CN1807144A - Fuel cell car energy control method based on CAN bus network communication - Google Patents

Abstract

The invention relates the fuel battery coach controlling method on base of the CAN bus internet communication used for hybrid power system, using the direct converting means to carry out energy management control. The CAN bus sends the main voltage signal VDC/DC, motor rotation rate signal rmotor and throttle pedal signal Acc_ps to full control device; in full control device looking up goal torque Tmotor and calculate demand total power Pmotor, auxiliary device power PAUX and accumulator charge-discharge power Pbat; calculate DC/DC output current IDC/DC; IDC/DC passes first order filtration, after meeting the DC/DC converter dynamic regulator course, then the full control device sends it to DC/DC control device by CAN bus, and realize the DC/DC current control. The invention can realize the accurately control of load power, and provide the flat form for any kind of energy controlling method; the charge and discharge state provided by secondary energy can be controlled; the integral efficiency of power system is improved.

Description

A kind of fuel cell car energy control method based on the CAN bus network communication

Technical field

A kind of fuel cell car energy control method based on the CAN bus network communication is applicable to the control method that hybrid power system utilizes dc converter to carry out real-time energy management, belongs to car load energy management method technical field.

Technical background

Being accompanied by in short supply and cry environmental protection of world energy sources improves day by day; that people need is efficient, the energy of cleaning, economy, safety and sustainable development provides the driving energy as the substitute of petroleum products for automobile; allow hydrogen and oxygen generate water in the fuel battery inside environment by electrochemical reaction; and discharging electric energy, this is a kind of ideal capacity source of very clean and effective.

At present most widely used in the automobile is the PEM hydrogen cell, and common way is that the exchange membrane hydrogen cell directly is connected with motor by cable, offers the motor electric energy.Because motor is the power component that directly reflects the driver driving demand, power variation rate may require to alter a great deal according to driving, and this causes fuel cell to provide power to take place than great fluctuation process, thereby requires its dynamic property better.Characteristics of fuel cells is: when stable state, maximum power and efficient can be provided, and dynamically the time, each parts will be operated in the efficient lower region, be unfavorable for providing more high-power to motor, because the factor of fuel cell regulating characteristic mainly is the inertia and the ducted fluid dynamics factor of compressor and various control cocks in the ancillary system, therefore need parallel connection increase an auxiliary energy link---storage battery between fuel cell and motor, common so pure fuel cell power system is with regard to the very natural hybrid power system that converts to.

Storage battery is a kind of common auxiliary energy unit, be mainly used in automobile starting and automobile low voltage circuit etc., and hybrid power system can be selected very big storage battery of capacity such as 85Ah, the 336V lead-acid battery.The storage battery characteristics are to have good dynamic response characteristic energy, can improve the service performance of electrical motor when load is suddenlyd change, this helps the quick switching of the quick start and the maximum power state of fuel battery engines, in addition, storage battery and fuel cell and motor parallel, can in vehicle traveling process, realize battery charge and brake energy feedback easily, guarantee charge capacity SOC (State Of Charge) in the storage battery.

Motor, fuel cell and three energy units of storage battery, owing to be connected in parallel on the same bus, therefore, as long as two energy unit input and output power among having determined three, so whole power system energy Flow will be determined.The requirement of power of motor reflection driver driving can draw by demarcating MAP figure according to acceleration pedal and motor speed; Bus directly is connected on the storage battery two-port, and its voltage has directly reflected the internal storage battery voltage swing, thereby storage battery input and output power is determined by the charge and discharge electric current; Fuel battery inside electrochemical reaction complexity, but its outside steady state characteristic is clearer and more definite, can calibrate under specified temp, and the relative output relation with voltage of its electric current has been determined fuel cell output current, can determine its horsepower output.To sum up, a direct current power converting means (DC/DC changer) in parallel between fuel cell and motor be can consider, fuel cell side output voltage or size of current on the bus controlled by it.Generally in the fuel cell hybrid system, usefulness more be boost, step-down, buck or current DC changer because the loop of these changers is simple, so efficient is higher.

