CN113884928B - A multi-stack distributed control method based on fuel cell health correction - Google Patents

Abstract

The invention discloses a multi-stack distributed control method based on fuel cell health degree correction, which comprises the steps of collecting voltage and current signals at the output end of a fuel cell, collecting voltage and current signals at the output end of a unidirectional converter, and collecting voltage and current signals at a demand side; evaluating the real-time operation performance of the fuel cell through the acquired output end voltage, current and power of the fuel cell, and quantifying the health degree of each fuel cell; calculating real-time self-setting factors related to the current performance state of each fuel cell by combining the circuit and current-carrying characteristics of a direct current power supply network according to the calculation result of the health degree of the fuel cells; and finally, completing the self-adaptive adjustment of the output power of the fuel cell through the rapid correction of the voltage outer ring and the current inner ring under the change of the real-time self-setting factor, and realizing the distributed control among the fuel cells of multiple stacks. The invention is beneficial to any galvanic pile access system or fault galvanic pile exit system, reduces communication fault, enhances system stability and is beneficial to system capacity expansion.

Description

A multi-stack distributed control method based on fuel cell health correction

technical field

The invention belongs to the technical field of fuel cells, and in particular relates to a power distribution management and control method of a fuel cell cluster.

Background technique

With the rapid development of science and technology in the world, the energy that pollutes the environment urgently needs to be replaced by new environmentally friendly energy sources. Energy saving and emission reduction have become the direction of continuous efforts of scientific research institutes in various countries. In many new energy applications, hydrogen energy is an efficient and safe energy source. , clean and sustainable new energy is regarded as the most promising clean energy and the development direction of human strategic energy in the 21st century, while the fuel cell is a device that converts hydrogen energy into electrical energy through electrochemical reaction. Restricted by the Carnot cycle, it has the advantages of high energy conversion efficiency, low operating temperature, fast startup speed, and low operating noise.

Although fuel cells have many advantages, they have shortcomings such as limited power level of a single power generation system and insufficient durability, which lead to the failure of fuel cells to be put into use on a large scale in the high-power energy market. Therefore, more and more researchers build a multi-stack fuel cell system to solve the above problems by coordinating multiple single fuel cells. However, most of the current multi-stack fuel cell systems are composed of single-stack fuel cells with the same power generation parameters, and no in-depth research has been carried out on the coordinated control method between multi-stacks. In addition, most of the existing control strategies are based on ideal conditions, treating the fuel cell as a static power generation system, assuming that the operating performance of the stack does not change, and does not consider the impact of changes in its operating performance. In practical applications, fuel cells are greatly affected by environmental factors such as temperature, pressure, and humidity. It is necessary to evaluate the operating status of the stacks in real time, and implement appropriate control methods in a timely and effective manner according to their respective health degrees to ensure that multiple stacks Normal and stable operation of the fuel cell system.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention proposes a multi-stack distributed control method based on fuel cell health correction. system performance. Considering that a certain stack in the multi-stack system may suddenly exit due to failure, and in order to achieve the plug-and-play function, a control method based on self-tuning factor adjustment is also adopted, and the adjustment is designed according to the real-time operating performance of each stack. The factor adaptively adjusts the setting coefficient to realize the distribution of the reference power.

In order to achieve the above object, the technical solution adopted in the present invention is: a multi-stack distributed control method based on fuel cell health correction, comprising the steps of:

S100, collect the voltage and current signals at the output end of the fuel cell, collect the voltage and current signals at the output end of the unidirectional DC/DC converter, and collect the voltage and current signals at the demand side;

S200, evaluating the real-time operation performance of the fuel cell by obtaining the output voltage, current and power of the fuel cell, and quantifying the health of each fuel cell;

S300, according to the calculation result of the health degree of the fuel cell, combined with the circuit and current carrying characteristics of the DC power supply network, calculate the real-time self-tuning factor related to the current performance state of each fuel cell;

S400, finally, under the real-time self-tuning factor change, the self-adaptive adjustment of the output power of the fuel cell is completed through the rapid correction of the voltage outer loop and the current inner loop, so as to realize distributed control among multiple stacks of fuel cells.

