Circuit control device

Abstract

To provide a circuit control device by which large rush current can be prevented even if a switch failure or the like occurs in a switch type rush current preventing circuit.SOLUTION: A circuit control device controls the state of a circuit including a first path that is a current path from a fuel battery to a rear stage side, a first switch that is disposed in a region between a front stage side particular position in the first path and a rear stage side particular position on the rear stage and can be switched between ON and OFF, a second path that extends from the front stage side particular position to the rear stage side particular position and is a current path formed to have a higher electrical resistance than in the region, and a second switch that is disposed on the second path and can be switched between ON and OFF. The circuit control device detects the difference between a voltage value at a position on the front stage side of the front stage side particular position and a voltage value at a position on the rear stage side of the rear stage side particular position, and prohibits switching from the OFF state to the ON state of the first switch if a prescribed condition regarding the value of the difference is not satisfied.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a circuit control device for controlling a circuit having a current path.

Background Art

[0002] Conventionally, a power supply system that can perform home power generation using a fuel cell or the like and supply the home-generated power to consumers has been used. By using such a power supply system, a part of the commercial power (for example, thermal power generated from coal or LNG as a primary energy source) purchased by consumers from a power company can be switched to home-generated power, and as a result, it is also possible to reduce the amount of carbon dioxide emissions.

[0003] Furthermore, as a power supply system for performing the above-described home power generation, a system that enables self-operation during a power outage in a commercial power supply system has also been proposed. By realizing such a system that can maintain power supply independently during a power outage due to a natural disaster or the like, it is possible to reduce the adverse effects on social life and economic activities.

[0004] By the way, in a power supply system using a fuel cell, if a large inrush current flows from the fuel cell at the start of power generation, the fuel cell may be damaged due to fuel shortage. Therefore, an inrush current prevention circuit is provided to prevent such an inrush current from flowing. Patent Documents 1 to 3 disclose a power supply system including an inrush current prevention circuit for a fuel cell.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] The inrush current prevention circuits disclosed in Patent Documents 1 to 3 are switch-type inrush current prevention circuits in which a main current path and an inrush current prevention current path with a large electrical resistance are arranged in parallel, and switches capable of switching on / off are provided in each of these current paths.

[0007] According to the above-described switch-type inrush current prevention circuit, if each switch is appropriately controlled so that the current flows through the inrush current prevention current path immediately after the start of power generation and the current flows through the main current path after a predetermined time has elapsed, it is possible to prevent a large inrush current from flowing. However, if the current does not flow through the inrush current prevention current path after the start of power generation due to a defect in the switch or the like, there is a risk that a large inrush current will flow when the main current path is made conductive.

[0008] In view of the above problems, an object of the present invention is to provide a circuit control device that can prevent a large inrush current from flowing even if a defect occurs in a switch or the like in a switch-type inrush current prevention circuit.

Means for Solving the Problems

[0009] The circuit control device according to the present invention includes a first path that is a path for current from a fuel cell to the subsequent stage side, and is provided in a region between a specific position on the front stage side and a specific position on the subsequent stage side in the first path, and a first switch that can be switched between on and off, and extends from the specific position on the front stage side to the specific position on the subsequent stage side, and is formed to have a higher electrical resistance than the region, and a second path that is a path for the current, and a second switch that is provided in the second path and can be switched between on and off, and is a circuit control device that controls the state of the circuit, and detects a difference between a voltage value at a position on the front stage side of the specific position on the front stage side and a voltage value at a position on the subsequent stage side of the specific position on the subsequent stage side, and prohibits switching of the first switch from the off state to the on state when a predetermined condition regarding the value of the difference is not satisfied.

[0010] According to this configuration, even if a malfunction or the like of the switch occurs in the switch-type inrush current prevention circuit, it is possible to prevent a large inrush current from flowing. More specifically, as the above configuration, the predetermined condition may be a condition satisfied when the absolute value of the difference value is smaller than a predetermined value.

[0011] Furthermore, more specifically, as the above configuration, the circuit at the start of power generation of the fuel cell is set to a state where the first switch is in an off state and the second switch is in an on state, and when the predetermined condition is satisfied after a lapse of a predetermined time from the start of power generation, switching control for switching the first switch to an on state may be performed. Further, more specifically, as the above configuration, after performing the switching control, the second switch may be switched to an off state after a lapse of a predetermined time.

Effect of the Invention

[0012] According to the circuit control device according to the present invention, even if a malfunction or the like of the switch occurs in the switch-type inrush current prevention circuit, it is possible to prevent a large inrush current from flowing.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to the respective drawings.

[0015] <Outline of the Configuration of the Fuel Cell System> First, the outline of the configuration of the fuel cell system 100 according to the present embodiment will be described. FIG. 1 is an explanatory diagram showing the configuration of the fuel cell system 100. As shown in FIG. 1, the fuel cell system 100 includes a plurality of cell stacks (fuel cell stacks) 1, a reformer 2, a burner 3, an evaporator 4, an air preheater 5, an anode off-gas cooler 6, an anode off-gas condenser 7, a condenser fan 7a, a CO oxidizer (carbon monoxide oxidizer) 8, a condensed water recovery tank 9, a first raw fuel blower 10, a first air blower 11, a water pump 12, a second raw fuel blower 13, a second air blower 14, a power conditioner 15, a unit controller 16, a third air blower 17, a heater 18, a radiator fan 19, and an inrush current prevention circuit 90.

[0016] In the example of the present embodiment, a total of eight cell stacks 1 are provided, including those not shown in FIG. 1. Also, in the following description, the fuel cell system 100 may be simply referred to as the "power generation unit".

[0017] The fuel cell system 100 also includes each line (pipe line) of a raw fuel line La, a mixed gas line Lb, an anode fuel line Lc, an anode off-gas line Ld, a cathode air line Le, a cathode off-gas line Lf, a combustion gas line Lg, a burner cooling air line Lh, a reformed water line Li, a starting air line Lj, a cooling air line Lk, and a condensed water recovery line Lw.

