A BOOST converter, a hybrid electric system and a control method
By controlling the switching transistor to block the waveform and turn it on at the appropriate time when the bidirectional interleaved parallel BOOST converter fails, the problem of overheating damage of the switching transistor is solved, and the system's safety protection and stable operation are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEFEI SUNSHINE POWER TECH CO LTD
- Filing Date
- 2022-12-30
- Publication Date
- 2026-05-26
AI Technical Summary
When a bidirectional interleaved parallel BOOST converter fails, the switching transistors overheat and are damaged due to the voltage drop of the body diode and the large current, affecting the normal operation of the system.
In case of a fault, the first, second, third, and fourth switching transistors are all blocked. When the voltage difference between the DC power supply and the bus capacitor is less than or equal to a preset voltage threshold, the second and third switching transistors are turned on to protect the switching transistors.
This avoids damage to the switching transistor due to overheating, reduces inrush current, and ensures safe and stable system operation.
Smart Images
Figure CN115987077B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electric vehicle technology, specifically to a BOOST converter, a hybrid electric system, and a control method. Background Technology
[0002] The hybrid electric system includes a bidirectional interleaved parallel boost converter. The battery side of the bidirectional interleaved parallel boost converter connects to the power battery, while the bus side connects to the generator system and the electric motor system. The topology of the bidirectional interleaved parallel boost converter reduces the current load on components, improves system redundancy, and reduces voltage and current ripple under the same hardware parameters and switching frequencies. The boost function of the bidirectional interleaved parallel boost converter can reduce the number of battery cells connected in series, achieving miniaturization and weight reduction of the on-board power supply.
[0003] When the electric motor system is in electric mode, the generator system and the power supply system work together to power the electric motor system to drive the vehicle or other mechanical rotating equipment. When the electric motor system is in regenerative braking mode, the energy fed back by the electric motor system charges the battery through a bidirectional interleaved parallel BOOST converter. In this case, the generator system can either operate in generator mode and work together with the electric motor system to power the battery, or the generator system can be off and the electric motor system can power the battery alone.
[0004] When a fault occurs during the operation of a bidirectional interleaved parallel BOOST converter, all switches in the converter need to be blocked. However, because each switch has a body diode, after blocking, the power battery will supply energy to the bus capacitor on the bus side through the body diode. Due to the large voltage drop of the body diode, the switch will eventually overheat and be damaged. Summary of the Invention
[0005] In view of this, this application provides a BOOST converter, a hybrid electric system, and a control method that can prevent the switching transistors from overheating and being damaged when the BOOST converter fails.
[0006] This application provides a BOOST converter, including: a first inductor, a second inductor, a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor;
[0007] The first terminal of the first inductor and the first terminal of the second inductor are both used to connect to the positive terminal of the DC power supply. The second terminal of the first inductor is connected to the first terminal of the bus capacitor through the second switching transistor. The second terminal of the second inductor is connected to the first terminal of the bus capacitor through the third switching transistor. The first switching transistor is connected between the second terminal of the first inductor and the negative terminal of the DC power supply. The fourth switching transistor is connected between the second terminal of the second inductor and the negative terminal of the DC power supply.
[0008] When the BOOST converter fails, the first, second, third, and fourth switches are all blocked; when the difference between the DC power supply voltage and the bus capacitor voltage is less than or equal to a preset voltage threshold, the second and third switches are turned on to protect them.
[0009] Preferably, it further includes: a voltage detection circuit and a controller;
[0010] Voltage detection circuit, used to detect the voltage of DC power supply and bus capacitor;
[0011] The controller is used to block the first, second, third, and fourth switching transistors when the BOOST converter fails, and to turn on the second and third switching transistors when the difference between the DC power supply voltage and the bus capacitor voltage is less than or equal to a preset voltage threshold.
[0012] Preferably, the controller is further configured to determine whether the BOOST converter has malfunctioned based on at least one of the voltage, current, or temperature of the BOOST converter.
[0013] Preferably, the controller is further configured to gradually increase the pulse width of the drive signals for the first and fourth switching transistors and gradually decrease the pulse width of the drive signals for the second and third switching transistors after the BOOST converter fault is cleared.
[0014] This application also provides a hybrid electric system, including the BOOST converter described above, and further including: a generator system and an electric motor system;
[0015] Both the generator system and the motor system are connected to the bus capacitor;
[0016] The DC power source is a power battery.
