Fuel cell power generation system and control method

Abstract

The invention discloses a fuel cell power generation system and a control method. The power generation system comprises a control unit, and an electric pile module, a DCAC module, a DCDC module and a fuel cell auxiliary system which are respectively connected with the control unit, the galvanic pile module, the DCAC module and the grid-connected circuit are sequentially connected to form a first line, the grid-connected circuit, the DCAC module, the DCDC module and the fuel cell auxiliary system are sequentially connected to form a second line, and the galvanic pile module, the DCAC module, the DCDC module and the fuel cell auxiliary system are sequentially connected to form a third line; the control unit is used for controlling the electric energy output of the electric pile unit and also used for controlling the DCAC module to be switched between a rectification mode and an inversion mode so as to switch the second circuit and the third circuit to uninterruptedly supply power to the fuel cell auxiliary system, and the DCDC module is located on a branch bus of a bus where the DCAC module is located. The system efficiency can be improved, the power level is reduced, the system architecture is simplified, the dynamic response capability is improved, and the system has high-voltage power supply and low-voltage power supply capabilities.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a fuel cell power generation system and control method. Background Technology

[0002] In existing technologies, fuel cell systems typically connect a DC-DC converter and a DC-AC converter in series on the voltage bus. The DC-DC converter provides the necessary DC power to both the Balance of Plant (BOP) fuel cell auxiliary system and the DC-AC converter, each with independent control. The DC-AC module is responsible for converting the DC power output from the fuel cell stack into AC power for the load. This independent control approach can meet the system's power requirements to some extent, but it has the following shortcomings in terms of architectural design:

[0003] This architecture outputs power via a "fuel cell stack-DC-DCAC" configuration. Due to losses in both the DC-DC and DC-AC stages, energy output from the fuel cell stack is wasted. To accommodate both fuel cell stack output and power supply to the BOP (Battery on the Power Plant), the DC-DC converter must provide both power and bus voltage platform functionality, typically employing a bidirectional DC-DC converter with lower cost and efficiency. Furthermore, the architecture fails to consider the coupling effects of BOP power fluctuations, DCAC efficiency variations, and fuel cell stack dynamic delays, resulting in insufficient disturbance compensation. BOP power prediction and efficiency compensation rely on fixed parameter tables, making them unsuitable for adapting to changing operating conditions and heavily dependent on static databases. Summary of the Invention

[0004] This invention provides a fuel cell power generation system and control method that can improve system efficiency, simplify system architecture, increase dynamic response capability, and has both high-voltage and low-voltage power supply capabilities. It is suitable for AC output scenarios such as distributed power generation systems that require high dynamic response power control.

[0005] According to one aspect of the present invention, a fuel cell power generation system is provided, comprising: a grid-connected circuit and a control unit, and a fuel cell stack module, a DCAC module, a DC-DC module, and a fuel cell auxiliary system respectively connected to the control unit;

[0006] The fuel cell stack module, the DCAC module, and the grid-connected circuit are connected in sequence to form a first circuit; the grid-connected circuit, the DCAC module, the DC-DC module, and the fuel cell auxiliary system are connected in sequence to form a second circuit; and the fuel cell stack module, the DCAC module, the DC-DC module, and the fuel cell auxiliary system are connected in sequence to form a third circuit.

[0007] The control unit is used to control the output of electrical energy of the fuel cell stack module, and also to control the DCAC module to switch between rectification mode and inverter mode, so as to switch the second line and the third line to supply power to the fuel cell auxiliary system. The DC-DC module is located on a branch bus of the bus where the DCAC module is located.

[0008] Optionally, the fuel cell stack module includes a fuel cell stack unit, a first pre-charge circuit, and a discharge circuit. The output terminal of the fuel cell stack unit is connected to one end of the first pre-charge circuit, and the other end of the first pre-charge circuit is connected to the DCAC module and the DCDC module. The discharge circuit is located at the output terminal of the fuel cell stack unit.

[0009] The first pre-charge circuit includes a first resistor, a first switch, and a first circuit breaker. The first circuit breaker is located between the output terminal of the fuel cell unit and the DCAC module. The first resistor and the first switch form a first series branch. The two ends of the first series branch are connected in parallel to the two ends of the first circuit breaker. The control unit is connected to the first pre-charge circuit and the discharge circuit.

[0010] Optionally, the DCAC module includes: a bidirectional DCAC unit, a filter unit, and a second pre-charging circuit. One end of the bidirectional DCAC unit is connected to the fuel cell stack module and the DC-DC module. The other end of the bidirectional DCAC unit is connected to one end of the filter unit. The other end of the filter unit is connected to one end of the second pre-charging circuit. The other end of the second pre-charging circuit is connected to the grid-connected circuit.

[0011] The second pre-charging circuit includes a second resistor, a second switch, and a second circuit breaker. The second circuit breaker is located between the filter unit and the grid-connected circuit. The second resistor and the second switch form a second series branch. The two ends of the second series branch are connected in parallel to the two ends of the second circuit breaker. The bidirectional DCAC unit and the second pre-charging circuit are both connected to the control unit.

[0012] Optionally, the fuel cell power generation system further includes a low-voltage power supply module, which includes a DCL step-down unit and a UPS power supply unit. The grid-connected circuit, the DCAC module, the DC-DC module, and the DCL step-down unit form a fourth circuit, and the fuel cell stack module, the DC-DC module, and the DCL step-down unit form a fifth circuit.

[0013] The DCL step-down unit is used to draw power from the DCDC module and step down the voltage, and the UPS power supply unit is used to draw power from AC 220V.

[0014] Optionally, the fuel cell power generation system further includes a transformer isolation unit located between the DCAC module and the grid-connected circuit.

[0015] Optionally, the fuel cell auxiliary system includes a third switch and a fuel cell auxiliary unit, the third switch being located at the connection between the fuel cell auxiliary unit and the DC-DC module, and the control unit being connected to the third switch.

[0016] According to another aspect of the present invention, a control method for a fuel cell power generation system is provided, implemented based on the fuel cell power generation system described in any embodiment of the present invention, the control method comprising:

[0017] Before the control stack module outputs electrical energy, the control DCAC module is in high-voltage rectification mode and supplies power to the fuel cell auxiliary system through the second line;

[0018] After controlling the stack module to output electrical energy, the DCAC module is controlled to enter inverter mode, supplying electrical energy to the grid-connected circuit through the first line, and simultaneously supplying power to the fuel cell auxiliary system through the third line.

