Split type two-stage electric composite pressurization system and control method

Abstract

The invention aims to provide a split type two-stage electric composite supercharging system and a control method, the split type two-stage electric composite supercharging system comprises an engine, a high-pressure-stage supercharger, a low-pressure-stage supercharger, a motor and a generator, the low-pressure-stage supercharger comprises a low-pressure-stage power turbine and a low-pressure-stage gas compressor, the low-pressure-stage power turbine is connected with the generator, and the low-pressure-stage gas compressor is connected with the motor; the air inlet pressure during operation is compared with the target air inlet pressure through the ECU, then a reasonable control strategy is made according to the operation states under different working conditions, and therefore the target air inlet requirement is met. According to the method, the air inlet pressure can be guaranteed, meanwhile, quick response to the air inlet requirement is achieved, the defects of turbine response lag, low efficiency, poor low-working-condition performance and the like of a traditional supercharger are overcome, and the good performance of an engine can be kept under various working conditions through a reasonable control strategy.

Description

Technical Field

[0001] The present invention relates to an engine and its control method, specifically a supercharging system and its control method. Background Art

[0002] Supercharging technology is one of the effective methods to achieve high intensification of engine performance, but it has limitations such as turbo lag, overspeed, surge, poor performance at low engine speeds, and excessive energy at high engine speeds. With the continuous improvement of the requirements for high supercharging, high power, and economy of engines, traditional single-stage turbocharging can no longer meet the intake requirements of engines.

[0003] In existing supercharging technologies, two-stage supercharging technology can meet the requirements of high supercharging ratio, but its performance at low operating conditions is poor and the power response is lagged. Sequential supercharging technology can well improve the performance at low operating conditions, but it cannot provide a very high supercharging pressure. Electric compound turbocharging technology uses the fast response of the motor to solve the problems of turbo lag and narrow operating condition matching range commonly existing in turbocharging technology. However, the existing single-stage electric turbo compound supercharging technology provides a limited pressure ratio and cannot make full use of the engine exhaust gas energy like two-stage supercharging technology, resulting in waste of excess exhaust gas energy. Especially for large engines, the utilization of exhaust gas energy is particularly important for economy. Summary of the Invention

[0004] The purpose of the present invention is to provide a split two-stage electric compound supercharging system and its control method that can quickly meet the intake demand at low engine speeds and transient operating conditions, so that the engine can always maintain excellent power performance, economy, and emission characteristics.

[0005] The purpose of the present invention is achieved as follows:

[0006] A split - type two - stage electric compound supercharging system of the present invention is characterized in that it includes an engine, a high - pressure stage supercharger, a low - pressure stage supercharger, an electric motor, a generator, an intake manifold, and an exhaust manifold. The high - pressure stage supercharger includes a high - pressure stage turbine and a high - pressure stage compressor, and the high - pressure stage turbine and the high - pressure stage compressor are coaxial. The low - pressure stage supercharger includes a low - pressure stage power turbine and a low - pressure stage compressor. The low - pressure stage power turbine is connected to the generator, and the low - pressure stage compressor is connected to the electric motor. Both the generator and the electric motor are connected to a storage battery. The inlet of the high - pressure stage turbine is connected to a high - pressure stage exhaust pipe, and the outlet of the high - pressure stage turbine is connected to a low - pressure stage exhaust pipe. The high - pressure stage exhaust pipe is respectively connected to the exhaust manifold and a high - pressure stage exhaust gas bypass pipe, and the high - pressure stage exhaust gas bypass pipe is connected to the low - pressure stage exhaust pipe. The inlet of the low - pressure stage power turbine is connected to the low - pressure stage exhaust pipe, and the outlet of the low - pressure stage power turbine is connected to an exhaust main pipe. Both the low - pressure stage exhaust pipe and the exhaust main pipe are connected to a low - pressure stage exhaust gas bypass pipe. The inlet of the low - pressure stage compressor is connected to an intake main pipe, and the outlet of the low - pressure stage compressor is connected to a low - pressure stage intake pipe. Both the intake main pipe and the low - pressure stage intake pipe are connected to an intake bypass pipe. The inlet of the high - pressure stage compressor is connected to the low - pressure stage intake pipe, and the outlet of the high - pressure stage compressor is connected to a high - pressure stage intake pipe. The high - pressure stage intake pipe is connected to the intake manifold.

