KR101750808B1 - Hybrid generation system - Google Patents

Abstract

The present invention relates to a hybrid power generation system, and more particularly, to a hybrid power generation system for use in an automobile, which includes a generator that is connected to an engine of an automobile and generates AC power by using engine power, A bidirectional converter for converting electric power to DC, a battery for storing DC power supplied from a bidirectional converter, a rectifier for converting three-phase AC power to DC, a DC / DC converter for boosting the DC power converted from the rectifier, A DC / AC inverter for converting the DC power converted from the DC / DC converter into a commercial AC power and transmitting the converted AC power to the load, and a control unit for controlling an output voltage of the rectifying unit, wherein the controller controls the switches of the bridge converter unit, And a control signal for controlling the switch To a hybrid power generation system.

Description

[0001] HYBRID GENERATION SYSTEM [0002]

The present invention relates to a hybrid power generation system, and more particularly, to a hybrid power generation system capable of supplying power to an external load through a generator connected to an engine and supplying power to an external load through electric power charged in the battery.

Cars are operated using fossil fuels such as refueling oil, diesel fuel, gas fuel, or electricity charged in the battery.

Leisure vehicles are becoming more popular due to recent industrial developments. BACKGROUND ART [0002] Recreational vehicles such as camping cars are developed with a camper with a trailer or a vehicle capable of connecting a trailer.

When camping in an area where no electricity is installed, a separate generator must be attached to the vehicle, mounted on the vehicle, or a high-capacity battery may be used. However, such a generator greatly increases the weight of the vehicle, thereby reducing the fuel consumption of the vehicle and increasing the emission amount of the exhaust gas. And a separate fuel to drive the generator.

The Korean Registered Utility Model No. 20-0356248 (a camper car having a generator storage compartment) is provided with a storage compartment for separately storing a generator in a trailer of a camper car. There is a problem that the weight of the trailer is increased and the space is narrowed because a storage room for storing the generator is separately provided.

In addition, in the case of specially equipped vehicles, fire engines, etc., electric power must be used from the outside, and such vehicles also operate with a separate generator.

Further, in the conventional rectifying part, since the current sensor and the voltage sensor are provided on the generator side and the rectifying part side to receive the three-phase input voltage and the three-phase input current to control the rectification part, voltage and current sensors should be additionally used, Is not high.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide an electric power supply system for a vehicle, which can supply electric power to an external load through a generator connected to an engine, To a hybrid power generation system capable of controlling a rectifier without using a rectifier.

In order to solve the above problems, the present invention provides a hybrid power generation system for use in an automobile, the hybrid power generation system comprising: a generator connected to an engine of the automobile to generate AC power using power of the engine; A bidirectional converter connected to the generator to convert the three-phase AC power supplied from the generator to DC; A battery for storing DC power supplied from the bidirectional converter; A rectifier connected to the generator for converting the three-phase AC power into DC; A DC / DC converter for boosting the DC power converted by the rectifier; A DC / AC inverter converting the DC power converted by the DC / DC converter into a commercial AC power and transmitting the converted AC power to the load; And a control unit for controlling an output voltage of the rectifying unit, wherein the rectifying unit includes: a bridge converter unit having six switches connected to an input unit to which three-phase voltage and current are input from the power generating unit, And a Z-source network in which two inductors and two capacitors have Z-impedance in an output portion output to the converter, and a DC inductor connected in common to the first inductor and the first capacitor are formed, And the control unit supplies a control signal for controlling the switches of the bridge converter unit and the direct current switch.

Wherein the control unit calculates the remaining phase currents through at least two phase currents input from the generator, and calculates an input voltage drop to output an estimated input voltage of three phases through the three phase currents, the DC voltage output from the rectifying unit, government; A DQ converting unit for performing DQ conversion of the estimated input voltage of the three phases and the estimated input voltage of the three phases through the three phase currents; A phase angle controller for controlling a phase angle through a voltage output from the D / Q converter; And a space vector modulator for controlling the turn-on and turn-off times of the plurality of switches and the dc switch of the bridge converter through the estimated phase angle output from the phase angle controller and the arm shortfall index.

