Storage battery SOC estimation method of fuel cell and storage battery hybrid system

Abstract

The invention relates to a storage battery SOC (State of Charge) estimation method for a fuel cell and storage battery hybrid system, which comprises the following steps: in the working process of the fuel cell and storage battery hybrid system, carrying out SOC estimation based on an ampere-hour method, and correcting the SOC according to the time interval from the last correction to the current moment; and the SOC estimation result is corrected by selecting improved open-circuit voltage method correction control or full charge correction control, and on-line high-precision estimation of the SOC is realized under the condition that the normal power requirement of the fuel cell system is not influenced. Compared with the prior art, the method has the advantages that hardware does not need to be added or changed, normal power requirements are not affected, estimation efficiency is high, and estimation is accurate.

Description

Technical Field

[0001] The present invention relates to the field of power management of a fuel cell and battery hybrid system, and particularly to a method for estimating the state of charge (SOC) of a battery in a fuel cell and battery hybrid system. Background Art

[0002] Fuel cells are characterized by high efficiency and cleanliness. The fuel cell stack is the part where the electrochemical reaction of the fuel cell occurs. Hydrogen is introduced into the anode of the fuel cell stack, and air or oxygen is introduced into the cathode of the fuel cell stack. Under the action of a catalyst, hydrogen reacts with oxygen to generate electric energy. Since the output dynamic characteristics of the fuel cell stack are poor, the system usually includes a rechargeable battery as a buffer device to supplement the insufficient energy of the fuel cell or absorb the excess energy of the fuel cell. At the same time, the battery also provides power for the startup of the system. The structure of the fuel cell and battery hybrid system is as Figure 1 shown.

[0003] When performing power management, the state of charge (SOC) of the battery indicates the amount of remaining power of the battery at present. Usually, the battery management system (BMS) calculates the SOC of the battery. Accurately estimating the SOC is of great significance. When the estimation deviates, it may lead to system failures, and in severe cases, even cause equipment damage. For example, if the calculated SOC is higher than the actual value, the actual power may not be sufficient to meet the discharge requirements, or the restart after shutdown may fail due to insufficient power; conversely, if the calculated SOC is lower than the actual value, the buffering function may not be effectively achieved, or the feedback energy of the load may not be absorbed; in a more serious case, due to inaccurate SOC estimation, the battery may be overcharged or over-discharged, damaging the battery and even causing danger.

[0004] There are various methods for estimating the SOC of a battery, including the ampere-hour integration method, open-circuit voltage (OCV) method, impedance method, and intelligent algorithms. The ampere-hour method is the most commonly used method. The principle is that after knowing the initial state of charge of a battery, the remaining power of the battery is obtained by calculating the integral of the current and time added or subtracted. The ampere-hour method is relatively easy to implement and the calculation is simple, but there is a problem of cumulative error. The long-term error accumulation will cause the calculated value to deviate greatly from the actual value. Therefore, it needs to be calibrated through external conditions. A common method is to fully charge the battery so as to calibrate the SOC state at full charge to 100%. This is why battery manufacturers recommend that users perform full charges regularly. The principle of the open-circuit voltage method is to estimate the remaining power through the open-circuit voltage value. However, the implementation of the open-circuit voltage method usually has certain conditional limitations. Generally, it is necessary to stand still for a period of time under the condition of no charge and discharge current to obtain more accurate results.

[0005] However, in a fuel cell system, the storage battery used as a buffer device usually does not have an external charging interface and does not receive external power replenishment, so it does not meet the conditions for external full charge calibration. At the same time, during actual operation, both the load and the fuel cell output are constantly changing dynamically, and the charging and discharging states of the storage battery change with the changes of the two. Therefore, it also does not meet the conditions for calculating SOC using the conventional open circuit voltage method. Therefore, the two most commonly used methods, the ampere-hour method and the open circuit voltage method, are difficult to apply in a fuel cell system. Summary of the Invention

[0006] The object of the present invention is to provide a method for estimating the state of charge (SOC) of a storage battery in a fuel cell and storage battery hybrid system, manage the output power of the fuel cell, and based on the conventional ampere-hour method, combine the improved open circuit voltage method and the full charge method for SOC correction, so as to achieve online high-precision estimation of SOC without affecting the normal power demand of the fuel cell system.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] A method for estimating the state of charge (SOC) of a storage battery in a fuel cell and storage battery hybrid system, during the operation of the fuel cell and storage battery hybrid system, based on the ampere-hour method for SOC estimation, and according to the time interval from the last correction to the current moment, select the improved open circuit voltage method correction control or the full charge correction control to correct the SOC estimation result.