[0018] The anode fuel line Lc includes a first distribution manifold Ma that serves as the main pipe for introducing anode fuel, and the cathode air line Le includes a second distribution manifold Mb that serves as the main pipe for introducing cathode air. These distribution manifolds Ma and Mb have an inlet and a plurality of outlets corresponding to each cell stack 1, and cause the fluid flowing into the inlet to flow out from each of the outlets.

[0019] The anode off-gas line Ld includes a first collection manifold Mc that serves as the main pipe for discharging anode off-gas, and the cathode off-gas line Lf includes a second collection manifold Md that serves as the main pipe for discharging cathode off-gas. These collection manifolds Mc and Md have a plurality of inlets and outlets corresponding to each cell stack 1, and cause the fluid flowing into each inlet to flow out from the outlet.

[0020] The combustion gas line Lg includes a heat radiation cylinder Za and a combustion gas pipe Zb. The cooling air line Lk includes a cooling pipe Zc and a collection pipe Lk1.

[0021] The raw fuel line La is a pipe connecting the fuel intake port E1 and the burner 3, and a second raw fuel blower 13 is arranged in this pipe. The second raw fuel blower 13 is a device that boosts the raw fuel gas Gf (for example, methane-containing gas such as city gas 13A) taken in from the fuel intake port E1 and sends it to the downstream side of the raw fuel line La, and is typically driven during the startup operation of the power generation unit.

[0022] The mixed gas line Lb is a pipe connecting the fuel intake port E2 and the reformer 2, and in this pipe, a first raw fuel blower 10, an evaporator 4, and a first bellows type expansion joint B1 are arranged in order from the upstream side. The first raw fuel blower 10 is a device that boosts the raw fuel gas Ga taken in from the fuel intake port E2 and sends it to the downstream side of the mixed gas line Lb, and is typically driven during the power generation operation of the power generation unit.

[0023] The anode fuel line Lc is a pipeline connecting the reformer 2 and the anodes of each cell stack 1. More specifically, the anode fuel line Lc includes, in order from the upstream side, a pipeline connecting the reformer 2 and the inlet of the first distribution manifold Ma, the first distribution manifold Ma, and eight pipelines (the branch pipes of the first distribution manifold Ma) connecting the outlets of the first distribution manifold Ma and the anodes of each cell stack 1.

[0024] The anode off-gas line Ld is a pipeline connecting the anodes of each cell stack 1 and the burner 3. More specifically, the anode off-gas line Ld includes, in order from the upstream side, eight pipelines (the branch pipes of the first collection manifold Mc) connecting the anodes of each cell stack 1 and the inlets of the first collection manifold Mc, the first collection manifold Mc, and a pipeline (hereinafter referred to as "pipeline Ld1") connecting the outlet of the first collection manifold Mc and the burner 3. In the middle of the pipeline Ld1, a second bellows expansion joint B2, an anode off-gas cooler 6, an anode off-gas condenser 7, and a gas-liquid separation section Sa are arranged in order from the upstream side.

[0025] The cathode air line Le is a pipeline connecting the air inlet E3 and the cathodes of each cell stack 1. More specifically, the cathode air line Le includes, in order from the upstream side, a pipeline (hereinafter referred to as "pipeline Le1") connecting the air inlet E3 and the inlet of the second distribution manifold Mb, the second distribution manifold Mb, and eight pipelines (the branch pipes of the second distribution manifold Mb) connecting the outlets of the second distribution manifold Mb and the cathodes of each cell stack 1.

[0026] In the middle of pipeline Le1, in order from the upstream side, a first air blower 11, an anode off-gas cooler 6, an air preheater 5, and a third bellows expansion joint B3 are arranged. The first air blower 11 is a device that pressurizes the air Aa taken in from the air inlet E3 and sends it to the downstream side of the cathode air line Le, and is typically driven during the power generation operation of the power generation unit. Further, in the pipeline Le1, a bypass path Le2 that bypasses the anode off-gas cooler 6 and the air preheater 5 is provided so as to connect the midpoint between the air inlet E3 and the anode off-gas cooler 6 and the midpoint between the air preheater 5 and the third bellows expansion joint B3.

[0027] The cathode off-gas line Lf is a pipeline that connects the cathode of each cell stack 1 and the burner 3. More specifically, the cathode off-gas line Lf includes, in order from the upstream side, eight pipelines (the branch pipes of the second collection manifold Md) that connect the cathode of each cell stack 1 and the inlets of the second collection manifold Md, the second collection manifold Md, and a pipeline that connects the outlet of the second collection manifold Md and the burner 3 (hereinafter referred to as "pipeline Lf1").

[0028] The combustion gas line Lg is a pipeline that connects the burner 3 and the gas discharge port D1. More specifically, the combustion gas line Lg includes, in order from the upstream side, a heat radiation cylinder Za, a pipeline that connects the heat radiation cylinder Za and the combustion gas pipe Zb, the combustion gas pipe Zb, and a pipeline that connects the combustion gas pipe Zb and the gas discharge port D1 (hereinafter referred to as "pipeline Lg1"). In the middle of the pipeline Lg1, in order from the upstream side, a fourth bellows expansion joint B4, an air preheater 5, a CO oxidizer 8, and an evaporator 4 are arranged.

[0029] The burner cooling air line Lh is a pipe connecting the pipe line Le1 and the starting air line Lj, and a flow rate adjusting means (such as an orifice) (not shown) is provided in this pipe line. More specifically described, the burner cooling air line Lh branches at an intermediate point of the pipe line Le1 connecting the first air blower 11 and the anode off-gas cooler 6, and merges into the starting air line Lj on the downstream side of the second air blower 14. It is configured such that a minute flow rate of air Ab flows toward the burner 3 when the first air blower 11 is driven. Note that the burner cooling air line Lh can be omitted depending on the combustion temperature of the burner 3.

