JP2012080689A - Power supply unit for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device for electric vehicle, which can improve the use efficiency of electric energy stored in a main battery while preventing the life of an auxiliary battery from shortening.SOLUTION: A control part 111 controls a DC/DC converter 107 so that SOC of the auxiliary battery 109 is between a first SOC and a second SOC which are less than 100% while an electric vehicle is traveling.

Description

  The present invention relates to a power supply device for an electric vehicle that charges an auxiliary battery from a main battery for driving an electric vehicle through a DC / DC converter.

  2. Description of the Related Art In recent years, attention has been focused on electric vehicles (EVs) that drive a vehicle with a motor instead of an engine to realize a low-carbon society. Such an electric vehicle includes a battery for storing electric power for driving a vehicle driving motor (hereinafter referred to as a main battery), and a battery for operating various in-vehicle devices such as a car navigation device and a car audio (hereinafter referred to as a battery). Auxiliary battery).

  The auxiliary battery is charged by supplying electric power from an external power source when the vehicle is stopped, and using electric power obtained by transforming electric power stored in the main battery with a DC / DC converter while the vehicle is running.

  As a conventional electric vehicle power supply device, the function of controlling the output voltage of the DC / DC converter to a first set voltage that can fully charge the auxiliary battery and a second set voltage that is lower than the first set voltage. When the vehicle is stopped and the main battery is charged, the output voltage is set to the first set voltage, and during traveling, the output voltage is controlled to the second set voltage.

  For example, Patent Document 1 is known as a prior art document.

JP 7-79505 A

  The conventional electric vehicle power supply device attempts to effectively use the energy of the main battery by changing the output voltage of the DC / DC converter and reducing the energy flowing to the auxiliary battery. In particular, the lead battery used as an auxiliary battery has a charging efficiency (the rate at which the power flowing into the battery is actually stored in the battery as the remaining battery capacity (SOC: State of Charge, also referred to as charge amount) is closer to 100%. ) Is lowered, it is effective for efficient use of energy to reduce the voltage during traveling. Particularly in an electric vehicle, such a means is effective because a decrease in the amount of power of the main battery directly leads to a decrease in the travelable distance.

However, since the output voltage of the DC / DC converter during operation of the conventional electric vehicle power supply device is a fixed value, the battery characteristics change when the temperature of the auxiliary battery is different, for example, in winter and summer. Therefore, there is a problem that even if the auxiliary battery is charged with the output voltage of the same DC / DC converter, the charging cannot be sufficiently performed. If the auxiliary battery could not be charged sufficiently, lead sulfate was accumulated and the life of the auxiliary battery was shortened. ,
The present invention has been made to solve the conventional problems, and can improve the use efficiency of the electric energy stored in the main battery while preventing the life of the auxiliary battery from being shortened. It aims at providing the power supply device for motor vehicles.

  The present invention is a power supply device mounted on an electric vehicle, which is a main battery that stores electric energy for driving a traveling motor, and a DC / DC converter that transforms and outputs the electric energy stored in the main battery. An auxiliary battery that is charged by electric energy transformed by the DC / DC converter, an auxiliary battery state detector that detects and outputs the temperature of the auxiliary battery, and the auxiliary battery state A control unit that calculates an SOC that is a battery remaining capacity of the auxiliary battery based on an output of the detection and controls the DC / DC converter, and the control unit is configured to drive the electric vehicle. The DC / DC converter is configured such that the SOC of the auxiliary battery is between the first SOC that is the lower limit value and the second SOC that is the upper limit value. It is for controlling the over data, and the first SOC and second SOC is to 100% larger than 0 and smaller than%.

  In the present invention, the amount of charge from the main battery to the auxiliary battery is controlled using the SOC calculated by detecting the temperature of the auxiliary battery.

  Since the SOC calculated by detecting the temperature of the auxiliary battery is performed, charging control reflecting the temperature of the auxiliary battery is possible. Also, instead of charging the auxiliary battery by changing the output voltage, the SOC can be charged while maintaining the range where the charging efficiency is good by using the SOC, and the state where the charging cannot be sufficiently performed. Can be avoided.

