WO2010137142A1

WO2010137142A1 - Fuel cell system

Info

Publication number: WO2010137142A1
Application number: PCT/JP2009/059718
Authority: WO
Inventors: 長谷川　貴彦; 伸之北村; 晃太真鍋
Original assignee: トヨタ自動車株式会社
Priority date: 2009-05-27
Filing date: 2009-05-27
Publication date: 2010-12-02

Abstract

It is possible to avoid a trouble caused by overvoltage of various elements to which an inverter voltage is applied. A control unit (8) judges whether a fuel cell (2) is generating electricity and an inverter voltage detected by a voltage sensor (V2) is equal to or above a predetermined upper limit voltage value. If yes, the control unit (8) reduces the duty ratio of an FC converter (3) and limits the output of the FC converter (3). This can suppress abnormal increase of the inverter voltage.

Description

Fuel cell system

The present invention relates to a fuel cell system.

Patent Document 1 below discloses a multi-output DC-DC converter having a plurality of current resonance type DC-DC converters. This multi-output DC-DC converter outputs a voltage corresponding to each load to the load connected to each current resonance type DC-DC converter.

JP 2007-318938 A

In the multi-output DC-DC converter, when the supply-demand balance between the power supplied from the power source and the power consumed by the load is lost, the voltage applied to the input side of the load may rise abnormally. . In such a case, various elements to which the increased voltage is applied may be damaged due to overvoltage.

The present invention has been made to solve the above-described problems caused by the prior art, and an object thereof is to provide a fuel cell system capable of avoiding a failure due to an overvoltage of an element.

In order to solve the above-described problems, a fuel cell system according to the present invention includes a fuel cell that receives supply of a fuel gas and an oxidant gas and generates power by an electrochemical reaction between the fuel gas and the oxidant gas, and a power generated by the fuel cell An electric power unit that can charge the battery, an electric power consuming device that consumes electric power from the fuel cell and the electric power unit, and a first voltage conversion unit that is disposed between the fuel cell and the electric power consuming device A second voltage converter disposed between the livestock power unit and the power consuming device, a determination unit that determines whether or not a supply voltage supplied to the power consuming device abnormally increases, and Output limiting means for limiting the output of the first voltage converter when the determination means determines that the supply voltage is abnormally increased.

According to this invention, it is possible to determine whether or not the supply voltage supplied to the power consuming device is abnormally increased. When it is determined that the supply voltage is abnormally increased, the output of the first voltage conversion unit is determined. Since it can restrict | limit, it becomes possible to suppress the abnormal raise of supply voltage.

In the fuel cell system, the determination unit determines that the supply voltage abnormally increases when the fuel cell is generating power and the supply voltage reaches a predetermined upper limit voltage value or more. It is good.

In this way, when the supply voltage reaches a predetermined upper limit voltage value or more during power generation of the fuel cell, the output of the first voltage conversion unit is limited to suppress an abnormal increase in supply voltage. It becomes possible.

In the fuel cell system, the predetermined upper limit voltage value may be set within a range in which various elements to which the supply voltage is applied are not damaged.

This makes it possible to suppress an abnormal increase in supply voltage without damaging various elements to which the supply voltage is applied.

In the fuel cell system, when the fuel cell is generating electric power and the increase rate of the supply voltage reaches a predetermined upper limit increase rate or higher, the determination voltage is abnormally increased. It may be determined.

In this way, when the rate of increase of the supply voltage reaches a predetermined upper limit increase rate during power generation of the fuel cell, the output of the first voltage conversion unit is limited to suppress an abnormal increase in supply voltage. It becomes possible to do.

In the fuel cell system, the predetermined upper limit increase rate is calculated by adding the assumed voltage even when the voltage assumed as the supply voltage after being increased for a predetermined period according to the predetermined upper limit increase rate is supplied. It is good also as setting in the range where the various elements to be damaged do not damage.

In the fuel cell system, the output limiting unit reduces the duty ratio that fluctuates by controlling an on / off cycle of a switch included in the first voltage conversion unit, whereby the first voltage conversion unit May be limited.

By doing in this way, when it is determined that the supply voltage is abnormally increased, the output of the first voltage converter can be limited, so that it is possible to suppress the abnormal increase of the supply voltage.

