A multi-gas-source pressure concentration recovery and intelligent grid-connected power generation control method

Abstract

The present application relates to a kind of multi-gas source pressure recovery and intelligent grid-connected power generation control method, belong to pressure recovery and grid-connected power generation control technical field.The method includes for each residual pressure gas source distribution access channel and carry out hierarchical pretreatment, and each gas source is converged as mixed residual pressure gas source;Detection of the parameters of the manifold, calculate the comprehensive energy quality index and determine the energy quality grade;According to energy quality grade, select the appropriate unit from the generator set group to form the online generator set group;With grid parameters as benchmark, in turn complete master group and slave unit grid-connected, and distribute load according to capacity proportion;Monitor gas source fluctuation, execute adaptive adjustment and smooth switching;And abnormal protection processing.The present application realizes the centralized recovery and intelligent utilization of the residual pressure of multiple gas sources, improves the comprehensive utilization rate of residual pressure energy.

Description

Technical Field

[0001] This invention belongs to the field of residual pressure recovery and grid-connected power generation control technology, specifically involving a multi-source residual pressure centralized recovery and intelligent grid-connected power generation control method. Background Technology

[0002] Waste pressure power generation technology converts excess pressure energy from industrial production or energy transmission and distribution processes into electrical energy, which is an important way to achieve energy cascade utilization and reduce carbon emissions. In practical application scenarios such as industrial parks and natural gas transmission and distribution stations, there are often multiple waste pressure gas sources with different pressure levels, flow characteristics, and compositions. How to achieve centralized recovery and unified scheduling of multiple gas sources is a major challenge currently facing waste pressure power generation technology.

[0003] The core challenge in centralized recovery of multi-source residual pressure lies in the highly discrete pressure, temperature, flow rate, and composition of different gas sources. Turbine expanders and generator sets have fixed design operating ranges and optimal operating intervals. This parameter mismatch makes it difficult for the mixed gas after direct confluence to be efficiently utilized by the power generation equipment. Existing technology CN106230025B discloses an intelligent energy supply control system based on photovoltaic energy storage and waste heat and pressure power generation. This system connects a single residual pressure power generation input interface to the system via a grid-connected module to achieve grid-connected control. However, it only supports single gas source access and lacks independent pre-processing devices for different gas source pressures and temperatures. This fails to unify the discrete parameters of multiple gas sources within the allowable range of the main confluence pipe, leading to mutual interference and increased energy loss between different gas sources during direct confluence. Existing technology CN119145949B discloses an intelligent expander residual pressure power generation system that obtains valve adjustment values ​​and adjusts impeller speed by monitoring expander load information. However, its monitoring and adjustment occur within the expander itself, not at the gas source access end, and do not address the parameter adaptation issues of each branch before multi-source confluence. Existing technology CN119093482B discloses a method for recovering and utilizing residual pressure. This method calculates residual pressure detection factors by deploying detection points to collect residual pressure data and set the operating state of a synchronous generator. However, it only addresses the pressure data collection of the equipment itself under a single-equipment, single-gas-source mode, and does not establish a quantitative evaluation model for the comprehensive energy quality of the mixed gas after multiple gas sources converge. Therefore, it cannot provide a decision-making basis for the dynamic selection of subsequent power generation equipment. Existing technology CN110233491B discloses a method for generating electricity and connecting to the grid using hydrogen peroxide tail gas residual pressure. This method uses a program main controller to control the intake valve and bypass valve to adjust the speed and achieve automatic synchronization and grid connection. However, it only applies to the grid connection operation of a single generator set. When multiple generator sets are connected to the grid simultaneously or sequentially, each unit independently performs synchronization detection and closing operations, lacking a master-slave coordination mechanism between multiple units. This easily leads to multiple impacts on the power grid and uneven reactive power distribution.

[0004] In summary, existing technologies all focus on single-source residual pressure recovery as the control object, emphasizing the access management of a single gas source, the operation and regulation of a single expander, the grid connection control of a single unit, or the residual pressure data acquisition of a single device. There is no technical solution that can integrate "pre-processing before multi-source convergence - energy quality assessment after convergence - dynamic configuration of generator sets - coordinated grid connection of multiple units" into a whole-chain intelligent control. There is an urgent need to develop a method for centralized recovery of multi-source residual pressure and intelligent grid-connected power generation control. Summary of the Invention

[0005] The purpose of this invention is to provide a method for centralized recovery of residual pressure from multiple gas sources and intelligent grid-connected power generation control to solve the above-mentioned problems in the prior art. The specific technical solution is as follows: A method for centralized recovery of residual pressure from multiple gas sources and intelligent grid-connected power generation control includes the following steps: Multiple residual pressure gas sources are connected to the manifold to form a mixed residual pressure gas source; The mixing parameters of the mixed residual pressure gas source are collected on the manifold, and the comprehensive energy quality index of the manifold is calculated based on the mixing parameters. The comprehensive energy quality index is compared with a preset first quality threshold and a second quality threshold respectively. The first quality threshold is greater than the second quality threshold. When the comprehensive energy quality index is greater than or equal to the first quality threshold, it is determined to be a high energy quality level. When the comprehensive energy quality index is between the first quality threshold and the second quality threshold, it is determined to be a medium energy quality level. When the comprehensive energy quality index is less than the second quality threshold, it is determined to be a low energy quality level. The system obtains the rated power and applicable operating conditions of multiple generator sets in a pre-configured generator set group, and selects matching generator sets to form an online generator set group according to the energy quality level: for high energy quality level, the first generator set with the largest rated power and the third generator set with the fastest adjustment response are selected to form an online generator set group; for medium energy quality level, the second generator set with the middle rated power is selected to form an online generator set group; for low energy quality level, the third generator set with the smallest rated power is selected to form an online generator set group, and a charging preparation command is sent to the energy storage device. The mixed residual pressure gas in the manifold is introduced into the expander connected to the online generator set group to drive the online generator set group to generate electricity.

[0006] As a preferred embodiment of this application, before connecting multiple residual pressure gas sources to the manifold, the method further includes: receiving a multi-source access command; allocating an access channel for each residual pressure gas source according to the multi-source access command; collecting the inlet pressure and inlet temperature values ​​of the corresponding gas source in each access channel; performing graded pretreatment on the gas in each access channel according to the inlet pressure value of each access channel, so that the gas pressure values ​​output by each access channel all fall within a preset manifold pressure range; introducing the pretreated gas from each access channel into the manifold for mixing; the graded pretreatment includes: throttling and depressurization when the inlet pressure value is greater than the upper limit of the manifold pressure range; pressurization and pressure increase when the inlet pressure value is less than the lower limit of the manifold pressure range; and heat exchange and temperature adjustment when the inlet temperature value exceeds a preset temperature range.

[0007] As a preferred embodiment of this application, the collection of the mixing parameters of the mixed residual pressure gas source on the manifold includes: deploying multiple detection points at intervals along the gas flow direction on the manifold, and collecting the manifold pressure value, manifold temperature value, mixed gas flow rate value, and mixed gas component composition data at each detection point; and taking the average value of the same type of parameters at each detection point to obtain the average value of the manifold pressure, the average value of the manifold temperature, the average value of the mixed gas flow rate, and the average value of the concentration of each component.

[0008] As a preferred embodiment of this application, when calculating the comprehensive energy quality index of the manifold based on the manifold parameters, the average pressure of the manifold is divided by a preset reference pressure value to obtain a pressure factor, the average temperature of the manifold is divided by a preset reference temperature value to obtain a temperature factor, the average flow rate of the mixed gas is divided by a preset reference flow rate to obtain a flow factor, a component correction coefficient is calculated based on the concentration of each component and the corresponding work capacity coefficient, and the pressure factor, temperature factor, flow factor and component correction coefficient are weighted and fused to obtain the comprehensive energy quality index.

