge arm is turned off (the other bridge arm is turned off) by applying the first pwm signal. Further, if in the discharge preparation stage, all the bridge arms of the bridge inverter can be used for discharging, and when the voltage on the dc bus capacitor C1 is high, different bridge arms can be used alternately to discharge the dc bus capacitor C1, so as to ensure the safety of the switching tube.
In summary, in the DC bus capacitor discharging method provided by the present invention, when the DC bus capacitor has a discharging requirement, one switching tube on any one bridge arm of the bridge inverter is turned on, and a first pulse width modulation signal is input to another switching tube on the bridge arm, so that the switching tube is switched between the on state and the off state, because the switching tube is in a linear region during the switching process, a large switching loss is generated, and the energy on the DC bus capacitor is dissipated in the form of heat on the switching tube, so that the bridge arm can rapidly complete the discharging of the DC bus capacitor without increasing additional cost.
The above embodiments have described the details of different configurations of the dc bus capacitor discharging method, and it is understood that the present invention includes, but is not limited to, the configurations listed in the above embodiments, and any modifications based on the configurations provided by the above embodiments are within the scope of the present invention. One skilled in the art can take the contents of the above embodiments to take a counter-measure.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.
Claims (10)
1. A method for discharging a direct current bus capacitor, wherein the direct current bus capacitor is connected in parallel with an input end of a bridge inverter, the bridge inverter is provided with at least one bridge arm, and each bridge arm is provided with two switching tubes, and the method for discharging the direct current bus capacitor comprises the following steps:
when the direct-current bus capacitor has a discharging requirement, enabling one switching tube on any one bridge arm of the bridge inverter to be conducted, and inputting a first pulse width modulation signal to the other switching tube on the bridge arm to discharge the direct-current bus capacitor;
before discharging, judging whether the direct current bus capacitor meets a discharging condition, including:
after the direct current bus capacitor is pre-discharged for a second set time, acquiring a voltage drop value of the direct current bus capacitor;
when the voltage drop value of the direct current bus capacitor is larger than or equal to a first threshold value, judging that the direct current bus capacitor meets a discharging condition; when the voltage drop value of the direct current bus capacitor is smaller than the first threshold value, the direct current bus capacitor is pre-discharged for the second set time again until the voltage drop value of the direct current bus capacitor is larger than or equal to the first threshold value, and the direct current bus capacitor is judged to meet the discharge condition.
2. The dc bus capacitive discharge method of claim 1, further comprising:
sequentially judging whether the bridge inverter and the direct current bus capacitor meet a discharging condition;
and when the bridge inverter and the direct-current bus capacitor both meet the discharge condition, enabling one switching tube on any one bridge arm of the bridge inverter to be conducted, and inputting the first pulse width modulation signal to the other switching tube on the bridge arm.
3. The method according to claim 2, wherein when the junction temperature of at least one switching tube on any one of the bridge arms of the bridge inverter is less than or equal to a safe discharge junction temperature, it is determined that the bridge inverter satisfies the discharge condition, and the bridge arm for discharging the dc bus capacitor is the bridge arm in which the junction temperature of at least one switching tube is less than or equal to the safe discharge junction temperature.
4. The method of discharging a dc bus capacitor of claim 3, wherein the step of determining whether the bridge inverter satisfies the discharge condition comprises:
obtaining junction temperature of a switching tube on each bridge arm of the bridge inverter as comparison junction temperature, and comparing the comparison junction temperature of each bridge arm with the safe discharge junction temperature;
when the comparative junction temperature of any bridge arm is less than or equal to the safe discharge junction temperature, judging that the bridge inverter meets the discharge condition; and when the comparative junction temperatures of all the bridge arms are greater than the safe discharge junction temperature, after waiting for a first set time, judging that the comparative junction temperatures of all the bridge arms are less than or equal to the safe discharge junction temperature, and enabling the bridge inverter to meet the discharge condition.
5. The method according to claim 2, wherein the dc bus capacitor is connected to a power module via a contactor, and the dc bus capacitor satisfies the discharging condition when the contactor is not adhered.
6. The method according to claim 1, wherein the discharging process of the dc bus capacitor is terminated when the number of times of pre-discharging of the dc bus capacitor is greater than a second threshold.
7. The method of discharging a dc bus capacitor of claim 1, wherein the step of pre-discharging the dc bus capacitor comprises:
and enabling one switching tube on any one bridge arm of the bridge inverter to be conducted, and inputting a second pulse width modulation signal to the other switching tube on the bridge arm so as to pre-discharge the direct current bus capacitor.
8. The method of discharging a dc bus capacitor of claim 7 wherein the first pwm signal and the second pwm signal are the same pwm signal.
9. The method according to claim 1, wherein when the voltage drop value of the dc bus capacitor is smaller than the first threshold, the dc bus capacitor is pre-discharged after waiting a third set time.
10. The method according to claim 2, wherein the calculation of the discharge time is started when the bridge inverter is determined to satisfy the discharge condition, and the discharge process of the dc bus capacitor is ended when the discharge time is greater than a third threshold value.
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| CN112737301A (en) | 2021-04-30 |
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