KR101141770B1 - electric energy charging and discharging apparatus and method using super capactiors for regenerative braking system of electric motorcycles - Google Patents

Abstract

The present invention relates to an energy charge / discharge control device of a regenerative braking apparatus for an electric vehicle, comprising: a battery capable of supplying electric power to a wheel driving motor of an electric vehicle through an inverter, and at least one supercapacitor connected in series; The auxiliary charging unit, a bidirectional converter connected between the battery and the auxiliary charging unit to switch the current conduction direction according to the control signal, the load current supplied to the inverter, the regenerative current flowing back through the inverter during braking, The current detector detects the charge / discharge current flowing between the bidirectional converters, the speed detector detects the speed of the electric vehicle, and the information output from the current detector controls the bidirectional converter, and determines whether the electric vehicle is in an acceleration mode or a braking mode. In braking mode, the regenerative current is charged until the auxiliary charging unit reaches the rated voltage. And a control unit for controlling the bidirectional converter so as to vary the duty ratio, which is a ratio of time to be turned on in the switching period of the bidirectional converter, according to the charging voltage of the auxiliary charging unit. According to the energy charging and discharging control device and method of the regenerative braking device of the electric vehicle, it is possible to increase the storage efficiency of the energy generated from the electric motor during braking to increase the operating distance of the electric vehicle possible with a single battery charging Not only can it be used for a long time by extending its life, but it also provides the advantage of suppressing the failure of the electric energy storage device.

Description

Electric energy charging and discharging apparatus and method using super capactiors for regenerative braking system of electric motorcycles}

The present invention relates to an apparatus for controlling energy charging and discharging of a regenerative braking apparatus for an electric vehicle, and more particularly, to a regenerative braking apparatus for an electric vehicle capable of performing charging and discharging by applying a bidirectional converter between a battery and a supercapacitor. An energy charging and discharging control device and method.

In general, electric vehicles such as electric motorcycles, electric bicycles, and electric vehicles are capable of driving electric motors, which are motors, by using the power of a battery. It can be consumed with heat energy or charged using a battery.

However, in the case of storing electrical energy by using the battery, due to the charging and discharging characteristics of the battery, the regenerative power energy generated in a short time cannot be effectively stored, and the efficiency is very bad and the frequent charging and discharging shortens the battery life, thereby reducing the durability of the battery. There is this. In addition, in the case of using electrical resistance, regenerative braking is possible, but there is a disadvantage in that electrical energy is released as heat.

In order to improve this problem, Korean Laid-Open Patent Publication No. 2003-0006269 discloses a control method of an energy storage system that can increase charging efficiency by adding a supercapacitor.

The energy storage system has a structure in which a DC / DC converter is connected in parallel with the battery between the battery and the inverter, and a supercapacitor is connected in series, and the DC / DC converter controls the voltage in inverse proportion to the traveling speed. have.

This conventional energy storage system is difficult to maximize the charging and discharging efficiency and energy utilization efficiency of the electric energy by not considering the voltage fluctuation state of the supercapacitor during the charge and discharge of the supercapacitor and the required load current or the amount of regenerative current detected. There is this.

The present invention was devised to improve the above problems, and according to the operating state of the motor, while controlling the electrical energy storage efficiency between the battery and the supercapacitor, the voltage is controlled to minimize the electrical transient occurring during the charging and discharging process. The purpose of the present invention is to provide an energy charging / discharging control device and method of a regenerative braking apparatus for an electric vehicle that can increase reliability by preventing a failure.

