KR101822243B1 - Control method of converter for vehicle - Google Patents

Abstract

Deriving a maximum voltage command and a minimum voltage command of the converter using the operating condition including the speed of the vehicle and the required torque, the converter output voltage maximum value, and the battery voltage value from the control unit; Deriving a minimum loss voltage command of the converter using the derived maximum voltage command, the minimum voltage command, the vehicle speed and the required torque; And applying the derived minimum loss voltage command to the output voltage of the converter.

Description

[0001] CONTROL METHOD OF CONVERTER FOR VEHICLE [0002]

The present invention relates to a vehicle converter control method capable of reducing the power loss of a converter provided to increase the efficiency of an inverter and a motor in an environmentally friendly vehicle, thereby improving the efficiency of the vehicle power system.

Recently, as interest in environmentally friendly vehicles has increased, hybrid vehicles having both an engine and an electric motor as power sources have been widely used. Hybrid vehicles are equipped with low-voltage batteries for engines and electric components and high-voltage batteries for electric motors.

Since hybrid cars usually do not have an alternator for charging low-voltage batteries, a step-down, isolated DC-DC converter with a high-voltage battery as the input for charging low-voltage batteries and supplying power to electrical products is needed It becomes. Since the electric power consumption is also increased due to the recent increase in electrical products, the DC-DC converter needs to convert a large amount of electric power.

In this case, the heat generation due to the loss in the DC-DC converter also increases, and the weight of the cooling device added for the heat dissipation measures increases and the weight of the secondary battery increases. Therefore, not only for improving the conversion efficiency but also for reducing the amount of heat and reducing the weight of the cooling apparatus, it is necessary to reduce the loss of the DC-DC converter.

Therefore, many techniques have been developed to increase the efficiency of a converter used in a power conversion system of an automobile, and in the " Method of estimating the DC-DC converter current "in Patent Document 10-2014-0140863, This paper presents a method to improve the efficiency of converter.

However, since this method does not consider the overall power system of the vehicle to which the converter is applied, the efficiency of the converter is increased, but the loss of the other power system associated with the converter is increased, There is a problem that the power loss may become large.

It should be understood that the foregoing description of the background art is merely for the purpose of promoting an understanding of the background of the present invention and is not to be construed as an admission that the prior art is known to those skilled in the art.

KR 2014-0140863 A

An object of the present invention is to provide a vehicle converter control method capable of controlling an output voltage of a converter provided in a vehicle, thereby reducing the amount of loss energy and ultimately improving the efficiency of the vehicle power conversion system.

According to an aspect of the present invention, there is provided a method of controlling a converter of a vehicle, the method comprising: controlling a converter to output a maximum voltage command and a minimum voltage command of the converter using a converter output voltage maximum value and a battery voltage value, Deriving a voltage command; Deriving a minimum loss voltage command of the converter using the derived maximum voltage command, the minimum voltage command, the vehicle speed and the required torque; And applying the derived minimum loss voltage command to the output voltage of the converter.

Deriving the maximum voltage command of the converter includes deriving a first motor maximum required voltage and a second motor maximum required voltage using an operating condition including a vehicle speed and a required torque; Comparing the derived first motor maximum required voltage and the second motor maximum required voltage; When the first motor maximum required voltage is equal to or greater than the second motor maximum required voltage, the first motor maximum required voltage is set as the maximum voltage, and when the second motor maximum required voltage exceeds the first motor maximum required voltage, Setting a required voltage to a maximum voltage; Comparing a set maximum voltage with a magnitude of a converter output voltage maximum value; And setting the maximum voltage as the maximum voltage command when the set maximum voltage is equal to or greater than the converter output voltage maximum value and setting the converter output voltage maximum value as the maximum voltage command when the converter output voltage maximum value exceeds the maximum voltage .

The step of deriving the first motor maximum required voltage and the second motor maximum required voltage includes the steps of: inputting the vehicle speed and the required torque as input and outputting map data having the first motor maximum required voltage and the second motor maximum required voltage as outputs And the like.

Wherein deriving the minimum voltage command of the converter includes deriving a first motor minimum required voltage and a second motor minimum required voltage using an operating condition including a vehicle speed and a required torque; Comparing the derived first motor minimum required voltage and the second motor minimum required voltage; When the first motor minimum required voltage is equal to or less than the second motor minimum required voltage, the first motor minimum necessary voltage is set to the minimum voltage, and when the second motor minimum required voltage is less than the first motor minimum necessary voltage, To a minimum voltage; Comparing the set minimum voltage with the magnitude of the battery voltage value; And setting the minimum voltage as the minimum voltage command when the set minimum voltage is equal to or less than the battery voltage value and setting the battery voltage value as the minimum voltage command when the battery voltage value is less than the minimum voltage.

