A fuel storage method and system based on oilfield associated gas

Abstract

The application discloses a kind of based on oilfield associated gas's fuel storage method and system.The method includes: the original oilfield associated gas is pretreated;Pretreated associated gas is distributed to at least one of solid oxide fuel cell system and gas range extender by fuel distribution valve to generate electricity, and electric energy is output to common bus, and common bus is also connected with energy storage unit and adjustable load;Energy management system real-time acquisition load total power and each unit operating data, compare load total power with the rated power based on solid oxide fuel cell system and the maximum discharge power of energy storage unit to set up the hierarchical threshold to judge working condition interval, according to working condition interval and the state of charge of energy storage unit generation control instruction, dynamically adjust each unit operating state, so that system total output power and load total power match.The application realizes the flexible regulation and control of oilfield associated gas power generation system output power, and can quickly respond to load dynamic change.

Description

Technical Field

[0001] This application relates to the fields of new energy microgrids and distributed generation technology, and in particular to a combustion and storage method and system based on associated gas from oil fields. Background Technology

[0002] Associated gas in oil fields is a natural gas resource extracted from the formation along with crude oil during the oil extraction process. Its main component is methane, and it has high utilization value. Converting associated gas into electricity on-site to meet the power needs of oil field production is currently one of the important technological directions for the comprehensive utilization of associated gas in oil fields.

[0003] In existing technologies, the power generation of associated gas from oil fields mainly relies on a single type of power generation equipment. A common approach is to use gas turbine generator sets, such as internal combustion engines or small gas turbines, to directly combust the associated gas and drive the generator to supply power to electrical loads at the oilfield site, such as pumping units and water injection pumps. While these gas turbine generator sets are technologically mature, their power generation efficiency is typically only 30% to 40%, and their power regulation response is slow, usually on the order of minutes. Another approach is to use solid oxide fuel cell systems, which directly convert the chemical energy in associated gas into electrical energy through electrochemical reactions, achieving a power generation efficiency of 50% to 60%. However, due to the operating characteristics of the high-temperature ceramic fuel cell stack, the power change rate is typically limited to within 3% to 5% of the rated power per minute, and similarly, rapid power regulation cannot be achieved.

[0004] However, the electrical load at oilfield sites exhibits significant volatility and intermittency. Periodic start-ups and shutdowns of pumping units and intermittent switching of water injection pumps lead to frequent and substantial dynamic changes in the total load power. Neither of the individual power generation devices can quickly adapt to these dynamic load changes on a timescale of seconds. This results in insufficient or excessive power supply during sudden load changes, causing voltage and frequency fluctuations, affecting power quality and equipment safety, and leading to inefficient utilization of associated gas resources. Therefore, how to achieve flexible control of the output power of oilfield associated gas power generation systems to quickly respond to dynamic load changes is a pressing technical problem to be solved in the field of associated gas power generation utilization in oilfields. Summary of the Invention

[0005] This application aims to at least partially address one of the technical problems in the related art. Therefore, one objective of this application is to propose a combustion-storage method and system based on associated gas from oil fields.

[0006] One aspect of this application provides a combustion-storage method based on associated gas from an oil field, comprising the following steps: Step S1: The raw associated gas from the oilfield is pretreated by the associated gas pretreatment unit to output pretreated associated gas that meets the preset purity requirements. In step S2, the pretreated associated gas is distributed to at least one of the solid oxide fuel cell system and the gas range extender for power generation via a fuel distribution valve. The electrical energy generated by the solid oxide fuel cell system is output to the common bus via a first inverter, and the electrical energy generated by the gas range extender is output to the common bus via a second inverter. An energy storage unit and an adjustable load are also connected to the common bus, and the common bus supplies power to the oilfield's electrical load. Step S3: The total load power on the common bus, the output power of the solid oxide fuel cell system, the output power of the gas range extender, the state of charge of the energy storage unit, and the charging and discharging power of the energy storage unit are collected in real time through the energy management system. Step S4: The energy management system compares the total load power with a grading threshold set based on the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit to determine the current operating condition range. In step S5, the energy management system generates control commands based on the operating condition range determined in step S4 and the state of charge of the energy storage unit, and sends them to at least one of the fuel distribution valve, the solid oxide fuel cell system, the gas range extender, the energy storage unit, and the adjustable load, so as to dynamically adjust the operating status of each unit and match the total output power of the system with the total load power.

[0007] The present invention also provides a fuel storage system based on associated gas from oil fields, comprising: The associated gas pretreatment unit is used to dehydrate, desulfurize and filter the raw oilfield associated gas to output pretreated associated gas that meets the preset purity requirements. The associated gas pretreatment unit includes a molecular sieve dehydration device, an activated carbon desulfurization device and a filter arranged in series. The associated gas pretreatment unit is equipped with a heat source input terminal. A fuel distribution valve, the input end of which is connected to the output end of the associated gas pretreatment unit, the fuel distribution valve having a first output end and a second output end, is used to distribute the pretreated associated gas to downstream gas-consuming equipment as needed; A solid oxide fuel cell system, wherein the fuel input end of the solid oxide fuel cell system is connected to the first output end of the fuel distribution valve for generating electricity through an electrochemical reaction using the pretreated associated gas as fuel, and the power output end of the solid oxide fuel cell system is connected to a common bus through a first inverter; A gas range extender, wherein the fuel input end of the gas range extender is connected to the second output end of the fuel distribution valve, and is used to drive a generator to generate electricity using the pretreated associated gas as fuel; the power output end of the gas range extender is connected to the common bus via a second inverter. An energy storage unit is bidirectionally electrically connected to the common bus via a bidirectional converter. It is used to absorb and store excess electrical energy from the common bus when the total output power of the system is greater than the total load power, and to release electrical energy to the common bus when the total output power of the system is less than the total load power. An adjustable load, which is electrically connected to the common bus, is used to absorb the excess electrical energy on the common bus when the energy storage unit cannot fully absorb the excess electrical energy. The waste heat recovery unit has its input end connected to the exhaust gas outlet of the solid oxide fuel cell system and the exhaust gas outlet of the gas range extender, respectively, and its output end connected to the heat source input end of the associated gas pretreatment unit. It is used to recover the waste heat in the high-temperature exhaust gas generated by the solid oxide fuel cell system and the gas range extender and convert it into hot water and / or steam to be fed back to the associated gas pretreatment unit. An energy management system is communicatively connected to the fuel distribution valve, the solid oxide fuel cell system, the gas range extender, the energy storage unit, and the adjustable load, and is also communicatively connected to a load monitoring device installed on the common bus. This system is used to collect in real time the total load power, the output power of the solid oxide fuel cell system, the output power of the gas range extender, the state of charge of the energy storage unit, and the charging and discharging power of the energy storage unit. The system compares the total load power with a tiered threshold set based on the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit to determine the current operating condition range. Based on the operating condition range and the state of charge of the energy storage unit, the system generates control commands and sends them to each controlled unit to dynamically coordinate the operation of each unit so that the total system output power matches the total load power. Beneficial effects

[0008] This invention coordinates a solid oxide fuel cell system with a gas-fired range extender, and introduces an energy storage unit and adjustable load. The energy management system determines the operating range based on a comparison between the total load power and a tiered threshold, and then generates control commands to dynamically adjust the operating status of each unit in conjunction with the state of charge of the energy storage unit, ensuring that the total system output power matches the total load power. Specifically, the solid oxide fuel cell system, as the baseload power source, continuously and stably outputs electricity with high power generation efficiency; the gas-fired range extender, with its rapid start-stop and wide-range power regulation characteristics, acts as a peak-shaving power source, operating on demand; the energy storage unit, with its extremely short response time, provides instantaneous power buffering; and the adjustable load absorbs excess electricity when it cannot be fully absorbed by the energy storage unit. Through the tiered and coordinated control of the energy management system, these various units with different response characteristics and power regulation capabilities achieve flexible regulation of the output power of the associated gas power generation system in the oilfield. This enables rapid response and maintenance of power balance when the oilfield's electrical load changes dynamically, overcoming the technical shortcomings of existing technologies where single power generation equipment cannot match dynamic load changes due to slow power regulation response speed.

[0009] Furthermore, because solid oxide fuel cell systems directly convert the chemical energy in associated gas into electrical energy through electrochemical reactions, their power generation efficiency is higher than that of traditional gas generator sets. Using solid oxide fuel cell systems as the main power generation unit to handle baseload output is beneficial to improving the overall energy conversion efficiency of the system and the utilization level of associated gas. Simultaneously, the fuel distribution valve allocates pretreated associated gas to the corresponding power generation units as needed according to the control commands of the energy management system, avoiding inefficient consumption or waste of associated gas due to load mismatch, further improving the effective utilization rate of associated gas. Attached Figure Description

[0010] Figure 1 This application provides a combustion and storage method based on associated gas from an oilfield. Figure 2 This application relates to a fuel storage system based on associated gas from an oilfield. Detailed Implementation

[0011] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0012] It should be noted that when an element is referred to as "connected" or "coupled" to another element, it can be directly connected or coupled to another element, or there may be an intervening element. Furthermore, the terms "comprising," "including," or any other variations thereof as used herein are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Example 1

[0013] This embodiment provides a combustion and storage method based on associated gas from an oilfield, applied to a comprehensive utilization project of associated gas at an oilfield site. The oilfield is located in Northwest my country, producing approximately 5,000 standard cubic meters of original associated gas per day. The main component of the original associated gas is methane (approximately 85%-92% by volume), along with small amounts of ethane (approximately 3%-5% by volume), propane (approximately 1%-2% by volume), hydrogen sulfide (approximately 0.02%-0.1% by volume), water vapor, and mechanical impurities from the formation and pipelines. The oilfield's electrical load mainly includes pumping units (approximately 15-30 kW each, 4 units in total), water injection pumps (approximately 20 kW), gathering and transportation pumps (approximately 10 kW), lighting systems (approximately 5 kW), control systems, and domestic electricity (approximately 5-10 kW). The total daily load power fluctuates between 30 kW and 150 kW, exhibiting significant intermittent and fluctuating characteristics.

