CN103241126A - Electric car brake energy recovery system - Google Patents

Abstract

The present invention proposes a braking energy recovery system for electric vehicles, including: a power conversion energy storage device (10), a brake recovery controller, a storage battery (VS) and a motor driver. The power conversion energy storage device (10) is controlled by the main Relay (K), control relay (K1), DC/DC converter and supercapacitor (SC), the DC/DC converter is connected to the supercapacitor (SC) through the output terminal of the control relay (K1); The input terminals of the main relay (K) and the control relay (K1) are respectively connected to the brake recovery controller; the main relay (K) is used to control the connection of the battery or the supercapacitor (SC) to the motor driver circuit ( 20). The invention can effectively improve the energy utilization rate of the vehicle, alleviate the low mileage of the electric vehicle caused by insufficient battery power, not only achieve the purpose of energy saving and environmental protection, but also improve the convenience of the electric vehicle user.

Description

An electric vehicle braking energy recovery system

technical field

The present invention belongs to the technical field of electric vehicles, and more specifically relates to a braking energy recovery device for electric vehicles, which can effectively recover part of the energy dissipated during frictional braking. the

Background technique

With the rapid development of the global automobile industry and the rapid growth of car ownership, the problems of energy crisis and environmental pollution are becoming more and more serious. With the official release of the "National "Twelfth Five-Year" Science and Technology Development Plan", the new energy vehicle industry technology will become a key area supported by the Ministry of Science and Technology in the next five years, so pure electric vehicles will receive more and more attention. the

 As the government and society pay more and more attention to environmental pollution and energy issues, energy conservation and environmental protection have become one of the main goals of the development of the automotive industry. The development of electric vehicle technology has entered an important stage, in which regenerative braking technology is one of the key technologies for energy saving and environmental protection, and there are many problems to be solved. During the braking process of the car, a large amount of kinetic energy is converted into heat energy and dissipated through friction, which leads to premature wear of the car brake system and increases the cost of using the car. Energy recovery using regenerative braking is one of the energy-saving advantages of electric vehicles. The regenerative braking system recycles and reuses part of the energy originally dissipated by friction braking, which can effectively improve the energy utilization rate of the vehicle and play a role in saving energy. With the further development of automobile drive motor technology and energy storage technology, the use of motors to recover and utilize braking energy is increasingly showing its advantages, especially in pure electric or hybrid vehicles, mainly using regenerative braking methods of electric energy storage . the

Contents of the invention

The invention provides an automobile braking energy recovery system to facilitate the recovery and reuse of part of the kinetic energy of the electric automobile during braking and improve the continuation mileage. the

The present invention uses a power conversion energy storage device composed of a buck-boost type DC-DC converter and a supercapacitor. The power conversion energy storage device can realize braking energy during the braking process of an electric vehicle under the control of a controller instruction. The recovery and reuse of stored energy during drive. Its specific working principle is to use a self-designed DC/DC converter in conjunction with a super capacitor. During the forward boost process, since the relay K1 is switched at terminal 1, the DC/DC converter becomes a boost converter. , through the control of the brake recovery controller during the braking process of the car, q1 is turned on, q2 is chopped, and the supercapacitor is boosted and charged in a forward direction; The DC converter becomes a buck converter at this time. During the normal running of the car, in order to match the output voltage of the supercapacitor terminal with the rated voltage of the motor, the brake recovery controller makes q2 conduct and q1 chops , reverse step-down according to the corresponding ratio; this system greatly simplifies the Bi-buck-boost type DC/DC part of the hardware circuit used in the traditional braking energy recovery system without affecting the effect, and cooperates with the corresponding control The strategy not only makes the recycling efficiency reach more than 30%, but also greatly improves the energy utilization efficiency. the

In order to achieve the above object, the present invention adopts the following technical solution: a braking energy recovery system for an electric vehicle, comprising: a power conversion energy storage device, a braking recovery controller, a storage battery and a motor driver, wherein the motor driver is composed of a field effect transistor The output terminal of the motor driver is connected to the three windings of the motor; the brake recovery controller is based on the output signal of the motor driver, the supercapacitor voltage signal, the bus current signal, the speed signal, the accelerator pedal signal and the brake pedal signal to control the power conversion energy storage device to absorb or release energy, the power conversion energy storage device is composed of a main relay, a control relay, a DC/DC converter and a supercapacitor, and the DC/DC converter outputs through the control relay terminal is connected with the supercapacitor; the input terminals of the main relay and the control relay are respectively connected with the brake recovery controller; the main relay is used to control the connection of the storage battery or the supercapacitor into the motor driver circuit;

The DC/DC converter is composed of a first field effect transistor, a second field effect transistor and an energy storage inductor, one end of the energy storage inductor is connected to the output end of the control relay, and the other end of the energy storage inductor is respectively connected to the first The source of the field effect transistor is connected to the drain of the second field effect transistor, the drain of the first field effect transistor is connected to the output terminal of the control relay, and the source of the second field effect transistor is connected to the supercapacitor one end of the supercapacitor; the other end of the supercapacitor is connected to the output contact of the control relay; the gates of the first field effect transistor and the second field effect transistor are respectively connected to the brake recovery controller;

The output end of the control relay includes first and second groups of contacts, the first group of contacts is provided with a first input contact and a first output contact, and the second group of contacts is provided with a second input contact point and the second output contact.