[0019] After controlling the stack module to stop outputting electrical energy, the DCAC module is controlled to enter uncontrolled rectification mode, and power is supplied to the fuel cell auxiliary system through the second line.

[0020] Optionally, the DCAC module includes a bidirectional DCAC unit, a filtering unit, and a second pre-charge circuit; the fuel cell stack module includes a fuel cell stack unit, a first pre-charge circuit, and a discharge circuit.

[0021] Before controlling the stack module to output electrical energy, controlling the DCAC module to be in high-voltage rectification mode and supplying power to the fuel cell auxiliary system through the second line includes:

[0022] Disconnect the first pre-charge circuit;

[0023] The second switch in the second pre-charging circuit is closed and the second circuit breaker is opened. At the same time, the bidirectional DCAC unit is controlled to be in rectification mode and the voltage of the bidirectional DCAC unit is monitored. When the voltage of the bidirectional DCAC unit is at a first preset value, the second switch is controlled to open and the second circuit breaker is closed, so that the grid-connected circuit supplies power to the fuel cell auxiliary system through the second pre-charging circuit, the filter unit, the bidirectional DCAC unit, and the DC-DC module.

[0024] Optionally, after controlling the stack module to output electrical energy, controlling the DCAC module to be in inverter mode, supplying electrical energy to the grid-connected circuit through the first line, and simultaneously supplying power to the fuel cell auxiliary system through the third line includes:

[0025] The system controls the output of electrical energy from the fuel cell unit and monitors the overall voltage of the fuel cell unit. When the overall voltage of the fuel cell unit is greater than a second preset value, the system controls the first switch in the first pre-charging circuit to close and the first circuit breaker to open.

[0026] When the voltage difference across the first circuit breaker is within a preset threshold range, the first switch is opened and the first circuit breaker is closed, and the fuel cell stack unit supplies power to the fuel cell auxiliary system through the first pre-charging circuit and the DC-DC module.

[0027] The bidirectional DCAC unit is controlled to be in inverter mode, and the fuel cell unit supplies power to the grid-connected circuit through the first pre-charging circuit, the bidirectional DCAC unit, the filter unit, and the second pre-charging circuit.

[0028] Optionally, after controlling the fuel cell stack module to stop outputting electrical energy, controlling the DCAC module to be in uncontrolled rectification mode and supplying power to the fuel cell auxiliary system through the second line includes:

[0029] The fuel cell unit is controlled to stop outputting electrical energy, and the fuel cell unit is purged and shut down.

[0030] After the fuel cell stack unit is purged and shut down, the discharge circuit is controlled to discharge the voltage of the fuel cell stack unit in stages. Specifically, when the DC bus voltage is lower than a third preset value, the first pre-charge circuit is disconnected; the bidirectional DCAC unit is controlled to be in uncontrolled rectification mode so that the grid-connected circuit supplies power to the fuel cell auxiliary system through the second pre-charge circuit, the filter unit, the bidirectional DCAC unit, and the DC-DC module, and continues to discharge through the discharge circuit.

[0031] When the discharge voltage reaches the fourth preset value, the second pre-charge circuit is disconnected.

[0032] According to embodiments of the present invention, a fuel cell power generation system and control method are provided. The power generation system includes: a grid-connected circuit and a control unit, and a fuel cell stack module, a DCAC module, a DC-CDC module, and a fuel cell auxiliary system respectively connected to the control unit. The fuel cell stack module, DCAC module, and grid-connected circuit are sequentially connected to form a first line; the grid-connected circuit, DCAC module, DC-CDC module, and fuel cell auxiliary system are sequentially connected to form a second line; and the fuel cell stack module, DCAC module, DC-CDC module, and fuel cell auxiliary system are sequentially connected to form a third line. The control unit is used to control the output of electrical energy from the fuel cell stack module and to control the DCAC module to switch between rectification mode and inverter mode, thereby switching the second line and the third line to supply power to the fuel cell auxiliary system. The DC-CDC module is located on a branch bus of the bus where the DCAC module is located. This system can improve system efficiency, simplify system architecture, increase dynamic response capability, and has both high-voltage and low-voltage power supply capabilities.

[0033] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a circuit topology diagram of a fuel power generation system in the prior art;

[0036] Figure 2 This is a circuit topology diagram of a fuel cell power generation system provided in an embodiment of the present invention;

[0037] Figure 3 This is a circuit diagram of a fuel cell power generation system provided in an embodiment of the present invention;

[0038] Figure 4 This is a circuit diagram of a fuel cell power generation system provided in one embodiment of the present invention;

[0039] Figure 5 This is a flowchart of the control method for a fuel cell power generation system provided in an embodiment of the present invention;

[0040] Figure 6 This is a flowchart of a control method for a fuel cell power generation system provided in a specific embodiment of the present invention. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0042] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0043] Figure 1 This is a circuit topology diagram of a fuel-powered power generation system in the prior art. For example... Figure 1As shown, the fuel cell power generation system includes: fuel cell BOP01, fuel cell stack 02, energy storage battery 03, bidirectional DC-DC converter 04, first filter 05, bidirectional DCAC converter 06, transformer 07, second filter 08, and load / grid connection 09. After the fuel cell stack 02 outputs electrical energy, it sequentially supplies power to the fuel cell BOP through the bidirectional DC-DC converter 04, and also supplies power to the load / grid connection 09 through the bidirectional DC-DC converter 04, first filter 05, bidirectional DCAC converter 06, transformer 07, and second filter 08. The bidirectional DC-DC converter 04 also requires power from the energy storage battery 03. Before the fuel cell stack 02 outputs electrical energy, the grid connection supplies power to the fuel cell BOP01 through the second filter 08, transformer 07, bidirectional DCAC converter 06, first filter 05, and bidirectional DC-DC converter 04. It can be seen that during the startup phase, the fuel cell BOP01 has a power supply problem; that is, in the single DCAC inverter mode, the fuel cell BOP01 cannot supply power, the fuel cell stack cannot establish voltage, and the system cannot start up at high voltage. Furthermore, during startup, the current reverses (i.e., in rectification mode), and due to the voltage difference, power is supplied to fuel cell stack 02 in reverse, causing electrolysis and damage to stack 02, leading to safety issues. Additionally, during shutdown, there is a power supply problem with fuel cell BOP01. When the fuel cell stack stops operating, fuel cell BOP01 cannot provide sufficient power, resulting in low bus voltage and an emergency shutdown of fuel cell BOP01. Moreover, because the DC-DC converter is connected in series with the DC-AC converter, bipolar losses are severe, leading to wasted energy output from stack 02. Bidirectional DC-DC converters are also costly, inefficient, and have a slow overall response.