[0017] This application also provides a control method for a BOOST converter. The BOOST converter includes: a first inductor, a second inductor, a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor. The first terminal of the first inductor and the first terminal of the second inductor are both used to connect to the positive terminal of a DC power supply. The second terminal of the first inductor is connected to the first terminal of a bus capacitor through the second switching transistor. The second terminal of the second inductor is connected to the first terminal of the bus capacitor through the third switching transistor. The first switching transistor is connected between the second terminal of the first inductor and the negative terminal of the DC power supply. The fourth switching transistor is connected between the second terminal of the second inductor and the negative terminal of the DC power supply.
[0018] The method includes:
[0019] When the BOOST converter fails, the first, second, third, and fourth switching transistors all block the waveform.
[0020] When the difference between the voltage of the DC power supply and the voltage of the bus capacitor is less than or equal to a preset voltage threshold, the second and third switching transistors are turned on to protect them.
[0021] Preferably, it further includes:
[0022] Detect the voltage of the DC power supply and the voltage of the bus capacitor.
[0023] Preferably, it further includes determining whether the BOOST converter has malfunctioned based on at least one of the voltage, current, or temperature of the BOOST converter.
[0024] Preferably, the DC power source is a power battery.
[0025] Preferably, the bus capacitor is also connected to the generator system and the motor system.
[0026] Therefore, this application has the following beneficial effects:
[0027] The BOOST converter provided in this application, when a BOOST converter failure occurs, first controls the first, second, third, and fourth switching transistors to block the waveform; when the difference between the DC power supply voltage and the bus capacitor voltage is less than or equal to a preset voltage threshold, it controls the second and third switching transistors to conduct, thereby protecting the body diodes of the second and third switching transistors. This scheme controls the second and third switching transistors to conduct only when the difference between the DC power supply voltage and the bus capacitor voltage is small, which can both ensure that the body diodes do not overheat and avoid excessive inrush current. Attached Figure Description
[0028] Figure 1 A schematic diagram of a hybrid electric system provided in this application embodiment;
[0029] Figure 2 This is a schematic diagram of a BOOST converter provided in an embodiment of this application;
[0030] Figure 3 A schematic diagram of a hybrid electric system provided in this application embodiment;
[0031] Figure 4 A flowchart illustrating a control method for a BOOST converter provided in an embodiment of this application. Detailed Implementation
[0032] To enable those skilled in the art to better understand the technical solutions provided in the embodiments of this application, the application scenarios are first described below with reference to the accompanying drawings. This application takes the field of hybrid electric vehicles as an example.
[0033] See Figure 1 The figure is a schematic diagram of a hybrid electric system provided in an embodiment of this application.
[0034] The hybrid electric system includes: a bidirectional interleaved parallel BOOST converter, an electric motor system MS2, and a generator system MS1;
[0035] The bidirectional interleaved parallel BOOST converter includes: a first inductor L1, a second inductor L2, a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4;
[0036] The first terminal of the first inductor L1 and the first terminal of the second inductor L2 are both used to connect to the positive terminal of the power battery. The second terminal of the first inductor L1 is connected to the first terminal of the bus capacitor Cbus through the second switch S2. The second terminal of the second inductor L2 is connected to the first terminal of the bus capacitor Cbus through the third switch S3. The first switch S1 is connected between the second terminal of the first inductor L1 and the negative terminal of the power battery. The fourth switch S4 is connected between the second terminal of the second inductor L2 and the negative terminal of the power battery.
[0037] The battery side of the bidirectional interleaved parallel BOOST converter is connected to the first capacitor C1, and also to the power battery.
[0038] The bus side of the bidirectional interleaved parallel BOOST converter is connected to MS1 and MS2. When MS2 is in electric mode: MS1 and the power system jointly supply power to system MS2 to drive the vehicle or other mechanical rotating equipment; when MS2 is in regenerative braking mode, the energy fed back by the MS2 system charges the battery through the bidirectional interleaved parallel BOOST converter. At this time, MS1 can either work in generator mode and jointly supply power to the battery with MS2, or it can not work and supply power to the battery alone through MS2.
[0039] In traditional technology, when a bidirectional interleaved parallel boost converter malfunctions during operation, all four switches S1-S4 are blocked, meaning the boost converter loses its boost function. However, since the second switch S2 and the third switch S3 both have body diodes, when the switches are blocked, the energy from the battery side of the bidirectional interleaved parallel boost converter, connected to the power battery, will be transferred to the bus side through S2 and S3, charging the bus capacitor Cbus. Because the body diode has a large voltage drop and carries a large current, it bears a significant power load. If the bus capacitor Cbus is normally providing a large amount of energy to the hybrid electric system at this time, prolonged operation could cause the second switch S2 and the third switch S3 to overheat and fail, potentially leading to the entire system malfunctioning.