At home, the energy control algorithm that is used for fuel battery city carriage uses the DC/DC voltage control always, and its principle is as follows: during less than Pmax, the output of DC-DC changer is constant in all the time a certain predeterminated voltage U0 at the horsepower output of fuel battery engines; When DC-DC changer horsepower output reaches corresponding to fuel cell maximum power point, DC-DC changer output voltage and the electric current relation of being inversely proportional to, it is constant that horsepower output keeps; When power demand continuation increase, because the electric current I max of DC-DC changer restriction, horsepower output descends very fast.The control of this method is simple, and energy distributes between driving engine and storage battery automatically, and the mistake that the bus steady state value has limited storage battery is put.But the method also comprises very big defective therein: during dynamic response, only control the energy distribution that bus voltage can't each parts of accuracy control; Owing to lack to accumulator internal pressure; internal resistance and SOC accurately estimate in real time; only rely on amount of bus voltage can't accomplish accurately the charging and discharging of storage battery power, storage battery occurs overcharging and crosses through regular meeting in real-world operation puts phenomenon, and storage battery is impacted service life.Therefore new car load energy control method need solve the problem that energy clearly distributes between fuel cell, storage battery and the motor three, and the DC converter current control that this method proposes can well address this problem.

It is big to have a system data exchange capacity based on the communication of CAN bus, and real-time and high reliability features are suitable for that entire car controller carries out energy control to total system and to each parts co-operative control.Network system based on the CAN bus comprises entire car controller, fuel cell system, DC/DC changer, motor and nodes such as controller and battery management system thereof, they with entire car controller as message switching center, be responsible for the data exchange between each node, be to carry out data exchange between the main and entire car controller of each node, pass between other node and change data.Network service moves in the following manner: after the entire car controller initialization operation, send its two frame data to each parts every 50MS with broadcast mode, after each parts is received first frame data that entire car controller sends, postpone (2* (entire car controller address-specific features address)) ms after the time, at once send himself data to entire car controller, only sending once (in the 50MS after receiving the entire car controller data) in the one-period in the point-to-point communication mode.Like this, each node state of power system passes to entire car controller by the CAN bus network in 50MS, and car load is controlled it and sent the instruction of DC/DC converter current and other instructions after treatment, finishes control method of finished.

Summary of the invention

Fuel battery passenger car dynamic structure at above-mentioned technical background analysis draws the objective of the invention is to provide a kind of energy control method---current control method:

Power of motor P _Motor, DC converter DC/DC power P _DC/DCWith the storage battery power P _BatBetween supplydemand relationship as follows: P _Motor=P _DC/DC+ P _Bat

Power of motor P in the method _MotorCan determine by look-up method, as long as determine P _DC/DCValue so according to this relational expression, can be determined storage battery input and output power P _Bat, because this three is parallel on the bus, voltage equates that then power relation can be exchanged into the electric current supplydemand relationship simultaneously:

I _motor＝I _DC/DC+I _bat

Therefore the core of this method is to determine the outgoing current I of DC/DC _DC/DCExpected value can be determined whole dynamic system power assignment problem.

The present invention can allow entire car controller in the sampling interval (50MS) that limits, and according to each unit status signal that the CAN bus is transmitted, solves clear and definite energy control numerical value, and finally sends to the control of execution unit DC/DC changer realization energy.