[0007] A split - type two - stage electric compound supercharging system of the present invention may further include:

[0008] It further includes an ECU. A high - pressure stage exhaust gas bypass valve is installed on the high - pressure stage exhaust gas bypass pipe, a low - pressure stage exhaust gas bypass valve is installed on the low - pressure stage exhaust gas bypass pipe, and an intake bypass valve is installed on the intake bypass pipe. A low - pressure stage intercooler and an intake cut - off valve are installed on the low - pressure stage intake pipe, and the intake cut - off valve is located downstream of the low - pressure stage intercooler. A high - pressure stage intercooler is installed on the high - pressure stage intake pipe. Speed sensors are respectively installed on the engine flywheel, the shaft of the high - pressure stage supercharger, the shaft of the electric motor, and the shaft of the generator. Temperature - pressure sensors are respectively installed on the high - pressure stage intake pipe downstream of the high - pressure stage intercooler, the low - pressure stage intake pipe downstream of the low - pressure stage intercooler, the high - pressure stage exhaust pipe, the low - pressure stage exhaust pipe, the intake main pipe, and the exhaust main pipe. The ECU is connected to all the speed sensors, temperature - pressure sensors, the high - pressure stage exhaust gas bypass valve, the low - pressure stage exhaust gas bypass valve, and the intake bypass valve.

[0009] A split - type two - stage electric compound supercharging control method of the present invention is characterized in that it adopts a split - type two - stage electric compound supercharging system. According to the target power of the engine under different working conditions, the target intake pressure and the total supercharging ratio are calculated and their target values are stored in the ECU. The ECU continuously monitors the target intake pressure and the real - time intake pressure in the current supercharging mode. If there is a difference, the supercharging mode, the speed of the electric motor, and the opening degree of the exhaust gas bypass valve are selected to ensure that the supercharging system can provide the target intake pressure under various working conditions, specifically as follows:

[0010] Under the idle condition, the ECU monitors the intake pressure in real time and compares it with the preset target intake pressure. If the intake pressure is lower than the target intake pressure at this time, and the intake pressure is still lower than the target intake pressure after the high-pressure stage waste gas bypass valve is fully closed, the intake cut-off valve is opened and the intake bypass valve is closed, the high-pressure stage waste gas bypass valve is closed, and the low-pressure stage compressor is cut into operation, entering the two-stage supercharging mode. The air is first compressed by the low-pressure stage compressor, then cooled by the low-pressure stage intercooler, enters the high-pressure stage compressor for further compression, and then cooled by the high-pressure stage intercooler to become high-pressure and high-density gas. Subsequently, it is sent into the engine cylinder through the intake manifold. The ECU calculates the required pressure ratio of the low-pressure stage based on the difference between the target total pressure ratio and the high-pressure stage pressure ratio, and then regulates the speed of the motor according to the low-pressure stage pressure ratio to ensure the target intake air demand.

[0011] A split two-stage electric composite supercharging control method of the present invention may further include:

[0012] 1. Under the low-speed condition, the ECU detects the intake pressure in the supercharging mode at this time. At this time, it is in the two-stage supercharging mode of the low-pressure stage supercharger and the high-pressure stage supercharger, and the control strategy is the same as that under the idle condition; if the intake pressure is higher than the target value, first reduce the motor speed to lower the intake pressure; if the motor speed drops to the lowest and the intake pressure is still higher than the target value, open the intake bypass valve, close the intake cut-off valve 8 to stop the motor from working, cut out the low-pressure stage compressor, and enter the high-pressure stage single-stage supercharging mode, and adjust the high-pressure stage waste gas bypass valve to achieve the target intake pressure.

[0013] 2. Under the medium-speed condition, the waste gas energy meets the supercharging requirement, and it is in the single-stage supercharging mode. The ECU monitors the intake pressure in real time and compares it with the preset target intake pressure; as the load increases, the intake pressure decreases. When it is lower than the target intake pressure, the ECU adjusts the opening of the high-pressure stage waste gas bypass valve to make more waste gas flow into the high-pressure stage turbine to ensure that the intake pressure reaches the target level; when the engine load further increases and the intake pressure still cannot reach the target value even when the high-pressure stage waste gas bypass valve is fully closed, the ECU opens the intake cut-off valve and closes the intake bypass valve, cuts into the low-pressure stage compressor for operation, and enters the two-stage supercharging mode in which the low-pressure stage supercharger and the high-pressure stage supercharger work together. The control strategy is consistent with that under the low-speed condition to ensure that the engine can obtain the best intake pressure support under different loads.

