CN109910641B

CN109910641B - Efficient composite energy storage system for pure electric vehicle and control method of efficient composite energy storage system

Info

Publication number: CN109910641B
Application number: CN201910143388.3A
Authority: CN
Inventors: 李健; 李勇; 马一鸣; 张鸿淇; 肖天正; 王浩琢
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2019-02-26
Filing date: 2019-02-26
Publication date: 2020-11-13
Anticipated expiration: 2039-02-26
Also published as: CN109910641A

Abstract

The invention discloses a high-efficiency composite energy storage system for a pure electric vehicle, which comprises a super capacitor bank (1), a bidirectional DC/DC converter (2), a storage battery pack (3), a power diode (4), a power switch tube (5) and a composite energy storage system controller (6). The invention also discloses a control method of the composite energy storage system. According to the invention, the super capacitor bank is directly connected to the side of the direct current bus in parallel, the energy storage potential of the super capacitor is exerted to the maximum extent, the storage battery pack is prevented from being damaged by the transient high-frequency component of the power supply load, meanwhile, the bidirectional DC/DC converter only needs to bear the steady low-frequency component of the power supply load provided by the storage battery, the cost and the volume are both greatly reduced, and the efficiency is improved. The control method divides the operation of the pure electric vehicle into six control modes, adopts different control strategies under different modes, comprehensively conforms to the driving requirements of the pure electric vehicle, and particularly has remarkable advantages for driving special vehicles working under severe road conditions such as the field and the like.

Description

Efficient composite energy storage system for pure electric vehicle and control method of efficient composite energy storage system

Technical Field

The invention belongs to the technical field of energy storage systems of new energy automobiles, and particularly relates to an efficient composite energy storage system for a pure electric automobile and a control method of the efficient composite energy storage system.

Background

The energy storage system is used as the only source of energy of the pure electric vehicle, and the working reliability, the economical efficiency and the environmental protection property of the energy storage system are always concerned. At present, most of pure electric vehicles use a storage battery pack as a power source of a motor. The storage battery has the advantages of high energy density, cyclic storage and release of more energy, and is suitable for being used as a main energy source of the pure electric vehicle. But the greatest disadvantage is that the power density is not high. The starting, obstacle crossing, climbing and acceleration of the pure electric vehicle, particularly the special vehicle which works in the field under the bad road condition for a long time, need the storage battery to bear the transient high-frequency component of the electric load, thus causing irreversible damage to the storage battery, greatly shortening the service life of the storage battery and further reducing the use economy of the storage battery. The method is one of the key factors for restricting the development of the pure electric vehicle.

The super capacitor has the advantages of high power density, low cost and the like, and the characteristic of high power density is complementary with the storage battery. Therefore, the super capacitor-storage battery composite energy storage system is provided for the self-attention. The conventional super capacitor-storage battery composite energy storage system has three basic configurations, namely a passive configuration, a semi-active configuration and an active configuration. The passive configuration directly connects the storage battery and the super capacitor in parallel on the side of the direct current bus, and cannot provide good power management; the active super capacitor and the storage battery are respectively connected to the side of the direct current bus in parallel through the DC/DC converter, the structure is complex, the cost is high, the efficiency is low, and the size is large, so that the active super capacitor and the storage battery are not suitable for being installed on a small special vehicle; the conventional semi-active configuration, which decouples the super capacitor and the battery through a DC/DC converter, is connected to the DC bus side.

Conventional semi-active configurations can be divided into two categories: the storage battery is directly connected in parallel to a direct current side bus, the terminal voltage of the super capacitor can fluctuate in a large range by the method, but instantaneous large current during starting and obstacle crossing needs to flow through the DC/DC converter, so that the size is larger, the cost is higher, and the efficiency is reduced; the super capacitor is directly connected in parallel to the direct current bus, and the structure has the advantages that the DC/DC converter does not need to bear instantaneous large current during starting and obstacle crossing, so the size can be smaller, the cost can be lower, the efficiency can be improved, the voltage controllability of the direct current side bus is poor, the storage battery needs to output transient high-frequency charging current to the super capacitor through the DC/DC converter in the recovery process of the direct current side bus voltage, the efficiency of the converter is reduced, and the storage battery is also seriously damaged.

