CN116232100A - Pulse width modulation method and system for reducing heating imbalance of switching device - Google Patents
Pulse width modulation method and system for reducing heating imbalance of switching device Download PDFInfo
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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
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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
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
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- H—ELECTRICITY
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
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- H—ELECTRICITY
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- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
- H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
- H02P27/085—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency
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Abstract
The embodiment of the invention provides a pulse width modulation method and a system for reducing unbalanced heating of a switching device, belonging to the technical field of switching devices of inverters. The pulse width modulation method comprises the steps of obtaining a sector where a switching device is located and a corresponding zero vector; timing the duration of the zero vector; and selecting a switching zero vector according to the duration of the zero vector to switch the conduction of the switching device. According to the pulse width modulation method for reducing the heating imbalance of the switching device, the duration of the zero vector is timed by acquiring the working sector of the switching device and the corresponding zero vector, and if the duration of the zero vector is overlong, the zero vector is switched, so that the switching device is switched to be in a conducting state, the heating imbalance problem of the switching device is effectively reduced, and the reliability of the inverter is improved.
Description
Technical Field
The invention relates to the technical field of switching devices of inverters, in particular to a pulse width modulation method and a pulse width modulation system for reducing unbalanced heating of the switching devices.
Background
In the field of ac transmission, an inverter is generally used as a core device for driving a motor to operate, and a Pulse Width Modulation (PWM) mode is generally adopted. Compared with Continuous Pulse Width Modulation (CPWM), discontinuous Pulse Width Modulation (DPWM) realizes that a switching device does not act in a certain interval in one voltage fundamental wave period, so that switching loss can be reduced, conversion efficiency is improved, and therefore DPWM is very popular in inverter application. The DPWM strategies currently in common use are: DPWM0, DPWM1, DPWM2, DPWM3, DPWMMAX, DPWMMIN and the like are all characterized in that different sectors are defined by taking a fundamental voltage vector as a reference, different zero vectors are configured in the different sectors, so that a one-phase switching device is always inactive in each interval of 30 degrees, 60 degrees or 120 degrees, and the distribution of the zero vectors is related to the fundamental voltage phase.
When the motor operates at a low speed, the output voltage frequency of the inverter is low, the fundamental wave period is long, when the DPWM of the common technology is adopted, the situation that one bridge arm switching device continuously turns on for a long time to circulate current and the other bridge arm switching device continuously turns off to not circulate current exists in the phase of the switching device, zero vector switching is slow at low frequency, heating of an upper bridge arm and a lower bridge arm is uneven, and particularly when the motor is locked, because no voltage phase change exists, only the switching device of one bridge arm bears all current and the switching device of the other bridge arm always does not circulate current, and serious unbalanced heating problem of the switching device can occur, so that the reliability of the inverter is seriously affected.
The inventor of the present application found that in the process of implementing the present invention, the above scheme of the prior art has the defect that the heat generation imbalance of the switching device of the inverter causes poor reliability of the inverter.
Disclosure of Invention
The embodiment of the invention aims to provide a pulse width modulation method and a system for reducing the heat imbalance of a switching device, which can avoid the problem of the heat imbalance of switching devices of upper and lower bridge arms.
In order to achieve the above object, an embodiment of the present invention provides a pulse width modulation method for reducing heat imbalance of a switching device, including:
acquiring a sector where a switching device is located and a corresponding zero vector;
timing the duration of the zero vector;
and selecting a switching zero vector according to the duration of the zero vector to switch the conduction of the switching device.
Optionally, selecting a switching zero vector to switch on the switching device according to a duration size of the zero vector includes:
judging whether the duration time of the zero vector is larger than a preset threshold value or not;
switching the zero vector and re-timing the duration of the zero vector under the condition that the duration of the zero vector is judged to be greater than a preset threshold value;
and maintaining the conduction of the switching device under the condition that the duration time of the zero vector is less than or equal to a preset threshold value.
Optionally, the zero vector includes full conduction of a lower bridge arm switching device of the three-phase bridge arm and full conduction of an upper bridge arm switching device of the three-phase bridge arm.
Optionally, acquiring the sector in which the switching device is located and the corresponding zero vector includes:
acquiring the position of a current voltage vector;
judging whether sector switching occurs or not;
under the condition that sector switching is judged to occur, configuring a voltage vector and the zero vector, and timing the duration time of the zero vector;
in the case that the sector switching is judged not to occur, the duration of the zero vector is timed.
