Control systems and methods for fuel cell stacks

Abstract

This invention provides a control system and method for a fuel cell stack. The system includes multiple fuel cell stacks, a secondary battery, a monitoring device, and a control device. Each fuel cell stack has an independent power output that can be started or stopped, and the power output terminal of each fuel cell stack is connected in parallel to a load terminal to provide power. The secondary battery is connected to the power output terminal of the fuel cell stack via a power transmission path. The monitoring device monitors the electrical parameters of the power transmission path. The control device receives signals of the electrical parameters from the monitoring device and, when the electrical parameters exceed a predetermined upper limit value, outputs a first control signal to shut down the power output of at least one of the fuel cell stacks; or, when the electrical parameters are below a predetermined lower limit value, outputs a second control signal to start the power output of at least one of the fuel cell stacks.

Description

Technical Field

[0001] This invention relates to a related technology of fuel cell stacks, and more particularly to a control system and method for fuel cell stacks. Background Technology

[0002] Fuel cell power systems, by directly supplying the load's power demand, not only reduce energy loss through power converters but also alleviate the burden of thermal management. Their use in DC power systems for unmanned aerial vehicles (UAVs) offers significant benefits in improving energy density. However, this power supply method causes the fuel cell's output voltage to vary considerably depending on changes in the load's power demand, exceeding the input voltage range of the load system. This variation is particularly pronounced when the UAV's payload varies, further widening the power requirements and making maintaining the fuel cell's output voltage within the desired range a more challenging issue.

[0003] In a power supply system where fuel cells directly supply the load demand, the key factor in maintaining the load voltage within the expected range is the control of the fuel cell output power. One effective method is to dynamically adjust the output power to meet the changing load demand by individually starting and stopping the power supply of multiple fuel cell modules.

[0004] However, how to adjust the number of fuel cell stacks in a timely manner in response to load changes, reduce the burden of load power demand on the secondary battery during the start-up / shutdown process of the fuel cell, and ensure smooth power supply quality has become a key technology currently under research. Summary of the Invention

[0005] This invention relates to a control system and method for a fuel cell stack, which can dynamically adjust the power supply start-up or shutdown of the fuel cell stack to reduce the charging or discharging current required by the secondary battery, thereby significantly reducing the system load.

[0006] According to an embodiment of the present invention, the control system of a fuel cell stack includes multiple fuel cell stacks, a secondary battery, a monitoring device, and a control device. Each fuel cell stack has an independent power output that can be started or stopped, and the power output terminal of each fuel cell stack is connected in parallel to a load terminal to provide power. The secondary battery is connected to the power output terminal of the fuel cell stack via a power transmission path. The monitoring device is used to monitor the electrical parameters of the power transmission path. The control device receives signals of the electrical parameters from the monitoring device, and when the electrical parameters exceed a predetermined upper limit value, outputs a first control signal to shut down the power output of at least one of the fuel cell stacks; and when the electrical parameters are below a predetermined lower limit value, outputs a second control signal to start the power output of at least one of the fuel cell stacks.

[0007] According to another embodiment of the present invention, a fuel cell stack control method is used to control multiple fuel cell stacks, wherein each fuel cell stack has an independently start-up or shutdown power output, and the power output terminals of the multiple fuel cell stacks are connected in parallel to a load terminal to provide power. The control method includes providing a secondary battery connected to the power output terminal of the fuel cell stack via a power transmission path, monitoring electrical parameters of the power transmission path using a monitoring device, receiving the electrical parameters using a control device, and performing one of the following steps based on the electrical parameters: When the electrical parameters exceed a predetermined upper limit value, outputting a first control signal to shut down the power output of at least one of the fuel cell stacks; When the electrical parameters are below a predetermined lower limit value, outputting a second control signal to start the power output of at least one of the fuel cell stacks.

[0008] Based on the above, this invention does not require monitoring the load or the status of individual fuel cells (stacks). It can control the system to respond in real-time to load changes, starting or stopping the power generation of some parallel fuel cell stacks, thus controlling the output voltage of multiple parallel fuel cell stacks within a specific expected range. Particularly useful in hybrid power supply systems where auxiliary power is provided by secondary batteries, it controls the output power of the fuel cell stacks to keep the discharge or charging power of the secondary batteries within an appropriate range.

[0009] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings. Attached Figure Description

[0010] Figure 1A This is a block diagram of a control system for a fuel cell stack according to a first embodiment of the present invention.

[0011] Figure 1B This is a graph showing the power demand of unmanned aerial vehicles.

[0012] Figure 1C It is a graph showing the change of the upper and lower power limits with the state of charge in the first embodiment.

[0013] Figure 1D This is a block diagram of a control system for another fuel cell stack according to the first embodiment.

[0014] Figure 1E This is a block diagram of another fuel cell stack control system according to the first embodiment.

[0015] Figure 2 This is a flowchart illustrating the control method of the fuel cell stack in the first embodiment.

[0016] Figure 3 This is a block diagram of a specific example of the control system of the fuel cell stack in the first embodiment.

