Fuel cell power generation system and control method thereof

Abstract

The invention discloses a fuel cell power generation system and a control method thereof, and the system controls the current of a fuel cell stack through the following method on the architecture that one path is branched from a bus between the output of the fuel cell stack and a DCAC (direct current-direct current converter) to supply power to the DCDC (direct current-direct current converter). The method comprises the following steps: acquiring a first difference value between an actual power value of a grid-connected / load and a target power value, and generating a reference current variation based on the first difference value and a power controller; obtaining a target current value of the fuel cell stack, and generating a reference current value based on the reference current variable quantity and the target current value; acquiring an actual current value output by the fuel cell stack; obtaining a current control value based on the reference current value, the actual current value and a current controller; and the fuel cell stack is controlled based on the current control value, so that closed-loop control of the power of the fuel cell can be realized, the system architecture is simplified, the system efficiency is improved, and the dynamic response capability is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of power generation systems, and in particular to a fuel cell power generation system and a control method thereof. Background Art

[0002] In existing technologies, fuel cell systems typically connect a DC-DC (Direct Current Control) and DC-AC (Direct Current Alternating Current) in series on a voltage bus. The DC-CDC provides the DC power required by both the BOP and the DC-AC, each of which is independently controlled. The DC-AC is responsible for converting the DC power output by the fuel cell stack into AC power for the load. This independent control approach can meet the system's power requirements to a certain extent, but it has shortcomings in the following architectural design and control aspects:

[0003] Irrational power allocation: Under high load conditions, both DCAC and DCCDC may require significant power simultaneously, causing bus voltage fluctuations and impacting system stability. Energy loss: Due to the lack of a dynamic power allocation mechanism, the system may not fully utilize the stack's output power in certain situations, resulting in energy waste. System complexity: Independent control requires additional control modules, increasing system complexity and cost. Single-loop control limitations: Using only current loop control, it is unable to directly track power demand. Insufficient disturbance compensation: The coupled effects of BOP power fluctuations, DCAC efficiency changes, and stack dynamic delays are not considered. Static database reliance: BOP power prediction and efficiency compensation rely on fixed parameter tables, making them unable to adapt to changing operating conditions. Summary of the Invention

[0004] The present invention provides a fuel cell power generation system and a control method thereof, which can simplify the architecture of the hydrogen fuel cell power generation system, improve the efficiency of the hydrogen fuel cell power generation system, and enhance the dynamic response capability.

[0005] According to one aspect of the present invention, a control method for a fuel cell power generation system is provided. The fuel cell power generation system includes at least a bidirectional DCAC module, a bidirectional DCDC module, a fuel cell stack, and a fuel cell auxiliary system. The output end of the fuel cell stack is connected to a DC bus, and the DC bus is divided into a first branch and a second branch. The first branch is converted by the bidirectional DCAC module to grid / load power supply, and the second branch is converted by the bidirectional DCDC module to power the fuel cell auxiliary system.

[0006] The control method includes:

[0007] Obtaining a first difference between an actual power value of the grid / load and a target power value, and generating a reference current variation based on the first difference and a power controller;

[0008] Acquiring a target current value of the fuel cell stack, and generating a reference current value based on the reference current variation and the target current value;

[0009] Obtain the actual current value output by the fuel cell stack;

[0010] Obtaining a current control value based on the reference current value, the actual current value, and a current controller;

[0011] The fuel cell stack is controlled based on the current control value.

[0012] Optionally, obtaining a target current value of the fuel cell stack includes:

[0013] Acquiring an actual voltage value of the DC bus, and acquiring the power prediction value of the fuel cell auxiliary system based on a corresponding relationship between the actual voltage value and the power prediction value;

[0014] Obtaining a conversion efficiency of the bidirectional DCAC module according to an interpolation efficiency table corresponding to the target power value and the actual voltage value;

[0015] The target current value is calculated based on the power prediction value, the actual voltage value, the conversion efficiency of the bidirectional DCAC module, and the target power value.

[0016] Optionally, the reference current variation The following conditions are met: ;

[0017] in, ; ; is the actual power value, is the target power value, is the first difference, is the reference current variation, are the proportional coefficient and integral coefficient of the power controller respectively, is the integral at the current moment;

[0018] The target current value The following conditions are met: ;in, is the power prediction value, is the conversion efficiency of the bidirectional DCAC module, is the actual voltage value;

[0019] The current control value The following conditions are met: ,in, , , are the proportional coefficient and differential coefficient of the current controller respectively, is the reference current value, is the actual current value, is the deviation of the current controller, is the number of iterations.

[0020] Optionally, after obtaining the current control value based on the reference current value, the actual current value and the current controller, the method further includes: calculating a compensation amount for the reference current value based on the current control value and the Smith predictor;

[0021] Generating a reference current value based on the reference current variation and the target current value includes generating the reference current value based on the reference current variation, the target current value, and the compensation amount.

[0022] Optionally, the reference current value after compensation The following conditions are met: , is the compensation amount; wherein, , , , , is the inertia time constant of the fuel cell stack, is the delay time of the fuel cell power generation system, is the compensation amount stored in each iteration of the Smith predictor, After updating the queue for each iteration, the queue at the head of the queue , is the number of delay steps, is the coefficient of the equation.