In the fuel cell system, the output limiting unit may limit the output of the first voltage converter by setting the duty ratio to 0.

By doing in this way, when it determines with a supply voltage rising abnormally, since the output of a 1st voltage converter can be set to 0, it can suppress an abnormal increase in supply voltage reliably. Become.

In the fuel cell system, the output limiting unit may limit the output of the first voltage converter by stopping a switch included in the first voltage converter in an off state.

According to the present invention, a failure due to an overvoltage of the element can be avoided.

It is a figure which shows typically the structure of the fuel cell system in embodiment. It is a timing chart for explaining the contents of FC converter output restriction processing. It is a flowchart for demonstrating the flow of the converter output limitation process for FC in embodiment.

Hereinafter, preferred embodiments of a fuel cell system according to the present invention will be described with reference to the accompanying drawings. In the embodiment, a case where the fuel cell system according to the present invention is used as an on-vehicle power generation system of a fuel cell vehicle (FCHV; Fuel Cell Hybrid Vehicle) will be described. The fuel cell system according to the present invention can also be applied to various mobile bodies (robots, ships, aircrafts, etc.) other than fuel cell vehicles, and further used as power generation equipment for buildings (housing, buildings, etc.). It can be applied to a stationary power generation system.

First, the configuration of the fuel cell system in the present embodiment will be described with reference to FIG. FIG. 1 is a diagram schematically illustrating a fuel cell system according to an embodiment.

As shown in the figure, a fuel cell system 1 includes a fuel cell 2 that generates electric power by an electrochemical reaction between an oxidizing gas and a fuel gas, and a DC / DC converter 3 (first voltage) for the fuel cell. Converter, hereinafter referred to as "FC converter"), battery 4 as a secondary battery (power storage unit), and battery DC / DC converter 5 (second voltage converter, hereinafter referred to as "Bat converter"). ), A traction inverter 6 and a traction motor 7 (power consuming device) as loads, and a control unit 8 that performs overall control of the entire system. The set of the fuel cell 2 and FC converter 3 and the set of the battery 4 and Bat converter 5 are connected in parallel to the traction inverter 6 and the traction motor 7.

The fuel cell 2 is, for example, a polymer electrolyte fuel cell, and has a stack structure in which a large number of single cells are stacked. The single cell has an air electrode on one surface of an electrolyte composed of an ion exchange membrane, a fuel electrode on the other surface, and a structure having a pair of separators so as to sandwich the air electrode and the fuel electrode from both sides. It has become. In this case, hydrogen gas is supplied to the hydrogen gas passage of one separator, the oxidizing gas is supplied to the oxidizing gas passage of the other separator, and electric power is generated by the chemical reaction of these reaction gases.

The FC converter 3 is a DC voltage converter, and has a function of boosting the DC voltage output from the fuel cell 2 and outputting it to the traction inverter 6 on the power consuming device side. The output voltage of the fuel cell 2 is controlled by the FC converter 3. A voltage sensor V <b> 1 that detects the output voltage of the fuel cell 2 is provided on the input side of the FC converter 3. On the output side of the FC converter 3, a voltage sensor V2 for detecting an input voltage (supply voltage, hereinafter referred to as "inverter voltage") Vi to the traction inverter 6 is provided.

The FC converter 3 includes elements such as a capacitor, a coil, and a switch. The FC converter 3 changes the duty ratio by switching on / off of the switch in accordance with an instruction from the control unit 8, and outputs a voltage corresponding to the required power generation amount.

The battery 4 is configured such that battery cells are stacked and a constant high voltage is used as a terminal voltage, and the surplus power of the fuel cell 2 can be charged or supplementarily supplied by control of a battery computer (not shown). ing. Between the battery 4 and the Bat converter 5, a voltage sensor V3 for detecting the output voltage of the battery 4 is provided.

The Bat converter 5 is a DC voltage converter, which boosts the DC voltage input from the battery 4 and outputs it to the traction inverter 6 on the power consuming device side, and from the fuel cell 2 or traction motor 7 side. And a function of stepping down the input DC voltage and outputting it to the battery 4. The battery 4 is charged and discharged by the function of the Bat converter 5 as described above.