[0030] The cooling air line Lk is a pipe connecting the air intake E5 and a predetermined location of the pipe line Lg1 (a location between the evaporator 4 and the gas discharge port D1), and in this pipe line, a third air blower 17 and a cooling pipe Zc are arranged in order from the upstream side. The third air blower 17 is a device that boosts the cooling air Ad taken in from the air intake E5 and sends it to the downstream side of the cooling air line Lk.

[0031] The reformed water line Li is a pipe connecting the condensed water recovery tank 9 and the evaporator 4, and a water pump 12 is arranged in this pipe line. The water pump 12 is a device that sends the condensed water Wb stored in the condensed water recovery tank 9 as reformed water Wa to the downstream side of the reformed water line Li.

[0032] The starting air line Lj is a pipe connecting the air intake E4 and the pipe line Lf1, and a second air blower 14 is arranged in this pipe line. The second air blower 14 is a device that boosts the air Ac taken in from the air intake E4 and sends it to the downstream side of the starting air line Lj, and is typically driven during the startup operation of the power generation unit.

[0033] The condensate recovery line Lw is a pipeline connecting the gas-liquid separation section Sa disposed in the middle of the pipeline Ld1 and the condensate recovery tank 9. The gas-liquid separation section Sa is a member that separates the condensate Wb generated in the anode off-gas condenser 7 from the anode off-gas Gd, and the separated condensate Wb flows down in the condensate recovery line Lw. The tip of the condensate recovery line Lw is opened to the gas phase portion without being immersed in the aqueous phase portion of the condensate recovery tank 9 so that the condensate amount does not increase or decrease under the influence of the water temperature of the stored condensate Wb. Note that the tip of the condensate recovery line Lw is not immersed in the aqueous phase portion in order not to change the flow rate of the anode off-gas Gd sent to the burner 3. In particular, this configuration is effective when the anode off-gas Gd after separating the condensate Wb is recycled to the primary side of the cell stack or used for power generation in the subsequent cell stack. For the gas-liquid separation section Sa, for example, a T-shaped pipe in which a straight pipe section is arranged horizontally and a branch pipe section is arranged downward is used. Also, a small-capacity cylindrical container erected vertically can be used as the gas-liquid separation section Sa.

[0034] The cell stack 1 is a power generation body composed of a solid oxide fuel cell (SOFC). The solid oxide fuel cell is a high-temperature operating fuel cell in which the solid electrolyte, anode, and cathode constituting the power generation cell are all ceramics, and a power generation unit in which a predetermined number of power generation cells are integrated via a metal interconnect material (also referred to as a separator material) is called a cell stack. The battery output of the cell stack 1 is fed after being adjusted by the power conditioner 15.

[0035] The reformer 2 reforms the raw fuel gas Ga using steam, generates a reformed gas Gc, and sends it to the subsequent stage side. The reformer 2 has a catalyst for steam reforming, reacts methane contained in the raw fuel gas Ga with steam, and generates a reformed gas Gc containing carbon monoxide and hydrogen. Although steam reforming is an endothermic reaction, the reformer 2 can stably generate the reformed gas Gc by heat supply from the burner 3.

[0036] The burner 3 burns the inflowing gas to generate heat, and discharges the combustion gas Gg generated by combustion into the combustion gas line Lg. The evaporator 4 is a device that indirectly heat-exchanges the reformed water Wa and the combustion gas Gg (heat source fluid). By heat-exchanging with the combustion gas Gg, it evaporates the reformed water Wa and at the same time plays a role in heating the raw fuel gas Ga.

[0037] The air preheater 5 and the anode off-gas cooler 6 are both heat exchangers that indirectly heat-exchange a low-temperature fluid and a high-temperature fluid. The air preheater 5 plays a role in preheating the air Aa in the cathode air line Le by heat-exchanging with the combustion gas Gg, and the anode off-gas cooler 6 plays a role in cooling the anode off-gas Gd by heat-exchanging with the air Aa in the cathode air line Le.

[0038] The anode off-gas condenser 7 uses the condenser fan 7a to cool the anode off-gas Gd and condenses the water vapor contained in the anode off-gas Gd. Note that the anode off-gas condenser 7 of this embodiment is an air-cooled heat exchanger, but instead, a water-cooled heat exchanger can be adopted, and thus it can also be a cogeneration type power generation unit in which heat recovery is performed.

[0039] The CO oxidizer 8 is a device that brings the harmful carbon monoxide contained in the combustion gas Gg into contact with a catalyst and converts it into harmless carbon dioxide. The CO oxidizer 8 does not operate when the oxidation reaction in the burner 3 is complete, and operates only when the oxidation reaction in the burner 3 is incomplete.

[0040] The condensate recovery tank 9 recovers the condensate Wb discharged from the gas-liquid separation section Sa and serves to make it reusable as reformed water Wa. The condensate recovery tank 9 is provided with a water level detector Sb and a drain valve Sc in order to adjust the water level of the stored reformed water Wa within a predetermined range. When the water level detector Sb detects the upper limit water level, the drain valve Sc is opened, while when the water level detector Sb detects the lower limit water level, the drain valve Sc is closed. In this way, the condensate recovery tank 9 is ensured to have the required amount of reformed water Wa. In order to prevent the anode off-gas Gd from leaking to the outside during the drainage operation of the reformed water Wa, the drainage position by the drain valve Sc is set near the bottom of the condensate recovery tank 9.