[0023] Optionally, before obtaining a first difference between the actual power value of the grid / load and the target power value, and generating a reference current variation based on the first difference and a power controller, the method further includes:

[0024] Controlling the auxiliary power supply input power of the grid / load, and controlling the bidirectional DCAC module to be in a rectification mode, to complete input pre-charging and output pre-charging of the bidirectional DCAC module;

[0025] When the output pre-charge of the bidirectional DCAC module reaches a first preset voltage, performing input pre-charge and output pre-charge on the bidirectional DCDC module;

[0026] When the output pre-charge of the DCDC module reaches a second preset voltage, controlling the fuel cell auxiliary system to operate and controlling the fuel cell stack to start operating;

[0027] When the average cell voltage of the fuel cell stack reaches a third preset voltage and the voltage difference between the output side of the fuel cell stack and the output side of the bidirectional DCAC module is within a threshold range, the bidirectional DCAC module is controlled to be in an inverter mode.

[0028] Optionally, the fuel cell power generation system further comprises a transformer and a filter, wherein the transformer is located between the bidirectional DCAC module and the grid / load, and the filter is located between the fuel cell stack and the bidirectional DCAC module;

[0029] The input power is AC10KV / 380V, and the transformer establishes a voltage of AC630V.

[0030] Optionally, the fuel cell power generation system further includes a diode, the positive electrode of the diode is connected to the fuel cell stack, and the negative electrode is connected to the filter and the bidirectional DCDC module respectively.

[0031] Optionally, the fuel cell power generation system further includes a discharge module, and the control method further includes:

[0032] After controlling the fuel cell stack to finish working, the stack is purged, and after the stack purge is completed, the fuel cell auxiliary system is controlled to be in a standby state;

[0033] controlling the discharge module to discharge the voltage of the fuel cell stack, and controlling the bidirectional DCAC module to shut down when the voltage of the bidirectional DCDC module reaches a fourth preset voltage;

[0034] When the voltage of the fuel cell stack reaches a fifth preset voltage, the discharge module is controlled to stop discharging the voltage of the fuel cell stack.

[0035] According to another aspect of the present invention, a fuel cell power generation system is provided, comprising: a bidirectional DCAC module, a bidirectional DCDC module, a fuel cell stack, and a fuel cell auxiliary system, wherein the output end of the fuel cell stack is connected to a DC bus, and the DC bus is divided into a first branch and a second branch. The first branch is converted by the bidirectional DCAC module to supply power to the grid / load, and the second branch is converted by the bidirectional DCDC module to supply power to the fuel cell auxiliary system.

[0036] Also included: at least one processor; and

[0037] a memory communicatively connected to the at least one processor; wherein,

[0038] The memory stores a computer program that can be executed by the at least one processor, and the computer program is executed by the at least one processor so that the at least one processor can execute the control method of the fuel cell power generation system according to any embodiment of the present invention.

[0039] The technical solution of an embodiment of the present invention is to control the current of the fuel cell stack in the following way on an architecture in which a branch is made on the bus between the output of the fuel cell stack and the DCAC (direct current-alternating current converter) to power the DCDC (direct current-direct current converter), namely, obtaining a first difference between the actual power value of the grid / load and the target power value, generating a reference current change based on the first difference and a power controller; obtaining a target current value of the fuel cell stack, and generating a reference current value based on the reference current change and the target current value; obtaining the actual current value output by the fuel cell stack; obtaining a current control value based on the reference current value, the actual current value and the current controller; and controlling the fuel cell stack based on the current control value, so as to achieve closed-loop control of the power of the fuel cell, simplify the architecture of the hydrogen fuel cell power generation system, improve the efficiency of the hydrogen fuel cell power generation system, and enhance the dynamic response capability.

[0040] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 It is an electrical topology diagram of a fuel cell power generation system in the related art;

[0043] Figure 2 is an electrical topology diagram of another fuel cell power generation system in the related art;

[0044] Figure 3 This is an electrical topology diagram of a fuel power generation system proposed in an embodiment of the present invention;

[0045] Figure 4 is a flow chart of a control method for a fuel cell power generation system proposed in an embodiment of the present invention;

[0046] Figure 5 This is a control logic block diagram of a fuel cell power generation system proposed in an embodiment of the present invention;

[0047] Figure 6 This is an estimation logic block diagram of the Smith estimator in the control method of the fuel cell power generation system proposed in an embodiment of the present invention;

[0048] Figure 7 This is an operation logic diagram of a power generation system in a control method of a fuel cell power generation system proposed in an embodiment of the present invention;

[0049] Figure 8 It is a structural diagram of a control device for implementing a control method for a fuel cell power generation system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0051] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0052] Figure 1 This is the electrical topology diagram of the fuel cell power generation system in the related art. Figure 2 This is an electrical topology diagram of another fuel cell power generation system in the related art, such as Figure 1 and Figure 2 As shown, in this power generation system, the stack output is connected to the DCAC after being stabilized by an independent DCDC, and the BOP is powered by an independent DCDC after being stabilized (as shown in Figure 1 ), or powered by another independent DCDC (as shown Figure 2As shown). They generally use the DCAC pre-stage DCDC to force the bus voltage to be regulated, sacrificing the natural characteristics of the stack, and are open-loop power control, that is, the stack output is controlled based on a preset current value, and the load demand is not dynamically tracked. In other words, the multi-stage DCDC architecture is widely adopted, which controls the stack output and BOP power supply respectively through two-stage DCDC. Although it can stabilize the bus voltage, it has the following defects: Efficiency loss: Multi-stage DCDC conversion leads to reduced system efficiency (additional loss of 5%-10%). Poor dynamic response: DCDC cascade delay affects the power tracking speed, making it difficult to cope with sudden load changes. Cost and volume: Multi-stage power devices increase hardware complexity and cost.