The traction inverter 6 converts a direct current into a three-phase alternating current and supplies it to the traction motor 7. The traction motor 7 is, for example, a three-phase AC motor, and constitutes a main power source of a fuel cell vehicle on which the fuel cell system 1 is mounted.

The control unit 8 detects an operation amount of an acceleration operation member (for example, an accelerator) provided in the fuel cell vehicle, and controls an acceleration request value (for example, a required power generation amount from a power consuming device such as the traction motor 7). Receives information and controls the operation of various devices in the system. In addition to the traction motor 7, the power consuming device includes, for example, auxiliary devices necessary for operating the fuel cell 2, various devices involved in traveling of the vehicle (transmission, wheel control device, steering device, Actuators used in suspension systems, etc., passenger space air conditioners (air conditioners), lighting, audio, etc.

The control unit 8 physically includes, for example, a CPU, a memory, and an input / output interface. The memory includes a ROM that stores a control program and control data processed by the CPU, and a RAM that is mainly used as various work areas for control processing. These elements are connected to each other via a bus. Various sensors such as a voltage sensor are connected to the input / output interface, and various drivers for driving the traction motor 7 and the like are connected.

The CPU receives the detection results of the various sensors via the input / output interface according to the control program stored in the ROM, and processes them using various data in the RAM, whereby various control processes in the fuel cell system 1 are performed. Execute. Further, the CPU controls the entire fuel cell system 1 by outputting control signals to various drivers via the input / output interface. Hereinafter, among the various control processes executed by the control unit 8, the FC converter output restriction process, which is a process unique to the present embodiment, will be described.

The FC converter output restriction process reduces the duty ratio of the FC converter 3 and lowers the output Pfc of the FC converter 3 when the inverter voltage of the traveling fuel cell vehicle is assumed to rise abnormally. By this, it is the process which suppresses the abnormal rise of an inverter voltage. As a case where the inverter voltage of the traveling fuel cell vehicle rises abnormally, for example, the fuel cell vehicle may slip.

The control unit 8 that executes such FC converter output restriction processing has a function as a determination unit and a function as an output restriction unit described below.

The control unit 8 as a determination unit determines whether or not the inverter voltage rises abnormally. Specifically, the control unit 8 determines that the inverter voltage abnormally increases when the fuel cell 2 is generating power and the inverter voltage is equal to or higher than a predetermined upper limit voltage value. The predetermined upper limit voltage value is set within a range in which various elements to which the inverter voltage is applied are not damaged. Examples of the various elements to which the inverter voltage is applied include elements such as capacitors, coils, switches, and ICs included in the FC converter 3, the Bat converter 5, the traction inverter 6, and auxiliary equipment. The predetermined upper limit voltage value is obtained by experiments or the like and is stored in advance in the memory.

Note that the requirement for determining that the inverter voltage rises abnormally is not limited to this. For example, it may be determined that the inverter voltage abnormally increases when the fuel cell 2 is generating power and the increase rate of the inverter voltage is equal to or greater than a predetermined upper limit increase rate. The predetermined upper limit increase rate can be provided for each inverter voltage, for example. In this case, the inverter voltage and the upper limit increase rate may be associated with each other and stored in the map. This map is stored in memory. The upper limit increase rate for each inverter voltage is added to the predicted inverter voltage even when the predicted inverter voltage after the increase assumed when the inverter voltage is increased for a predetermined period according to the upper limit increase rate is supplied. It can be set within a range where various elements are not damaged. The upper limit increase rate and the predetermined period can be obtained by experiments or the like.

The judgment procedure in this case is as follows. First, when the fuel cell 2 is generating power, the inverter voltage at that time is acquired from the voltage sensor V2, and the rate of increase of the inverter voltage at that time is calculated. Subsequently, an upper limit increase rate corresponding to the acquired inverter voltage is extracted from the map. Subsequently, when the calculated increase rate is equal to or higher than the extracted upper limit increase rate, it is determined that the inverter voltage abnormally increases. Thereby, it is possible to suppress an abnormal increase in the inverter voltage without damaging various elements to which the inverter voltage is applied.