(여기서, E_a,b,c ^{est 는} a, b, c상의 추정된 입력 전압, Ea,b,c는 a, b, c상의 입력 상전압, D_o는 암단락 지수임) 로 계산되어 상기 추정된 입력 전압을 각 상별로 출력할 수 있다.The input voltage estimating unit

(Wherein, E _{a, b, c} ^{est is} a, b, c on the estimated input voltage, Ea, b, c are a, b, c phase input voltage, D _o on _the cancer being shunt index) And output the estimated input voltage for each phase.

The control unit may further include a PI controller for generating the arm short-circuit index through the DC voltage output from the rectifier.

The DC / DC converter can supply the boosted power to the load.

Wherein the hybrid power generation system supplies power from the battery to the bidirectional converter and generates power from the power supplied from the bidirectional converter in the generator when the power consumption of the load is larger than the amount of power produced through the power of the engine .

The hybrid power generation system may supply power to the alternating current load or the direct current load from the battery when the engine is in a stopped state.

The hybrid power generation system according to the embodiment of the present invention can charge the battery or supply electric power to the load by the engine power. At this time, the hybrid power generation system according to the embodiment of the present invention can supply power to the load through the electric power charged in the battery without operating the engine of the vehicle.

In addition, the hybrid power generation system according to the embodiment of the present invention can supply power to the load by using both the engine and the power of the battery when the load requires a large amount of power.

The hybrid power generation system according to an embodiment of the present invention can be used in a rescue vehicle such as a fire engine, a laker car, or a leisure car.

The hybrid power generation system according to an embodiment of the present invention receives a current of two phases without receiving a three-phase voltage supplied from a generator, estimates a three-phase voltage, and controls a switch of a rectifier through an estimated voltage, Power generation system can be provided.

1 is a block diagram showing a hybrid power generation system according to an embodiment of the present invention;
2 is a block diagram showing the rectifying part and the control part shown in Fig.
3 is a block diagram showing a rectifying section of the hybrid power generation system shown in Figs. 1 and 2. Fig.
FIG. 4 is a block diagram showing an example of the input voltage estimating unit shown in FIG. 2. FIG.
FIG. 5 is a block diagram showing an example of the phase angle control unit shown in FIG. 2. FIG.
6 is a waveform diagram showing a phase angle estimation waveform of the phase angle control unit shown in Fig. 5; Fig.
FIG. 7 is a waveform diagram showing a switching pattern of the space vector convergence unit shown in FIG. 2; FIG.
8 is a waveform chart comparing an estimated input AC voltage and a measured AC voltage in a steady state using a PSIM simulator.
Fig. 9 is an enlarged waveform diagram of the estimated input AC voltage and the measured AC voltage of Fig. 8; Fig.
10 is a waveform diagram showing the estimated three-phase input phase voltage waveform and phase angle.
11 and 12 are waveforms showing the transient response of the estimated input phase voltage waveform when the input phase voltage changes, and magnified waveforms obtained by enlarging the waveforms.
13 is a waveform chart showing a result of a simulation for a unit input power factor control and a rectifier output stage voltage control.
FIG. 14 is a waveform chart showing output stage reference voltage fluctuation dynamic characteristics of a conventional PWM rectifier, and FIG. 15 is a waveform chart showing output stage reference voltage fluctuation dynamic characteristics of a rectifying section according to an embodiment of the present invention.
16 is a waveform diagram showing FFT analysis results on the estimated input voltage, the measured input voltage, and the input current.

Hereinafter, the description of the present invention with reference to the drawings is not limited to a specific embodiment, and various transformations can be applied and various embodiments can be made. It is to be understood that the following description covers all changes, equivalents, and alternatives falling within the spirit and scope of the present invention.

In the following description, the terms first, second, and the like are used to describe various components and are not limited to their own meaning, and are used only for the purpose of distinguishing one component from another component.

Like reference numerals used throughout the specification denote like elements.

As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. It is also to be understood that the terms " comprising, "" comprising, "or" having ", and the like are intended to designate the presence of stated features, integers, And should not be construed to preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 16 attached hereto.

FIG. 1 is a block diagram schematically showing a hybrid power generation system according to an embodiment of the present invention. FIG. 2 is a block diagram specifically showing a rectifier and a control unit shown in FIG. 1, Fig. 6 is a block diagram showing an example of a rectifying section shown in Fig.