[0014] The fuel-storage method in this embodiment is achieved through the coordinated operation of an associated gas pretreatment unit, a fuel distribution valve, a solid oxide fuel cell system, a gas range extender, a first inverter, a second inverter, a common bus, an energy storage unit, an adjustable load, a waste heat recovery unit, and an energy management system. The following section provides a detailed description of the selection and key technical parameters of each major component.

[0015] Regarding the associated gas pretreatment unit: In this embodiment, the associated gas pretreatment unit is used to dehydrate, desulfurize, and filter the raw oilfield associated gas to produce pretreated associated gas that meets preset purity requirements. The dehydration process within the associated gas pretreatment unit uses 4A molecular sieves as the adsorbent and removes water vapor through pressure swing adsorption (PSA), configured in a dual-tower alternating operation mode. The desulfurization process uses impregnated activated carbon as the adsorbent and is designed in a dual-tank alternating operation mode. The filtration process uses sintered stainless steel filter elements. The associated gas pretreatment unit is equipped with a heat source input terminal to receive externally input hot water and / or steam as a heating source. In this embodiment, the preset desulfurization threshold is 0.1 ppm, and the preset filtration accuracy threshold is 5 micrometers.

[0016] Regarding the solid oxide fuel cell system: In this embodiment, the solid oxide fuel cell system uses a tubular solid oxide fuel cell stack as the core power generation component. The rated power of the solid oxide fuel cell system is 100kW, the minimum stable output power is 70kW (i.e., 70% of the rated power of the solid oxide fuel cell system), the power generation efficiency is 50%-55% (based on the lower calorific value of the fuel), and the operating temperature range is 700℃-800℃. The response time of the solid oxide fuel cell system from the minimum stable output power to the rated power is approximately 3 to 5 minutes. The solid oxide fuel cell system comprises four main functional units: a fuel processing module, a solid oxide fuel cell stack, an oxidant supply module, and a thermal management module. The fuel processing module performs steam reforming on the input pretreated associated gas, converting methane into reformed gas rich in hydrogen and carbon monoxide. The solid oxide fuel cell stack uses yttrium-stabilized zirconium oxide as the electrolyte material, converting the chemical energy in the fuel into direct current (DC) electricity through an electrochemical reaction. The oxidant supply module supplies preheated air as the oxidant to the cathode side of the solid oxide fuel cell stack. The thermal management module maintains the solid oxide fuel cell stack within a preset operating temperature range (700℃-800℃) by regulating the airflow to control the temperature distribution within the stack. The power output of the solid oxide fuel cell system is connected to a first inverter, which converts the DC power generated by the system into 380V / 50Hz three-phase AC power before outputting it to the common bus. The fuel input of the solid oxide fuel cell system is connected to the first output of the fuel distribution valve.

[0017] Regarding the gas range extender: In this embodiment, the gas range extender uses a small gas internal combustion engine generator set with a rated power of 50kW. The minimum stable output power of the gas range extender is 5kW (i.e., 10% of the rated power), and the power regulation range is 10% to 100% of the rated power. The gas range extender uses pretreated associated gas as fuel, with a cold start time of no more than 30 seconds and a power regulation response time of no more than 5 seconds, possessing rapid start-stop and wide-range power regulation capabilities. The power output terminal of the gas range extender is connected to a second inverter, which converts the electrical energy generated by the gas range extender into 380V / 50Hz three-phase AC power matched to the common bus before outputting it to the common bus. The fuel input terminal of the gas range extender is connected to the second output terminal of the fuel distribution valve.

[0018] Regarding the energy storage unit: In this embodiment, the energy storage unit uses a lithium iron phosphate battery pack with a rated capacity of 20kWh. The maximum charging power of the energy storage unit is 20kW, the maximum discharging power of the energy storage unit is 20kW, and the discharge response time does not exceed 100 milliseconds. The energy storage unit is bidirectionally connected to the common bus via a bidirectional converter. In this embodiment, a positive charge / discharge power indicates that the energy storage unit is discharging to the common bus, and a negative power indicates that the energy storage unit is charging from the common bus. In this embodiment, the threshold values ​​for each state of charge (SOC) are set as follows: the upper limit threshold for SOC is 90%, and when the SOC of the energy storage unit reaches this upper limit threshold, the energy storage unit will no longer accept charging; the lower limit threshold for SOC is 20%, and when the SOC of the energy storage unit is lower than this lower limit threshold, the energy storage unit will, in principle, no longer continuously discharge; the recovery threshold for SOC is 40%, which is higher than the lower limit threshold for SOC, and is used to determine when the gas range extender is allowed to stop and switch back to the energy storage unit discharge mode after it starts due to insufficient energy in the energy storage unit, forming a hysteresis control interval to prevent the system from frequently starting and stopping near the lower limit threshold for SOC; the short-time discharge protection threshold is 15%, which is lower than the lower limit threshold for SOC, and is used to determine whether the energy storage unit is allowed to provide short-time discharge support during the transition phase of the gas range extender startup.

[0019] Regarding the adjustable load: In this embodiment, the adjustable load is an electric heating device. The adjustable load is electrically connected to the common bus, and its power can be continuously adjusted within the range of 0 to 50kW. The function of the adjustable load is to absorb the excess electrical energy on the common bus when the energy storage unit cannot fully absorb the excess electrical energy.

[0020] Regarding the fuel distribution valve: In this embodiment, the fuel distribution valve is an electrically operated proportional control valve. The input end of the fuel distribution valve is connected to the output end of the associated gas pretreatment unit. The fuel distribution valve has a first output end and a second output end. The first output end of the fuel distribution valve is connected to the fuel input end of the solid oxide fuel cell system, and the second output end of the fuel distribution valve is connected to the fuel input end of the gas range extender.

[0021] Regarding the energy management system: In this embodiment, the energy management system adopts a control architecture based on a programmable logic controller (PLC), with a data sampling period of 100 milliseconds. The energy management system is communicatively connected to the fuel distribution valve, solid oxide fuel cell system, gas range extender, energy storage unit, and adjustable load, and is also communicatively connected to the load monitoring devices (including current transformers, voltage transformers, and power transmitters) located on the common bus. The control algorithms of the energy management system include a fuzzy PID control algorithm for real-time fast power regulation and a model predictive control algorithm for optimizing and predicting the operating state over a long time window.

[0022] Regarding the waste heat recovery unit: In this embodiment, the core equipment of the waste heat recovery unit is a flue gas-water heat exchanger, which adopts a finned tube structure. The input end of the waste heat recovery unit is connected to the exhaust gas outlet of the solid oxide fuel cell system and the exhaust gas outlet of the gas range extender, respectively. The output end of the waste heat recovery unit is connected to the heat source input end of the associated gas pretreatment unit through an insulated pipeline.

[0023] Based on the above system configuration, see Figure 1 The combustion and storage method based on associated gas from oil fields described in this embodiment includes the following steps: Step S1: The raw associated gas from the oilfield is pretreated by the associated gas pretreatment unit to output pretreated associated gas that meets the preset purity requirements.

[0024] Specifically, in this embodiment, the pretreatment in step S1 includes: sequentially subjecting the raw associated gas from the oilfield to dehydration, desulfurization, and filtration. Dehydration treatment removes moisture from the associated gas from the original oilfield. In this embodiment, 4A molecular sieves are used as the adsorbent, and pressure swing adsorption (PSA) is employed to deeply remove water vapor from the associated gas. The dehydration treatment is configured in a dual-tower alternating operation mode, where one tower performs adsorption and dehydration while the other tower uses hot water and / or steam from the waste heat recovery unit as a heat source for regeneration and recovery, thus achieving continuous and uninterrupted treatment. After dehydration treatment, the dew point temperature of the original associated gas from the oilfield is reduced to below -40°C, and the water content is reduced to trace levels. The presence of moisture can lead to pipeline corrosion and freezing in winter. More importantly, moisture can adversely affect the catalyst in the fuel processing module of the solid oxide fuel cell system, reducing catalyst activity or even causing catalyst poisoning and deactivation. Therefore, dehydration treatment is an indispensable first step in the pretreatment process.

[0025] Desulfurization removes hydrogen sulfide from the dehydrated gas, ensuring that the hydrogen sulfide content does not exceed a preset desulfurization threshold. In this embodiment, the preset desulfurization threshold is 0.1 ppm. The desulfurization process uses impregnated activated carbon as the adsorbent, a composite solution of sodium hydroxide and potassium iodide. Hydrogen sulfide is efficiently removed through the synergistic effect of chemical and physical adsorption. Hydrogen sulfide is a highly toxic impurity gas to the anode catalyst in solid oxide fuel cell systems. Even extremely low concentrations of hydrogen sulfide can cause irreversible catalyst deactivation, severely impacting the power generation efficiency and lifespan of the solid oxide fuel cell system. Furthermore, hydrogen sulfide corrodes the internal combustion engine components of the gas range extender. Therefore, desulfurization is a crucial step in the pretreatment process.