  As described above, the present invention has an effect that the use efficiency of the electric energy stored in the main battery can be improved while preventing the life of the auxiliary battery from being shortened.

1 is a block diagram of an electric vehicle power supply device and its surroundings according to an embodiment of the present invention. The figure explaining operation | movement of the power supply device for electric vehicles in one embodiment of this invention Diagram explaining the operation Diagram explaining the operation Same timing diagram

  Hereinafter, a power supply device for an electric vehicle according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of a power supply device for an electric vehicle according to an embodiment of the present invention.

  An electric vehicle power supply device 1 shown in FIG. 1 is a power supply device mounted on a vehicle. The electric vehicle power supply device 1 receives electric power supplied from the house 2 side (home side) through a plug and charges an internal storage battery. Hereinafter, the configuration of the electric vehicle power supply device 1 and the house 2 will be described.

  The electric vehicle power supply device 1 includes a plug 100 that receives power from the home. The power received by the plug 100 is stored in the main battery 104 via the relay 102 and the main battery state detection unit 103. The electric power stored in the main battery 104 is transmitted to the motor 106 via the inverter 105. In addition, the power received by the plug 100 is transformed by the DC / DC converter 107 and then stored in the auxiliary battery 109 via the auxiliary battery state detection unit 108, and the electric power for operating the in-vehicle device 110 Also used as The electric vehicle power supply device 1 also includes a control unit 111 that controls each unit. Hereinafter, each part will be described in detail.

  The plug 100 is for receiving power supplied from the house 2 by being inserted into an outlet 201 described later. The plug 100 may be a plug for an outlet used in a general home or a dedicated plug.

  The power received by the plug 100 is normally alternating current. The power received by the plug 100 is converted into direct current by the charger 101 and stored in the main battery 104.

  The charger 101 and the main battery state detection unit 103 are electrically connected. If the relay 102 is in an energized state (on), power is supplied from the charger 101 to the main battery 104, and if the relay 102 is in an interrupted state (off), the power supply is interrupted. The control unit 111 controls on / off of the relay 102.

  The relay 102 may be a contact relay having a metal contact that is turned on / off by the magnetic force of an electromagnet, or may be a contactless relay such as a semiconductor relay.

  When the charger 101 detects an abnormality such as an electric leakage, the charger 101 transmits a signal including information on the abnormality to the control unit 111. The relay 102 is cut off when it is dangerous to supply power to the main battery 104 due to factors such as electric leakage and abnormality of the charger 101.

  The main battery 104 detects various states of the main battery 104 and outputs it to the control unit 111. The various states include at least one of the amount of current flowing into the main battery 104, the voltage between the terminals of the main battery 104, or the temperature of the main battery 104 itself.

  The main battery 104 stores DC electric energy output from the charger 101. The stored electrical energy is used to operate a motor 106 described later. For the main battery 104, for example, a nickel metal hydride battery, a lithium ion battery, or a high-capacity capacitor can be used.

  The electrical energy stored in the main battery 104 is converted into alternating current by the inverter 105 and supplied to the motor 106. The motor 106 is connected to the axle of the drive wheel of the vehicle, and is used as a traveling motor for rotating the axle.

  The motor 106 is used as a generator that converts kinetic energy when the vehicle decelerates by regenerative braking force into electric energy and outputs the electric energy. The electric energy generated at this time (hereinafter, regenerative energy) is stored in the main battery 104.

  The DC / DC converter 107 transforms the direct current electric energy output from the charger 101. The transformed electrical energy is stored in the auxiliary battery 109 and used as power for operating the in-vehicle device 110.

  The auxiliary battery state detection unit 108 detects various states of the auxiliary battery 109 and outputs them to the control unit 111. The various states include at least one of the amount of current flowing into the auxiliary battery 109, the voltage between the terminals of the auxiliary battery 109, or the temperature of the auxiliary battery 109 itself.

The auxiliary battery 109 is a battery for storing electric energy transformed by the DC / DC converter 107. The electrical energy stored in the auxiliary battery 109 is used as electric power for operating the in-vehicle device 110. For example, a lead storage battery is used as the auxiliary battery 109.