[0017] Figure 4 This is a block diagram of a control system for a fuel cell stack according to a second embodiment of the present invention.

[0018] Figure 5 This is a block diagram of a control system for a fuel cell stack according to a third embodiment of the present invention.

[0019] Figure 6 This is a block diagram of a control system for a fuel cell stack according to a fourth embodiment of the present invention.

[0020] Figure 7 This is a block diagram of a control system for a fuel cell stack according to a fifth embodiment of the present invention.

[0021] Figure 8 The fifth embodiment's fuel cell stack's stage of charge (SOC) and output voltage V Batt The curve between them.

[0022] Explanation of reference numerals in the attached figures

[0023] 100: Control system of fuel cell stack

[0024] 102: Multiple fuel cell stacks

[0025] 104: Secondary battery

[0026] 106, 602: Monitoring devices

[0027] 108: Control device

[0028] 110: Power output terminal

[0029] 112: Load end

[0030] 114: Power Transmission Path

[0031] 200, 202, 204, 206, 208, 210, 212: Step 300: Fuel Cell Stack

[0032] 302: BOP

[0033] 304: Intake valve

[0034] 306: Fuel Tank

[0035] 308: Gas fuel supply pipe

[0036] 310: Pressure regulating device

[0037] 502: Device for monitoring the power input to a secondary battery

[0038] 700: Device for monitoring the output voltage of a secondary battery

[0039] C1, C2, C3: DC-DC voltage converter

[0040] D1: Unidirectional current control element

[0041] I in Input current of the secondary battery

[0042] P in Input power of the secondary battery

[0043] S: Electrical parameters

[0044] S1: Pre-set upper limit value

[0045] S2: Preset lower limit value

[0046] V1, V2, V3, V4, V5, V6, V Batt Output voltage of the secondary battery

[0047] V FC Output voltage of fuel cell stack Detailed Implementation

[0048] Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same element references are used in the drawings and description to denote the same or similar parts.

[0049] Figure 1A This is a block diagram of a control system for a fuel cell stack according to a first embodiment of the present invention.

[0050] Please refer to Figure 1A The fuel cell stack control system 100 of this embodiment includes multiple fuel cell stacks 102, secondary batteries 104, a monitoring device 106, and a control device 108. Each fuel cell stack 102 has an independent start-up or shutdown power output, and the power output terminal 110 of the fuel cell stack 102 is connected in parallel to a load terminal 112 to provide variable load power. The secondary battery 104 is connected to the power output terminal 110 of the fuel cell stack 102 via a power transmission path 114. The secondary battery 104 can provide auxiliary power or receive the remaining power from the fuel cell stack 102 after providing variable load power for charging. The monitoring device 106 is used to monitor the electrical parameters S of the power transmission path 114, where the power transmission path 114 refers to the path between the secondary battery 104 and the power output terminal 110, and the electrical parameters S may include the power P input to the secondary battery 104, depending on the monitoring device or conditions. in The state of charge (SOC) of the secondary battery 104 and the output voltage V of the secondary battery 104. BattInput current I of secondary battery 104 in The output voltage V of fuel cell stack 102 FC After receiving the electrical parameter S, the control device 108 will output a first control signal to shut down the power output of at least one group in the fuel cell stack 102 when the electrical parameter S exceeds a predetermined upper limit value S1; or, when the electrical parameter S is lower than a predetermined lower limit value S2, it will output a second control signal to start the power output of at least one group in the fuel cell stack 102. In one embodiment, the secondary battery 104 is, for example, a lithium battery (lithium polymer battery LIPO, lithium-ion battery Li-ion, or solid electrolyte lithium battery, etc.) or other high-power rechargeable batteries (including lead-acid batteries, nickel-cadmium batteries NiCd, nickel-metal hydride batteries NiMH, or electrical double-layer capacitors EDLC, etc.). The monitoring device 106, depending on the electrical parameter S to be monitored, may include, but is not limited to, various power monitoring instruments and equipment such as voltage detectors, voltage-power detectors, current detectors, power meters, watt-hour meters, or residual power estimators. The control device 108 may be, for example, a processor, a computer, or other equipment.

[0051] In one embodiment, the variable load is a device with large load variations, such as an unmanned aerial vehicle. For example, such as Figure 1B As shown, as the power demand of the unmanned aerial vehicle (UAV) increases linearly over time, the output power of the fuel cell stack 102 increases in a stepped manner (fuel cell power generation) to meet the power needs of the UAV. The electrical parameters S (such as output / input power) of the power transmission path 114 are as follows: Figure 1B The system comprises dense and sparse point distribution blocks, where the dense point distribution blocks represent the charging power (at which point the output power of fuel cell stack 102 exceeds the power demand of the UAV, so the excess power is used to charge the secondary battery 104), and the sparse point distribution blocks represent the discharging power (at which point the output power of fuel cell stack 102 is less than the power demand of the UAV, so the insufficient power is provided by the discharge of the secondary battery 104). This system adapts to changes in the power demand of the UAV's motor load and activates the power output of each fuel cell stack in the multiple fuel cell stacks 102 according to the electrical parameter S. In situations such as tailwind / headwind, deceleration / acceleration, or changes in flight altitude, the motor load power of the UAV will also differ. Therefore, the control system and method of this invention can respond instantly to load changes and activate or deactivate some fuel cell stacks in the multiple fuel cell stacks 102.