During the braking process of the vehicle, the brake recovery controller controls one end of the energy storage inductance to be connected to the first input contact of the control relay, and the drain of the first field effect transistor is connected to the first output contact of the control relay Connecting, controlling the conduction of the first FET, and chopper boosting of the second FET, so that the DC/DC converter becomes a boost-type converter, and charges the supercapacitor with positive boost;

When the electric vehicle is in the state of starting, accelerating, etc., the brake recovery controller controls the drain of the first field effect transistor to be connected to the second input contact of the control relay, and one end of the energy storage inductor is connected to the second input contact of the control relay. The two output contacts are connected to control the conduction of the second field effect transistor, and the first field effect transistor is chopper-boosted, so that the DC/DC converter becomes a buck type converter, and the supercapacitor reverses the step-down discharge .

As a further improvement of the present invention, when the supercapacitor is working in the boost charging state, the brake recovery controller monitors the supercapacitor voltage and the motor speed, and before the motor generated voltage is equal to the supercapacitor voltage, the motor generated voltage is boosted. voltage, and adjust the duty cycle of the PWM wave as the gating signal of the second field effect tube according to the speed, control the second field effect tube to chop and boost the voltage, and continue to charge the supercapacitor. the

As a further improvement of the present invention, when the supercapacitor is working in the step-down discharge state, the brake recovery controller monitors the motor speed and the supercapacitor voltage, and the supercapacitor boosts the output to drive the motor. When the motor speed reaches a predetermined value, the The relay K is switched to the battery circuit, and the battery supplies power to the motor. the

The invention mainly controls the opening and closing of the main relay and the switching of two field effect transistors in the DC-DC to charge and discharge the supercapacitor to achieve the purpose of improving efficiency. The battery is used as the main power source, the supercapacitor is used as the energy recovery storage device, the DC-DC converter is used to adjust the terminal voltage when the supercapacitor is charged and discharged, the relay K1 controls the DC/DC to form a step-up and step-down circuit respectively, and the main relay K is to control Connect the battery or supercapacitor to the main circuit. The role of the brake recovery controller is to receive the supercapacitor voltage signal, bus current signal, speed signal, accelerator pedal signal and brake pedal signal and make corresponding processing and control. the

This system can realize the following functions: When the electric vehicle is in the state of braking and deceleration, the system can keep the super capacitor in the charging state, and use the response control strategy to control the vehicle to achieve different effects under different driving conditions, such as maximizing energy recovery, The braking performance is optimal; when the electric vehicle is in the state of starting, accelerating, etc., the super capacitor works in the boost discharge state, and the boost output of the super capacitor drives the motor in advance. When the motor speed reaches a predetermined value, the battery supplies power to the motor. In this way, the damage to the battery due to high current discharge in working conditions such as motor starting and climbing is avoided, and the cruising range of the electric vehicle is extended. the

Description of drawings

Figure 1 is a topological structure diagram of the main circuit according to Embodiment 1 of the present invention;

Figure 2 is a description of the input/output signals of the brake recovery controller in Embodiment 1 of the present invention;

Fig. 3 is a circuit diagram switching to the first group of contacts with the control relay K1 of Embodiment 1 of the present invention;

Fig. 4 is a circuit diagram of switching to the second group of contacts with the control relay K1 of Embodiment 1 of the present invention;

Fig. 5 is a system diagram of Embodiment 1 of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments. the

Example 1

As shown in Figure 1, a brake energy recovery system for electric vehicles includes: a power conversion energy storage device 10, a brake recovery controller, a storage battery VS and a motor driver, wherein the motor driver 20 is composed of field effect transistors Q1, Q2, Q3 , Q4, Q5, Q6, the output terminal of the motor driver is connected to the three windings A, B, C of the motor; the brake recovery controller is based on the output signal of the motor driver, the supercapacitor voltage signal, the bus current signal, the speed signal, accelerator pedal signal and brake pedal signal to control the power conversion energy storage device 10 to absorb or release energy. The power conversion energy storage device 10 is composed of a main relay K, a control relay K1, a DC/DC converter and a supercapacitor SC, and the DC/DC converter is connected to the supercapacitor SC through the output terminal of the control relay K1. The input ends of the main relay K and the control relay K1 are respectively connected to the brake recovery controller; the main relay K is used to control the connection of the storage battery or the supercapacitor SC into the motor driver circuit 20 . The DC/DC converter is composed of a first field effect transistor q1, a second field effect transistor q2 and an energy storage inductor L. One end of the energy storage inductor L is connected to the output end of the control relay K1, and the other end of the energy storage inductor L is respectively It is connected to the source of the first field effect transistor q1 and the drain of the second field effect transistor q2), the drain of the first field effect transistor q1 is connected to the output terminal of the control relay K1, and the source of the second field effect transistor q2 is connected to One end of the supercapacitor SC. The other end of the supercapacitor SC is connected to the first and second output contacts 12, 22 of the control relay K1. The gates of the first field effect transistor q1 and the second field effect transistor q2 are respectively connected to the brake recovery controller;