[0009] Further, the step of selecting the improved open circuit voltage method correction control or the full charge correction control to correct the SOC estimation result according to the time interval from the last correction to the current moment is specifically as follows:

[0010] When the time interval from the last correction to the current moment is greater than the second preset value, the improved open circuit voltage method correction control is adopted; if the time interval from the last correction to the current moment is greater than the first preset value and the improved open circuit voltage method correction control still fails to achieve correction, then the full charge correction control is adopted, where the second preset value is less than the first preset value.

[0011] Further, if the improved open circuit voltage method correction control or the full charge correction control is successfully implemented, the SOC correction value calculated by the improved open circuit voltage method correction control or the full charge correction control is directly used as the SOC estimation value.

[0012] Further, the method includes the following steps:

[0013] S000. When the fuel cell and storage battery hybrid system starts to work, initialize the first timer;

[0014] S100. Increase the value of the first timer;

[0015] S200. Determine whether the value of the first timer is greater than the first preset time value. If it is, execute step S400; otherwise, execute step S300.

[0016] S300. Determine whether the value of the first timer is greater than the second preset time value. If it is, execute step S500; otherwise, execute step S600.

[0017] S400. Execute full charge correction control. If the full charge correction control is successfully implemented, use the calculated SOC correction value as the SOC estimation value and reset the first timer; otherwise, execute step S600.

[0018] S500. Execute improved open - circuit voltage method correction control by controlling the power output of the fuel cell stack. If the improved open - circuit voltage method correction control is successfully implemented, use the calculated SOC correction value as the SOC estimation value and reset the first timer; otherwise, execute step S600.

[0019] S600. Estimate the SOC based on the ampere - hour method.

[0020] During the operation of the fuel cell and battery hybrid system, steps S100 - S600 are periodically executed to estimate the SOC in real - time.

[0021] Further, the full charge correction control includes the following steps:

[0022] S401. Determine whether the charging current at the current moment is less than the charging current upper limit and the fuel cell output is less than the output upper limit. If it is, increase the fuel cell output and go to step S403; otherwise, go to step S402.

[0023] S402. Determine whether the charging current at the current moment is greater than the charging current upper limit or the fuel cell output is greater than the output upper limit. If it is, decrease the fuel cell output and go to step S403; otherwise, directly go to step S403.

[0024] S403. Determine whether the battery has reached the full charge state. If it has, the full charge correction control is successfully implemented, and the SOC is corrected to 100%; otherwise, it indicates that the full charge correction is not successful or not completed, and go to step S600.

[0025] Further, determine whether the battery has reached the full charge state by whether the maximum single - cell voltage of the battery reaches the set value.

[0026] Further, the improved open-circuit voltage method correction control controls the power output of the fuel cell stack to satisfy the judgment condition that the fuel cell neither charges nor discharges. After satisfying the judgment condition, it judges whether the open-circuit voltage method calculation condition is satisfied according to the charging current accumulation value and the accumulation time. If the calculation condition is satisfied, the open-circuit voltage method is used to calculate the SOC correction value.

[0027] Further, the improved open-circuit voltage method correction control includes the following steps:

[0028] S501. Judge whether the charging current is greater than the charging current upper limit, or the fuel cell output is greater than the output upper limit, or the SOC calculated by the ampere-hour method is greater than the first SOC preset value. If so, reduce the fuel cell output and go to step S505; otherwise, go to step S502.