[0009] As a preferred embodiment of this application, the first quality threshold is 0.75, and the second quality threshold is 0.45; the rated power and applicable operating condition range of the first generator set are higher than those of the second generator set, and the rated power and applicable operating condition range of the second generator set are higher than those of the third generator set.

[0010] As a preferred embodiment of this application, the method further includes: after driving the online generator group to generate electricity, collecting real-time operating parameters from the grid side and the power generation side operating parameters of each generator group; using the real-time operating parameters from the grid side as a reference, selecting a master generator group from the online generator group and performing synchronous adjustment on the master generator group so that the output voltage, frequency, and phase of the master generator group are consistent with those of the grid side, and then controlling the master generator group to connect to the grid; using the operating parameters of the master generator group after grid connection as a reference, sequentially performing follow-up adjustment on each slave generator group so that the output voltage, frequency, and phase of each slave generator group are consistent with those of the master generator group, and then controlling each slave generator group to connect to the grid respectively.

[0011] As a preferred embodiment of this application, when selecting the main generator set from the online generator set group, the speed governor response time constant and the excitation regulator response time constant of each generator set are obtained respectively, and the generator set with the smallest sum of the speed governor response time constant and the excitation regulator response time constant is selected as the main generator set; when performing synchronous regulation on the main generator set, the intake valve opening of the main generator set is adjusted to adjust the power generation frequency, and the excitation current of the main generator set is adjusted to adjust the output voltage, until the absolute value of the difference between the power generation frequency and the grid frequency is less than the first frequency difference threshold and the absolute value of the difference between the output voltage and the grid voltage is less than the first voltage difference threshold.

[0012] As a preferred embodiment of this application, when each slave unit performs follow-up adjustment, the current frequency value and current voltage value of the master unit are used as the adjustment target values ​​of each slave unit. The intake valve opening and excitation current of each slave unit are adjusted respectively until the absolute value of the difference between the generation frequency of each slave unit and the frequency of the master unit is less than the second frequency difference threshold, and the absolute value of the difference between the generation voltage of each slave unit and the voltage of the master unit is less than the second voltage difference threshold; the second frequency difference threshold is less than the first frequency difference threshold, and the second voltage difference threshold is less than the first voltage difference threshold.

[0013] As a preferred embodiment of this application, during the power generation process, the intake pressure values ​​of each access channel are continuously collected and their variation range is calculated. When the variation range of the intake pressure value of a certain access channel exceeds a preset variation threshold, the preprocessing parameters of that access channel are adjusted accordingly. The comprehensive energy quality index of the busbar is continuously calculated and its cross-level changes are monitored. When the comprehensive energy quality index undergoes cross-level changes, generator sets are reselected to form a new online generator set group. During the switching of generator sets, the generator set to be added is connected to the grid under no-load conditions and then its output power is increased in a stepwise manner. At the same time, the already connected generator sets synchronously reduce their output power until the power distribution reaches a new balance.

[0014] This application also provides a multi-gas source residual pressure centralized recovery and intelligent grid-connected power generation control system for implementing the method described above, including a multi-gas source access and graded pretreatment subsystem, a busbar, a quality assessment calculation unit, a generator group and a central control unit. The multi-gas source access and graded pretreatment subsystem includes multiple access channels. Each access channel is equipped with a parameter detection unit and a graded pretreatment unit along the gas flow direction. The parameter detection unit is used to collect the inlet pressure and inlet temperature values ​​of the corresponding gas source. The graded pretreatment unit is used to perform graded pretreatment on the gas in the corresponding access channel according to the inlet pressure value, so that the gas pressure value output by each access channel falls within the preset manifold pressure range. The inlet end of the manifold is connected to the output end of each access channel, and is used to receive and mix the gas output from each access channel to form a mixed residual pressure gas source. The quality assessment calculation unit is signal-connected to the busbar parameter detection component installed on the busbar, and is used to calculate the comprehensive energy quality index of the busbar based on the busbar parameters collected by the busbar parameter detection component, and compare the comprehensive energy quality index with the preset first quality threshold and second quality threshold to determine the current energy quality level of the busbar. The generator set group includes multiple generator sets with different rated power and applicable operating conditions. The central control unit is connected to the quality assessment calculation unit and the generator group signal, and is used to select generators that match the energy quality level from the generator group to form an online generator group according to the energy quality level. The output end of the manifold is connected to the air inlet of the turbine expander corresponding to the online generator set group through a gas supply pipeline. The mixed residual pressure gas is expanded by the turbine expander and then drives the online generator set group to generate electricity.

[0015] As a preferred embodiment of this application, the central control unit has a built-in generator configuration decision logic module. The generator configuration decision logic module is used to execute the following matching strategy according to the energy quality level: when the energy quality level is determined to be high, the first generator set with the largest rated power and the third generator set with the fastest adjustment response are selected to form an online generator set group; when the energy quality level is determined to be medium, the second generator set with the middle rated power is selected to form an online generator set group; when the energy quality level is determined to be low, the third generator set with the smallest rated power is selected to form an online generator set group.

[0016] The beneficial effects of this invention are as follows: 1) This invention configures an independent access channel for each residual pressure gas source. Each channel is equipped with a throttling and pressure-reducing valve, a booster compressor and a heat exchanger. According to the actual pressure and temperature values ​​of each gas source, personalized graded pre-processing is performed so that residual pressure gases from different sources, with different pressure levels and different temperature characteristics can all be merged into a common manifold after closed-loop regulation. This solves the physical contradiction that multiple gas sources cannot be directly merged due to large parameter differences.

[0017] 2) This invention deploys three detection points on the busbar. After fusing the pressure, temperature, flow rate and component data of each detection point, it calculates the pressure factor, temperature factor, flow rate factor and component correction coefficient. The four factors are weighted and fused to obtain a comprehensive energy quality index, which is compared with the first quality threshold and the second quality threshold to determine the quality level. Based on the determination result, a suitable generator set combination is dynamically selected from the first generator set, the second generator set and the third generator set with different rated power and applicable operating conditions, so that the generator set always works in the most suitable operating condition range.

[0018] 3) This invention selects the fastest-responding generator unit from the online generator group as the master unit. Using grid-side parameters as a reference, the master unit is controlled to achieve synchronous grid connection. Each slave unit follows the master unit's grid connection, avoiding multiple impacts on the grid caused by independent grid connection of multiple units. Simultaneously, a sliding window monitors changes in gas source parameters. When the pressure change exceeds 20% of the initial value or the flow rate change exceeds 25% of the initial value, adaptive adjustment is triggered. When the quality changes across levels, the generator unit is gradually switched at a rate of 2% increase or decrease of rated power per step, ensuring that the total output power fluctuation does not exceed ±3% of the target total power.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is an overall flowchart of the multi-gas source residual pressure centralized recovery and intelligent grid-connected power generation control method provided in the embodiments of the present invention.

[0022] Figure 2 This is a flowchart of multi-gas source access and graded preprocessing provided in an embodiment of the present invention.

[0023] Figure 3 This is a flowchart of the energy quality assessment of the busbar provided in an embodiment of the present invention.

[0024] Figure 4 This is a flowchart of the dynamic configuration of generator group provided in an embodiment of the present invention.

[0025] Figure 5 This is a flowchart of multi-unit coordinated grid connection control provided in an embodiment of the present invention.

[0026] Figure 6 This is a flowchart of the multi-gas source fluctuation adaptive adjustment provided in the embodiments of the present invention.

[0027] Figure 7 This is a flowchart of the abnormal operating condition protection provided in the embodiments of the present invention.