[0040] In order to solve the above-mentioned technical problems, this application provides a technical solution that can control the second and third switching transistors to shoot through at an appropriate time when a bidirectional interleaved parallel BOOST converter fails, thereby avoiding energy transfer from the body diode of the switching transistors, which would cause the body diode to overheat and damage the switching transistors.
[0041] The bidirectional interleaved parallel BOOST converter provided in this application embodiment is not specifically limited to any particular application scenario. It can be applied to the field of hybrid electric vehicles, as well as other technical fields, as long as a DC-DC scenario requiring a bidirectional interleaved parallel BOOST converter for boost conversion is needed. For ease of understanding, the following embodiments use the application of the bidirectional interleaved parallel BOOST converter in a hybrid electric system as an example for description.
[0042] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.
[0043] See Figure 2 This figure is a schematic diagram of a BOOST converter provided in an embodiment of this application.
[0044] The BOOST converter provided in this application embodiment includes: a first inductor L1, a second inductor L2, a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4;
[0045] The first terminal of the first inductor L1 and the first terminal of the second inductor L2 are both used to connect to the positive terminal of the DC power supply. The second terminal of the first inductor L1 is connected to the first terminal of the bus capacitor through the second switch S2. The second terminal of the second inductor L2 is connected to the first terminal of the bus capacitor Cbus through the third switch S3. The first switch S1 is connected between the second terminal of the first inductor L1 and the negative terminal of the DC power supply. The fourth switch S4 is connected between the second terminal of the second inductor L2 and the negative terminal of the DC power supply.
[0046] When the BOOST converter fails, the first switch S1, the second switch S2, the third switch S3 and the fourth switch S4 are all blocked; when the difference between the voltage of the DC power supply and the voltage of the bus capacitor Cbus is less than or equal to a preset voltage threshold, the second switch S2 and the third switch S3 are turned on to protect the second switch S2 and the third switch S3.
[0047] This application uses a DC power source as an example for illustration.
[0048] In this embodiment, the specific value of the preset voltage threshold is not limited; for example, it can be 5V, which is the safe voltage range that the body diode can withstand. If the voltage of the DC power supply differs significantly from the voltage of the bus capacitor, controlling the second and third switching transistors to be directly connected would result in an excessively large inrush current, which is unsafe. The second and third switching transistors are only controlled to be directly connected when the voltage difference between the DC power supply and the bus capacitor is small, i.e., when the voltage difference is small; in this case, the inrush current is smaller.
[0049] For example, taking a power battery voltage of 250V, a bus capacitor Cbus voltage of 450V, and a bidirectional interleaved parallel BOOST converter operating at full load as an example, a fault occurs during operation.
[0050] When a fault occurs in the bidirectional interleaved parallel BOOST converter, controls S1, S2, S3, and S4 are all blocked. At this time, the bidirectional interleaved parallel BOOST converter loses its boost function and can no longer provide energy to the bus capacitor Cbus. Meanwhile, the motor system MS2 is still running at full load, and the voltage on the bus capacitor Cbus will drop rapidly. When the voltage on the bus capacitor Cbus is ≤ (Vbat - body diode voltage drop), the body diodes of S2 and S3 will conduct. During the voltage drop, if the voltage difference between the bus voltage Vbus and the battery voltage Vbat is detected to be < a preset voltage threshold, the second switch S2 and the third switch S3 will be directly controlled to conduct. That is, when S2 and S3 are conducting, the energy from the power battery reaches the bus capacitor Cbus through S2 and S3, instead of through the body diodes of S2 and S3.
[0051] After the fault of the bidirectional interleaved parallel BOOST converter is cleared, the bidirectional interleaved parallel BOOST converter restarts slowly, raising the voltage of the bus capacitor Cbus back to 450V. During the slow start-up process, the pulse width of the drive signals of the first switch S1 and the fourth switch S4 gradually increases, while the pulse width of the drive signals of the second switch S2 and the third switch S3 gradually decreases, that is, from a direct pulse width to a gradual decrease.
[0052] The technical solution provided in this application does not directly switch the second switch S2 and the third switch S3 immediately upon the occurrence of a fault in the bidirectional interleaved parallel BOOST converter. This is because the voltage of the bus capacitor Cbus is 450V, the voltage of the power battery is 250V, and there is only an inductor between them with very low impedance. A large inrush current would cause the second switch S2 and the third switch S3 to be damaged due to excessive current stress. Instead, the second and third switches are controlled to be switched on only when the voltage difference between the power battery and the bus capacitor is small. This ensures that the body diode does not overheat and avoids excessive inrush current.