The step of deriving the first motor minimum required voltage and the second motor minimum necessary voltage may comprise the steps of: inputting map data representing an output of the first motor minimum required voltage and the second motor minimum required voltage, And the like.

Deriving the minimum loss voltage command of the converter includes deriving losses of the first motor, the second motor and the converter using an operating condition including a maximum voltage command of the converter, a minimum voltage command, a vehicle speed, ; And setting a voltage command of the converter that minimizes the sum of losses of the derived first motor, second motor, and converter to a minimum loss voltage command.

Wherein deriving the first motor loss comprises: defining a voltage command range of the converter using a maximum voltage command and a minimum voltage command; And deriving a first motor loss using map data in which a vehicle speed, a required torque, and a voltage command within the voltage command range are input and the first motor loss is an output.

Wherein deriving the second motor loss comprises: defining a voltage command range of the converter using a maximum voltage command and a minimum voltage command; And deriving a second motor loss using the map data in which the vehicle speed, the required torque, and the voltage command within the voltage command range are input and the second motor loss is an output.

Wherein deriving the converter loss comprises: defining a voltage command range of the converter using a maximum voltage command and a minimum voltage command; And deriving a converter loss using map data that receives the speed of the vehicle, the required torque, and the voltage command within the voltage command range as input and the converter loss as an output.

And the voltage command range of the converter is a voltage command interval between the minimum voltage command and the maximum voltage command.

Wherein the setting of the minimum loss voltage command includes: limiting a voltage command interval between a maximum voltage command and a minimum voltage command to a voltage command range of the converter; And setting a voltage command of the converter that minimizes the sum of the first motor loss, the second motor loss, and the converter loss within the voltage command range of the converter to the minimum loss voltage command.

And the voltage command range is changed in accordance with a required output change amount of the vehicle.

And extends the voltage command range when the required output change amount of the vehicle exceeds a predetermined output reference.

And the voltage command range is reduced when the required output change amount of the vehicle is equal to or less than a preset output reference.

The following effects can be obtained by using as described above.

First, the energy efficiency of the vehicle power system is improved because the energy loss of the entire system can be reduced by considering the output and voltage loss required by the motor and the converter of the vehicle.

Second, since the energy loss of the vehicle is reduced, the heat generation due to the electric field load is reduced, so that the durability of the electric device is improved and the number of times of driving the cooling device can be reduced, thereby improving the fuel efficiency of the vehicle.

1 is a flowchart of a method of controlling a converter of a vehicle according to an embodiment of the present invention
FIG. 2 is a flowchart showing a step of deriving the maximum voltage command of the converter according to the embodiment of the present invention.
FIG. 3 is a flowchart of a minimum voltage command derivation step of the converter according to the embodiment of the present invention.
FIG. 4 is a graph showing the minimum loss voltage command derivation graph of the converter according to the embodiment of the present invention

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, the method for controlling a converter of a vehicle according to the present invention uses a maximum voltage command and a maximum voltage command of a converter using a converter operating condition including a vehicle speed and a required torque, Deriving a minimum voltage command (S100); (S120) deriving a minimum loss voltage command of the converter using the derived maximum voltage command, the minimum voltage command, the vehicle speed, and the required torque; And applying the derived minimum loss voltage command to the output voltage of the converter (S140).

The step S100 of deriving the maximum voltage command and the minimum voltage command of the converter determines the range of the converter output voltage that maximizes the efficiency of the vehicle power conversion system in consideration of the variables associated with the power conversion system of the vehicle . Therefore, the vehicle speed, the required torque, the converter output voltage maximum value, and the battery voltage value at this stage are all the criteria for determining the output voltage of the converter to the variable values related to the vehicle power efficiency.

In a concrete method for deriving the maximum voltage command, the present invention may include deriving a first motor maximum required voltage and a second motor maximum required voltage using an operation condition including a vehicle speed and a required torque (S200); Comparing the derived first motor maximum required voltage and the second motor maximum required voltage (S220); If the first motor maximum required voltage is equal to or greater than the second motor maximum required voltage, the first motor maximum required voltage is set to the maximum voltage (S230). If the second motor maximum required voltage exceeds the first motor maximum required voltage, Setting the maximum motor required voltage to the maximum voltage (S240); Comparing the set maximum voltage with the magnitude of the converter output voltage maximum value (S260); (S270). When the maximum value of the converter output voltage exceeds the maximum voltage, the converter output voltage maximum value is set as the maximum voltage command ( S280), which is shown in FIG.