[0026] Filtration removes mechanical impurities from the desulfurized gas, ensuring that the particle size of the treated particulate matter does not exceed a preset filtration accuracy threshold. In this embodiment, the preset filtration accuracy threshold is 5 micrometers, and a sintered stainless steel filter element is used for filtration. Associated gas from raw oil fields may carry tiny solid particles from formations or pipelines. These mechanical impurities, when entering a solid oxide fuel cell system or gas range extender, can clog fuel nozzles, wear moving parts, and contaminate the catalyst surface.

[0027] The dehydration, desulfurization and filtration processes are performed sequentially. The output gas of the previous process is used as the input gas for the next process, and the output gas of the filtration process is the pretreated associated gas.

[0028] After the above three-stage pretreatment, the final quality indicators of the pretreated associated gas output are: methane content not less than 85% (volume fraction), dew point temperature not higher than -40℃, hydrogen sulfide content not exceeding 0.1ppm, and particulate matter particle size not exceeding 5 micrometers. The pretreated associated gas enters the input end of the fuel distribution valve through the outlet pipeline, awaiting subsequent steps for distribution according to load requirements.

[0029] Step S2: The pretreated associated gas is distributed to at least one of the solid oxide fuel cell system and the gas range extender via a fuel distribution valve for power generation. The electricity generated by the solid oxide fuel cell system is output to the common bus via a first inverter, and the electricity generated by the gas range extender is output to the common bus via a second inverter. An energy storage unit and an adjustable load are also connected to the common bus, which supplies power to the oilfield's electrical loads.

[0030] Specifically, during normal operation of this embodiment, the power generation and power output processes of each unit in step S2 are as follows: The power generation process of a solid oxide fuel cell system: The energy management system sends control commands to the fuel distribution valve based on the current operating conditions. The first output of the fuel distribution valve delivers pretreated associated gas to the fuel input of the solid oxide fuel cell system. After entering the solid oxide fuel cell system, the pretreated associated gas is first converted into reformed gas rich in hydrogen and carbon monoxide through a steam reforming reaction in the fuel processing module. The reformed gas is then delivered to the anode side of the solid oxide fuel cell stack, while the oxidant supply module supplies preheated air to the cathode side. In the solid oxide fuel cell stack, oxygen on the cathode side is conducted to the anode side in the form of oxygen ions through the solid oxide electrolyte, where it undergoes an electrochemical oxidation reaction with the hydrogen and carbon monoxide on the anode side to generate water vapor and carbon dioxide, while simultaneously generating direct current in the external circuit. The thermal management module maintains the solid oxide fuel cell stack within a preset operating temperature range. The electrical energy generated by the solid oxide fuel cell system is converted into 380V / 50Hz three-phase AC power by the first inverter and then output to the common bus.

[0031] The power generation process of the gas range extender: When the energy management system determines that the gas range extender needs to be activated, it sends a regulation command to the fuel distribution valve. The second output of the fuel distribution valve delivers pretreated associated gas to the fuel input of the gas range extender. The pretreated associated gas enters the internal combustion engine cylinder of the gas range extender and mixes with air for combustion, driving the generator to convert mechanical energy into alternating current electrical energy. The electrical energy generated by the gas range extender is output to the common bus via the second inverter.

[0032] The working process of the energy storage unit: The energy storage unit is bidirectionally electrically connected to the common bus via a bidirectional converter. When the total output power of the system on the common bus is greater than the total load power, the energy storage unit absorbs and stores excess electrical energy from the common bus; when the total output power of the system is less than the total load power, the energy storage unit releases electrical energy to the common bus to make up for the power gap.

[0033] The operation of adjustable load: The adjustable load is electrically connected to the common bus. When the energy storage unit cannot fully absorb excess energy (for example, the state of charge of the energy storage unit has reached the upper limit threshold of the state of charge or the excess power exceeds the maximum charging power of the energy storage unit), the energy management system controls the adjustable load to absorb the remaining energy on the common bus to prevent overvoltage or frequency abnormalities in the system.

[0034] In the power generation process of step S2, a waste heat recovery step is also performed in parallel, which specifically includes: The system collects high-temperature exhaust gases generated during power generation by the solid oxide fuel cell system and / or the gas range extender, and inputs the collected high-temperature exhaust gases into the waste heat recovery unit. Specifically, the high-temperature exhaust gases generated by the solid oxide fuel cell system during power generation have a temperature of approximately 250°C to 350°C, and the high-temperature exhaust gases generated by the gas range extender during power generation have a temperature of approximately 400°C to 550°C. Both high-temperature exhaust gases are connected to the input end of the waste heat recovery unit through high-temperature resistant stainless steel pipelines. When the solid oxide fuel cell system and the gas range extender are operating simultaneously, both high-temperature exhaust gases are input into the waste heat recovery unit simultaneously; when only the solid oxide fuel cell system is operating and the gas range extender is shut down, only the high-temperature exhaust gases generated by the solid oxide fuel cell system during power generation are input into the waste heat recovery unit.

[0035] The waste heat recovery unit converts the heat energy in the high-temperature exhaust gas into hot water and / or steam for output. The high-temperature exhaust gas flows on the flue gas side of the flue gas-water heat exchanger, while the circulating water flows on the tube side, and the two exchange heat through the finned tube walls. After heat exchange, the temperature of the high-temperature exhaust gas is reduced to approximately 80°C to 120°C before being discharged into the atmosphere, while the circulating water is heated to hot water and / or low-pressure steam at 80°C to 95°C.

[0036] The hot water and / or steam output from the waste heat recovery unit are fed back to the associated gas pretreatment unit as a heat source for the pretreatment process in step S1. Specific applications include: providing a heat source for the thermal regeneration of the adsorbent in the dehydration process; providing heat tracing and insulation for the pipelines and equipment of the associated gas pretreatment unit in low-temperature winter environments; and supplying excess heat to external sources if there are other heat demands at the oilfield site. Through the above waste heat recovery steps, a closed-loop cascade utilization of waste heat from power generation exhaust gas is achieved, increasing the overall energy utilization efficiency of the system to over 70%.

[0037] Step S3: Collect in real time the total load power on the common bus, the output power of the solid oxide fuel cell system, the output power of the gas range extender, the state of charge of the energy storage unit, and the charging and discharging power of the energy storage unit through the energy management system.

[0038] Specifically, the data acquisition process of the energy management system in this embodiment is as follows: Regarding the acquisition of total load power: The energy management system acquires the total load power on the common bus in real time through load monitoring devices installed on the common bus. Current transformers and voltage transformers in the load monitoring devices acquire current and voltage signals respectively, and the power transmitter converts these signals into power signals and uploads them to the energy management system. The sampling period is 100 milliseconds.

[0039] Regarding the acquisition of the output power of the solid oxide fuel cell system: The energy management system interacts with the internal controller of the solid oxide fuel cell system via the Modbus TCP communication protocol to read the active power at the output of the first inverter in real time, i.e., the output power of the solid oxide fuel cell system. Simultaneously, it reads auxiliary operating parameters such as the operating temperature of the solid oxide fuel cell stack, fuel flow rate, and stack voltage and current.

[0040] Regarding the acquisition of the gas range extender's output power: The energy management system interacts with the gas range extender's control module via a communication bus, reading the active power at the output of the second inverter in real time, which is the gas range extender's output power. It also reads the gas range extender's operating parameters such as speed and exhaust temperature. When the gas range extender is in a stopped state, its output power is zero.

[0041] Regarding the acquisition of the state of charge (SOC) and charge / discharge power of the energy storage unit: The energy management system interacts with the battery management system of the energy storage unit through the communication bus to read the SOC of the lithium iron phosphate battery pack in real time (expressed as a percentage, ranging from 0% to 100%), i.e., the SOC of the energy storage unit, and the current charge / discharge power, i.e., the charge / discharge power of the energy storage unit.

[0042] The energy management system stores the total load power, output power of the solid oxide fuel cell system, output power of the gas range extender, state of charge of the energy storage unit, and charging and discharging power of the energy storage unit in the internal data buffer in real time, and updates the data with a control cycle of 100 milliseconds, providing a real-time data basis for subsequent steps S4 and S5.

[0043] Step S4: The energy management system compares the total load power with the grading thresholds set for the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit to determine the current operating condition range.

[0044] Specifically, the grading thresholds set in this embodiment include a first grading threshold and a second grading threshold: the first grading threshold is equal to the rated power of the solid oxide fuel cell system, which is 100kW in this embodiment; the second grading threshold is equal to the sum of the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit, which is 100kW + 20kW = 120kW in this embodiment. The energy management system compares the total load power with the above two grading thresholds to determine whether the current operating condition range is one of the following three: First operating condition: The total load power is not greater than the rated power of the solid oxide fuel cell system, that is, the total load power is not greater than 100kW.

[0045] Second operating condition: The total load power is greater than the rated power of the solid oxide fuel cell system and not greater than the sum of the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit, that is, the total load power is greater than 100kW and not greater than 120kW.

[0046] Third operating condition: The total load power is greater than the sum of the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit, that is, the total load power is greater than 120kW.

[0047] Step S4 also includes the step of calculating the power difference according to the following formula: Power difference = Total load power - (Output power of solid oxide fuel cell system + Output power of gas range extender + Charging and discharging power of energy storage unit).

[0048] The total load power is the current actual total load power on the common bus collected in step S3; the output power of the solid oxide fuel cell system is the current actual active power of the solid oxide fuel cell system output to the common bus via the first inverter collected in step S3; the output power of the gas range extender is the current actual active power of the gas range extender output to the common bus via the second inverter collected in step S3 (zero when the gas range extender is in a shutdown state); the charging and discharging power of the energy storage unit is the current actual power exchanged between the energy storage unit and the common bus via the bidirectional converter collected in step S3 (discharging is positive, charging is negative). The power difference reflects the real-time deviation between the current system supply and demand: when the power difference is greater than zero, it indicates that the current system supply is insufficient; when the power difference is less than zero, it indicates that the current system supply is excessive; when the power difference is approximately zero (within the ±1kW allowable deviation range), it indicates that the system is in a power balance state.