Patent document CN106347144A discloses an energy optimization allocation method for a composite energy storage system of an electric vehicle. The system comprises a storage battery, a super capacitor and a DC/DC converter, wherein the super capacitor is connected with the DC/DC converter in series and then connected with the storage battery in parallel. According to the invention, a convex optimization method is adopted to generate an optimized comparison table of total output power and output power of the super capacitor bank, the required total torque is calculated according to the comparison table in combination with actual operation parameters of the electric vehicle, then the actual required power of the electric vehicle is calculated, and finally the bidirectional DC/DC converter is controlled according to the comparison table of the actual power and the output power of the super capacitor bank, so that the energy distribution of the electric vehicle is completed. However, patent document CN106347144A discloses an energy optimal allocation method for a composite energy storage system of an electric vehicle, which has the following disadvantages:

(1) the system configuration determines that the storage battery is directly connected in parallel on the direct current bus side, and the response speed of the DC/DC converter must be fast enough to ensure that the battery is prevented from being impacted by large driving current during starting and obstacle crossing, so that the complexity and the cost of control are increased undoubtedly.

(2) Although the optimization method solves the problem of low efficiency of the energy storage system configuration to a certain extent, the super capacitor still needs to provide the instantaneous driving current for starting and obstacle crossing through the DC/DC converter, so the defects of large volume and high cost of the DC/DC converter are not solved

In order to overcome the defects of the conventional semi-active configuration, patent document CN102611203B discloses a high-efficiency composite energy storage system for a vehicle, which includes a super capacitor and super capacitor management system, a power battery and power battery management system, a unidirectional DC/DC converter, a power diode, a function dissipation device, a power switch and an energy storage system controller. The invention is characterized in that: the unidirectional DC/DC converter is connected with a power diode in parallel, the anode of the power diode is connected with the input end of the unidirectional DC/DC converter, and the cathode of the power diode is connected with the output end of the unidirectional DC/DC converter; the anode of the power diode is also connected with the anode of the power battery, and the cathode of the power diode is also connected with the anode of the super capacitor. However, patent document CN102611203B discloses an efficient composite energy storage system for vehicles, which has the following disadvantages:

(1) according to the invention, the problem that the voltage of a direct-current side bus fluctuates greatly without control is solved by connecting the power diodes in parallel on two sides of the DC/DC converter, but the energy storage utilization rate of the super capacitor is reduced, and meanwhile, the overload capacity of the motor is insufficient.

(2) In the invention, when the voltage of the super capacitor is reduced to the voltage of the storage battery, the storage battery is required to continuously supply power to the transient high-frequency component of the power load through the power diode, and the damage to the storage battery is large.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides the high-efficiency composite energy storage system for the pure electric vehicle and the control method thereof, the super capacitor bank is directly connected to the side of the direct-current bus in parallel, the energy storage potential of the super capacitor is exerted to the maximum extent, the storage battery bank is prevented from being damaged by the transient high-frequency component of the power supply load, meanwhile, the bidirectional DC/DC converter only needs to bear the steady low-frequency component of the power supply load provided by the storage battery, the cost and the volume can be greatly reduced, and the efficiency can be improved.