[0044] This invention proposes a fuel cell power generation system and control method, which can improve system efficiency, simplify system architecture, increase dynamic response capability, and has both high-voltage and low-voltage power supply capabilities. It is suitable for AC output scenarios such as distributed power generation systems that require high dynamic response power control.

[0045] The fuel cell power generation system of the present invention will now be described in detail with reference to the accompanying drawings. Figure 2 This is a circuit topology diagram of a fuel cell power generation system provided in an embodiment of the present invention. Figure 2 As shown, the fuel cell power generation system includes: a grid-connected circuit 106 and a control unit 101, as well as a fuel cell stack module 102, a DCAC module 103, a DC-DC module 104, and a fuel cell auxiliary system 105, which are respectively connected to the control unit 101.

[0046] The stack module 102, DCAC module 103 and grid-connected circuit 106 are connected in sequence to form a first line; the grid-connected circuit 106, DCAC module 103, DCCDC module 104 and fuel cell auxiliary system 105 are connected in sequence to form a second line; and the stack module 102, DCAC module 103, DCCDC module 104 and fuel cell auxiliary system 105 are connected in sequence to form a third line.

[0047] The control unit 101 is used to control the output of electrical energy of the stack module 102, and also to control the DCAC module 103 to switch between rectification mode and inverter mode, so as to switch the second line and the third line to supply power to the fuel cell auxiliary system 105. The DC-DC module 104 is located on a branch bus of the bus where the DCAC module 103 is located.

[0048] Understandably, before the control unit 101 controls the stack module 102 to output electrical energy, the control DCAC module 103 is in high-voltage rectification mode and supplies power to the fuel cell auxiliary system 105 through the second line; after the control unit 101 controls the stack module 102 to output electrical energy, the control DCAC module 103 is in inverter mode, supplying electrical energy to the grid-connected circuit 106 through the first line, and simultaneously supplying power to the fuel cell auxiliary system 105 through the third line; after the control stack module 102 stops outputting electrical energy, the control DCAC module 103 is in uncontrolled rectification mode and supplies power to the fuel cell auxiliary system 105 through the second line.

[0049] In other words, in this fuel cell power generation system, before the fuel cell stack module 102 starts working, the grid-connected circuit 106 outputs high-voltage electricity, which is then rectified by the DCAC module 103 and transmitted to the DC-DC module 104, which in turn supplies power to the fuel cell auxiliary system 105. After the fuel cell stack module 102 starts working, it outputs electrical energy, which is then inverted by the DCAC module 103 and transmitted to the grid-connected circuit 106. Simultaneously, it can also supply power to the fuel cell auxiliary system 105 via the DC-DC module 104. After the fuel cell stack module 102 stops working, the grid-connected circuit 106 can resume outputting high-voltage electricity, which is then rectified by the DCAC module 103 and transmitted to the DC-DC module 104, which in turn supplies power to the fuel cell auxiliary system 105.

[0050] In this context, the high-voltage rectification mode can be understood as the set voltage of the DCAC module 103 being lower than the open-circuit voltage of the stack module 102 but higher than the minimum voltage provided by the stack module 102 to the fuel cell auxiliary system 105. The uncontrolled rectification mode can be understood as the DCAC module 103 not needing to perform high-voltage rectification in the high-voltage rectification mode; the 630V / AC of the normal grid-connected circuit 106 can be rectified to 900V / DC through uncontrolled rectification.

[0051] In the above embodiment, the fuel cell auxiliary system 105 is the battery BOP, the balancing system of the fuel cell system, including equipment such as compressors, radiators, hydrogen circulation pumps, and PTC, to ensure the normal operation of the fuel cell system. A fuse FU is also installed between the fuel cell auxiliary system 105 and the DC-DC module, so that when the current in one path is large, the device in that path can be protected by blowing the fuse. The DC-DC module 104 is a DC-DC converter used to adjust the DC voltage and provide the required voltage to other devices in the system. The DC-AC module 103 is a DC-AC converter that converts the DC power generated by the fuel cell stack into AC power. The fuel cell stack module 102 is composed of multiple stacked fuel cell units and is used to generate DC power. The DC bus is a common voltage transmission line connecting the output of the fuel cell stack module 102 to the DC-AC and DC-DC modules.

[0052] In this way, by branching off a power supply line from the bus between the output of the fuel cell stack module 102 and the DC-AC (Direct-to-Acoustic Converter) to power the DC-DC converter, the BOP (Balanced Plant) operation of the fuel cell system is supported, thereby reducing redundant DC-DC stages, lowering the energy conversion levels, and improving system efficiency. This approach offers significant advantages in terms of architectural topology, reducing first-stage energy conversion losses and improving system efficiency by 8%-12%. The bus voltage is autonomously adjusted by the dynamic characteristics of the fuel cell stack, avoiding multi-stage control conflicts. Integrating the BOP through bus branch power supply eliminates redundant DC-DC stages, reduces the number and complexity of system equipment, lowers system costs, and simultaneously improves system reliability and maintainability. Dynamic load control of the DC-AC is achieved, reducing terminal control deviations and enhancing dynamic response capabilities. External low-power AC power supply provides dual power supply (DC + AC), and the BOP is powered under all operating conditions through rectification mode and fuel cell stack output.

[0053] Optionally, Figure 3 This is a circuit diagram of a fuel cell power generation system provided in an embodiment of the present invention. Figure 2 and Figure 3As shown, the fuel cell stack module 102 includes a fuel cell stack unit 1021, a first pre-charge circuit 1022, and a discharge circuit 1023. The output terminal of the fuel cell stack unit 102 is connected to one end of the first pre-charge circuit 1022, and the other end of the first pre-charge circuit 1022 is connected to the DCAC module 103 and the DC-DC module 104. The discharge circuit 1023 is located at the output terminal of the fuel cell stack unit 1021.

[0054] The first pre-charge circuit 1022 includes a first resistor R1, a first switch K1, and a first circuit breaker CB1. The first circuit breaker CB1 is located between the output terminal of the fuel cell unit 102 and the DCAC module 103. The first resistor R1 and the first switch K1 form a first series branch. The two ends of the first series branch are connected in parallel across the two ends of the first circuit breaker CB1. The control unit 101 is connected to the first pre-charge circuit 1022 and the discharge circuit 1023.

[0055] Understandably, before the fuel cell stack unit 1021 starts operating, the grid-connected circuit 106 or other auxiliary power supply inputs electrical energy (AC10kV / 380V) to establish the critical low-voltage power supply for the system. Simultaneously, an AC630V voltage is established via a transformer, and power is supplied to the fuel cell auxiliary system 105 sequentially through the second pre-charge circuit 1033, the filter unit 1032, the bidirectional DCAC unit 1031, and the unidirectional DC-DC unit 1041. At this time, the first pre-charge circuit 1022 needs to be disconnected to prevent the grid-connected circuit 106 from reverse-charging the fuel cell stack unit 1021, causing electrolysis and damage to the stack unit 1021, resulting in safety issues. That is, both the first switch K1 and the first circuit breaker CB1 in the first pre-charge circuit 1022 need to be disconnected.

[0056] After the fuel cell unit 1021 starts working and the overall voltage reaches a certain value (e.g., 1400V), it indicates that the fuel cell unit 1021 can output electrical energy. At this time, the first switch K1 can be closed first and the first circuit breaker CB1 can be opened. When the voltage across the first circuit breaker CB1 reaches a slight balance, the first circuit breaker CB1 can be closed again and the first switch K1 can be opened. This can prevent arcing when the first circuit breaker CB1 is closed.

[0057] Therefore, the first pre-charging circuit 1022 can prevent reverse charging of the fuel cell unit 1021 and ensure the safety of the circuit when the fuel cell unit 1021 outputs electrical energy.

[0058] The discharge circuit 1023 is mainly used to discharge the residual pressure of the fuel cell stack unit 1021 after it stops working, ensuring the normal operation capability of the fuel cell stack unit 1021 and the safety of the entire fuel cell system. It should be noted that after the fuel cell stack unit 1021 stops working, the first circuit breaker CB1 needs to be disconnected to prevent reverse power supply to the fuel cell stack unit 1021 due to a decrease in voltage.

[0059] Optionally, continue to refer to Figure 2 and Figure 3 As shown, the DCAC module 103 includes: a bidirectional DCAC unit 1031, a filter unit 1032, and a second pre-charging circuit 1033. One end of the bidirectional DCAC unit 1031 is connected to the fuel cell stack module 102 and the DC-DC module 104. The other end of the bidirectional DCAC unit 1031 is connected to one end of the filter unit 1032. The other end of the filter unit 1032 is connected to one end of the second pre-charging circuit 1033. The other end of the second pre-charging circuit 1033 is connected to the grid-connected circuit 106.

[0060] The second pre-charging circuit 1033 includes a second resistor R2, a second switch K2, and a second circuit breaker CB2. The second circuit breaker CB2 is located between the filter unit 1032 and the grid-connected circuit 106. The second resistor R2 and the second switch K2 form a second series branch. The two ends of the second series branch are connected in parallel to the two ends of the second circuit breaker CB2. The bidirectional DCAC unit 1031 and the second pre-charging circuit 1033 are both connected to the control unit 101.

[0061] Understandably, before the fuel cell stack unit 1021 outputs electrical energy, the grid-connected circuit 106 supplies power to the fuel cell auxiliary system 105 through the DCAC module 103 and the DC-DC module 104. Since the initial voltage difference between the bidirectional DCAC unit 1031 and the grid-connected circuit 106 is relatively large, the second switch K2 can be closed first. When the voltage difference across the second circuit breaker CB2 reaches a certain value, the second circuit breaker CB2 can then be closed. This avoids sudden changes in the input voltage of the bidirectional DCAC unit 1031, preventing damage to the bidirectional DCAC unit 1031. It also prevents arcing when the second circuit breaker CB2 is closed, further improving circuit safety. Furthermore, after the fuel cell auxiliary system 105 shuts down, the second circuit breaker CB2 can be disconnected to stop the grid-connected circuit 106 from supplying power to the fuel cell auxiliary system 105.

[0062] Therefore, the second pre-charging circuit 1033 has a protective function for the bidirectional DCAC unit 1031, and also has a protective function for the entire bus line.

[0063] The filter unit 1032 can be an LC filter (such as...) Figure 3The filter inductor L1 and filter capacitor C2 in the circuit can suppress harmonic currents, prevent harmonic pollution of the power grid, impede short-circuit current, slow down the current rise rate, buy more operating time for the circuit breaker, limit the amplitude of short-circuit current, reduce the dynamic and thermal stability requirements of the equipment, and further improve the safety of the line.

[0064] Optionally, continue to refer to Figure 2 and Figure 3 As shown, the fuel cell power generation system also includes a low-voltage power supply module 107, which includes a DCL step-down unit 1071, a UPS power supply voltage 1073 and a 24V power supply 1072. The grid-connected circuit 106, the DCAC module 103, the DC-DC module 104 and the DCL step-down unit 1071 form a fourth circuit, and the fuel cell stack module 102, the DC-DC module 104 and the DCL step-down unit 1071 form a fifth circuit.

[0065] The DCL step-down unit 1071 is used to draw power from the DC-DC module 104 and step down the voltage, while the UPS power supply unit 1073 is used to draw power from AC 220V.

[0066] Among them, the DC-DC module 104 is a unidirectional step-down DC, which reduces the bus voltage of the fuel cell auxiliary system 105 from 1000V to 650V. It is also equipped with a DCL step-down unit 1071 to reduce the voltage from 650V to 24V as a stable DC power supply.

[0067] The UPS power supply unit 1073 is connected to the power grid, providing 220V AC power to the system as a constant AC power source. The 220V power is converted to 24V through the power module. Then, through the DCL step-down unit and the 24V power supply 1072 conversion, a current sharing mode is achieved to realize a stable dual-path power supply (24V).

[0068] Therefore, before the fuel cell stack module 102 outputs electrical energy, the grid-connected circuit 106 supplies power to the low-voltage power supply module 107 via the DCAC module 103 and the DCDC module 104. After the fuel cell stack module 102 outputs electrical energy, it supplies power to the low-voltage power supply module 107 via the DCAC module 103 and the DCDC module 104. Thus, the fuel cell power generation system can continuously supply power to the low-voltage power supply module. The same logic can also continuously supply power to the fuel cell auxiliary system 105. Further, refer to... Figure 3 Anti-reverse diodes are provided at the output terminals of both the DCL step-down unit 1071 and the 24V power supply 1072 to prevent the load from reverse charging the DCL step-down unit 1071 and the 24V power supply 1072 during low-voltage power distribution.

[0069] Optionally, continue to refer to Figures 2 to 4The fuel cell auxiliary system 105 includes a third switch K3 and a fuel cell auxiliary unit 1051. The third switch K3 is located at the connection between the fuel cell auxiliary unit 1051 and the DC-DC module 104. The control unit 101 is connected to the third switch K3.

[0070] The third switch K3 ensures the safety of the circuit between the DC-DC module 104 and the fuel cell auxiliary unit 1051. When it is necessary to shut down the fuel cell auxiliary unit 1051, the third switch K3 can be opened to stop power supply to the fuel cell auxiliary unit 1051. When power supply to the fuel cell auxiliary unit 1051 is needed, the third switch K3 can be closed. Before closing the third switch K3, the voltage output of the unidirectional DC-DC unit 1041 can be monitored for stability. The third switch K3 can be closed only after stability is confirmed, ensuring the stability of the power supply to the fuel cell auxiliary unit 1051.

[0071] The third switch K3 is an electronic switch, and the control unit 101 can remotely control the third switch K3 to open or close.

[0072] In the above embodiments, the control unit 101 can remotely control the opening or closing of the first switch K1, the second switch K2, the first circuit breaker CB1, and the second circuit breaker CB2.

[0073] Optionally, refer to Figures 2 to 4 The fuel cell power generation system also includes a transformer isolation unit 108, which is located between the DCAC module 103 and the grid-connected circuit 106.

[0074] The transformer isolation unit 108 includes a fast-acting fuse F1 and a surge protector SPD, which can isolate and protect the entire circuit, improving the circuit's safety.

[0075] Optionally, refer to Figure 2 and Figure 4 An insulation monitor 109 is also provided between the fuel cell stack module 102 and the DCAC module 103. The insulation monitor 109 is used to detect whether there is insulation between the fuel cell stack module 102 and the DCAC module 103, that is, whether there is current between the two before the fuel cell stack module 102 outputs electrical energy, so as to infer whether the first pre-charging circuit 1022 is connected and avoid reverse charging of the fuel cell stack module 102.

[0076] Continue to refer to Figure 3 and Figure 4A voltmeter and an ammeter are provided at the output terminals of the fuel cell stack module 102, the DC side of the DCAC module 103, and the output terminals of the DC-DC module 104. The output terminal of the grid-connected circuit 106 is equipped with a voltmeter to monitor the voltage and current of these ports in real time and thus make corresponding responses.

[0077] Therefore, this power generation system is applicable to scenarios such as distributed power generation systems with AC output and requiring high dynamic response power control, and it can simplify the architecture of hydrogen fuel cell power generation systems and improve their efficiency.

[0078] Figure 5 This is a flowchart of a control method for a fuel cell power generation system provided in an embodiment of the present invention. This method is implemented based on a fuel cell power generation system according to any embodiment of the present invention, such as... Figure 5 As shown, the control methods include:

[0079] S101 controls the DCAC module to be in high-voltage rectification mode before controlling the stack module to output electrical energy, and supplies power to the fuel cell auxiliary system through the second line.

[0080] In this fuel cell power generation system, before the stack module starts working, the grid-connected circuit outputs high-voltage electricity, which is transformed and rectified by the DCAC module and then transmitted to the DCDC module, and then the DCDC module supplies power to the fuel cell auxiliary system.

[0081] S102, after controlling the stack module to output electrical energy, controls the DCAC module to be in inverter mode, transmits electrical energy to the grid-connected circuit through the first line, and simultaneously supplies power to the fuel cell auxiliary system through the third line.

[0082] After the fuel cell stack module starts working, it outputs electrical energy, which is then inverted by the DCAC module and sent to the grid-connected circuit. At the same time, it can also supply power to the fuel cell auxiliary system through the DC-DC module.

[0083] S103, after the control stack module stops outputting electrical energy, controls the DCAC module to enter uncontrolled rectification mode and supplies power to the fuel cell auxiliary system through the second line.

[0084] After the fuel cell stack module stops working, the grid-connected circuit can be restored to output high voltage. However, since the uncontrolled rectification mode of the DCAC can meet the power supply of the fuel cell auxiliary system at this time, the power is transmitted to the DC-DC module after uncontrolled rectification by the DCAC module, and then the power is supplied to the fuel cell auxiliary system through the DC-DC module.

[0085] In this context, the high-voltage rectification mode can be understood as the DCAC module's set voltage being lower than the stack module's open-circuit voltage but higher than the minimum voltage provided by the stack module to the fuel cell auxiliary system. The uncontrolled rectification mode can be understood as the DCAC module not needing to perform high-voltage rectification in the high-voltage rectification mode; the normal grid-connected circuit's 630V / AC can be rectified to 900V / DC through uncontrolled rectification.

[0086] In this way, by branching off a power supply line from the bus between the fuel cell stack module output and the DC-AC (DC-AC converter) to power the DC-DC converter, the BOP (Balanced Plant) operation of the fuel cell system is supported, thereby reducing redundant DC-DC stages, lowering the energy conversion levels, and improving system efficiency. This approach offers significant advantages in architectural topology, reducing first-stage energy conversion losses and improving system efficiency by 8%-12%. The bus voltage is autonomously adjusted by the dynamic characteristics of the fuel cell stack, avoiding multi-stage control conflicts. Integrating the BOP through bus branch power supply eliminates redundant DC-DC stages, reduces the number and complexity of system equipment, lowers system costs, and simultaneously improves system reliability and maintainability. Dynamic load control of the DC-AC is achieved, reducing terminal control deviations and enhancing dynamic response capabilities. External low-power AC power supply provides a dual-power supply of "DC + AC," and the "rectified mode + fuel cell stack output" approach enables full-condition power supply to the BOP.

[0087] Optionally, the DCAC module includes a bidirectional DCAC unit, a filter unit, and a second pre-charge circuit; the fuel cell stack module includes a fuel cell stack unit, a first pre-charge circuit, and a discharge circuit.