[0014] 3. Under the high-speed condition, the high-pressure stage supercharger alone supercharging mode is adopted, and the intake pressure is controlled by adjusting the opening of the high-pressure stage waste gas bypass valve to meet the requirement of the target intake pressure; if the waste gas flow is too large, open the high-pressure stage waste gas bypass valve and the low-pressure stage waste gas bypass valve and control the opening.

[0015] The advantages of the present invention are as follows: The present invention can achieve a rapid response to the intake air demand while ensuring the intake air pressure, overcoming the defects of traditional superchargers such as lagging turbine response, low efficiency, and poor performance under low load conditions. Through a reasonable control strategy, the engine can maintain good performance under various working conditions. At the same time, the present invention makes full use of the waste gas energy and reduces energy waste, which is of great significance to the economy and environmental protection of large engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of the present invention;

[0017] Figure 2 is a flow chart of the present invention;

[0018] Figure 3 is a schematic diagram of single-stage supercharging of the high-pressure stage adopted by the present invention;

[0019] Figure 4 is a schematic diagram of two-stage supercharging of the present invention.

[0020] In the figure: air filter 1, intake main pipe 2, intake bypass pipe 3, low-pressure stage compressor 4, intake bypass valve 5, low-pressure stage intake pipe 6, low-pressure stage intercooler 7, intake cut-off valve 8, high-pressure stage compressor 9, high-pressure stage intake pipe 10, exhaust manifold 11, high-pressure stage intercooler 12, temperature and pressure sensor 13, engine 14, intake manifold 15, engine speed sensor 16, electronic control unit ECU 17, high-pressure stage exhaust pipe 18, high-pressure stage exhaust gas bypass pipe 19, high-pressure stage exhaust gas bypass valve 20, high-pressure stage supercharger 21, high-pressure stage turbine 22, storage battery 23, low-pressure stage exhaust pipe 24, low-pressure stage power turbine 25, low-pressure stage exhaust gas bypass valve 26, low-pressure stage exhaust gas bypass pipe 27, exhaust main pipe 28, muffler 29, low-pressure stage supercharger 30, electric motor 31, generator 32. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The present invention will be described in more detail with reference to the accompanying drawings as follows:

[0022] Combined with Figures 1-4 , a split two-stage electric compound turbocharging system of the present invention includes: engine 14, high-pressure stage supercharger 21, low-pressure stage supercharger 30. The high-pressure stage supercharger 21 includes a high-pressure stage turbine 22 and a high-pressure stage compressor 9; the low-pressure stage supercharger 30 includes a low-pressure stage compressor 4 and a low-pressure stage power turbine 25 arranged separately. The low-pressure stage compressor is driven by an electric motor 31, and the low-pressure stage power turbine drives a generator 32; the system also includes a low-pressure stage intercooler 7, a high-pressure stage intercooler 12, an intake bypass valve 5, an intake cut-off valve 8, a high-pressure stage exhaust gas bypass valve 20, a low-pressure stage exhaust gas bypass valve 26, a storage battery 23, a temperature and pressure sensor 13, a speed sensor 16, an electronic control unit ECU 17, etc.

[0023] The positions and connections of each component in the system are as follows:

[0024] The inlet of the high-pressure stage turbine 22 is connected to the high-pressure stage exhaust pipe 18, and the outlet is connected to the low-pressure stage exhaust pipe 24. The high-pressure stage exhaust gas bypass pipe 19 is connected to the high-pressure stage exhaust pipe 18 and the low-pressure stage exhaust pipe 24. The exhaust gas of the engine exhaust manifold 11 is divided into two paths and flows into the high-pressure stage exhaust pipe 18 and the high-pressure stage exhaust gas bypass pipe 19 respectively. A high-pressure stage exhaust gas bypass valve 20 is provided on the high-pressure stage exhaust gas bypass pipe 19.

[0025] The inlet of the low-pressure stage power turbine 25 is connected to the low-pressure stage exhaust pipe 24, the outlet is connected to the exhaust manifold 28, and it is itself connected to the generator 32. The generator 32 is electrically connected to the battery 23. The low-pressure stage exhaust gas bypass pipe 27 is connected to the low-pressure stage exhaust pipe 24 and the exhaust manifold 28, and a low-pressure stage exhaust gas bypass valve 26 is provided on the low-pressure stage exhaust gas bypass pipe 27.