The output end of the control relay K1 includes first and second sets of contacts, the first set of contacts is provided with a first input contact 11 and a first output contact 12, and the second set of contacts is provided with a second input contact contact 21 and a second output contact 22.

During the braking process of the vehicle, the brake recovery controller 20 controls one end of the energy storage inductance L to be connected to the first input contact 11 of the control relay, and the drain of the first field effect transistor q1 is connected to the first output contact 12 of the control relay , control the first field effect transistor q1 to be turned on, and the second field effect transistor q2 is chopper-boosted, so that the DC/DC converter becomes a boost type converter, and charges the supercapacitor SC with positive boost. the

As shown in Figure 3, when the electric vehicle is in the braking deceleration state, the brake recovery controller controls one end of the energy storage inductance L to be connected to the first input contact 11 of the control relay, and the drain of the first field effect transistor q1 is connected to the control relay The first output contact 12 of the relay is connected to control the first field effect transistor q1 to be completely turned on, and the second field effect transistor q2 is choppered to boost the voltage, so that the DC/DC converter becomes a boost type converter and supplies power to the supercapacitor SC Positive boost charge. At this time, the supercapacitor is working in a charging state. At this time, the voltage generated by the motor gradually weakens as the speed decreases, while the voltage of the super capacitor gradually increases. Since the voltage generated by the motor is proportional to the speed, the voltage of the super capacitor and the speed of the motor are monitored at the same time. Before the voltage generated by the motor is equal to the voltage of the super capacitor , that is to feed back the supercapacitor voltage and the motor speed, through the control algorithm to make q2 chopper boost, boost the voltage generated by the motor, continue to charge the supercapacitor, and adjust the duty cycle of the boosted PWM wave according to the speed, with the maximum efficiency Recover braking energy. the

As shown in Figure 4, when the electric vehicle is in the state of starting, accelerating, etc., the brake recovery controller controls the drain of the first field effect transistor q1 to be connected to the second input contact 21 of the control relay, and the energy storage inductance L One end is connected to the second output contact (22) of the control relay to control the second field effect transistor q2 to be completely turned on, and the first field effect transistor q1 is choppered and boosted, so that the DC/DC converter becomes a buck type converter, the supercapacitor SC reverse step-down discharge. At this time, the supercapacitor works in the step-down discharge state, and monitors the motor speed and supercapacitor voltage at the same time. The boost output of the supercapacitor drives the motor in advance. When the motor speed reaches the predetermined value, then The relay K is switched to the battery circuit, and the battery supplies power to the motor. In this way, the damage to the battery due to high current discharge in working conditions such as motor starting and climbing is avoided, and the driving range of the electric vehicle is extended. the

As shown in Figure 2, the input/output signal description diagram of the brake recovery controller of the electric vehicle braking energy recovery system, the brake recovery controller adopts Atmega16 single-chip microcomputer, and the brake recovery controller collects the signals of the motor, pedal acceleration and braking signals , and signals such as current and voltage are converted into analog signals to coordinate the state of the control system according to the internal program. Combine the collected three-phase Hall signals with two phases, and then add them together, then when the motor rotates at a constant speed through the 360° electrical angle period, you will get three symmetrical and square wave signals with the same cycle and 120° electrical angle, that is, with The high and low level durations (T) of the square wave signal are equal. When the rotational speed changes, the period of the square wave also changes accordingly. Using it to measure the rotational speed of the motor has higher measurement accuracy and resolution than when a single Hall signal is used. Every time the motor rotates through 360 ゜ mechanical angle, 3*p square waves will be generated, where p is the number of pole pairs of the motor. In addition, the bus current signal at both ends of the battery driving the motor and the voltage at the supercapacitor terminal are collected, and the acceleration and braking signals of the motor are collected. Through a simple integral circuit, PWM can obtain an analog voltage signal that is linearly related to the signal duty cycle, and use PWM to simulate the handle signal and braking signal. At this time, the host computer sends instructions to the braking energy recovery controller. The brake recovery controller outputs PWM with a given frequency f and duty cycle D to simulate the handlebar or brake signal. At this time, the voltage of the analog signal is D*5V. Therefore, it is necessary for the brake recovery controller to output two PWMs to simulate the handlebar signal and the brake signal respectively, and use the PWM as the gating signal to control the field effect transistor switch, control the DC/DC converter buck-boost, and the relay in the system. Switching between the automatic recovery control loop and the battery loop. the