[0028] Figure 8 This is an architecture diagram of the multi-gas source residual pressure centralized recovery and intelligent grid-connected power generation control system provided in the embodiments of the present invention. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1 This invention provides a method for centralized recovery of residual pressure from multiple gas sources and intelligent grid-connected power generation control. For example... Figure 1 As shown, the method specifically includes the following steps: S101, Multi-source gas access and staged pretreatment Figure 2 The flowchart for multi-source gas access and staged pretreatment is as follows: Figure 2 As shown, this step aims to perform channel-level identification and hierarchical preprocessing on multiple sources of residual pressure gas with discrete parameters. This ensures that the pressure and temperature of each gas source fall within the allowable range of the main pipe, and after outlet isolation and backflow prevention, a mixed residual pressure gas source with controllable parameters is formed. This provides stable upstream medium conditions for subsequent energy quality assessment and power generation grid connection. The specific implementation is as follows: The system receives multi-source gas access commands, which are automatically issued by the upper-level monitoring system according to the process production plan, or manually triggered by operators through the human-machine interface. After parsing the multi-source gas access commands, the system identifies the number of available residual pressure gas sources and the source attribute identifier of each gas source, assigns an independent access channel to each residual pressure gas source, and establishes a corresponding channel identifier. Each access channel physically consists of an inlet shut-off valve, a parameter detection unit, a staged pretreatment unit, and an outlet isolation valve connected in series, and each unit is signal-connected to the system's main control unit.

[0031] In the parameter detection unit of each access channel, a pressure transmitter embedded in the system acquires the real-time inlet pressure of the gas in the current access channel, a thermocouple temperature sensor acquires the real-time inlet temperature, a vortex flow meter acquires the real-time volumetric flow rate, and an online gas chromatograph acquires the gas composition data. The analog signals acquired by these sensors are amplified and filtered by a signal conditioning circuit, then converted into digital signals by an analog-to-digital converter and uploaded as data frames to the channel controller of the current access channel for buffering and preprocessing. Each sensor has a sampling period of 200ms. The channel controller takes the median value from three consecutive sampling periods and outputs it to suppress the impact of instantaneous fluctuations on control decisions.

[0032] In the graded preprocessing unit, the channel controller compares the collected intake pressure value with the upper and lower limits of the manifold pressure preset in the channel controller register. In this embodiment, the upper limit of the manifold pressure is set to 2.5 MPa, and the lower limit of the manifold pressure is set to 0.8 MPa.

[0033] When the inlet pressure exceeds 2.5 MPa, the channel controller sends an opening adjustment command to the electric actuator of the throttling and pressure-reducing valve located on the currently connected channel. The throttling and pressure-reducing valve employs linear regulation, with an opening adjustment range of 0 to 100%. The channel controller calculates the target opening value based on the ratio of the measured pressure value to 2.5 MPa. The electric actuator receives an analog control signal of 4 mA to 20 mA and adjusts the valve position to the target opening value. During valve operation, the pressure transmitter continuously feeds back the throttled pressure value at 100 ms intervals. The channel controller compares the feedback value with the range of 0.8 MPa to 2.5 MPa. If the feedback value is still higher than 2.5 MPa, the opening is increased; if the feedback value is lower than 0.8 MPa, the opening is decreased, forming a closed-loop regulation until the throttled pressure value stably falls within the 0.8 MPa to 2.5 MPa range and the fluctuation amplitude does not exceed ±5% of the set value.

[0034] When the inlet pressure is less than 0.8 MPa, the channel controller sends start and frequency adjustment commands to the variable frequency drive of the booster compressor located on the currently connected channel. The booster compressor is driven by a variable frequency motor, and the channel controller calculates the target operating frequency based on the ratio of the difference between the measured pressure and 0.8 MPa. After receiving the target frequency command, the variable frequency drive adjusts the motor speed to compress and boost the low-pressure gas. The pressure transmitter at the outlet of the booster compressor continuously feeds back the boosted pressure value at a period of 100 ms. The channel controller compares the feedback value with the range of 0.8 MPa to 2.5 MPa. If the feedback value is still lower than 0.8 MPa, the operating frequency is increased; if the feedback value is higher than 2.5 MPa, the operating frequency is decreased, forming a closed-loop regulation until the boosted pressure value stably falls within the range of 0.8 MPa to 2.5 MPa and the fluctuation range does not exceed ±5% of the set value.

[0035] When the inlet air temperature exceeds the preset temperature range, the channel controller sends an opening command to the refrigerant regulating valve or heat medium regulating valve located in the heat exchanger on the currently connected channel. In this embodiment, the lower limit of the temperature range is set to -20℃, and the upper limit is set to 60℃. The heat exchanger is equipped with a coil-type heat exchange structure, in which the refrigerant or heat medium circulates. When the measured temperature is higher than 60℃, the channel controller sends an opening command to the refrigerant regulating valve to increase the refrigerant circulation flow rate to cool the gas; when the measured temperature is lower than -20℃, the channel controller sends an opening command to the heat medium regulating valve to increase the heat medium circulation flow rate to heat the gas. A thermocouple temperature sensor installed at the heat exchanger outlet continuously feeds back the temperature value after heat exchange at a period of 200ms. The channel controller compares the feedback value with the range of -20℃ to 60℃ to form a closed-loop regulation until the temperature value after heat exchange stably falls within the range of -20℃ to 60℃.

[0036] After the graded pretreatment is completed, each channel controller sends a pretreatment completion status signal, along with the actual pressure, temperature, and flow rates after pretreatment, back to the central control unit. Once the central control unit confirms that all active access channels have completed pretreatment and that all parameters are within acceptable ranges, it issues an opening command to the outlet isolation valve of each access channel. The outlet isolation valve is a pneumatic shut-off valve; upon receiving the opening signal, its valve core actuates under pneumatic pressure, simultaneously introducing gas from each gas source into the shared manifold. The various gas streams mix naturally within the manifold based on their respective pressure differences, forming a mixed residual pressure gas source. A spring-return check valve is installed at the inlet of the manifold. The check valve's opening pressure is 0.05 MPa. When the pressure of an access channel is lower than the manifold pressure, the check valve automatically closes to prevent gas backflow between different access channels or from the manifold to the access channels.

[0037] S102, Busbar Energy Quality Assessment Figure 3 A flowchart for assessing the energy quality of a busbar, such as... Figure 3 As shown, this step aims to calculate the comprehensive energy quality index based on the pressure, temperature, flow rate, and component data after multi-point merging of the busbar, and to classify the quality levels according to thresholds. This quality level code is then reported to the central control unit to provide a basis for dynamic configuration decisions of the generator group. The specific implementation is as follows: Three detection points are deployed at intervals along the gas flow direction on the manifold, located 1m downstream of the manifold inlet, in the middle of the manifold, and 1m upstream of the manifold outlet. Each detection point is equipped with a manifold parameter detection component, which integrates a pressure transmitter, a thermocouple temperature sensor, a vortex flow meter, and an online gas chromatograph. The sensors at each detection point synchronously collect pressure, temperature, flow rate, and gas composition data within the manifold at a sampling period of 500ms. The collected data is uploaded to the quality assessment calculation unit in the form of data frames.

[0038] After receiving the manifold parameters from each detection point, the quality assessment calculation unit first performs data fusion preprocessing. For parameters of the same type, the quality assessment calculation unit arranges the data uploaded from the three detection points into a data sequence, removes data points that deviate from the median by more than 30% as outliers, and then calculates the arithmetic mean of the remaining valid data points. Through this method, the quality assessment calculation unit obtains the average values ​​of the manifold pressure, the manifold temperature, the mixed gas flow rate, and the concentration of each component.

[0039] The quality assessment calculation unit calculates the comprehensive energy quality index of the busbar based on the average value of the above-mentioned busbar parameters.

[0040] The quality assessment calculation unit divides the average manifold pressure by a preset reference pressure value of 2.0 MPa in the register to obtain the pressure factor; divides the average manifold temperature by a preset reference temperature value of 40°C in the register to obtain the temperature factor; and divides the average mixed gas flow rate by a preset reference flow rate value of 10000 Nm³ in the register. 3 / h, to obtain the flow factor.