[0088] Before the control stack module outputs electrical energy, the control DCAC module is in high-voltage rectification mode, and power is supplied to the fuel cell auxiliary system through the second line, including:

[0089] Disconnect the first pre-charge circuit;

[0090] The second switch in the second pre-charging circuit is closed and the second circuit breaker is opened. At the same time, the bidirectional DCAC unit is controlled to be in high-voltage rectification mode and the voltage of the bidirectional DCAC unit is monitored. When the voltage of the bidirectional DCAC unit is at the first preset value, the second switch is opened and the second circuit breaker is closed so that the grid-connected circuit supplies power to the fuel cell auxiliary system through the second pre-charging circuit, the filter unit, the bidirectional DCAC unit, and the DC-DC module.

[0091] Before the fuel cell stack unit starts working, the grid-connected circuit or other load auxiliary power supply inputs electrical energy (AC10kV / 380V) to establish the critical low-voltage power supply for the system. Simultaneously, an AC630V voltage is established via a transformer, and power is supplied to the BOP sequentially through the second pre-charge circuit, the filter unit, the bidirectional DCAC unit, and the unidirectional DC-DC unit. At this time, the first pre-charge circuit needs to be disconnected to prevent the grid-connected circuit from reverse-charging the fuel cell stack unit, causing electrolysis, damage, and safety issues. Specifically, both the first switch K1 and the first circuit breaker CB1 in the first pre-charge circuit need to be disconnected.

[0092] Therefore, the first pre-charging circuit can prevent reverse charging of the fuel cell unit and ensure the safety of the circuit when the fuel cell unit outputs electrical energy.

[0093] Furthermore, before the fuel cell stack unit outputs electrical energy, the grid-connected circuit supplies power to the fuel cell auxiliary system through the DCAC module and the DC-DC module. Because the initial voltage difference between the bidirectional DCAC unit and the grid-connected circuit is relatively large, the second switch K2 can be closed first. When the voltage difference across the second circuit breaker CB2 reaches a certain value, CB2 can then be closed. This avoids sudden changes in the input voltage of the bidirectional DCAC unit, which could damage it. It also prevents arcing when the second circuit breaker CB2 is closed, further improving circuit safety. Additionally, after the fuel cell auxiliary system shuts down, the second circuit breaker CB2 can be disconnected to stop the grid-connected circuit from supplying power to the fuel cell auxiliary system.

[0094] Therefore, the second pre-charging circuit protects the bidirectional DCAC unit and also protects the entire bus line.

[0095] In the above embodiment, the first preset value is the pre-charge voltage value of the bidirectional DCAC.

[0096] Optionally, after controlling the fuel cell stack module to output electrical energy, controlling the DCAC module to be in inverter mode, supplying electrical energy to the grid-connected circuit through the first line, and simultaneously supplying power to the fuel cell auxiliary system through the third line includes:

[0097] The system controls the output of electrical energy from the fuel cell unit and monitors the overall voltage of the fuel cell unit. When the overall voltage of the fuel cell unit is greater than a second preset value, the system controls the first switch in the first pre-charging circuit to close and the first circuit breaker to open.

[0098] When the voltage difference across the first circuit breaker is within a preset threshold range, the first switch is opened and the first circuit breaker is closed. The fuel cell stack unit supplies power to the fuel cell auxiliary system through the first pre-charging circuit and the DC-DC module. The bidirectional DCAC unit is controlled to be in inverter mode so that the fuel cell stack unit can deliver electrical energy to the grid-connected circuit through the first pre-charging circuit, the bidirectional DCAC unit, the filter unit, and the second pre-charging circuit.

[0099] In other words, after the fuel cell unit starts working and the overall voltage reaches a certain value (such as 1400V), it means that the fuel cell unit can output electrical energy. At this time, the first switch K1 can be closed first and the first circuit breaker CB1 can be opened. When the voltage across the first circuit breaker CB1 is slightly balanced, the first circuit breaker CB1 can be closed again and the first switch K1 can be opened. This can prevent arcing when the first circuit breaker CB1 is closed.

[0100] At this time, the bidirectional DCAC unit is in inverter mode, and the stack unit can supply power to the grid-connected circuit through the first pre-charging circuit, the bidirectional DCAC unit, the filter unit, and the second pre-charging circuit; it can also supply power to the fuel cell auxiliary system through the first pre-charging circuit and the DC-DC module.

[0101] The preset threshold range in the above embodiments is ±a, and the value of a can be set according to specific circumstances.

[0102] Optionally, after the control stack module stops outputting electrical energy, the control DCAC module is in rectification mode, and supplies power to the fuel cell auxiliary system through the second line, including:

[0103] The control unit stops outputting electrical energy and performs a purge shutdown on the fuel cell unit;

[0104] After the fuel cell stack unit is purged and shut down, the control discharge circuit discharges the voltage of the fuel cell stack unit in stages. Specifically, when the DC bus voltage is lower than the third preset value (900V), the first pre-charge circuit is disconnected; the bidirectional DCAC unit is controlled to be in uncontrolled rectification mode so that the grid-connected circuit supplies power to the fuel cell auxiliary system through the second pre-charge circuit, the filter unit, the bidirectional DCAC unit, and the DC-DC module; the discharge continues through the discharge circuit until the discharge voltage reaches the fourth preset value (60V), at which point the second pre-charge circuit is disconnected.

[0105] In other words, after the fuel cell stack unit stops working, the first circuit breaker CB1 needs to be disconnected to prevent reverse power supply to the fuel cell stack unit due to the low voltage of the stack unit. Then, the bidirectional DCAC unit is in uncontrolled rectification mode so that the grid-connected circuit can supply power to the fuel cell auxiliary system through the second pre-charge circuit, the filter unit, the bidirectional DCAC unit, and the DC-DC module, thereby ensuring uninterrupted power supply to the fuel cell auxiliary system.

[0106] The venting circuit is mainly used to release the residual pressure of the fuel cell stack unit after it stops working, so as to ensure the normal operation of the fuel cell stack unit and the safety of the entire fuel cell system.

[0107] In one specific embodiment, the operation of the fuel cell power generation system is carried out according to the following steps:

[0108] 1. Grid-connected or other load auxiliary power input (AC10kV / 380V) to establish the critical low-voltage power supply of the system, and at the same time establish AC630V voltage through the transformer;

[0109] 2. The system starts up. The control unit issues a start command, sends a high-voltage rectification mode command to the DCAC module, disconnects the first pre-charge circuit, starts the inverter to enter the high-voltage rectification mode, and completes the input pre-charge and output pre-charge of the DCAC module respectively.