[0041] Also, as shown by the dashed line frame in FIG. 1, each cell stack 1, reformer 2, burner 3, each manifold Ma to Md, heat radiation cylinder Za, combustion gas pipe Zb, and cooling pipe Zc are arranged in the first region R1. The first region R1 is maintained at a temperature exceeding 600°C during the power generation operation of the power generation unit and independently maintains the heat balance of heat absorption and heat generation. On the other hand, the evaporator 4, air preheater 5, anode off-gas cooler 6, and CO oxidizer 8 are arranged in the second region R2. The second region R2 is maintained at a temperature lower than that of the first region R1 and higher than room temperature during the power generation operation of the power generation unit. The first region R1 and the second region R2 are each surrounded by a heat insulation box, and the power generation module is formed by integrating the two heat insulation boxes. The anode off-gas condenser 7, condenser fan 7a, condensate recovery tank 9, each blower 10, 11, 13, 14, 17, water pump 12, power conditioner 15, unit controller 16, heater 18, and heat dissipation fan 19 are arranged outside the power generation module (room temperature region). In addition, the above-described bellows type expansion pipe joints B1 to B4 are used to absorb the expansion and contraction of the pipes caused by the temperature change between the cold state and the operation state.

[0042] The power conditioner 15 is a device for converting the electric power generated by the cell stack 1 into a state where it can be used in business activities and social life, and is connected to the cell stack 1 via an inrush current prevention circuit 90 for preventing the flow of inrush current. The configuration and operation of the inrush current prevention circuit 90 will be described in detail again.

[0043] 11 FIG. 2 schematically illustrates the internal configuration of the power conditioner 15 and the connection state to peripheral devices. As shown in FIG. 2, the power conditioner 15 includes a first DC / DC converter 91, a second DC / DC converter 92, a first control circuit 93, a second control circuit 94, a grid-connected inverter 95, a grid-connected switch 96, and a self-contained outlet switch 97. An auxiliary equipment group AU for operating the power generation module and a load module LD including a heater 18 and a radiator fan 19 are connected to the power conditioner 15.

[0044] The auxiliary equipment group AU includes the first raw fuel blower 10, the first air blower 11, the water pump 12, the second raw fuel blower 13, the second air blower 14, the third air blower 17, the condenser fan 7a, and the spark rod of the burner 3 described above. In the self-sustaining operation mode of the power generation unit, the load module LD causes the heater 18 to generate heat and consume the surplus generated power of the cell stack 1, and the radiator fan 19 dissipates the heat generated from the heater 18. Further, as shown in FIG. 2, a self-contained outlet 200 and a switchboard 300 are connected to the power conditioner 15.

[0045] The first DC / DC converter 91 (boost circuit) boosts the DC voltage output from the cell stack 1. The second DC / DC converter 92 adjusts the DC voltage boosted by the first DC / DC converter 91 to a DC voltage suitable for driving the auxiliary equipment group AU.

[0046] The first control circuit 93 supplies the DC voltage regulated by the second DC / DC converter 92 to the auxiliary equipment AU and drives the auxiliary equipment AU appropriately. The second control circuit 94 supplies the DC voltage boosted by the first DC / DC converter 91 to the load module LD and drives the load module LD appropriately. The grid-connected inverter 95 (voltage conversion circuit) converts the DC voltage boosted by the first DC / DC converter 91 into an AC voltage synchronized with the commercial power supply system.

[0047] The grid-connected inverter 95 is electrically connected to, for example, the distribution board 300 of the commercial power supply system 400 installed in a building. The grid-connected inverter 95 and the distribution board 300 can be switched between parallel connection and disconnection via the grid connection switch 96. The commercial power supply system 400 and the demand equipment 500 are electrically connected to the distribution board 300. The demand equipment 500 includes a plurality of sub-distribution boards, and load devices such as lighting fixtures, power devices, or electrical outlets used in the building are electrically connected to each sub-distribution board.

[0048] Note that the auxiliary equipment AU is driven using commercial power during the startup operation and shutdown operation of the power generation unit, and is driven using the generated power during the power generation operation of the fuel cell system 100. In addition, the fuel cell system 100 is also capable of independent operation during a power outage, and the grid-connected inverter 95 is also electrically connected to the independent outlet 200 via the independent outlet switch 97. The independent outlet 200 can be connected to various power-consuming devices (such as electrical products used by consumers), and can supply independent operation power (output power generated by the power supply device 100 through independent operation) to the connected power-consuming devices. The independent operation power is preset within a range not exceeding the rated output power and not less than the minimum output power in the grid-connected operation mode based on the equipment information of the load module LD. Note that the minimum output power is set based on the minimum fuel supply amount that can maintain the thermal self-sufficiency of the power generation module and the minimum fuel utilization rate that can maintain the water self-sufficiency of the power generation module.

[0049] The unit controller 16 is a device that controls the operations of auxiliary equipment AU, the power conditioner 15, etc. (i.e., the power generation unit operation) according to a control program created and stored in advance. The unit controller 16 is provided with a communication unit for communicating with the outside of the power generation unit. Using this communication unit, remote operation of the power generation unit may be enabled.

[0050] <Overview of the Operation of the Fuel Cell System> Next, the overview of the operation of the fuel cell system 100 will be described with reference to FIG. 1. The raw fuel gas Ga supplied into the mixed gas line Lb from the fuel inlet E2 is sent to the subsequent stage by the action of the first raw fuel blower 10. In parallel with the supply of the raw fuel gas Ga, the reformed water Wa supplied into the reformed water line Li from the condensed water recovery tank 9 has its water volume adjusted by the water pump 12 and flows into the mixed gas line Lb.

[0051] The reformed water Wa flows into the evaporator 4 together with the raw fuel gas Ga in the mixed gas line Lb, and is heated by heat exchange in the evaporator 4 to become water vapor (superheated steam). The water vapor is mixed with the heated raw fuel gas Ga and flows into the reformer 2 as the mixed gas Gb.

[0052] The reformer 2 reforms the raw fuel gas Ga using the water vapor in the mixed gas Gb, generates the reformed gas Gc, and sends it to the subsequent stage. The reformed gas Gc sent out from the reformer 2 is distributed to the anodes of the respective cell stacks 1 through the anode fuel line Lc.