[0041] The reference pressure value of 2.0 MPa is taken from the upper part of the midpoint of the design pressure range of 0.8 MPa to 2.5 MPa of the manifold, corresponding to the inlet pressure center of the centripetal turboexpander in the rated efficiency range under this gas source scenario; the reference temperature value of 40℃ is taken from the midpoint of the heat exchanger design temperature range of -20℃ to 60℃, which is the weighted average temperature of the component gas under typical industrial residual pressure conditions; the reference flow rate value of 10000 Nm³ / h is taken from the inlet volume flow rate of the first generator set in the rated efficiency range, as a reference for the typical gas supply scale under high energy quality level.

[0042] The quality assessment calculation unit calculates component correction coefficients based on the composition data of the mixed gas. The unit reads the work capacity coefficients of each component gas from the database. These work capacity coefficients are calibrated according to the ratio of the adiabatic index of each component to the adiabatic index of methane, reflecting the theoretical enthalpy drop percentage that each component gas can convert per unit volume within the turbine expander. In this embodiment, the work capacity coefficients for methane are set to 1.00, ethane to 0.85, propane to 0.70, nitrogen to 0.30, and carbon dioxide to 0.20. The unit multiplies the volume fraction of each component by its corresponding work capacity coefficient, sums the products of all components, and obtains the comprehensive component correction coefficient. Both volume fraction and work capacity coefficient are dimensionless quantities; the component correction coefficient obtained after weighted averaging is also dimensionless, consistent with the dimensionless nature of pressure factor, temperature factor, and flow factor.

[0043] Although the four factors characterize different aspects of energy quality—the pressure factor reflects the amount of pressure energy that can be released per unit volume of gas, the flow factor reflects the total amount of usable energy, the temperature factor reflects the contribution of gas enthalpy, and the component correction coefficient reflects the differences in physical properties that do work during gas expansion—they are all normalized into dimensionless indicators. By weighted summation, the overall work potential of the residual pressure gas source can be comprehensively evaluated, providing a unified criterion for the configuration of generator sets.

[0044] The quality assessment calculation unit performs weighted fusion calculations on pressure factor, temperature factor, flow rate factor, and comprehensive component correction coefficient to obtain a comprehensive energy quality index. Among these, the energy source for waste pressure power generation is primarily pressure energy, therefore the weighting coefficient for the pressure factor is set to the highest weight of 0.35. Flow rate reflects the total available energy and is a key factor determining generator set selection and output ceiling; therefore, the weighting coefficient for the flow rate factor is set to the second highest weight of 0.30. The comprehensive component correction coefficient reflects the differences in physical properties of gas expansion, and its impact on energy quality is less than that of pressure and flow rate; therefore, the weighting coefficient for the component correction coefficient is set to 0.20. The actual contribution of the temperature factor to industrial waste pressure gas is relatively limited; the contribution of temperature drop to enthalpy drop during turbine expansion is far less than that of pressure drop; therefore, the weighting coefficient for the temperature factor is set to the lowest weight of 0.15.

[0045] The quality assessment calculation unit compares the calculated comprehensive energy quality index with a first quality threshold and a second quality threshold stored in a register. In this embodiment, the first quality threshold is set to 0.75, and the second quality threshold is set to 0.45. When the comprehensive energy quality index is greater than or equal to 0.75, the quality assessment calculation unit determines that the current busbar is at a high energy quality level, generates the corresponding quality level code 2, and sends it to the central control unit in the form of a data frame; when the comprehensive energy quality index is less than 0.75 but greater than or equal to 0.45, the quality assessment calculation unit determines that the current busbar is at a medium energy quality level, generates the corresponding quality level code 1, and sends it to the central control unit; when the comprehensive energy quality index is less than 0.45, the quality assessment calculation unit determines that the current busbar is at a low energy quality level, generates the corresponding quality level code 0, and sends it to the central control unit.

[0046] S103, Dynamic Configuration of Generator Set Groups Figure 4 A flowchart for dynamic configuration of generator groups, such as Figure 4 As shown, this step aims to have the central control unit select a suitable unit combination and main / auxiliary machine role from the three units (large, medium, and small capacity) based on the current energy quality level code of the busbar, and then feed in mixed residual pressure gas at the initial opening to drive the centripetal turbine expander for power generation, so that the unit capacity matches the energy quality of the gas source. The specific implementation is as follows: The system is pre-configured with a generator set group, consisting of three units: a first generator set, a second generator set, and a third generator set. The rated power of the three generator sets decreases sequentially, and their applicable operating ranges differ. The first generator set is a large-capacity unit, suitable for high energy quality levels; the second generator set is a medium-capacity unit, suitable for medium energy quality levels; and the third generator set is a small-capacity unit, suitable for low energy quality levels. Each generator set is connected to a centrifugal turboexpander as its prime mover. The turboexpander's inlet is connected to the output of the main gas supply pipe via a supply branch pipe. Each supply branch pipe is equipped with an electrically operated regulating valve. These valves receive 4mA to 20mA control signals from the central control unit to regulate the gas flow into each turboexpander. The valve position feedback signals from each electrically operated regulating valve are transmitted back to the central control unit in the form of 4mA to 20mA signals.

[0047] After receiving the quality grade code from the quality assessment and calculation unit, the central control unit makes a generator set configuration decision.

[0048] When the received quality level code is 2, the central control unit determines that the current manifold is in a high energy quality level. For high energy quality levels, the system adopts a coordinated configuration strategy of large-capacity units and regulating small-capacity units. This design is based on the fact that large-capacity units have the highest energy conversion efficiency near their rated power, but their response speed is slower under varying load conditions; small-capacity units have lower rotational inertia and larger adjustment margins, providing faster tracking response to instantaneous fluctuations in gas source pressure. Under high energy quality levels, the total energy of the manifold is sufficient, but in multi-gas source mixed scenarios, even small fluctuations in the gas sources can still cause high-frequency, small-amplitude oscillations in the manifold pressure. If only the large-capacity units operate alone, the unit governor will frequently actuate to track pressure changes, which will shorten the service life of the governor's hydraulic actuator over long-term operation. By configuring a large-capacity generator unit to handle the smooth base load and a small-capacity generator unit to handle the fluctuating regulation component, the large-capacity unit can maintain high efficiency while operating in a stable high-load range. Simultaneously, the rapid response characteristics of the small-capacity unit absorb high-frequency fluctuations. The synergy of these two approaches achieves both high energy efficiency and rapid regulation. Based on this strategy, the central control unit simultaneously sends a 24V DC start signal to the starting relays of both the first and third generator units, initiating a turning start. The central control unit also simultaneously sends a 20% opening control signal to the electric regulating valve on the first gas supply branch pipe and a 15% opening control signal to the electric regulating valve on the third gas supply branch pipe, gradually increasing the speed of both generator units to their rated speed. The central control unit designates the first generator unit as the main output unit and the third generator unit as the auxiliary regulating unit, responsible for rapid tracking and regulation of high-frequency fluctuations.

[0049] When the received quality level code is 1, the central control unit determines that the current busbar is at the medium energy quality level. The central control unit sends a 24V DC start signal only to the start relay of the second generator set, causing the second generator set to begin turning gear start-up. The central control unit sends a 20% opening control signal to the electric regulating valve on the second gas supply branch pipe, causing the second generator set to gradually increase its speed to the rated speed. The central control unit sets the second generator set as the only operating unit in the online generator set group.

[0050] When the received quality level code is 0, the central control unit determines that the current busbar is in a low energy quality level. The central control unit sends a 24V DC start signal to the starting relay of the third generator set, initiating a turning start. The central control unit also sends a 15% opening control signal to the electric regulating valve on the third gas supply branch pipe, gradually increasing the speed of the third generator set to its rated speed. Simultaneously, the central control unit sends a charging preparation command to the energy storage converter, which switches the DC bus to charging mode and sets the upper limit of the charging current. The central control unit then sets the third generator set as an online generator set and the energy storage device as an energy buffer unit.