[0052] In one embodiment, refer to Figure 1A , Figure 1C The electrical parameter S is the power (charging power) input to the secondary battery 104. inThe predetermined upper limit value S1 is the upper limit value of (charging) power, and the predetermined lower limit value S2 is the lower limit value of (discharging) power. Therefore, the charging power is positive (S1>0), and the discharging power is negative (S2<0). Furthermore, the monitoring device 106 can also estimate the state of charge (SOC) of the secondary battery 104, and when the SOC is greater than an upper limit value SOC2, the aforementioned upper limit value of power is reduced; and when the SOC is less than an lower limit value SOC1, the aforementioned lower limit value of power is increased. For example, such as... Figure 1C As shown, the original S1 is set to 600W. Once the SOC exceeds the upper limit of the state of charge SOC2 (e.g., 70%), S1 linearly decreases from 600W, i.e., the upper limit of charging power S1(SOC=80%) = 400W; S1(SOC=90%) = 200W; S1(SOC=100%) = 0W. A similar approach can be used for setting the S2 value. Assuming the original lower limit of discharge power S2 is set to -1200W, once the SOC is less than the lower limit of the state of charge SOC1 (e.g., 30%), S2 linearly increases from -1200W, i.e., S2(SOC=20%) = -800W; S2(SOC=10%) = -400W; S2(SOC=0%) = 0W. Therefore, the electrical parameter S is the power (charging power) P input to the secondary battery 104. in In this case, the predetermined upper limit of charging power S1 and the predetermined lower limit of discharging power S2 can be maintained at fixed values ​​or adjusted according to the SOC. As for the SOC of the secondary battery 104, it can be determined from the output voltage of the secondary battery 104 in the power transmission path 114, or estimated by the output voltage of the secondary battery 104 in the power transmission path 114 and the amount of electricity entering and leaving the secondary battery 104 from the power transmission path 114, for example, by the estimation method disclosed in Taiwan Patent Publication No. TW 1337413.

[0053] In another embodiment, the electrical parameter S is the state of charge (SOC) of the secondary battery 104, and the predetermined upper limit value S1 is the upper limit value of the SOC, and the predetermined lower limit value S2 is the lower limit value of the SOC. Therefore, both S1 and S2 are greater than 0. As for the state of charge of the secondary battery 104, it is as described above and will not be repeated here.

[0054] In yet another embodiment, reference is made to... Figure 1D The electrical parameter S can be the input current I of the secondary battery 104. inThe predetermined upper limit value S1 is the upper limit value of the input current, and the predetermined lower limit value S2 is the lower limit value of the input current, where S1>0 and S2<0. When the secondary battery 104 receives current from the power transmission path 114, the S value is greater than zero; when the secondary battery outputs current through the power transmission path 114, the S value is less than zero. Furthermore, the state of charge (SOC) of the secondary battery 104 can be estimated by the monitoring device 106, as... Figure 1C The curve change shown is, Figure 1C The charging power and discharging power are changed to charging current and discharging current. Therefore, when the state of charge (SOC) is greater than an upper limit value of SOC2, the aforementioned upper limit value of input current (S1) is reduced, and when the state of charge (SOC) is less than an upper limit value of SOC1, the aforementioned lower limit value of input current (S2) is increased.

[0055] In yet another embodiment, referring to Figure 1E The electrical parameter S is the output voltage V from the secondary battery 104 to the (variable) load. Batt And the predetermined upper limit value S1 is the terminal voltage upper limit value V. H The predetermined lower limit value S2 is the terminal voltage lower limit value V. L .

[0056] Figure 2 This is a step diagram of the control method for the fuel cell stack of the first embodiment. Therefore, the contents of the control system can be referred to the above description of the first embodiment, and will not be repeated here.

[0057] Please refer to Figure 2 In step 200, a monitoring device is used ( Figure 1A Step 106) Monitoring the power transmission path ( Figure 1A The electrical parameter S of (114), where S can be the power P input to the secondary battery. in The state of charge (SOC) of the secondary battery and the output voltage V of the secondary battery. Batt Input current I of secondary battery 104 in Or the output voltage V of fuel cell stack 102 FC .

[0058] When S is the power P input to the secondary battery in The predetermined upper limit value S1 is the upper limit value of (charging) power, and the predetermined lower limit value S2 is the lower limit value of (discharging) power.

[0059] When S is the state of charge (SOC) of the secondary battery, the predetermined upper limit value S1 is the upper limit value of the state of charge, and the predetermined lower limit value S2 is the lower limit value of the state of charge.

[0060] When S is the input current I of the secondary battery 104 inThe predetermined upper limit value S1 is the upper limit value of the input current, and the predetermined lower limit value S2 is the lower limit value of the input current.

