JP2011168226A - Control device for series hybrid vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device capable of appropriately controlling an output of a battery in accordance with a DC bus voltage. <P>SOLUTION: Based on a target output P<SB>B</SB>of the battery 23 and a charging rate SOC of the battery 23, a DC bus voltage command value Vbus<SP>*</SP>to a DC bus 8 is set and an output to the DC bus 8 from the battery 23 is controlled so as to reach the target output P<SB>B</SB>of the battery. When the output from the battery 23 to the DC bus 8 reaches the target output P<SB>B</SB>of the battery, electric energy supplied from a generator 2 is controlled so that the DC voltage level of a converter 21 approaches the DC bus voltage command value Vbus<SP>*</SP>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an output control technique for a hybrid vehicle, and more particularly to a control device that performs output control of a series hybrid vehicle.

  A hybrid vehicle is known that travels by combining a plurality of power sources and operating the power sources simultaneously or individually depending on the situation. Among these, there is a series hybrid system in which a battery is charged with electric power generated by turning a generator with an engine or used as running energy. This scheme is used only to drive the generator without the engine turning the wheels. In this way, all the driving force of the wheels is supplied from the motor, and the flow of power is in series, so it is called a series system. Incidentally, as another method, there is a parallel hybrid method in which the engine is mainly driven and used as a power source for charging a battery in some cases. This method is called a parallel method because two power sources, an engine and a motor, are involved in driving in parallel.

The inventor has previously proposed an apparatus for controlling electric power in a series hybrid vehicle (Patent Document 1).
A circuit configuration of a control device according to Patent Document 1 is as shown in FIG. 10, and a battery 101 is connected in parallel to an a terminal and a b terminal that are output terminals of a converter 103 via a power converter 102. The power conversion device 102 composed of a bidirectional DC / DC converter controls the charge / discharge current according to the voltage level of the DC bus voltage Vbus applied to the a terminal and b terminal which are output terminals of the converter 103. For example, in order to respond to the output (load) required by the vehicle, when the rotation of the engine 104 and the generator 107 increases and the converter 103 outputs, the DC bus voltage Vbus increases. At this time, the battery 101 is controlled to be charged. Further, when the inverter 105 absorbs power, the DC bus voltage Vbus decreases, and the battery 101 is discharged.
Then, inverter 105 outputs the sum of the power from battery 101 and the power from converter 103 to motor 106. Thus, the battery 101 and the motor 106 can be controlled only by controlling the DC bus voltage Vbus. Since control of the battery 101 itself is left to the power converter 102 only, the converter 103 only needs to monitor the command of what output the driver wants to make the vehicle and the DC bus voltage Vbus.

  Further, the power conversion device 102 configured by a DC / DC converter converts the voltage from a low voltage (for example, 300 V) battery 101 to a high voltage DC bus voltage Vbus (for example, 600 V) and supplies power. Playing a role.

  The voltage of the battery 101 has characteristics that vary depending on output power / current of the battery 101, SOC (State of Charge, battery charge rate [%] = remaining battery capacity / full charge capacity of battery × 100), and the like. . However, according to the control device of Patent Document 1, by providing the power converter 102 with a function of controlling the output of the battery 101 in response to the DC bus voltage Vbus, the DC bus voltage Vbus regardless of the characteristics of the battery 101. The battery 101 can also be controlled only by controlling (system voltage).

Japanese Patent No. 3886940

The power conversion device 102 made up of a bidirectional DC / DC converter has a large space for occupying the vehicle when used in a hybrid vehicle, is not easy to be mounted on the vehicle, and is disadvantageous in terms of cost.
In addition, in the hybrid vehicle, power input / output to / from the battery 101 frequently occurs, and the energy loss due to the power conversion device 102 is large. Therefore, the vehicle fuel consumption decreases due to the presence of the power conversion device 102.
The present invention has been made based on such a problem, and an object of the present invention is to provide a control device that can appropriately control the output to the battery corresponding to the DC bus voltage without using a power converter. .