[0051] After the third generator unit is connected to the grid, the electricity it generates is first supplied to the local load via the grid bus. When the power output of the third generator unit exceeds the real-time demand of the local load, the surplus electricity is rectified by the energy storage converter and stored in the energy storage device. The energy storage converter has a built-in power monitoring module that detects the power flow direction and power magnitude on the grid bus in real time. When a positive power surplus is detected, the charging process is automatically initiated. In this mode, the energy storage device acts as an energy buffer unit to prevent low-quality surplus energy from being directly discharged and wasted because the generator unit cannot absorb it.

[0052] After the selected generator set combination has been confirmed to start and reach its no-load rated speed and operate stably for more than 5 seconds, the main control unit sends an opening command to the main gas supply regulating valve at the output end of the manifold. The main gas supply regulating valve is an electrically adjustable valve that accepts control signals from 4mA to 20mA. The main control unit sends a control signal according to the preset initial opening of 30%, introducing the mixed residual pressure gas in the manifold into the gas supply main. The gas supply main distributes the gas to the turbine expanders corresponding to each online generator set. The gas accelerates and expands in the nozzles of the turbine expander, driving the impeller to rotate and converting the pressure energy and internal energy of the gas into rotational mechanical energy. The output shaft of the turbine expander is connected to the generator rotor through a gear speed increaser and a diaphragm coupling, transmitting the mechanical energy to the generator. The generator converts the mechanical energy into electrical energy and outputs it through the output terminal.

[0053] S104, Multi-unit coordinated grid connection control Figure 5 For a multi-unit coordinated grid connection control flowchart, such as Figure 5 As shown, this step aims to use the grid-side voltage, frequency, and phase as a reference, first having the fastest-responding unit as the master unit complete the initial synchronous grid connection, then having the remaining slave units follow suit with synchronous grid connection based on the master unit's parameters, and finally distributing power according to the rated capacity ratio of each unit and fine-tuning the intake valves to achieve smooth integration of multiple units into the external grid. The specific implementation is as follows: After the generator set reaches its no-load rated speed, the central control unit begins grid connection control. The central control unit receives grid-side data from the grid parameter measurement terminal and generation-side data from the generation parameter measurement units of each generator set in real time.

[0054] The power grid parameter measurement terminal is located on the grid side upstream of the common grid connection point, and integrates a voltage transformer, a frequency meter, and a phase detector. The primary side of the voltage transformer is connected to the grid line, and the secondary side outputs a voltage signal from 0 to 100V to the analog input module of the central control unit. The frequency meter measures the grid frequency by counting the number of zero-crossings of the grid voltage and uploads it to the central control unit in digital form. The phase detector measures the grid phase by comparing the phase difference between the grid voltage zero-crossing moment and the internal reference clock, and uploads it to the central control unit in digital form.

[0055] Each generator set's outgoing terminal is equipped with a power generation parameter measurement unit. Each unit integrates a voltage transformer, a current transformer, a frequency meter, and a phase detector to measure the corresponding generator set's power generation voltage, current, frequency, and phase, respectively. Each measurement unit also integrates a power calculation chip, which calculates active and reactive power based on the instantaneous values ​​of voltage and current, and uploads this data to the central control unit in digital form.

[0056] The central control unit uses grid-side parameters as a reference to coordinate and control the grid connection of each generator unit in the online generator group.

[0057] The central control unit selects the generator set with the fastest response speed from the online generator set group as the main unit. The central control unit compares the governor response time constant and the excitation regulator response time constant of each online generator set, and selects the one with the smallest sum of the governor response time constant and the excitation regulator response time constant as the main unit.

[0058] After selecting the main unit, the central control unit sends a speed regulation command to the main unit's speed governor. The speed governor, based on the command value, adjusts the opening of the main unit's intake valve via a hydraulic actuator, changing the gas flow rate into the turbine expander, thereby adjusting the main unit's speed and power generation frequency. The main unit's intake valve is a linear-stroke electric regulating valve, accepting control signals from 4mA to 20mA, with a response time of 2 seconds from fully closed to fully open. Simultaneously, the central control unit sends a voltage regulation command to the main unit's excitation regulator. The excitation regulator changes the excitation current of the excitation winding by adjusting the firing angle of the thyristor rectifier bridge, thereby adjusting the main unit's output voltage. The output excitation current regulation range of the excitation regulator is 0 to 120% of the rated excitation current.

[0059] During the adjustment process, the central control unit reads the generator frequency and voltage feedback values ​​every 100ms and compares them with the grid frequency and voltage values. When the absolute value of the difference between the generator frequency and the grid frequency is less than 0.2Hz and the absolute value of the difference between the generator voltage and the grid voltage is less than 5% of the grid voltage, the central control unit determines that the frequency and voltage meet the grid connection conditions. The central control unit then reads the generator phase value and the grid phase value. When the absolute value of the difference between the two is less than 5 degrees, the central control unit sends a closing command to the grid-connected circuit breaker of the main unit. The grid-connected circuit breaker is a vacuum circuit breaker. After receiving the closing command, its closing coil is energized, the circuit breaker contacts close, and the main unit completes grid connection. After the closing command is issued, the central control unit checks the feedback signal of the circuit breaker auxiliary contacts within 50ms to confirm successful closing.

[0060] After the main generator set is connected to the grid, the central control unit uses the real-time operating parameters of the connected main generator set as a reference to sequentially control each slave generator set in the online generator group to follow the grid connection. For each slave generator set, the central control unit sends adjustment commands to the speed governor and excitation regulator of that slave generator set, with the adjustment target values ​​set to the current frequency and voltage values ​​of the main generator set. The speed governor and excitation regulator of the slave generator set perform closed-loop adjustment accordingly. The central control unit reads the generator frequency, generator voltage, and generator phase of the slave generator set at a period of 100ms. When the absolute value of the difference between the generator frequency and the main generator frequency of the slave generator set is less than 0.1Hz, the absolute value of the difference between the generator voltage and the main generator voltage is less than 3% of the main generator voltage, and the absolute value of the difference between the generator phase and the main generator phase is less than 3 degrees, the central control unit sends a closing command to the grid connection circuit breaker of that slave generator set, and the slave generator set completes grid connection. All slave generator sets are connected to the grid in this manner.

[0061] After all generator sets are connected to the grid, the central control unit switches to power distribution control mode. The central control unit reads the instantaneous output power value of each online generator set every 200ms. The central control unit calculates the total rated capacity of the online generator sets and calculates the percentage of each unit's rated capacity relative to the total rated capacity as its power distribution coefficient. The central control unit multiplies the current total load demand by the power distribution coefficient of each unit to obtain the target output power value for each unit. The central control unit compares the target output power value of each unit with the actual output power value. When the deviation between the actual value and the target value exceeds 5% of the target value, the central control unit issues an adjustment command to the governor of the corresponding unit, fine-tuning the intake valve opening to bring the output power closer to the target value, until the ratio of the actual output power of each unit matches the ratio of its rated capacity and the deviation is less than 5%.

[0062] It should be further explained that the design basis for the above host group selection and frequency difference threshold setting is as follows: Firstly, the selection criteria for the main generator unit and the optimal operating condition matching for unit configuration decisions are two relatively independent optimization dimensions. The main generator unit undertakes the initial synchronization and grid connection task, and its core objective is to shorten the synchronization capture time and minimize the impact on the grid. Therefore, the unit with the smallest sum of response time constants is selected. The role of the main output generator unit is jointly determined by configuration decisions and power allocation logic. The unit with the optimal capacity or efficiency assumes the main output after grid connection through power allocation. The two roles can be separated, which ensures both the speed and safety of the initial connection process and the high efficiency of steady-state operation. Seamless role switching is achieved through smooth transition logic. The main generator unit that connects to the grid first provides a unified synchronization tracking benchmark for subsequent slave units, avoiding governor oscillations caused by multiple slave units simultaneously chasing dynamic fluctuations on the grid side, effectively reducing the complexity of synchronization capture and the risk of grid connection failure.