[0049] In step S5, the energy management system uses the goal of bringing the power difference close to zero to perform closed-loop power regulation on each unit. Specifically, the energy management system calculates the current power difference within each control cycle (100 milliseconds): if the power difference is greater than +1kW, the energy management system fine-tunes by increasing the discharge power of the energy storage unit or increasing the output power of the gas range extender; if the power difference is less than -1kW, the energy management system fine-tunes by increasing the charging power of the energy storage unit or decreasing the output power of the solid oxide fuel cell system. A fuzzy PID control algorithm is used to achieve rapid dynamic response, while a model predictive control algorithm is used for optimization prediction over a longer time window, balancing the system's rapid responsiveness and operational stability.

[0050] Step S5: Based on the operating condition range determined in step S4 and the state of charge of the energy storage unit, the energy management system generates control commands and sends them to at least one of the fuel distribution valve, solid oxide fuel cell system, gas range extender, energy storage unit, and adjustable load to dynamically adjust the operating status of each unit so that the total output power of the system matches the total load power.

[0051] The specific control strategies for the three operating conditions are explained in detail below.

[0052] I. Control Strategy for the First Operating Condition In step S5, when the operating condition range determined in step S4 is the first operating condition, that is, when the total load power is not greater than the rated power of the solid oxide fuel cell system (in this embodiment, when the total load power is not greater than 100kW), the following rules apply: First branch: If the state of charge of the energy storage unit is less than the preset upper limit threshold of the state of charge (in this embodiment, the state of charge of the energy storage unit is less than 90%): When the excess power obtained by the difference between the rated power of the solid oxide fuel cell system and the total load power is not greater than the maximum charging power of the energy storage unit, the solid oxide fuel cell system is maintained at its rated power, and all excess power is input to the energy storage unit for charging.

[0053] Taking the parameters of this embodiment as an example: assuming the total load power is 90kW and the rated power of the solid oxide fuel cell system is 100kW, the excess power obtained by the difference between the rated power of the solid oxide fuel cell system and the total load power is 100 - 90 = 10kW. Since this excess power of 10kW is not greater than the maximum charging power of the energy storage unit of 20kW, the energy management system maintains the solid oxide fuel cell system at its rated power of 100kW, and inputs all the excess power of 10kW to the energy storage unit for charging. The system power balance relationship is: the output power of the solid oxide fuel cell system 100kW = total load power 90kW + energy storage unit charging power 10kW, and the power balance is achieved.

[0054] When the excess power exceeds the maximum charging power of the energy storage unit, the energy storage unit is controlled to charge at its maximum charging power. At the same time, the output power of the solid oxide fuel cell system is reduced to the larger of the sum of the total load power and the maximum charging power of the energy storage unit and the minimum stable output power of the solid oxide fuel cell system. If there is still excess power that has not been absorbed by the energy storage unit after reducing the output power to the minimum stable output power of the solid oxide fuel cell system, the adjustable load is activated to absorb the excess power.

[0055] The following explanation will be given using the parameters of this embodiment as an example, categorized by case: Scenario 1: Assuming a total load power of 60kW: Excess power = 100 - 60 = 40kW, which is greater than the maximum charging power of the energy storage unit (20kW). The energy storage unit is controlled to charge at its maximum charging power of 20kW, while the solid oxide fuel cell system's output power is reduced to the greater of the sum of the total load power and the energy storage unit's maximum charging power, and the solid oxide fuel cell system's minimum stable output power, i.e., max(60 + 20, 70) = max(80, 70) = 80kW. Therefore, the solid oxide fuel cell system reduces its output power to 80kW. At this point, the solid oxide fuel cell system's output power of 80kW = total load power 60kW + energy storage unit charging power 20kW, achieving power balance, and there is no need to activate the adjustable load. The energy management system synchronously reduces the pretreated associated gas flow supplied to the solid oxide fuel cell system via the fuel distribution valve.

[0056] Scenario 2, assuming a total load power of 40kW: Excess power = 100 - 40 = 60kW, which is greater than the maximum charging power of the energy storage unit (20kW). The energy storage unit is controlled to charge at its maximum charging power of 20kW, while the solid oxide fuel cell system's output power is reduced. The target output power = max(40 + 20, 70) = max(60,70) = 70kW, which is the minimum stable output power of the solid oxide fuel cell system. After reducing the solid oxide fuel cell system's output power to its minimum stable output power of 70kW, the actual excess power is 70 - 40 = 30kW. Of this, 20kW is absorbed by the energy storage unit at its maximum charging power, leaving a remaining excess power of 30 - 20 = 10kW. The energy management system activates the adjustable load to absorb the remaining 10kW of excess power. The system power balance is: 70kW = 40kW + 20kW + 10kW, and the power balance is achieved.

[0057] Second branch: If the state of charge of the energy storage unit is greater than or equal to the upper limit threshold of the state of charge (in this embodiment, the state of charge of the energy storage unit is greater than or equal to 90%): When the total load power is greater than or equal to the minimum stable output power of the solid oxide fuel cell system, the output power of the solid oxide fuel cell system is controlled to be reduced to match the total load power.

[0058] Taking the parameters of this embodiment as an example: assuming the total load power is 85kW and the state of charge of the energy storage unit is 92%. The total load power of 85kW is greater than or equal to the minimum stable output power of the solid oxide fuel cell system of 70kW. The output power of the solid oxide fuel cell system is controlled to decrease to match the total load power, i.e., the output power of the solid oxide fuel cell system is adjusted to 85kW. 85kW = 85kW, and power balance is achieved.

[0059] When the total load power is less than the minimum stable output power of the solid oxide fuel cell system, the solid oxide fuel cell system is maintained at the minimum stable output power of the solid oxide fuel cell system, and the adjustable load is activated to absorb the excess power obtained by the difference between the minimum stable output power of the solid oxide fuel cell system and the total load power.

[0060] Taking the parameters of this embodiment as an example: assuming the total load power is 50kW and the state of charge of the energy storage unit is 95%. The total load power of 50kW is less than the minimum stable output power of the solid oxide fuel cell system (SOFC) of 70kW. Due to the limitations of electrochemical reaction characteristics and thermal management requirements, the SOFC system cannot reduce its output power below the minimum stable output power. The energy management system maintains the SOFC system at its minimum stable output power of 70kW and activates an adjustable load to absorb the excess power obtained by the difference between the minimum stable output power and the total load power, i.e., the adjustable load absorbs 70-50 = 20kW. The system power balance relationship is: 70kW = 50kW + 20kW, and the power balance is achieved.

[0061] Special handling for the gas range extender being in operation during the first operating condition: During the execution of the first operating condition, the following transitional scenario may occur: the system was previously in the second or third operating condition, the gas range extender was already in operation, and subsequently, the oilfield's electrical load decreased, causing the total load power to drop to the range of the first operating condition. In this case, the following procedure should be followed: During the execution of the first operating condition, if the gas range extender is currently in operation, before executing the first or second branch, the gas range extender is preferentially controlled to reduce its output power until it stops, and the flow rate of pretreated associated gas allocated to the gas range extender is reduced through the fuel distribution valve until the supply of pretreated associated gas to the gas range extender stops; after the gas range extender stops, the first or second branch is executed according to the current state of charge of the energy storage unit.

[0062] The design logic behind this priority load reduction and shutdown strategy is that when the total load power has been reduced to within the range that the solid oxide fuel cell system can cover, continuing to operate the gas range extender would increase unnecessary consumption of pre-treated associated gas and mechanical wear. The power generation efficiency of the solid oxide fuel cell system (50%-55%) is significantly higher than that of the gas range extender (approximately 30%-38%), therefore prioritizing the operation of the solid oxide fuel cell system and stopping the operation of the gas range extender is the optimal economic choice.

[0063] The transition process is illustrated using the parameters of this embodiment as an example: Assume the system was previously in a steady-state operation under the third operating condition (total load power of 140kW, output power of the solid oxide fuel cell system of 100kW, and output power of the gas range extender of 40kW). Subsequently, the total load power suddenly drops to 80kW, and the state of charge of the energy storage unit is 55%. Step S4 determines that the system is currently in the first operating condition. Detecting that the gas range extender is currently operating, before executing the first or second branch, the gas range extender's output power is preferentially reduced until it shuts down. The power regulation response time of the gas range extender is approximately 5 seconds. Within approximately 5 to 10 seconds, the gas range extender's output power gradually decreases from 40kW to its minimum stable output power of 5kW before shutting down. Simultaneously, the flow rate of pretreated associated gas allocated to the gas range extender is reduced via the fuel distribution valve until the supply of pretreated associated gas to the gas range extender is stopped. After the gas-powered range extender shuts down, based on the current state of charge (SOC) of the energy storage unit (55%, less than the upper limit threshold of 90%), the first branch is executed: the solid oxide fuel cell system operates at its rated power of 100kW. The excess power = 100 - 80 = 20kW = the maximum charging power of the energy storage unit, 20kW. All of this excess power is input to the energy storage unit for charging. 100kW = 80kW + 20kW, thus achieving power balance.