1 to 3, a hybrid power generation system according to the present invention includes an engine 10, a generator 20, a bidirectional converter 30, a battery 40, a power conversion unit 100, and a control unit 200 .

Specifically, the generator 20 can receive the power transmitted from the engine 10 of the automobile and produce AC power. Also, the generator 20 may receive the power supplied from the battery 40 to produce AC power.

The generator 20 may be an induction generator or the like. The generator 20 generates and outputs AC power of three phases. At this time, the generator 20 has a weight of about 30 Kg so that the generator 20 can be mounted on an automobile. The generator 20 may include a generator driver (not shown) for controlling the generator 20.

The battery 40 is installed inside the vehicle for electric power charging. The battery 40 may be selected in capacity depending on the use of the vehicle.

The power converter 100 includes circuit devices and may include a rectifier 110, a DC / DC converter 120, and a DC / AC inverter 130.

The bidirectional converter 30 is installed between the generator 20 and the battery 40 to convert AC power supplied from the generator 20 into DC power and provide the battery 40 with the AC power. The bidirectional converter 30 converts the DC power supplied from the battery 40 to AC power and supplies the AC power to the generator 20.

If the amount of power used in the load 60 can not be supplied through the engine 10, it is possible to supply power from the battery 40 to the bidirectional converter 30, thereby providing additional power to the generator 20 . In addition, when the engine 10 is stopped, power can be supplied to the load 60 by power supplied from the battery 40.

Here, when power is supplied from the battery 40, power may be supplied from the battery 40 to the bidirectional converter 30 using a separate control device and switches.

The bi-directional converter 30 has a plurality of power switch elements, and can be implemented as an electric circuit in which an inductor and a capacitor are connected in series and in parallel.

The rectifying unit 110 converts the three-phase alternating-current power output from the generator 20 into single-phase direct-current power. 3, a rectifier 110 according to an embodiment of the present invention can be used with a three-phase Z-source PWM rectifier.

As shown in FIG. 3, the rectifying section 110 is coupled to the bridge converter section 112 and the Z-source network 114.

The bridge converter unit 112 switches on / off the six internal switches according to a switch signal input from the controller 200, and rectifies the alternating voltage into a DC voltage. The Z-source network 114 boosts or downstages the voltage output from the bridge converter unit 112 and provides the voltage to the DC / DC converter 120. At this time, the Z-source network 114 may be provided with a dc switch 116 connected in series to the dc / dc converter 120. The Z-source network 114 is formed such that two inductors L1 and L2 and two capacitors C1 and C2 have Z-impedances at the output, and the first inductor L1 and the first capacitor C1 And a DC switch 116 connected in common to the DC switch 116 is formed.

The a-phase voltage equation of the bridge converter unit 112 can be calculated as shown in Equation (1). Where E _a is the input phase voltage, i _a is the phase current, and v _a is the voltage across each phase between the neutral points of the system. Further, L _n and R _{n denote} an AC-side inductor and a resistor.

From Equation (1), the phase voltage of the a phase between the neutral points can be calculated by Equation (2).

In Equation (2), S _a , S _b , and S _c are switching states of respective phases, and are 1 when the switch of each phase is ON and 0 when OFF.

Unlike the conventional PWM rectifier, the switching pattern in the rectifying unit 110 is composed of nine switching patterns including six effective vectors, two zero vectors, and an added zero vector. The added zero vector occurs when the dc switch 116 is in the off state.

Here, the operation can be classified into a non-shoot-through state (active state) mode and a shoot-through state mode. The DC stage switch 116 is turned on during the specific arm shorting time (TR) of the two switches located in the same arm, and during this period, the Z-source rectifier 110 operates as a voltage-type rectifier. At this time, the input DC voltage V _in and the output DC voltage V _dc applied to the Z-source network 114 are the same.

During the time (T _D ) during which the two switches located in the same arm are short-circuited to each other, the DC switch 116 is turned off. In this case, the input DC voltage V _in applied to the Z-source network 114 is applied at a voltage higher than the output DC voltage V _dc .

The inductor average voltage (V _L ) and the average voltage V _C applied to the capacitor in the operation mode are expressed by Equations (3) and (4).

In the arm short state in which the current loop is formed through the diode formed in the bridge converter unit 112 and the capacitor of the Z-source network 114, the Z-source network 114 can step up or down the output voltage, 5 and (6).