According to the present invention, the most necessary value for deriving the maximum voltage command of the converter is the maximum required voltage of the first motor and the second motor. As described above, the control method for increasing the efficiency of the conventional converter only improves the efficiency of the converter itself, but does not consider the entire power conversion system of the vehicle. Therefore, according to the conventional technology, only the efficiency of the converter is increased, and the efficiency of the other power conversion apparatus is decreased, so that the fuel efficiency is rather lowered when the whole vehicle is viewed. In order to solve such a problem, the present invention considers not only the loss of the converter but also the power loss of the first motor and the second motor in deriving the voltage command of the converter, and as a first step, And to derive the maximum required voltage of the motor and the second motor.

Both the first motor and the second motor are electronic motors used in vehicles, and receive current and voltage to rotate and transmit torque to the vehicle. The control reference used in the control of a general electronic motor is the speed of the vehicle, the required torque, the motor rotation speed, etc. In the present invention, the first motor and the second motor derive the maximum required voltage that can satisfy the required output of the vehicle. The vehicle speed and the required torque are input, and the map data is used to derive the first motor maximum required voltage and the second motor maximum required voltage as outputs.

If the maximum required voltage of the first motor and the second motor is derived in the above manner, a step S220 of comparing the maximum required voltages of the first motor and the second motor is performed, The maximum value of the maximum required voltage is set to the maximum voltage and is compared with the maximum value of the converter output voltage. Since this step will be described later in detail, it is necessary to derive the maximum value of the converter voltage command to determine the converter voltage command that minimizes the energy loss in the range below the maximum value of the voltage command, so that the maximum required voltage of the first motor and the second motor It is intended to use only a large value by setting the maximum voltage. If it is determined that the maximum voltage is greater than the converter output voltage maximum value, the maximum voltage is set as the maximum voltage command (S270) If the converter output voltage maximum value is larger than the voltage, the converter output voltage maximum value is set as the maximum voltage command (S280). The step S260 of comparing the maximum voltage with the maximum value of the converter output voltage may be the same as the step S220 of comparing the maximum required voltage of the first motor and the second motor, Only the large value is set as the maximum voltage command.

If the maximum voltage command is set in this way, it is necessary to set the minimum voltage command. This is because it is desirable to limit not only the maximum value of the converter voltage command but also the minimum value in order to quickly and easily derive the point where the energy loss becomes minimum. Accordingly, the present invention proposes a method of setting the minimum voltage command similar to the method of setting the maximum voltage command, and the flowchart is shown in FIG.

3, deriving the minimum voltage command includes deriving a first motor minimum required voltage and a second motor minimum required voltage using an operation condition including a vehicle speed and a required torque (S300) ; Comparing the derived first motor minimum required voltage and the second motor minimum required voltage (S320); If the first motor minimum required voltage is equal to or less than the second motor minimum required voltage, the first motor minimum necessary voltage is set to the minimum voltage (S330). If the second motor minimum required voltage is less than the first motor minimum necessary voltage, Setting a minimum required voltage to a minimum voltage (S340); Comparing the set minimum voltage with the magnitude of the battery voltage value (S360); And setting the minimum voltage to the minimum voltage command when the set minimum voltage is equal to or less than the battery voltage value (S370), and setting the battery voltage value to the minimum voltage command when the battery voltage value is less than the minimum voltage (S380) .

As can be seen from a comparison between the flowcharts of FIGS. 2 and 3, the step of setting the minimum voltage command proceeds in the same order as the step of setting the maximum voltage command. Accordingly, in the step S300 of deriving the minimum required voltages of the first motor and the second motor, the speed and the required torque of the vehicle are inputted and the first motor minimum required voltage and the second motor minimum required voltage are output Based on the map data. However, since the purpose is to set the minimum voltage command, the minimum voltage determined by comparing the first motor minimum required voltage with the second motor minimum required voltage is compared with the battery voltage value, and the smaller value is set as the minimum voltage command . Since the output voltage of the converter according to the present invention can not be lower than the battery voltage value connected to the converter, the minimum value of the converter output voltage can be regarded as the battery voltage value. Therefore, FIG. 3 includes a step of setting a minimum voltage command by comparing the battery voltage value and the minimum voltage.

If the maximum voltage command and the minimum voltage command are derived through the steps shown in FIG. 2 and FIG. 3, the minimum loss voltage command deriving step S120 is performed as shown in FIG. 1, Deriving a loss of the first motor, the second motor and the converter using an operating condition including a maximum voltage command of the converter, a minimum voltage command, a speed of the vehicle, and a required torque; And setting a voltage command of the converter that minimizes the sum of losses of the derived first motor, second motor, and converter to a minimum loss voltage command.