[0064] II. Second Operating Condition Control Strategy In step S5, when the operating condition range determined in step S4 is the second operating condition, that is, when the total load power is greater than the rated power of the solid oxide fuel cell system and not greater than the sum of the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit (in this embodiment, the total load power is greater than 100kW and not greater than 120kW): The solid oxide fuel cell system is controlled to operate at its rated power. The difference between the total load power and the rated power of the solid oxide fuel cell system is taken as the power gap. The power gap is supplemented according to the state of charge of the energy storage unit and the current operating status of the gas range extender according to the following rules: When the state of charge of the energy storage unit is greater than or equal to the preset state of charge lower limit threshold and the gas range extender is currently in a shutdown state, the energy storage unit is controlled to output electrical energy to the common bus at a discharge power equal to the power gap to supplement the power gap.

[0065] Taking the parameters of this embodiment as an example: Assume the total load power is 110kW, the state of charge (SOC) of the energy storage unit is 50%, and the gas range extender is currently shut down. The power deficit = 110 - 100 = 10kW. Since the SOC of the energy storage unit (50%) is greater than or equal to the lower threshold of 20%, and the gas range extender is currently shut down, the energy management system controls the solid oxide fuel cell system to operate at its rated power of 100kW. Simultaneously, it controls the energy storage unit to output power to the common bus at a discharge power of 10kW, equal to the power deficit, to supplement the power deficit. The system power balance is: 100kW + 10kW = 110kW, and the power balance is achieved.

[0066] During the discharge of the energy storage unit, the energy management system continuously monitors the changes in the state of charge (SOC) of the energy storage unit. It is important to note that a new condition has been added to this conditional branch: "the gas range extender is currently in a shutdown state." This means that if the gas range extender is already in operation for other reasons (e.g., it was started because its SOC was previously below the minimum SOC threshold and the shutdown conditions have not yet been met), even if the SOC of the energy storage unit has recovered to a level greater than or equal to the minimum SOC threshold but has not yet reached the SOC recovery threshold, the system will not switch to a mode where the energy storage unit discharges and the gas range extender shuts down. Instead, the gas range extender will continue to operate. This design avoids the "ping-pong effect" caused by frequent starting and stopping of the gas range extender near the minimum SOC threshold.

[0067] When the state of charge of the energy storage unit is less than the lower limit threshold (i.e., less than 20% in this embodiment), pretreated associated gas is distributed to the gas range extender through the fuel distribution valve and the gas range extender is started. When the power gap is greater than or equal to the minimum stable output power of the gas range extender, the gas range extender is controlled to operate at an output power equal to the power gap.

[0068] Taking the parameters of this embodiment as an example: Assume the total load power is 115kW, and the state of charge of the energy storage unit is 10%. The power deficit = 115 - 100 = 15kW, which is greater than or equal to the minimum stable output power of the gas range extender, 5kW. The energy management system distributes pretreated associated gas to the gas range extender through the fuel distribution valve and starts the gas range extender, controlling it to operate at an output power of 15kW, equal to the power deficit. The system power balance relationship is: 100kW + 15kW = 115kW, and the power balance is achieved.

[0069] When the power deficit is less than the minimum stable output power of the gas range extender, the gas range extender is controlled to operate at its minimum stable output power. The excess power obtained by the difference between the minimum stable output power of the gas range extender and the power deficit is preferentially input to the energy storage unit for charging. When the excess power exceeds the maximum charging power of the energy storage unit, it is absorbed by the adjustable load.

[0070] Taking the parameters of this embodiment as an example: Assume the total load power is 103kW, and the state of charge (SOC) of the energy storage unit is 10%. The power deficit = 103 - 100 = 3kW, which is less than the minimum stable output power of the gas range extender, 5kW. The gas range extender is started and controlled to operate at its minimum stable output power of 5kW. The excess power obtained by the difference between the minimum stable output power of the gas range extender and the power deficit is 5 - 3 = 2kW. Since the SOC of the energy storage unit is 10% (less than the lower threshold of 20%), the energy storage unit needs to be replenished. This 2kW excess power is preferentially input to the energy storage unit for charging. This excess power of 2kW is much less than the maximum charging power of the energy storage unit, 20kW, so it is all absorbed by the energy storage unit. The system power balance relationship is: 100kW + 5kW = 103kW + 2kW = 105kW, and the power balance is achieved.

[0071] Regarding hysteresis control mechanisms: When the gas range extender is started due to the state of charge of the energy storage unit being lower than the lower limit threshold, the energy management system maintains the continuous operation of the gas range extender and dynamically adjusts the output power of the gas range extender according to the real-time changes in the power gap. Only when the state of charge of the energy storage unit recovers to the preset state of charge recovery threshold can the energy management system control the gas range extender to shut down and switch to discharging from the energy storage unit to the common bus to supplement the power gap. The state of charge recovery threshold is higher than the lower limit threshold.

[0072] In this embodiment, the state-of-charge recovery threshold is 40%, and the state-of-charge lower limit threshold is 20%. The state-of-charge recovery threshold of 40% is higher than the state-of-charge lower limit threshold of 20%. The design logic of this hysteresis control mechanism is as follows: When the state of charge (SBC) of the energy storage unit drops from above the SBC threshold of 20% to below 20%, the system activates the gas range extender. Subsequently, during the operation of the gas range extender, even if the SBC of the energy storage unit gradually recovers and exceeds the SBC threshold of 20% again (e.g., to 25%) through excess power charging from the gas range extender, the energy management system will not immediately shut down the gas range extender. The gas range extender continues to operate, both continuing to provide power support to the load and continuously charging the energy storage unit with excess power, thus allowing the SBC of the energy storage unit to continue to rise.

[0073] Only when the state of charge (SBC) of the energy storage unit recovers to the SBC recovery threshold of 40% can the energy management system control the gas range extender to shut down and switch to discharging from the energy storage unit to the common bus to supplement the power gap. Since the SBC of the energy storage unit has reached 40% at this time, it has sufficient power margin. Even if it continues to discharge subsequently, it will take a long time for the SBC to drop below the lower SBC threshold of 20% again, thus effectively avoiding frequent start-stops of the gas range extender near the lower SBC threshold.

[0074] Quantitatively illustrating the parameters of this embodiment: The energy storage unit has a capacity of 20kWh, and the amount of electricity that can be released when the state of charge (SBC) discharges from 40% to 20% is 20kWh × (40% - 20%) = 4kWh. Assuming a continuous power deficit of 10kW, the energy storage unit can independently discharge for approximately 4kWh ÷ 10kW = 0.4 hours (24 minutes). Without a hysteresis interval, a 1% fluctuation in SBC around 20% (i.e., 0.2kWh) would be consumed in approximately 72 seconds at a 10kW discharge power, potentially causing the gas range extender to start and stop every tens of seconds to several minutes. This would cause severe impact damage to the gas range extender's starter motor, ignition system, and generator components, significantly shortening their lifespan. The 20% hysteresis interval between the SBC recovery threshold and the SBC lower limit threshold extends the shortest operating cycle of the gas range extender to over 20 minutes, effectively protecting equipment safety.

[0075] III. Third Operating Condition Control Strategy In step S5, when the operating condition range determined in step S4 is the third operating condition, that is, when the total load power is greater than the sum of the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit (in this embodiment, the total load power is greater than 120kW): The solid oxide fuel cell system is controlled to operate at its rated power. Simultaneously, pretreated associated gas is distributed to the gas range extender via a fuel distribution valve, and the gas range extender is started. The power distribution method is determined based on the state of charge of the energy storage unit. When the state of charge of the energy storage unit is greater than or equal to the preset state of charge lower limit threshold (in this embodiment, the state of charge of the energy storage unit is greater than or equal to 20%), the energy storage unit is simultaneously controlled to discharge to the common bus, and the output power of the gas range extender is adjusted so that the sum of the output power of the solid oxide fuel cell system, the discharge power of the energy storage unit, and the output power of the gas range extender matches the total load power.

[0076] Taking the parameters of this embodiment as an example: Assume the total load power is 140kW, and the state of charge (SOC) of the energy storage unit is 60%. The solid oxide fuel cell system operates at its rated power of 100kW. The SOC of the energy storage unit (60%) is greater than or equal to the lower threshold of 20%, and the energy storage unit is simultaneously controlled to discharge to the common bus. The energy management system allocates power according to the capacity of each unit: the energy storage unit discharges to the common bus at its maximum discharge power of 20kW. The output power of the gas range extender = total load power - output power of the solid oxide fuel cell system - discharge power of the energy storage unit = 140 - 100 - 20 = 20kW. The output power of the solid oxide fuel cell system (100kW) + the discharge power of the energy storage unit (20kW) + the output power of the gas range extender (20kW) = 140kW = total load power of 140kW. The sum of these three values ​​matches the total load power, and power balance is achieved.

[0077] In this mode, because the energy storage unit participates in power sharing, the power shortfall that the gas range extender needs to bear is reduced from 40kW to 20kW, which lowers the load level of the gas range extender and helps extend its service life and reduce fuel consumption. At the same time, when the load fluctuates rapidly, the energy storage unit can provide instantaneous power support with its millisecond-level response speed to compensate for the short-term power fluctuations caused by the second-level response delay of the gas range extender.

[0078] When the state of charge of the energy storage unit is less than the lower limit threshold of the state of charge (in this embodiment, the state of charge of the energy storage unit is less than 20%), the output power of the gas range extender is adjusted to be equal to the difference between the total load power and the rated power of the solid oxide fuel cell system, so that the sum of the output power of the solid oxide fuel cell system and the output power of the gas range extender matches the total load power.

[0079] Taking the parameters of this embodiment as an example: Assume the total load power is 140kW, and the state of charge (SOC) of the energy storage unit is 10%. The solid oxide fuel cell system operates at its rated power of 100kW. Since the SOC of the energy storage unit is 10%, which is less than the lower threshold of 20%, the energy storage unit does not participate in discharging. The output power of the gas range extender is adjusted to equal the difference between the total load power and the rated power of the solid oxide fuel cell system = 140 - 100 = 40kW. The output power of the solid oxide fuel cell system (100kW) + the output power of the gas range extender (40kW) = 140kW = the total load power (140kW). The sum of these two values ​​matches the total load power, thus achieving power balance.

