KR101583956B1 - Control method for DC-DC converter - Google Patents

Abstract

The present invention relates to a control method for a DC-DC converter and the main purpose of the present invention is to provide a control method for operating a DC-DC converter having n buck-boost converter sub-circuits paralleled for DC-DC converting between power sources or between the power source and a load, in the maximum efficiency. To attain the purpose, for a control method of a parallel type DC converter which has n sub circuit parts converting DC-DC composed with parallel connection, and which output a current on the basis of a current demand value, by the operation of the sub circuit part, disclosed is the control method comprising: a) a step of seeking current distribution values which are equally distributed to the sub circuit part on the basis of the number of sub circuit parts used, from the current demand value; b) a step of seeking a predetermined efficiency value corresponding to each current distribution value, from the current distribution value on the basis of the number of sub circuit parts used; c) a step of determining the current distribution values and the number of sub circuit parts used to represent the maximum efficiency value by comparing efficiency values corresponding to each current distribution value; and d) a step of selecting the determined number of sub circuit parts used and controlling the operation of the sub circuit part in order to output the current of the determined current distribution values.

Description

[0001] The present invention relates to a control method for a DC-DC converter,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for DC converters, and more particularly to a control method for operating DC converters having a parallel structure at an optimum efficiency point.

Today, internal combustion engine vehicles using fossil fuels such as gasoline and diesel have various problems such as environmental pollution caused by exhaust gas, global warming caused by carbon dioxide, and generation of respiratory diseases caused by ozone generation.

Accordingly, there is a demand for an electric vehicle (EV) that drives an electric motor, that is, an electric motor, a hybrid electric vehicle (HEV) that runs on an engine and an electric motor, Eco-friendly vehicles such as a fuel cell electric vehicle (FCEV) that drives an electric motor by electric power have been developed.

As well known, an eco-friendly automobile has a regenerative braking (RB) system that recovers braking and inertia energy through electric motor power generation when the vehicle is coasting due to braking or inertia, Is performed.

In an eco-friendly automobile, energy can be recovered through an electric motor (a traction motor) during braking or traveling on a bumpy road, thereby recharging the battery and reusing the electric motor to drive the vehicle.

On the other hand, a polymer electrolyte membrane fuel cell mounted on a fuel cell vehicle using hydrogen as a fuel operates at a high efficiency. However, when only a fuel cell is used as a power source of a vehicle, There is a problem that the performance is deteriorated in an operation region where the efficiency of the battery is low.

In addition, when a sudden load is applied to the vehicle, the output voltage of the fuel cell, which generates electricity by a chemical reaction, may instantaneously drop and fail to supply sufficient power to the driving motor for driving the vehicle, resulting in deterioration of vehicle performance.

In addition, since the fuel cell has a unidirectional output characteristic, it is not possible to recover the energy drawn from the drive motor at the time of braking the vehicle, thereby reducing the efficiency of the vehicle system.

In order to overcome the above problems, an energy storage device such as a high voltage battery or a super capacitor (supercap) capable of charge / discharge as a separate auxiliary power source for driving a drive motor and a high voltage component, in addition to a fuel cell, Fuel cell hybrid systems that are connected in parallel with a battery are being studied.

When an auxiliary power source capable of charging / discharging other than the fuel cell is mounted, the vehicle can be driven by the power of the auxiliary power source if necessary (the EV mode in which the driving motor is driven only by the output of the auxiliary power source is possible) It is possible to recover energy (regenerative braking) as an auxiliary power source through power generation.

As described above, in a fuel cell hybrid vehicle in which two energy sources (a power source), that is, a fuel cell and a battery are mounted together, a bidirectional high voltage DC converter (Bi- direction High Voltage DC-DC Converter, BHDC) in front of the battery or in front of the fuel cell.

FIG. 1 is a diagram illustrating a configuration of a power net of a fuel cell hybrid vehicle, which includes a fuel cell 1 as a main power source, a high voltage battery 2 as an auxiliary power source, a drive motor 7 for driving the vehicle, A motor control unit (MCU) 6 including an inverter 5 for converting the DC power of the fuel cell 1 or the battery 2 to three-phase AC power for driving the motor .

As shown in the figure, in the power net configuration of the fuel cell hybrid vehicle, the high-voltage battery 2 which is the power storage unit and is the power source is connected to the DC-link stage 4 through the bidirectional high voltage DC converter 3, In parallel.