  Usually, since the voltage of the main battery 104 battery is higher than the voltage of the auxiliary battery 109, the DC / DC converter 107 steps down. The output voltage of the main battery 104 is, for example, about 345V, and the output voltage of the auxiliary battery 109 is, for example, about 12V.

  The in-vehicle device 110 is, for example, an accessory such as a car navigation device or a car audio, a power window, an electrical component such as an ECU (Electronic Control Unit), and various in-vehicle devices such as ETC (registered trademark). The power source for operating these in-vehicle devices 110 is either the electrical energy stored in the auxiliary battery 109 or the electrical energy after the DC / DC converter 107 is transformed.

  The control unit 111 includes a CPU, a ROM, a RAM, and the like. The CPU executes a program stored in the ROM to perform various operations, output control signals, and the like.

  Specifically, the control unit 111 controls the DC / DC converter 107 based on the outputs of the main battery state detection unit 103 and the auxiliary battery state detection unit 108.

  The control of the DC / DC converter 107 performed by the control unit 111 includes control of receiving power supplied from the house 2 when the electric vehicle is stopped and charging the auxiliary battery 109 (hereinafter, “charging process during power reception”). In addition, there is control of charging performed when the electric vehicle is traveling (hereinafter referred to as “in-travel charging process”). Details of these controls will be described later.

  Control unit 111 performs the charging process during power reception and the charging process during traveling based on the remaining battery capacity (SOC). Control unit 111 also calculates this SOC. This SOC is an index representing the storage state of the battery. Terms such as “charge rate” and “charge amount” may be used as the name of this index.

  In the following description, it is assumed that the SOC is expressed as a percentage, a state where power is stored up to the maximum level (full charge state) is defined as “100%”, and a state where no power is stored (discharge state) ) Is defined as “0%”. The battery is normally used within a charge rate range of α% (0 <α <100) to β% (α <β <100).

  The control unit 111 has at least the amount of current flowing into the auxiliary battery 109 output from the auxiliary battery state detection unit 108, the voltage between the terminals of the auxiliary battery 109, or the temperature of the auxiliary battery 109 itself. One is used to calculate the SOC.

  For example, even when the SOC is 100%, the voltage of the auxiliary battery 109 varies depending on the temperature of the auxiliary battery 109 and the like, and even if the auxiliary battery 109 is controlled with the same charging voltage, it is actually stored. Different SOCs are used.

  Therefore, in order to accurately calculate the SOC, it is necessary to consider not only the voltage and current between the terminals of the auxiliary battery 109 but also the temperature. Specifically, the SOC is estimated from the voltage between the terminals with respect to the temperature of the auxiliary battery 109 and the charge / discharge current.

The lead storage battery used as the auxiliary battery 109 has a lower charging efficiency (a rate at which the power flowing into the battery is actually stored in the battery) as the SOC becomes higher (closer to 100%). Such characteristics include not only lead storage batteries, but also nickel metal hydride batteries and lithium ion batteries.
Although it is common to other secondary batteries, lead-acid batteries are particularly prominent.

  While the electric vehicle power supply device 1 is running, the auxiliary battery 109 is charged by the power of the main battery 104. In particular, in an electric vehicle, a decrease in the amount of power of the main battery 104 directly leads to a decrease in the travelable distance. Accordingly, it is required to improve the charging efficiency as much as possible in consideration of the characteristics of the charging efficiency and the SOC as described above during traveling. This is why the control unit 111 performs the running charging process separately from the charging process during power reception.

  In addition, the control unit 111 performs control to turn off the race 102 based on information related to the abnormality detected by the charger 101.

  The house 2 includes a distribution board 200 that distributes commercial power to the home, and an outlet 201 for supplying the distributed power to various electrical devices in the home.

  The house 2 here is not limited to a general house, but may be an apartment house such as an apartment, a store such as a convenience store, a gas station, or the like as long as the outlet 201 can be installed. It may be a charging stand.

  The various electric devices include the electric vehicle power supply device 1, and the outlet 201 supplies power to the inserted plug 100. The outlet 201 may be an outlet used in a general household, or may be a dedicated connector.