[0053] On the other hand, in parallel with the supply of the above-mentioned raw fuel gas Ga, air Aa is supplied from the air inlet E3 into the cathode air line Le. The air Aa in the cathode air line Le is sent to the subsequent stage by the action of the first air blower 11. This air Aa is heated by heat exchange in the anode off-gas cooler 6 and further heated by heat exchange in the air preheater 5, and then distributed to the cathodes of the respective cell stacks 1. Note that, for temperature adjustment of the air Aa, etc., it is also possible to make a part of the air Aa, i.e., the air Aa1, flow into the cathodes of the respective cell stacks 1 through the bypass path Le2.

[0054] Furthermore, in synchronization with the supply of air Aa to the cathode, air Ab is supplied into the burner cooling air line Lh. The air Ab in the burner cooling air line Lh is sent to the burner 3 by the action of the first air blower 11. This air Ab acts as a coolant for reducing the combustion temperature of the burner 3.

[0055] Each cell stack 1 generates electricity using the reformed gas Gc flowing into the anode and the air Aa flowing into the cathode, discharges the anode off-gas Gd from the anode to the anode off-gas line Ld, and discharges the cathode off-gas Ge from the cathode to the cathode off-gas line Lf. The anode off-gas Gd contains fuel components that were unreacted at the anode, and the cathode off-gas Ge contains oxygen that was unreacted at the cathode.

[0056] The anode off-gas Gd discharged from each cell stack 1 to the anode off-gas line Ld is collected in the first collection manifold Mc, then cooled by heat exchange in the anode off-gas cooler 6, and flows into the anode off-gas condenser 7. In the anode off-gas condenser 7, the anode off-gas Gd is cooled to below the dew point temperature, and the water vapor contained in the anode off-gas Gd condenses.

[0057] The anode off-gas Gd that has passed through the anode off-gas condenser 7 is sent to the gas-liquid separation section Sa for gas-liquid separation, and the condensed water Wb is recovered in the condensed water recovery tank 9. The condensed water Wb recovered in the condensed water recovery tank 9 is reused as the reformed water Wa as described above. Note that the non-condensed portion of the anode off-gas Gd (the anode off-gas Gd after gas-liquid separation) is sent to the burner 3.

[0058] The cathode off-gas Ge discharged from each cell stack 1 to the cathode off-gas line Lf is collected by the second collection manifold Md, and then mixed with the air Ab flowing in through the burner cooling air line Lh in the pipeline Lf1, and sent to the burner 3. Further, to the burner 3, according to the operating state of the system, the raw fuel gas Gf supplied from the fuel inlet E1 is sent through the raw fuel line La, and the air Ac supplied from the air inlet E4 is sent through the starting air line Lj.

[0059] The burner 3 has the first burner gas Gx which is the raw fuel gas Gf and / or the anode off-gas Gd, and the second burner gas Gy which is the air Ac and / or the cathode off-gas Ge flowing in, and burns these to generate heat. That is, the first burner gas Gx is a mixed gas of the raw fuel gas Gf and the anode off-gas Gd, or in a state of either the raw fuel gas Gf or the anode off-gas Gd, and which state it is in can vary depending on the operating state of the power generation unit and the like. Also, the second burner gas Gy is a mixed gas of the air Ac and the cathode off-gas Ge, or in a state of either the air Ac or the cathode off-gas Ge, and which state it is in can vary depending on the operating state of the system and the like. That is, according to the startup operation, power generation operation (full load operation or partial load operation), shutdown operation, etc. of the power generation unit, the supply gas to the burner 3 changes its state appropriately.

[0060] Note that the raw fuel gas Gf is a kind of hydrocarbon-containing gas. On the other hand, the air Ac is a kind of oxidant-containing gas. During the combustion operation of the burner 3, air Ab is continuously supplied from the burner cooling air line Lh to adjust the combustion temperature.

[0061] The combustion gas Gg generated by combustion in the burner 3 is sent to the combustion gas line Lg and passes through the heat radiation cylinder Za, the combustion gas pipe Zb, the air preheater 5, the CO oxidizer 8, and the evaporator 4 in sequence, and is discharged to the outside of the power generation module. The heat radiation cylinder Za and the combustion gas pipe Zb are arranged so that the reformer 2 can be effectively heated using the combustion gas Gg. Further, the combustion gas Gg in the combustion gas line Lg is utilized for heat exchange when passing through the air preheater 5 and the evaporator 4, and when carbon monoxide is contained, the carbon monoxide is converted to carbon dioxide when passing through the CO oxidizer 8.

[0062] Also, the cooling air Ad supplied from the air inlet E5 to the cooling air line Lk plays a role in cooling the inside of the power generation module when passing through the cooling pipe Zc. The cooling pipe Zc is installed in the vicinity of the cell stack 1, and the cell stack 1 can be effectively cooled by the cooling air Ad. Then, the cooling air Ad is finally discharged to the outside of the power generation module through the collection pipe Lk1 together with the combustion gas Gg.

[0063] Also, in the fuel cell system 100, the amount of heat (temperature) inside the power generation module is controlled by adjusting the flow rate of the cooling air Ad introduced into the cooling pipe Zc. As an example, when the temperature inside the power generation module (for example, the maximum value of the surface temperature of the end plate of each cell stack 1) exceeds the upper limit temperature, the fuel cell system 100 drives the third air blower 17 and controls the rotation speed of the third air blower 17 so that the temperature inside the power generation module becomes the target temperature (a temperature lower than the upper limit temperature by a predetermined temperature). Further, when the rotation speed below the lower limit value continues for a predetermined time, the fuel cell system 100 stops the third air blower 17. Note that the greater the rotation speed of the third air blower 17, the greater the flow rate of the cooling air Ad introduced into the cooling pipe Zc. Such control operations may be performed by the unit controller 16.