[0029] S502. Judge whether the SOC calculated by the ampere-hour method is less than the second SOC preset value. If so, increase the fuel cell output and go to step S505; otherwise, go to step S503.

[0030] S503. Judge whether the charging current is greater than zero. If so, reduce the fuel cell output and go to step S505; otherwise, go to step S504.

[0031] S504. Judge whether the charging current is less than zero. If so, increase the fuel cell output and go to step S505; otherwise, directly go to step S505.

[0032] S505. Judge whether the judgment condition that the fuel cell neither charges nor discharges is satisfied. If so, go to step S506; otherwise, reset the second timer and the charging current accumulation value, and go to step S600.

[0033] S506. Increase the value of the second timer and update the charging current accumulation value according to the current charging current.

[0034] S507. Judge whether the open-circuit voltage method calculation condition is satisfied according to the value of the second timer and the charging current accumulation value. If the calculation condition is satisfied, go to step S508; if the calculation condition is not satisfied, go to step S600.

[0035] S508. Calculate the SOC correction value by using the open-circuit voltage method with the current battery voltage and temperature, and reset the second timer and the charging current accumulation value.

[0036] S509. Judge whether the SOC correction value calculated in step S508 is within the set range. If so, it indicates that the improved open-circuit voltage method correction control is successfully implemented, and the SOC correction value is used as the SOC estimated value; otherwise, discard the SOC correction value and go to step S600.

[0037] Further, the judgment condition that the fuel cell neither charges nor discharges is: the SOC calculated by the ampere-hour method currently is within a preset acceptable range, and the current charging current is within a preset acceptable range.

[0038] Further, the calculation condition of the open-circuit voltage method is that the value of the second timer is greater than the third preset time value and the cumulative value of the charging current is less than a preset current value. When the condition that the cumulative value of the charging current is less than the preset current value is not met, the second timer and the cumulative value of the charging current are reset.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. No need to add or change hardware: Whether it is full charge correction or improved open-circuit voltage method correction, only through a series of software calculations and logical judgments, the output power of the fuel cell is adjusted and controlled to make the battery in a certain set state until the expected setting is reached, thus completing a complete correction operation, without modifying the hardware.

[0041] 2. Does not affect normal power demand: Starting from the index of the battery SOC, the present invention performs high-precision estimation through the ampere-hour method and the open-circuit voltage method, adjusts and controls the SOC of the battery to achieve efficient power control. The actual operation first controls the output of the fuel cell by controlling the power converter to make the battery SOC within the set range, and then performs the SOC correction of the open-circuit voltage. For special cases where the adjustment cannot be completed in a short time due to load changes, the full charge correction operation is transferred, and then the operation returns to the previous operation. This belongs to the internal adjustment of the fuel cell, power converter, and battery, and does not affect the normal power output.

[0042] 3. Achieves the optimization and balance between efficiency and accuracy of different SOC correction methods: The present invention first estimates the remaining power of the battery through the ampere-hour method, and after controlling the SOC within the set range, measures and calculates the SOC according to the modified open-circuit voltage method to obtain a relatively accurate estimated value, basically meeting the requirements for accuracy. The ampere-hour method has the advantages of simple method and small calculation amount, but the disadvantage is that it is difficult to obtain the accurate value of the initial SOC, and the integration process will accumulate large errors. The advantage of the open-circuit voltage method is that the initial value is relatively accurate, but it has high requirements for the measurement error of the terminal voltage. Therefore, by using the ampere-hour method and the open-circuit voltage method in combination, first estimating the real-time SOC value through the ampere-hour method, and then further estimating the SOC by using the open-circuit voltage method, a more accurate initial SOC value can be obtained, improving the overall efficiency. If in some cases, the open-circuit voltage method does not complete the correction within the set time period, the full charge correction method is enabled to ensure that a correction can be completed within a certain time. Description of the Drawings

[0043] Figure 1 Schematic diagram of the fuel cell and battery hybrid system

[0044] Figure 2 Method flowchart of the present invention

[0045] Figure 3 Full charge correction control flowchart of the present invention