The present invention relates to an output control device for a series hybrid vehicle, which includes an engine that generates a driving force, a generator that generates electric power using the driving force generated by the engine, and an electric power generated by the generator. A converter that converts alternating current power into direct current and controls the voltage, a battery that is charged with the power supplied from the converter, a motor that uses the generator and the battery as a power source, and power from the converter and the battery And a bus for supplying the motor to the motor.
And the control apparatus by this invention controls electric power supply in the following procedures. In other words, the DC voltage command value for the bus is set based on the target output of the battery and the charging rate of the battery, the output from the battery to the bus is controlled to reach the target output, and the output from the battery to the bus becomes the target output. When it reaches, the power from the generator is controlled so that the DC voltage level of the converter approaches the DC bus voltage command value.
Since the control device of the present invention sets the DC bus voltage command value in consideration of the charging rate of the battery, an appropriate output can be given from the battery to the bus.

  The control device according to the present invention can set the DC bus voltage command value in consideration of one or both of the battery temperature and the battery deterioration state. By doing so, even when the temperature of the battery changes or when the characteristics of the battery change due to deterioration, an appropriate output can be given from the battery to the bus.

  The control device according to the present invention preferably determines the target output of the battery and the output from the generator based on the required load power for the vehicle and the maximum output of the generator. By doing so, since the battery and the generator, in other words, the output from the engine can be supplied to the bus without overs and shorts with respect to the load request, it is possible to prevent insufficient vehicle performance such as acceleration and engine overload.

  The control device according to the present invention gives priority to the output from the generator to the bus over the output from the battery to the bus when the charging rate of the battery is lower than a preset threshold, and from the generator Is preferably used for charging the battery. By doing so, it becomes possible to maintain the charge rate of the battery within a specified range, and it is possible to prevent overcharge and overdischarge of the battery. Further, since the battery can be operated at a medium charge rate, sufficient acceleration (discharge) and regenerative braking (charge) can be secured at all times, and the battery life can be extended because the fluctuation range of the charge rate is narrow.

  Since the control device of the present invention sets the DC bus voltage command value in consideration of the charging rate of the battery, an appropriate output can be given from the battery to the bus.

It is a block diagram showing a schematic structure of a series hybrid system vehicle in a 1st embodiment. It is a block diagram which shows the procedure of the power control in 1st Embodiment. An example of the battery power-voltage characteristic table in 1st Embodiment is shown. In the first embodiment, (a) is a graph showing the state of power distribution between the battery and the engine when the load on the vehicle is increasing, and (b) is a transition of the DC bus voltage accompanying an increase in the load on the vehicle. It is a graph. An example of the battery power-voltage characteristic table in 2nd Embodiment is shown. It is a block diagram which shows schematic structure of the series hybrid system vehicle in 2nd Embodiment. It is a block diagram which shows the structure which determines the direct-current bus voltage command value in 2nd Embodiment. It is a block diagram which shows the control procedure of the control part in 3rd Embodiment. In 3rd Embodiment, (a) is a graph which shows the mode of the power distribution of a battery and an engine when the load of the vehicle at the time of high SOC mode is increasing, (b) is the load of the vehicle at the time of low SOC mode It is a graph which shows the mode of the power distribution of a battery and an engine when is increasing. It is a block diagram which shows schematic structure of the conventional series hybrid system vehicle.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
[First Embodiment]
FIG. 1 shows a schematic configuration of a series hybrid vehicle 10 according to the present embodiment.
The series hybrid vehicle 10 generates power by driving the generator 2 with the engine 1, and the first traveling motor 3 and the second traveling motor that rotate the first wheel 5 and the second wheel 6, respectively, with the obtained electric power. 4 is driven. The electric power obtained by the generator 2 is also used for charging the battery 23. The battery 23 drives the first travel motor 3 and the second travel motor 4 by discharging the stored electric power. That is, the driving forces of the first wheel 5 and the second wheel 6 are all supplied from the first traveling motor 3 and the second traveling motor 4. Supply of electric power to the first traveling motor 3 and the second traveling motor 4 can be selected from either the generator 2, the battery 23, or the generator 2 and the battery 23.

  As the engine 1 as the internal combustion engine, a diesel engine is mainly used. However, the engine 1 is not limited to this, and known engines such as a reciprocating engine and a rotary engine can be widely applied.