Further, the multi-stack fuel cell system includes a plurality of fuel cells that supply power to the busbar in a fully parallel manner, and all fuel cells are connected to the DC busbar through their respective unidirectional DC/DC converters to ensure that the output power fluctuates and the load side voltage is stable. Stability improves power supply quality.

Further, in the calculation of the health degree of the real-time operating performance of the fuel cell in the step S200, the rated voltage when the corresponding stack performance is optimal is calculated according to the real-time output current of the fuel cell, and according to the allowable current at the rated current. Maximum voltage drop calculation health.

Further, the calculation formula of the health degree of the real-time operating performance of the fuel cell in the step S200 is:

The health degree that takes into account the performance of the fuel cell is H _FC , and has the following formula:

In the formula, ΔV _rated represents the stack voltage drop when the stack outputs the rated current under the current performance, and is further represented as the difference between the rated voltage V _rated,init when the stack performance is the best and the rated voltage V _{rated,degraded} at the current performance state; ΔV _rated,max indicates the maximum allowable voltage drop at rated current, which is 10% of the rated voltage.

Further, the process of obtaining the rated voltage V _rated,init when the corresponding stack performance is optimal under the real-time output current of the fuel cell includes the steps:

Carry out test experiments on fuel cells with good performance, and obtain experimental data of current and voltage operating under different power levels;

Through the analysis of the experimental data of voltage and current, the relationship between the ideal output voltage and operating current of the fuel cell is reversed;

The _coefficients a ₀ , a ₁ , . The rated voltage V _rated,init when the stack performance is optimal.

Further, the coefficients of the ideal output voltage and operating current of the fuel cell are identified based on the complex nonlinear least squares algorithm, specifically:

For a fuel cell system: y=f(x, θ);

Among them, y is the ideal voltage value of the fuel cell; x is the measured current when the fuel cell is working; θ is the parameter vector to be identified:

and have:

In the formula, N is the number of frequency sampling points, wk is the residual weight, S is the residual weighted square sum of the measured value and the fitted value, Δ _l is the error precision, when θ(k+1) and θ(k) are infinite When approaching, Δ _l will be very small, and the identification result will tend to be stable.

Further, in the step S300, the output power of each fuel cell is calculated according to the calculation result of the health degree of the fuel cell, and the output power of each fuel cell is calculated according to the output power of the fuel cell combined with the circuit and current carrying characteristics of the DC power supply network. Real-time auto-tuning factor related to the current performance state.

Further, according to the calculation result of the health degree of the fuel cell, the output power of each fuel cell is calculated, including the steps:

Real-time estimation of the health ratio of each fuel cell in operation according to the measured voltage change;

The output power of each fuel cell in the multi-stack fuel cell system is calculated according to the health ratio.

Further, calculating a real-time self-tuning factor related to the current performance state of each fuel cell according to the output power of the fuel cell combined with the circuit and current-carrying characteristics of the DC power supply network, including the steps:

Considering that the self-tuning factor of the output terminal of the unidirectional DC/DC converter configured for each fuel cell is K _droop , for the DC power supply system with a parallel structure, the equation system can be constructed according to Kirchhoff's voltage and current laws;

The real-time value of the auto-tuning factor corresponding to the output power of each fuel cell can be calculated according to the constructed equations combined with the circuit and current-carrying characteristics of the DC power supply network.

Further, in the step S400, a corresponding self-tuning factor is added to the output power of the one-way DC/DC converter configured in each fuel cell, and the one-way DC/DC conversion can be controlled by changing the size of the self-tuning factor. The output power of the fuel cell is corresponding to the output of the fuel cell, and the self-adaptive adjustment of the output power of the fuel cell is completed through the rapid correction of the voltage outer loop and the current inner loop, so as to realize distributed control among multiple stacks of fuel cells.

The beneficial effects of adopting this technical solution:

The invention firstly relies on high-precision sensors to collect the voltage and current signals of the fuel cell input end and the output end of the unidirectional DC/DC converter, and the voltage and current of the load demand side respectively in real time and store them in the controller, and then according to the measured voltage, The current and power evaluate the real-time operating performance of fuel cells, and quantify the health of each fuel cell for the first time. Finally, combine the circuit and current carrying characteristics of the DC power supply network to calculate the real-time self-tuning factor related to the current health of each fuel cell. And through the voltage outer loop and the current inner loop to complete the self-adaptive adjustment of the output power of each fuel cell, so as to achieve distributed control among multiple stacks of fuel cells. The patent of the present invention is beneficial for any stack to be connected to the system or the faulty stack to be withdrawn from the system, reduces communication failures, enhances system stability, and is beneficial to system expansion.