[0046] Figure 4 Improved open circuit voltage method correction control flowchart of the present invention Specific embodiments

[0047] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0048] This embodiment is described with Figure 1 the fuel cell and battery hybrid system as shown. As Figure 1 , the fuel cell stack outputs through a power converter and is connected to the load, and the battery output is connected to the load. In the fuel cell system, the battery as a buffer device usually does not have the condition of external charging, and the battery changes with both the load and the fuel cell output, and is in a dynamic change process for a long time. The ampere-hour method is used as the basic method in the BMS for SOC estimation; at the same time, by controlling the power output of the fuel cell stack, the purpose of correcting the SOC of the battery using the improved open circuit voltage method is achieved; if the above improved open circuit voltage method fails to achieve correction within a certain time, full charge correction is performed, and the SOC is corrected to 100% in the full charge state. The above process is repeated periodically. On the basis of applying the conventional ampere-hour method, effective correction can be ensured, and the problem of excessive deviation in SOC calculation caused by long-term error accumulation can be avoided.

[0049] Specifically, as Figure 2 shown, this embodiment provides a method for estimating the SOC of a battery in a fuel cell and battery hybrid system, including the following steps:

[0050] S000. When the fuel cell and battery hybrid system starts to work, initialize the timer T. The timer T is used for timing, which represents the time interval from the last correction to the current moment;

[0051] S100. Increase the value of the timer T by the time dt of one program execution cycle;

[0052] S200. Determine whether the value of the timer T is greater than the preset value T1. If so, execute step S400; otherwise, execute step S300;

[0053] S300. Determine whether the value of timer T is greater than the preset value T2 (T2 < T1). If so, execute step S500; otherwise, execute step S600.

[0054] S400. Execute full charge calibration control. If the full charge calibration control is successfully implemented, use the calculated SOC calibration value as the SOC estimation value and reset timer T; otherwise, execute step S600.

[0055] S500. Execute improved open circuit voltage method calibration control by controlling the power output of the fuel cell stack. If the improved open circuit voltage method calibration control is successfully implemented, use the calculated SOC calibration value as the SOC estimation value and reset timer T; otherwise, execute step S600.

[0056] S600. Estimate SOC based on the ampere-hour method.

[0057] Among them, during the operation of the fuel cell and battery hybrid system, steps S100 - S600 are periodically executed to estimate SOC in real time.

[0058] The above process can be described as follows: Use timer T for timing. When the timing value of the timer exceeds the set value T2, start the control algorithm to implement improved OCV calibration. If the improved OCV calibration is successfully implemented, timer T is cleared; otherwise, continue timing until timer T exceeds the set value T1, indicating that it has been a long time since the SOC calibration was not completed. The control algorithm changes from improved OCV calibration to full charge calibration, and timer T is cleared when the full charge calibration is completed and starts timing again. Whether it is improved OCV calibration or full charge calibration, once it is successfully implemented, the current SOC estimation value is modified to the calibration value; during the process of no calibration or unsuccessful calibration, SOC is calculated by the ampere-hour method.

[0059] In step S300, timer T is compared with the set value T2. If it is not greater than T2, jump to the control without SOC calibration. In this control mode, the power control of the fuel cell is controlled according to other reasonable control methods. In this embodiment, the output power of the fuel cell can be controlled to maintain the SOC of the battery within a set range.

[0060] As Figure 3 shown, the full charge calibration control includes the following steps:

[0061] S401. Determine whether the charging current at the current moment is less than the charging current upper limit and the fuel cell output is less than the output upper limit. If so, increase the fuel cell output and go to step S403; otherwise, go to step S402.

[0062] S402. Determine whether the charging current at the current moment is greater than the upper limit of the charging current or the fuel cell output is greater than the upper limit of the output. If so, reduce the fuel cell output and proceed to step S403; otherwise, directly proceed to step S403.

[0063] S403. Determine whether the storage battery has reached the fully charged state. If so, the full charge correction control is successfully implemented, and the SOC is corrected to 100%; otherwise, it indicates that the full charge correction has not been successful or the correction is not completed, and proceed to step S600.