In order to achieve the above object, the energy charge / discharge control apparatus of the regenerative braking apparatus for an electric vehicle according to the present invention includes a battery capable of supplying electric power through an inverter to a wheel driving motor of an electric vehicle; An auxiliary charging unit in which at least one supercapacitor is interconnected in series; A bidirectional converter connected between the battery and the auxiliary charging unit to switch the current conduction direction according to a control signal; A current detector for detecting a load current supplied to the inverter, a regenerative current flowing back from the motor through the inverter during braking, and a charge / discharge current flowing between the battery and the bidirectional converter; A speed detector for detecting a speed of the electric vehicle; A first voltage detector detecting a voltage of the battery; A second voltage detector detecting a voltage of the auxiliary charging unit; The bidirectional converter is controlled by using the information output from the speed detector and the current detector, and it is determined whether the electric vehicle is in an acceleration mode or a braking mode. And a control unit for controlling the bidirectional converter to charge the current, and varying the duty ratio, which is a ratio of time to be conducted (turned on) within the switching period of the bidirectional converter according to the charging voltage of the auxiliary charging unit.

Preferably, the bidirectional converter is switched on / off by a pulse width modulation (PWM) control signal of the control unit and is connected to form a current conduction path from the positive terminal of the battery toward the positive terminal of the auxiliary charging unit. A switching element; A first diode connected in parallel with the first switching element, and connected to form a current conduction path in a reverse direction with respect to the current conduction direction of the first switching element; A second switching element connected in parallel between the positive terminal and the negative terminal of the auxiliary charging part and connected to form a current conduction path from the positive terminal of the auxiliary charging part to the negative terminal of the auxiliary charging part; A second diode connected in parallel with the second switching element and connected to form a current conduction path in a reverse direction with respect to the current conduction direction of the second switching element, wherein the second switching element is formed from an anode terminal of the auxiliary charging unit. And a first inductor installed on the current conduction path leading to the inductor.

The current detector may include a first current detector configured to detect a load current supplied to the inverter; A second current detector for detecting a regenerative current flowing backward from the electric motor through the inverter when braking the electric vehicle; And a third current detector for detecting a charge / discharge current flowing between the battery and the bidirectional converter, wherein the control unit determines that the braking mode is provided when a regenerative current is detected by the second current detector.

More preferably, a second inductor connected between the first switching element and the positive terminal of the battery and a first capacitor connected in parallel with the bidirectional converter to suppress overvoltage generated during charging and discharging of the auxiliary charging unit. It further comprises an overvoltage buffer.

According to one aspect of the invention, the control unit includes a reference charge and discharge current value calculation unit for calculating a reference current from the speed and the load current of the electric vehicle detected by the speed detection unit; A proportional integral controller configured to proportionally integrate the attenuation error between the reference current and the charge / discharge current; A duty ratio adjusting unit for adjusting a duty ratio for driving the bidirectional converter based on the output signal of the proportional integral controller; A pulse width modulator for generating a pulse width control signal corresponding to the duty ratio adjusted by the duty ratio adjuster; And a switching driver configured to apply the driving pulse signal generated by the pulse width modulator to the first switching element in the braking mode and to the second switching element in the acceleration mode.

The auxiliary charging unit may further include: a resistance element connected in parallel with each of the plurality of supercapacitors connected in series; A zener diode connected in parallel with both ends of the auxiliary charging unit is preferably further provided.

In addition, the energy charging and discharging control method of the regenerative braking apparatus of the electric vehicle according to the present invention in order to achieve the above object in parallel through a battery and a bi-directional converter to supply power to the wheel drive motor of the electric vehicle through an inverter. A method for controlling energy charging and discharging of a regenerative braking apparatus for an electric vehicle having a connected auxiliary charging unit, comprising: a. Setting a reference duty ratio to be applied to the bidirectional converter during charging and discharging; I. Calculating a reference charge / discharge current required from the speed of the electric vehicle, the load current supplied to the inverter, and the regenerative current; All. Performing proportional integral control to reduce a difference between the reference charge / discharge current and the charge / discharge current flowing through the bidirectional converter; la. Determining whether a braking mode or an acceleration mode is detected from the regenerative current flowing backward from the motor through the inverter; hemp. Determining whether the voltage of the battery is greater than a first reference voltage that is set and the voltage of the auxiliary charging unit is lower than or equal to a second reference voltage when the braking mode is determined in step (d); bar. And increasing the duty ratio of the pulse width applied to the bidirectional converter when the voltage of the battery is higher than the first reference voltage and the charging voltage of the auxiliary charging unit is lower than the second reference voltage. .