In order to achieve the above object, according to one aspect of the present invention, there is provided an efficient composite energy storage system for a pure electric vehicle, including a super capacitor bank (1), a bidirectional DC/DC converter (2), a storage battery bank (3), a power diode (4), a power switch tube (5), and a composite energy storage system controller (6); wherein the content of the first and second substances,

the power diode (4) and the power switch tube (5) are connected in series and then connected in parallel to two sides of the bidirectional DC/DC converter (2), the drain electrode of the power switch tube (5) is connected with the anode of the storage battery pack (3), the source electrode of the power switch tube (5) is connected with the anode of the power diode (4), the cathode of the power diode (4) is connected with the anode of the super capacitor pack (1), and the super capacitor pack (1) and the storage battery pack (3) are not arranged in common;

the bidirectional DC/DC converter (2) adopts an isolated buck-boost topology, and the power switch tube (5) and the bidirectional DC/DC converter (2) are cooperatively controlled by the composite energy storage system controller (6).

Further, the device also comprises a current measuring device (7) and a voltage measuring device (12); wherein the content of the first and second substances,

one end of the current measuring device (7) and one end of the voltage measuring device (12) are respectively arranged on the direct current side bus (8), and the other end of the current measuring device is respectively connected with the composite energy storage system controller (6) and used for monitoring current and voltage signals of the direct current side bus (8) in real time and transmitting the current and voltage signals to the composite energy storage system controller (6).

According to another aspect of the invention, a control method for a high-efficiency composite energy storage system of a pure electric vehicle is provided, and the control method is divided into six control modes, namely a low-speed mode, a high-speed mode, an obstacle crossing mode I, an obstacle crossing mode II, a regenerative braking mode and a starting mode according to the current measured by the current measuring device (7); wherein the content of the first and second substances,

the low-speed mode is a control mode that the vehicle stably runs in a low-speed area;

the high-speed mode is a control mode that the vehicle runs stably in a high-speed area;

the obstacle crossing mode I is a control mode when the vehicle runs normally and meets short obstacles;

the obstacle crossing mode II is a control mode when the vehicle encounters a continuous obstacle with a higher height relative to the short obstacle or the wheel falls into a deep recess;

the feedback braking mode is a control mode that the motor feeds back electric energy to the composite energy storage system when the vehicle decelerates;

the starting mode is a control mode for normally starting the vehicle.

Further, the control method of the low speed mode includes the steps of:

s31, when the vehicle runs at low speed, the power supply load is mainly the steady low-frequency component, the impact of the current on the storage battery pack (3) is not large, and the storage battery pack (3) is used for supplying power to the load through the bidirectional DC/DC converter (2);

and S32, the bidirectional DC/DC converter (2) works in a boosting mode, and the control strategy is constant voltage control so as to maintain the voltage of the direct current side bus (8) and ensure that the super capacitor bank (1) has enough energy.

Further, the control method of the high speed mode includes the steps of:

s41, when the vehicle runs at a high speed, the power required by the power supply load is larger than that in a low-speed mode, and the stable low-frequency component is still taken as the main component, the composite energy storage system controller (6) controls the bidirectional DC/DC converter (2) to work in a constant-voltage mode, and the super capacitor bank (1) starts to supply power to the load;

and S42, the bidirectional DC/DC converter (2) participates in the control of the voltage of the direct-current side bus (8).

Further, the control method of the obstacle crossing mode I comprises the following steps:

s51, the composite energy storage system controller (6) controls the bidirectional DC/DC converter (2) to be closed, and the super capacitor bank (1) bears transient high-frequency current independently;

and S52, when the obstacle is crossed and the voltage of the direct current side bus (8) is reduced to be lower than the voltage of the storage battery pack (3), the storage battery pack participates in power supply through the power switch tube (5) and the power diode (4) branch.

Further, the control method of the obstacle crossing mode II includes the steps of:

s61, the super capacitor group (1) continues to supply power to the load independently so as to fully utilize the energy storage of the super capacitor and improve the overload capacity of the motor;

and S62, after the vehicle is out of the trouble, the voltage of the direct current side bus (8) rises, the bidirectional DC/DC converter (2) is controlled to work in a voltage reduction mode, and the storage battery pack provides steady-state low-frequency current for the power supply load through the bidirectional DC/DC converter (2) by adopting a constant current control strategy.