[0080] In this embodiment, since the rated power of the gas range extender is 50kW, when the energy storage unit participates in discharging, the maximum total load power that the system can cover is 100kW + 20kW + 50kW = 170kW; when the energy storage unit does not participate in discharging, the maximum total load power that the system can cover is 100kW + 50kW = 150kW. The maximum total load power at this oilfield site is 150kW, and the system capacity design meets the requirements.

[0081] IV. Handling the start-up transition phase of the gas range extender In the second operating condition control strategy described above, where the state of charge of the energy storage unit is less than the lower limit threshold of the state of charge, and in the third operating condition control strategy, both involve the process of starting the gas range extender from a shutdown state until it reaches the target output power. During the transition phase from starting the gas range extender to it reaching the target output power, the gas range extender has not yet reached the target output power, and there is a risk that the power shortfall cannot be filled in time. This embodiment handles this transition phase as follows: If the state of charge of the energy storage unit is greater than the preset short-time discharge protection threshold (in this embodiment, the state of charge of the energy storage unit is greater than 15%), the energy storage unit is controlled to discharge to the common bus for a short time during the transition phase to provide instantaneous power support; when the gas range extender reaches the target output power, the energy storage unit is controlled to stop discharging, and the gas range extender takes over the power output of the energy storage unit.

[0082] Taking the parameters of this embodiment as an example: In the third operating condition, assuming the total load power is 140kW, the state of charge of the energy storage unit is 60%, and the gas range extender is in a stopped state and needs to be started. The solid oxide fuel cell system operates at the rated power of 100kW, with a power deficit of 40kW.

[0083] From 0 seconds to approximately 5 seconds: The gas range extender is starting up, and its output power gradually increases from zero. Since the energy storage unit's state of charge (60%) is greater than the short-time discharge protection threshold of 15%, the energy storage unit is controlled to briefly discharge to the common bus during the transition phase to provide instantaneous power support. The energy storage unit outputs power to the common bus at its maximum discharge power of 20kW or the difference between the actual power deficit and the current power supply (whichever is smaller).

[0084] From approximately 5 to 30 seconds: The output power of the gas range extender gradually increases to the target output power. During this period, the discharge power of the energy storage unit decreases accordingly as the output power of the gas range extender increases, and the two work together to ensure that the total output power of the system on the common bus is close to the total load power.

[0085] 30 seconds later: The gas range extender reaches the target output power and operates stably. The control energy storage unit stops discharging, and the gas range extender takes over the power output of the energy storage unit. The system then enters steady-state operation mode.

[0086] The short-time discharge protection threshold (15%) is lower than the state-of-charge (SOC) limit threshold (20%) because this discharge behavior is a short-term, emergency power support, typically lasting no more than 30 seconds, and has a limited impact on the battery's depth of discharge. Even if the energy storage unit's SOC is between 15% and 20%, a 30-second short-time discharge will only consume approximately 20kW × 30 seconds / 3600 seconds ≈ 0.17kWh, which is only about 0.85% of the total 20kWh capacity of the lithium iron phosphate battery pack, and has a very small actual impact on the energy storage unit's SOC. However, when the energy storage unit's SOC is no greater than the short-time discharge protection threshold of 15%, discharge is no longer allowed to protect the battery. At this time, during the start-up transition phase of the gas range extender, a brief power fluctuation may occur on the oilfield's electrical load side. The energy management system maintains the power supply quality as much as possible through the voltage and frequency regulation functions of the first and second inverters.

[0087] Supplementary numerical examples To further illustrate the complete working process of the fuel storage method in this embodiment under various typical operating conditions, the following detailed analysis of several typical operating scenarios is given in conjunction with specific numerical values.

[0088] Scenario 1: Stable operation under low load, with the energy storage unit having charging capacity.

[0089] Total load power = 90kW, energy storage unit state of charge = 50%, gas range extender is in shutdown state.

[0090] Step S4 determination: The total load power of 90kW is not greater than the rated power of the solid oxide fuel cell system of 100kW, and the current condition is the first operating condition.

[0091] Step S5 is executed: The state of charge (SOC) of the energy storage unit is less than the upper threshold of 90%, so the first branch of the first operating condition is executed. The excess power obtained by the difference between the rated power of the solid oxide fuel cell system and the total load power is 10kW, which is not greater than the maximum charging power of the energy storage unit (20kW). The solid oxide fuel cell system is maintained at its rated power of 100kW, and all excess power (10kW) is input to the energy storage unit for charging.

[0092] Power balance check: 100kW = 90kW + 10kW.

[0093] Scenario 2: Operating under extremely low load, with the energy storage unit having charging capacity.

[0094] Total load power = 40kW, energy storage unit state of charge = 50%, gas range extender is in shutdown state.

[0095] Step S4 Judgment: First working condition.

[0096] Step S5 execution: The state of charge (SOC) of the energy storage unit is less than the upper limit threshold of 90%, so the first branch of the first operating condition is executed. Excess power = 60kW, which is greater than the maximum charging power of the energy storage unit (20kW). The energy storage unit is controlled to charge at its maximum charging power of 20kW. The solid oxide fuel cell system reduces its output power to max(40+20, 70) = 70kW. Remaining excess power = 70-40-20 = 10kW, and the adjustable load is activated to absorb the remaining excess power of 10kW.

[0097] Power balance check: 70kW = 40kW + 20kW + 10kW.

[0098] Scenario 3: Low load operation, energy storage unit is almost fully charged.

[0099] Total load power = 50kW, energy storage unit state of charge = 95%, gas range extender is in shutdown state.

[0100] Step S4 Judgment: First working condition.

[0101] Step S5 execution: The state of charge (SOC) of the energy storage unit is 95% greater than or equal to the upper limit threshold of SOC of 90%, and the second branch of the first operating condition is executed. The total load power of 50kW is less than the minimum stable output power of the solid oxide fuel cell system of 70kW, so the solid oxide fuel cell system is maintained at the minimum stable output power of 70kW, and the adjustable load is started to absorb 20kW.

[0102] Power balance check: 70kW = 50kW + 20kW.

[0103] Scenario 4: The load slightly exceeds the rated power of the solid oxide fuel cell system, and the energy storage unit discharges to support it.

[0104] Total load power = 110kW, energy storage unit state of charge = 50%, gas range extender is in shutdown state.

[0105] Step S4: Determine the second operating condition.

[0106] Step S5 execution: The energy storage unit's state of charge (SOC) is 50% or greater than or equal to the SOC lower threshold of 20%, and the gas range extender is currently shut down. Power deficit = 10kW. Control the energy storage unit to output electrical energy to the common bus at a discharge power of 10kW, equal to the power deficit. Power balance verification: 100kW + 10kW = 110kW.

[0107] Scenario 5: In the second operating condition, the energy storage unit is low on power, triggering hysteresis control.

[0108] The total load power is 110kW. The state of charge of the energy storage unit gradually decreases from 25% to 18% (below the lower limit threshold of 20%), and the gas range extender is in a shutdown state.

[0109] Step S4: Determine the second operating condition.

[0110] Step S5 execution: The state of charge (SOC) of the energy storage unit is 18%, which is less than the lower limit threshold of 20%. Pretreated associated gas is distributed to the gas range extender via the fuel distribution valve, and the gas range extender is started. Power shortfall = 10kW, greater than or equal to the minimum stable output power of the gas range extender (5kW). The gas range extender is controlled to operate at an output power equal to the power shortfall, 10kW. Power balance verification: 100kW + 10kW = 110kW.

[0111] Subsequently, after the gas range extender starts due to the energy storage unit's state of charge (SOC) falling below the lower threshold, the energy management system maintains continuous operation of the gas range extender. Assuming the total load power remains at 110kW, the gas range extender operates continuously at 10kW. During this period, the energy storage unit neither charges nor discharges (because the power deficit is exactly equal to the gas range extender's output power). If subsequent changes in the power deficit cause the gas range extender to generate excess power, this excess power charges the energy storage unit, and the energy storage unit's SOC gradually recovers.

[0112] When the state of charge of the energy storage unit recovers to the 40% state of charge recovery threshold, the energy management system can then shut down the gas range extender and switch to discharging from the energy storage unit to the common bus to compensate for the power shortfall. Afterward, the system returns to a mode supported by the energy storage unit's discharge.

[0113] Assuming the energy storage unit's state of charge recovers to 40%, and it operates at a discharge power of 10kW, the time it can independently discharge is approximately 20kWh × (40% - 20%) ÷ 10kW = 0.4 hours = 24 minutes, effectively avoiding the gas range extender from repeatedly starting and stopping in a short period of time.

[0114] Scenario 6: Third operating condition, energy storage unit participates in discharge coordination.

[0115] Total load power = 140kW, energy storage unit state of charge = 60%, gas range extender is in shutdown state.

[0116] Step S4 determination: The total load power of 140kW is greater than the sum of the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit of 120kW, and the current condition is the third operating condition.

[0117] Step S5 execution: The state of charge (SOC) of the energy storage unit is 60% greater than or equal to the lower threshold of SOC of 20%. Control the solid oxide fuel cell system to operate at its rated power of 100kW, simultaneously controlling the energy storage unit to discharge 20kW (the maximum discharge power of the energy storage unit) to the common bus, and adjusting the output power of the gas range extender to 140 - 100 - 20 = 20kW. The total output power of the solid oxide fuel cell system (100kW) + the discharge power of the energy storage unit (20kW) + the output power of the gas range extender (20kW) = 140kW, matching the total load power. Power balance verification: 100kW + 20kW + 20kW = 140kW.