[0053] The BOOST converter provided in this embodiment also includes: a voltage detection circuit (not shown in the figure) and a controller 100;
[0054] Voltage detection circuit, used to detect the voltage of DC power supply and bus capacitor;
[0055] The controller 100 is used to control the first switch S1, the second switch S2, the third switch S3 and the fourth switch S4 to block the waveform when the BOOST converter fails, and to control the second switch S2 and the third switch S3 to turn on when the difference between the voltage of the DC power supply and the voltage of the bus capacitor is less than or equal to a preset voltage threshold.
[0056] The BOOST converter provided in this application embodiment does not specifically limit the specific type of fault. Any fault requiring waveform blocking can be addressed by applying the technical solutions provided in this application. For example, the controller is also used to determine whether the BOOST converter has failed based on at least one of the voltage, current, or temperature of the BOOST converter.
[0057] The voltage can be at least one of the input voltage or the output voltage, and the current can be at least one of the input current or the output current.
[0058] This application does not specifically limit the specific type of each switching transistor, as long as it is a controllable switching transistor. For example, the first switching transistor, the second switching transistor, the third switching transistor, and the fourth switching transistor are all MOSFETs.
[0059] Based on the BOOST converter provided in the above embodiments, this application also provides a hybrid electric system, which will be described in detail below with reference to the accompanying drawings.
[0060] See Figure 3 The figure is a schematic diagram of a hybrid electric system provided in an embodiment of this application.
[0061] The hybrid electric system provided in this embodiment includes the BOOST converter described in the above embodiments, and also includes: a generator system MS1 and a motor system MS2; wherein, the generator system MS1 includes a first motor M1, and the motor system MS2 includes a second motor M2.
[0062] Both generator system MS1 and motor system MS2 are connected to bus capacitor Cbus;
[0063] The DC power source is a power battery.
[0064] The battery side of the BOOST converter is connected to the first capacitor C1, and the two ends of C1 are connected to the two ends of the power battery (not shown in the figure).
[0065] The hybrid electric system provided in this embodiment can, in the event of a BOOST converter failure, first block all switches in the BOOST converter. By detecting the voltage of the power battery and the voltage of the bus capacitor, when the voltage difference between the two is less than or equal to a preset voltage threshold, the second and third switches are then controlled to be directly connected. This prevents the energy of the power battery from being transferred to the bus capacitor through the body diodes of the second and third switches, thereby preventing the body diodes from overheating and damaging the switches. Furthermore, controlling the second and third switches to be directly connected when the voltage difference is small can prevent excessive inrush current caused by a large voltage difference, thus protecting the switches.
[0066] Based on the BOOST converter and hybrid electric system provided in the above embodiments, this application also provides a control method for the BOOST converter, which will be described in detail below with reference to the accompanying drawings.
[0067] See Figure 4 The figure is a flowchart of a control method for a BOOST converter provided in an embodiment of this application.
[0068] The control method for the BOOST converter provided in this embodiment includes a BOOST converter comprising: a first inductor, a second inductor, a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor; the first terminals of the first inductor and the second inductor are both connected to the positive terminal of the DC power supply; the second terminal of the first inductor is connected to the first terminal of the bus capacitor through the second switching transistor; the second terminal of the second inductor is connected to the first terminal of the bus capacitor through the third switching transistor; the first switching transistor is connected between the second terminal of the first inductor and the negative terminal of the DC power supply; and the fourth switching transistor is connected between the second terminal of the second inductor and the negative terminal of the DC power supply.
[0069] The method includes:
[0070] S401: When the BOOST converter fails, the first, second, third, and fourth switching transistors all block the waveform;
[0071] S402: When the difference between the voltage of the DC power supply and the voltage of the bus capacitor is less than or equal to a preset voltage threshold, control the second and third switching transistors to turn on in order to protect the second and third switching transistors.
[0072] This application does not specifically limit the specific value of the preset voltage threshold. For example, it can be 5V or other values can be selected. It does not specifically limit whether the voltage of the DC power supply is higher or the voltage of the bus capacitor is higher. As long as the absolute value of the voltage difference between the two is less than or equal to the preset voltage threshold, the second and third switching transistors can be controlled to be directly connected.
[0073] Specifically, the voltage of the DC power supply and the voltage of the bus capacitor can be detected by a voltage detection circuit. In hybrid electric systems, the DC power supply can be a battery. The bus capacitor also connects the generator system and the motor system.
[0074] The technical solution provided in this application does not directly switch the second and third switching transistors immediately upon the occurrence of a fault in the bidirectional interleaved parallel BOOST converter. This is because the voltage of the bus capacitor Cbus is 450V, while the voltage of the power battery is 250V. Furthermore, there is only an inductor between them, resulting in very low impedance. A large inrush current would cause the second and third switching transistors to be damaged due to excessive current stress. Instead, the second and third switching transistors are controlled to switch on only when the voltage difference between the power battery and the bus capacitor is small. This ensures that the body diode does not overheat and avoids excessive inrush current.
