CN111645544A - Plug-in electric automobile integrated charging system with active filtering function - Google Patents

Abstract

The invention discloses a plug-in electric vehicle integrated charging system with an active filtering function. During traction battery charging, the three-phase power converter is considered as two parts: a front-end full-bridge converter (FE-FBC) and a middle-end half-bridge converter (ME-HBC). Inductor L_aAfter being connected with the FE-FBC, the single-phase PWM rectifier is formed; inductor L_auxAnd a capacitor C_auxAfter being connected in series, the power divider is connected to the midpoint of the ME-HBC to form a voltage-reducing power decoupling circuit; 8 IGBT and high-frequency transformer groupBecomes an isolated bidirectional CLLC resonant circuit (BE-FBC). In the charging process of the auxiliary battery, the traction battery is isolated by the CLLC converter, and then the auxiliary battery is charged after the Buck circuit formed by ME-HBC reduces the voltage. Three relay switches are added in the integrated charging topology, so that four different working modes of the integrated charging topology of the whole vehicle system can be realized.

Description

Plug-in electric automobile integrated charging system with active filtering function

Technical Field

The invention relates to a plug-in electric vehicle integrated charging system with an active filtering function.

Background

Compared with a power automobile, a plug-in electric automobile is receiving more and more attention and development due to the excellent characteristics of zero emission, low noise, high efficiency and the like, and as a core technology of the electric automobile, an electric automobile driving system and a charging system are particularly important. In the traditional electric automobile, a driving system, a traction battery charging system and an auxiliary battery charging system are independent respectively, so that the volume, the weight and the cost of the electric automobile are increased, and the future development of the electric automobile is greatly limited. Moreover, when the conventional vehicle-mounted charging system of the electric vehicle is connected to a single-phase power socket to charge the traction battery, a large secondary ripple is generated and injected into the traction battery, which greatly affects the service life of the traction battery. Although ripples can be eliminated by connecting the electrolytic capacitor with large capacity in parallel at the direct current side, the electrolytic capacitor has large volume, short service life and poor safety performance, and the whole service life and the application environment of the electric automobile are seriously influenced. Aiming at the problems, the plug-in integrated charging system with the active filtering function is designed, the charging system and the driving system are combined into a whole, the integration level of the plug-in electric automobile is improved, and the problem of secondary ripples existing in single-phase charging is solved under the condition that a large-capacity electrolytic capacitor is not required to be connected in parallel.

When the plug-in electric automobile is in a charging state, the electric drive system is in a stop state, and the charging system is composed of a power switch device and an inductor, so that the power switch device of the electric drive system at the moment can be utilized to form the charging system, the integration level and the charging flexibility of the whole system can be greatly improved, and the cost and the volume of the system are reduced. Meanwhile, an active filtering module can be formed by utilizing power switching devices of a driving system to solve the problem of secondary ripples caused by single-phase charging, and the problems of size and service life caused by parallel connection of large electrolytic capacitors are avoided. The existing patents require an additional active filter circuit to eliminate the secondary ripple and an additional auxiliary battery charging system to charge the auxiliary battery.

Disclosure of Invention

In view of the above problems, the present invention provides a plug-in electric Vehicle integrated charging system with an active filtering function, which can achieve four functions of eliminating a secondary ripple (grid to grid-G2V), feeding back energy from a Traction battery to a power grid (Vehicle to grid-V2G), charging an auxiliary battery from the Traction battery (Traction battery to automatic battery-T2A), and driving a motor (Traction battery to motor-T2M) under the condition that a single-phase power grid charges the Traction battery without adding an additional circuit.

The invention adopts the following technical scheme for solving the technical problems:

a plug-in electric automobile integrated charging system with an active filtering function comprises a motor, a single-phase PWM rectifier, an isolated bidirectional CLLC resonance circuit and an auxiliary battery v_auxAnd a traction battery v_tra；

The three-phase voltage type PWM rectifier comprises an inductor L_aCapacitor C_dcInductor L_auxCapacitor C_auxAnd first to third half-bridge circuits connected in parallel, an inductor L_aOne end of the first half-bridge circuit is connected with the midpoint of the first half-bridge circuit, the other end of the first half-bridge circuit is connected with one end of the charging interface, and the other end of the charging interface is connected with the midpoint of the second half-bridge circuit; electric motor passing relay switch J_aAre respectively connected with the middle points of the three half-bridge circuits; inductor L_auxIs connected with the midpoint of the third half-bridge circuit, and the other end is connected with the midpoint of the third half-bridge circuit through a relay switch J_bRespectively connected with a capacitor C_auxAnd an auxiliary battery v_auxPositive electrode connection of (1), capacitor C_auxThe other end of (b), an auxiliary battery v_auxRespectively connected with a capacitor C_dcNegative electrode of (1), capacitor C_dcConnected in parallel with the first to third half-bridge circuits;

the isolated bidirectional CLLC resonance circuit comprises a first full-bridge circuit, a second full-bridge circuit, a high-frequency transformer, an output filter capacitor Ctra, a first full-bridge circuit connected with the primary side of the high-frequency transformer, and a capacitor C_dcA second full-bridge circuit connected in parallel with the secondary side of the high-frequency transformer via a relay switch J_cAnd a capacitor C_dcParallel connection;

the traction battery and the output filter capacitor Ctra are respectively connected with the second full bridge circuit in parallel.