Further, the method for controlling the regenerative braking mode comprises the following steps:

s71, under the condition that the super capacitor bank (1) is not fully charged, the motor (10) works in a feedback braking mode to generate braking feedback energy to quickly charge the super capacitor bank (1) so as to enable the voltage of the direct current side bus (8) to rise;

and S72, when the vehicle is in the middle and later braking period or deep braking, the voltage of the direct current side bus (8) is increased to the rated voltage value of the super capacitor bank (1), and at the moment, the composite energy storage system controller controls the bidirectional DC/DC converter (2) to work in a charging mode to charge the storage battery bank (3).

Further, the control method of the start mode includes the following steps:

s81, the composite energy storage system controller (6) turns on the power switch tube (5), and simultaneously controls the bidirectional DC/DC converter (2) to be turned off, and the super capacitor bank (1) enables the voltage of the direct current side bus (8) to independently bear the transient high-frequency component of the starting load in the process of reducing the voltage to the voltage of the storage battery bank (3);

and S82, the storage battery pack (3) provides a steady-state low-frequency component for the load through the branch of the power switch tube (5) and the power diode (4).

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

1. according to the efficient composite energy storage system, the super capacitor bank is directly connected to the side of the direct current bus in parallel, the energy storage potential of the super capacitor is exerted to the maximum extent, the storage battery pack is prevented from being damaged by the transient high-frequency component of the power supply load, meanwhile, the bidirectional DC/DC converter only needs to bear the steady low-frequency component of the power supply load provided by the storage battery, the cost and the volume can be greatly reduced, and the efficiency can be improved.

2. According to the efficient composite energy storage system, the power diode and the power switch tube are connected in series and then connected in parallel to two sides of the bidirectional DC/DC converter, so that the problem that a direct-current side bus fluctuates greatly uncontrollably is solved, and meanwhile, the power switch tube can be turned off under the control of a control strategy to enable the super capacitor to continue discharging, the voltage of the direct-current side bus is reduced, and the overload capacity of the motor in a low-rotating-speed mode is improved.

3. The efficient composite energy storage system uses the bidirectional isolation type buck-boost converter, so that the control of the system is more flexible, and meanwhile, the design requirement and the manufacturing cost of the bidirectional DC/DC converter are reduced by introducing the power switch tube and the power diode branch, and the control method of the composite energy storage system is also simplified.

4. The efficient composite energy storage system is widely applied to pure electric vehicles, in particular to energy storage systems of special vehicles working under severe road conditions in the field.

5. The control method of the high-efficiency composite energy storage system avoids the storage battery and the bidirectional DC/DC converter from directly bearing the transient high-frequency component of the power supply load in all working modes through a reasonable control strategy, prolongs the service life of the storage battery, and reduces the design requirement of the bidirectional DC/DC converter, thereby greatly improving the economy of the system.

6. According to the control method of the high-efficiency composite energy storage system, the working mode of the bidirectional DC/DC converter and the on and off of the power switch tube are reasonably controlled by the composite energy storage system controller, and the problems that the direct-current side bus voltage of the existing semi-active configuration composite energy storage system is uncontrollably and greatly fluctuated, the overload capacity of a motor is insufficient, and a storage battery pack is difficult to avoid bearing the transient high-frequency component of a power supply load are solved.

Drawings

FIG. 1 is a schematic structural diagram of a high-efficiency composite energy storage system according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of five exemplary operation modes of the control strategy according to the current division measured by the current measuring device 7 according to the embodiment of the present invention;

FIG. 3(a) is a schematic diagram illustrating the operation of the high efficiency hybrid energy storage system according to the embodiment of the present invention in the low speed mode;

FIG. 3(b) is a schematic diagram of the high-efficiency hybrid energy storage system according to the embodiment of the present invention operating in the high-speed mode

Fig. 3(c) is a schematic working diagram of the high-efficiency composite energy storage system according to the embodiment of the invention when the high-efficiency composite energy storage system works in the obstacle crossing mode 1.