As described above, the object of the present invention is not only to consider the efficiency of the converter but also to consider the efficiency of the entire power conversion system of the vehicle. Therefore, the present invention can be applied not only to the loss of the converter but also to the first motor 2 motor loss is also considered.

Specifically, the first motor loss includes the steps of: defining a voltage command range of the converter using a maximum voltage command and a minimum voltage command; And deriving a first motor loss using map data in which a vehicle speed, a required torque, and a voltage command within the voltage command range are input and the first motor loss is an output. The output voltage of the converter will have a value between the maximum voltage command and the minimum voltage command mentioned above. The interval between the maximum voltage command and the minimum voltage command is limited to the voltage command range, and the vehicle speed and the required torque It is possible to derive the first motor loss using the 3D map having the axis as the axis.

Likewise, the loss of the second motor may also be defined by limiting the voltage command range of the converter using the maximum voltage command and the minimum voltage command; And deriving a second motor loss using map data in which the vehicle speed, the required torque, and the voltage command within the voltage command range are input and the second motor loss is an output, and the loss of the converter Limiting the voltage command range of the converter using the maximum voltage command and the minimum voltage command; And deriving a converter loss using map data that receives the speed of the vehicle, the required torque, and the voltage command within the voltage command range as an input and outputs the converter loss as an output. The voltage command range in the case of deriving the loss of the second motor and the converter will also be limited to the interval between the maximum voltage command and the minimum voltage command in the same manner as when the first motor loss is derived.

If the losses of the first motor, the second motor, and the converter are derived through the above-described method, the voltage command of the converter in which the sum of the losses is minimized is set as the minimum loss voltage command. In this case, consider a method of setting the voltage command that minimizes the sum of the losses by considering both the voltage command of the converter from 0 to the maximum output voltage of the converter. However, if this is done, It takes a long time and gives an excessive load to the control unit which derives the minimum loss voltage command. Therefore, in the present invention, a method of using the maximum voltage command and the minimum voltage command derived above is proposed as a method of quickly and accurately deriving the minimum loss voltage command.

As mentioned above, the maximum voltage command and the minimum voltage command mean the maximum and minimum output voltages that can be output by the converter. The sum of the energy losses is the minimum. Voltage command level The voltage command range that the converter can drive, It is reasonable to search only between commands. Accordingly, the present invention limits the voltage command interval between the maximum voltage command and the minimum voltage command to the voltage command range of the converter after deriving the losses of the first motor, the second motor and the converter. And setting the voltage command of the converter that minimizes the sum of the first motor loss, the second motor loss, and the converter loss within the voltage command range of the converter to the minimum loss voltage command, It suggests how to draw the command.

However, the converter voltage command range in this step may be changed according to the required output change amount of the vehicle. Specifically, when the required output change amount of the vehicle exceeds the preset output reference, the voltage command range will be extended. The voltage command range will be reduced if the output change amount is equal to or less than the predetermined output reference. The reason why the voltage command range is changed in accordance with the required output change of the vehicle is that if the required output change is large, the range of the voltage command change of the converter may be widened. The voltage command range of the converter becomes narrower. Therefore, the voltage command range is reduced in order to quickly derive the minimum loss voltage command. The predetermined output reference herein may be a value that can be set variously according to the state and type of the vehicle.

A graph for deriving the minimum loss voltage command of the converter according to the present invention is shown in FIG. The first motor loss, the second motor loss, and the converter loss are derived from the above-mentioned method, and the total loss value of each loss value can be easily confirmed through the graph. Therefore, in this case, the point at which the loss value becomes minimum is defined as the minimum loss voltage command, and the output voltage of the converter is controlled based on the minimum loss voltage command. In the graph of FIG. 4, the minimum value of the x-axis is the battery voltage value and the maximum value thereof is the output voltage maximum value. This means that the battery voltage value is set as the minimum voltage command of the converter in the above- Value will be set.

If the minimum loss voltage command of the converter is derived in this manner, the step of controlling the output voltage of the converter based on the minimum loss voltage command as shown in FIG. 1 is performed. Finally, the output voltage of the converter is set as the minimum loss voltage command So that the efficiency of the vehicle power conversion system can be maximized.

Although the present invention has been shown and described with respect to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. It will be obvious to those who have knowledge of.