The DC-DC converter 3 supplies the electric power of the battery 2 to the inverter 5 at the time of vehicle start, and receives the regenerative energy via the drive motor 7 at the time of the motor-generator 3 to charge the battery 2, When the state of charge (SOC) is low, the power of the fuel cell 1 is supplied and the battery 2 is charged.

In order to reduce the current level, the DC converter may be configured by connecting a plurality of (n) small converters (converter sub circuit portions described below) in parallel. The DC converters may distribute power arithmetically .

FIG. 2 is a diagram illustrating the configuration of a DC converter connected between two power sources, that is, a fuel cell, which is the two power sources of a fuel cell hybrid vehicle, and a battery. As illustrated, the DC converters 3 are connected in parallel A converter controller 3b for outputting a PWM control signal to the switching elements Q1 and Q2 of each converter sub circuit portion 3a and a converter controller 3b for outputting a PWM control signal to the converter elements Q1 and Q2 of the converter sub- And a gate driver 3c for applying a gate driving signal in accordance with the PWM control signal of the inverter 3b.

The illustrated DC converter 3 has a configuration in which three converter sub circuit portions 3a are connected in parallel so as to convert a DC input voltage to a DC output voltage of another level. Each converter sub circuit portion 3a has two And a half bridge structure having switching elements Q1 and Q2.

The DC converter 3 illustrated in FIG. 2 exemplifies a configuration in which three sub-circuit portions 3a of three phases (U, V, and W) are connected in parallel, but the number of sub-circuit portions is n It is expandable.

In the DC converter 3, voltage / current control is performed by the converter controller 3b in accordance with an operation command of the host controller 10. The voltage controller 3b includes three (n) buck-boost converter sub circuit portions 3a (1 / n) with respect to the current demand value (current command) of the host controller 10. [

However, in the conventional control method in which a current distribution of 1 / n is applied to all the sub-circuit portions with respect to the current demand value as described above, the region using the high current is advantageous in terms of efficiency, I have a problem to show.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a DC-DC converter for a DC- And it is an object of the present invention to provide a control method that allows a DC converter having a connected configuration to be operated at an optimum efficiency point.

In order to achieve the above object, according to an embodiment of the present invention, there is provided a parallel-type power supply device in which n sub-circuit parts in which DC-DC power conversion is performed are connected in parallel and a current output according to a current demand value is performed by operation of a sub- A) calculating a current distribution value to be uniformly distributed to the sub circuit section according to the number of sub circuit sections from the current demand value; b) obtaining a predetermined efficiency value corresponding to each current distribution value from a current distribution value according to the number of uses of the sub circuit section; c) comparing the efficiency values corresponding to the respective current distribution values to determine the number of uses and the current distribution value of the sub circuit section indicating the maximum efficiency value; And d) selecting the determined number of sub-circuit portions and controlling operation of each selected sub-circuit portion so that current output of the determined current distribution value is made. .

In a preferred embodiment, the current vs. current value defining the corresponding efficiency value according to the current value in the step b). Efficiency table information can be used.

In addition, in the process of selecting the sub circuit portion in the step d), the current distribution value of one used current divider value is obtained when the number of the sub circuit portions is one, Can be set to select as many sub-circuit portions as the number of used sub-circuit portions.

In addition, in the process of controlling the operation of each selected sub-circuit portion in the step d), the operation cumulative current amount of each of the sub-circuit portions to be operated is configured to be accumulated as a value obtained by accumulating the current cumulative value x the operation time ' .

If the maximum efficiency value, the number of sub-circuit units to be used, and the current distribution value are determined, the difference between the determined maximum efficiency value and the maximum efficiency value of the previous cycle is compared with a predetermined set value, May be set to meet the output of the current demand value with the operation of the sub circuit portion that was selected and operated in the previous cycle.

The control circuit controls the sub-circuit sections of the sub-circuit sections selected and operated in the previous cycle so that the current output value of the current demand value is uniformly distributed. The difference between the current maximum efficiency value and the maximum efficiency value of the previous cycle is greater than the set value And if it is larger, it is preferable to perform the step d) according to the number of used sub-circuit portions and the current distribution value determined in the step c).