Optionally, the voltage vector includes that the upper bridge arm switching device of the three-phase bridge arm U-phase is turned on, the lower bridge arm switching devices of the three-phase bridge arm V-phase and the W-phase are turned on, the upper bridge arm switching devices of the three-phase bridge arm U-phase and the V-phase are turned on, and the lower bridge arm switching devices of the three-phase bridge arm W-phase are turned on.
Optionally, the voltage vector further includes a three-phase bridge arm V-phase upper bridge arm switching device, a three-phase bridge arm U-phase lower bridge arm switching device, a three-phase bridge arm V-phase upper bridge arm switching device, and a three-phase bridge arm U-phase lower bridge arm switching device.
Optionally, the voltage vector further includes upper bridge arm conduction of the three-phase bridge arm W phase, lower bridge arm conduction of the three-phase bridge arm U phase and the V phase, upper bridge arm conduction of the three-phase bridge arm U phase and the W phase, and lower bridge arm conduction of the three-phase bridge arm V phase.
Optionally, the preset threshold comprises 30ms.
In another aspect, the present invention also provides a pulse width modulation system for reducing heat imbalance of a switching device, including:
a three-phase inverter circuit;
the timer is connected with the three-phase inverter circuit and is used for timing the duration time of the zero vector in the three-phase inverter circuit;
and the controller is connected with the three-phase inverter circuit and the timer and is used for executing the pulse width modulation method.
In yet another aspect, the present invention also provides a computer-readable storage medium storing instructions for being read by a machine to cause the machine to perform a pulse width modulation method as described in any one of the above.
According to the technical scheme, the pulse width modulation method for reducing the heating imbalance of the switching device provided by the invention has the advantages that the working sector of the switching device and the corresponding zero vector are obtained, the duration of the zero vector is timed, and if the duration of the zero vector is overlong, the zero vector is switched, so that the switching device is switched to be in a conducting state, the heating imbalance of the switching device is further effectively reduced, and the reliability of the inverter is improved.
Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain, without limitation, the embodiments of the invention. In the drawings:
FIG. 1 is a flow chart of a pulse width modulation method of reducing switching device heating imbalance in accordance with one embodiment of the present invention;
FIG. 2 is a flow chart of zero vector determination in a pulse width modulation method for reducing switching device heating imbalance in accordance with one embodiment of the present invention;
FIG. 3 is a flow chart of sector switching decisions in a pulse width modulation method for reducing switching device heating imbalance in accordance with one embodiment of the present invention;
FIG. 4 is a flow chart of an inverter output frequency determination in a pulse width modulation method for reducing switching device heating imbalance in accordance with one embodiment of the present invention;
FIG. 5 is a flow chart of an inverter output current determination in a pulse width modulation method for reducing switching device heat imbalance in accordance with one embodiment of the present invention;
FIG. 6 is a flow chart of obtaining a preset threshold in a pulse width modulation method for reducing switching device heating imbalance according to one embodiment of the present invention;
FIG. 7 is a schematic diagram of sector division in a pulse width modulation method for reducing switching device heating imbalance in accordance with one embodiment of the present invention;
fig. 8 is a schematic diagram of bridge arm switching device conduction states before and after zero vector switching in a pulse width modulation method for reducing switching device heat imbalance according to one embodiment of the present invention.
Detailed Description
The following describes the detailed implementation of the embodiments of the present invention with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
Fig. 1 is a flowchart of a pulse width modulation method for reducing switching device heat generation imbalance in accordance with one embodiment of the present invention. In fig. 1, the pulse width modulation method may include:
in step S10, the sector in which the switching device is located and the corresponding zero vector are acquired. As shown in fig. 7, the state where the upper arm switch is turned on and the lower arm switch is turned off is represented as 1, and the state where the upper arm switch is turned off and the lower arm switch is turned on is represented as 0, so that the switch logic combination of the three-phase arm U, V, W can be described by 8 basic voltage vectors. Specifically, the 8 basic voltage vectors may include U0 (000), U1 (100), U2 (110), U3 (010), U4 (011), U5 (001), U6 (101), U7 (111). Specifically, U0 (the lower arm of the three-phase arm is fully conductive) and U7 (the upper arm of the three-phase arm is fully conductive) are zero vectors, U1 to U6 are non-zero vectors, and 6 non-zero basic vectors are divided into 6 sectors.
In step S11, the duration of the zero vector is timed. Wherein the duration of the zero vector in each sector needs to be timed to determine if the on-time of the switching device is too long for that zero vector in that sector.