[0064] Note that the cooling pipe Zc installed near the cell stack 1 can also be used to heat up the cell stack 1 during the startup operation of the power generation unit. Specifically, in the startup operation of the power generation unit, first, the second fuel blower 13 and the second air blower 14 are driven to burn the burner 3. The combustion gas Gg generated by this combustion flows through the heat radiation cylinder Za and the combustion gas pipe Zb, and heats up the cold reformer 2 from the outside by radiative heat transfer while flowing through them. Further, the combustion gas Gg becomes the heat source of the evaporator 4 and generates water vapor from the reforming water Wa. This water vapor flows through the cold reformer 2 and the cell stack 1 in sequence, and heats up these devices from the inside by heat conduction. If there is residual heat in the combustion gas Gg discharged from the evaporator 4, the combustion gas Gg is allowed to flow from the pipeline Lg1 to the collecting pipe Lk1. As a result, the combustion gas Gg flows through the cooling pipe Zc, so that the cold cell stack 1 can be heated from the outside by radiative heat transfer and its temperature can be raised.

[0065] In addition, the unit controller 16 constantly monitors the presence or absence of a power outage in the commercial power supply system. When a power outage is detected, it turns off the system connection switch 96 and turns on the outlet socket switch 97. As a result, the fuel cell system 100 shifts from the grid-connected operation mode to the stand-alone operation mode. When an electrical device is connected to the outlet socket 200, the output power of the power conditioner 15 can be supplied as the stand-alone operation power to the electrical device. When the commercial power supply system resumes power after a power outage, the unit controller 16 shifts the power supply device 100 from the stand-alone operation mode to the grid-connected operation mode.

[0066] When the supply amount of the stand-alone operation power exceeds the consumption amount in the stand-alone operation mode, the fuel cell system 100 causes the load module LD to consume the surplus of the stand-alone operation power. The adjustment of the power consumption amount of the load module LD can be realized by adjusting the calorific value of the heater 18 (for example, adjusting the number of heaters to be energized, or adjusting the on / off duty ratio of the energization).

[0067] FIG. 3 is a perspective view of the fuel cell system 100 (power generation unit). The fuel cell system 100 is configured such that each element such as a power generation module is housed in a housing 100a. A load module LD is disposed above the housing 100a.

[0068] <Inrush current prevention circuit> Next, the inrush current prevention circuit 90 described above will be explained. When a large inrush current flows at the start of power generation of the fuel cell stack 1 (fuel cell), the fuel cell stack 1 may be damaged due to fuel depletion. Therefore, in the fuel cell system 100, an inrush current prevention circuit 90 is provided that can prevent a large inrush current from flowing.

[0069] FIG. 4 is a schematic configuration diagram of the inrush current prevention circuit 90. As shown in this figure, the inrush current prevention circuit 90 includes a first path LN1, a first switch SW1, a second path LN2, a second switch SW2, and a resistor RE, and is configured as a switch-type inrush current prevention circuit. The inrush current prevention circuit 90 may be built into the power conditioner 15. Further, in the fuel cell system 100, a controller CON for controlling the state of the inrush current prevention circuit 90 is provided. The controller CON may be integrated with the unit controller 16, or may be a device provided separately from the unit controller 16 (for example, a built-in controller of the power conditioner 15).

[0070] The first path LN1 is the main current path from the fuel cell stack 1 to the subsequent stage side, and is arranged to connect the fuel cell stack 1 and the power conditioner 15 (first DC / DC converter 91). The first switch SW1 is provided in a region between a predetermined position P1 (hereinafter referred to as the front stage side specific position P1) and a predetermined position P2 on the subsequent stage side (hereinafter referred to as the subsequent stage side specific position P2) in the first path LN1, and is configured to be switchable between on and off. The first switch SW1 conducts the first path LN1 when in the on state and cuts off the first path LN1 when in the off state.

[0071] The second path LN2 extends from the front-stage specific position P1 to the rear-stage specific position P2, and is a current path for preventing inrush current formed to have a higher electrical resistance than the above-described region (the region between the front-stage specific position P1 and the rear-stage specific position P2 in the first path LN1). In the example of the present embodiment, the second path LN2 is formed to have a higher resistance than the said region by providing a resistor RE. The second switch SW2 is provided in the second path and is configured to be switchable between on and off. The second switch SW2 conducts the second path LN2 when in the on state and cuts off the second path LN2 when in the off state.

[0072] The controller CON can detect the difference between the voltage value Va at a position on the front stage side of the front-stage specific position P1 and the voltage value Vb at a position on the rear stage side of the rear-stage specific position P2. The voltage value Va is detected, for example, by connecting a first signal converter to the region between the cell stack 1 and the front-stage specific position P1, and corresponds to the output voltage of the cell stack 1. On the other hand, the voltage value Vb is detected, for example, by connecting a second signal converter to the region between the rear-stage specific position P2 and the first DC / DC converter 91, and corresponds to the input voltage of the first DC / DC converter 91. The first signal converter and the second signal converter each convert the input DC voltage signal into a unified signal and output it to the controller CON. Note that each signal converter may be built into the power conditioner 15.

[0073] When the power generation of the cell stack 1 (fuel cell) starts, the controller CON controls the state of the inrush current prevention circuit 90 so as to prevent the generation of an inrush current. The control content of the state of the inrush current prevention circuit 90 will be described more specifically with reference to the flowchart shown in FIG. 5. Before the power generation of the cell stack 1 starts (the state in which the power generation unit is on standby with a power generation output of zero, which is called hot standby), both the first switch SW1 and the second switch SW2 are controlled to be in the off state. When the unit controller 16 receives a power generation start command, the controller CON keeps the first switch SW1 in the off state and controls the second switch SW2 to be in the on state. That is, at this point, each switch SW1, SW2 is controlled to be in the state shown in FIG. 6, and when the current sweep by the power conditioner 15 is executed, the power generation (electrochemical reaction of the reformed gas and oxygen) of the cell stack 1 starts.