S100: Step of deriving maximum voltage command and minimum voltage command
S120: Step of deriving the minimum loss voltage command
S140: Output voltage control step
S200: Step of deriving the maximum required voltage of the first motor and the second motor
S300: Step of deriving the minimum required voltage of the first motor and the second motor

Claims (14)

Deriving a maximum voltage command and a minimum voltage command of the converter using the operating condition including the speed of the vehicle and the required torque, the converter output voltage maximum value, and the battery voltage value from the control unit;
Deriving a minimum loss voltage command of the converter using the maximum voltage command and the minimum voltage command of the converter and the operating condition; And
And controlling the output voltage of the converter based on the minimum loss voltage command,
Wherein deriving the minimum loss voltage command of the converter comprises:
Deriving a first motor loss, a second motor loss, and a converter loss using an operating condition including a maximum voltage command of the converter, a minimum voltage command, a vehicle speed, and a required torque; And
And setting the voltage command of the converter that minimizes the sum of the derived first motor loss, the second motor loss, and the converter loss to the minimum loss voltage command. The method according to claim 1,
Wherein deriving the maximum voltage command of the converter comprises:
Deriving a first motor maximum required voltage and a second motor maximum required voltage using an operating condition including a vehicle speed and a required torque;
Comparing the derived first motor maximum required voltage and the second motor maximum required voltage;
When the first motor maximum required voltage is equal to or greater than the second motor maximum required voltage, the first motor maximum required voltage is set as the maximum voltage, and when the second motor maximum required voltage exceeds the first motor maximum required voltage, Setting a required voltage to a maximum voltage;
Comparing a set maximum voltage with a magnitude of a converter output voltage maximum value; And
Setting the maximum voltage as the maximum voltage command when the set maximum voltage is equal to or greater than the converter output voltage maximum value and setting the converter output voltage maximum value as the maximum voltage command when the converter output voltage maximum value exceeds the maximum voltage Of the vehicle. The method of claim 2,
Wherein deriving the first motor maximum required voltage and the second motor maximum required voltage comprises:
Wherein the map data is derived using map data in which the vehicle speed and the required torque are input and the first motor maximum required voltage and the second motor maximum required voltage are output. The method according to claim 1,
Wherein deriving the minimum voltage command of the converter comprises:
Deriving a first motor minimum required voltage and a second motor minimum required voltage using an operating condition including a vehicle speed and a required torque;
Comparing the derived first motor minimum required voltage and the second motor minimum required voltage;
When the first motor minimum required voltage is equal to or less than the second motor minimum required voltage, the first motor minimum necessary voltage is set to the minimum voltage, and when the second motor minimum required voltage is less than the first motor minimum necessary voltage, To a minimum voltage;
Comparing the set minimum voltage with the magnitude of the battery voltage value; And
Setting the minimum voltage as the minimum voltage command when the set minimum voltage is equal to or less than the battery voltage value and setting the battery voltage value as the minimum voltage command when the battery voltage value is less than the minimum voltage. The method of claim 4,
Wherein deriving the first motor minimum required voltage and the second motor minimum required voltage comprises:
Wherein the map data is derived using map data in which the vehicle speed and the required torque are input and the first minimum motor voltage and the second minimum motor voltage are output. delete The method according to claim 1,
Wherein deriving the first motor loss comprises:
Limiting the voltage command range of the converter using the maximum voltage command and the minimum voltage command; And
And deriving a first motor loss by using map data in which a speed of the vehicle, a required torque and a voltage command in the voltage command range are inputted and the first motor loss is an output. The method according to claim 1,
Wherein deriving the second motor loss comprises:
Limiting the voltage command range of the converter using the maximum voltage command and the minimum voltage command; And
And deriving a second motor loss using map data in which a speed of the vehicle, a required torque and a voltage command in the voltage command range are inputted and the second motor loss is an output. The method according to claim 1,
Wherein deriving the converter loss comprises:
Limiting the voltage command range of the converter using the maximum voltage command and the minimum voltage command; And
And deriving a converter loss by using map data in which a speed of the vehicle, a required torque, and a voltage command within the voltage command range are input and the converter loss is an output. The method according to any one of claims 7 to 9,
The voltage command range of the converter
Wherein the voltage command section is a voltage command section between the minimum voltage command and the maximum voltage command. The method according to claim 1,
The step of setting the minimum loss voltage command includes:
Limiting the voltage command interval between the maximum voltage command and the minimum voltage command to the voltage command range of the converter; And
And setting a voltage command of the converter that minimizes the sum of the first motor loss, the second motor loss, and the converter loss within the voltage command range of the converter to the minimum loss voltage command. The method of claim 11,
Wherein the voltage command range is changed in accordance with a required output change amount of the vehicle. The method of claim 12,
Wherein the voltage command range is extended when the required output variation amount of the vehicle exceeds a preset output reference. The method of claim 12,
When the required output change amount of the vehicle is equal to or less than a preset output reference, the voltage command range is reduced.

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