In step S12, the switching zero vector is selected according to the magnitude of the duration of the zero vector to switch the switching device on. Wherein, in each sector, two different bridge arm switches can be allocated to be inactive according to the difference of zero vectors, and specifically, the bridge arm switches can be shown in table 1.
Table 1 table of the operational relationship of sector, zero vector and three-phase switch
In step S10 to step S12, the sector where the three-phase bridge arm switching device of the inverter is located and the corresponding zero vector are acquired first, the duration of the zero vector is timed, and after the duration of the zero vector reaches a certain threshold, the zero vector is switched. Specifically, if the zero vector is counted as U0, the operation is switched to U7, and if the zero vector is counted as U7, the operation is switched to U0. After the zero vector is switched, the conducting state of the switching devices of the three-phase bridge arm can be changed, and further heating non-uniformity caused by continuous conduction of the switching devices on the three-phase bridge arm is avoided.
The traditional inverter adopts Discontinuous Pulse Width Modulation (DPWM) to realize that a switching device does not act in a certain interval in a voltage fundamental wave period, but when a motor runs at a low speed, the output voltage frequency of the inverter is low, the fundamental wave period is long, one bridge arm switching device of a phase in which the switching device does not act is continuously conducted for a long time by adopting the DPWM mode, the other bridge arm switching device is continuously turned off for a long time, and therefore the switching devices of an upper bridge arm and a lower bridge arm generate heat unevenly. In addition, if CPWM mode is adopted, zero vectors U0 and U7 are evenly distributed, the upper bridge arm and the lower bridge arm can be guaranteed to bear the same current load, and heat generation can be balanced. However, CPWM increases the switching times of the switching device, increases the loss in low frequency, and increases the switching loss control in low frequency than in high frequency because the speed of the alternating conversion between the three-phase currents in low frequency operation of the inverter is slower than that in high frequency operation, so that the switching loss control in low frequency is higher than that in high frequency operation, CPWM is adopted to ensure the balance of the upper bridge arm and the lower bridge arm, but the total switching loss is increased, which is unfavorable for safe and reliable low frequency operation. In the embodiment of the invention, the duration time of the zero vector in the same sector is monitored, the zero vector is switched according to the duration time to switch the on state of the switching device, so that the problem of unbalanced heating of the switching device can be effectively reduced, and the reliability of the inverter is improved.
In this embodiment of the present invention, in order to implement adjustment of the heat balance of the switching devices of the upper and lower bridge arms, it is also necessary to determine the duration of the zero vector in the sector, and specifically, the determining step may be as shown in fig. 2. Specifically, in fig. 2, the pulse width modulation method may further include:
in step S20, it is determined whether the duration of the zero vector is greater than a preset threshold.
In step S21, when it is determined that the duration of the zero vector is greater than the preset threshold, the zero vector is switched, and the duration of the zero vector is counted again. If the duration of the current zero vector is longer than the preset threshold, it indicates that one of the bridge arm switching devices of the non-action phase is too long, and the other bridge arm switching device is too long, so that the situation of uneven heating exists, the zero vector is switched, the non-action phase is switched, the conduction situation of the upper bridge arm and the lower bridge arm is further changed, and the situation of uneven heating of the upper bridge arm switching device and the lower bridge arm switching device is avoided. Specifically, as shown in fig. 8, taking the sector 1 as an example, in the switching period Ts1, a zero vector is configured to be U7, and at this time, the U-phase upper arm is continuously turned on, the lower arm is continuously turned off, and the current continuously flows from the upper arm. Meanwhile, because the output voltage is low at low frequency, the zero vector U7 time has a large duty ratio in a switching period, and the V-phase and W-phase bridge arms have switching actions, but the current flows in the upper bridge arm in most of the time, and the heating value of the three-phase upper bridge arm switching device is far higher than that of the lower bridge arm switching device. When the PWM duration with sector 1 zero vector U7 reaches the preset time threshold, it is switched to zero vector U0, as shown by switching period Ts2 in fig. 8. At this time, the inactive phase of the switch is switched to the W phase, the lower bridge arm of the W phase is continuously turned on, the upper bridge arm is continuously turned off, and current continuously flows from the lower bridge arm. Meanwhile, because the output voltage is low at low frequency, the zero vector U0 time has a large duty ratio in the switching period, and the current flows through the lower bridge arm in most of the V phase and the W phase, so that the heating state of the three-phase upper bridge arm switching device is changed to the heating state of the lower bridge arm switching device. When the voltage vector is still in sector 1 and the zero vector U0 duration reaches the preset time threshold, the switching to zero vector U7 is again carried by the three-phase upper leg switching device.