  Next, the processing operation of the electric vehicle power supply device configured as described above will be described. 2-4 is a figure explaining the operation | movement of the power supply device for electric vehicles in one embodiment of this invention. FIG. 5 is a timing chart of the electric vehicle power supply device according to the embodiment of the present invention.

The operation of the control unit 111 will be described with reference to FIG. 2. When the control unit 111 starts processing, it first determines whether or not the charger 101 is receiving power (S10). The time when the charger 101 is receiving power is when the plug 100 is inserted into the outlet 201. The charger 101 outputs a signal indicating whether or not power is being received from the plug 100 to the control unit 111. Based on this signal, the control unit 111 can determine whether or not the charger 101 is receiving power.

  When the charger 101 is receiving power (YES in S10), the control unit 111 executes a charging process during power reception (S20) described later.

  When charger 101 is not receiving power (NO in S10), control unit 111 determines whether or not the electric vehicle is running (S30). For example, the control unit 111 determines whether or not the vehicle is running based on on / off of a key of an electric vehicle (not shown). The control unit 111 determines that the vehicle is traveling if the key of the electric vehicle is on and is stopped if the key is off. When the vehicle is not traveling (NO in S30), the control unit 111 ends (ends) the process.

  On the other hand, when the vehicle is traveling (YES in S30), the control unit 111 executes a traveling charging process (S40).

When the charging process during power reception (S20) or the charging process during traveling (S40) ends, the control unit 111 ends (ends) the process. When the process ends (end of FIG. 2), the control unit 111 starts the process again (start of FIG. 2). The control unit 111 repeatedly starts the process every predetermined time (for example, every 100 msec).

  Next, the charging process during power reception will be described with reference to FIG.

  First, the control unit 111 determines whether the current SOC of the auxiliary battery 109 is greater than 100% (S201). If larger than 100% (YES in S201), the control unit 111 stops the DC / DC converter 107 (S202) and ends the charging process during power reception. It is because it will become overcharge if it charges by addition.

  When the SOC of the current auxiliary battery 109 is 100% or less (NO in S201), it is determined whether or not the current SOC of the auxiliary battery 109 is equal to or lower than a predetermined lower limit (hereinafter referred to as the lower limit SOC). (S203).

  When the SOC of current auxiliary battery 109 is lower than the lower limit SOC (for example, 95%) (YES in S203), control unit 111 controls DC / DC converter 107 to supply power to auxiliary battery 109. It is made to supply (S204). If the current SOC of auxiliary battery 109 is greater than the lower limit SOC (NO in S203), control unit 111 ends the charging process during power reception.

  Thus, when auxiliary battery 109 is not fully charged (SOC is 100%), charging is performed by supplying electric power in S204, and charging is performed when SOC reaches 100% in S201 (S202).

  As will be described later, the auxiliary battery 109 is charged so that the SOC does not become 100% in the running charging process, but the charging is performed so that the SOC becomes 100% in the charging process during power reception.

  If charging is continued so that the SOC does not become 100% in the running charging process, lead sulfate accumulates, causing a reduction in the life of the auxiliary battery 109. This can be solved by performing charging (refresh charging) to make the SOC 100%.

  However, it is not preferable to perform refresh charging during traveling because the charging efficiency is lowered. Thus, as described above, refresh charging is preferably performed when the electric vehicle is stopped and power is supplied from the outside of the vehicle. This is because power is supplied from the outside at this time, and there is no need to consider charging efficiency.

  Next, the running charging process will be described with reference to FIG.

  First, control unit 111 sets a target SOC range (hereinafter referred to as a target SOC range) when auxiliary battery 109 is charged. The lower limit value of the target SOC range is called a first SOC, and the upper limit value is called a second SOC. The first SOC and the second SOC are values larger than 0% and smaller than 100%. For example, the first SOC is about 60% and the second SOC is about 90%.

  Following S401, the control unit 111 calculates the current SOC of the auxiliary battery 109. Next, control unit 111 performs the following processing according to the SOC size of current auxiliary battery 109.