[0053] Specifically, significant efficiency losses occur due to forced voltage regulation, which requires the DC-DC converter to continuously adjust the stack's output current and voltage. This requires additional conversion steps (such as step-down, step-up, and step-down / step-up) for the DC-DC voltage regulation, resulting in energy losses (approximately 3-5%) or reliance on large-capacity capacitors for buffering, increasing size and cost. This causes the stack's operating point to deviate from its optimal efficiency zone, compounding the DC-DC converter's own losses and increasing size and cost. Bus voltage fluctuations and dynamic response delays arise from the series connection of multiple control loops (DCDC voltage loop + DC / AC power loop). When load power suddenly changes, the stack's response speed is limited by electrochemical reactions (with millisecond-level lags), causing instantaneous bus voltage drops / rises. The BOP supply voltage exceeds the DC-DC input range, triggering a system shutdown. This results in large bus voltage fluctuations under step loads and significant power overshoot / undershoot. Inadequate dynamic response stems from the fact that the fixed bus voltage design cannot adapt to the stack's output characteristics (e.g., voltage drops as current increases), resulting in poor system load responsiveness and low efficiency at light loads. The complexity of the system and the BOP power supply is due to the fact that the BOP needs to draw power from the fuel cell stack through independent DCDC. Independent control requires an additional control module, resulting in competitive power distribution between the fuel cell stack and the BOP. The control logic is highly coupled, which increases the complexity and cost of the system.

[0054] To solve the above problems, an embodiment of the present invention provides a fuel cell power generation system and a control method thereof, which will be described in detail below with reference to the accompanying drawings.

[0055] Figure 3 This is the electrical topology diagram of the fuel power generation system proposed in the embodiment of the present invention. Figure 3 As shown, the fuel cell power generation system includes at least a bidirectional DCAC module 101, a bidirectional DCDC module 102, a fuel cell stack 103 and a fuel cell auxiliary system 104, wherein the output end of the fuel cell stack 103 is connected to a DC bus, and the DC bus is divided into a first branch and a second branch. The first branch is converted by the bidirectional DCAC module 101 to power the grid / load 107, and the second branch is converted by the bidirectional DCDC module 102 to power the fuel cell auxiliary system 104.

[0056] Among them, the fuel cell auxiliary system 104 is the fuel cell module BOP (Balance of Plant), the balance system of the fuel cell system, including compressors, radiators, hydrogen circulation pumps and other equipment to ensure the normal operation of the fuel cell system. The bidirectional DCDC module 102 is a DC-DC converter used to adjust the DC voltage and provide the required voltage for other devices in the system. The bidirectional DCAC module 101 is a DC-AC converter that converts the DC power generated by the fuel cell stack 103 into AC power. The busbar is a common voltage transmission line connecting the output of the fuel cell stack 103 with the bidirectional DCAC module 101 and the bidirectional DCDC module 102.

[0057] It should be noted that when the fuel cell stack 103 outputs power, it supplies the grid / load 107 via the bidirectional DCAC module and supplies the fuel cell auxiliary system 104 via the bidirectional DC-DC module. Closed-loop control of the fuel cell stack 103's output power is implemented based on the power requirements of the grid / load 107. By branching off a bus between the fuel cell stack 103 output and the bidirectional DCAC module 101 (DC-AC converter) to power the bidirectional DC-DC module 102 (DC-DC converter), the fuel cell system's balance of power (BOP) is supported. This reduces redundant DC-DC links, lowers the number of energy conversion levels, and improves system efficiency. This architectural topology offers significant advantages, reducing primary energy conversion losses and increasing system efficiency by 8%-12%. The bus voltage is autonomously adjusted based on the stack's dynamic characteristics, avoiding multi-level control conflicts. Furthermore, integrating the BOP with bus branch power eliminates redundant DC-DC links, reduces the number and complexity of system equipment, lowers system costs, and improves system reliability and maintainability.

[0058] Figure 4 This is a flow chart of a control method for a fuel cell power generation system proposed in an embodiment of the present invention. Figure 5 This is a control logic block diagram of the fuel cell power generation system proposed in an embodiment of the present invention. Figure 4 and Figure 5 As shown, the control method includes:

[0059] S101 , obtaining a first difference between an actual power value of a grid / load and a target power value, and generating a reference current variation based on the first difference and a power controller.

[0060] When the fuel cell stack outputs electrical energy, it primarily supplies power to the load. At this point, a target power value can be set based on the load's power requirements, while the actual power value can be acquired via a power sensor. The difference between the two values ​​is then calculated and adjusted by a power controller to ensure that the actual power value reaches the target power value. This power controller can be a PID controller.

[0061] This link is the outer-loop power regulation process. Since the outer-loop power regulation actually adjusts the control current of the fuel cell stack, the reference current change can be calculated through the first difference. That is, the actual power value needs to be superimposed on the first difference to reach the target power value, then the corresponding fuel cell stack output current needs to be superimposed on the reference current change corresponding to the above-mentioned first difference.