Also, for example, when it is detected that the fuel cell vehicle slips, it may be determined that the inverter voltage rises abnormally. Since the inverter voltage increases when the fuel cell vehicle slips, the control is performed on the assumption that the inverter voltage is likely to reach a predetermined upper limit voltage value or higher when slipping. As a result, the output Pfc of the FC converter 3 can be reduced at the time when slip is detected. Therefore, when the inverter voltage is assumed to rise abnormally, the inverter voltage is reliably lowered early. It becomes possible.

The control unit 8 as the output limiting means limits the output of the FC converter 3 when it is determined that the inverter voltage rises abnormally. Specifically, the control unit 8 controls the output voltage of the FC converter 3 by controlling the on / off cycle of the switch included in the FC converter 3 to vary the duty ratio. When it is determined that the inverter voltage rises abnormally, the control unit 8 limits the output of the FC converter 3 by reducing the duty ratio from a normal value based on the required value.

The duty ratio at the time of limiting the output of the FC converter 3 only needs to be reduced to a value that allows the inverter voltage to change within a range in which various elements to which the inverter voltage is applied are not damaged. Therefore, it is not always necessary to reduce the duty ratio to zero. However, since the output of the FC converter 3 can be reduced to 0 by reducing the duty ratio to 0, an increase in the inverter voltage can be reliably suppressed.

The reduced duty ratio may be a fixed value, or may be calculated according to the inverter voltage at that time or the rate of increase of the inverter voltage. When calculating according to the inverter voltage or the increase rate of the inverter voltage, for example, the correspondence relationship between the inverter voltage or the increase rate of the inverter voltage and the duty ratio is stored in advance in the map, and this map is referred to. It may be calculated. The values stored in this map may be obtained by experiments or the like and stored in the memory in advance.

In addition, when controlling the output voltage of the FC converter 3, the switch included in the FC converter 3 may be stopped in an off state. Thereby, since the output of FC converter 3 can be set to 0, the abnormal rise of inverter voltage can be suppressed reliably.

Referring to FIG. 2, the details of the FC converter output restriction process will be described in detail. FIG. 2 shows a case where the FC converter output limiting process according to the present embodiment is performed (Example of the present invention) and a case where the inverter voltage is not performed (Comparative Example) when the inverter voltage reaches a predetermined upper limit voltage value or more. It is a timing chart which illustrates transition states, such as various outputs.

2A shows the transition state of the duty ratio of the FC converter 3, FIG. 2B shows the transition state of the output Pfc of the FC converter 3, and FIG. The transition state of the inverter voltage Vi is shown. 2A, 2B, and 2E, the solid line portion after time t2 indicates the transition state in the embodiment, and the dotted line portion indicates the transition state in the comparative example. 2C shows a transition state of the power consumption Pm of the traction motor 7, and FIG. 2D shows a transition state of the output Pbat of the Bat converter 5. FIG.

First, each transition state in the embodiment of the present invention will be described. For example, when the traveling fuel cell vehicle slips at time t1, the power consumption Pm of the traction motor 7 that drives the wheels decreases as shown in FIG. In FIG. 2C, the power consumption Pm of the traction motor 7 is reduced from A [kw] to B [kw].

Even after the power consumption Pm of the traction motor 7 is reduced due to the slip, if the output Pfc of the FC converter 3 shown in FIG. 2B is maintained at A [kw], surplus power is generated. When surplus power is generated, the Bat converter 5 outputs the surplus power to the battery 4 to charge the battery, as shown after time t1 in FIG.

When the surplus power exceeds the upper limit charge amount C [kw] of the Bat converter 5, as shown after the time t <b> 1 in FIG. To rise.

When the inverter voltage Vi reaches the predetermined upper limit voltage value Vt at time t2, the control unit 8 changes the duty ratio of the FC converter 3 from D to 0 as shown after time t2 in FIG. Reduce towards. As a result, as shown after time t2 in FIG. 2B, the output Pfc of the FC converter 3 decreases. Thereby, as shown after time t2 of (e) of Drawing 2, abnormal rise of inverter voltage Vi is controlled.