Unlike the conventional PWM rectifier, the maximum value E _pk of the rectified voltage 110 of the rectifying unit 110 is expressed by Equation 5, and the output voltage V _dc , the voltage / current conversion ratio B, the modulation index M, D _o ) is defined. Equation (6) represents the voltage / current ratio (B) and the voltage / gain ratio (G). Where TS is the switching period of the six switches in the bridge converter unit 112 and T7 is the switching time of the dc switch 116. [

Steady-state modeling of the rectifying part 110 can be expressed as Equation (7).

The modeling equation can be largely composed of a Z-source impedance network (L1 = L2, C1 = C2), phase and phase currents, and DC-link capacitance. Where L _n and R _n are the AC side inductor and resistor, C _out is the connection capacitor of the DC / DC converter 120, L and C are the inductor and capacitor elements of the Z- i _{a, b, c} , and v _{a, b, and c} represent line-to-line current and line-to-line voltage, respectively. V _Cout is a DC voltage applied to the DC / DC converter 120, and R _Load is a load resistance. v _c , i _L are the capacitor voltage and the inductor voltage applied to the Z-source network 114. Finally, d _{a, b, and c} are the duty cycles of each line voltage, and d _ST is the duty ratio at the shoot-through state.

The voltage gain can be varied according to the modulation index. In the conventional PWM rectifier, although the voltage gain is linearly increased in proportion to the modulation index increase, the rectifying section 110 of the present invention can control the voltage gain exponentially according to the modulation index.

This is because the short-circuit time of the L-C combined Z-source network 114 can be controlled to utilize both the boosting and down-converting characteristics. The above characteristics can be regarded as control variable characteristics for the modulation index variation of the rectifying unit 110 of the present invention, and can be expressed by Equations (8) and (9).

The DC / DC converter 120 boosts the single-phase DC power output from the rectifier 110 and outputs it. DC / DC converter 120 outputs a voltage boosted to about 310 [V].

 The DC / DC converter 120 uses an insulated converter. The DC / DC converter 120 uses a circuit in which elements such as a transformer, a plurality of switches, an inductor, and a capacitor are connected.

The DC / DC converter 120 may supply DC power to the DC / AC inverter 130 or may supply power to the direct load 60 when the load 60 is a DC load.

The DC / AC inverter 130 converts the voltage output from the DC / DC converter 120 into commercial AC power and supplies it to the load 60. The DC / AC inverter 130 is implemented as a single-phase inverter circuit. The DC / AC inverter 130 outputs a voltage of 220 [V], 60 Hz. Here, the DC / AC inverter 130 may include a plurality of switch elements, an inductor, and a capacitor.

The control unit 200 outputs a signal for controlling ON / OFF of the switching elements of the rectifying unit 110. At this time, the controller 200 can adjust the level of the output voltage without varying the input voltage of the rectifier 110 using the phase currents input from the generator 20 and the DC voltage output from the rectifier 110.

The controller 200 can adjust the output voltage level of the rectifier 110 by estimating the input voltage and the current of the rectifier 110 using the output DC voltage and DC current of the rectifier 110.

The control unit 200 may include an input voltage estimation unit 210, a DQ conversion unit 240, a phase angle control unit 250, a PI control unit 200, and a space vector modulation unit 220.

Specifically, the input voltage estimating unit 210 receives input AC currents of at least two phases input from the generator 20 to the rectifying unit 110, and calculates the remaining one current from the currents of the two phases. Next, the input AC voltage of each phase can be estimated by using the DC voltage output from the rectifying unit 110 and Equations (1) and (2).

Equation (10) is a formula for estimating the voltage of a-phase estimated using Equations (1) and (2) and DC voltage. At this time, S _k = S _a + S _b + S _c .

4 is a block diagram schematically showing an example of the input voltage estimating unit.

The input voltage estimating unit shown in FIG. 4 calculates an AC voltage estimated using the inputted AC current. In this case, E _{a, b and c} ^est are the estimated input voltage values, i _{a, b and c} are the measured input current values, and E _dq ^est is the DQ conversion value of the estimated input voltage. V _dc and V _dc ^* are the output stage measurements and setpoint D ₀ is the cancer short-cut index associated with the cancer shortage described above. [theta] ^est is an estimated input voltage and an estimated phase angle generated through the phase angle controller 250. [

The input voltage estimator 210 shown in FIG. 4 generates the amplitude command value E ^* _a of the input voltage from the detected phase current, the output DC voltage, and the switching function. Voltage command E ^* _a generates the input voltage E estimate _a ^est multiplied with cancer shunt index (D _o) of the rectifying section 110 calculated from the equation (11).