[0062] S102 , obtaining a target current value of the fuel cell stack, and generating a reference current value based on the reference current variation and the target current value.

[0063] This step is the inner loop current regulation process. After the reference current variation is obtained in S101, the target current value of the fuel cell stack in this cycle is the sum of the current of the fuel cell auxiliary system branch and the grid / load branch in the previous cycle. The reference current value is then the sum of the reference current variation and the target current value. The reference current value can also be understood as the required current value of the entire power generation system in the current cycle.

[0064] S103, obtaining the actual current value output by the fuel cell stack.

[0065] Among them, the actual current value output by the fuel cell stack can be collected by a current sensor.

[0066] S104 , obtaining a current control value based on the reference current value, the actual current value, and the current controller.

[0067] The current controller may be a PID controller. After obtaining the reference current value and the actual current value, the current control value (ie, the output value of the current controller) may be obtained through PID regulation.

[0068] S105, controlling the fuel cell stack based on the current control value.

[0069] By outputting the output value of the current controller to the fuel cell stack, the output current of the fuel cell stack is controlled accordingly, so that the output current of the fuel cell stack can reach the required current value of the entire power generation system in the current cycle, and then reach the target power value to meet the actual power value of the load.

[0070] This, combined with the natural VI characteristics of the fuel cell stack, enables dynamic maintenance of bus voltage and high-precision tracking of DC / AC output power, improving the system's response speed and accuracy to dynamic power demands. It also forms a closed-loop power control logic for the fuel cell system.

[0071] In one embodiment, the power closed-loop control logic system may include a host computer, an outer-loop power control module, an inner-loop current control module, a grid / load power collector, and a fuel cell stack output current collector. The output of the host computer and the output of the grid / load power collector are both connected to the input of the outer-loop power control module; the output of the outer-loop power control module and the output of the fuel cell stack output current collector are respectively connected to the input of the inner-loop current control module; the output of the inner-loop current control module is connected to the current signal control terminal of the fuel cell stack; and the output of the fuel cell stack is connected to the input of the fuel cell stack output current collector.

[0072] Among them, the host computer is used to send the target power value, the grid / load power collector is used to collect the actual power value, the outer loop power control module is used to perform PID control based on the deviation between the target power value and the current actual power value, and output the reference current change amount that the current needs to change in the current cycle. Then, based on the current value required by the entire power generation system in the previous cycle and the sum of the reference current change amount in this cycle, as the current value to be achieved by the entire power generation system in the current cycle, the fuel cell stack output current collector is used to collect the actual current value output by the fuel cell stack. Then, the inner loop current control module performs PID control on the deviation between the current value to be achieved by the entire power generation system and the actual current value output by the fuel cell stack, and outputs the current control amount required for the fuel cell stack in the current cycle, and controls it so that the actual current value of the fuel cell stack reaches the current value to be achieved by the entire power generation system as much as possible.

[0073] Therefore, closed-loop control of the output power of the fuel cell stack can be achieved through the power controller and the current controller, with a simple architecture, closed-loop control, and fast response speed.

[0074] Optionally, obtaining a target current value of the fuel cell stack includes:

[0075] Obtaining an actual voltage value of the DC bus, and obtaining a power prediction value based on a corresponding relationship between the actual voltage value and a power prediction value of the fuel cell auxiliary system;

[0076] Obtain the conversion efficiency of the bidirectional DCAC module based on the interpolation efficiency table corresponding to the target power value and the actual voltage value;

[0077] The target current value is calculated based on the power prediction value, the actual voltage value, the conversion efficiency of the bidirectional DCAC module, and the target power value.

[0078] It can be understood that the target current value of the fuel cell stack is the sum of the currents of the first branch and the second branch in the previous cycle. It can also be understood as the ratio of the fuel cell stack's output power to its output voltage. In one embodiment, a correspondence between the actual voltage value of the DC bus and the predicted power value of the fuel cell auxiliary system can be pre-stored. Once the actual voltage value of the DC bus is measured, the predicted power value of the second branch can be obtained. Furthermore, the conversion efficiency of the bidirectional DCAC module can be obtained by using a pre-stored interpolation efficiency table corresponding to the target power value and actual voltage value of the first branch. Based on the actual voltage value and this conversion efficiency, the power value of the first branch before conversion by the bidirectional DCAC module can be obtained. Consequently, the power of both the first branch and the second branch can be calculated. Ultimately, the target current value is calculated based on the predicted power value, the actual voltage value, the conversion efficiency of the bidirectional DCAC module, and the target power value.

[0079] Optionally, the reference current variation The following conditions are met: ;

[0080] in, ; ; is the actual power value, is the target power value, is the first difference, is the reference current variation, are the proportional coefficient and integral coefficient of the power controller respectively, is the integral at the current moment;

[0081] The target current value The following conditions are met: ;in, is the power prediction value, is the conversion efficiency of the bidirectional DCAC module, is the actual voltage value;

[0082] The current control value The following conditions are met: ,in, , , are the proportional coefficient and differential coefficient of the current controller respectively, is the reference current value, is the actual current value, is the deviation of the current controller, is the number of iterations.