[0063] Secondly, the frequency difference threshold setting between the master unit and the slave unit conforms to the general logic of power system grid connection control. The master unit is directly connected to the public power grid, which is an infinitely large system with extremely high inertia. The grid connection impact of a single small-to-medium capacity residual pressure generator can be completely absorbed by the grid. Therefore, setting a frequency difference threshold of 0.2Hz can improve the start-up and grid connection efficiency while ensuring grid safety. When the slave unit is connected to the grid, it is connected to the already connected master unit. The two are connected in parallel to the same bus and have strong electrical coupling. If the frequency difference is too large, a significant circulating current impact will be generated at the moment of grid connection. At the same time, it will cause mechanical damage to the impeller, coupling and other components of the centripetal turboexpander. Therefore, the frequency difference threshold of the slave unit is tightened to 0.1Hz. The stricter grid connection requirements can effectively ensure the stability of multi-unit parallel operation. The threshold setting logic is self-consistent and without contradiction.

[0064] S105, Multi-source fluctuation adaptive adjustment Figure 6 The flowchart for adaptive adjustment of multi-gas source fluctuations is as follows: Figure 6 As shown, this step aims to continuously monitor significant changes in the original residual pressure parameters through a sliding window in each access channel, and adjust the pretreatment actuator of that channel accordingly or disconnect the channel in case of gas source failure; simultaneously, the quality assessment unit periodically recalculates the energy quality indicators, triggering dynamic reconfiguration of the generator group and smoothing the transition when cross-level changes occur, thus suppressing fluctuations in total output power. The specific implementation is as follows: During power generation, the system continuously monitors fluctuations and adaptively adjusts. Each access channel's channel controller continuously collects the raw residual pressure parameters of its channel every 2 seconds and temporarily stores them in a buffer. Each channel controller maintains a sliding window with a length of 10 sampling periods. Whenever new sampled data arrives, the channel controller compares the latest data with the oldest data within the window, calculating the magnitude and rate of change of each parameter from its initial value to its current value within the window period.

[0065] When the intake pressure value of a certain channel changes by more than 20% from its initial value to its current value within a certain window period, or when the flow rate value of a certain channel changes by more than 25% from its initial value to its current value within a certain window period, the channel controller determines that the original residual pressure parameter of the gas source has changed significantly. The channel controller reports the significant change event to the central control unit. The reported data includes the channel identifier, the type of parameter change, the parameter value before the change, and the parameter value after the change.

[0066] After receiving a significant change event, the central control unit makes corresponding adaptive adjustments based on the type and magnitude of the change in the reported data.

[0067] When the change type is a significant increase in intake pressure, the central control unit sends a pressure regulation command to the channel controller of that channel. The channel controller increases the opening of the throttling and pressure-reducing valve to increase the pressure reduction. The new opening value is calculated based on the product of the pressure increase ratio and the regulation coefficient. The channel controller sends a new opening control signal to the electric actuator of the throttling and pressure-reducing valve, and the pressure transmitter provides feedback to confirm that the pressure value after the pressure reduction falls within the range of 0.8MPa to 2.5MPa.

[0068] When the change type is a significant decrease in intake pressure, the channel controller first determines whether the current operating frequency of the booster compressor has reached 95% of the rated frequency. If the current operating frequency is lower than 95% of the rated frequency, the channel controller increases the operating frequency of the booster compressor to increase the boost pressure. The new frequency value is calculated as the product of the pressure reduction ratio and the adjustment coefficient. After receiving the new frequency command, the frequency converter increases the motor speed and confirms through feedback from the pressure transmitter that the boosted pressure value falls within the range of 0.8MPa to 2.5MPa. If the current operating frequency has reached 95% of the rated frequency and the measured intake pressure is still lower than 0.6MPa, the channel controller determines that the air source no longer meets the effective access conditions and sends an air source failure report to the central control unit. After receiving the air source failure report, the central control unit simultaneously issues a shut-off command to the inlet shut-off valve and the outlet isolation valve of the channel. Both the inlet shut-off valve and the outlet isolation valve are pneumatic shut-off valves. After receiving the shut-off signal, the valve core closes quickly under the action of the spring return force, completely disconnecting the air source from the manifold. The central control unit simultaneously sends a gas source cutoff prompt to the human-machine interface and displays the cutoff channel number in red flashing mode on the interface.

[0069] When the change type is a significant change in inlet air temperature, the main control unit sends a temperature adjustment command to the channel controller of that channel. The channel controller then adjusts the refrigerant regulating valve or heat medium regulating valve of the heat exchanger accordingly to increase or decrease the heat exchange capacity in order to maintain the outlet temperature within the range of -20℃ to 60℃.

[0070] The quality assessment calculation unit continuously calculates the comprehensive energy quality index of the busbar every 2 seconds, comparing the new value obtained in each calculation with the old value obtained in the previous cycle, and simultaneously comparing the new value with the first quality threshold of 0.75 and the second quality threshold of 0.45 stored in the register. When the new value changes from greater than or equal to 0.75 to less than 0.75 but greater than or equal to 0.45, or from less than 0.75 but greater than or equal to 0.45 to greater than or equal to 0.75, or from less than 0.45 to greater than or equal to 0.45, the quality assessment calculation unit determines that a cross-level change in quality level has occurred and sends a quality level change event to the central control unit. The event data includes the quality level code before the change and the quality level code after the change.

[0071] Upon receiving a quality level change event, the central control unit re-performs the generator configuration decision in S103 according to the changed quality level code to determine the generator set combination adapted to the new energy quality level. During the switching process of the generator set combination, the central control unit performs smooth transition control.

[0072] When an additional generator unit needs to be added, the central control unit first sends a start command to the generator unit to be added. After the unit reaches its no-load rated speed, the central control unit uses the power generation parameters of the currently grid-connected units as a benchmark, and adjusts the power generation frequency, voltage, and phase of the generator unit to be added to match those of the already grid-connected units through the speed governor and excitation regulator. After adjustment, the central control unit sends a closing command to the grid-connected circuit breaker of the generator unit to be added, and the generator unit to be added completes grid connection under no-load conditions. After successful grid connection, the central control unit reads the output power of the generator unit to be added at a period of 200ms and sends a power increase command to its speed governor. The intake valve is gradually opened at a rate of 2% of the rated power per step, so that the output power increases slowly. The time interval between each step is set to 200ms. If, during the stepping process, the quality assessment calculation unit detects a significant change in the gas source parameters during the transition period, the central control unit immediately pauses the current stepping operation, rereads the current quality level code, and re-executes the unit configuration decision according to the latest quality level. The corresponding smooth transition control process is only initiated after the new decision is determined. When the ratio of the actual output power of each online generator unit to its rated capacity is consistent and the absolute value of the deviation is less than 5%, the central control unit determines that a new power distribution balance has been achieved and stops the stepping adjustment.

[0073] When a generator unit needs to be shut down, the central control unit first issues a load reduction command to the unit to be shut down, gradually closing its intake valve at a rate of 2% reduction in rated power per step, causing its output power to decrease slowly. Simultaneously, the central control unit issues power coordination commands to other online generator units, synchronously increasing their output according to the power distribution coefficient of each unit, with the rate of increase matching the rate of power reduction of the unit to be shut down, to compensate for the power reduction. Throughout the transition process, the central control unit monitors the total output power at the grid connection point at a period of 100ms, ensuring that the fluctuation range of the total output power does not exceed ±3% of the target total power. Once the output power of the generator unit to be shut down drops below 2% of its rated power, the central control unit issues a trip command to the unit's grid connection circuit breaker to disconnect it from the grid, and then issues a full-close command to the unit's intake valve to stop the unit's operation.