[0064] In steps S401 and S402, the charging current of the storage battery and the output power of the fuel cell are judged for their ranges. When the judgment result of S401 is true (that is, the charging current at the current moment is less than the upper limit of the charging current and the fuel cell output is less than the upper limit of the output), by controlling the BOP of the fuel cell, especially the output power converter, the output power of the fuel cell is increased; when the judgment result of S401 is false, jump to step S402 for further judgment. When the judgment result of S402 is true (that is, the charging current of the storage battery is greater than the upper limit value of the set charging current, or the output power of the fuel cell is greater than the upper limit value of the set output power), by controlling the BOP of the fuel cell, especially the output power converter, the output power of the fuel cell is reduced. When the judgment result of S402 is false, the output power of the fuel cell is not adjusted. After the adjustment of the fuel cell output power is completed, jump to step S403 to judge the charging state of the storage battery. If it is judged that the storage battery is fully charged, the SOC is corrected to 100%, and the timer T is cleared; otherwise, the full charge control process of this cycle ends.

[0065] In this embodiment, it is judged whether the storage battery has reached the fully charged state by whether the maximum single cell voltage of the storage battery reaches the set value.

[0066] Steps S401 to S403 are sub - processes in the overall process, so they are also repeatedly executed periodically along with the overall process. During the repeated execution process, the output of the fuel cell is dynamically adjusted to try to maintain the storage battery in the charging state until it is fully charged. It should be noted that there are many actual working conditions in the control process of step S400. In some cases, for example, when the output load power demand exceeds the maximum output power of the fuel cell, the storage battery will be in the discharge state, but according to the algorithm and system design, the storage battery can be fully charged and reach the fully charged state sooner or later.

[0067] As Figure 4 shown, the improved open - circuit voltage (OCV) method correction control includes the following steps:

[0068] S501. Judge the ranges of the charging current of the storage battery, the output power of the fuel cell, and the SOC value. Judge whether the charging current is greater than the upper limit of the charging current, or the fuel cell output is greater than the output upper limit, or the SOC calculated by the ampere-hour method is greater than the preset value SOC1. If the above conditions are judged to be true, that is, any one of the conditions that the charging current is greater than the upper limit of the charging current, the fuel cell output is greater than the output upper limit, and the SOC calculated by the ampere-hour method is greater than the preset value SOC1 is satisfied, then by controlling the BOP of the fuel cell, especially the output power converter, reduce the fuel cell output, and go to step S505. If the above conditions are judged to be false, go to step S502 for further judgment;

[0069] S502. Judge whether the SOC calculated by the ampere-hour method is less than the preset value SOC2. If so, by controlling the BOP of the fuel cell, especially the output power converter, increase the fuel cell output, and go to step S505. Otherwise, go to step S503 for further judgment;

[0070] S503. Judge whether the charging current is greater than zero. If so, by controlling the BOP of the fuel cell, especially the output power converter, reduce the fuel cell output, and go to step S505. Otherwise, go to step S504 for further judgment;

[0071] S504. Judge whether the charging current is less than zero. If so, by controlling the BOP of the fuel cell, especially the output power converter, increase the fuel cell output, and go to step S505. Otherwise, keep the output power of the fuel cell unchanged without adjustment and directly go to step S505;

[0072] S505. Judge whether the judgment condition that the fuel cell is neither charging nor discharging is satisfied, that is, whether the current SOC calculated by the ampere-hour method is within the preset acceptable range and the current charging current is within the preset acceptable range. If the condition is satisfied (that is, the SOC and the charging current are within the set ranges), then go to step S506. Otherwise, clear the timer t and the charging current accumulation value Ica, and end the improved OCV method correction control process of this cycle, and go to step S600;

[0073] S506. Increase the value of the timer t and update the charging current accumulation value Ica according to the current charging current;