[0118] Transition Phase Handling: When the state of charge (SOC) of the energy storage unit is 60% higher than the short-time discharge protection threshold of 15%, the energy storage unit is controlled to perform a short-time discharge to the common bus during the transition phase of the gas range extender startup to provide instantaneous power support. Once the gas range extender reaches its target output power, the energy storage unit switches from emergency short-time discharge to steady-state continuous discharge (20kW), with the gas range extender taking over the additional power supplied during the emergency discharge.

[0119] Scenario 7: Third operating condition, the energy storage unit has insufficient power.

[0120] Total load power = 140kW, energy storage unit state of charge = 10%, gas range extender is in shutdown state.

[0121] Step S4 judgment: Third working condition.

[0122] Step S5 execution: The state of charge (SOC) of the energy storage unit is 10%, which is less than the lower threshold of 20%. Adjust the output power of the gas range extender to equal the difference between the total load power and the rated power of the solid oxide fuel cell system = 140 - 100 = 40kW. The output power of the solid oxide fuel cell system (100kW) + the output power of the gas range extender (40kW) = 140kW, and the sum of these two matches the total load power. Power balance verification: 100kW + 40kW = 140kW.

[0123] Transition phase handling: The state of charge of the energy storage unit is not greater than 10% of the short-time discharge protection threshold of 15%. The energy storage unit will not provide short-time discharge support. During the transition period, there may be brief power fluctuations on the oilfield's power load side.

[0124] Scenario 8: The transition process from high-load to low-load conditions.

[0125] The system was previously in steady-state operation under scenario six (total load power 140kW, output power of solid oxide fuel cell system 100kW, energy storage unit discharge 20kW, gas range extender output power 20kW), then the total load power suddenly dropped to 80kW, and the state of charge of energy storage unit was 45%.

[0126] Step S4 determination: The total load power of 80kW is not greater than the rated power of the solid oxide fuel cell system of 100kW, and the current condition is the first operating condition.

[0127] Step S5 execution: During the execution of the first operating condition, the gas range extender is currently in operation. Before executing the first or second branch, the gas range extender is preferentially controlled to reduce its output power until it stops. Simultaneously, the flow rate of pretreated associated gas allocated to the gas range extender is reduced through the fuel distribution valve until the supply of pretreated associated gas to the gas range extender stops. At the same time, the energy storage unit is controlled to stop discharging.

[0128] After the gas range extender shuts down, based on the current state of charge (SOC) of the energy storage unit (45%, less than the upper limit threshold of 90%), the first branch is executed: the solid oxide fuel cell system operates at its rated power of 100kW. Excess power = 100 - 80 = 20kW = the maximum charging power of the energy storage unit (20kW). All excess power is then input to the energy storage unit for charging. Power balance verification: 100kW = 80kW + 20kW

[0129] Through the coordinated execution of steps S1 to S5 above, the combustion and storage method based on associated gas in oil fields in this embodiment achieves the following technical effects: First, in terms of load regulation, through a four-level synergy—the solid oxide fuel cell system as a high-efficiency baseload power source, the gas range extender as a rapid peak-shaving power source, the energy storage unit as an instantaneous power support source, and the adjustable load as a means of absorbing excess power—the system can achieve rapid and stable power regulation across the entire load range of 30kW to 150kW. In the third operating condition, the energy storage unit actively participates in power sharing based on its state of charge, achieving true "fuel cell-storage synergistic" scheduling.

[0130] Secondly, in terms of control stability, the control strategy for the second operating condition introduces a hysteresis control range between the state of charge recovery threshold and the state of charge limit threshold. This effectively eliminates the "ping-pong effect" caused by the small fluctuations in the state of charge of the energy storage unit near the state of charge limit threshold, which leads to frequent start-stop of the gas range extender. This protects the starter motor and mechanical components of the gas range extender and extends the service life of the equipment.

[0131] Third, in terms of energy efficiency, the solid oxide fuel cell system, as the main power generation unit, achieves a power generation efficiency of 50%-55%. Combined with the waste heat recovery unit for recovering and utilizing the waste heat of high-temperature exhaust gas, the overall energy efficiency of the system is increased to over 70%.

[0132] Fourth, regarding the utilization rate of associated gas, the energy management system enables flexible control of the fuel distribution valve, allowing the pretreated associated gas to be rationally allocated to at least one of the solid oxide fuel cell system and the gas range extender for efficient utilization based on the total load power. The utilization rate of associated gas is improved by approximately 15% to 25% compared to traditional systems.

[0133] Fifth, in terms of closed-loop waste heat recovery, the waste heat recovery unit converts the heat energy in the high-temperature exhaust gas into hot water and / or steam, which is then fed back to the associated gas pretreatment unit as a heating source, thus realizing the cascade utilization of energy. Example 2

[0134] This embodiment is based on the previous embodiment, and the parts that are the same as in Embodiment 1 will not be described in detail here. See also Figure 2 This embodiment discloses a fuel-storage system based on associated gas from an oilfield, comprising: The associated gas pretreatment unit is used to dehydrate, desulfurize and filter the raw oilfield associated gas to output pretreated associated gas that meets the preset purity requirements. The associated gas pretreatment unit includes a molecular sieve dehydration device, an activated carbon desulfurization device and a filter arranged in series. The associated gas pretreatment unit is equipped with a heat source input terminal. A fuel distribution valve, the input end of which is connected to the output end of the associated gas pretreatment unit, the fuel distribution valve having a first output end and a second output end, is used to distribute the pretreated associated gas to downstream gas-consuming equipment as needed; A solid oxide fuel cell system, wherein the fuel input end of the solid oxide fuel cell system is connected to the first output end of the fuel distribution valve for generating electricity through an electrochemical reaction using the pretreated associated gas as fuel, and the power output end of the solid oxide fuel cell system is connected to a common bus through a first inverter; A gas range extender, wherein the fuel input end of the gas range extender is connected to the second output end of the fuel distribution valve, and is used to drive a generator to generate electricity using the pretreated associated gas as fuel; the power output end of the gas range extender is connected to the common bus via a second inverter. An energy storage unit is bidirectionally electrically connected to the common bus via a bidirectional converter. It is used to absorb and store excess electrical energy from the common bus when the total output power of the system is greater than the total load power, and to release electrical energy to the common bus when the total output power of the system is less than the total load power. An adjustable load, which is electrically connected to the common bus, is used to absorb the excess electrical energy on the common bus when the energy storage unit cannot fully absorb the excess electrical energy. The waste heat recovery unit has its input end connected to the exhaust gas outlet of the solid oxide fuel cell system and the exhaust gas outlet of the gas range extender, respectively, and its output end connected to the heat source input end of the associated gas pretreatment unit. It is used to recover the waste heat in the high-temperature exhaust gas generated by the solid oxide fuel cell system and the gas range extender and convert it into hot water and / or steam to be fed back to the associated gas pretreatment unit. An energy management system is communicatively connected to the fuel distribution valve, the solid oxide fuel cell system, the gas range extender, the energy storage unit, and the adjustable load, and is also communicatively connected to a load monitoring device installed on the common bus. This system is used to collect in real time the total load power, the output power of the solid oxide fuel cell system, the output power of the gas range extender, the state of charge of the energy storage unit, and the charging and discharging power of the energy storage unit. The system compares the total load power with a tiered threshold set based on the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit to determine the current operating condition range. Based on the operating condition range and the state of charge of the energy storage unit, the system generates control commands and sends them to each controlled unit to dynamically coordinate the operation of each unit so that the total system output power matches the total load power.

[0135] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A combustion-storage method based on associated gas from oil fields, characterized in that, Includes the following steps: Step S1: The raw associated gas from the oilfield is pretreated by the associated gas pretreatment unit to output pretreated associated gas that meets the preset purity requirements. In step S2, the pretreated associated gas is distributed to at least one of the solid oxide fuel cell system and the gas range extender for power generation via a fuel distribution valve. The electrical energy generated by the solid oxide fuel cell system is output to the common bus via a first inverter, and the electrical energy generated by the gas range extender is output to the common bus via a second inverter. An energy storage unit and an adjustable load are also connected to the common bus, and the common bus supplies power to the oilfield's electrical load. Step S3: The total load power on the common bus, the output power of the solid oxide fuel cell system, the output power of the gas range extender, the state of charge of the energy storage unit, and the charging and discharging power of the energy storage unit are collected in real time through the energy management system. Step S4: The energy management system compares the total load power with a grading threshold set based on the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit to determine the current operating condition range. In step S5, the energy management system generates control commands based on the operating condition range determined in step S4 and the state of charge of the energy storage unit, and sends them to at least one of the fuel distribution valve, the solid oxide fuel cell system, the gas range extender, the energy storage unit, and the adjustable load, so as to dynamically adjust the operating status of each unit and match the total output power of the system with the total load power.

2. The combustion and storage method based on associated gas from oilfields according to claim 1, characterized in that, Step S4 also includes the step of calculating the power difference according to the following formula: Power difference = Total load power - (Output power of solid oxide fuel cell system + Output power of gas range extender + Charging and discharging power of energy storage unit); In the control process of step S5, the energy management system uses the power difference approaching zero as the adjustment target to perform closed-loop power regulation on each unit.