Fig. 3(d) is a schematic working diagram of the high-efficiency composite energy storage system according to the embodiment of the invention when the high-efficiency composite energy storage system works in the obstacle crossing mode 2.

Fig. 3(e) and (f) are schematic diagrams illustrating two phases of the regenerative braking mode of the efficient hybrid energy storage system according to the embodiment of the invention.

In all the figures, the same reference numerals denote the same features, in particular: the system comprises a super capacitor bank 1, a bidirectional DC/DC converter 2, a storage battery 3, a power diode 4, a power switch 5, a composite energy storage system controller 6, a current measuring device 7, a direct current side bus 8, an inverter 9, a motor 10, a composite energy storage system 11 and a voltage measuring device 12.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Fig. 1 is a high-efficiency composite energy storage configuration according to an embodiment of the present invention, which includes a super capacitor bank 1, a bidirectional DC/DC converter 2, a storage battery 3, a power diode 4, a power switch tube 5, and a composite energy storage system controller 6. The power diode 4 and the power switch tube 5 are connected in series and then connected in parallel to two sides of the bidirectional DC/DC converter 2, the drain electrode of the power switch tube 5 is connected with the anode of the storage battery 3, the source electrode of the power switch tube 5 is connected with the anode of the power diode 4, and the cathode of the power diode 4 is connected with the anode of the super capacitor group 1; the bidirectional DC/DC converter 2 adopts an isolated buck-boost topology, such as a phase-shifted full-bridge topology, and the super capacitor bank 1 and the storage battery 3 are not grounded together; the power switch tube 5 and the bidirectional DC/DC converter 2 are controlled by the composite energy storage system controller 6 to work in a coordinated mode. According to the invention, the super capacitor bank is directly connected to the side of the direct current bus in parallel, the energy storage potential of the super capacitor is exerted to the maximum extent, the storage battery pack is prevented from being damaged by the transient high-frequency component of the power supply load, meanwhile, the bidirectional DC/DC converter 2 only needs to bear the steady low-frequency component of the power supply load provided by the storage battery, the cost and the volume can be greatly reduced, and the efficiency can be improved.

Further, as shown in fig. 1, the efficient composite energy storage system further includes a current measuring device 7 and a voltage measuring device 12, wherein one end of the current measuring device 7 and one end of the voltage measuring device 12 are respectively disposed on the dc-side bus 8, and the other end of the current measuring device 7 and the other end of the voltage measuring device 12 are respectively connected to the composite energy storage system controller 6, so as to monitor current and voltage signals of the dc-side bus 8 in real time and transmit the signals to the composite energy storage system controller 6, and after receiving the signals, the composite energy storage system controller 6 controls the power switch tube 5 and the power diode 4 to operate, thereby realizing control of the dc-side bus voltage. According to the invention, the power diode 4 and the power switch tube 5 are connected in series and then connected in parallel to two sides of the bidirectional DC/DC converter 2, so that the problem that a direct current side bus fluctuates uncontrollably and greatly is solved, and meanwhile, the power switch tube 5 can be closed under the control of a control strategy to enable the super capacitor 1 to continue discharging, the voltage of the direct current side bus 8 is reduced, and the overload capacity of the motor in a low rotating speed mode is improved. The invention can be widely applied to the energy storage system of the pure electric vehicle, in particular to the energy storage system of the special vehicle working under the severe road conditions in the field.