[0074] S507. Determine whether the open-circuit voltage method calculation condition is satisfied based on the value of the timer t and the accumulated charging current value Ica (the value of the timer t is greater than the preset value t1 and the accumulated charging current value Ica is less than the preset current value Ica1). If the calculation condition is satisfied, proceed to step S508. If the condition that the value of the timer t is greater than the preset value t1 is not satisfied, directly end the improved OCV method correction control process for this cycle, proceed to step S600 to estimate the SOC using the ampere-hour method, and continue to increment the timer t in the next cycle. If the condition that the accumulated charging current value Ica is less than the preset current value Ica1 is not satisfied, clear the timer t and the accumulated charging current value Ica, and end the improved OCV method correction control process for this cycle, then proceed to step S600;

[0075] S508. Calculate the SOC correction value using the open-circuit voltage method based on the current battery voltage and temperature, and clear the timer t and the accumulated charging current value Ica;

[0076] S509. Determine whether the SOC correction value calculated in step S508 is within the set range. If so, it indicates that the improved open-circuit voltage method correction control has been successfully implemented. Take the SOC correction value as the SOC estimated value, clear the timer T, and end the improved OCV control process for this cycle. Otherwise, discard the SOC correction value, end the improved OCV control process for this cycle, and proceed to step S600.

[0077] Steps S501 - S509 are a sub-process in the overall process, and thus are also repeatedly executed periodically along with the overall process.

[0078] In step S600, the conventional ampere-hour method is used to calculate the SOC. The calculation principle of the conventional ampere-hour method is common knowledge: after knowing a certain state of charge SOC(t0) of the battery, by calculating the integral of the current i L (τ) and time, the remaining charge SOC(t) of the battery is obtained, which can be expressed by the formula as follows:

[0079] SOC(t) = SOC(t0) + (∫ t0 t η i i L (τ)dτ) / Q I

[0080] In this formula, Q c is the charge amount of the battery in a certain state, Q I is the rated charge amount, t0 is the initial moment, t is the termination moment, η i is the charge-discharge efficiency coefficient, i L (τ) is the charging current of the battery at the moment τ, and τ is the integration moment.

[0081] Step S600 integrates the charging current over a certain period by the ampere-hour method and accumulates it with the SOC of the previous period. Since the period length is extremely short, the charging current i L The integral over a period is approximately equal to the product of the time period dt and the charging current i L .

[0082] In this embodiment, the cycle period is set to 0.1 s, that is, the control flow shown is executed every 0.1 s, and the timer T is incremented once in each cycle period. Let T1 be 15 hours and T2 be 1 hour. Figure 2 During the operation of the fuel cell and battery hybrid system, first, the ampere-hour method is used for SOC estimation and timing starts, and the timer T is initialized to 0.

[0083] When the timer T increases to the T2 time, that is, when the count value of T is greater than 36000, the improved OCV method correction control is executed. Set the SOC to the median value 75% of the set range, the preset value SOC1 to 75.5%, and the preset value SOC2 to 74.5%. When SOC > SOC1, reduce the stack output; when SOC < SOC2, increase the stack output.

[0084] When SOC2 < SOC < SOC1, detect the current of the battery. If the charging current of the battery is greater than 0, control the fuel cell system to reduce the output power of the fuel cell to reduce the charging current of the battery; conversely, if the charging current of the battery is less than 0, that is, the battery is in the discharge state, control the fuel cell system to increase the output power of the fuel cell to reduce the discharge current of the battery.

[0085] The preset value SOC3 is 74%, the preset value SOC4 is 76%, the preset value Ic3 is -0.05C, and Ic4 is 0.05C. When it is satisfied that SOC is between SOC3 and SOC4 and the battery charging current is between Ic3 and Ic4, it is considered that the battery is basically in a stable non-charging and discharging state, the timer t starts timing, and the battery charging current is accumulated, and the accumulated result is recorded as Ica. Once the state that SOC is between SOC3 and SOC4 and the battery charging current is between Ic3 and Ic4 is not satisfied, the timer t starts timing again, and the accumulated result Ica of the battery charging current is cleared.