In order to output a stable voltage in the rectifying unit 110, since a value of E _d ^est must be estimated to be 0 as shown in Equation 13, the PI control unit 200 performs PI control by considering the D axis as an error component of phase . As shown in FIGS. 5 and 6, the phase angle controller 250 calculates the phase angle command value? ^* And outputs the phase angle? ^Est .

At this time, the phase angles are estimated from Equations (14) and (15), and the estimated phase angle (? ^Est ) information is used for coordinate conversion.

The spatial vector modulator 220 has a low modulation rate and a low harmonic content and is used in a three-phase power conversion system. The spatial vector modulator 220 of the present invention is configured such that the size (max V _R ) of V _R having the maximum size is made equal to the modulation index 1 as shown in FIG. 7, and the V _R and the arm short Construct a V _R having the maximum magnitude with the vector V _D. At this time, it is preferable that the zero vector always has the minimum size.

The spatial vector modulator 220 detects the estimated input phase voltage and the output voltage to control the output voltage and controls the switching application time and the output voltage through the DQ conversion unit 240 and the PI control unit 200 have.

The reference vector application time of the spatial vector modulator 220 may be calculated as shown in Equations (17) to (20).

In the above Equations 17 to 19, M is a sector number, and a is a phase angle.

At this time, the switching pattern by the space vector modulator 220 is as shown in Table 1.

8 to 16 are diagrams showing simulation waveforms of respective components included in a control unit for controlling the three-phase Z-source pulse width modulation rectifier according to the embodiment of the present invention.

In order to perform the simulation, the parameter values were set as shown in Table 2, and the result was predicted by configuring the PSIM system.

At this time, the PSIM system is implemented as a system having the same configuration as the control unit 200, and has no input AC voltage sensor, and is controlled by only the input AC current sensor and DC voltage sensor.

Under the simulation conditions, the output DC voltage reference value changes from 150 [V] to 110 [V], 110 [V] to 70 [V], and the output AC voltage swings and transient response characteristics and the estimated input AC voltage waveform The performance of the controller 200 was evaluated by measuring FFT (Fast Fourier Transform) and efficiency.

8 is a waveform diagram showing an input voltage estimated by the input voltage estimating unit and a measured input voltage together with a phase current.

As shown in FIG. 8, when the input phase voltage estimated in the steady state is expressed by the graphs obtained by the equations (11) to (13) using only the input current and DC voltage of the two phases, Compared with the detected waveform, it shows the same form.

9 is an enlarged view of the estimated input AC voltage and the detected voltage.

As shown in FIG. 9, it can be confirmed that the estimated input AC voltage matches the amplitude and phase of the detected voltage.

FIG. 10 is a waveform diagram showing the estimated three-phase input phase voltage waveform and phase angle. As shown in FIG. 10, it can be confirmed that a certain frequency is followed through the phase angle controller.

Figs. 11 and 12 are waveforms showing the transient response of the estimated input phase voltage waveform when the input phase voltage changes and enlarged waveforms showing the transient response. Fig. 13 shows the waveforms of the input phase voltage of 0.5 [s] V] to 120 [V], it can be confirmed that the estimated input phase voltage is the same as the measured input phase voltage. Also, as shown in FIG. 11, it can be seen that the estimated input voltage maintains a constant frequency without changing the waveform and phase angle of the measured input voltage even in a period where the input voltage fluctuates.

13 is a waveform chart showing a simulation result for a case where the unit input power factor control and the output stage voltage control are performed.

It can be confirmed that the estimated input AC phase voltage and the measured input AC current waveform of FIG. 13 are in phase with each other. Also, when the reference value of the voltage output to the DC / DC converter is constantly controlled to 150 [V], it can be confirmed that the ripple is not generated in the output side DC voltage.