Fig. 2 is a schematic diagram of a control strategy for five exemplary operating modes divided according to the current measured by the current measuring device 7, and the normal starting mode of the vehicle will be discussed separately. The low-speed mode refers to a control mode that a vehicle runs stably in a low-speed area, the high-speed mode refers to a control mode that the vehicle runs stably in a high-speed area, the obstacle crossing mode 1 refers to a control mode that the vehicle runs normally when encountering a low obstacle, the obstacle crossing mode 2 refers to a control mode that the vehicle encounters a continuous obstacle with a height higher than that of the low obstacle or a wheel falls into a deep depression, and the feedback braking mode refers to a control mode that a motor feeds back electric energy to a composite energy storage system when the vehicle decelerates. The start mode refers to a control mode in which the vehicle starts on a normal road surface.

Fig. 3(a) is an operation schematic diagram of the composite energy storage system when operating in the low-speed mode. When the vehicle runs at a low speed, the power supply load is mainly provided with a steady-state low-frequency component, and the current is less than a in fig. 2, so that the impact of the current on the battery pack 3 is not great, and the battery pack 3 can be used for supplying power to the load through the bidirectional DC/DC converter 2. In this mode, the bidirectional DC/DC converter 2 operates in a boost mode, and the control strategy is constant voltage control to maintain the voltage of the DC-side bus 8 and ensure that the super capacitor bank 1 has sufficient energy.

Fig. 3(b) is an operation schematic diagram of the composite energy storage system when operating in the high-speed mode. When the vehicle runs at a high speed, the power required by the power supply load is larger than that in a low-speed mode, but the power is still mainly based on a steady-state low-frequency component, so that the bidirectional DC/DC converter 2 can be controlled by the composite energy storage system controller 6 to still work in a constant-voltage mode, but at the moment, the super capacitor group 1 starts to supply power to the load, and the load of the storage battery group is reduced. Meanwhile, since the motor rotates at a high speed and the back electromotive force is correspondingly increased, the voltage of the DC-side bus 8 cannot be reduced at this time, and the bidirectional DC/DC converter 2 is required to participate in the control of the voltage of the DC-side bus 8.

Fig. 3(c) is an operation schematic diagram of the composite energy storage system when operating in the obstacle crossing mode 1. When the vehicle encounters a low obstacle, the driving system is required to provide a large torque to cross the obstacle in a short time, so that the power supply load has a transient high-frequency component. In order to prevent the power supply load transient high-frequency current from causing irreversible damage to the storage battery pack 3 and simultaneously prevent the transient high-frequency current from causing overlarge impact on the bidirectional DC/DC converter 2, at the moment, if the current measured by the current measuring device is greater than the value b, the power switch tube 5 is rapidly switched on, the bidirectional DC/DC converter 2 is controlled to be switched off by the composite energy storage system controller 6, the super capacitor pack 1 singly bears the transient high-frequency current, when an obstacle is crossed and the voltage of the direct-current side bus 8 is reduced to be lower than the voltage of the storage battery pack 3, the storage battery pack participates in power supply through the power switch tube and the power diode branch, and in the whole process, the storage battery pack 3 and the bidirectional DC/DC converter 2 both avoid the. The service life of the storage battery pack is greatly prolonged, and the design index of the bidirectional DC/DC converter is reduced, so that the economy is greatly improved.

Fig. 3(d) is an operation schematic diagram of the composite energy storage system when operating in the obstacle crossing mode 2. When the vehicle encounters a high obstacle or the wheel falls into a deep recess and needs to get rid of the obstacle, the rotating speed of the motor is low and the required torque is large, so that the voltage of the direct-current side bus 8 can be allowed to be reduced. After the vehicle passes through the obstacle crossing mode 1, the vehicle is not trapped, the driving current needs to be further increased, at the moment, the composite energy storage system controller 6 turns off the power switch tube according to the fact that the current value measured by the current measuring device is larger than the c value, the super capacitor group 1 continues to supply power to the load independently, the energy storage of the super capacitor is fully utilized, and the overload capacity of the motor is improved. After the vehicle is out of the trouble, the voltage of the direct current side bus 8 is required to rise, the bidirectional DC/DC is controlled to work in a voltage reduction mode, a constant current control strategy is adopted, the storage battery pack supplies stable low-frequency current to a power supply load through the bidirectional DC/DC converter 2, and the energy supply of the vehicle after the vehicle is out of the trouble is guaranteed. In this mode, the voltage of the dc-side bus 8 is lowered a lot in order to fully utilize the stored energy of the supercapacitor group 1, but the bus voltage is also allowed to be lowered in consideration of the low motor speed. In the whole process, the storage battery 3 and the bidirectional DC/DC converter 2 both avoid transient high-frequency current, so that the service life of the storage battery is greatly prolonged, the design index of the bidirectional DC/DC converter is reduced, and the economy is greatly improved.