Thus, according to the control method of the direct current converter according to the present invention, the current distribution and the output amount of each sub circuit section are adjusted according to the current efficiency value so that each of the buck-boost converter sub circuit sections can be operated at the optimum efficiency point, DC converter can be operated at an optimum efficiency point, and the operation efficiency is improved through optimal control of the DC converter.

In addition, the control method of the DC / DC converter according to the present invention can be applied to an environmentally friendly automobile such as a bi-directional high voltage DC converter (BHDC) interposed between a fuel cell and a battery (power storage device and power storage device) It is possible to improve the fuel efficiency of the vehicle by optimally controlling the dc converter considering the efficiency point.

In addition, since the sub-circuit portion to be used for power conversion is selected in accordance with the amount of cumulative operating current of each converter sub-circuit portion, the sub-circuit portion in the DC-DC converter can be used equally and the current distribution and the amount of power can be uniformly distributed to the sub- . As a result, the operating time and the current amount of each sub-circuit portion and the power module (including the switching device) included therein can be evenly limited, so that the durability of the sub-circuit portion and the power module can be increased.

In addition, in the optimal efficiency control algorithm according to the present invention, efficiency hysteresis is applied to limit the operation mode change according to the efficiency difference, thereby reducing switching loss due to frequent changes in the number of sub circuit portions and efficiency deterioration due to current variations .

In addition, the control method of the DC / DC converter according to the present invention is a control method for controlling the current flowing from the battery to the load side of the vehicle, as well as controlling and converting the current flowing from the vehicle to the battery (regeneration) (Charging) of the battery.

In addition, it can be widely used not only in a three-parallel type bidirectional high-voltage DC converter of a fuel cell hybrid vehicle but also in a DC converter of a hybrid car or a pure electric car using an n parallel sub-circuit scheme.

Further, the present invention can be applied not only to a high-voltage DC converter but also to a low-voltage DC-DC converter (LDC) having n parallel sub-circuits.

1 is a diagram illustrating a power net configuration of a general fuel cell hybrid vehicle.
2 is a diagram illustrating a configuration of a general DC converter connected to two power sources.
3 is a flowchart showing a control method according to an embodiment of the present invention.
4 is a flowchart showing a control method in which the efficient hysteresis and the current amount even distribution control are applied as an embodiment of the present invention.
FIG. 5 is a graph showing an efficiency characteristic according to a current of the DC-DC converter and an arbitrary required current of the vehicle according to time.
6 is a view showing an efficiency curve according to a control method.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains.

The present invention relates to a DC converter having a configuration in which n buck-boost converter sub circuit portions are connected in parallel for DC-DC power conversion between a power source and a power source or between a power source and a load, And to provide a control method for enabling the control device to be controlled.

To this end, in the present invention, a method of adjusting the current distribution and the output amount of each sub circuit portion according to the current efficiency value is applied so that each of the buck-boost converter sub circuit portions can be operated at the optimum efficiency point.

The control method of the present invention can be applied to a control method of a bidirectional high voltage DC converter (BHDC) interposed between a fuel cell, a battery, and a drive motor (specifically, an inverter) in an environmentally friendly vehicle, particularly a fuel cell hybrid vehicle.

In this specification, a three-parallel type bidirectional high voltage DC converting apparatus of a fuel cell hybrid vehicle will be described as an example, and a configuration of a three-parallel bidirectional high voltage DC converting apparatus will be described with reference to FIG.

FIG. 3 is a flowchart showing a control method according to an embodiment of the present invention, in which a converter controller (3b in FIG. 2) receives a control output value of a direct current converter from an upper controller (10 in FIG. 2) (Step S11), and determines the number of sub-circuit portions 3a used for indicating the maximum efficiency value from the current demand value.

Here, the host controller 10 may be a vehicle controller (e.g., FCEV Controller) communicably connected to the converter controller 3b through CAN communication or the like.

To be more specific, when only one buck-boost converter sub circuit section (hereinafter abbreviated as "sub circuit section") is operated when the current demand value of the host controller is i *, it is distributed to one sub circuit section, The amount of current output, that is, the current distribution value i1, which the one sub-circuit portion should take charge of and output from, is the current demand value i * of the host controller.

When the two sub circuit portions are operated, current distribution is equalized in the two sub circuit portions. The current distribution value i2 to be distributed to each of the two sub circuit portions to be operated is 1 / 2, i * / 2.