[0061] When S is the output voltage V of the secondary battery Batt The predetermined upper limit value S1 is the upper limit value of the terminal voltage, and the predetermined lower limit value S2 is the lower limit value of the terminal voltage.

[0062] When S is the output voltage V of fuel cell stack 102 FC The predetermined upper limit value S1 is the upper limit value of the output voltage of the fuel cell stack, and the predetermined lower limit value S2 is the lower limit value of the output voltage of the fuel cell stack.

[0063] Then, using the control device ( Figure 1A (108) Receive the electrical parameter S, and first determine whether the electrical parameter S exceeds a predetermined upper limit value S1 (step 202). If S is greater than or equal to S1, then execute step 204; if S is less than S1, then execute step 206.

[0064] In step 204, it is confirmed whether the number N of currently activated fuel cell stacks is the minimum number N. min If N = N min Then return to step 200. If N is not N min Then the control device ( Figure 1A Step 108) will output a first control signal to shut down the power output of one of the fuel cell stacks (step 208).

[0065] In step 206, it is determined whether the electrical parameter S is lower than or equal to a predetermined lower limit value S2. If S is less than or equal to S2, step 210 is executed; if S is greater than S2, the process returns to step 200.

[0066] In step 210, it is confirmed whether the number N of currently activated fuel cell stacks is the maximum number N. max If N = N max Then return to step 200. If N is not N max Then the control device ( Figure 1A (108) will output a second control signal to start the power output of one of the fuel cell stacks (step 212).

[0067] Furthermore, regardless of whether step 212 or step 208 is executed, the process will return to step 200 to continuously monitor the electrical parameter S. Therefore, it is possible to respond in real time to load changes and start or stop the power generation operation of some parallel fuel cell stacks, enabling multiple fuel cell stacks to operate in parallel. Figure 1A The output voltage of (102) is controlled within a specific expected range. In particular, the monitored electrical parameter S is related to the secondary battery ( Figure 1AThe value is directly related to 104), so this embodiment does not need to monitor the state of the load or the fuel cell stack itself. It only needs to monitor the power output state of the secondary battery to control the output power of the fuel cell stack and keep the discharge or charging power of the secondary battery within an appropriate range.

[0068] Figure 3 This is a block diagram of a specific example of the control system for the fuel cell stack of the first embodiment, wherein the control system is used in conjunction with... Figure 1A The same markings are used to represent the same or similar components, and the contents of the same or similar components can also be referenced. Figure 1A The relevant explanations will not be repeated here.

[0069] Please refer to Figure 3 The multiple fuel cell stacks 102 may include multiple fuel cell stacks 300, and each fuel cell stack 300 is equipped with a balance of plant (BOP) device 302. The BOP 302 controls the opening and closing of the intake valve 304. Since the intake valve 304 is connected to the fuel tank 306, closing one intake valve 304 means shutting down the power output of one fuel cell stack 300; opening one intake valve 304 means starting the power output of one fuel cell stack 300. Figure 3 Although four fuel cell stacks 300 are shown, it should be understood that the number of fuel cell stacks 300 in the multiple fuel cell stacks 102 of the present invention can be increased or decreased as needed. In addition, a pressure regulating device 310 can be provided in the gas fuel supply pipe 308 between the inlet valve 304 and the fuel tank 306 to control the gas pressure entering the fuel cell stack 300, wherein the pressure regulating device 310 is, for example, a pressure reducing valve.

[0070] exist Figure 3 In this configuration, the power output path of the multiple fuel cell stacks 102 is from each fuel cell stack 300 to the BOP 302, and then to each power output terminal 110. When the control device 108 receives the electrical parameter S measured by the monitoring device 106, it will perform the following... Figure 2 The steps are as follows, and control signals are output to each BOP 302 to start or shut down a fuel cell stack 300 in parallel.

[0071] Figure 4 This is a block diagram of a control system for a fuel cell stack according to a second embodiment of the present invention, wherein the same or similar reference numerals as in the first embodiment are used to represent the same or similar components, and the contents of the same or similar components can also refer to the relevant description of the first embodiment above, and will not be repeated here.

[0072] Please refer to Figure 4The difference between the fuel cell stack control system in this embodiment and the first embodiment is that the electrical parameter S in the second embodiment is the power (charging power) P input to the secondary battery 104. in Therefore, the predetermined upper limit S1 is the upper limit of (charging) power, and the predetermined lower limit S2 is the lower limit of (discharging) power. Thus, the charging power is positive (S1>0), and the discharging power is negative (S2<0). The control system 100 of the fuel cell stack in this embodiment also includes a third DC voltage converter C3, which is disposed between the power output terminal 110 and the load terminal 112 of the fuel cell stack 102, so as to output power to the load terminal 112 via the third DC voltage converter C3. For example, if the variable load is the motor of an unmanned aerial vehicle (UAV), and the operating voltage of the UAV motor is between 42V and 55V, then the preset output voltage Vout of the third DC voltage converter C3 can be set within the above range to ensure that the terminal voltage of the output load terminal 112 meets the operating voltage of the UAV motor. The insufficient power output will be supplemented to the load terminal 112 by the secondary battery 104 through the power transmission path 114, or the secondary battery 104 will absorb the excessive power output through the power transmission path 114.