  A converter 21 is attached to the generator 2. The converter 21 electrically connected to the generator 2 converts AC power generated by the generator 2 into DC and controls output to the DC bus 8. Converter 21 controls charging / discharging of electric power from battery 23 by controlling a DC bus voltage.

  One end of the DC bus 8 is connected to the a terminal and b terminal which are output terminals of the converter 21. A DC bus voltage Vbus is applied between the a terminal and the b terminal. The other end of the DC bus 8 is connected to the c terminal and the d terminal which are input terminals of the first inverter 25. The DC bus 8 is branched in the middle, and the branched portion of the DC bus 8 is connected to the e terminal and the f terminal which are input terminals of the second inverter 27. Thus, the first inverter 25 and the second inverter 27 are connected in parallel to each other.

A battery 23 is connected to the DC bus 8 in parallel. The battery 23 is directly connected to the direct current bus 8, and the series hybrid vehicle 10 does not include a power converter such as a bidirectional DC / DC converter. For this purpose, the battery 23 having a voltage corresponding to the DC bus voltage Vbus is used. This also means that the battery 23 having a voltage within the drive voltage range of the first inverter 25 and the second inverter 27 is used.
In addition, an auxiliary machine 7 serving as a power load is connected to the DC bus 8 in parallel. As the auxiliary machine 7, for example, an air conditioner, lighting, and the like are listed, which becomes a power load. The auxiliary machine 7 is an optional component for the present invention.

  The first inverter 25 and the second inverter 27 convert DC power sent through the DC bus 8 into AC and supply the AC power to the first traveling motor 3 and the second traveling motor 4, respectively. The first inverter 25 and the second inverter 27 convert the electric power generated by the regenerative operation of the first traveling motor 3 and the second traveling motor 4 into direct current.

  The DC bus 8 supplies DC power from the converter 21 to the battery 23, the first inverter 25, and the second inverter 27. When the electric power generated when the first traveling motor 3 and the second traveling motor 4 are regenerated is converted into direct current power by the first inverter 25 and the second inverter 27, the battery 23 passes through the direct current bus 8. Send to. Furthermore, regenerative power converted into DC power by one of the first inverter 25 and the second inverter 27 may be sent to the other.

  The first traveling motor 3 connected to the first inverter 25 and the second traveling motor 4 connected to the second inverter 27 are constituted by, for example, a permanent magnet type synchronous motor. The first traveling motor 3 and the second traveling motor 4 are driven by AC power supplied via the first inverter 25 and the second inverter 27, respectively, thereby rotating the first wheel 5 and the second wheel 6. The first travel motor 3 and the second travel motor 4 operate as a generator to generate regenerative power when the first wheel 5 and the second wheel 6 are braked and decelerated. This regenerative power is sent to the first inverter 25 and the second inverter 27 and converted into DC power. In this example, the first traveling motor 3 and the first wheel 5 and the second traveling motor 4 and the second wheel 6 are directly connected, but it goes without saying that a reduction gear may be used.

The series hybrid vehicle 10 includes a control unit 20 that controls operations of the engine 1, the generator 2, the converters 21. The converter 21 controls the output of the electric power from the generator 2 and the battery 23 based on the instruction | command of the control part 20 as follows.
The converter 21 has a function of controlling the output of the generator 2 connected to the engine 1. Specifically, the output of the generator 2 is controlled by adding and subtracting the electric power input and output by the battery 23 from the load required by the vehicle. At this time, the output from the battery 23 is indirectly controlled by referring to the value of the DC bus voltage Vbus. Then, the first inverter 25 and the second inverter 27 output the sum of the electric power from the converter 21 and the electric power from the battery 23 to the first traveling motor 3 and the second traveling motor 4.