In step S22, in the case where it is determined that the duration of the zero vector is less than or equal to the preset threshold value, the on state of the switching device is maintained. If the duration of the zero vector is less than or equal to the preset threshold, the conduction time of one bridge arm of the non-action phase is in a controllable range, and the conduction state can be continuously maintained.
In step S20 to step S22, the duration of the zero vector is first determined, and if the duration is greater than the predetermined threshold, it is indicated that the one-phase heating is not performed for a long time. Therefore, zero vectors are switched to switch the phase of no action, and further the influence of unbalanced heating of the upper bridge arm and the lower bridge arm for a long time on the reliability of the inverter is avoided. If the duration is less than or equal to the preset threshold, the state that the one-phase heating is not operated is in the controllable range, and the conduction state can be maintained. The pulse width modulation method maintains the advantages of few DPWM switching times and low switching loss, and simultaneously evenly distributes the circulating current of the upper bridge and the lower bridge, thereby avoiding the problem of unbalanced heating of the switching devices of the upper bridge arm and the lower bridge arm.
In this embodiment of the invention, the size for the preset threshold comprises 30ms. Specifically, under the condition that the preset threshold value is 30ms, compared with the current general DPWM strategy, only 33 switching actions are added per second, the switching loss change is negligible, and the problem of unbalanced heating of the upper bridge arm and the lower bridge arm can be effectively reduced, so that the reliability of the inverter is improved.
In this embodiment of the present invention, in order to further improve the accuracy of adjusting the heat balance of the upper and lower bridge arms, it is also necessary to determine whether or not sector switching occurs in the voltage vector, and the specific steps may be as shown in fig. 3. Specifically, in fig. 3, the pulse width modulation method may include:
in step S30, the position of the current voltage vector is acquired. The position of the voltage vector may include the six sectors described above.
In step S31, it is determined whether or not sector switching occurs. The voltage vectors of different sectors are different, namely the on states of the three-phase bridge arm switching devices are different.
In step S32, when it is determined that the sector switching has occurred, the voltage vector and the zero vector are arranged, and the duration of the zero vector is counted. If there is sector switching, the conducting state of the three-phase bridge arm switching device needs to be changed, corresponding voltage vectors (non-zero voltage vectors) and zero vectors are configured according to the sectors, and the duration of the current zero vector is reckoned. Specifically, the voltage vector may include U1 (upper arm switching device on of the three-phase arm U-phase, lower arm switching device on of the three-phase arm V-phase and W-phase), U2 (upper arm switching device on of the three-phase arm U-phase and V-phase, lower arm switching device on of the three-phase arm W-phase), U3 (upper arm switching device on of the three-phase arm V-phase, lower arm switching device on of the three-phase arm U-phase and W-phase), U4 (upper arm switching device on of the three-phase arm V-phase and W-phase, lower arm switching device on of the three-phase arm U-phase), U5 (upper arm switching device on of the three-phase arm W-phase, lower arm switching device on of the three-phase arm U-phase and V-phase), U6 (upper arm switching device on of the three-phase arm and W-phase, lower arm switching device on of the three-phase arm V-phase) mentioned above. Specifically, the configuration of the zero vector may include U0 or U7.
In step S33, in the case where it is determined that the sector switching does not occur, the duration of the current zero vector is counted. If sector switching does not occur, the continuous operation in the same sector is indicated, the duration of the current zero vector is timed, whether the duration reaches a preset threshold value or not is tracked in real time, and if the duration does not reach the preset threshold value, wave-transmitting control is performed.
In step S30 to step S33, the position of the voltage vector is first obtained to determine whether sector switching occurs, if sector switching occurs, the voltage vector and the zero vector are reconfigured, and the duration of the zero vector is counted; if sector switching does not occur, tracking and monitoring whether the duration of the zero vector reaches a preset threshold value so as to facilitate timely switching of the zero vector, and adjusting the on-off state of the three-phase bridge arm switching device to avoid unbalanced heating of the switching device.
In this embodiment of the present invention, in order to further improve the accuracy of adjusting the heat balance of the three-phase legs of the inverter, the pulse width modulation method may further include the steps as shown in fig. 4. Specifically, in fig. 4, the pulse width modulation method may include:
in step S40, the output frequency of the inverter is acquired.