FIG. 14 is a waveform chart showing the output stage reference voltage fluctuation dynamic characteristic of the conventional PWM rectifier, and FIG. 15 is a waveform chart showing the output stage reference voltage fluctuation dynamic characteristic of the rectifying section according to the embodiment of the present invention.

Referring to FIGS. 14 and 15, it can be seen that the conventional PWM rectifier controls the output voltage only by a voltage higher than the input voltage with respect to the output DC voltage reference value of 150 [V] 110 [V] 70 [V]. This is because the circuit connected to the switch-on operation in the bridge circuit always has a characteristic that the line-to-line voltage is applied, so that the output reference voltage of the rectifier can not be controlled below the input voltage. Therefore, the rectifier of the present invention is used to control the output DC voltage at a voltage lower than the input voltage. 15, the 3-phase Z-source PWM rectifier used in the rectifying unit 110 of the present invention is designed to output the output DC voltage boosted to be higher than the input voltage even when abrupt control is performed at 150 [V] 110 [V] Or to obtain a reduced voltage.

16 is a waveform diagram showing an FFT analysis result on the estimated input voltage, the measured input voltage, and the input current.

As shown in FIG. 16, the input voltage, the measured input voltage, and the input current estimated from the FFT analysis are all sinusoidal waves because the harmonic components except for the fundamental wave component of 60 [Hz] are insignificant have.

10: Engine
20: generator
30: Bi-directional converter
40: Battery
60; Load
100: power converter
110: rectification part
112: bridge converter section
114: Z-source network
116: DC Switch
120: DC / DC converter
130: DC / AC inverter
200:
210: Input voltage estimation unit
220: Space vector modulating unit
230: PI control unit
240: DQ conversion unit
250: Phase angle controller

Claims (7)

In a hybrid power generation system for use in a motor vehicle,
A generator connected to the engine of the automobile to produce AC power using the power of the engine;
A bidirectional converter connected to the generator to convert the three-phase AC power supplied from the generator to DC;
A battery for storing DC power supplied from the bidirectional converter;
A rectifier connected to the generator for converting the three-phase AC power into DC;
A DC / DC converter for boosting the DC power converted by the rectifier;
A DC / AC inverter converting the DC power converted by the DC / DC converter into a commercial AC power and transmitting the converted AC power to the load; And
And a control unit for controlling an output voltage of the rectifying unit,
The rectifying part
A bridge converter unit in which six switches are connected in a bridge form to an input unit to which three-phase voltage and current are input from the generator, and two inductors and two capacitors in the output unit output to the DC / DC converter convert Z- And a Z-source network formed with a DC inductor connected in common to the first inductor and the first capacitor,
The control unit
A control signal for controlling the switches of the bridge converter unit and the direct current switch,
The control unit
An input voltage estimator for calculating a remaining phase current through at least two phase currents input from the generator and outputting an estimated input voltage of three phases through the three-phase current, the DC voltage output from the rectifier, and the arm short circuit index;
A DQ conversion unit for performing DQ conversion of the estimated input voltage of the three phases and the estimated input voltage of the three phases through the three-phase current;
A phase angle controller for controlling the phase angle through the voltage output from the DQ converter;
A space vector modulator for controlling the turn-on and turn-off times of the plurality of switches and the dc switch of the bridge converter through the estimated phase angle output from the phase angle controller and the arm shortfall index; And
And a PI controller for generating the arm short-circuit index via a DC voltage output from the rectifier,
The input voltage estimating unit

(Wherein, E _{a, b, c} ^{est is} a, b, c on the estimated input voltage, Ea, b, c are a, b, c phase input voltage, D _o on _the cancer being shunt index)
And outputs the estimated input voltage for each phase,
The bidirectional converter is provided between the generator and the battery separately from the rectifying unit and the DC / DC converter. The bidirectional converter converts the three-phase AC power supplied from the generator to DC power to provide the battery or DC power supplied from the battery. Converted into alternating-current power and provided to the generator,
If the amount of power used by the load is greater than the amount of power produced through the power of the engine, power is supplied from the battery to the bidirectional converter to generate power from the bidirectional converter in the generator,
Wherein the DC / DC converter supplies the boosted power to the load,
Supplying power to the load from the battery when the engine is in a stopped state,
Wherein the DC / DC converter is an insulated converter, and is a circuit in which a transformer, a plurality of switches, an inductor, and a capacitor are connected.
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