[0073] Figure 5 This is a block diagram of a control system for a fuel cell stack according to a third embodiment of the present invention, wherein the same or similar reference numerals as in the first embodiment are used to represent the same or similar components, and the contents of the same or similar components can also refer to the relevant description of the first embodiment above, and will not be repeated here.

[0074] Please refer to Figure 5 In this embodiment, the electrical parameter S of the fuel cell stack control system is the power (charging power) P input to the secondary battery 104. inTherefore, the predetermined upper limit S1 is the upper limit of (charging) power, and the predetermined lower limit S2 is the lower limit of (discharging) power. Thus, the charging power is positive (S1>0), and the discharging power is negative (S2<0). The difference between this embodiment and the first embodiment is that it may also include a first DC-DC voltage converter C1 and a unidirectional current control element D1, disposed between the secondary battery 104 and the power transmission path 114. The first DC-DC voltage converter C1 transmits electrical energy from the secondary battery 104, supplying the power demand of the variable load via the load terminal 112. For example, if the output voltage setting of the first DC-DC voltage converter C1 is 44V, when the output voltage of the fuel cell stack 102 is lower than 44V, the secondary battery 104 will provide auxiliary power via C1 to adjust the voltage value supplied by the fuel cell stack 102 to the variable load so that it is not lower than the aforementioned output voltage setting value of the first DC-DC voltage converter C1. The unidirectional current control element D1 transmits the remaining power from the fuel cell stack 102 to charge the secondary battery 104, wherein the unidirectional current control element D1 is, for example, a diode element. Therefore, when the load power demand decreases, causing the output voltage of the fuel cell stack 102 to be greater than the output voltage of the secondary battery 104, the output power of the fuel cell stack 102 will charge the secondary battery 104 via D1, resulting in a power (charging power) P in The value is greater than 0. Furthermore, when the load voltage at load terminal 112 is higher than a preset output voltage value of the first DC-DC voltage converter C1, the first DC-DC voltage converter C1 does not transmit electrical energy from the secondary battery 104. In this embodiment, the monitoring device is a device 502 that monitors the power input to the secondary battery, i.e., the electrical parameter S is the power P input to the secondary battery 104. in .

[0075] Figure 6 This is a block diagram of a control system for a fuel cell stack according to a fourth embodiment of the present invention, wherein the same or similar reference numerals as in the first embodiment are used to represent the same or similar components, and the contents of the same or similar components can also refer to the relevant description of the first embodiment above, and will not be repeated here.

[0076] Please refer to Figure 6 The difference between the fuel cell stack control system of this embodiment and the first embodiment is that it may further include a first DC-DC voltage converter C1 and a second DC-DC voltage converter C2, disposed between the secondary battery 104 and the power transmission path 114. The first DC-DC voltage converter C1 transmits electrical energy from the secondary battery 104, supplying power to the fluctuating load via the load terminal 112. The second DC-DC voltage converter C2 receives electrical energy from the fuel cell stack 102 and converts it to the voltage level of the secondary battery 104, charging the secondary battery 104. The monitoring device in this embodiment monitors the output voltage V of the fuel cell stack 102. FCThe monitoring device 602, i.e., the electrical parameter S, is the terminal voltage V output from the fuel cell stack 102 to the (variable) load. FC And the predetermined upper limit value S1 is the upper limit value V of the output voltage of the fuel cell stack 102. H The predetermined lower limit value S2 is the lower limit value V of the output voltage of the fuel cell stack 102. L For example, the range of load power provided by the fuel cell stack 102 is 45V to 49.8V, therefore the predetermined upper limit value S1 is the upper limit value V of the output voltage of the fuel cell stack 102. H = 49.8V, the predetermined lower limit value S2 is the lower limit value V of the output voltage of the fuel cell stack 102. L =45V. When the output voltage V of fuel cell stack 102 is... FC Greater than V H At least one group of fuel cells in the multi-module fuel cell stack 102 will be shut down until all fuel cells are shut down; conversely, when the output voltage V of the fuel cell stack 102 is turned off... FC Less than V L At least one set of fuel cells in the multi-module fuel cell stack 102 will be started until all fuel cells are started.