The patent of the present invention adopts the real-time operation performance of each stack to adaptively adjust the output power of the stack, which improves the system operation performance. At the same time, a droop control method based on health setting is adopted. According to the real-time operating performance of each stack, an adjustment factor is designed to adaptively adjust the droop coefficient to realize the distribution of reference power, which reduces the possibility of system failure and improves the system fault tolerance. And power supply reliability, to achieve the plug and play function. The multi-stack fuel cell system adopts distributed control to ensure that each stack can adaptively adjust its output power according to its own performance and health relationship, which not only improves the consistency of the system but also improves the reliability of system power supply. performance and fault tolerance.

The invention proposes a calculation formula for real-time operation performance evaluation, quantifies the operation aging degree of the fuel cell, and provides a control basis for the power distribution of the multi-stack fuel cell system.

The invention adopts the complex nonlinear least squares algorithm to fit the relationship between the ideal voltage and the output current of the fuel cell in real time, determines the coupling coefficients a ₀ , a ₁ , . . . , an of the fuel _cell , and adopts the complex nonlinear least squares algorithm Compared with other methods, iterative solution not only uses less measurement data, but also can reduce the fitting error, and has strong engineering practicability.

The invention adopts the method of simplifying the quantitative relationship between the output power of the fuel cell and the added self-tuning factor by analyzing and simplifying the basic circuit of the parallel DC power supply system, directly coupling the performance of the fuel cell itself with the control variable, and reducing the number of stacks. The communication link of the system enhances the stability of the system and improves the scalability of the system expansion.

Description of drawings

1 is a schematic flowchart of a multi-stack distributed control method based on fuel cell health correction according to the present invention;

FIG. 2 is a schematic structural diagram of a multi-stack fuel cell system with setting factors in an embodiment of the present invention;

FIG. 3 is a schematic diagram of an equivalent simplified circuit of the output of a unidirectional DC/DC converter in a multi-stack fuel cell system according to an embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention is further described below with reference to the accompanying drawings.

In this embodiment, referring to FIG. 1 , the present invention proposes a multi-stack distributed control method based on fuel cell health correction, including the steps:

S100, collect the voltage and current signals at the output end of the fuel cell, collect the voltage and current signals at the output end of the unidirectional DC/DC converter, and collect the voltage and current signals at the demand side;

S200, evaluating the real-time operation performance of the fuel cell by obtaining the output voltage, current and power of the fuel cell, and quantifying the health of each fuel cell;

S300, according to the calculation result of the health degree of the fuel cell, combined with the circuit and current carrying characteristics of the DC power supply network, calculate the real-time self-tuning factor related to the current performance state of each fuel cell;

S400, finally, under the real-time self-tuning factor change, the self-adaptive adjustment of the output power of the fuel cell is completed through the rapid correction of the voltage outer loop and the current inner loop, so as to realize distributed control among multiple stacks of fuel cells.

The multi-stack fuel cell system includes multiple fuel cells that supply power to the busbar in a fully parallel manner, and all fuel cells are connected to the DC busbar through their respective unidirectional DC/DC converters to ensure the stability of the load-side voltage for output power fluctuations Improve power quality.

As an optimization scheme of the above embodiment, in the step S200, when calculating the health degree of the real-time operating performance of the fuel cell, the rated voltage corresponding to the optimal stack performance is calculated according to the real-time output current of the fuel cell, and the rated voltage is calculated according to the rated voltage of the fuel cell. The maximum allowable voltage drop when the current is used to calculate the health.

The formula for calculating the health degree of the real-time operating performance of the fuel cell is:

The health degree that takes into account the performance of the fuel cell is H _FC , and has the following formula:

In the formula, ΔV _rated represents the stack voltage drop when the stack outputs the rated current under the current performance, and is further represented as the difference between the rated voltage V _rated,init when the stack performance is the best and the rated voltage V _{rated,degraded} at the current performance state; ΔV _rated,max indicates the maximum allowable voltage drop at rated current, which is 10% of the rated voltage.