3. The combustion and storage method based on associated gas from oilfields according to claim 1, characterized in that, In step S5, when the operating condition range determined in step S4 is the first operating condition, that is, when the total load power is not greater than the rated power of the solid oxide fuel cell system, the following rules apply: First branch: If the state of charge of the energy storage unit is less than the preset upper limit threshold of the state of charge: When the excess power obtained by the difference between the rated power of the solid oxide fuel cell system and the total load power is not greater than the maximum charging power of the energy storage unit, the solid oxide fuel cell system is maintained at the rated power of the solid oxide fuel cell system, and all the excess power is input to the energy storage unit for charging. When the excess power exceeds the maximum charging power of the energy storage unit, the energy storage unit is controlled to charge at its maximum charging power, while the solid oxide fuel cell system is controlled to reduce its output power to the greater of the sum of the total load power and the maximum charging power of the energy storage unit and the minimum stable output power of the solid oxide fuel cell system. If there is still excess power that has not been absorbed by the energy storage unit after reducing the output power to the minimum stable output power of the solid oxide fuel cell system, the adjustable load is activated to absorb the excess power. Second branch: If the state of charge of the energy storage unit is greater than or equal to the upper limit threshold of the state of charge: When the total load power is greater than or equal to the minimum stable output power of the solid oxide fuel cell system, the solid oxide fuel cell system is controlled to reduce its output power to match the total load power. When the total load power is less than the minimum stable output power of the solid oxide fuel cell system, the solid oxide fuel cell system is maintained at the minimum stable output power of the solid oxide fuel cell system, and the adjustable load is activated to absorb the excess power obtained by the difference between the minimum stable output power of the solid oxide fuel cell system and the total load power.

4. The combustion and storage method based on associated gas from oilfields according to claim 1, characterized in that, In step S5, when the operating condition range determined in step S4 is the second operating condition, that is, when the total load power is greater than the rated power of the solid oxide fuel cell system and not greater than the sum of the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit: The solid oxide fuel cell system is controlled to operate at its rated power. The difference between the total load power and the rated power of the solid oxide fuel cell system is taken as the power gap. The power gap is supplemented according to the state of charge of the energy storage unit and the current operating state of the gas range extender according to the following rules: When the state of charge of the energy storage unit is greater than or equal to the preset state of charge lower limit threshold and the gas range extender is currently in a shutdown state, the energy storage unit is controlled to output electrical energy to the common bus with a discharge power equal to the power gap, so as to supplement the power gap; When the state of charge of the energy storage unit is less than the lower threshold of the state of charge, the pretreated associated gas is allocated to the gas range extender through the fuel distribution valve and the gas range extender is started. When the power deficit is greater than or equal to the minimum stable output power of the gas range extender, the gas range extender is controlled to operate at an output power equal to the power deficit. When the power deficit is less than the minimum stable output power of the gas range extender, the gas range extender is controlled to operate at the minimum stable output power of the gas range extender, and the excess power obtained by the difference between the minimum stable output power of the gas range extender and the power deficit is preferentially input to the energy storage unit for charging. When the excess power exceeds the maximum charging power of the energy storage unit, it is absorbed by the adjustable load. When the gas range extender is activated due to the state of charge (SBC) of the energy storage unit being lower than the SBC threshold, the energy management system maintains the continuous operation of the gas range extender and dynamically adjusts the output power of the gas range extender according to the real-time changes in the power gap. Only when the SBC of the energy storage unit recovers to the preset SBC recovery threshold can the energy management system control the gas range extender to shut down and switch to discharging from the energy storage unit to the common bus to supplement the power gap. The SBC recovery threshold is higher than the SBC threshold.

5. The combustion and storage method based on associated gas from oilfields according to claim 1, characterized in that, In step S5, when the operating condition range determined in step S4 is the third operating condition, that is, when the total load power is greater than the sum of the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit: The solid oxide fuel cell system is controlled to operate at its rated power. Simultaneously, the pretreated associated gas is distributed to the gas range extender via the fuel distribution valve, and the gas range extender is started. The power distribution method is determined based on the state of charge of the energy storage unit. When the state of charge of the energy storage unit is greater than or equal to the preset state of charge lower threshold, the energy storage unit is simultaneously controlled to discharge to the common bus, and the output power of the gas range extender is adjusted so that the sum of the output power of the solid oxide fuel cell system, the discharge power of the energy storage unit, and the output power of the gas range extender matches the total load power. When the state of charge of the energy storage unit is less than the lower limit threshold of the state of charge, the output power of the gas range extender is adjusted to be equal to the difference between the total load power and the rated power of the solid oxide fuel cell system, so that the sum of the output power of the solid oxide fuel cell system and the output power of the gas range extender matches the total load power.

6. The combustion and storage method based on associated gas from oilfields according to claim 3, characterized in that, During the execution of the first operating condition, if the gas range extender is currently in operation, before executing the first branch or the second branch, the gas range extender is preferentially controlled to reduce its output power until it stops, and the flow rate of the pre-treated associated gas allocated to the gas range extender is simultaneously reduced through the fuel distribution valve until the supply of the pre-treated associated gas to the gas range extender is stopped. After the gas range extender stops, the first branch or the second branch is executed according to the current state of charge of the energy storage unit.

7. The combustion and storage method based on associated gas from oilfields according to claim 4 or 5, characterized in that, During the transition phase from the start-up of the gas range extender to the point where the gas range extender reaches its target output power: If the state of charge of the energy storage unit is greater than the preset short-time discharge protection threshold, the energy storage unit is controlled to discharge to the common bus for a short time during the transition phase to provide instantaneous power support; when the gas range extender reaches the target output power, the energy storage unit is controlled to stop discharging, and the gas range extender takes over the power output of the energy storage unit.

8. The combustion and storage method based on associated gas from oilfields according to claim 1, characterized in that, The preprocessing in step S1 specifically includes: The raw associated gas from the oilfield is sequentially subjected to dehydration, desulfurization, and filtration treatments: The dehydration process removes moisture from the original associated gas from the oilfield. The desulfurization process removes hydrogen sulfide from the gas after the dehydration process, ensuring that the hydrogen sulfide content after the process does not exceed a preset desulfurization threshold. The filtration process removes mechanical impurities from the gas after desulfurization, ensuring that the particle size of the treated particulate matter does not exceed a preset filtration accuracy threshold. The dehydration treatment, the desulfurization treatment, and the filtration treatment are performed sequentially, with the output gas of the previous treatment serving as the input gas for the next treatment, and the gas output from the filtration treatment serving as the associated gas from the pretreatment treatment.

9. The combustion and storage method based on associated gas from oilfields according to claim 1, characterized in that, In the power generation process of step S2, a waste heat recovery step is also performed in parallel: The high-temperature exhaust gas generated during the power generation process of the solid oxide fuel cell system and / or the high-temperature exhaust gas generated during the power generation process of the gas range extender is collected, and the collected high-temperature exhaust gas is input into the waste heat recovery unit. The waste heat recovery unit converts the heat energy in the high-temperature exhaust gas into hot water and / or steam for output. The hot water and / or steam output from the waste heat recovery unit are fed back to the associated gas pretreatment unit as the heating source for the pretreatment process in step S1.

10. A fuel-storage system based on associated gas from an oilfield, used to implement the method as described in any one of claims 1 to 9, characterized in that, include: The associated gas pretreatment unit is used to dehydrate, desulfurize and filter the raw oilfield associated gas, and output pretreated associated gas that meets the preset purity requirements. The associated gas pretreatment unit includes a molecular sieve dehydration device, an activated carbon desulfurization device and a filter arranged in series. The associated gas pretreatment unit is provided with a heat source input terminal. A fuel distribution valve, the input end of which is connected to the output end of the associated gas pretreatment unit, the fuel distribution valve having a first output end and a second output end, is used to distribute the pretreated associated gas to downstream gas-consuming equipment as needed; A solid oxide fuel cell system, wherein the fuel input end of the solid oxide fuel cell system is connected to the first output end of the fuel distribution valve for generating electricity through an electrochemical reaction using the pretreated associated gas as fuel, and the power output end of the solid oxide fuel cell system is connected to a common bus through a first inverter; A gas range extender, wherein the fuel input end of the gas range extender is connected to the second output end of the fuel distribution valve, and is used to drive a generator to generate electricity using the pretreated associated gas as fuel; the power output end of the gas range extender is connected to the common bus via a second inverter. An energy storage unit is bidirectionally electrically connected to the common bus via a bidirectional converter. It is used to absorb and store excess electrical energy from the common bus when the total output power of the system is greater than the total load power, and to release electrical energy to the common bus when the total output power of the system is less than the total load power. An adjustable load, which is electrically connected to the common bus, is used to absorb the excess electrical energy on the common bus when the energy storage unit cannot fully absorb the excess electrical energy. The waste heat recovery unit has its input end connected to the exhaust gas outlet of the solid oxide fuel cell system and the exhaust gas outlet of the gas range extender, respectively, and its output end connected to the heat source input end of the associated gas pretreatment unit. It is used to recover the waste heat in the high-temperature exhaust gas generated by the solid oxide fuel cell system and the gas range extender and convert it into hot water and / or steam to be fed back to the associated gas pretreatment unit. An energy management system is communicatively connected to the fuel distribution valve, the solid oxide fuel cell system, the gas range extender, the energy storage unit, and the adjustable load, and is also communicatively connected to a load monitoring device installed on the common bus. This system is used to collect in real time the total load power, the output power of the solid oxide fuel cell system, the output power of the gas range extender, the state of charge of the energy storage unit, and the charging and discharging power of the energy storage unit. The system compares the total load power with a tiered threshold set based on the rated power of the solid oxide fuel cell system and the maximum discharge power of the energy storage unit to determine the current operating condition range. Based on the operating condition range and the state of charge of the energy storage unit, the system generates control commands and sends them to each controlled unit to dynamically coordinate the operation of each unit so that the total system output power matches the total load power.

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