Technical scheme is as follows:

A kind of fuel cell car energy control method based on the CAN bus network communication, its hardware mainly comprises motor, fuel cell and storage battery, and the DC/DC DC converter, and they are parallel on the bus, finish power supply and demand transformational relation, thereby satisfy the bus driving demand.It is characterized in that this method may further comprise the steps:

1. acquisition of signal: gather the storage battery port voltage as bus voltage signal V by the CAN bus _DC/DCGather motor speed signal r by the CAN bus _MotorGather accelerator pedal signal Acc_ps by the CAN bus and all send entire car controller to;

2. in entire car controller, look into the target torque T of power taking machine by torque M AP figure _Motor, equation expression is:

T _motor＝f(r _motor，Acc_ps)

Output T wherein _MotorBe the target torque of motor, input r _MotorBe the current rotating speed of motor, Acc_ps is an accelerator pedal position, represents with percentum, and f () expression is tabled look-up and used nonlinear function.

3. in entire car controller, calculate motor demand gross horsepower P _Motor:

P _motor＝(T _moror×r _motor)/(η _{motor_ctr}×η _motor)

Output P wherein _MotorBe motor demand gross horsepower, η _{Motor_ctr}Be electric machine controller efficient, η _MotorBe electrical efficiency.

4. in entire car controller, calculate other auxiliary device power demands P _AUX, can obtain the rating horsepower value:

P _mix＝P _motor+P _AUX

P wherein _MixExpression comprises the motor demand and comprises the gross horsepower of other auxiliary device power at the internal power consumable part.

5. in entire car controller, calculating accumulator discharges and recharges power:

P _bat＝P _max×(SOC _lim-SOC)

Output P wherein _BatBe accumulator cell charging and discharging power; P _MaxFor the storage battery maximum discharges and recharges power.

6. in entire car controller, calculate DC/DC horsepower output P _DC/DCFor:

P _DC/DC＝P _mix+P _bat＝(T _motor×r _motor)/(η _{motor_ctr}×η _motor)+P _cond+P _max×(SOC _lim-SOC)

7. in entire car controller, calculate DC/DC outgoing current I _DC/DCFor:

I _DC/DC＝P _DC/DC/V _DC/DC

8. this I _DC/DCThrough first-order filtering, satisfy DC/DC changer dynamic adjustments respective process after, send to the DC/DC controller by entire car controller by the CAN bus communication, realize the DC/DC current control.

Control principle of the present invention is as follows:

1. the power system bus voltage is determined by storage battery;

2. motor driver is a current source, i.e. the load of power system shows as current-mode;

3. control the horsepower output of fuel cell by the electric current of control DC/DC mouth;

4. the charging and discharging of accumulator electric current is the electric current and the motor driver electric current sum of DC/DC mouth, and its power control is clear and definite;

Therefore in the power system bus voltage and each branch current all be fully controlled.

This method is considered storage battery SOC state and power demand of motors, realizes the energy back adjusting: when storage battery SOC is higher than thresholding SOC _LimThe time, method adopts combined power to satisfy power demand of motors, promptly allows storage battery emit corresponding power in the SOC ratio, and surplus power is satisfied by fuel cell; When storage battery SOC is lower than thresholding SOC _LimThe time, method charges a battery in proportion according to SOC, considers power demand of motors simultaneously, and their power sums are the fuel cell output power output.

This method is particularly suitable for being realized by dc converter the hybrid architecture of control, promptly provides parts (as fuel cell, combustion engine etc.) and second energy that the parts hybrid architecture that (as storage battery, super capacitor, flywheel etc.) are formed is provided by expenditure of energy parts (as motor etc.), main energy.Its major advantage has:

1. realization accurate control of load power can be various energy control methods and realizes providing experiment porch;

2. optimize the operating mode that main energy provides parts, second energy that parts are provided, improve the whole efficiency of power system;

3. second energy provides parts charging and discharging state may command.

Description of drawings

Fig. 1 is the fuel cell power system structural representation;

Fig. 2 is the current control method diagram of circuit;

Fig. 3 is driver driving intention MAP figure.