The schematic diagram of the electric vehicle braking energy recovery system is shown in Figure 5. The solid line in the figure is the power line, and the dotted line is the signal line. The motor driver drives and controls the motor, receives Hall signals, accelerator pedal and brake pedal electric signals, and real-time Passed to the brake recovery controller, the brake recovery controller judges the driving conditions of the vehicle through these signals, and makes a judgment to control the opening and closing of the main relay K and the control relay K1, so as to realize energy recovery and release. the

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some predictable improvements and modifications can also be made, these improvements And retouching should also be regarded as the protection scope of the present invention. the

the

Claims (4)

1. An electric vehicle braking energy recovery system, comprising: a power conversion energy storage device (10), a braking recovery controller, a storage battery (VS) and a motor driver, wherein the motor driver (20) is composed of a field effect tube ( Q1, Q2, Q3, Q4, Q5, Q6), the output terminal of the motor driver is connected with the three windings (A, B, C) of the motor; the brake recovery controller is based on the output signal of the motor driver, The supercapacitor voltage signal, the bus current signal, the speed signal, the accelerator pedal signal and the brake pedal signal control the power conversion energy storage device to absorb or release energy, which is characterized in that: The power conversion energy storage device (10) is composed of a main relay (K), a control relay (K1), a DC/DC converter and a supercapacitor (SC), and the DC/DC converter outputs through the control relay (K1) The terminal is connected to the supercapacitor (SC); the input terminals of the main relay (K) and the control relay (K1) are respectively connected to the brake recovery controller; the main relay (K) is used to control the battery Or the supercapacitor (SC) is connected to the motor driver circuit (20); The DC/DC converter is composed of a first field effect transistor (q1), a second field effect transistor (q2) and an energy storage inductor (L), and one end of the energy storage inductor (L) is connected to a control relay (K1) The output terminal of the energy storage inductance (L) is respectively connected to the source of the first field effect transistor (q1) and the drain of the second field effect transistor (q2), and the first field effect transistor ( The drain of q1) is connected to the output terminal of the control relay (K1), the source of the second field effect transistor (q2) is connected to one end of the supercapacitor (SC); the other end of the supercapacitor (SC) and The output contacts (12, 22) of the control relay (K1) are connected; the gates of the first field effect transistor (q1) and the second field effect transistor (q2) are respectively connected with the brake recovery controller ; The output end of the control relay (K1) includes first and second sets of contacts, the first set of contacts is provided with a first input contact (11) and a first output contact (12), and the second set of contacts The contacts are provided with a second input contact (21) and a second output contact (22). 2. The electric vehicle braking energy recovery system according to claim 1, characterized in that, When the car brakes or decelerates, the brake recovery controller controls one end of the energy storage inductance (L) to be connected to the first input contact (11) of the control relay, and the first FET (q1) The drain is connected to the first output contact (12) of the control relay to control the conduction of the first field effect transistor (q1), and the second field effect transistor (q2) is chopper-boosted, so that the DC/DC converter becomes A boost-type converter, charging the supercapacitor (SC) with a positive boost; When the electric vehicle is in the state of starting, accelerating, etc., the brake recovery controller controls the drain of the first field effect transistor (q1) to be connected to the second input contact (21) of the control relay, and the energy storage inductor One end of (L) is connected to the second output contact (22) of the control relay to control the conduction of the second field effect transistor (q2), and the first field effect transistor (q1) is chopper-boosted so that the DC/ The DC converter becomes a buck converter, and the supercapacitor (SC) reverses the step-down discharge. 3. The electric vehicle braking energy recovery system according to claim 1 or 2, characterized in that, when the supercapacitor is working in a boost charging state, the brake recovery controller monitors the supercapacitor voltage and the motor speed, Before the voltage generated by the motor is equal to the voltage of the supercapacitor, the voltage generated by the motor is boosted, and the duty cycle of the PWM wave as the gating signal of the second FET (q2) is adjusted according to the speed to control the second FET (q2) q2) Chopping and boosting, continue to charge the supercapacitor; When the supercapacitor works in the step-down discharge state, the brake recovery controller monitors the motor speed and the supercapacitor voltage, and the supercapacitor boosts the output to drive the motor. When the motor speed reaches a predetermined value, the relay K is switched to the battery circuit. The motor is powered by the battery. 4. The electric vehicle braking energy recovery system according to claim 1, wherein the braking recovery controller adopts an Atmega16 single-chip microcomputer.

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