When the current SOC of the auxiliary battery 109 is (first SOC + second SOC) / 2 or more, the control unit 111 stops the DC / DC converter 107 (S403). By this stop, charging to the auxiliary battery 109 is also stopped. This is because the power is sufficiently stored in the auxiliary battery 109, and it is not necessary to charge the auxiliary battery 109 with power from the main battery 104.

When the SOC of the current auxiliary battery 109 satisfies the following formula:
(First SOC + second SOC) / 2> current SOC ≧ (first SOC + A%)
The control unit 111 controls the output of the DC / DC converter 107 so that the current to the auxiliary battery 109 becomes zero. As this current, the result detected by the auxiliary battery state detection unit 108 is used. A% is a value of about 10%, for example.

  Although sufficient electric power is stored in auxiliary battery 109, it is closer to the lower limit (first SOC) than S403, so control is performed to maintain the SOC. For example, since the SOC decreases when the in-vehicle device 110 is operating, the control as in S404 is performed to supplement this power with the output of the DC / DC converter 107.

When the SOC of the current auxiliary battery 109 satisfies the following formula:
(First SOC + A%)> current SOC ≧ (first SOC + B%)
The control unit 111 determines whether the output of the DC / DC converter 107 is a predetermined value (for example, 70%) or less (S405). B is a positive value smaller than A.

  If it is equal to or less than the predetermined value (YES in S405), control unit 111 controls DC / DC converter 107 so as to increase the SOC of auxiliary battery 109 by 10%. On the other hand, when it is below the predetermined value (NO in S405), the control unit 111 ends the running charging process.

When the SOC of the current auxiliary battery 109 satisfies the following formula:
(1st SOC + B%)> Current SOC
The control unit 111 controls the DC / DC converter 107 so as to increase the SOC of the auxiliary battery 109 by 10% (S406).

  When S403, S404, S406, and S407 are completed, the control unit 111 ends the traveling charging process.

  Note that the motor 106 can generate regenerative energy as described above. In addition to the above processing, the control unit 111 can predict the electric energy (regenerative energy) output from the motor 106. This prediction can be predicted from an accelerator depression amount, a brake depression amount, and a vehicle speed (not shown).

  If the SOC of the auxiliary battery 109 is smaller than 100% even if the predicted electric energy is charged in the auxiliary battery 109, the control unit 111 converts the electric energy output from the motor 106 into the auxiliary battery 109. The DC / DC converter 107 is controlled so as to be charged.

  By doing so, even if the regenerative energy cannot be recovered beyond the power that the main battery 104 can accept, it can be recovered by the auxiliary battery 109, and energy can be recovered efficiently. There is an effect.

  Further, in S403, S404, S406, and S407 of FIG. 4, charging is not performed until the current SOC of the auxiliary battery 109 becomes the second SOC that is the upper limit value of the target SOC range. That is, the DC / DC converter 107 is controlled so that the SOC of the auxiliary battery 109 is smaller than the second SOC and is larger than the first SOC.

  This is to provide a delay in the SOC so that the above-described regenerative energy can be received. If the second SOC is not reached even when regenerative energy is received, the regenerative energy can be recovered in a range with good charging efficiency.

  The time transition of the processing operations of FIGS. 2 to 4 will be described with reference to FIG. FIG. 5 is an example of the transition of the SOC of the auxiliary battery 109. T0 in FIG. 5 is the state of S202 in FIG.

  Assume that the electric vehicle starts running at T1. From T1 to T2, the SOC of the auxiliary battery 109 gradually decreases due to the use of the in-vehicle device 110. The SOC may increase due to the recovery of regenerative energy.

  Although it is not lower than (first SOC + A%) until T2 is reached, when the SOC is lower than (first SOC + second SOC) / 2, the control unit 111 indicates that the current to the auxiliary battery 109 is zero. The output of the DC / DC converter 107 is controlled so as to become (S404). However, even when this control is performed, as shown in T2, if the power consumption of the in-vehicle device 110 is large, the SOC of the auxiliary battery 109 gradually decreases. When the SOC decreases and falls below (first SOC + A%) at T2, control unit 111 controls DC / DC converter 107 so as to increase the SOC of auxiliary battery 109 by 10%. Also at this time, if charging from the main battery 104 consumes a large amount of power in the in-vehicle device 110, the SOC gradually decreases.