The specific embodiment

Below in conjunction with accompanying drawing concrete enforcement of the present invention is described further:

Fig. 1 is the fuel cell power system structural representation, and bifilar heavy line is represented the energy Flow circuit among the figure, and the representative of sub-thread dotted line is based on the state and the control signal flow circuits of the transmission of CAN bus network.Fuel cell is by coming from hydrogen in the hydrogen cylinder as energy source.Electric machine controller is a kind of DC/AC changer, direct current energy can be converted to AC energy and come drive motor.Fuel cell system is in parallel with storage battery and electric machine controller by main DC/DC DC converter, like this, by controlling main DC/DC electric current output, fuel cell current output and power output both can have been controlled, can realize the automatic guidance of motor input and output electric current and storage battery input and output electric current again, with clearly defined objective.Parts such as fuel cell, main DC/DC, storage battery and electric machine controller all have the controller of oneself: they collect the status signal of function unit, send to entire car controller by the CAN bus network, accept the control signal that entire car controller is sent then, realize the control of parts separately.Entire car controller is in the core of distributed control network, it gathers the information of each parts, in conjunction with the intention of driver driving, generates control command after carrying out corresponding method, be published to each subassembly by the CAN network, thereby realize control each subassembly.

Fig. 2 is the current control method diagram of circuit, is at first gathered the status signal of each node of power system by the CAN bus, comprising bus voltage signal V _DC/DC, motor speed signal r _MotorWith accelerator pedal signal Acc_ps.

Because bus is connected on the storage battery two-port, bus voltage has been represented internal storage battery voltage, through obtaining removing the bus voltage value V of high frequency noise behind the single order low frequency filtering _DC/DC

Entire car controller is accepted the motor speed signal r of CAN bus transfer _MotorWith throttle position signal Acc_ps, look into the target torque (Fig. 3) of power taking machine by torque M AP figure interpolation.Motor target torque T _MotorNeed just to be used for power calculation power upper limit and power upper limit etc. when quickening when torque upper limit when these restrictions comprise hybrid power, pure electronic torque through restriction under the specific driving situation.

Motor target torque T after restriction _MotorWith motor speed r _MotorProduct can obtain motor horsepower output demand, and the ratio of it and efficient can obtain the gross horsepower P of input electric machine controller on the bus _Motor, efficient comprises the electric machine controller efficiency eta _{Motor_ctr}With electrical efficiency η _MotorTwo parts, they are that motor and electric machine controller are obtained parameter by the off-line matching and calibration, are the nonlinear functions of temperature.

Through above-mentioned processing, obtained the motor demand power after, can realize the fuel cell energy feedback regulation, specific practice is the power P with the auxiliary power consumable part _AUXBe superimposed upon on the motor demand power.With air-conditioning power is example, air-conditioning demand power P _CondCan be expressed as follows:

Comprise the motor demand this moment and comprise the gross horsepower P of other auxiliary device power at the internal power consumable part _MixCan be expressed as:

P _mix＝P _motor+P _cond

The battery charge will state can show according to its SOC, thus on the method to keep its SOC at a certain thresholding SOC of place _LimValue be standard: if SOC＞SOG _Lim, illustrate that its internal charge is full, fully allow its discharge can reduce the fuel cell consumption of hydrogen fuel; If SOC＜SOC _LimIllustrate that its internal charge wanes, if excessively allow its discharge can reduce storage battery service life, tackle battery charge this moment, certainly what can according to SOC to accumulator cell charging and discharging, and be a research topic on optimum theory, in this engineering territory the degree that fuel-cell fuel reduce to consume, for simplicity, then be according to (SOC _Lim-SOC) difference is carried out linear regulation, and concrete formula is expressed as follows:

P _bat＝P _max×(SOC _lim-SOC)

Output P wherein _BatBe accumulator cell charging and discharging power; P _MaxFor the storage battery maximum discharges and recharges power.Certainly, SOC _LimAnd P _MaxCan obtain by the method that the off-line examination is gathered, principle is P _BatBe no more than the minimum value of charge power restriction and discharge power restriction.Get P in this method _Max=90KW, SOC _Lim=0.8.