[0075] In addition, the method provided in this application embodiment may also include the following steps:
[0076] After the fault of the bidirectional interleaved parallel BOOST converter is cleared, the bidirectional interleaved parallel BOOST converter restarts slowly, raising the voltage of the bus capacitor Cbus back to 450V. During the slow start-up process, the pulse width of the drive signals of the first and fourth switches gradually increases, while the pulse width of the drive signals of the second and third switches gradually decreases, that is, from a direct pulse width to a gradual decrease.
[0077] This application does not specifically limit the type of fault that occurs in the BOOST converter. Specifically, the method further includes: determining whether the BOOST converter has failed based on at least one of the following: voltage, current, or temperature. That is, one of the above can be used to determine whether the BOOST converter has failed, or multiple of the above can be used to determine whether the BOOST converter has failed.
[0078] The voltage can be either the battery-side voltage or the bus voltage of the BOOST converter, and the current can be either the battery-side current or the bus-side current.
[0079] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems or apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.
[0080] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A BOOST converter, characterized in that, include: First inductor, second inductor, first switching transistor, second switching transistor, third switching transistor, and fourth switching transistor; The first end of the first inductor and the first end of the second inductor are both used to connect to the positive terminal of the DC power supply. The second end of the first inductor is connected to the first end of the bus capacitor through the second switching transistor. The second end of the second inductor is connected to the first end of the bus capacitor through the third switching transistor. The first switching transistor is connected between the second end of the first inductor and the negative terminal of the DC power supply. The fourth switching transistor is connected between the second end of the second inductor and the negative terminal of the DC power supply. When the BOOST converter fails, the first, second, third, and fourth switches are all blocked; when the difference between the voltage of the DC power supply and the voltage of the bus capacitor is less than or equal to a preset voltage threshold, the second and third switches are turned on to protect the second and third switches.
2. The converter according to claim 1, characterized in that, Also includes: Voltage detection circuit and controller; The voltage detection circuit is used to detect the voltage of the DC power supply and the voltage of the bus capacitor; The controller is configured to, when the BOOST converter fails, control the first switch, the second switch, the third switch and the fourth switch to block the waveform, and when the difference between the voltage of the DC power supply and the voltage of the bus capacitor is less than or equal to a preset voltage threshold, control the second switch and the third switch to turn on.
3. The converter according to claim 2, characterized in that, The controller is further configured to determine whether the BOOST converter has malfunctioned based on at least one of the voltage, current, or temperature of the BOOST converter.
4. The converter according to claim 2, characterized in that, The controller is further configured to, after the BOOST converter fault is cleared, gradually increase the pulse width of the drive signals of the first switch and the fourth switch, and gradually decrease the pulse width of the drive signals of the second switch and the third switch.
5. A hybrid electric system, characterized in that, The BOOST converter according to any one of claims 1-4 further includes: a generator system and a motor system; Both the generator system and the motor system are connected to the bus capacitor; The DC power source is a power battery.
6. A control method for a BOOST converter, characterized in that, The BOOST converter includes: a first inductor, a second inductor, a first switching transistor, a second switching transistor, a third switching transistor, and a fourth switching transistor; the first end of the first inductor and the first end of the second inductor are both used to connect to the positive terminal of the DC power supply; the second end of the first inductor is connected to the first end of the bus capacitor through the second switching transistor; the second end of the second inductor is connected to the first end of the bus capacitor through the third switching transistor; the first switching transistor is connected between the second end of the first inductor and the negative terminal of the DC power supply; and the fourth switching transistor is connected between the second end of the second inductor and the negative terminal of the DC power supply. The method includes: When the BOOST converter fails, the first switch, the second switch, the third switch, and the fourth switch all block the waveform. When the difference between the voltage of the DC power supply and the voltage of the bus capacitor is less than or equal to a preset voltage threshold, the second switch and the third switch are controlled to be turned on to protect the second switch and the third switch.
7. The control method according to claim 6, characterized in that, Also includes: The voltage of the DC power supply and the voltage of the bus capacitor are detected.
8. The control method according to claim 6 or 7, characterized in that, Also includes: Determine whether the BOOST converter has malfunctioned based on at least one of the voltage, current, or temperature of the BOOST converter.
9. The control method according to claim 6 or 7, characterized in that, The DC power source is a power battery.
10. The control method according to claim 9, characterized in that, The bus capacitor is also connected to the generator system and the motor system.