Compared with the prior art, the invention adopting the technical scheme has the following technical effects:

the invention can realize four functions of eliminating secondary ripples (Grid to Grid-G2V), feeding back energy to the power Grid (Grid to Grid-V2G), charging auxiliary batteries by the Traction battery (Traction battery to automatic battery-T2A) and driving motors of the Traction battery (Traction battery to motor-T2M) under the condition that a single-phase power Grid charges the Traction battery without adding an additional circuit.

Drawings

FIG. 1 is a plug-in electric vehicle integrated charging topology;

FIG. 2 is a G2V mode circuit topology;

FIG. 3 is an operating state of the power decoupling circuit, wherein (a) is state 1, (b) is state 2, (c) is state 3, and (d) is state 4;

FIG. 4 is an operating state of a bidirectional LLC, wherein (a) is state 1, (b) is state 2, (c) is state 3, and (d) is state 4;

FIG. 5 is a V2G mode circuit topology;

FIG. 6 is a T2A mode circuit topology;

FIG. 7 is an operating state of the Buck circuit, in which (a) is state 1 and (b) is state 2;

fig. 8 is a T2M mode circuit topology.

Detailed Description

The technical scheme of the invention is further explained in detail by combining the attached drawings:

the integrated charging topology of the plug-in electric vehicle provided by the patent of the invention is shown in fig. 1.In the driving process of the motor, a three-phase winding of the motor is connected with a three-phase power converter, and the voltage on the side of the direct current bus is inverted by the three-phase power converter to generate three-phase alternating current to drive the motor. During traction battery charging, the three-phase power converter is considered as two parts: a front-end full-bridge converter (FE-FBC) and a middle-end half-bridge converter (ME-HBC). Additional inductance L_aAfter being connected with the FE-FBC, the single-phase PWM rectifier is formed, and the input single-phase alternating current is rectified into direct current to charge the traction battery. In addition, the inductance L_auxAnd a capacitor C_auxAfter being connected in series, the power divider is connected to the midpoint of the ME-HBC to form a voltage-reducing power decoupling circuit, and secondary ripples brought in the single-phase charging process can be filtered. Capacitor C with very small capacity_dcAnd the high-order harmonic waves are filtered out from the circuit by being connected in parallel on the side of the direct-current bus. 8 Insulated Gate Bipolar Transistors (IGBT) Q₇～Q₁₄An isolated bidirectional CLLC resonance circuit (BE-FBC) is formed with the high-frequency transformer, so that the traction battery is electrically isolated from a power grid and an auxiliary battery, and the safety of the whole vehicle system is improved. Due to the characteristic of bidirectional energy flow of the bidirectional CLLC converter, the residual energy in the traction battery can be fed back to the power grid. In the charging process of the auxiliary battery, the traction battery is isolated by the CLLC converter, and then the auxiliary battery is charged after the Buck circuit formed by ME-HBC reduces the voltage. In order to realize the flexible switching of different functions of the whole vehicle system, three relay switches J are added in the integrated charging topology_a、J_bAnd J_c. According to the state of the relay switch, four different working modes of the integrated charging topology of the whole vehicle system can be realized.

The integrated plug-in electric vehicle charging system provided by the invention has four different functions, including: grid charging traction batteries (G2V), battery feedback energy to the grid (V2G), traction battery charging auxiliary batteries (T2A), and traction battery driving motors (T2M). The first table lists the switching states of the relay and the IGBT under different functions.

TABLE 1 switching states of Relay and IGBT under different functions

Mode(s)

#

Energy flow

Ja

Jb

Jc

Q1～Q4

Q5～Q6

Q7～Q14

G2V

1

Vgrid→Vtra

Disconnect

"2" is connected "

Disconnect

PWM signal

PWM signal

PFM signal

V2G

2

Vtra→Vgrid

Disconnect

Disconnect

Disconnect

PWM signal

Closing device

PFM signal

T2A

3

Vtra→Vaux

Disconnect

Is connected with '1'

Disconnect

Closing device

PWM signal

PFM signal

T2M

4

Vtra→Vdc

Closure is provided

Disconnect

Closure is provided

PWM signal

PWM signal

Closing device

One, G2V mode

When relay switch J_aAnd J_cBreak, J_bWhen "2" is switched on, the G2V mode circuit structure is as shown in fig. 2. At this time, the FE-FBC of the motor drive system power converter is used as an AC/DC converter to rectify AC power into DC power, and the BE-HBC and the inductor L are connected_auxAnd a capacitor C_auxAnd a power decoupling circuit is formed so as to eliminate secondary ripples brought by charging. After the stable DC bus voltage is isolated by the CLLC resonance circuit, the voltage is fed to the traction deviceAnd charging the battery.

In the G2V mode, the operation of the power decoupling circuit is as shown in fig. 3. When the secondary ripple current i_sAbove zero, the power decoupling circuit operates in Buck mode, as shown in (a), (b) of fig. 3. When IGBT Q₅When on, current passes through inductor L_auxCapacitor C_auxCharging; when IGBT Q₅When turned off, is stored in inductor L_auxThrough diode D₆Continuously supplying the capacitor C_aux。

When the secondary ripple current i_sWhen the voltage is less than zero, the power decoupling circuit works in a Boost mode, as shown in (c) and (d) of fig. 3. When IGBT Q₆When turned on, the capacitor C_auxThrough an inductance L_auxAnd IGBT Q₆Discharging; when IGBT Q₆When turned off, the capacitor C_auxThrough an inductance L_auxAnd diode D₅And (4) discharging.

On the other hand, the CLLC resonant circuit realizes the isolation between the power grid and the traction battery, and ensures the safety of the traction battery. The operating states of the bidirectional CLLC resonant circuit are shown in fig. 4 (a) to (d), for a total of eight states, in which the four states of the first half cycle are the same as the four states of the second half cycle, and only the operating state of the first half cycle is listed here.

Two, V2G mode

When the traction battery energy is left, the energy left in the battery can be fed back to the grid due to the energy bidirectional flow characteristic of the integrated charging topology. When three relay switches J_a、J_bAnd J_cWhen both are off, the integrated charging topology operates in the V2G mode. This mode of operation is the same as the G2V mode, except for the direction of energy flow, as shown in fig. 5.

Three, V2A mode

When relay switch J_aAnd J_cBreak, J_bWhen the power supply is switched to '1', the plug-in electric vehicle integration topology works in a T2A mode, the traction battery charges the auxiliary battery, and the circuit structure is shown in fig. 6. ME-HBC and inductor L_auxForm a Buck circuit, and the traction battery is isolated by a CLLC circuit and then a busThe line voltage is reduced through the Buck circuit, and finally the auxiliary battery is charged.

In the T2A mode, the Buck circuit composed of ME-HBCs has two operating states, as shown in (a) and (b) of fig. 7. When IGBT Q₅When conducting, the charging current flows through Q₅And an inductance L_auxFlows to the auxiliary battery as shown in (a) of fig. 7. Inductance L at this stage_auxEnergy is stored. When IGBT Q₅When it is cut off, it is stored in inductor L_auxVia a diode D₆Flows to the auxiliary battery as shown in (b) of fig. 7. Inductance L at this stage_auxThe energy in (1) charging the auxiliary battery, inductor L_auxEnergy is released.

Four, T2M mode

When relay switch J_aAnd J_cOpening, J_bWhen disconnected, the integrated plug-in electric vehicle charging topology operates in a drive mode, as shown in fig. 8. The traction battery is directly connected to the side of the direct current bus, the three-phase windings of the motor are respectively connected to the middle point of the power bridge, and the three-phase power converter inverts the voltage of the direct current bus into three-phase voltage so as to drive the motor to rotate.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can understand that the modifications or substitutions within the technical scope of the present invention are included in the scope of the present invention, and therefore, the scope of the present invention should be subject to the protection scope of the claims.

Claims (2)

1. A plug-in electric automobile integrated charging system with an active filtering function is characterized by comprising a motor, a single-phase PWM rectifier, an isolated bidirectional CLLC resonance circuit and an auxiliary battery v_auxAnd a traction battery v_tra；

The three-phase voltage type PWM rectifier comprises an inductor L_aCapacitor C_dcInductor L_auxCapacitor C_auxAnd first to third half-bridge circuits connected in parallel, an inductor L_aOne end of the first half-bridge circuit is connected with the midpoint of the first half-bridge circuit, and the other end of the first half-bridge circuit is connected with the chargerOne end of the electric interface, the other end of the charging interface is connected with the midpoint of the second half-bridge circuit; electric motor passing relay switch J_aAre respectively connected with the middle points of the three half-bridge circuits; inductor L_auxIs connected with the midpoint of the third half-bridge circuit, and the other end is connected with the midpoint of the third half-bridge circuit through a relay switch J_bRespectively connected with a capacitor C_auxAnd an auxiliary battery v_auxPositive electrode connection of (1), capacitor C_auxThe other end of (b), an auxiliary battery v_auxRespectively connected with a capacitor C_dcNegative electrode of (1), capacitor C_dcConnected in parallel with the first to third half-bridge circuits;

the isolated bidirectional CLLC resonance circuit comprises a first full-bridge circuit, a second full-bridge circuit, a high-frequency transformer, an output filter capacitor Ctra, a first full-bridge circuit connected with the primary side of the high-frequency transformer, and a capacitor C_dcA second full-bridge circuit connected in parallel with the secondary side of the high-frequency transformer via a relay switch J_cAnd a capacitor C_dcParallel connection;

the traction battery and the output filter capacitor Ctra are respectively connected with the second full bridge circuit in parallel.

2. The integrated charging system with active filtering function for plug-in electric vehicles as claimed in claim 1, wherein two full bridge circuits of the isolated bidirectional CLLC resonant circuit are respectively composed of eight igbt transistors.

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