In addition, when it is determined that the voltage of the battery is less than or equal to the set first reference voltage or the voltage of the auxiliary charging unit is greater than the set second reference voltage, the duty ratio of the pulse width applied to the bidirectional converter may be reduced. It is preferable to include a.

According to the energy charging and discharging control device and method of the regenerative braking apparatus of the electric vehicle according to the present invention, it is possible to increase the storage efficiency of the energy generated from the motor during braking to increase the operating distance of the electric vehicle possible with a single battery charging It can be used for a long time by extending the battery life and suppressing the failure of the electric energy storage device.

1 is a block diagram showing an energy charge and discharge control device of the regenerative braking apparatus for an electric vehicle according to the present invention;
FIG. 2 is a block diagram of the control unit of FIG. 1,
3 is a detailed circuit diagram of the auxiliary charging unit of FIG. 1;
Figure 4 is a flow diagram showing the energy charge and discharge control process of the regenerative braking apparatus of the electric vehicle in the present invention,
5 to 7 are graphs showing simulation results of charging current during regenerative braking for the energy charge / discharge control device of the regenerative braking apparatus for an electric vehicle according to the present invention;
8 to 10 are graphs showing simulation results of charging voltage during regenerative braking for the energy charge / discharge control device of the regenerative braking apparatus for an electric vehicle according to the present invention;
11 to 14 are graphs showing simulation results during acceleration of the energy charge / discharge control device of the regenerative braking apparatus for an electric vehicle according to the present invention.

Hereinafter, an apparatus and method for controlling energy charge and discharge of a regenerative braking apparatus for an electric vehicle according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing an energy charge and discharge control device of the regenerative braking apparatus for an electric vehicle according to the present invention.

Referring to FIG. 1, the energy charge / discharge control apparatus 100 of the regenerative braking apparatus for an electric vehicle includes a battery 110, an auxiliary charging unit 120, a bidirectional converter 130, and first to third current detectors 141 to 143. ), First and second voltage detectors 151 and 152, an inverter 170, a speed detector 180, an overvoltage buffer 190, and a control unit 200.

The motor (M) 230 is applied as a wheel driving motor of the electric vehicle (EV) 250, and generally applies a brushless (BLDC) motor, and is driven by the power supplied through the inverter 170 and At the same time, the regenerative current is output through the reflux diodes D11 to D16 connected in parallel with the electrical energy generated by the rotation to the switching elements S1 to S6 of the inverter 170.

The speed detector 180 detects the speed of the electric vehicle driven by the motor 230, and a Hall sensor may be applied, and outputs the detected speed information to the control unit 200.

The inverter 170 converts the DC power supplied from the battery 110 or the auxiliary charging unit 120 as a voltage source into an AC phase by switching elements S1 to S6 selectively controlled by a brushless motor driver (not shown). It is to be supplied to the three-phase motor 230, the structure is known, detailed description thereof will be omitted.

The battery 110 is connected to both ends of the inverter 170 to supply power through the inverter 170.

The battery 110 may be a known one such as a lithium ion battery.

Reference numeral C2 denotes a smoothing capacitor connected between the battery 110 and the inverter 170.

As shown in FIG. 3, the auxiliary charging unit 120 is connected in parallel with the battery 110 through a bidirectional converter 130 which will be described later so that a plurality of supercapacitors 121 may be interconnected in series to charge or discharge energy. It is.

Here, the supercapacitor 121 refers to a capacitor having a low voltage (2.7V) and a large capacity (100 to 1000F). The supercapacitor 121 uses a metal oxide and a polymer compound to charge a charge between the anodes, thereby charging the charge by an electrochemical action. The structure is different from the battery 110.

Therefore, the auxiliary charging unit 120 may be used in the form of a bank by connecting a plurality of supercapacitors 121 in series so as to suit the required voltage level, to suppress the uneven charging phenomenon by the series connection, and to prevent the overcharge phenomenon. It is desirable that it be constructed.