[0074] S106, Abnormal Operating Condition Protection Figure 7 The flowchart for abnormal operating condition protection is as follows: Figure 7As shown, this step aims to have the fault diagnosis module compare the real-time monitoring parameters of each stage with safety thresholds, implement different response strategies for various abnormal operating conditions, and issue alarms through the human-machine interface to ensure the safety of the system and critical loads. The specific implementation is as follows: During power generation, the system continuously monitors and protects against abnormal operating conditions. Each status monitoring sensor collects the operating status parameters of each component with a sampling period of 200ms and uploads them in real time to the fault diagnosis module of the central control unit in the form of data frames. The fault diagnosis module is equipped with multiple comparators. The first input of each comparator receives the corresponding real-time status parameter value, and the second input is connected to the corresponding safety threshold register.

[0075] The fault diagnosis module compares the real-time pressure values ​​uploaded by the pressure transmitters of each access channel with the pressure safety threshold of 4.0 MPa stored in the safety threshold register. When the real-time pressure value of a certain access channel exceeds 4.0 MPa, the fault diagnosis module determines that the access channel has an overpressure risk and sends a channel overpressure fault event to the central control unit. After receiving the channel overpressure fault event, the central control unit simultaneously sends a 24V DC shutdown signal to the inlet shut-off valve and the outlet isolation valve of that channel. Both the inlet shut-off valve and the outlet isolation valve are single-acting pneumatic shut-off valves. Under normal operation, the gas source pressure keeps the valve open. When the shutdown signal is received, the solenoid valve de-energizes and releases pressure, and the valve core quickly resets to the closed position under the drive of the spring force, cutting off the connection between the channel and the gas source and the manifold. After the shutdown signal is sent, the central control unit confirms that the valve is completely closed within 200ms through the valve position feedback contact. At the same time, the central control unit sends an opening signal to the bypass vent valve of that channel. After the bypass vent valve opens, the residual gas in the channel is switched to the safe discharge pipeline. The safety emission pipeline is connected to the plant's venting or flare system to safely combust the emitted gases.

[0076] The fault diagnosis module compares the real-time pressure value transmitted from the pressure transmitter on the manifold with the manifold pressure safety threshold of 3.0 MPa stored in the safety threshold register. When the real-time pressure value of the manifold exceeds 3.0 MPa, the fault diagnosis module determines that there is a risk of pressure buildup in the manifold and sends a manifold overpressure fault event to the central control unit. Upon receiving the manifold overpressure fault event, the central control unit sends a 24V DC opening signal to the safety relief valve installed on the manifold. The safety relief valve is a pilot-operated safety valve; upon receiving the opening signal, its pilot solenoid valve actuates, and the main valve disc opens rapidly under the pressure of the medium, releasing the gas in the manifold to the vent pipe. Simultaneously, the central control unit sends a pressure-maintaining shut-off command to the outlet isolation valves of each access channel, closing the outlet isolation valves to prevent further gas from entering the manifold. The main control unit reads the main pipe pressure value every 100ms. When the main pipe pressure value drops below 2.0MPa, the main control unit sends a shut-off signal to the safety relief valve. The pilot solenoid valve of the safety relief valve is reset, and the main valve disc returns to its seat and closes under the action of the main spring force.

[0077] The fault diagnosis module compares the vibration amplitude signals from the vibration sensors built into each generator set with the vibration amplitude safety threshold of 12 mm / s stored in the safety threshold register; it compares the temperature values ​​uploaded by the bearing temperature sensors of each generator set with the bearing temperature safety threshold of 95℃ stored in the safety threshold register; and it compares the speed values ​​uploaded by the speed sensors of each generator set with the speed safety threshold stored in the safety threshold register. When any monitored parameter of a generator set exceeds the corresponding safety threshold, the fault diagnosis module determines that the generator set has malfunctioned and sends a generator set fault event to the central control unit. The event data includes the faulty generator set number and the fault parameter type.

[0078] Upon receiving a generator set fault event, the central control unit immediately sends a trip command to the grid-connected circuit breaker of the faulty generator set. After the trip coil of the circuit breaker is energized, the circuit breaker contacts open, and the faulty generator set is disconnected from the grid. Simultaneously, the central control unit sends a full-close command to the intake valve of the faulty generator set, cutting off the gas supply to the corresponding turbine expander. After these operations are completed, the central control unit selects a generator set from the generator set group that is in standby mode and whose capacity matches the current energy quality level, based on the current comprehensive energy quality level of the busbar. The central control unit sends a start command to the standby generator set, which completes the start-up and grid connection operations according to the grid connection control process in S104, taking over the power generation task of the faulty generator set. After the standby generator set completes grid connection and operates stably for 5 seconds, the central control unit displays a fault replacement completion message on the human-machine interface. After the faulty unit is confirmed to be normal after inspection, the operator can manually input the recovery confirmation command through the human-machine interface to switch the unit to standby status. When a unit becomes available or needs to be added due to a change in quality level, the central control unit will call it back according to the normal startup procedure.

[0079] The fault diagnosis module compares the grid frequency value uploaded by the grid parameter measurement terminal with the lower limit of the normal grid frequency range (49.5Hz) and the upper limit (50.5Hz) stored in the safety threshold register. When the grid frequency value is lower than 49.5Hz or higher than 50.5Hz, or when the voltage value uploaded by the grid parameter measurement terminal is lower than 85% of the rated voltage, the fault diagnosis module determines that an anomaly has occurred on the grid side and sends a grid anomaly event to the central control unit. Upon receiving the grid anomaly event, the central control unit immediately issues a trip command to the grid-connected circuit breakers of all online generator sets simultaneously. Each grid-connected circuit breaker operates simultaneously, disconnecting all generator sets from the external grid. The central control unit then switches to off-grid operation mode. In off-grid operation mode, the central control unit selects the generator set with the largest capacity from the online generator set group as the off-grid reference unit. Using the output voltage and frequency of this unit as a reference, the central control unit maintains the voltage of the local microgrid within ±5% of the rated value and the frequency within 50Hz ±0.5Hz through the speed governor and excitation regulator of this unit. The central control unit continuously supplies power to the preset critical load power supply lines through the local load switch.

[0080] The central control unit simultaneously checks whether the grid parameters have returned to normal at a 1-second interval. The fault diagnosis module continuously monitors the grid frequency and voltage at a 1-second interval. When the grid frequency remains stable within the range of 49.5Hz to 50.5Hz for 30 seconds and the voltage recovers to more than 90% of the rated voltage, the fault diagnosis module determines that the external grid has met the conditions for grid reconnection and sends a grid reconnection ready signal to the central control unit. The central control unit maintains the current online generator configuration unchanged. Upon receiving the grid reconnection ready signal, it automatically issues a command to the off-grid reference unit to re-execute the grid connection control process in step S104 based on the current external grid parameters, reconnecting the off-grid reference unit to the external grid. After the off-grid reference unit successfully reconnects, the central control unit uses the real-time parameters of that unit as a reference to sequentially reconnect other online generator units to the external grid. If, during the grid restoration process, grid parameters are detected to be outside the normal range again, the fault diagnosis module immediately sends a grid anomaly event to the central control unit. The central control unit then interrupts the grid restoration process, disconnects all grid-connected units again, and maintains off-grid operation until grid parameters stabilize again. After all units are restored to grid connection, the central control unit displays a grid restoration completion notification on the human-machine interface.

[0081] Example 2 This invention also provides a multi-source residual pressure centralized recovery and intelligent grid-connected power generation control system, implemented using the method of Embodiment 1. For example... Figure 8 As shown, the system includes a multi-gas source access and graded pretreatment subsystem, a busbar, a quality assessment and calculation unit, a generator set group, a power grid parameter measurement terminal, a central control unit, an energy storage device, and a human-machine interface.

[0082] The multi-source gas access and staged pretreatment subsystem includes multiple access channels, the number of which matches the number of available residual pressure gas sources. Each access channel is equipped with an inlet shut-off valve, a parameter detection unit, a staged pretreatment unit, and an outlet isolation valve, connected in series along the gas flow direction. The inlet shut-off valve is a pneumatic single-acting shut-off valve, which is kept open by the gas source pressure during normal operation. When a shut-off signal is received, the solenoid valve depressurizes, and the valve core closes quickly under the action of spring force, which can quickly cut off the connection between the channel and the gas source under abnormal operating conditions.