In step S41, it is determined whether the output frequency is greater than or equal to a preset value.
In step S42, in the case where it is determined that the output frequency is greater than or equal to the preset value, the conventional DPWM mode is adopted.
In step S43, in the case where the output frequency is determined to be smaller than the preset value, the sector in which the switching device is located and the corresponding zero vector are acquired.
In step S40 to step S43, the output frequency of the inverter is first determined, and if the output frequency of the inverter is greater than or equal to the preset value, it is indicated that the output frequency of the inverter is high, and the on time of one of the bridge arm switching devices of the inactive one phase is not too long at the high frequency, and the conventional DPWM mode is adopted. If the output frequency of the inverter is smaller than the preset value, the output frequency of the inverter is low, and the on time of one bridge arm switching device of one phase which does not act is too long at the low frequency, so that the duration time of the zero vector needs to be monitored.
In this embodiment of the present invention, in order to further improve the accuracy of adjusting the heat balance of the three-phase leg of the inverter, the pulse width modulation method may further include the steps as shown in fig. 5. Specifically, in fig. 5, the pulse width modulation method may include:
in step S50, an output current of the inverter is acquired.
In step S51, it is determined whether the output current is less than or equal to a preset current value.
In step S52, in the case where it is determined that the output current is less than or equal to the preset current value, the CPWM mode is adopted.
In step S53, in the case where it is determined that the output current is greater than the preset current value, the sector in which the switching device is located and the corresponding zero vector are acquired.
In steps S50 to S53, the output current of the inverter is obtained and judged first, and if the output current of the inverter is smaller than or equal to a preset current value, CPWM mode should be adopted in order to reduce output harmonics; if the output current of the inverter is larger than a preset current value, the duration time of the zero vector is required to be tracked and controlled so as to ensure the heating balance of the three-phase bridge arm of the inverter.
In this embodiment of the present invention, for the magnitude of the preset threshold, it may be decided according to the switching device characteristics, and specifically the steps may include the steps as shown in fig. 6. Specifically, in fig. 6, the pulse width modulation method may further include:
in step S60, the current values of a plurality of gradients are preset. The magnitude of the current value may be determined according to the current value flowing through the switching device of the three-phase bridge arm in the inverter in an actual state.
In step S61, a plurality of gradient current values are flown through the switching device, temperature values of time periods of the switching device and the like are acquired, and a temperature coordinate set is formed. The sampling time interval is preset, a plurality of temperature values are collected near the optimal working temperature of the switching device, and a temperature coordinate set is formed.
In step S62, a fitted linear function around the optimum operating temperature of the switching device is obtained according to formula (1),
wherein sigma is the error, x i Y is the moment corresponding to the ith temperature value in the temperature coordinate set i For the i-th temperature value in the temperature coordinate set, k is the slope of the fit straight line function, b is the intercept of the fit straight line function, i is the integer number, and i e n, n is the number of temperature values in the temperature coordinate set. Wherein the slope and intercept of the fitted straight-line function are calculated according to equation (1).
In step S63, the moment when the switching device is at the optimum operating temperature is calculated according to formula (2),
wherein x is * For the moment of time when the switching device is at the optimum operating temperature, y * Is the optimum operating temperature of the switching device.
In step S64, the time when the switching device is at the operating temperature is taken as a preset threshold.
In step S60 to step S64, the time when the switching device reaches the optimal working temperature under different current values is calculated, and the value within a certain range of the time which can be up and down floated according to the actual requirement can be used as the actual preset threshold value, so that the switching device can be ensured to continuously work near the optimal working temperature, and the service life and reliability of the switching device are further improved.
On the other hand, the invention also provides a pulse width modulation system for reducing the heating imbalance of the switching device. In particular, the pulse width modulation system may include a three-phase inverter circuit, a timer, and a controller.
The timer is connected with the three-phase inverter circuit and is used for timing the duration of the zero vector in the three-phase inverter circuit. The controller is connected with the three-phase inverter circuit and the timer and is used for executing any pulse width modulation method.
In yet another aspect, the present invention also provides a computer-readable storage medium. In particular, the computer readable storage medium stores instructions for reading by a machine to cause the machine to perform a pulse width modulation method as any one of the above.