Like this, the DC/DC gross horsepower estimated valve P that should export _DC/DCFor:

P _DC/DC＝P _mix+P _bat＝(T _motor×r _motor)/(η _{motor_ctr}×η _motor)+P _cond+P _max×(SOC _lim-SOC)

Can find out as SOC＞SOC by following formula _LimThe time, P _Bat＜0, P _DC/DCThen reduce, explanation should be by the part power transfer of fuel cell burden to storage battery; As SOC＜SOC _LimThe time, P _Bat＞0, P _DC/DCThen increase, illustrate that fuel cell born power demand of motors and battery charge power two parts energy simultaneously.Following formula has carried out the energy back adjusting according to the SOC value to fuel cell, simple in structure and easy row.

At last, according to gross horsepower estimated valve P _DC/DCWith bus voltage value V _DC/DC, can calculate DC/DC output current value I _DC/DC, as shown in the formula:

I _DC/DC＝P _DC/DC/V _DC/DC

This I _DC/DCThrough first-order filtering, satisfy DC/DC changer dynamic adjustments respective process after, send to the DC/DC controller by entire car controller by the CAN bus communication, realize the DC/DC current control.

Fig. 3 is driver driving intention MAP figure.Can ask for the motor target torque value according to accelerator pedal position and current motor speed, increase with pedal position, under the same rotational speed, the target torque amount increases, and has reflected the driver driving intention; And under same pedal position condition, by motor characteristic as can be known, increase with rotating speed, Motor torque can reduce gradually, and physical relationship passes through off-line calibration.

Claims (1)

1, a kind of fuel cell car energy control method based on the CAN bus network communication, its hardware mainly comprises motor, fuel cell and storage battery, and DC/DC DC converter, they are parallel on the bus, finish power supply and demand transformational relation, thereby satisfy the bus driving demand, it is characterized in that, this method may further comprise the steps:

(1) acquisition of signal: gather the storage battery port voltage as bus voltage signal V by the CAN bus _DC/DCGather motor speed signal r by the CAN bus _MotorGather accelerator pedal signal Acc_ps by the CAN bus and all send entire car controller to;

(2) in entire car controller, look into the target torque T of power taking machine by torque M AP figure _Motor, equation expression is:

T _motor＝f(r _motor，Acc_ps)，

Output T wherein _MotorBe the target torque of motor, input r _MotorBe the current rotating speed of motor, Acc_ps is an accelerator pedal position, represents with percentum, and f () expression is tabled look-up and used nonlinear function;

(3) in entire car controller, calculate motor demand gross horsepower P _Motor:

P _motor＝(T _motor×r _motor)/(η _{motor_ctr}×η _motor)

Output P wherein _MotorBe motor demand gross horsepower, η _{Motor_ctr}Be electric machine controller efficient, η _MotorBe electrical efficiency;

(4) in entire car controller, calculate other auxiliary device power demands P _AUX, can obtain the rating horsepower value:

P _mix＝P _motor+P _AUX

P wherein _MixExpression comprises the motor demand and comprises the gross horsepower of other auxiliary device power at the internal power consumable part;

(5) in entire car controller, calculating accumulator discharges and recharges power:

P _bat＝P _max×(SOC _lim-SOC)

Output P wherein _BatBe accumulator cell charging and discharging power; P _MaxFor the storage battery maximum discharges and recharges power;

(6) in entire car controller, calculate DC/DC horsepower output P _DC/DCFor:

P _DC/DC＝P _mix+P _bat＝(T _motor×r _motor)/(η _{motor_ctr}×η _motor)+P _cond+P _max×(SOC _lim-SOC)

(7) in entire car controller, calculate DC/DC outgoing current I _DC/DCFor:

I _DC/DC＝P _DC/DC/V _DC/DC

(8) this I _DC/DCThrough first-order filtering, satisfy DC/DC changer dynamic adjustments respective process after, send to the DC/DC controller by entire car controller by the CAN bus communication, realize the DC/DC current control.

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