When the three sub-circuit portions are operated, the current distribution is distributed to the three sub-circuit portions. The current distribution value i3 to be distributed to each of the three sub-circuit portions to be operated is 1 / 3, i * / 3.

Therefore, the current distribution values i1, i2, and i3 that are to be uniformly distributed to the individual sub-circuit portions are obtained according to the number of use (operation number) of the sub-circuit portion (S12).

(N-1) = i * / 4, i5 = i * / 5, ..., i (n-1) as well as i1, i2 and i3 in a DC converter in which n sub- (n is the natural number) of the individual sub-circuit portions according to various use count values of the sub-circuit portions by the method of (i) / (n-1), in = i * / n.

Then, efficiency values eff1 to eff3 corresponding to the current division values according to the current efficiency values, that is, the number of used sub-circuit portions, are determined from the respective current distribution values according to the number of used sub-circuit portions (S13).

In this case, the currents stored in the converter controller after experimentally obtained through the preceding test are compared. Efficiency table information can be used.

Here, The efficiency table information is table information that defines an efficiency value corresponding to each current value. The current and efficiency graphs are digitized and specified in a lookup table. The efficiency table information is defined as a value corresponding to each current distribution value (i1 to i3) So that the efficiency values eff1 to eff3 can be obtained.

If the efficiency value corresponding to i1 is represented as eff1, the efficiency value corresponding to i2 is referred to as eff2, and the efficiency value corresponding to i3 is referred to as eff3, efficiency values corresponding to the respective current distribution values are compared with each other (S14 ', S14 " (S15 ', S15 ", S15 "").

In this process, the number of use and the current distribution value of the sub-circuit portion indicating the maximum efficiency (eff) are determined, and the converter controller controls the operation of the sub-circuit portion according to the number of use and current distribution values i1 to i3 .

That is, the sub-circuit portions are operated as many as the number of uses that indicate the maximum efficiency, and the output of the sub-circuit portion is controlled so that the output current of each sub-circuit portion becomes the current distribution values i1 to i3 according to the number of uses of the sub-circuit portion.

Thus, only the selected number of sub-circuit portions representing the maximum efficiency value (optimum efficiency) in the entire DC-DC converter is used to satisfy the current value output requested by the host controller.

Of course, the output control of each sub-circuit part outputs the PWM control signal for the individual sub-circuit part so that the current output corresponding to the current distribution value can be made, and the gate driver outputs the PWM control signal to the switching element And outputs a gate driving signal (on / off switching signal).

Thus, in the present invention, the uniform current distribution values (i1 to in) according to the various use number values of the sub circuit section are obtained from the current demand values of the host controller, and the efficiency values (eff1 to effn) After the efficiency is determined, the number of sub-circuit portions corresponding to the optimum efficiency and the equal current distribution value are determined, and then the operation of the sub-circuit portion is controlled so that the output of the current distribution value can be output to the determined number of sub-circuit portions .

As a result, the DC converter can be operated at the optimum efficiency point, and the entire DC converter can be operated at the optimum efficiency point by the selection operation of the sub circuit portion reflecting the optimum efficiency and the current amount distribution control As a result, the operating efficiency of the DC / DC converter is improved.

In addition, when the control method of the DC-DC converter is applied to a control method of a bi-directional high-voltage DC converter (BHDC) of an eco-friendly automobile such as a fuel cell hybrid vehicle, optimal control of the DC- The fuel efficiency of the engine is improved.

4 is a flowchart showing an embodiment in which efficiency hysteresis and current amount even distribution control are additionally applied to increase the durability of the DC / DC converter. The optimum efficiency (eff) and the number of uses (number of operations) After the equal current distribution values i1 to i3 are determined, it is determined which sub-circuit section is to be selected and operated according to the determined number of uses for power conversion and voltage / current output required by the vehicle controller, Based on the accumulated current amounts Ca, Cb and Cc.

That is, in the embodiment of FIG. 4, the number of sub-circuit portions to be used for power conversion is selected in accordance with the accumulated cumulative current amount of each sub-circuit portion so that the whole current amount uniform distribution control can be performed on the sub-circuit portion in the DC- have.

Thus, the operation time and current amount of each sub-circuit portion and the power module (including the switching device) included therein can be evenly limited, and the durability of the sub-circuit portion and the power module can be increased.