[0026] The inlet of the low-pressure stage compressor 4 is connected to the intake manifold 2, and the intake manifold 2 is also connected to the air filter 1 at the same time. The outlet is connected to the low-pressure stage intake pipe 6. The low-pressure stage compressor 4 is itself connected to the motor 31, and at the same time the motor 31 is electrically connected to the battery 23. A low-pressure stage intercooler 7 and an intake cut-off valve 8 are provided on the low-pressure stage intake pipe 6, and the intake cut-off valve 8 is located downstream of the low-pressure stage intercooler 7. The low-pressure stage intake bypass pipe 3 is connected to the intake manifold 2 and the low-pressure stage intake pipe 6, and an intake bypass valve 5 is provided thereon.

[0027] The inlet of the high-pressure stage compressor 9 is connected to the low-pressure stage intake pipe 6, and the outlet is connected to the high-pressure stage intake pipe 10. The high-pressure stage intake pipe 10 is connected to the engine intake manifold 15, and a high-pressure stage intercooler 12 is provided on the high-pressure stage intake pipe 10.

[0028] The rotational speed sensors 16 are arranged on the engine flywheel, the high-pressure stage supercharger shaft, the motor 31 shaft, and the generator 32 shaft. Temperature and pressure sensors 13 are provided on the high-pressure stage intake pipe 10 downstream of the high-pressure stage intercooler 12, the low-pressure stage intake pipe 6 downstream of the low-pressure stage intercooler 7, the high-pressure stage exhaust pipe 18, the low-pressure stage exhaust pipe 24, the intake manifold 2, and the exhaust manifold 28. The electronic control unit ECU17 receives the sensor information and makes a control strategy under the current working conditions.

[0029] The opening degrees of both the high-pressure stage exhaust gas bypass valve 20 and the low-pressure stage exhaust gas bypass valve 26 are adjustable, the rotational speed of the motor 31 is adjustable, and the low-pressure stage power turbine 25 and the generator 32 are always in a working state during operation.

[0030] The specific steps of a split two-stage electric compound supercharging control method of the present invention are as follows:

[0031] First, according to the target power of the engine under different working conditions, the target intake pressure and the total boost ratio are calculated, and their target values are stored in the electronic control unit ECU17.

[0032] The electronic control unit ECU17 continuously monitors the target intake pressure and the real-time intake pressure in the current boost mode. If there is a difference, by selecting an appropriate boost mode, as well as the speed of the motor 31 and the opening degree of the waste gas bypass valve 20, it ensures that the boost system can provide the target intake pressure under various working conditions. The specific control strategy is as follows:

[0033] A1: At idle speed, the waste gas flow is small and not enough to rely solely on the waste gas energy to make the boost system provide the target intake. At this time, the electronic control unit ECU17 monitors the intake pressure in real time and compares it with the preset target intake pressure. If the intake pressure is lower than the target intake pressure at this time, and after the high-pressure stage waste gas bypass valve 20 is fully closed, the intake pressure is still lower than the target intake pressure. At this time, open the intake cut-off valve 8 and close the intake bypass valve 5, close the high-pressure stage waste gas bypass valve 20, and the low-pressure stage compressor 4 cuts in to operate, entering the two-stage boost mode. The air is first compressed by the low-pressure stage compressor 4, then cooled by the low-pressure stage intercooler 7, enters the high-pressure stage compressor 9 for further compression, and then cooled by the high-pressure stage intercooler 12 to become high-pressure and high-density gas, and then is sent into the engine cylinder through the intake manifold 15. The electronic control unit ECU17 calculates the required pressure ratio of the low-pressure stage according to the difference between the target total pressure ratio and the high-pressure stage pressure ratio, and then adjusts the speed of the motor 31 according to the low-pressure stage pressure ratio to ensure the target intake demand and make the engine operate efficiently.

[0034] A2: At low speed, the electronic control unit ECU17 first detects the intake pressure in the current boost mode. Since the low-speed condition is transitioned from the idle speed condition, usually it is in the two-stage boost mode of the low-pressure stage supercharger 30 + the high-pressure stage supercharger 21 at this time. Therefore, the control strategy at this time is the same as that of A1 under the idle speed condition; if the intake pressure is higher than the target value, first reduce the speed of the motor 31 to reduce the intake pressure. If the speed of the motor 31 drops to the lowest and the intake pressure is still higher than the target value, open the intake bypass valve 5, close the intake cut-off valve 8, stop the motor 31 from working, cut out the low-pressure stage compressor 4, and enter the high-pressure stage single-stage boost 21 mode, and adjust the high-pressure stage waste gas bypass valve to achieve the target intake pressure.