  When the power consumption of the in-vehicle device 110 decreases, as shown from T2 to T3 and T4, power is supplied from the main battery 104 to the auxiliary battery 109, and the SOC gradually increases.

  Subsequently, when the electric vehicle is stopped at T5 (YES in S10) and charging is possible (YES in S11), charging is performed until the SOC of the auxiliary battery 109 reaches 100% (S201). . This charge becomes a fresh charge, and accumulation of lead sulfate can be eliminated. Thereafter, when traveling is started at T6, the same state as T0 is obtained again.

  As described above, the electric vehicle power supply apparatus according to the embodiment of the present invention uses the SOC calculated by detecting the temperature of the auxiliary battery 109 to calculate the amount of charge from the main battery 104 to the auxiliary battery 109. I tried to control it.

  Since the SOC calculated by detecting the temperature of the auxiliary battery 109 is performed, charging control reflecting the temperature of the auxiliary battery 109 is possible. In addition, instead of charging the auxiliary battery 109 by changing the output voltage, the auxiliary battery 109 can be charged while maintaining a range with good charging efficiency by using the SOC, and the charging cannot be sufficiently performed. The state can be avoided.

  As described above, the present invention has an effect that the use efficiency of the electric energy stored in the main battery 104 can be improved while preventing the life of the auxiliary battery 109 from being shortened.

  In the present embodiment, the power supply device for an electric vehicle has been described. However, the present invention can also be applied to a vehicle other than an electric vehicle, for example, a ship propelled by an electric motor or an airplane.

  INDUSTRIAL APPLICABILITY The present invention is useful as a power supply device for an electric vehicle that charges an auxiliary battery from a main battery for driving an electric vehicle through a DC / DC converter.

DESCRIPTION OF SYMBOLS 1 Electric vehicle power supply device 100 Plug 101 Charger 102 Relay 103 Main battery state detection part 104 Main battery 105 Inverter 106 Motor 107 DC / DC converter 108 Auxiliary battery state detection part 109 Auxiliary battery 110 In-vehicle apparatus 111 Control part 2 House 200 Distribution board 201 Outlet

Claims (5)

A power supply device mounted on an electric vehicle,
A main battery for storing electrical energy for driving the motor for running;
A DC / DC converter that transforms and outputs electrical energy stored in the main battery;
An auxiliary battery that is charged by electric energy transformed by the DC / DC converter, an auxiliary battery state detector that detects and outputs the temperature of the auxiliary battery, and
A controller that calculates the SOC, which is the remaining battery capacity of the auxiliary battery, based on the output of the auxiliary battery state detection, and controls the DC / DC converter;
The controller controls the DC so that the SOC of the auxiliary battery when the electric vehicle is running is between a first SOC that is a lower limit value and a second SOC that is an upper limit value. A power supply device for an electric vehicle, which controls a DC / DC converter, and wherein the first SOC and the second SOC are values greater than 0% and less than 100%. The auxiliary battery state detection unit further detects and outputs at least one of an amount of current flowing into the auxiliary battery and a voltage between terminals of the auxiliary battery,
2. The electric vehicle power supply device according to claim 1, wherein the control unit calculates an SOC of the auxiliary battery based on an output of the auxiliary battery state detection. 3. The said control part controls the said DC / DC converter so that SOC of an auxiliary machine battery may be 100%, when the said electric vehicle stops and charges the said main battery. Item 2. The electric vehicle power supply device according to Item 1. The traveling motor can output kinetic energy when the electric vehicle decelerates into electric energy,
The control unit predicts the electric energy output by the traveling motor, and when the SOC of the auxiliary battery when the predicted electric energy is charged to the auxiliary battery is smaller than 100%, 2. The electric vehicle power supply device according to claim 1, wherein the DC / DC converter is controlled so as to charge the auxiliary battery with electric energy output from a traveling motor. The traveling motor can output kinetic energy when the electric vehicle decelerates into electric energy,
The control unit controls the DC / DC converter so that the SOC of the auxiliary battery is smaller than the second SOC and larger than the first SOC. The electric vehicle power supply device according to claim 1.