First, the number of sub-circuit portions corresponding to the optimum efficiency (eff) and the equal current distribution values (i1 to i3) are determined and the optimal efficiency value is stored (S17).

Basically, the number of sub-circuit portions determined by the number of uses is selected in consideration of the cumulative current amounts Ca, Cb, and Cc for each sub-circuit portion. At this time, the number of sub-circuit portions is selected in descending order of the cumulative operating current amount.

For example, if one sub-circuit portion is to be used, that is, if the number of sub-circuit portions to be used is determined to be 1, a sub-circuit portion having the smallest accumulated operation current amount is selected and operated, And accumulates and accumulates in the amount of the accumulated current of the circuit part.

4, when the number of used sub-circuit portions is one and the respective accumulated operation current amounts of the three sub-circuit portions are Ca, Cb, and Cc, the minimum cumulative operating current amount C of Ca, Cb, One sub-circuit section is selected so that one sub-circuit section is operated so that the current output of i * requested by the host controller is made, and the accumulated accumulated current amount of the sub-circuit section is set to 'i * (C + i * x operation time → C) (S18 ', S19'). Here, i * is a current distribution value of one sub-circuit portion to be operated.

When the number of sub-circuit portions is determined to be two, two sub-circuit portions having small cumulative operation current amount are selected, and two of the sub-circuit portions are operated so that a current output of i * / 2 is achieved, The accumulated cumulative current amount is stored as a value obtained by newly accumulating the accumulated cumulative current amount by the "i * / 2 × operating time". Here, i * / 2 is the current distribution value of the two sub circuit portions to be operated.

In the flowchart of FIG. 4, it is described that the remaining two sub-circuit portions except for one sub-circuit portion having the maximum amount of operation cumulative current among the three sub-circuit portions in the same meaning are operated (S18 ", S19 ").

When the number of sub-circuit portions is determined to be three, the entire sub-circuit portion is operated so that the current output of i * / 3 is performed, and the accumulated accumulated current amount of each sub- (S19 "'), where i * / 3 is the current distribution value of the three sub-circuit sections to be operated.

Although the example of the DC converter having three sub circuit portions is described above, if the number of the sub circuit portions is m (m? N, m is a natural number), if the DC converter is extended to a DC converter having n sub circuit portions connected in parallel The converter controller selects the m sub-circuit portions in the order of the small accumulated operating current amount in consideration of the cumulative operating current amount of each sub-circuit portion, and controls the m sub-circuit portions so that the current output of i * / m is performed .

Also, the accumulated accumulated current amount of each sub circuit portion is stored as a value obtained by newly accumulating the accumulated accumulated current amount by an 'i * / m × operating time', where i * / m is a current distribution value of each sub circuit portion to be operated.

4, the sub-circuit portion to be used for power conversion is selected according to the amount of cumulative operation current of each converter sub-circuit portion, so that the sub-circuit portion in the DC-DC converter can be used equally, So that the equal distribution control can be performed.

As a result, the operating time and current amount of each sub-circuit portion and the power module (including the switching device) included therein can be evenly limited, and the durability of the sub-circuit portion and the power module can be increased.

4, after the optimum efficiency value eff is determined, it is compared with the optimum efficiency value pre_eff of the previous cycle, and when the efficiency difference is equal to or smaller than the predetermined set value a, It is possible to additionally apply efficient hysteresis control for selecting and controlling the sub-circuit portion according to the number of uses only when the operation mode of the sub-circuit portion is greater than the set value.

That is, if the optimum efficiency value eff is determined in the previous steps S15 ', S15', and S15 "', the current optimum efficiency value eff is compared with the optimum efficiency value pre_eff in the previous cycle (S16) When the difference between the current efficiency value and the previous efficiency value is equal to or less than a predetermined set value (a) (eff - pre_eff? A), the sub circuit portion selected in the previous cycle and the sub- The circuit portion is operated as it is and the current demand value required by the vehicle controller is satisfied.

At this time, the current demand value of the current host controller is evenly distributed according to the number of the sub circuit sections used in the previous cycle, and the operation of each sub circuit section is controlled so that the output of the current value can be uniformly distributed from each sub circuit section.