[0083] in, is the power proportional coefficient, the typical value is 0.5-2A / kW, is the power integration coefficient, with a typical value of 0.5-2A / kW·s. When Z is integrated, anti-integral saturation processing is performed. , reset the points to 0, otherwise . is the current proportional coefficient, the typical value is 0.8-1.5, is the current differential coefficient, with a typical value of 0.05-1.2. Furthermore, the current of the fuel cell stack can be closed-loop regulated through the power controller and current controller.

[0084] Optionally, after obtaining the current control value based on the reference current value, the actual current value and the current controller, the method further includes: calculating a compensation amount of the reference current value based on the current control value and a Smith predictor;

[0085] Generating the reference current value based on the reference current variation and the target current value includes generating the reference current value based on the reference current variation, the target current value, and the compensation amount.

[0086] It is understandable that since the fuel cell power generation system as a whole has dynamic delay characteristics, including inertial delay (dynamic first-order inertial response of the stack reaction) and transmission delay (communication delay between signal acquisition and actuator), the Smith predictor can be used to compensate for the delay to improve the control accuracy of the overall system.

[0087] Among them, the process model of the Smith predictor is defined as the transfer function is ,in, For gain, is the pure lag time, is the inertia time constant of the fuel cell stack, In order to delay the fuel cell power generation system, in practical applications, it is necessary to convert the continuous-time controller into discrete-time controller so that it can be implemented on a microprocessor or DSP. The zero-order hold is a commonly used method that can simulate the sampling and holding process of the actual system.

[0088] In order to implement the Smith predictor and parameter identification algorithm in the digital controller, the continuous model and controller need to be discretized and the zero-order holder is used for discretization. The time delay link in the continuous system is usually converted in the discrete system. However, if Instead of using integer multiples of the period, fractional time delay processing may be required, such as using Thiran filters or interpolation methods, performed in discrete time, and more explicitly expressing the difference equation in the form of discrete difference equations.

[0089] Consider the discretization process of the entire control system, convert the continuous-time prediction model into a discrete model, and integrate it into the control loop. First, discretize it, and then build a discrete version of the Smith predictor.

[0090] The difference equation is The transfer function of the zero-order holder is , is the discretized time.

[0091] Optionally, the compensated reference current value The following conditions are met: , is the compensation amount; , , , , is the inertia time constant of the fuel cell stack, Delay time for the fuel cell power generation system, The compensation amount stored in each iteration of the Smith estimator, After updating the queue for each iteration, the queue at the head of the queue , is the number of delay steps, is the coefficient of the equation.

[0092] Figure 6 This is an estimation logic block diagram of the Smith estimator in the control method of the fuel cell power generation system proposed in the embodiment of the present invention. Figure 6 As shown, Figure 6 The controller in is a current controller. When the current controller outputs the current control quantity, the Smith estimator calculates the Smith compensation of the reference current value at the next moment based on the current control quantity, that is, The Smith compensation value of the reference current value at the next moment is stored in the delay queue, and finally taken out according to the number of delay steps , as the Smith compensation amount of the reference current value at the next moment.

[0093] Specifically, the current control quantity at the current moment is , and then the current control amount Give Figure 5 The actuator in the fuel cell stack is used to control the input current of the fuel cell stack. Then, based on the Smith estimator and conduct , and put it into the queue, and then take out the value in the queue as the compensation amount for the next moment.

[0094] The following letters represent the variables at each moment:

[0095] At time k-1:

[0096] ;

[0097] ;

[0098] ;

[0099] ;

[0100] ;

[0101] Notice It is known at time k-1 (calculated from the control quantity at time k-2).

[0102] ;

[0103] ;

[0104] Then, the Smith predictor is updated (to prepare for the next time step k):

[0105] , use the control quantity at time k-1 to update the model state, Put it into the delay queue and take out the delayed value as (for time k) .

[0106] At time k:

[0107] ;

[0108] ;

[0109] ;

[0110] ;

[0111] ;

[0112] Notice It is known at time k (calculated from the control quantity at time k-1).

[0113] ;

[0114] ;

[0115] Then, the Smith estimator is updated (to prepare for the next time step k+1):

[0116] , use the control quantity at time k to update the model state, Put it into the delay queue and take out the delayed value as (for time k+1) .

[0117] In this way, at each moment k, the Smith compensation amount calculated using the current control amount at moment k-1 is Calculate the current control quantity at time k, and use the current control quantity at time k to calculate the current control quantity required at time k+1 .

[0118] Note: The implementation details of the delay queue are that the queue length is calculated each time Put it at the end of the queue and take a value from the head of the queue as compensation.

[0119] therefore, (The value at the head of the queue after the queue is updated at time k-1).

[0120] Therefore, the present invention adopts a dual-loop cascade control + three-dimensional feedforward compensation + delayed prediction compensation control method, combined with the natural VI characteristics of the fuel cell stack, to achieve dynamic maintenance of bus voltage and high-precision tracking of DCAC output power, thereby improving the system's response speed and accuracy to dynamic power requirements.

[0121] Optionally, Figure 7 This is the operation logic diagram of the power generation system in the control method of the fuel cell power generation system proposed in the embodiment of the present invention. Figure 7 As shown, before obtaining a first difference between the actual power value of the grid / load and the target power value and generating a reference current variation based on the first difference and the power controller, the method further includes:

[0122] Controls the auxiliary power input energy of the grid / load, and controls the bidirectional DCAC module to be in rectification mode, completing the input pre-charge and output pre-charge of the bidirectional DCAC module;

[0123] When the output pre-charge of the bidirectional DCAC module reaches a first preset voltage, performing input pre-charge and output pre-charge on the bidirectional DCDC module;

[0124] When the output pre-charge of the DCDC module reaches a second preset voltage, the fuel cell auxiliary system is controlled to operate, and the fuel cell stack is controlled to start operating;

[0125] When the average cell voltage of the fuel cell stack reaches a third preset voltage and the voltage difference between the output side of the fuel cell stack and the output side of the bidirectional DCAC module is within a threshold range, the bidirectional DCAC module is controlled to be in inverter mode.

[0126] That is to say, before the fuel cell stack outputs electric energy to the outside, the fuel cell power generation system operates as follows: (1) the grid or other load auxiliary power supply inputs electric energy (AC10kV / 380V), and the voltage of AC630V is established through the transformer; (2) the system starts, the controller sends a start-up instruction, sends a rectification mode instruction to the DCAC inverter, starts the inverter to enter the rectification mode, and completes the DCAC input pre-charging and output pre-charging respectively; (3) the system collects the voltage value of the DC side voltage sensor of the inverter, reaches the preset threshold voltage of 1500V (settable) (first preset voltage), pre-charges the DCDC, and the high voltage DC650V and low voltage D C24V (second preset voltage); (4) The fuel cell module starts, and the BOP starts working at the same time. The average cell voltage of the stack is greater than 0.8V (third preset voltage). The fuel cell stack starts to output power to the outside, and the voltage sensor detects the stack output voltage at the same time; (5) As the output power of the fuel cell stack is established and gradually increased, it replaces the DCAC inverter rectifier output. The current of the current sensor will gradually decrease. When it is detected that the current reaches 0A (voltage difference threshold range), it proves that the output of the fuel cell stack has completely replaced the inverter rectifier output. A rectifier mode switching inverter mode instruction is sent to the DCAC inverter, and the inverter enters the inverter working mode.

[0127] At this time, the fuel cell stack outputs electrical energy to the outside, and the power control method of steps S101 to S105 is executed to control the output of the fuel cell stack. By real-time monitoring of the system power demand and bus voltage, the power distribution control method is dynamically adjusted to ensure system stability and efficiency.

[0128] Optionally, continue to refer to Figure 3 and Figure 7 , the fuel cell power generation system also includes a transformer and a filter. The transformer is located between the bidirectional DCAC module and the grid / load, and the filter is located between the fuel cell stack and the bidirectional DCAC module;

[0129] The input power is AC10kV / 380V, and the transformer generates AC630V. The transformer and filter are used to stabilize the overall electrical signal transmission of the circuit.

[0130] Optionally, the fuel cell power generation system further includes a diode, the positive electrode of which is connected to the fuel cell stack, and the negative electrode of which is connected to the filter and the bidirectional DC-DC module, respectively. The diode is used to prevent the bidirectional DC-DC from charging the fuel cell stack and damaging it when the fuel cell power output is unstable.

[0131] Optionally, continue to refer to Figure 7 The fuel cell power generation system further includes a discharge module, and the control method further includes:

[0132] After the fuel cell stack is controlled to finish working, the stack is purged, and when the stack purge is completed, the fuel cell auxiliary system is controlled to be in a standby state;

[0133] The discharge module is controlled to discharge the voltage of the fuel cell stack, and when the voltage of the bidirectional DCDC module reaches a fourth preset voltage, the bidirectional DCAC module is controlled to shut down;

[0134] When the voltage of the fuel cell stack reaches a fifth preset voltage, the discharge module is controlled to stop discharging the voltage of the fuel cell stack.

[0135] That is, after the fuel cell stack outputs electrical energy, the fuel cell power generation system operates as follows: (6) After the work is completed, the controller issues a shutdown command, controls the fuel cell module to shut down, and performs stack purge. After the stack purge is completed, the fuel cell module BOP is on standby; (7) The fuel cell module begins to discharge. When the DC voltage of the voltage sensor drops to DC1200V (the fourth preset voltage), the controller sends a shutdown command to the DCAC inverter; (8) When the fuel cell stack discharges the residual electricity, a logical judgment is made based on the output voltage of the fuel cell stack collected by the voltage sensor. As the voltage at the output end of the fuel cell stack decreases, the discharge resistance is gradually reduced to meet the discharge of the fuel cell stack within a limited time. (9) When the residual electricity of the fuel cell stack is discharged to the set pressure holding value (the fifth preset voltage), the discharge circuit, i.e., the discharge module, is controlled to stop discharging, and the system enters the shutdown and pressure holding standby state.

[0136] Therefore, the electrical topology of the hydrogen fuel cell power generation system and the fuel cell power closed-loop control method with multi-dimensional dynamic compensation are suitable for scenarios such as distributed power generation systems with AC output and requiring high dynamic response power control. The system is an efficient, stable and simple hydrogen fuel cell power generation system. The present invention improves the overall performance of the system by optimizing the system architecture and control method, simplifies the architecture of the hydrogen fuel cell power generation system, improves the efficiency of the hydrogen fuel cell power generation system, and enhances the dynamic response capability.

[0137] According to another aspect of the present invention, a fuel cell power generation system is provided, referring to Figure 3, including: a bidirectional DCAC module, a bidirectional DCDC module, a fuel cell stack and a fuel cell auxiliary system, wherein the output end of the fuel cell stack is connected to a DC bus, and the DC bus is divided into a first branch and a second branch. The first branch is converted into grid / load power supply by the bidirectional DCAC module, and the second branch is converted into power supply for the fuel cell auxiliary system by the bidirectional DCDC module;

[0138] The power generation system further includes: at least one processor; and

[0139] a memory communicatively connected to at least one processor; wherein,

[0140] The memory stores a computer program that can be executed by at least one processor. The computer program is executed by the at least one processor so that the at least one processor can execute the control method of the fuel cell power generation system according to any embodiment of the present invention.

[0141] like Figure 3 As shown, the fuel cell power generation system of the present invention is mainly composed of key components such as PCS (filter, bidirectional DCAC, etc.), controller, fuel cell module, fuel cell module BOP, bidirectional DCDC, diode, etc. The DC power output by the fuel cell is directly input to the PCS through the diode. The DC bus output by the fuel cell is divided into two branches. The main branch is connected to the PCS for inversion and outputs AC power to the transformer to provide power energy for the load / grid. The branch is converted by DC / DC to power the fuel cell module BOP to provide the fuel cell module with hydrogen, air, water temperature, etc. necessary for the fuel cell reaction.

[0142] Figure 8 Schematic diagram of the structure of the control device for implementing the control method of the fuel cell power generation system according to the embodiment of the present invention. Figure 8 As shown, the system includes at least one processor 11 and memory, such as a read-only memory (ROM) 12 and a random access memory (RAM) 13, communicatively connected to the at least one processor 11. The memory stores computer programs executable by the at least one processor. The processor 11 can perform various appropriate actions and processes based on the computer program stored in the ROM 12 or loaded from the storage unit 18 into the RAM 13. The RAM 13 can also store various programs and data required for system operation. The processor 11, the ROM 12, and the RAM 13 are interconnected via a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0143] Many components in the system are connected to an input / output (I / O) interface 15, including an input unit 16, such as a keyboard, mouse, etc.; an output unit 17, such as various types of displays, speakers, etc.; a storage unit 18, such as a magnetic disk, optical disk, etc.; and a communication unit 19, such as a network card, modem, wireless communication transceiver, etc. The communication unit 19 allows the system to exchange information / data with other devices via a computer network such as the Internet and / or various telecommunication networks.

[0144] Processor 11 can be any general-purpose and / or specialized processing component with processing and computing capabilities. Some examples of processor 11 include, but are not limited to, a central processing unit (CPU), a graphics processing unit (GPU), various specialized artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, a digital signal processor (DSP), and any other suitable processor, controller, microcontroller, etc. Processor 11 executes the various methods and processes described above, such as the control method for the fuel cell power generation system.

[0145] In some embodiments, the control method of the fuel cell power generation system can be implemented as a computer program, which is tangibly contained in a computer-readable storage medium, such as the storage unit 18. In some embodiments, part or all of the computer program can be loaded and / or installed on the system via the read-only memory (ROM) 12 and / or the communication unit 19. When the computer program is loaded into the random access memory (RAM) 13 and executed by the processor 11, one or more steps of the control method of the fuel cell power generation system described above can be performed. Alternatively, in other embodiments, the processor 11 can be configured to execute the control method of the fuel cell power generation system in any other appropriate manner (for example, by means of firmware).

[0146] Various embodiments of the systems and techniques described above can be implemented in digital electronic circuit systems, integrated circuit systems, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), system-on-chip systems (SOCs), programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments can include being implemented in one or more computer programs that are executable and / or interpreted on a programmable system that includes at least one programmable processor, which can be a special purpose or general purpose programmable processor that can receive data and instructions from a storage system, at least one input device, and at least one output device, and transmit data and instructions to the storage system, the at least one input device, and the at least one output device.

[0147] The technical solution of an embodiment of the present invention is to control the current of the fuel cell stack in the following way on an architecture in which a branch is made on the bus between the output of the fuel cell stack and the DCAC (direct current-alternating current converter) to power the DCDC (direct current-direct current converter), namely, obtaining a first difference between the actual power value of the grid / load and the target power value, generating a reference current change based on the first difference and a power controller; obtaining a target current value of the fuel cell stack, and generating a reference current value based on the reference current change and the target current value; obtaining the actual current value output by the fuel cell stack; obtaining a current control value based on the reference current value, the actual current value and the current controller; and controlling the fuel cell stack based on the current control value, so as to achieve closed-loop control of the power of the fuel cell, simplify the architecture of the hydrogen fuel cell power generation system, improve the efficiency of the hydrogen fuel cell power generation system, and enhance the dynamic response capability.

[0148] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0149] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A control method for a fuel cell power generation system, characterized in that: The fuel cell power generation system comprises at least a bidirectional DCAC module, a bidirectional DCDC module, a fuel cell stack, and a fuel cell auxiliary system, wherein the output end of the fuel cell stack is connected to a DC bus, and the DC bus is divided into a first branch and a second branch. The first branch is converted by the bidirectional DCAC module into grid / load power supply, and the second branch is converted by the bidirectional DCDC module into power supply for the fuel cell auxiliary system; The control method includes: Obtaining a first difference between an actual power value of the grid / load and a target power value, and generating a reference current variation based on the first difference and a power controller; Acquiring a target current value of the fuel cell stack, and generating a reference current value based on the reference current variation and the target current value; Obtain the actual current value output by the fuel cell stack; Obtaining a current control value based on the reference current value, the actual current value, and a current controller; The fuel cell stack is controlled based on the current control value.

2. The control method of the fuel cell power generation system according to claim 1, characterized in that: Obtaining a target current value of the fuel cell stack includes: Acquiring an actual voltage value of the DC bus, and acquiring the power prediction value of the fuel cell auxiliary system based on a corresponding relationship between the actual voltage value and the power prediction value; Obtaining a conversion efficiency of the bidirectional DCAC module according to an interpolation efficiency table corresponding to the target power value and the actual voltage value; The target current value is calculated based on the power prediction value, the actual voltage value, the conversion efficiency of the bidirectional DCAC module, and the target power value.

3. The control method of the fuel cell power generation system according to claim 2, characterized in that: The reference current variation The following conditions are met: ; in, ; ; is the actual power value, is the target power value, is the first difference, is the reference current variation, are the proportional coefficient and integral coefficient of the power controller respectively, is the integral at the current moment; The target current value The following conditions are met: ;in, is the power prediction value, is the conversion efficiency of the bidirectional DCAC module, is the actual voltage value; The current control value The following conditions are met: ,in, , , are the proportional coefficient and differential coefficient of the current controller respectively, is the reference current value, is the actual current value, is the deviation of the current controller, is the number of iterations.

4. The control method of the fuel cell power generation system according to claim 3, characterized in that: After obtaining the current control value based on the reference current value, the actual current value and the current controller, the further step includes: calculating a compensation amount for the reference current value based on the current control value and a smith estimator; Generating a reference current value based on the reference current variation and the target current value includes generating the reference current value based on the reference current variation, the target current value, and the compensation amount.

5. The control method of the fuel cell power generation system according to claim 4, characterized in that: The reference current value after compensation The following conditions are met: , is the compensation amount; wherein, , , , , is the inertia time constant of the fuel cell stack, is the delay time of the fuel cell power generation system, is the compensation amount stored in each iteration of the Smith predictor, After updating the queue for each iteration, the queue at the head of the queue , is the number of delay steps, is the coefficient of the equation.

6. The control method of the fuel cell power generation system according to claim 1, characterized in that: Before obtaining a first difference between the actual power value of the grid / load and the target power value, and generating a reference current variation based on the first difference and a power controller, the method further includes: Controlling the auxiliary power supply input power of the grid / load, and controlling the bidirectional DCAC module to be in a rectification mode, to complete input pre-charging and output pre-charging of the bidirectional DCAC module; When the output pre-charge of the bidirectional DCAC module reaches a first preset voltage, performing input pre-charge and output pre-charge on the bidirectional DCDC module; When the output pre-charge of the DCDC module reaches a second preset voltage, controlling the fuel cell auxiliary system to operate and controlling the fuel cell stack to start operating; When the average cell voltage of the fuel cell stack reaches a third preset voltage and the voltage difference between the output side of the fuel cell stack and the output side of the bidirectional DCAC module is within a threshold range, the bidirectional DCAC module is controlled to be in an inverter mode.

7. The control method of the fuel cell power generation system according to claim 6, characterized in that: The fuel cell power generation system further includes a transformer and a filter, wherein the transformer is located between the bidirectional DCAC module and the grid / load, and the filter is located between the fuel cell stack and the bidirectional DCAC module; The input power is AC10KV / 380V, and the transformer establishes a voltage of AC630V.

8. The control method of the fuel cell power generation system according to claim 7, characterized in that: The fuel cell power generation system further includes a diode, wherein the positive electrode of the diode is connected to the fuel cell stack, and the negative electrode of the diode is connected to the filter and the bidirectional DCDC module respectively.

9. The control method of the fuel cell power generation system according to claim 6, characterized in that: The fuel cell power generation system further includes a discharge module, and the control method further includes: After controlling the fuel cell stack to finish working, the stack is purged, and after the stack purge is completed, the fuel cell auxiliary system is controlled to be in a standby state; controlling the discharge module to discharge the voltage of the fuel cell stack, and controlling the bidirectional DCAC module to shut down when the voltage of the bidirectional DCDC module reaches a fourth preset voltage; When the voltage of the fuel cell stack reaches a fifth preset voltage, the discharge module is controlled to stop discharging the voltage of the fuel cell stack.

10. A fuel cell power generation system, characterized in that: include: A bidirectional DCAC module, a bidirectional DCDC module, a fuel cell stack, and a fuel cell auxiliary system, wherein the output end of the fuel cell stack is connected to a DC bus, the DC bus is divided into a first branch and a second branch, the first branch is converted by the bidirectional DCAC module to power the grid / load, and the second branch is converted by the bidirectional DCDC module to power the fuel cell auxiliary system; Also included: at least one processor; and a memory communicatively connected to the at least one processor; wherein, The memory stores a computer program executable by the at least one processor. The computer program is executed by the at least one processor to enable the at least one processor to execute the control method of the fuel cell power generation system according to any one of claims 1 to 9.

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