Preferably, the auxiliary charging unit 120 includes a resistor element 123 connected in parallel with each of the plurality of supercapacitors 121 connected in series for equalizing charge between the plurality of supercapacitors 121, and the auxiliary charging unit 120. And a zener diode ZD1 connected in parallel with both ends.

Here, the zener diode ZD1 has been applied for overvoltage suppression in order to prevent burnout due to overcharging of the super capacitor 121 of the auxiliary charging unit 120.

The bidirectional converter 130 is connected between the battery 110 and the auxiliary charging unit 120 to switch the current conduction direction according to the control signal of the control unit 200.

The bidirectional converter 130 includes a first switching device T1, a second switching device T2, and first and second diodes D1 and D2.

The first switching element T1 is switched on / off by the control signal of the control unit 200 and the current conduction path is directed from the positive terminal 112 of the battery 110 to the positive terminal 125 of the auxiliary charging unit 120. An IGBT element, which is connected to form a circuit and is a three-terminal power switching element, can be applied.

The first diode D1 is connected in parallel between the drain terminal and the source terminal of the first switching element T1 so as to form a current conduction path in a reverse direction with respect to the current conduction direction of the first switching element T1.

The second switching element T2 is connected between the first switching element T1 and the ground G corresponding to the negative electrode terminal 127 of the auxiliary charging unit 120.

That is, the second switching element T2 is connected in parallel between the positive electrode terminal 125 and the negative electrode terminal 127 of the auxiliary charging unit 120 to connect the auxiliary charging unit 127 from the positive terminal 125 of the auxiliary charging unit 120. It is connected so as to form a current conduction path in the negative terminal direction.

An IGBT device, which is a three-terminal power switching device, may also be applied to the second switching device T2.

The second diode D2 is connected in parallel between the drain terminal and the source terminal of the second switching element T2 so as to form a current conduction path in a reverse direction with respect to the current conduction direction of the second switching element T2.

The first inductor L1 is provided on a current conduction path extending from the anode terminal 125 of the auxiliary charging unit 120 to the source terminal of the first switching element T1 and the drain of the second switching element T2.

The current detector detects a load current supplied to the inverter 170, a regenerative current flowing back from the motor 230 through the inverter 170 when braking, and a charge / discharge current flowing between the battery 110 and the bidirectional converter 130. First to third current detectors CS1 to CS3 141 to 143 have been applied.

The first current detector (CS1) 141 is installed on the current supply path 172 from the battery 110 to the inverter 170 to detect the load current supplied to the inverter 172 to the control unit 200 Output

The third diode D3 is connected between the first current detector 141 and the positive terminal 112 of the battery 110 so that only a current supplied to the inverter 170 can be conducted.

The second current detector 142 detects the regenerative current flowing through the fourth diode D4 connected on the regenerative current conduction path 174 connected in parallel with the current supply path 172 leading to the inverter 170. It is installed to do this.

Here, the regenerative current refers to a current flowing backward from the motor 230 through the reflux diodes D11 to D16 of the inverter 170 when the electric vehicle 250 is braked.

The third current detector 143 may be configured to detect the positive and negative terminals 112 of the battery 110 and the bidirectional converter 130 so as to detect the charge / discharge current I3 flowing between the battery 110 and the bidirectional converter 130. It is connected between the drains of one switching element T1.

The charge / discharge current information detected by the third current detector 143 is also used to control the suppression of overcharge by the control unit 200 described later.

The overvoltage buffer 190 is a second inductor connected between the drain of the first switching element T1 and the positive terminal 112 of the battery 110 to suppress the overvoltage generated during charging and discharging of the auxiliary charging unit 120. L2 and a first capacitor C1 connected in parallel with the bidirectional converter 130.

The first voltage detector 151 detects the voltage of the battery 110 and provides the voltage to the control unit 200.