[0110] 3. After the rectified voltage is set to stabilize, precharge the output of the DC-DC module to establish a high voltage DC650V BOP and connect the DCL step-down unit to a low voltage DC24V.

[0111] IV. The fuel cell module starts up, and the BOP starts working at the same time. When the average cell voltage of the stack is >0.8V, the fuel cell stack has the ability to connect, and the first pre-charge circuit is closed. The stack outputs power to the outside and the output current is detected at the same time.

[0112] V. As the fuel cell stack output replaces the DCAC module rectifier output and a stable BOP supply is achieved, the control unit sends a high-voltage rectification mode switching inverter mode command to the DCAC module. The inverter enters the inverter working mode, and the control unit adjusts the gas supply and active power output based on the required power.

[0113] 6. After the work is completed, the control unit issues a shutdown command to control the fuel cell module to purge and shut down. After the fuel cell stack purge process is completed, the fuel cell system is shut down to maintain pressure.

[0114] 7. When the pressure holding begins, the fuel cell module BOP is in standby mode. At this time, the bus is close to open circuit, the first pre-charge circuit is disconnected, and the DCAC module switches back to uncontrolled rectification mode to achieve seamless power supply to the BOP.

[0115] 8. At this time, the air compressor ensures the purging of the fuel cell stack and the concentration of hydrogen in the exhaust gas, and the water pump ensures that the water temperature before shutdown is maintained below the set value.

[0116] 9. When starting to discharge the fuel cell module and discharging the residual power, the discharge resistance is gradually reduced as the voltage at the output terminal of the fuel cell stack decreases, so as to achieve the discharge of the fuel cell stack within a limited time.

[0117] 10. When the residual charge of the fuel cell stack is discharged to the set holding voltage value, the control unit controls the discharge circuit to stop discharging and enters the system shutdown holding voltage standby state;

[0118] 11. After the BOP completes shutdown, perform high-voltage standby or low-voltage standby as required.

[0119] In other words, Figure 6 This is a flowchart of a control method for a fuel cell power generation system according to a specific embodiment of the present invention, for reference. Figure 6 Initially, close the relevant switches for the UPS and DC24V power supply to power on the DC24V power. Then, the DCAC module starts, performing input and output pre-charge. Next, control the DCAC module to enter high-voltage rectification mode to establish the DC high voltage on the bus, start the DC-DC module, establish the BOP DC high voltage, and start the DCL step-down unit. At this point, both high-voltage and low-voltage power supplies are established, allowing the BOP to start. Then, control the fuel cell stack module to output power. When the average total voltage of the fuel cell stack is greater than 1400V, establish the connection between the fuel cell stack module and the DCAC module, i.e., close the first pre-charge circuit. Then, the fuel cell stack begins current traction, outputting current. The DCAC module operates in inverter mode, with no conflict between the fuel cell stack output voltage and the BOP supply voltage. The fuel cell stack's load current is the DC-DC input current minus the DCAC output current. After the fuel cell stack receives a shutdown command and stops, it performs fuel cell stack purging. After purging is completed, the fuel cell stack can be charged and discharged. When the output voltage of the fuel cell stack module is less than 900V, the first pre-charge circuit is disconnected, the DCAC is in uncontrolled rectification mode, the BOP works continuously, and the discharge circuit continues to discharge voltage. When the discharge voltage is less than 60V, the discharge is completed, the system stops, and the process ends.

[0120] Therefore, the power generation system mainly consists of key components such as PCS (filter unit, bidirectional DCAC unit, etc.), control unit, fuel cell stack module, fuel cell BOP, unidirectional DC-DC unit, switch, and circuit breaker. The DC power output from the fuel cell is directly input to the PCS for inversion, and the AC power output is sent to the transformer to provide power energy to the load / grid. The branch circuit is converted by DC-DC to power the fuel cell BOP, which provides the necessary hydrogen, air, water temperature, etc. for the fuel cell reaction to the fuel cell module.

[0121] Furthermore, the system can integrate a BOP (Balance of Plant) via bus branch power supply. By utilizing DC-AC mode switching and combining the stack VI (Variable Identification and Control) characteristics, it maintains the bus voltage range, ensuring the DC-DC input voltage remains within the stack's operating range. It also dynamically adjusts gas distribution and current load through DC-AC load current and real-time monitoring of system power demand and stack output current, ensuring stable and efficient system operation. The stack output current is adjusted based on actual active power output. Thus, utilizing the fuel cell characteristics, a control logic scheme with AC power supply before startup, DC power supply after startup, and AC backup provides dual power supply, improving the stability of low-voltage power supply. Moreover, during shutdown, by disconnecting the first pre-charge circuit and switching the inverter to rectification, DC-DC power supply is maintained while residual hydrogen is discharged through an independent discharge circuit, ensuring a safe system shutdown.

[0122] In summary, the fuel cell power generation system and control method provided by the embodiments of the present invention include: a control unit, and a fuel cell stack module, a DCAC module, a DC-CDC module, and a fuel cell auxiliary system respectively connected to the control unit; the fuel cell stack module, the DCAC module, and the grid-connected circuit are sequentially connected to form a first line; the grid-connected circuit, the DCAC module, the DC-CDC module, and the fuel cell auxiliary system are sequentially connected to form a second line; and the fuel cell stack module, the DCAC module, the DC-CDC module, and the fuel cell auxiliary system are sequentially connected to form a third line; the control unit is used to control whether the fuel cell stack module outputs electrical energy, and also to control the DCAC module to switch between rectification mode and inverter mode, so as to switch the second line and the third line to supply power to the fuel cell auxiliary system, wherein the DC-CDC module is located on a branch bus of the bus where the DCAC module is located. This system can improve system efficiency, simplify system architecture, increase dynamic response capability, and has both high-voltage and low-voltage power supply capabilities.

[0123] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0124] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A fuel cell power generation system, characterized in that, include: The grid-connected circuit and control unit, as well as the fuel cell stack module, DCAC module, DCCDC module, and fuel cell auxiliary system connected to the control unit respectively; The fuel cell stack module, the DCAC module, and the grid-connected circuit are connected in sequence to form a first circuit; the grid-connected circuit, the DCAC module, the DC-DC module, and the fuel cell auxiliary system are connected in sequence to form a second circuit; and the fuel cell stack module, the DCAC module, the DC-DC module, and the fuel cell auxiliary system are connected in sequence to form a third circuit. The control unit is used to control the output of electrical energy of the fuel cell stack module, and also to control the DCAC module to switch between rectification mode and inverter mode, so as to switch the second line and the third line to supply power to the fuel cell auxiliary system. The DC-DC module is located on a branch bus of the bus where the DCAC module is located.