[0086]

[0087] ​When the state that the SOC is between SOC3 and SOC4 and the battery charging current is between Ic3 and Ic4 lasts for 1 hour, that is, after the timer t count value reaches 36000, the calculation of correcting the SOC by the improved open-circuit voltage method is performed to obtain the open-circuit voltage method SOC correction value. The obtained SOC correction value is compared with the SOC result calculated by the ampere-hour method in the previous cycle. If the difference is greater than the set value of 5%, it is considered that the calculated SOC correction value is not within the reasonable range, and the calculated SOC correction value is discarded, and the timer t and the cumulative result Ica of the battery charging current are cleared. According to the logic shown in the program flow, starting from the next cycle, a new round of improved open-circuit method correction will be restarted. If the difference between the obtained SOC correction value and the SOC result calculated by the ampere-hour method in the previous cycle is less than the set value of 5%, it is considered that the calculated SOC correction value is within the reasonable range, and the calculated SOC correction value is used as the new SOC value, and the timer T, the timer t, and the cumulative value Ica of the battery charging current are reset.

[0088] If the timer T increases to the T1 time, that is, the count value of T is greater than 540000, it means that the correction result has not been effectively corrected by the improved open-circuit voltage method correction control. If the timer T has not been cleared for 15 consecutive hours, the full charge correction control needs to be executed. Control the fuel cell system to increase the fuel cell output, and charge the battery through the active charging of the fuel cell or / and the feedback of the load until the battery reaches the full charge state. The condition for reaching the full charge state is set that the single cell voltage reaches the set value, such as 3.65V. When the full charge state is reached, the SOC is corrected to 100%, and the timer T, the timer t, and the cumulative value Ica of the battery charging current are reset.

[0089] The above timer T keeps running during the operation of the system, and the timing result is stored in the non-volatile storage medium. That is to say, when the controller of the system is powered off and then powered on again, it will not cause the timer T to start timing again.

[0090] The above has described in detail the preferred specific embodiments of the present invention. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field based on the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A method for estimating the state of charge (SOC) of a battery in a fuel cell and battery hybrid system, characterized in that, During the operation of the fuel cell and battery hybrid system, SOC estimation is performed based on the ampere-hour method, and according to the time interval from the last correction to the current moment, improved open circuit voltage method correction control or full charge correction control is selected to correct the SOC estimation result.

2. The battery SOC estimation method for a fuel cell and battery hybrid system according to claim 1, characterized in that The specific method of selecting improved open circuit voltage method correction control or full charge correction control to correct the SOC estimation result according to the time interval from the last correction to the current moment is as follows: When the time interval from the last correction to the current moment is greater than the second preset time value, improved open circuit voltage method correction control is adopted; if the time interval from the last correction to the current moment is greater than the first preset time value and the improved open circuit voltage method correction control still fails to achieve correction, full charge correction control is adopted, where the second preset time value is less than the first preset time value.

3. The method for estimating the SOC of a storage battery in a fuel cell and storage battery hybrid system according to claim 1, characterized in that, If the improved open circuit voltage method correction control or full charge correction control is successfully implemented, the SOC correction value calculated by the improved open circuit voltage method correction control or full charge correction control is directly used as the SOC estimation value.

4. The method for estimating the state of charge (SOC) of a battery in a fuel cell and battery hybrid system according to claim 1, characterized in that, The method includes the following steps: S000: When the fuel cell and battery hybrid system starts to work, initialize the first timer. S100: Increase the value of the first timer. S200: Determine whether the value of the first timer is greater than the first preset time value. If so, execute step S400; otherwise, execute step S300. S300: Determine whether the value of the first timer is greater than the second preset time value. If so, execute step S500; otherwise, execute step S600. S400: Execute full charge correction control. If the full charge correction control is successfully implemented, use the calculated SOC correction value as the SOC estimation value and reset the first timer; otherwise, execute step S600. S500: Execute improved open circuit voltage method correction control by controlling the power output of the fuel cell stack. If the improved open circuit voltage method correction control is successfully implemented, use the calculated SOC correction value as the SOC estimation value and reset the first timer; otherwise, execute step S600. S600: Perform SOC estimation based on the ampere-hour method. During the operation of the fuel cell and battery hybrid system, steps S100 to S600 are periodically executed to estimate SOC in real time.