The second voltage detector 152 detects the voltage of the auxiliary charging unit 120 and provides the voltage to the control unit 200.

The control unit 200 uses speed information of the electric vehicle 250 detected by the speed detector 180, information detected by the current detector, and information detected by the first and second voltage detectors 151 and 152. To control the bidirectional converter 130.

The control unit 200 determines whether the electric vehicle 250 is in an acceleration mode or a braking mode. In the braking mode, the regenerative current is increased until the auxiliary charging unit 120 reaches the rated voltage in preference to the battery 110. While controlling the bidirectional converter 130 to be charged, the pulse width modulation (PWM) duty ratio, which is the ratio of the time that is turned on in the switching cycle of the bidirectional converter 130, is varied according to the charging voltage of the auxiliary charging unit 120. To control.

Preferably, the control unit is constructed to determine the braking mode when the regenerative current is detected by the second current detector 142.

This control unit will be described in more detail with reference to FIG. 2.

The control unit 200 includes a reference charge / discharge current value calculator 202, a proportional integral (PI) controller 207, a duty ratio adjuster 209, a pulse width modulator (PWM modulator) 211, and a switching driver. 213 is provided.

The reference charge / discharge current value calculator 202 includes a reference charge current value calculator 202a and a reference discharge current value calculator 202b.

The reference charging current value calculator 202a calculates the reference charging current value in the braking mode, and is set based on the speed of the electric vehicle 250 detected by the speed detector 180 and the regenerative current detected by the second current detector 142. The reference charging current Iregen_ref is calculated according to the calculation method. Here, the reference charging current calculation method of the reference charging current value calculating unit 202a is calculated as I _{regen_ref} = K ₁ V _vehicle + K ₂ I _regen for the speed (V _vehicle ) and the regenerative current (I _regen ) of the _vehicle (K ₁ , K ₂ coefficients).

In addition, the reference discharge current value calculator 202b calculates a reference discharge current value in the acceleration mode, and the speed of the electric vehicle 250 detected by the speed detector 180 and the load current detected by the first current detector 141. The reference discharge current Iaccel_ref is calculated according to the calculation method set up from. Here, the reference discharge current calculation method of the reference discharge current value calculation unit 202 is expressed as I _{accel_ref} = K ₃ V _vehicle + K ₄ I _load for the speed V _vehicle and the load current I _load of the electric vehicle 250 ( K ₃ , K ₄ coefficient).

The proportional integration controller 207 is proportionally integrated so that the error is attenuated with respect to an error value between the reference charging current or the reference discharge current and the charging current or the discharge current detected by the third current detector 143, so that the charge / discharge request current, that is, The charge demand current or the discharge demand current is calculated.

The duty ratio adjusting unit 209 adjusts the duty ratio for driving the bidirectional converter 130 based on the output signal of the proportional integral controller 207.

The duty ratio adjusting unit 209 also uses voltage Vbatt information of the battery 110 and voltage information of the auxiliary charging unit 120 when adjusting the duty ratio. As an example, when the voltage of the auxiliary charging unit 120 at the time of charging reaches the rated voltage, a 0% duty ratio is applied to stop driving of the first switching device T1, and the voltage of the auxiliary charging unit 120 is rated at the time of discharge. When the voltage reaches 1/2, the 0% duty ratio of the second switching device may be applied to stop driving of the second switching device T2. In addition, a process of using the voltage of the battery 110 of the duty ratio adjusting unit 209 will be described later with reference to FIG. 4.

The pulse width modulator 211 generates a pulse width control signal corresponding to the duty ratio adjusted by the duty ratio adjuster 209.

The switching driver 213 applies the driving pulse signal generated by the pulse width modulator 211 to the first switching device T1 in the braking mode and to the second switching device T2 in the acceleration mode. .

Hereinafter, this charge and discharge control process will be described with reference to FIG. 4.

First, a reference duty ratio applied to the bidirectional converter 130 by pulse width modulation during charging / discharging is set (step 310). Here, the reference duty ratio is to be applied as an initial value in consideration of the charging and discharging characteristics of the auxiliary charging unit 120 and may be generally set to be 50%.

Next, the speed of the electric vehicle 250, the load current and the regenerative current supplied to the inverter 170 are detected (step 320), and the required reference current, that is, the reference charge / discharge current is calculated using the detected values. (Step 330).

After step 330, the charge / discharge required current is calculated by performing proportional integral control to reduce the difference between the reference charge / discharge current and the charge / discharge current flowing through the bidirectional converter 130 (step 340).

Subsequently, it is determined whether the braking mode or the acceleration mode is detected from the regenerative current flowing from the motor 230 through the inverter 170 (step 350). If the braking mode is determined, the battery 110 voltage Vbatt is determined. The second reference voltage Vr2 in which the voltage of the battery 110 is greater than the set first reference voltage Vr1 with respect to the voltage Vcap of the auxiliary charging unit 120 and the charging voltage Vcap of the auxiliary charging unit 120 is set. (Step 360). Here, the first reference voltage Vr1 is preferably set to zero volts.

In operation 360, if the voltage Vbatt of the battery 110 is higher than the set first reference voltage Vr1 and the charging voltage of the auxiliary charging unit 120 is lower than or equal to the set second reference voltage Vr2, the battery 110 is applied to the bidirectional converter 120. The duty ratio of the pulse width to be increased is increased by the set increment (step 370).

After step 370, the first switching device T1 is driven with the increased duty ratio, and the operation returns to step 320.

Unlike this, if it is determined in step 360 that the voltage Vbatt of the battery 110 is equal to or less than the set first reference voltage Vr1 or the charging voltage of the auxiliary charging unit 120 exceeds the set second reference voltage Vr2. The duty ratio of the pulse width applied to the bidirectional converter 120 is reduced by the set reduction width (step 380).

After step 380, the first switching device T1 is driven with the reduced duty ratio, and the flow returns to step 320.

On the other hand, if it is determined in the acceleration mode in step 350, the third reference voltage (Vbatt) of the charging voltage (Vcap) of the auxiliary charging unit 120 is greater than the set second reference voltage (Vr2), the voltage (Vbatt) is set Vr3) or more (step 400). The third reference voltage is preferably set higher than zero volts.

In operation 400, when it is determined that the charging voltage Vcap of the auxiliary charging unit 120 is greater than or equal to the set second reference voltage Vr2, and the voltage Vbatt of the battery 110 is greater than or equal to the set third reference voltage Vr3, in both directions, The duty ratio of the pulse width to be applied to the converter 120 is increased by the set increment (step 410).

Unlike this, if it is determined that the charging voltage Vcap of the auxiliary charging unit 120 is less than the set second reference voltage Vr2 or that the voltage Vbatt of the battery 110 is less than the set third reference voltage Vr3, the bidirectional direction is determined. The duty ratio of the pulse width to be applied to the converter 120 is reduced by the set increment (step 420).

After operation 410 or operation 420, the second switching device T2 is driven at a duty ratio to which the increase or decrease is applied, and the operation returns to operation 320.

On the other hand, looking at the charging process in the braking mode in this control process, when the braking force is applied to the motor 230 of the electric vehicle 250 in the braking mode by the vehicle inertia force, the motor 230 immediately acts as a generator The current flows backward through the reflux diodes D11 to D16 of the inverter 170, the reverse current is detected through the second and third current detectors 142 and 143, and the first of the bidirectional converter 130. The switching element T1 is turned on with a duty cycle determined by the duty ratio adjustment scheme described above. The first switching element T1 stores a current that is temporarily regenerated in the first inductor L1 in a state where the first switching element T1 is turned on with the determined duty cycle.

In addition, during the period in which the first switching device T1 is turned off while the first switching device T1 is driven at a set duty cycle, the current stored in the first inductor L1 is stored in the auxiliary charging unit through the second diode D2. When the current is stored in the 120 and the first switching device T1 is turned on, the current stored in the second inductor L2 is transferred to the first inductor L1 to store energy. In this process, the auxiliary charging unit 120 is sequentially charged until each of the supercapacitors 121 reaches the terminal voltage, and is controlled so as not to be charged any more when the rated voltage is reached.