Fig. 3(e) and 3(f) show two stages of the regenerative braking mode, respectively. When the vehicle is in the initial braking stage or the light braking stage, and the super capacitor bank 1 is not fully charged, the motor 10 works in a feedback braking mode to generate braking feedback energy to rapidly charge the super capacitor bank 1, so that the voltage of the direct-current side bus 8 is increased; when the vehicle is in the middle and later braking period or in deep braking, the voltage of the direct-current side bus 8 is already increased to the rated voltage value of the super capacitor bank 1, and at the moment, the composite energy storage system controller controls the bidirectional DC/DC converter 2 to work in a charging mode to charge the storage battery bank 1.

The operation diagram of the normal starting mode of the vehicle is the same as that of the obstacle crossing mode 1 shown in fig. 3 (c). When the vehicle starts, the driving system needs to provide larger torque in a short time so as to facilitate the vehicle to start, and the control strategy at the moment is as follows: the composite energy storage system controller 6 is used for switching on the power switch tube 5 and simultaneously controlling the bidirectional DC/DC converter 2 to be switched off, the super capacitor group 1 enables the voltage of the direct-current side bus 8 to independently bear the transient high-frequency component of a starting load in the process of reducing to the voltage of the storage battery group 3, and the storage battery group 3 provides a steady low-frequency component for the load through the power switch tube 5 and the power diode 4.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A high-efficiency composite energy storage system for a pure electric vehicle is characterized by comprising a super capacitor bank (1), a bidirectional DC/DC converter (2), a storage battery pack (3), a power diode (4), a power switch tube (5) and a composite energy storage system controller (6); wherein the content of the first and second substances,

2. The efficient composite energy storage system for the pure electric vehicle as recited in claim 1, further comprising a current measuring device (7) and a voltage measuring device (12); wherein the content of the first and second substances,

3. The control method of the efficient composite energy storage system for the pure electric vehicle as claimed in claim 2, characterized in that the control method is divided into six control modes, namely a low-speed mode, a high-speed mode, an obstacle crossing mode I, an obstacle crossing mode II, a regenerative braking mode and a starting mode, according to the current measured by the current measuring device (7); wherein the content of the first and second substances,

the starting mode is a control mode for normally starting the vehicle.

4. The control method for the efficient hybrid energy storage system of the pure electric vehicle according to claim 3, characterized in that the control method for the low-speed mode comprises the following steps:

5. The control method for the efficient composite energy storage system of the pure electric vehicle as claimed in claim 3, wherein the control method for the high-speed mode comprises the following steps:

6. The control method for the efficient composite energy storage system of the pure electric vehicle as claimed in claim 3, wherein the control method for the obstacle crossing mode I comprises the following steps:

7. The control method for the efficient composite energy storage system of the pure electric vehicle as claimed in claim 3, wherein the control method for the obstacle crossing mode II comprises the following steps:

8. The control method of the efficient composite energy storage system for the pure electric vehicle as claimed in claim 3, wherein the control method of the regenerative braking mode comprises the following steps:

9. The control method for the efficient hybrid energy storage system of the pure electric vehicle as claimed in claim 3, wherein the control method for the starting mode comprises the following steps: