KR20200062835A - Isolated bi-directional DC-DC converter charger for electric vehicles - Google Patents

Abstract

Provided is an isolated bi-directional DC-DC converter charger for an electric vehicle, capable of receiving a home supply voltage to be converted through a power converter, and controlling charging power through a phase control scheme, thereby prohibiting a rapid dynamic characteristic and an ineffective component to increase the charging efficiency in an electric vehicle having a stack-type charger. The isolated bi-directional DC-DC converter charger for the electric vehicle includes: a power factor correction (PFC) to receive a supply alternating current (AC) power to be converted into a variable direct current (DC) voltage and control a power factor of a voltage current; an isolated-type transformer to electrically isolate a primary side from a secondary side; a first-phase full-bridge inverter interposed between the primary side of the isolated-type transformer and the PFC; a secondary-phase full-bridge inverter interposed between the second side of the isolated-type transformer and the battery; and an inductor interposed between the primary side of the isolated-type transformer and the first-phase full-bridge inverter to output, as power, stored energy.

Description

Isolated bi-directional DC-DC converter charger for electric vehicles

The present invention relates to an insulated bi-directional DC-DC converter charger for an electric vehicle, and in particular, in an electric vehicle having a built-in charger, receives a commercial voltage from home and varies through a power converter, and controls charging power through a phase control method The present invention relates to an isolated bidirectional DC-DC converter charger for an electric vehicle, thereby increasing charging efficiency by suppressing fast dynamic characteristics and reactive components.

The electric vehicle is configured to drive a vehicle through an electric motor by receiving electric power from a vehicle battery without building an internal combustion engine. As described above, in an electric vehicle, a battery is a very important part, and it is necessary to provide a charging device for charging the battery. The types of chargers are largely divided into on-board chargers and off-board chargers.

The on-board charger is a method of charging a battery from a charger mounted in an individual vehicle by receiving 110~220[V] of single-phase power for household use. There are two general control methods: PWM (Pulse Width Modulation) control and Phase-Shift control.

A prior art for a power conversion device for charging an electric vehicle is disclosed in <Patent Document 1> below.

The prior art disclosed in <Patent Document 1> provides a battery and a transformer in which current is charged/discharged.

Built-in, electrically isolated, isolated converter that operates at fixed duty and fixed frequency and outputs the voltage output from the battery at a fixed step-up ratio according to the turns ratio of the transformer, and the input terminal is connected to the isolated converter and supplied from the isolated converter An inverter that converts a DC voltage into an AC voltage and an LCL filter is connected to the output terminal; And a control unit for indirectly controlling the current input and output to the grid side by monitoring the voltage applied to the grid-side inductor of the LCL filter and controlling the output voltage of the inverter. With this configuration, the converter of the bi-directional charger is set so that the output gain is kept constant regardless of the load, so that only the bypass function is performed, so that the mode can be switched only with the control of the inverter without any regulation, which can occur in 2-stage. This suppresses the transient state.

Republic of Korea Patent Registration 10-1714593 (Registration on March 30, 2017) (V2G, bi-directional charger for electric vehicles with V2H function)

However, the prior art as described above is composed of an insulated converter and an inverter using a fixed duty and a fixed frequency, and is a duty variable method using a PWM control method, and thus has low dynamic characteristics and low charging efficiency due to low suppression rate of invalid components. have.

Therefore, the present invention has been proposed to solve various problems occurring in the prior art as described above, in an electric vehicle having a built-in charger, a household commercial voltage is applied and varied through a power converter, and a charger through a phase control method An object of the present invention is to provide an insulated bidirectional DC-DC converter charger for an electric vehicle, which increases the charging efficiency by suppressing the fast dynamic characteristics and reactive components by charging them.

In order to achieve the above object, the insulated bidirectional DC-DC converter charger for an electric vehicle according to the present invention receives commercial AC power, converts it into a variable DC voltage, and controls PFC (Power) to control the power factor of the voltage current. Factor Correction); An insulated transformer electrically insulating the primary and secondary sides; A first single-phase full-bridge inverter interposed between the primary side of the insulated transformer and the PFC; A second single-phase full-bridge inverter disposed between the secondary side of the insulated transformer and the battery; It characterized in that it comprises an inductor for outputting the energy stored and stored between the primary side of the insulating transformer and the first single-phase full-bridge inverter as power.

In the above, the first and second single-phase full-bridge inverters are characterized by being controlled by a phase control method.

In the above, the isolated transformer is characterized by having an N: 1 turns ratio.

In the above, the duty of the first and second single-phase full-bridge inverters is fixed to 0.5, and the flow of power is controlled by using the phase difference of the voltage applied across the inductor.

In the above, when the switching signal of the first single-phase full-bridge inverter precedes the second single-phase full-bridge switching signal, it operates in a charging mode, and the switching signal of the second single-phase full-bridge inverter is the first single-phase full-bridge inverter. It is characterized in that it operates in a discharge mode when it precedes the switching signal.

According to the present invention, in an electric vehicle having a built-in charger, the household commercial voltage is applied and varied through a power converter, and the charging power is controlled by controlling the charging power through a phase control method to increase charging efficiency by suppressing fast dynamic characteristics and invalid components. It has the effect.

1 is a circuit diagram of an insulated bidirectional DC-DC converter charger for an electric vehicle according to the present invention,
2 is an equivalent circuit diagram of a dual full-bridge isolated bi-directional DC-DC converter in the present invention,
3 is a switch signal for each section, voltage and current waveforms across the inductor,
4 is an operation state diagram for each mode.

Hereinafter, an insulated bidirectional DC-DC converter charger for an electric vehicle according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram of an insulated bidirectional DC-DC converter charger for an electric vehicle according to a preferred embodiment of the present invention, receiving commercial AC power, converting it into a variable DC voltage, and controlling a power factor of a PFC (Power Factor) Correction) 10, an insulated transformer 40 electrically insulating the primary and secondary sides, and a first single-phase full-bridge placed between the primary side of the insulated transformer 40 and the PFC 10 ( Full-Bridge) Inverter 20, second single-phase full-bridge inverter 50 placed between the secondary side of the insulated transformer 40 and the battery 60, and the primary side of the insulated transformer 40 And an inductor 30 that outputs energy stored and stored between the first single-phase full-bridge inverters 20 as electric power.

The operation of the insulated bidirectional DC-DC converter charger for an electric vehicle according to the preferred embodiment of the present invention configured as described above will be described in detail as follows.

In the case of the charging method of the battery for an electric vehicle proposed in the present invention, the battery 60 is connected to the DC-link stage through a bi-directional DC-DC converter, and the power transmission direction varies depending on the charge/discharge state. Therefore, the bidirectional DC-DC converter controls variables such as duty or phase angle according to the voltage of the battery to control bidirectional power flow during charging and discharging operations.

The single-phase full-bridge inverter 20, 50 is connected to the primary and secondary sides based on the transformer (isolated transformer) 40. The primary side receives commercial power and is applied to the first single-phase Full_Bridge inverter 20 through power conversion from the existing PFC 10, and the battery 60 is connected to the secondary side. And the AC inductor 30 is configured on the primary side of the transformer 40, and transmits electric power using energy stored in the inductor 30.

The DC voltage converted from the PFC 10 on the primary side varies between 150 and 310 [V], and the voltage on the secondary battery 60 is charged and discharged in the range of 12 to 48 [V]. At this time, the winding ratio of the transformer 40 is N:1.

2 shows an equivalent circuit of a dual full-bridge isolated bidirectional DC-DC converter for explaining the principle of operation of a bidirectional DC-DC converter for charging and discharging a battery. At this time, based on the primary side inductor 30 L, V1 is the output value of the DC voltage converted from the PFC 10 passing through the single-phase full-bridge inverter 20 on the primary side, and nV2 is the battery 60 The voltage and the V2 voltage, which is the output of the secondary-side single-phase full-bridge inverter 50, are converted by the winding ratio of the transformer 40 and applied to the primary side of the transformer 40. At this time, the inductor applied voltage VL was determined as in Equation 1 below based on the current direction of the current iL of the inductor 30.

At this time, the flowing current iL is as shown in [Equation 2] below.

In general, there are mainly two types of control methods of the topology: pulse width modulation (PWM) control and phase-shift control.

In the case of duty control by PWM, it is simple and easy to implement, but the dynamic performance is poor. So, in the present invention, it was controlled by the phase-shift mode, which is a phase control method. At this time, the phase-shift control variable is not the duty value, but θ (phase difference).

The duty of all switches is fixed at 0.5, and the flow of power is controlled using the phase difference between V1 and nV2 applied across the inductor (L). At this time, when the primary side switching signal precedes the secondary side switching signal, it operates in the charging mode, and when the secondary side switching signal precedes the primary side switching signal, it operates in the discharge mode.

In addition, ZCS (Zero Current Switching) operation during switch turn-on can reduce switching losses. The operation principle of Phase-Shift can be explained by dividing it into 8 sections, and the switch signal for each section and the voltage and current waveforms across the inductor are shown in FIG. 3. At this time, D ₁ and D ₂ are internal and external phase difference ratios, respectively. The internal phase difference is defined as the phase shift between the arms of the full bridge, and the external phase shift is defined as the phase difference between the primary and secondary sides of the transformer. In addition, T _hs represents a switching period.

Mode 1(t ₀ -t ₁ ):

Figure 4 (a) shows the operating state of Mode 1.

At time t ₀ , S ₂ is turned off, S ₁ is turned on, and D ₁ starts to conduct. At this time, the secondary current flows through M ₂ and M ₃ and the voltage across the inductor is nV ₂ . This mode ends when Q ₄ is turned on.

During this mode, the current through L is expressed as follows.

Mode 2(t ₁ -t ₂ ):

Figure 4 (b) shows the operating state of Mode 2.

At time t1, since the primary voltage V1 is equal to NV2, S7 is turned OFF and S8 is turned ON. However, when NV2 is higher than V1, S8 is turned OFF and hard switching of S7 is turned OFF. Conversely, when NV2 is lower than V1, S7 is turned OFF, and hard switching of S8 is turned ON. During this mode, the voltage across the inductor is zero. This mode ends when switch S4 is ON. During this mode, the current through L is expressed as follows.

Mode 3(t ₂ -t ₃ ):

Figure 4 (c) shows the operating state of Mode 3.

If the primary voltage V1 is equal to NV2 at t ₂ hours, S4 is turned on. However, if NV2 is higher than V1, S3 is turned OFF and hard switching of S4 is turned ON. Conversely, when NV2 is lower than V1, S4 is turned on and hard switching of S3 is turned off. In this mode, the inductor current flows through S1, S4, S6 and D8. This mode ends when the S6 is switched off. During this mode, the current through L is expressed as follows.

Mode 4(t ₃ -t ₄ ):

Figure 4 (d) shows the operating state of Mode 4.

At time ₃ t, Q1 turns on and Q2 turns off. At this time, a positive current flows through M1 and M4. The current on the primary side flows through S1 and S4. In this mode, the voltage across the inductor is V1-NV2. During this mode, the current through L is expressed as follows.

Mode 5(t ₄ -t ₅ ):

4(e) shows the operation state of Mode 5.

At time t4, S2 turns ON and S1 turns OFF. At this time, the inductor current IL flows through D2 and S4. This mode ends when switch S7 is ON. During this mode, the current through L is expressed as follows.

Mode 6(t ₅ -t ₆ ):

4(f) shows the operation state of Mode 6.

If V1 and NV2 are the same at t ₅ hours, S7 is turned on. However, if NV2 is higher than V1, S7 is turned on and hard switching of S8 is turned off. Conversely, when NV2 is lower than V1, S8 is turned OFF and hard switching of S7 is turned ON. In this mode, the voltage across the inductor is O. During this mode, the current through L is expressed as follows.

Mode 7 (t ₆ -t ₇ ):

Figure 4 (g) shows the operating state of Mode 7.

At time t6, S4 is OFF. At this time, if V1 and NV2 are the same, S3 is ON. However, if NV2 is higher than V1, S4 is turned OFF, and hard switching of S3 is turned ON. Conversely, if NV2 is lower than V1, S3 is turned on and hard switching of S4 is turned off. In this mode, the voltage of the inductor is V1. During this mode, the current through L is expressed as follows.

Mode 8(t ₇ -t ₈ ):

4(h) shows the operation state of Mode 8.

_At time t7, S5 is OFF and S6 is ON. The inductor current IL flows by M2 and M3. During this mode, the current through L is expressed as follows.

The initial current value of the inductor current IL can be obtained as follows.

The present invention provides a converter that can be changed to 12v, 24v and 48v voltage through phase-shift control by receiving commercial power 110[V] or 220[V]. At this time, by improving the power factor through an appropriate phase difference, reactive power can be minimized, thereby maximizing efficiency in power supply.

In addition, if bi-directional PFC is used, electric power can be operated in both directions, so that in the event of an accident such as a power failure, smooth power supply from the vehicle battery will be possible.

The invention made by the present inventors has been described in detail according to the above-described embodiments, but the present invention is not limited to the above-described embodiments and can be changed in various ways without departing from the gist thereof. It is obvious to those who have it.

10: PFC
20: first single-phase full-bridge inverter
30: inductor
40: isolated transformer
50: second single-phase full-bridge inverter
60: battery

Claims (5)

Power Factor Correction (PFC) that receives commercial AC power, converts it into a variable DC voltage, and controls the power factor of the voltage current;
An insulated transformer electrically insulating the primary and secondary sides;
A first single-phase full-bridge inverter interposed between the primary side of the insulated transformer and the PFC;
A second single-phase full-bridge inverter disposed between the secondary side of the insulated transformer and the battery; And
And an inductor outputting energy stored and stored between the primary side of the insulated transformer and the first single-phase full-bridge inverter as electric power.
The method according to claim 1, The first and second single-phase full-bridge inverter is an isolated bi-directional DC-DC converter charger for electric vehicles, characterized in that controlled by a phase control method.
The method according to claim 1, wherein the isolated transformer is N: 1 insulated bidirectional DC-DC converter charger for an electric vehicle, characterized in that it has a turns ratio.
In claim 1, The duty of the first and second single-phase full-bridge inverter is fixed to 0.5, the electric vehicle is characterized in that the flow of power is controlled by using the phase difference of the voltage applied across the inductor Bi-directional DC-DC converter charger.
The method according to claim 1, If the switching signal of the first single-phase full-bridge inverter is ahead of the second single-phase full-bridge switching signal, and operates in a charging mode, the switching signal of the second single-phase full-bridge inverter is the first single-phase Isolated bi-directional DC-DC converter charger for electric vehicles, characterized in that it operates in discharge mode when it precedes the full-bridge switching signal.

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