[0077] In addition, the monitoring device 602 in this embodiment can simultaneously monitor the output voltage from the first DC voltage converter C1 and the input voltage transmitted to the second DC voltage converter C2 in the power transmission path 114. Assuming the normal operating voltage of the secondary battery 104 is 42V to 50.4V, and the set value V of the entire system's output voltage (i.e., the voltage at the load terminal 112) is... S1 The voltage is 44V, once the fuel cell stack 102 outputs voltage V. FC Below 44V, the secondary battery 104 will provide auxiliary power via the first DC-DC voltage converter C1 to regulate the voltage supplied by the fuel cell stack 102 to the variable load so that it is not lower than the aforementioned output voltage setting value V. S1 When the load power demand decreases, the output voltage V of the fuel cell stack 102 decreases. FC The input voltage V is greater than the preset input voltage value of the second DC-DC voltage converter C2. S2 When the voltage is at a set voltage range (e.g., 45.6V), a portion of the current output from the fuel cell stack 102 will charge the secondary battery 104 via the second DC-DC voltage converter C2. In other words, the secondary battery 104 charges the secondary battery 104 within a set voltage range (output voltage V). FC It neither charges nor discharges within a range of 44V to 45.6V. On the other hand, the load voltage at load terminal 112 is higher than the aforementioned set value V. S1 At this time, the first DC-DC voltage converter C1 does not transmit electrical energy from the secondary battery 104. Additionally, the preset output voltage value V of the second DC-DC voltage converter C2... S3The output current supply to the secondary battery 104 is stopped when the output voltage of the second DC voltage converter C2 is higher than the maximum charging voltage, and the voltage is less than or equal to the maximum charging voltage of the secondary battery 104. (Set value V) S1 This is used as the voltage condition for regulating the discharge of the secondary battery 104 by the first DC voltage converter C1; the preset input voltage value V S2 / Preset output voltage value V S3 It is the voltage condition used by the second DC voltage converter C2 to charge the secondary battery 104.

[0078] Figure 7 This is a block diagram of a control system for a fuel cell stack according to a fifth embodiment of the present invention, wherein the second embodiment is used ( Figure 4 The same or similar symbols are used to represent the same or similar components, and the content of the same or similar components can also refer to the relevant description of the first embodiment above, which will not be repeated here.

[0079] Please refer to Figure 7 The difference between the control system of the fuel cell stack in this embodiment and that in the second embodiment is that the monitoring device monitors the output voltage V of the secondary battery 104. Batt The device 700, i.e., the electrical parameter S, is the terminal voltage V output from the secondary battery 104 to the (variable) load. Batt And the predetermined upper limit value S1 is the terminal voltage upper limit value V. H The predetermined lower limit value S2 is the terminal voltage lower limit value V. L .

[0080] In this embodiment, the number of fuel cells used for power generation in the multiple fuel cell stacks 102 is based on the output voltage V of the secondary battery 104. Batt Control is performed, and therefore it is also affected by the state of charge (SOC) and charging / discharging current of the secondary battery 104. Please refer to... Figure 8 Assuming that the secondary battery 104 has a preset optimal charge and discharge voltage operating range, and the upper limit V H The voltage is 49.2V and the lower limit is V. L The voltage is 46.8V. When the SOC of the secondary battery 104 is 80% (open circuit voltage OCV is approximately 48V), if the recharge current I of the secondary battery 104 is equal to 24A (I = +24A), the output voltage V1 of the secondary battery 104 will be equal to the upper limit of the terminal voltage V. H (49.2V), therefore, once the recharge current I is greater than 24A (I>+24A), the output voltage V1 will be greater than the upper limit of the terminal voltage V. HThis triggers the action of "shutting down the power output of at least one group in the fuel cell stack"; similarly, if the discharge current I at this time exceeds / is less than -24A (I<-24A), the output terminal voltage V2 of the secondary battery 104 will drop below the lower limit of the terminal voltage V. L (46.8V), thus triggering the action of "starting the power output of at least one of the fuel cell stacks".

[0081] The higher the SOC of the secondary battery 104, the higher its open circuit voltage OCV (OCV). For example, when the SOC of the secondary battery 104 is 90%, without charging or discharging (I = 0A), the output terminal voltage V3 of the secondary battery 104 can be equal to the upper limit value of the terminal voltage V. H Therefore, this will trigger the action of "shutting down the power output of at least one of the fuel cell stacks"; on the other hand, the absolute value of the discharge current must be much greater than 24A (because the discharge current I < 0, so I << -24A) for the output voltage V4 of the secondary battery 104 to be lower than V. L (46.8V) triggers the action of “starting the power output of at least one group in the fuel cell stack”.

[0082] Conversely, the lower the SOC of the secondary battery 104, the lower its open-circuit voltage OCV. For example, when the SOC of the secondary battery 104 is 70%, it means that when it is not charging or discharging (I=0A), the output terminal voltage V5 of the secondary battery 104 is equal to the lower limit of the terminal voltage V. L Therefore, the action of "starting the power output of at least one group in the fuel cell stack" needs to be triggered immediately; on the other hand, if the action of "shutting down the power output of at least one group in the fuel cell stack" is to be triggered, a charging current much greater than 24A (I>>+24A) is required to make the output terminal voltage V6 of the secondary battery 104 greater than the upper limit value of the terminal voltage V. H .