[0074] When the power generation of the cell stack 1 starts, the controller CON waits for the timing when a predetermined time Ta has elapsed since the start of power generation (start of current sweep) (step S1). When the predetermined time Ta has elapsed (Yes in step S1), the controller CON determines whether the absolute value Vd of the difference between the voltage value Va and the voltage value Vb is smaller than a predetermined value Vs (step S2).

[0075] If the absolute value Vd is smaller than the predetermined value Vs (Yes in step S2), the controller CON switches the first switch SW1 to the on state (step S3) and then waits for the timing when a predetermined time Tb (1 second in the example of this embodiment) has elapsed (step S4). When the predetermined time Tb has elapsed (Yes in step S4), the controller CON switches the second switch SW2 to the off state (step S5).

[0076] On the other hand, when the absolute value Vd is not less than the predetermined value Vs (No in step S2), the controller CON executes a predetermined abnormality handling process without switching the first switch SW1 to the on state (step S6). As described above, by controlling the state of the inrush current prevention circuit 90, it is possible to prevent a large inrush current from flowing and to appropriately respond even when the second switch SW2 does not operate normally.

[0077] More specifically, immediately after the power generation of the cell stack 1 starts, since the first switch SW1 is in the off state and the second switch SW2 is in the on state, during normal operation, as shown in FIG. 6, the current flowing from the cell stack 1 to the power conditioner 15 passes through the second path LN2 provided with the resistor RE. Therefore, it is possible to prevent a situation where a large inrush current flows after the start of power generation of the cell stack 1 and the cell stack 1 is damaged due to fuel shortage. The resistance value of the resistor RE is appropriately set so that such a situation does not occur. The colored arrows in FIG. 6 (the same applies to FIGS. 7 and 8 described later) schematically show the paths through which current can flow.

[0078] After the start of power generation of the cell stack 1, during normal operation (when the second switch SW2 operates normally and is in the on state), the voltage of the cell stack 1 is applied also at a position on the downstream side of the downstream-side specific position P2, and the voltage value Vb increases. Therefore, the voltage value Va and the voltage value Vb become substantially equal, and the absolute value Vd of the difference between them becomes smaller than the predetermined value Vs. Conversely, during an abnormality (when the second switch SW2 does not operate normally and is not in the on state), a situation occurs where current does not flow through the second path LN2 after the start of power generation of the cell stack 1. In this case, the voltage value Vb does not increase, and the absolute value Vd of the difference between the voltage value Va and the voltage value Vb does not become smaller than the predetermined value Vs.

[0079] In this way, it is possible to distinguish between normal and abnormal conditions by determining whether the absolute value Vd is smaller than the predetermined value Vs. The predetermined value Vs is a value set so that such discrimination is appropriately performed, and in the example of the present embodiment, it is set to 10V.

[0080] Therefore, when a predetermined time Ta has elapsed since the start of power generation of the cell stack 1, if the absolute value Vd is smaller than a predetermined value Vs (Yes in step S2), that is, if it can be determined as normal, the controller CON switches the first switch SW1 to the on state to make the inrush current prevention circuit 90 in the state shown in FIG. 7, and further, after the elapse of a predetermined time Tb, switches the second switch SW2 to the off state to make the inrush current prevention circuit 90 in the state shown in FIG. 8 (steps S3 to S5). The predetermined time Ta is set to a time that can surely avoid a situation where a large inrush current flows through the first path LN1, and is set to 12 seconds in the example of this embodiment.

[0081] The state of the inrush current prevention circuit 90 shown in FIG. 8 is a state when the power generation unit operates in the parallel operation mode or the independent operation mode, and it is a state in which current can flow from the cell stack 1 to the power conditioner 15 through the first path LN1 having a smaller electrical resistance than the second path LN2. In this embodiment, the inrush current prevention circuit 90 is shifted from the state shown in FIG. 6, through the state shown in FIG. 7, to the state shown in FIG. 8. Thereby, compared with the case where the inrush current prevention circuit 90 is shifted from the state shown in FIG. 6 directly to the state shown in FIG. 8 without passing through the state shown in FIG. 7, it is possible to more surely avoid a situation where both switches SW1 and SW2 are simultaneously in the off state.

[0082] When stopping the power generation of the cell stack 1, the unit controller 16 terminates the current scavenging by the power conditioner 15, and the controller CON switches the first switch SW1 to the off state while keeping the second switch SW2 in the off state. Thereby, the power generation unit shifts to the hot standby state.

[0083] On the other hand, when the absolute value Vd is not less than the predetermined value Vs (No in step S2), that is, when it can be determined as an abnormal situation, if the first switch SW1 is switched to the on state, the first switch SW1 changes from the off state of both switches SW1 and SW2 to the on state, and there is a risk of a large current flowing through the first path LN1. That is, in this case, since the initial current (limiting current) is not flowing through the second path LN2, there is a risk of an inrush current flowing when the first switch SW1 is switched to the on state. Therefore, the controller CON executes an abnormality countermeasure process without switching the first switch SW1 to the on state (step S6).

[0084] In this way, when the condition of step S2 regarding the difference value between the voltage value Va and the voltage value Vb (hereinafter, may be referred to as "predetermined condition α" for convenience) is not satisfied, the controller CON prohibits switching the first switch SW1 from the off state to the on state. That is, even though the first switch SW1 is controlled to be in the off state and the second switch SW2 is controlled to be in the on state, when the absolute value Vd of the difference value between the voltage value Va and the voltage value Vb is greater than the predetermined value Vs, it is determined that the second switch SW2 has failed in the off state, and switching the first switch SW1 to the on state is prohibited. Thereby, a large current flowing through the first path LN1 is prevented beforehand.

[0085] Note that examples of the abnormality countermeasure process in step S6 include a process of issuing an alarm for notifying a customer or the like of an abnormality and executing a shutdown operation of the power generation unit. However, the specific content of the abnormality countermeasure process is not limited to this.

[0086] <Effects of the Present Invention, etc.> As described above, the controller CON is a circuit control device that controls the state of the inrush current prevention circuit 90, detects the difference between the voltage value Va at a position on the front stage side of the front stage specific position P1 and the voltage value Vb at a position on the rear stage side of the rear stage specific position P2, and prohibits switching the first switch SW1 from the off state to the on state when the predetermined condition α regarding the difference value is not satisfied.

[0087] Therefore, according to the controller CON, even if a problem occurs in the second switch SW2 in the switch-type inrush current prevention circuit 90, it is possible to prevent a large inrush current from flowing. The predetermined condition α in this embodiment is a condition satisfied when the absolute value Vd of the difference between the voltage value Va and the voltage value Vb is smaller than the predetermined value Vs.

[0088] Also, when starting power generation of the cell stack 1, the controller CON sets the inrush current prevention circuit 90 such that the first switch SW1 is in the off state and the second switch SW2 is in the on state. When the predetermined condition α is satisfied after the elapse of the predetermined time Ta from the start of power generation, the controller CON performs switching control to switch the first switch SW1 to the on state. Thereby, while preventing a large inrush current from flowing, it is possible to make the first path LN1 function as the main current path.

[0089] Further, after performing the above switching control, the controller CON switches the second switch SW2 to the off state when the predetermined time Tb has elapsed. Thereby, it is possible to surely avoid a situation where both switches SW1 and SW2 are in the off state at the same time.

[0090] As described above, the embodiments of the present invention have been described. However, the configuration of the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the invention. That is, the above embodiments should be considered as illustrative in all respects and not restrictive. The technical scope of the present invention is shown not by the description of the above embodiments but by the scope of the claims, and it should be understood that all modifications belonging to the meaning and scope equivalent to the scope of the claims are included.

[0091] <Contribution to the United Nations Sustainable Development Goals (SDGs)> The power supply device and power supply system according to the present disclosure can contribute to the achievement of Goal 13, "Take urgent action to combat climate change" and Goal 11, "Sustainable cities and communities" of the SDGs (Sustainable Development Goals).

Industrial Applicability

[0092] The present invention is applicable to a circuit control device that controls a circuit having a current path.

Explanation of Signs

[0093] 1 Cell stack 2 Reformer 2a Reaction vessel 3 Burner 4 Evaporator 5 Air preheater 6 Anode off-gas cooler 7 Anode off-gas condenser 8 CO oxidizer 9 Condensate recovery tank 10 First raw fuel blower 11 First air blower 12 Water pump 13 Second raw fuel blower 14 Second air blower 15 Power conditioner 16 Unit controller 17 Third air blower 18 Heater 19 Heat dissipation fan 91 First DC / DC converter 92 Second DC / DC converter 93 First control circuit 94 Second control circuit 95 Grid-connected inverter 96 Grid-connected switch 97 Stand-alone outlet switch 100 Fuel cell system 100a Housing 200 Stand-alone outlet 300 Switchboard 400 Commercial Power Supply System 500 Required Equipment 600 Socket Unit Aa~Ac Air Ad Cooling Air AU Auxiliary Equipment B1 First Bellows-Type Expansion Joint B2 Second Bellows-Type Expansion Joint B3 Third Bellows-Type Expansion Joint B4 Fourth Bellows-Type Expansion Joint CON Controller E1, E2 Fuel Inlet E3, E4, E5 Air Inlet Ga Raw Fuel Gas Gb Mixed Gas Gc Reformed Gas Gd Anode Off-Gas Ge Cathode Off-Gas Gf Raw Fuel Gas Gg Combustion Gas La Raw Fuel Line Lb Mixed Gas Line Lc Anode Fuel Line Ld Anode Off-Gas Line Le Cathode Air Line Lf Cathode Off-Gas Line Lg Combustion Gas Line Lh Burner Cooling Air Line Li Stack Cooling Air Line Lj Reformed Water Line Lk Cooling Air Line Lka First Cooling Air Line Lkb Second Cooling Air Line LD Load Module LN1 First Route LN2 Second Route Ma First Distribution Manifold Mb Second Distribution Manifold Mc First Collection Manifold Md Second Collection Manifold RE Resistor SW1 First Switch SW2 Second Switch Wa Modified Water Za Heat Radiation Tube Zb Combustion Gas Pipe Zc Cooling Pipe

Claims

1. a first path that serves as a path for current from the fuel cell to the rear stage side; a first switch provided in a region between a specific position on the front stage side and a specific position on the rear stage side in the first path, the on / off state of which is switchable; a second path that serves as the path for the current, extending from the specific position on the front stage side to the specific position on the rear stage side and formed to have a higher electrical resistance than the region; a circuit control device for controlling the state of a circuit including a second switch provided in the second path, the on / off state of which is switchable, the circuit control device detecting a difference between a voltage value at a position on the front stage side of the specific position on the front stage side and a voltage value at a position on the rear stage side of the specific position on the rear stage side, and prohibiting switching of the first switch from the off state to the on state when a predetermined condition regarding the value of the difference is not satisfied. detecting a difference between a voltage value at a position on the front stage side of the specific position on the front stage side and a voltage value at a position on the rear stage side of the specific position on the rear stage side; a circuit control device that prohibits switching of the first switch from the off state to the on state when a predetermined condition regarding the value of the difference is not satisfied.

2. The circuit control device according to claim 1, wherein the predetermined condition is a condition satisfied when an absolute value of the value of the difference is smaller than a predetermined value.

3. setting the circuit at the start of power generation of the fuel cell to a state in which the first switch is in the off state and the second switch is in the on state, and performing switching control to switch the first switch to the on state when the predetermined condition is satisfied after a lapse of a predetermined time from the start of power generation. The circuit control device according to claim 1 or claim 2, which performs switching control to switch the first switch to the on state when the predetermined condition is satisfied after a lapse of a predetermined time from the start of power generation.

4. The circuit control device according to claim 3, which switches the second switch to the off state after a lapse of a predetermined time after performing the switching control.

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