On the other hand, when the regenerative power is not detected by the second current detector 142, that is, when a load current is supplied to the normal motor 230, the electric energy stored in the super capacitor 121 of the auxiliary charging unit 120 is converted into a motor ( In order to supply 230, the second switching device T2 is turned on at a PWM duty cycle determined by the duty adjustment scheme described above, and the discharge current is stored in the first inductor L1. do.

In addition, when the second switching device T2 is turned off, the current stored in the first inductor L1 is discharged through the first diode D1 to supply electrical energy to the load of the motor 230 again. Done. Even during the discharge operation, when the regenerative power is detected again by the second current detector 142 or when the terminal voltage of the auxiliary charging unit 120 reaches the set discharge limit voltage, for example, 1/2 of the rated voltage, the discharge operation is stopped. Controlled and ready for charging again.

Simulation Results and Analysis

In this embodiment, as the auxiliary charging unit 120, 10 supercapacitors 121 having a capacity of 100F 2.7V were used, and the output voltage was 10F 27V, and a resistance element 123 for equalization of 10A load current and 20 mA was used. .

In order to verify the performance of the proposed circuit, a circuit simulation was performed using the Simplorer Tool provided by Ansoft Co., USA.

Simulation conditions are assumed to be voltage sources by the role of generators in braking mode, whereas motor loads are assumed for normal motor loads.

The parameters of the active irradiation used in the simulation are shown in Table 1 below.

Parameter unit value Remarks L1 mH 0.2 L2 mH 0.1 C1 uF 200 PI Gain 1 + 100 / s PI controller PWM switching frequency kHz 20

-Simulation result and analysis of circuit during regenerative braking

Circuit simulation results according to regenerative braking are shown separately from the current flow and the voltage state through FIGS. 5 to 10.

5 is a supercapacitor charging current of the auxiliary charging unit, FIG. 6 is an inductor current of the first inductor L1, FIG. 7 is a battery charging current, FIG. 8 is a supercapacitor charging voltage of the auxiliary charging unit, and FIG. 9 is a first switching element T1. ) Input voltage L1 and FIG. 10 show the first inductor voltage, respectively.

As can be seen from the drawing, during the regenerative braking period (0-0.2msec), when the regenerative power is generated, the battery is temporarily charged in the supercapacitor 121 of the auxiliary charging unit 120, and the charging voltage rises rampantly to 27 [V]. When it reaches the charging voltage, it does not charge any more. In this process, the charging current of the battery 110 and the voltage of the first inductor L1 may be checked. In addition, it can be seen that the current charged in the battery 110 approaches zero and most of the current is charged in the supercapacitor 121 of the auxiliary charging unit 120.

-Simulation result and analysis of circuit during normal motor acceleration

The circuit simulation results during acceleration are shown in FIGS. 11 to 14 in the current flow and voltage states. 11 shows a supercapacitor current flow of the auxiliary charging unit, FIG. 12 shows a current flow of the bidirectional inverter 130, FIG. 13 shows a battery current flow, and FIG. 14 shows a supercapacitor voltage state of the auxiliary charging unit.

When power is normally supplied to the motor 230 of the electric vehicle 250, the current of the supercapacitor 121 of the auxiliary charging unit 120 flows in reverse to supply power to the motor 230, and part of the battery 110 is provided. By charging the power to the power stored in the battery 110 is increased to obtain the effect of increasing the use time of the battery 110.

The discharge current of the supercapacitor 121 of the auxiliary charging unit 120 is discharged to 0A within about 0.15 msec at the initial stage of discharging, indicating that all currents stored in the supercapacitor 121 are discharged and ready for recharging. On the other hand, since the motor load current -50A flows, the capacitor charging current means that the current flows in the opposite direction and is discharged. When the total supercapacitor voltage of the auxiliary charging unit 120 becomes 1.0 pu [V] or less, the discharge is stopped and thereafter, the load current flows from the battery 110.

<Performance Analysis>

In order to verify the performance of the proposed circuit, the performance test was performed using an electric bicycle. The experimental apparatus used in the circuit used electric bicycle of 24V, 250W, 1800rpm brushless motor and confirmed the charge / discharge performance as confirmed through the simulation.

110: battery 120: auxiliary charging unit
121: supercapacitor 130: bidirectional converter
170: inverter 200: control unit

Claims (8)

delete delete delete A battery configured to supply electric power to the wheel driving motor of the electric vehicle through an inverter;
An auxiliary charging unit in which at least one supercapacitor is interconnected in series;
A bidirectional converter connected between the battery and the auxiliary charging unit to switch the current conduction direction according to a control signal;
A current detector for detecting a load current supplied to the inverter, a regenerative current flowing back from the motor through the inverter during braking, and a charge / discharge current flowing between the battery and the bidirectional converter;
A speed detector for detecting a speed of the electric vehicle;
The bidirectional converter is controlled by using the information output from the speed detector and the current detector, and it is determined whether the electric vehicle is in an acceleration mode or a braking mode. In the braking mode, the regenerative charger reaches the rated voltage until it reaches the rated voltage. And a control unit controlling the bidirectional converter to charge an electric current, and controlling a duty ratio, which is a ratio of time to be conducted within a switching period of the bidirectional converter, according to the charging voltage of the auxiliary charging unit.
The bidirectional converter
A first switching element switched on / off by a control signal of the control unit and connected to form a current conduction path from a positive terminal of the battery toward a positive terminal of the auxiliary charging unit;
A first diode connected in parallel with the first switching element and connected to form a current conduction path in a reverse direction with respect to the current conduction direction of the first switching element;
A second switching element connected in parallel between the positive terminal and the negative terminal of the auxiliary charging part and connected to form a current conduction path from the positive terminal of the auxiliary charging part to the negative terminal of the auxiliary charging part;
And a second diode connected in parallel with the second switching element and connected to form a current conduction path in a reverse direction with respect to the current conduction direction of the second switching element.
And a first inductor provided on a current conduction path from the anode terminal of the auxiliary charging section to the second switching element.
The current detection unit
A first current detector for detecting a load current supplied to the inverter;
A second current detector for detecting a regenerative current flowing backward from the electric motor through the inverter when braking the electric vehicle;
And a third current detector configured to detect a charge / discharge current flowing between the battery and the bidirectional converter.
The control unit determines that the braking mode when the regenerative current is detected by the second current detector,
A second inductor connected between the first switching element and a positive terminal of the battery to suppress the overvoltage generated during charging and discharging of the auxiliary charging unit, and connected in parallel with the bidirectional converter to suppress overvoltage generation of the auxiliary charging unit; And an overvoltage buffer comprising a first capacitor. An energy charge / discharge control device of a regenerative braking apparatus for an electric vehicle. The method of claim 4, wherein the control unit
A reference charge / discharge current value calculator for calculating a reference charge / discharge current from the speed, the load current, and the regenerative current of the electric vehicle detected by the speed detector;
A proportional integral controller configured to proportionally integrate the attenuation error between the reference charge / discharge current and the charge / discharge current;
A duty ratio adjusting unit for adjusting a duty ratio for driving the bidirectional converter based on the output signal of the proportional integral controller;
A pulse width modulator for generating a pulse width control signal corresponding to the duty ratio adjusted by the duty ratio adjuster;
And a switching driver configured to apply the driving pulse signal generated by the pulse width modulator to the first switching element in the braking mode, and to the second switching element in the acceleration mode. Charge / discharge control device of regenerative braking device. The method of claim 5, wherein the auxiliary charging unit
A resistance element connected in parallel with each of the plurality of supercapacitors connected in series;
And a zener diode connected in parallel with both ends of the auxiliary charging unit. delete delete

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