[0035] A3: Under medium engine speed conditions, when the load is relatively small, the exhaust gas energy can meet the supercharging requirements, and it is usually in the single-stage supercharging mode. The electronic control unit ECU17 will monitor the intake pressure in real time and compare it with the preset target intake pressure. As the load gradually increases, the intake pressure will also gradually decrease. When it is lower than the target intake pressure, the ECU will adjust the opening degree of the high-pressure stage exhaust gas bypass valve 20 to allow more exhaust gas to flow into the high-pressure stage turbine 22, thereby improving its working efficiency and ensuring that the intake pressure reaches the target level. When the engine load further increases and the intake pressure still cannot reach the target value even when the high-pressure stage exhaust gas bypass valve 20 is fully closed, the system will initiate further adjustment measures. At this time, the ECU will open the intake cut-off valve 8 and close the intake bypass valve 5, and switch to the operation of the low-pressure stage compressor 4, so that the system enters the two-stage supercharging mode where the low-pressure stage supercharger 30 and the high-pressure stage supercharger 21 work together. In this mode, the control strategy of the system is the same as that in the low engine speed condition A2 to ensure that the engine can obtain the best intake pressure support under different loads, thereby achieving efficient and stable operation.

[0036] A4: Under high engine speed conditions, the engine generates a large amount of exhaust gas, which is sufficient to meet the needs of the supercharging system. At this time, the system adopts the single supercharging mode of the high-pressure stage supercharger 21, and precisely controls the intake pressure by adjusting the opening degree of the high-pressure stage exhaust gas bypass valve 20 to meet the requirements of the target intake pressure. However, if the exhaust gas flow is too large at this time, to prevent the high-pressure stage turbine 22 and the low-pressure stage power turbine 25 from overspeeding, the high-pressure stage exhaust gas bypass valve 20 and the low-pressure stage exhaust gas bypass valve 26 can be opened to a certain degree.

[0037] Based on ensuring the intake pressure, the present invention can quickly respond to the intake demand, effectively solve problems such as turbine response lag, low efficiency, and poor performance under low working conditions. Through a reasonable control strategy, the engine can achieve excellent performance under different working conditions. In addition, the system makes full use of the exhaust gas energy, significantly reducing energy waste, which is of great significance to the economy and environmental protection of large engines.

Claims

1. A split two-stage electric compound supercharging system, characterized by: The invention comprises an engine, a high-pressure supercharger, a low-pressure supercharger, an electric motor, a generator, an intake manifold, and an exhaust manifold. The high-pressure supercharger comprises a high-pressure turbine and a high-pressure compressor. The high-pressure turbine is coaxial with the high-pressure compressor. The low-pressure supercharger comprises a low-pressure power turbine and a low-pressure compressor. The low-pressure power turbine is connected to the generator, the low-pressure compressor is connected to the electric motor, and the generator and the electric motor are both connected to the battery. The inlet of the high-pressure turbine is connected to the high-pressure exhaust pipe, the outlet of the high-pressure turbine is connected to the low-pressure exhaust pipe, and the high-pressure exhaust pipe is respectively connected to the exhaust manifold. , a high-pressure stage exhaust gas bypass pipe, the high-pressure stage exhaust gas bypass pipe is connected to the low-pressure stage exhaust pipe; the inlet of the low-pressure stage power turbine is connected to the low-pressure stage exhaust pipe, the outlet of the low-pressure stage power turbine is connected to the exhaust manifold, and both the low-pressure stage exhaust pipe and the exhaust manifold are connected to the low-pressure stage exhaust gas bypass pipe; the inlet of the low-pressure stage compressor is connected to the intake manifold, the outlet of the low-pressure stage compressor is connected to the low-pressure stage intake pipe, the intake manifold and the low-pressure stage intake pipe are both connected to the intake bypass pipe, the inlet of the high-pressure stage compressor is connected to the low-pressure stage intake pipe, the outlet of the high-pressure stage compressor is connected to the high-pressure stage intake pipe, and the high-pressure stage intake pipe is connected to the intake manifold.