<Reference of battery target output P _B and battery SOC>
FIG. 2 schematically shows power control procedures in the control unit 20 and the converter 21.
In this power control system, first, the battery target output P _B and the charging rate of the battery 23 (hereinafter referred to as the battery SOC) are referred to. The battery SOC is referred to for the following reason. As described above, the converter 21 indirectly controls the output of the battery 23 by controlling the output of the generator 2. However, when the battery 23 is repeatedly charged and discharged, its characteristics fluctuate, and the battery voltage depends on this characteristic. Therefore, it is difficult to obtain an arbitrary output (power) from the battery 23. Therefore, the battery SOC that has the greatest influence on the output is considered.
Here, the battery target output P _B is determined based on driving conditions (vehicle load demand) based on the accelerator, steering wheel, brake (not shown) of the vehicle, and the like.
The battery SOC is specified by “remaining battery capacity / full charge capacity of battery × 100”. For example, the battery voltage value and the battery current of the battery 23 are detected, and the remaining battery capacity is determined based on the integrated value. Can be estimated. However, this is the most basic example of specifying the remaining capacity of the battery. In addition to the battery voltage value and the battery current, the remaining capacity of the battery 23 is determined in consideration of the terminal voltage, the terminal current, and the temperature of the battery 23. It can also be estimated.

<Battery power vs. voltage characteristics comparison block>
Next, the power control system determines DC bus voltage command value Vbus ^* with reference to battery target output P _B and battery SOC. This determination is performed in the battery power-voltage characteristic comparison block 29.
The battery power-voltage characteristic comparison block 29 holds a characteristic table in which the battery voltage and the battery power in the battery 23 are associated with each other. This characteristic table is held according to the value of the battery SOC. An example of this characteristic table is graphed and shown in FIG. In FIG. 3, the vertical axis represents the battery voltage, and the horizontal axis represents the battery power (current). As shown in this graph, even with the same battery power, the battery voltage tends to be higher as the battery SOC is higher, and the battery voltage tends to be lower as the battery SOC is lower. For example, if the battery target output is P1 and the battery SOC is S4, the DC bus voltage command value Vbus ^* is determined to be V1 by referring to the characteristic diagram S4 of FIG.
The characteristic table shown in FIG. 3 is experimentally acquired in advance for the battery 23 to be used. Further, although an example using a table (graph) has been described here, the DC bus voltage command value Vbus ^* is determined using a relational expression between the battery voltage and the battery power derived from a value obtained experimentally in advance. You can also.

The DC bus voltage command value Vbus ^* determined as described above is output from the battery power-voltage characteristic comparison block 29 and compared with the actual DC bus voltage Vbus. In response to this comparison result, the DC bus voltage regulator block 33 outputs the torque command value Tg ^* of the generator 2 while further monitoring the actual DC bus voltage Vbus. Converter 21 receives torque command value Tg ^* and controls the operation of generator 2.

An example of power control when the load of the series hybrid vehicle 10 (required vehicle load power) increases will be described with reference to FIG. The vehicle load is determined by the load due to traveling and the total load due to the use of the auxiliary machine 7.
As shown in FIG. 4, when the vehicle load increases, the battery 23 outputs with priority over the generator 2. As the vehicle load increases, the battery voltage, that is, the DC bus voltage Vbus, decreases according to the change in output and characteristics from the battery 23. When the DC bus voltage Vbus decreases and reaches the DC bus voltage command value Vbus ^* , the engine 1 is driven to generate electric power by the generator 2 and supplied to the first inverter 25 and the second inverter 27. . The converter 21 controls the generator 2 such that the DC bus voltage Vbus generated by the output from the generator 2 and the output from the battery 23 matches the DC bus voltage command value Vbus ^* . By this control, the output from the battery 23 is kept constant.

[Second Embodiment]
The second embodiment aims to determine the DC bus voltage command value Vbus ^* with higher accuracy. That is, since the battery power-voltage characteristic is affected by the temperature (T _B ) and the deterioration state (battery SOH) of the battery 23 in addition to the battery SOC, the DC bus voltage command value is determined by the power-voltage characteristic taking these into consideration. Determine Vbus ^* . Note that the battery deterioration state (State of Health) is specified by the deterioration full charge capacity / initial full charge capacity × 100 [%].

FIG. 5 shows an example of battery power-voltage characteristics in consideration of the battery temperature T _B and the battery SOH. As shown in FIG. 5, even if the battery SOC is the same, the characteristics of the battery 23 change. That is, to the low battery temperature T _B increases the internal resistance of the battery 23, even in the power of the battery 23 (output) are the same, the voltage during charging is high, the voltage at the time of discharging is low, battery The voltage fluctuation range of 23 increases. The same applies to the case where the battery SOH is small, that is, the degree of deterioration of the battery 23 is large. When the degree of deterioration of the battery temperature T _B is high or the battery 23 is small, contrary, the voltage variation width of the battery 23 is reduced to this. Although FIG. 5 shows a characteristic diagram for one battery SOC, actually, a similar characteristic diagram is prepared for a plurality of different batteries SOC.