On the other hand, in the case of the comparative example, when the traveling fuel cell vehicle slips at time t1, the duty ratio of the FC converter 3 is set to D as shown after time t1 in FIG. It remains maintained. Therefore, as shown after time t1 in FIG. 2B, the output Pfc of the FC converter 3 is also maintained at A [kw]. As a result, as shown in the time t1 and after in FIG. 2 (e), the inverter voltage Vi is reduced by the surplus power generated when the power consumption Pm of the traction motor 7 decreases from A [kw] to B [kw]. The inverter voltage Vi breaks through the breakdown voltage Vm of the element at time t3. Thereby, there exists a possibility that an element may be damaged by overvoltage.

Next, the flow of FC converter output restriction processing in this embodiment will be described using the flowchart shown in FIG. This FC converter output restriction process is started, for example, when the ignition key is turned on, and is repeatedly executed until the operation is completed.

First, the control unit 8 determines whether or not the fuel cell 2 is generating power (step S101). When this determination is NO (step S101; NO), the control unit 8 ends the FC converter output restriction process.

On the other hand, when it is determined in step S101 that the fuel cell 2 is generating power (step S101; YES), the control unit 8 determines that the inverter voltage detected by the voltage sensor V2 is greater than or equal to a predetermined upper limit voltage value. It is determined whether or not (step S102). When this determination is NO (step S102; NO), the control unit 8 ends the FC converter output restriction process.

On the other hand, when it is determined in step S102 that the inverter voltage is equal to or higher than the predetermined upper limit voltage value (step S102; YES), the control unit 8 reduces the duty ratio of the FC converter 3 (step S103). .

As described above, according to the fuel cell system 1 of the present embodiment, the duty ratio of the FC converter 3 is reduced when the inverter voltage reaches a predetermined upper limit voltage value or more during power generation of the fuel cell 2. Thus, the output of the FC converter 3 can be limited. Thereby, since the abnormal rise of an inverter voltage can be suppressed, the failure by the overvoltage of the various elements to which an inverter voltage is added can be avoided.

The fuel cell system according to the present invention is suitable for avoiding a failure due to an overvoltage of an element.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 3 ... FC converter, 4 ... Battery, 5 ... Bat converter, 6 ... Traction inverter, 7 ... Traction motor, 8 ... Control part, V1, V2, V3 ... Voltage sensor .

Claims

A fuel cell that receives supply of the fuel gas and the oxidizing gas and generates power by an electrochemical reaction of the fuel gas and the oxidizing gas;
An animal power unit capable of charging the power generated by the fuel cell;
A power consuming device that consumes power from the fuel cell and the livestock power unit;
A first voltage converter disposed between the fuel cell and the power consuming device;
A second voltage conversion unit disposed between the livestock power unit and the power consuming device;
Determining means for determining whether or not a supply voltage supplied to the power consuming device abnormally increases;
An output limiting means for limiting the output of the first voltage converter when the determination means determines that the supply voltage is abnormally increased;
A fuel cell system comprising:
The determination means determines that the supply voltage is abnormally increased when the fuel cell is generating power and the supply voltage reaches a predetermined upper limit voltage value or more. 1. The fuel cell system according to 1.
3. The fuel cell system according to claim 2, wherein the predetermined upper limit voltage value is set within a range in which various elements to which the supply voltage is applied are not damaged.
The determination means determines that the supply voltage is abnormally increased when the fuel cell is generating power and the increase rate of the supply voltage reaches a predetermined upper limit increase rate or more. The fuel cell system according to claim 1.
The predetermined upper limit increase rate does not damage various elements to which the assumed voltage is applied even when the assumed voltage is supplied as the supply voltage after rising for a predetermined period according to the predetermined upper limit increase rate. The fuel cell system according to claim 4, wherein the fuel cell system is set within a range.
The output limiting means limits the output of the first voltage converter by reducing a varying duty ratio by controlling an on / off cycle of a switch included in the first voltage converter. The fuel cell system according to any one of claims 1 to 5, wherein:
The fuel cell system according to claim 6, wherein the output limiting means limits the output of the first voltage conversion unit by setting the duty ratio to zero.
8. The output limiting unit limits the output of the first voltage converter by stopping a switch included in the first voltage converter in an off state. The fuel cell system according to claim 1.