[0083] In summary, this invention controls the system to respond in real-time to load changes, starting or stopping the power generation operation of some parallel fuel cell stacks, thus keeping the output voltage of multiple parallel fuel cell stacks within a predetermined range. Furthermore, the monitored parameter S is the electrical parameter S of the power transmission path connecting the secondary battery to the fuel cell stack; therefore, this invention achieves the above effects without needing to monitor the load or the status of each fuel cell (stack). Particularly useful in hybrid power supply systems where secondary batteries provide auxiliary power, controlling the output power of the fuel cell stacks ensures that the discharge or charging power of the secondary batteries is also controlled within an appropriate range.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A control system for a fuel cell stack, characterized in that, include: Multiple fuel cell stacks, each with independent start-up or shutdown power output, and the power output terminals of the multiple fuel cell stacks are connected in parallel to a load terminal to provide power; The secondary battery is connected to the power output terminal of the fuel cell stack via a power transmission path; A monitoring device is used to monitor the electrical parameters of the power transmission path, wherein the electrical parameters are the power input to the secondary battery, the state of charge of the secondary battery, the terminal voltage output from the secondary battery to the load, the output voltage of the fuel cell stack, the output terminal voltage of the secondary battery, or the current input to the secondary battery. as well as The control device receives signals of the electrical parameters from the monitoring device, and when the electrical parameters exceed a predetermined upper limit value, outputs a first control signal to shut down the power output of at least one group in the fuel cell stack, and when the electrical parameters are lower than a predetermined lower limit value, outputs a second control signal to start the power output of at least one group in the fuel cell stack, wherein when the electrical parameters are the power input to the secondary battery, the predetermined upper limit value is the upper limit value of the charging power, and the predetermined lower limit value is the lower limit value of the discharging power.

2. The control system for the fuel cell stack according to claim 1, characterized in that, The monitoring device also includes a means for estimating the state of charge of the secondary battery, which is used to estimate the state of charge of the secondary battery. When the state of charge is greater than an upper limit value of the state of charge, the upper limit value of the charging power is reduced, and when the state of charge is less than an upper limit value of the state of charge, the lower limit value of the discharge power is increased.

3. The control system for the fuel cell stack according to claim 1, characterized in that, The electrical parameter is the state of charge of the secondary battery, and the predetermined upper limit is the upper limit of the state of charge, and the predetermined lower limit is the lower limit of the state of charge.

4. The control system for the fuel cell stack according to claim 3, characterized in that, The state of charge of the secondary battery is estimated from the output voltage of the secondary battery in the power transmission path and the amount of electricity entering and leaving the secondary battery through the power transmission path.

5. The control system for the fuel cell stack according to claim 3, characterized in that, The state of charge of the secondary battery is determined based on the output voltage of the secondary battery.

6. The control system for the fuel cell stack according to claim 1, characterized in that, It also includes a first DC-DC voltage converter, disposed between the secondary battery and the power transmission path, for transmitting power from the secondary battery to supply the power demand of the load via the load end.

7. The control system for a fuel cell stack according to claim 6, characterized in that, When the load voltage at the load end is higher than a preset voltage value of the first DC voltage converter, the first DC voltage converter does not transmit electrical energy to the secondary battery.

8. The control system for the fuel cell stack according to claim 6, characterized in that, It also includes a unidirectional current control element disposed between the secondary battery and the power transmission path, for transmitting the remaining power from the fuel cell stack to charge the secondary battery.

9. The control system for a fuel cell stack according to claim 8, characterized in that, The unidirectional current control element is a diode element.

10. The control system for a fuel cell stack according to claim 6, characterized in that, The electrical parameter is the terminal voltage output from the secondary battery to the load via the first DC voltage converter, and the predetermined upper limit is the upper limit value of the terminal voltage, and the predetermined lower limit is the lower limit value of the terminal voltage.

11. The control system for a fuel cell stack according to claim 6, characterized in that, It also includes a second DC-DC voltage converter disposed between the secondary battery and the power transmission path, for receiving power from the fuel cell stack and converting it into a voltage level for the secondary battery to charge the secondary battery, wherein the electrical parameter is the output voltage of the fuel cell stack, and the predetermined upper limit value is the upper limit value of the output voltage of the fuel cell stack, and the predetermined lower limit value is the lower limit value of the output voltage of the fuel cell stack.

12. The control system for a fuel cell stack according to claim 11, characterized in that, The second DC voltage converter has a preset input voltage value. When the output voltage of the fuel cell stack is greater than the preset input voltage value, a portion of the current from the fuel cell stack will charge the secondary battery via the second DC voltage converter.

13. The control system for a fuel cell stack according to claim 12, characterized in that, The second DC voltage converter has a preset output voltage value, which is less than or equal to the maximum charging voltage of the secondary battery. When the output voltage of the second DC voltage converter is higher than the maximum charging voltage, the output current supplied to the secondary battery is stopped.

14. The control system for the fuel cell stack according to claim 1, characterized in that, It also includes a third DC-DC voltage converter, disposed between the power output terminal and the load terminal of the fuel cell stack, to output power to the load terminal via the third DC-DC voltage converter.

15. The control system for a fuel cell stack according to claim 1, characterized in that, The electrical parameter is the output terminal voltage of the secondary battery, and the predetermined upper limit is the upper limit value of the terminal voltage, and the predetermined lower limit is the lower limit value of the terminal voltage.