Of course, if only one sub-circuit portion is operated in the previous cycle, control is performed so that all the current requirement values of the host controller are outputted from one sub-circuit portion.

On the other hand, when the difference between the current efficiency value and the previous efficiency value is larger than the set value (a), as described above, the current amount equalization control for selecting and operating the sub- Conduct.

In the case where the improvement efficiency is insufficient by comparing the calculated optimum efficiency with the transfer efficiency, the conventional operation method is maintained. When the effect is large (when the efficiency difference is larger than the set value), only the operation amount equalization distribution control (A new operating number application and a new sub circuit selection operation).

As a result, efficiency hysteresis is applied to limit the operation mode change according to the efficiency difference, thereby reducing the switching loss due to frequent changes in the number of sub circuit parts and the efficiency deterioration due to the current change.

In this way, in the present invention, when the current demand of the vehicle is required, the efficiency when the sub-circuit portions 1, 2, and 3 are used is calculated instead of the conventional method in which the entire sub- So that the output of the sub-circuit can be controlled at the optimum efficiency point considered. In addition, in order to improve the durability problem, the amount of the operating current is accumulated so that the entire sub-circuit portion operates alternately without operating only the specific sub- Hysteresis is provided to minimize losses due to frequent changes in quantity in a specific current range.

5 is a diagram illustrating an efficiency characteristic of the DC-DC converter according to the current and an arbitrary required current of the vehicle according to time, and FIG. 6 is a diagram showing an efficiency curve according to a control method.

Referring to FIG. 6, it can be seen that in the case of applying the conventional control method ('1/3 current distribution', blue), it is advantageous in terms of efficiency in a region where a high current is used, have.

In addition, in the case of using one sub circuit portion (black), it is advantageous in the low current region, but in the high current region, the efficiency is low.

On the other hand, as in the present invention, the best efficiency can be ensured when one, two, or three sub-circuit portions are suitably used depending on the required current rate ('max efficiency', red).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments. Forms are also included within the scope of the present invention.

1: fuel cell 2: battery
3: DC converter 3a:
3b: converter controller 3c: gate driver
4: DC-link terminal 5: Inverter
6: motor controller 7: drive motor
10: Host controller Q1, Q2: Switching element

Claims (8)

A method of controlling a parallel-type DC converter in which n sub-circuit portions in which DC-DC power conversion is performed are connected in parallel and a current output according to a current demand value is performed by operation of a sub-
a) obtaining a current distribution value to be evenly distributed to the sub circuit part according to the number of uses of the sub circuit part from the current demand value;
b) obtaining a predetermined efficiency value corresponding to each current distribution value from a current distribution value according to the number of uses of the sub circuit section;
c) comparing the efficiency values corresponding to the respective current distribution values to determine the number of uses and the current distribution value of the sub circuit section indicating the maximum efficiency value; And
d) selecting the determined number of sub-circuit portions and controlling operation of each selected sub-circuit portion so that the current output of the determined current distribution value is made,
When the maximum efficiency value, the number of sub-circuit units to be used, and the current distribution value are determined, the difference between the determined maximum efficiency value and the maximum efficiency value of the previous cycle is compared with a predetermined set value. And the output of the current demand value is satisfied by the operation of the sub circuit section which has been selected and operated in the cycle.
The method according to claim 1,
In the step b), the current value vs. the current value defining the corresponding efficiency value according to the current value. And the efficiency table information is used.
The method according to claim 1,
And when the number of the sub circuit portions is one, the current distribution value of one used number is obtained by the current request value.
The method according to claim 1,
Wherein in the step of selecting the sub circuit section in the step d), the sub circuit sections are selected as many as the number of the used sub circuit sections in descending order of the cumulative operating current amount among all the sub circuit sections.
The method of claim 4,
And the accumulated cumulative current amount of each of the sub circuit portions to be operated is accumulated in the previous cumulative current amount by a sum of the current divided value and the operating time in the process of controlling the operation of each selected sub circuit portion in the step d) DC converter.
delete The method according to claim 1,
And controls so that an evenly divided current output of the current demand value is performed in each of the sub circuit portions selected and operated in the previous cycle.
The method according to claim 1,
If the difference between the current maximum efficiency value and the maximum efficiency value of the previous cycle is greater than the set value, performing step d) according to the number of used sub-circuit parts and the current distribution value determined in step c) DC converter.

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