2. A split two-stage electric compound supercharging system according to claim 1, characterized in that: It also includes an ECU. A high-pressure exhaust bypass valve is installed on the high-pressure exhaust bypass pipe, a low-pressure exhaust bypass valve is installed on the low-pressure exhaust bypass pipe, and an intake bypass valve is installed on the intake bypass pipe; a low-pressure intercooler and an intake stop valve are installed on the low-pressure intake pipe, the intake stop valve is located downstream of the low-pressure intercooler, and the high-pressure intercooler is installed on the high-pressure intake pipe; speed sensors are installed on the engine flywheel, the shaft of the high-pressure supercharger, the shaft of the electric motor, and the shaft of the generator respectively; temperature and pressure sensors are installed on the high-pressure intake pipe downstream of the high-pressure intercooler, on the low-pressure intake pipe downstream of the low-pressure intercooler, on the high-pressure exhaust pipe, on the low-pressure exhaust pipe, on the intake manifold and on the exhaust manifold respectively; the ECU is connected to all speed sensors, temperature and pressure sensors, as well as the high-pressure exhaust bypass valve, the low-pressure exhaust bypass valve and the intake bypass valve.

3. A split two-stage electric compound supercharging control method, characterized in that: Using a split two-stage electric compound supercharging system as claimed in claim 2, the target intake pressure and the total boost ratio are calculated according to the target power of the engine under different working conditions, and the target values ​​are stored in the electric ECU; The ECU continuously monitors the target intake pressure and the real-time intake pressure in the current boost mode. If there is a difference, the ECU selects the boost mode, motor speed and wastegate valve opening to ensure that the boost system can provide the target intake pressure under various operating conditions, as follows: During idling conditions, the ECU monitors the intake pressure in real time and compares it with the preset target intake pressure. If the intake pressure is lower than the target intake pressure at this time, and the intake pressure is still lower than the target intake pressure after the high-pressure stage exhaust bypass valve is fully closed, the intake shut-off valve is opened and the intake bypass valve is closed, the high-pressure stage exhaust bypass valve is closed, and the low-pressure stage compressor is cut into operation to enter the two-stage supercharging mode. The air is first compressed by the low-pressure stage compressor, and then cooled by the low-pressure stage intercooler. It enters the high-pressure stage compressor for compression again, and then cools down by the high-pressure stage intercooler to become a high-pressure and high-density gas, which is then sent into the engine cylinder through the intake manifold. The ECU calculates the pressure ratio required for the low-pressure stage based on the difference between the target total pressure ratio and the high-pressure stage pressure ratio, and then adjusts the speed of the motor based on the low-pressure stage pressure ratio to ensure the target intake demand.

4. A split two-stage electric compound supercharging control method according to claim 3, characterized in that: Under low speed conditions, the ECU detects the intake pressure under the boost mode at this time. At this time, it is in a two-stage boost mode of the low-pressure stage supercharger and the high-pressure stage supercharger. The control strategy at this time is the same as that under the idle condition; if the intake pressure is higher than the target value, the intake pressure is first reduced by reducing the motor speed; if the motor speed drops to the minimum and the intake pressure is still higher than the target value, the intake bypass valve is opened, the intake stop valve 8 is closed to stop the motor, the low-pressure stage compressor is cut out, and the high-pressure stage single-stage boost mode is entered, and the target intake pressure is achieved by adjusting the high-pressure stage exhaust bypass valve.

5. A split two-stage electric compound supercharging control method according to claim 3, characterized in that: At medium speed, the exhaust gas energy meets the boost requirement and is in single-stage boost mode. The ECU monitors the intake pressure in real time and compares it with the preset target intake pressure. As the load increases, the intake pressure decreases. When it is lower than the target intake pressure, the ECU adjusts the opening of the high-pressure stage exhaust bypass valve to allow more exhaust gas to flow into the high-pressure stage turbine to ensure that the intake pressure reaches the target level. When the engine load increases further, even if the high-pressure stage exhaust bypass valve is completely closed, the intake pressure still cannot reach the target value. The ECU opens the intake shut-off valve and closes the intake bypass valve, switches on the low-pressure stage compressor, and enters a two-stage boost mode in which the low-pressure stage supercharger and the high-pressure stage supercharger work together. The control strategy is consistent with the low-speed condition to ensure that the engine can obtain the best intake pressure support under different loads.

6. A split two-stage electric compound supercharging control method according to claim 3, characterized in that: Under high-speed conditions, the high-pressure stage supercharger is used in a separate boost mode, and the intake pressure is controlled by adjusting the opening of the high-pressure stage exhaust bypass valve to meet the target intake pressure requirement; if the exhaust gas flow is too large, open the high-pressure stage exhaust bypass valve and the low-pressure stage exhaust bypass valve and control the opening.

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