According to the technical scheme, the pulse width modulation method for reducing the heating imbalance of the switching device provided by the invention has the advantages that the working sector of the switching device and the corresponding zero vector are obtained, the duration of the zero vector is timed, and if the duration of the zero vector is overlong, the zero vector is switched, so that the switching device is switched to be in a conducting state, the heating imbalance of the switching device is further effectively reduced, and the reliability of the inverter is improved.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
In one typical configuration, a computing device includes one or more processors (CPUs), input/output interfaces, network interfaces, and memory.
The memory may include volatile memory in a computer-readable medium, random Access Memory (RAM) and/or nonvolatile memory, etc., such as Read Only Memory (ROM) or flash RAM. Memory is an example of a computer-readable medium.
Computer readable media, including both non-transitory and non-transitory, removable and non-removable media, may implement information storage by any method or technology. The information may be computer readable instructions, data structures, modules of a program, or other data. Examples of storage media for a computer include, but are not limited to, phase change memory (PRAM), static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), read Only Memory (ROM), electrically Erasable Programmable Read Only Memory (EEPROM), flash memory or other memory technology, compact disc read only memory (CD-ROM), digital Versatile Discs (DVD) or other optical storage, magnetic cassettes, magnetic tape magnetic disk storage or other magnetic storage devices, or any other non-transmission medium, which can be used to store information that can be accessed by a computing device. Computer-readable media, as defined herein, does not include transitory computer-readable media (transmission media), such as modulated data signals and carrier waves.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article or apparatus that comprises an element.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and changes may be made to the present application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. which are within the spirit and principles of the present application are intended to be included within the scope of the claims of the present application.
Claims (10)
1. A pulse width modulation method for reducing heat imbalance of a switching device, comprising:
acquiring a sector where a switching device is located and a corresponding zero vector;
timing the duration of the zero vector;
and selecting a switching zero vector according to the duration of the zero vector to switch the conduction of the switching device.
2. The pulse width modulation method of claim 1, wherein selecting a switching zero vector to switch on the switching device based on a magnitude of a duration of the zero vector comprises:
judging whether the duration time of the zero vector is larger than a preset threshold value or not;
switching the zero vector and re-timing the duration of the zero vector under the condition that the duration of the zero vector is judged to be greater than a preset threshold value;
and maintaining the conduction of the switching device under the condition that the duration time of the zero vector is less than or equal to a preset threshold value.
3. The pulse width modulation method of claim 2, wherein the zero vector comprises a full conduction of a lower leg switching device of a three-phase leg and a full conduction of an upper leg switching device of the three-phase leg.
4. The pulse width modulation method of claim 3, wherein obtaining the sector in which the switching device is located and the corresponding zero vector comprises:
acquiring the position of a current voltage vector;
judging whether sector switching occurs or not;
under the condition that sector switching is judged to occur, configuring a voltage vector and the zero vector, and timing the duration time of the zero vector;
in the case that the sector switching is judged not to occur, the duration of the zero vector is timed.
5. The pulse width modulation method of claim 4, wherein the voltage vector comprises an upper leg switching device of the three-phase leg U-phase being turned on, a lower leg switching device of the three-phase leg V-phase and W-phase being turned on, and an upper leg switching device of the three-phase leg U-phase and V-phase being turned on, and a lower leg switching device of the three-phase leg W-phase being turned on.
6. The pulse width modulation method of claim 5, the voltage vector further comprises an upper leg switching device of a three-phase leg V-phase, a lower leg switching device of a three-phase leg U-phase and W-phase, an upper leg switching device of a three-phase leg V-phase and W-phase, and a lower leg switching device of a three-phase leg U-phase.
7. The pulse width modulation method of claim 6, wherein the voltage vector further comprises an upper leg conduction of the W-phase of the three-phase legs, a lower leg conduction of the U-phase and V-phase of the three-phase legs, an upper leg conduction of the U-phase and W-phase of the three-phase legs, and a lower leg conduction of the V-phase of the three-phase legs.
8. The pulse width modulation method of claim 2, wherein the preset threshold comprises 30ms.
9. A pulse width modulation system for reducing switching device heating imbalance, comprising:
a three-phase inverter circuit;
the timer is connected with the three-phase inverter circuit and is used for timing the duration time of the zero vector in the three-phase inverter circuit;
a controller, connected to the three-phase inverter circuit and the timer, for executing the pulse width modulation method according to any one of claims 1 to 8.
10. A computer readable storage medium storing instructions for reading by a machine to cause the machine to perform the pulse width modulation method of any one of claims 1 to 8.
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