In the second embodiment, as shown in FIG. 6, in order to detect the battery temperature T _B, providing a temperature detection sensor 24 to the battery 23. The temperature of the battery 23 detected by the temperature detection sensor 24 is sent to the control unit 20.
The battery 23 is provided with a charge / discharge history monitoring circuit 28. Since the main factor for the deterioration of the battery 23 is the number of charge / discharge cycles, the charge / discharge history of the battery 23 obtained by the charge / discharge history monitoring circuit 28 is sent to the control unit 20.
Control unit 20, as shown in FIG. 7, the obtained battery SOC, the history of the battery temperature T _B, and charging and discharging, by comparing the characteristic diagram shown in FIG. 5, determines the DC bus voltage command value Vbus ^* To do. By doing so, a desired battery output can be obtained even when the temperature of the battery 23 changes or the battery power-voltage characteristic changes due to the deterioration of the battery 23.

[Third Embodiment]
In the third embodiment, the control unit 20 has a function of determining the battery target output P _B input to the battery power-voltage characteristic table in consideration of the vehicle state.
Determination mechanism of the battery target output P _B, as shown in FIG. 8, includes a running power calculation block 37, the maximum engine output calculation block 39 and the battery output decision block 41.

The battery output determination block 41 determines the power distribution between the engine 1 and the battery 23 with respect to the required load power, and calculates and determines the battery target output P _B. The required load power is determined by the sum of the traveling power and the auxiliary power. The travel power is calculated and determined using the motor rotation speed and the motor torque command value for each of the first travel motor 3 and the second travel motor 4. This will be described in more detail below.

In the driving power calculation block 37, for example, the driving power is obtained as follows. That is, the power (travel power) Pr (kW) necessary for the first travel motor 3 and the second travel motor 4 is obtained from the motor rotation speed (n (rpm)) and the motor torque command value (T (N · m)). The traveling power P1 (= Pr / η) applied to the DC bus 8 in consideration of the efficiency η of the first traveling motor 3, the second traveling motor 4, the first inverter 25, and the second inverter 27 to the traveling power Pr Is required. Since the motor torque is proportional to the applied current, a current command value can be used instead of the motor torque command value (T (N · m)).
The electric power (auxiliary power) P2 required for the operation of the auxiliary machine 7 is calculated separately.
Load required power P _L by adding the traction power P1 and the auxiliary power P2 is determined.

In running power calculation block 37, the rotational speed the engine 1, the amount of depression of the accelerator pedal, based on the opening degree information of the governor engine 1, the engine 1 is determined the maximum output P _E at that time.

Battery output determination block 41, by comparing the load required power P _L and the maximum output P _G of the generator 2 obtained from the engine maximum output P _E, the power to be output battery 23 (battery target output) P _B (= P _L −P _G ) is determined. Thus, the power distribution between the engine 1 (generator 2) and the battery 23 is specified.

In the battery output determination block 41, in addition to determining the battery target output P _B , the high SOC mode or the low SOC mode is selected by referring to the battery SOC. The control of power distribution output from each of the engine 1 (generator 2) and the battery 23 differs between the high SOC mode in which the battery SOC is high and the low SOC mode in which the battery SOC is low.

  As shown in FIG. 9A, the high SOC mode gives priority to the power from the battery 23 as in FIG. If the battery SOC is 50% or more, for example, it is determined that the high SOC mode is set. Of course, a value other than 50% can be used as a reference for the level of the battery SOC.

In the low SOC mode (for example, less than 50%), priority is given to the output from the engine 1 via the generator 2 as shown in FIG. When the output from the engine 1 is started, the electric power generated by the generator 2 is supplied to the load (the first traveling motor 3, the second traveling motor 4 and the auxiliary device 7) and also used for charging the battery 23. Thus, in the process in which the output of the engine 1 increases, the output of the engine 1 is supplied to the load and used for charging the battery 23. However, when the output of the engine 1 approaches the engine maximum output P _E (for example, 0.8 P _E ), the power supplied for charging the battery 23 is reduced. Then, when the output of the engine 1 reaches the maximum engine output P _E, charging of the battery 23 is stopped. Furthermore, for the portion that exceeds the maximum engine output P _E, that in addition to the output from the engine 1 is output from the battery 23, meet the load demand power P _L.
Here, as shown in the high SOC mode (FIG. 9A) and the low SOC mode (FIG. 9B), the SOC is in two stages, but the high SOC mode, the medium SOC mode, and the low SOC mode. It is also possible to set the SOC mode in three stages, or four stages or more.

As described above, according to the third embodiment, the output of the engine 1 (generator 2) and the battery 23 is distributed in consideration of the battery SOC, so that an output can be supplied to the request from the load without excess or deficiency. Therefore, it is possible to prevent insufficient vehicle performance such as acceleration and overload on the engine 1.
Here, when the battery SOC is maintained at a high value, the battery 23 is excessively charged by the regenerated electric power. On the other hand, when the battery SOC is maintained at a low value, the battery 23 supplies electric power that meets the demand from the load. In general, the battery SOC is required to be maintained at about 50 to 60%. On the other hand, according to the third embodiment, since charging / discharging of the battery 23 is determined in consideration of the battery SOC, the battery SOC can be kept at about 50 to 60%, so that the battery 23 is excessively charged. Or excessive discharge. In addition, since the battery SOC can be operated at an intermediate level of 50 to 60%, the battery 23 has a long life because the swing range of the battery SOC is narrow while always ensuring sufficient acceleration (discharge) and regenerative braking (charging). be able to.
Further, by determining the battery target output P _B in consideration of the power distribution between the engine 1 and the battery 23, that is, the engine fuel efficiency, it is possible to expect an improvement in the engine fuel efficiency.

In the first to third embodiments, it is assumed that the vehicle travels with the first wheel 5 and the second wheel 6 itself. However, the present invention can be applied to a vehicle that travels via a caterpillar, for example.
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

DESCRIPTION OF SYMBOLS 10 ... Series hybrid system vehicle 1 ... Engine, 2 ... Generator, 3 ... 1st traveling motor, 4 ... 2nd traveling motor 5 ... 1st wheel, 6 ... 2nd wheel, 7 ... Auxiliary machine, 8 ... DC bus 20 DESCRIPTION OF SYMBOLS ... Control part, 21 ... Converter, 23 ... Battery, 24 ... Temperature detection sensor 25 ... 1st inverter, 27 ... 2nd inverter, 28 ... Charge-discharge history monitoring circuit 29 ... Battery power-voltage characteristic comparison block 33 ... DC bus voltage Regulator block 37 ... Power calculation block for driving, 39 ... Engine maximum output calculation block 41 ... Battery output determination block

Claims (4)

An engine that generates driving force;
A generator for generating electricity by the driving force generated by the engine;
A converter that converts alternating current power generated by the generator into direct current and supplies voltage by controlling the voltage;
A battery charged with power supplied from the converter;
A motor powered by the generator and the battery;
A bus for supplying electric power from the converter and the battery to the motor;
An output control device for a series hybrid vehicle comprising:
The controller is
Set a DC voltage command value for the bus based on the target output of the battery and the charging rate of the battery,
Controlling the output from the battery to the bus to reach the target output;
When the output from the battery to the bus reaches the target output, the output from the generator is controlled so that the DC voltage level of the converter approaches the DC voltage command value.
A control apparatus for a hybrid vehicle characterized by the above. The controller is
Setting the DC voltage command value in consideration of one or both of the temperature of the battery and the deterioration state of the battery;
The hybrid vehicle control device according to claim 1. The controller is
Determining the target output of the battery and the output from the generator based on the required load power for the vehicle and the maximum output of the generator;
The control apparatus of the hybrid vehicle of Claim 1 or 2. If the battery charge rate is lower than a preset threshold,
Prioritizing the output from the generator to the bus over the output from the battery to the bus, and providing the output from the generator for charging the battery;
The control apparatus of the hybrid vehicle as described in any one of Claims 1-3.

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