Further, the process of obtaining the rated voltage V _rated,init when the corresponding stack performance is optimal under the real-time output current of the fuel cell includes the steps:

Carry out test experiments on fuel cells with good performance, and obtain experimental data of current and voltage operating under different power levels;

Through the analysis of the experimental data of voltage and current, the relationship between the ideal output voltage and operating current of the fuel cell is reversed;

The _coefficients a ₀ , a ₁ , . The rated voltage V _rated,init when the stack performance is optimal.

Among them, the coefficients of the ideal output voltage and operating current of the fuel cell are identified by the complex nonlinear least squares algorithm, specifically:

For a fuel cell system: y=f(x, θ);

Among them, y is the ideal voltage value of the fuel cell; x is the measured current when the fuel cell is working; θ is the parameter vector to be identified:

and have:

In the formula, N is the number of frequency sampling points, wk is the residual weight, S is the residual weighted square sum of the measured value and the fitted value, Δ _l is the error precision, when θ(k+1) and θ(k) are infinite When approaching, Δ _l will be very small, and the identification result will tend to be stable.

As an optimization scheme of the above embodiment, in the step S300, the output power of each fuel cell is calculated according to the calculation result of the health degree of the fuel cell, and the output power of each fuel cell is calculated according to the output power of the fuel cell combined with the circuit and current carrying characteristics of the DC power supply network. A real-time auto-tuning factor related to the current performance state of each fuel cell.

Among them, calculating the output power of each fuel cell according to the calculation result of the health degree of the fuel cell includes the steps:

Real-time estimation of the health ratio of each fuel cell in operation based on the measured voltage change:

In the formula, L _ij represents the ratio of the output power fluctuation of the ith branch converter to the output power fluctuation of the jth branch converter;

Calculate the output power of each fuel cell in the multi-stack fuel cell system according to the health ratio:

In the formula, ΔP _dci represents the output power fluctuation of the ith branch converter, and P _dci (0) represents the initial output power of the ith branch converter.

Among them, as shown in Figure 2 and Figure 3, according to the output power of the fuel cell and combined with the circuit and current carrying characteristics of the DC power supply network, the real-time self-tuning factor related to the current performance state of each fuel cell is calculated, including the steps:

Taking into account the self-tuning factor of the output terminal of the unidirectional DC/DC converter configured for each fuel cell is K _droop , for the DC power supply system with a parallel structure, the equation system can be constructed according to Kirchhoff's voltage and current laws:

In the formula, I _dci , V _dci and R _li respectively represent the output current, voltage and line impedance of the i-th branch converter of the system, wherein the line impedance R _li is generally very small and can be ignored when necessary, R _load represents the load resistance, K _droopi Indicates the self-tuning factor added by the i-th branch, V _bus is the DC bus voltage;

According to the constructed equations combined with the circuit and current-carrying characteristics of the DC power supply network, the real-time value of the auto-tuning factor corresponding to the output power of each fuel cell can be calculated:

in,

As an optimization scheme of the above embodiment, in the step S400, a corresponding self-tuning factor is added to the output power of the unidirectional DC/DC converter configured in each fuel cell, and the unidirectional can be controlled by changing the size of the self-tuning factor. The DC/DC converter outputs the corresponding power, and completes the self-adaptive adjustment of the output power of the fuel cell through the rapid correction of the voltage outer loop and the current inner loop, and realizes distributed control among multiple stacks of fuel cells.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (7)

1. A multi-stack distributed control method based on fuel cell health correction, characterized in that it comprises the steps: S100, collect the voltage and current signals at the output end of the fuel cell, collect the voltage and current signals at the output end of the unidirectional DC/DC converter, and collect the voltage and current signals at the demand side; S200, evaluating the real-time operating performance of the fuel cell through the obtained fuel cell output terminal voltage, current and power, and quantifying the degree of health of each fuel cell; in the step S200, when calculating the degree of health of the real-time operating performance of the fuel cell, Calculate the rated voltage of the corresponding stack with the best performance according to the real-time output current of the fuel cell, and calculate the health degree according to the maximum allowable voltage drop at the rated current; The calculation formula of the health degree of the real-time operating performance of the fuel cell in the step S200 is: The health degree that takes into account the performance of the fuel cell is H _FC , and has the following formula:

In the formula, ΔV _rated represents the stack voltage drop when the stack outputs the rated current under the current performance, and is further represented as the difference between the rated voltage V _{rated_init} when the stack has the best performance and the rated voltage V _{rated_D} in the current performance state; ΔV _{rated_max} represents the rated current The maximum allowable voltage drop when the value is 10% of the rated voltage; S300, according to the calculation result of the health degree of the fuel cell, combined with the circuit and current carrying characteristics of the DC power supply network, calculate the real-time self-tuning factor related to the current performance state of each fuel cell; S400, finally, under the real-time self-tuning factor change, the self-adaptive adjustment of the output power of the fuel cell is completed through the rapid correction of the voltage outer loop and the current inner loop, so as to realize distributed control among multiple stacks of fuel cells; In the step S400, a corresponding self-tuning factor is added to the output power of the one-way DC/DC converter configured in each fuel cell, and the one-way DC/DC can be controlled by changing the size of the self-tuning factor through the constructed equation system The converter outputs the corresponding power, and completes the self-adaptive adjustment of the output power of the fuel cell through the rapid correction of the voltage outer loop and the current inner loop, and realizes distributed control among multiple stacks of fuel cells. 2. A multi-stack distributed control method based on fuel cell health correction according to claim 1, wherein the multi-stack fuel cell system comprises a plurality of fuel cells supplying power to the busbar in a fully parallel manner, all The fuel cells are connected to the DC bus through respective unidirectional DC/DC converters. 3 . The multi-stack distributed control method based on fuel cell health correction according to claim 1 , wherein, the rated voltage V _{rated_init} when the corresponding stack performance is optimal under the real-time output current of the fuel cell. 4 . The acquisition process includes steps: Carry out test experiments on fuel cells with good performance, and obtain experimental data of current and voltage operating under different power levels; Through the analysis of the experimental data of voltage and current, the relationship between the ideal output voltage and operating current of the fuel cell is reversed; The _coefficients a ₀ , a ₁ , . Rated voltage V _{rated_init} at which stack performance is optimal. 4 . The multi-stack distributed control method based on fuel cell health correction according to claim 3 , wherein the coefficients of the ideal output voltage and operating current of the fuel cell are identified based on a complex nonlinear least squares algorithm, 5 . Specifically: For a fuel cell system: y=f(x, θ); Among them, y is the ideal voltage value of the fuel cell; x is the measured current when the fuel cell is working; θ is the parameter vector to be identified:

and have:

In the formula, N is the number of frequency sampling points, wk is the residual weight, S is the residual weighted square sum of the measured value and the fitted value, Δ _l is the error precision, when θ(k+1) and θ(k) are infinite When approaching, Δ _l will be very small, and the identification result will tend to be stable. 5 . The multi-stack distributed control method based on fuel cell health degree correction according to claim 1 , wherein in the step S300 , each fuel cell is calculated according to the calculation result of the health degree of the fuel cells. 6 . Output power, according to the output power of the fuel cell and combined with the circuit and current-carrying characteristics of the DC power supply network, the real-time self-tuning factor related to the current performance state of each fuel cell is calculated. 6. A multi-stack distributed control method based on fuel cell health degree correction according to claim 5, characterized in that, calculating the output power of each fuel cell according to the calculation result of the health degree of the fuel cell, comprising the steps of: Real-time estimation of the health ratio of each fuel cell in operation according to the measured voltage change; The output power of each fuel cell in the multi-stack fuel cell system is calculated according to the health ratio. 7. A multi-stack distributed control method based on fuel cell health correction according to claim 5, characterized in that, according to the output power of the fuel cell combined with the circuit and current carrying characteristics of the DC power supply network, the Real-time self-tuning factor related to the current performance state of the battery, including steps: Considering that the self-tuning factor of the output terminal of the unidirectional DC/DC converter configured for each fuel cell is K _droop , for the DC power supply system with a parallel structure, the equation system can be constructed according to Kirchhoff's voltage and current laws; The real-time value of the auto-tuning factor corresponding to the output power of each fuel cell can be calculated according to the constructed circuit combined with the DC power supply network and the current-carrying characteristics.

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