5. The method for estimating the state of charge (SOC) of a battery in a fuel cell and battery hybrid system according to claim 1, wherein The full charge correction control includes the following steps: S401: Determine whether the charging current at the current moment is less than the charging current upper limit and the fuel cell output is less than the output upper limit. If so, increase the fuel cell output and go to step S403; otherwise, go to step S402. S402: Determine whether the charging current at the current moment is greater than the charging current upper limit or the fuel cell output is greater than the output upper limit. If so, decrease the fuel cell output and go to step S403; otherwise, directly go to step S403. S403: Determine whether the battery has reached the full charge state. If so, the full charge correction control is successfully implemented, and the SOC is corrected to 100%; otherwise, it indicates that the full charge correction is not successful or the correction is not completed, and go to step S600.

6. The method for estimating the state of charge (SOC) of a battery in a fuel cell and battery hybrid system according to claim 5, wherein, It is determined whether the battery has reached the full charge state by whether the maximum single cell voltage of the battery reaches the set value.

7. The method for estimating the SOC of the battery in a fuel cell and battery hybrid system according to claim 1, wherein, The improved open-circuit voltage method correction control controls the power output of the fuel cell stack to meet the judgment condition that the fuel cell neither charges nor discharges. After meeting the judgment condition, it judges whether the open-circuit voltage method calculation condition is met according to the charging current accumulation value and the accumulation time. If the calculation condition is met, the open-circuit voltage method is used to calculate the SOC correction value.

8. The method for estimating the SOC of a battery in a fuel cell and battery hybrid system according to claim 1, characterized in that, The improved open-circuit voltage method correction control includes the following steps: S501. Judge whether the charging current is greater than the charging current upper limit, or the fuel cell output is greater than the output upper limit, or the SOC calculated by the ampere-hour method is greater than the first SOC preset value. If so, reduce the fuel cell output and go to step S505; otherwise, go to step S502. S502. Judge whether the SOC calculated by the ampere-hour method is less than the second SOC preset value. If so, increase the fuel cell output and go to step S505; otherwise, go to step S503. S503. Judge whether the charging current is greater than zero. If so, reduce the fuel cell output and go to step S505; otherwise, go to step S504. S504. Judge whether the charging current is less than zero. If so, increase the fuel cell output and go to step S505; otherwise, directly go to step S505. S505. Judge whether the judgment condition that the fuel cell neither charges nor discharges is met. If so, go to step S506; otherwise, reset the second timer and the charging current accumulation value, and go to step S600. S506. Increase the value of the second timer and update the charging current accumulation value according to the current charging current. S507. Judge whether the open-circuit voltage method calculation condition is met according to the value of the second timer and the charging current accumulation value. If the calculation condition is met, go to step S508; if the calculation condition is not met, go to step S600. S508. Calculate the SOC correction value by using the open-circuit voltage method with the current battery voltage and temperature, and reset the second timer and the charging current accumulation value. S509. Judge whether the SOC correction value calculated in step S508 is within the set range. If so, it indicates that the improved open-circuit voltage method correction control is successfully implemented, and the SOC correction value is used as the SOC estimated value; otherwise, discard the SOC correction value and go to step S600.

9. The method for estimating the state of charge (SOC) of a battery in a fuel cell and battery hybrid system according to claim 7 or 8, characterized in that, The judgment condition that the fuel cell neither charges nor discharges is that the SOC calculated by the current ampere-hour method is within the preset acceptable range, and the current charging current is within the preset acceptable range.

10. The method for estimating the SOC of a battery in a fuel cell and battery hybrid system according to claim 8, wherein The open-circuit voltage method calculation condition is that the value of the second timer is greater than the third time preset value and the charging current accumulation value is less than the preset current value. When the condition that the charging current accumulation value is less than the preset current value is not met, reset the second timer and the charging current accumulation value.

Images