2. The fuel cell power generation system according to claim 1, characterized in that, The fuel cell stack module includes a fuel cell stack unit, a first pre-charge circuit, and a discharge circuit. The output terminal of the fuel cell stack unit is connected to one end of the first pre-charge circuit, and the other end of the first pre-charge circuit is connected to the DCAC module and the DCDC module. The discharge circuit is located at the output terminal of the fuel cell stack unit. The first pre-charge circuit includes a first resistor, a first switch, and a first circuit breaker. The first circuit breaker is located between the output terminal of the fuel cell unit and the DCAC module. The first resistor and the first switch form a first series branch. The two ends of the first series branch are connected in parallel to the two ends of the first circuit breaker. The control unit is connected to the first pre-charge circuit and the discharge circuit.

3. The fuel cell power generation system according to claim 1, characterized in that, The DCAC module includes: a bidirectional DCAC unit, a filter unit, and a second pre-charging circuit. One end of the bidirectional DCAC unit is connected to the fuel cell stack module and the DC-DC module. The other end of the bidirectional DCAC unit is connected to one end of the filter unit. The other end of the filter unit is connected to one end of the second pre-charging circuit. The other end of the second pre-charging circuit is connected to the grid-connected circuit. The second pre-charging circuit includes a second resistor, a second switch, and a second circuit breaker. The second circuit breaker is located between the filter unit and the grid-connected circuit. The second resistor and the second switch form a second series branch. The two ends of the second series branch are connected in parallel to the two ends of the second circuit breaker. The bidirectional DCAC unit and the second pre-charging circuit are both connected to the control unit.

4. The fuel cell power generation system according to claim 1, characterized in that, It also includes a low-voltage power supply module, which includes a DCL step-down unit and a UPS power supply unit. The grid-connected circuit, the DCAC module, the DC-DC module and the DCL step-down unit form a fourth line, and the fuel cell stack module, the DC-DC module and the DCL step-down unit form a fifth line. The DCL step-down unit is used to draw power from the DCDC module and step down the voltage, and the UPS power supply unit is used to draw power from AC 220V.

5. The fuel cell power generation system according to claim 1, characterized in that, It also includes a transformer isolation unit, which is located between the DCAC module and the grid-connected circuit.

6. The fuel cell power generation system according to claim 1, characterized in that, The fuel cell auxiliary system includes a third switch and a fuel cell auxiliary unit. The third switch is located at the connection between the fuel cell auxiliary unit and the DC-DC module, and the control unit is connected to the third switch.

7. A control method for a fuel cell power generation system, characterized in that, Based on the fuel cell power generation system as described in any one of claims 1-6, the control method includes: Before the control stack module outputs electrical energy, the control DCAC module is in high-voltage rectification mode and supplies power to the fuel cell auxiliary system through the second line; After controlling the stack module to output electrical energy, the DCAC module is controlled to enter inverter mode, supplying electrical energy to the grid-connected circuit through the first line, and simultaneously supplying power to the fuel cell auxiliary system through the third line. After controlling the stack module to stop outputting electrical energy, the DCAC module is controlled to enter uncontrolled rectification mode, supplying power to the fuel cell auxiliary system through the second line.

8. The control method for a fuel cell power generation system according to claim 7, characterized in that, The DCAC module includes a bidirectional DCAC unit, a filtering unit, and a second pre-charge circuit; the fuel cell stack module includes a fuel cell stack unit, a first pre-charge circuit, and a discharge circuit. Before controlling the stack module to output electrical energy, controlling the DCAC module to be in high-voltage rectification mode and supplying power to the fuel cell auxiliary system through the second line includes: Disconnect the first pre-charge circuit; The system controls the second switch in the second pre-charging circuit to close and the second circuit breaker to open. Simultaneously, it controls the bidirectional DCAC unit to be in high-voltage rectification mode and monitors the voltage of the bidirectional DCAC unit. When the voltage of the bidirectional DCAC unit is at a first preset value, it controls the second switch to open and the second circuit breaker to close, so that the grid-connected circuit supplies power to the fuel cell auxiliary system through the second pre-charging circuit, the filter unit, the bidirectional DCAC unit, and the DC-DC module.

9. The control method for a fuel cell power generation system according to claim 8, characterized in that, After controlling the stack module to output electrical energy, controlling the DCAC module to enter inverter mode, supplying electrical energy to the grid-connected circuit through the first line, and simultaneously supplying power to the fuel cell auxiliary system through the third line includes: The system controls the output of electrical energy from the fuel cell unit and monitors the overall voltage of the fuel cell unit. When the overall voltage of the fuel cell unit is greater than a second preset value, the system controls the first switch in the first pre-charging circuit to close and the first circuit breaker to open. When the voltage difference across the first circuit breaker is within a preset threshold range, the first switch is opened and the first circuit breaker is closed, and the fuel cell stack unit supplies power to the fuel cell auxiliary system through the first pre-charging circuit and the DC-DC module. The bidirectional DCAC unit is controlled to be in inverter mode, and the fuel cell unit supplies power to the grid-connected circuit through the first pre-charging circuit, the bidirectional DCAC unit, the filter unit, and the second pre-charging circuit.

10. The control method for a fuel cell power generation system according to claim 8, characterized in that, After controlling the stack module to stop outputting electrical energy, controlling the DCAC module to be in uncontrolled rectification mode and supplying power to the fuel cell auxiliary system through the second line includes: controlling the stack unit to stop outputting electrical energy and purging and shutting down the stack unit; After the fuel cell stack unit is purged and shut down, the discharge circuit is controlled to discharge the voltage of the fuel cell stack unit in stages. Specifically, when the DC bus voltage is lower than a third preset value, the first pre-charge circuit is disconnected; the bidirectional DCAC unit is controlled to be in uncontrolled rectification mode so that the grid-connected circuit supplies power to the fuel cell auxiliary system through the second pre-charge circuit, the filter unit, the bidirectional DCAC unit, and the DC-DC module, and continues to discharge through the discharge circuit. When the discharge voltage reaches the fourth preset value, the second pre-charge circuit is disconnected.

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