16. The control system for a fuel cell stack according to claim 1, characterized in that, The electrical parameter is the current input to the secondary battery, and the predetermined upper limit is the upper limit of the input current, and the predetermined lower limit is the lower limit of the input current.

17. A control method for a fuel cell stack, used to control multiple fuel cell stacks, wherein each fuel cell stack has an independent start-up or shutdown electrical output, and the electrical output terminal of the fuel cell stack is connected in parallel to a load terminal to provide power, characterized in that, The control method includes: A secondary battery is provided, which is connected to the power output terminal of the fuel cell stack via a power transmission path; The electrical parameters of the power transmission path are monitored using a monitoring device, wherein the electrical parameters are the power input to the secondary battery, the state of charge of the secondary battery, the terminal voltage output from the secondary battery to the load, the output voltage of the fuel cell stack, the output terminal voltage of the secondary battery, or the current input to the secondary battery; and The control device receives the electrical parameters and performs one of the following steps based on the electrical parameters: When the electrical parameters exceed a predetermined upper limit value, a first control signal is output to shut down the power output of at least one group in the fuel cell stack; When the electrical parameters fall below a predetermined lower limit, a second control signal is output to activate the power output of at least one group in the fuel cell stack. Wherein, when the electrical parameter is the power input to the secondary battery, the predetermined upper limit value is the upper limit value of the charging power, and the predetermined lower limit value is the lower limit value of the discharging power.

18. The control method for a fuel cell stack according to claim 17, characterized in that, It also includes monitoring the state of charge of the secondary battery, reducing the upper limit of the charging power when the state of charge is greater than an upper limit of the state of charge, and increasing the lower limit of the discharging power when the state of charge is less than an upper limit of the state of charge.

19. The control method for a fuel cell stack according to claim 17, characterized in that, The electrical parameter is the state of charge of the secondary battery, and the predetermined upper limit is the upper limit of the state of charge, and the predetermined lower limit is the lower limit of the state of charge.

20. The control method for a fuel cell stack according to claim 19, characterized in that, The state of charge of the secondary battery is estimated from the output voltage of the secondary battery in the power transmission path and the amount of electricity entering and leaving the secondary battery through the power transmission path.

21. The control method for a fuel cell stack according to claim 19, characterized in that, The state of charge of the secondary battery is determined based on the output voltage of the secondary battery.

22. The control method for a fuel cell stack according to claim 17, characterized in that, It also includes providing a first DC-DC voltage converter between the secondary battery and the power transmission path to transmit power from the secondary battery and supply the power demand of the load via the load end.

23. The control method for a fuel cell stack according to claim 22, characterized in that, When the load voltage connected to the load terminal is higher than a preset voltage value of the first DC voltage converter, the first DC voltage converter does not transmit electrical energy to the secondary battery.

24. The control method for a fuel cell stack according to claim 22, characterized in that, It also includes providing a unidirectional current control element between the secondary battery and the power transmission path to transmit the remaining power from the fuel cell stack to charge the secondary battery.

25. The control method for a fuel cell stack according to claim 24, characterized in that, The unidirectional current control element is a diode element.

26. The control method for a fuel cell stack according to claim 22, characterized in that, The electrical parameter is the terminal voltage output from the secondary battery to the load via the first DC voltage converter, and the predetermined upper limit is the upper limit value of the terminal voltage, and the predetermined lower limit is the lower limit value of the terminal voltage.

27. The control method for a fuel cell stack according to claim 22, characterized in that, It also includes providing a second DC-DC voltage converter between the secondary battery and the power transmission path, receiving power from the fuel cell stack and converting it to the voltage level of the secondary battery to charge the secondary battery, wherein the electrical parameter is the output voltage of the fuel cell stack, the predetermined upper limit value is the upper limit value of the output voltage of the fuel cell stack, and the predetermined lower limit value is the lower limit value of the output voltage of the fuel cell stack.

28. The control method for a fuel cell stack according to claim 27, characterized in that, The second DC voltage converter has a preset input voltage value. When the output voltage of the fuel cell stack is greater than the preset input voltage value, a portion of the current from the fuel cell stack will charge the secondary battery via the second DC voltage converter.

29. The control method for a fuel cell stack according to claim 28, characterized in that, The second DC voltage converter has a preset output voltage value, which is less than or equal to the maximum charging voltage of the secondary battery. When the output voltage of the second DC voltage converter is higher than the maximum charging voltage, the output current supplied to the secondary battery is stopped.

30. The control method for a fuel cell stack according to claim 17, characterized in that, The electrical parameter is the current input to the secondary battery, and the predetermined upper limit is the upper limit of the input current, and the predetermined lower limit is the lower limit of the input current.

31. The control method for a fuel cell stack according to claim 17, characterized in that, It also includes providing a third DC-DC voltage converter between the power output terminal and the load terminal to output power to the load terminal via the third DC-DC voltage converter.

32. The control method for a fuel cell stack according to claim 17, characterized in that, The electrical parameter is the output terminal voltage of the secondary battery, and the predetermined upper limit is the upper limit value of the terminal voltage, and the predetermined lower limit is the lower limit value of the terminal voltage.

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