[0083] The parameter detection unit integrates a pressure transmitter, a thermocouple temperature sensor, a vortex flow meter, and an online gas chromatograph. The pressure transmitter is a capacitive pressure transmitter with a range of 0 MPa to 6 MPa, outputting a 4 mA to 20 mA analog signal. The thermocouple temperature sensor is a type K armored thermocouple with a measurement range of -50℃ to 150℃, and its output is converted to a 4 mA to 20 mA analog signal via the temperature transmitter. The vortex flow meter is a stress-type vortex flow meter with a range ratio of 20:1, outputting a 4 mA to 20 mA analog signal. The online gas chromatograph is a miniaturized thermal conductivity detector-type gas chromatograph with an analysis cycle of 60 s, outputting volume fraction data of each component via an RS485 communication interface. The signal output terminals of all the above sensors are electrically connected to the signal input terminals of the channel controller. Signal transmission uses shielded cables and isolators to prevent electromagnetic interference.

[0084] The staged pretreatment unit consists of a throttling and pressure-reducing valve, a booster compressor, and a heat exchanger, connected in series along the gas flow direction. The throttling and pressure-reducing valve is a cage-type sleeve regulating valve with a nominal diameter of DN100. Its electric actuator receives control signals from 4mA to 20mA, and its full stroke time is 2 seconds. The booster compressor is a reciprocating piston compressor with a rated discharge pressure of 2.5MPa. It is driven by a variable frequency motor, whose control signal input receives frequency commands from 4mA to 20mA, and whose output frequency adjustment range is 20Hz to 50Hz. The heat exchanger is a shell-and-tube structure, with industrial gas flowing through the shell side and refrigerant or heat transfer medium flowing through the tube side. An electric regulating valve is installed at the tube-side inlet. The control signal inputs of the electric actuator of the throttling and pressure-reducing valve, the frequency converter of the booster compressor, and the electric regulating valve of the heat exchanger are electrically connected to the analog output channel of the channel controller.

[0085] The outlet isolation valve is a pneumatic single-acting shut-off valve with the same structure as the inlet shut-off valve. The output of the outlet isolation valve of each access channel is connected in parallel to the inlet of the common manifold via a manifold branch. Each access channel is equipped with a spring-return check valve at the connection point to the manifold. The check valve disc opens when the forward pressure difference is greater than 0.05 MPa and automatically closes when the reverse pressure difference is greater than 0.01 MPa, preventing gas backflow between different access channels and from the manifold to the access channels.

[0086] The manifold is located downstream of all access channels, with a nominal diameter of DN300 and a design pressure of 4.0 MPa. Three detection point mounting bases are spaced along the gas flow direction on the manifold wall: 1m downstream of the manifold inlet, 1m in the middle of the manifold, and 1m upstream of the manifold outlet. Each mounting base is fixed with a manifold parameter detection assembly, which integrates a pressure transmitter, a thermocouple temperature sensor, a vortex flow meter, and an online gas chromatograph. The specifications and models of each sensor are the same as those in the access channel parameter detection unit, and the signal output terminals of each sensor are electrically connected to the signal input terminal of the quality assessment calculation unit. The manifold is also equipped with a pilot-operated safety relief valve. The nominal diameter of the safety relief valve is DN150, and the set pressure is 3.0MPa. The control signal input terminal of the pilot solenoid valve of the safety relief valve is electrically connected to the digital output channel of the main control unit, and performs emergency pressure relief when the manifold is overpressured. The output terminal of the manifold is equipped with a main gas supply regulating valve. The main gas supply regulating valve is an electrically adjustable butterfly valve with a nominal diameter of DN250. It receives 4mA to 20mA control signals and regulates the total gas supply flow to the downstream power generation equipment.

[0087] The analog input channel of the quality assessment calculation unit is connected to the signal output terminals of the pressure and temperature transmitters at each detection point on the manifold via shielded cables, receiving 4mA to 20mA current signals. The communication interface of the quality assessment calculation unit is connected to the communication ports of the vortex flowmeters and online gas chromatographs at each detection point via an RS485 bus, reading flow and component data according to the Modbus RTU protocol. The quality assessment calculation unit has built-in data preprocessing algorithm modules, weighted calculation algorithm modules, and grade determination algorithm modules. The data preprocessing algorithm module performs outlier removal and RMS averaging on similar parameters at each detection point, outputting average pressure, average temperature, average flow rate, and average concentration of each component. The weighted calculation algorithm module performs weighted fusion calculation based on the preprocessed average pressure, average temperature, average flow rate, and component correction coefficients to obtain the comprehensive energy quality index. The grade determination algorithm module compares the comprehensive energy quality index with the first and second quality thresholds stored in a register to determine the current energy quality level of the manifold. The digital output port of the quality assessment calculation unit is connected to the digital input port of the main control unit via hardwiring, and the judgment result is sent in binary form with quality level coding.

[0088] The generator set group consists of three units: the first generator set, the second generator set, and the third generator set. The rated power of the three generator sets decreases sequentially, and their applicable operating conditions differ. The first generator set is a large-capacity unit, suitable for high energy quality levels; the second generator set is a medium-capacity unit, suitable for medium energy quality levels; and the third generator set is a small-capacity unit, suitable for low energy quality levels. Each generator set is connected to a centrifugal turboexpander as its prime mover. The turboexpander's air inlet is connected to the main air supply pipe downstream of the main air supply regulating valve of the manifold via a supply branch pipe. Each supply branch pipe is equipped with an electrically operated regulating valve, a single-seat regulating valve driven by a linear electric actuator, receiving 4mA to 20mA control signals to control the gas flow entering each turboexpander.

[0089] Each generator set is equipped with a permanent magnet speed sensor on its rotor. The signal output terminal of the speed sensor is connected to the speed signal input terminal of the central control unit to measure the real-time speed of the generator set. Each generator set is equipped with a digital speed governor and a digital excitation regulator. The speed governor is an electro-hydraulic conversion speed governor. Its control signal input terminal receives a 4mA to 20mA speed command signal from the central control unit. The hydraulic actuator of the speed governor is connected to the intake regulating valve of the turbine expander. By changing the opening of the intake regulating valve, the flow rate of gas entering the turbine expander is controlled to regulate the generator set speed and power generation frequency. The excitation regulator is a self-excited static excitation system. Its control signal input terminal receives a 4mA to 20mA voltage command signal from the central control unit. The excitation regulator regulates the excitation current of the excitation winding by controlling the firing angle of the thyristor rectifier bridge to regulate the output voltage of the generator set. Each generator set is equipped with a power generation parameter measurement unit at its output terminal. This unit integrates a voltage transformer, current transformer, frequency meter, phase detector, and power calculation chip to measure the power generation voltage, current, frequency, phase, and active power. All measurement data are transmitted digitally to the central control unit via a communication bus. Each generator set's output terminal is also connected to a common grid connection point via an independent vacuum grid-connected circuit breaker and grid-connected bus. The control terminals of the closing and opening coils of the grid-connected circuit breaker are connected to the digital output channels of the central control unit. The circuit breaker is equipped with a synchronizing detection device. When the synchronizing detection device detects that the voltage difference, frequency difference, and phase difference between the generator side and the grid side all meet the set values, it sends a closing permission signal to the central control unit.

[0090] The power grid parameter measurement terminal is located on the grid side upstream of the common grid connection point and integrates a voltage transformer, a frequency meter, and a phase detector. The primary side of the voltage transformer is connected to the grid line, and the secondary side outputs a 0-100V AC voltage signal to the analog input module of the central control unit. The frequency meter tracks the grid voltage frequency through a phase-locked loop circuit and uploads it to the central control unit in digital form via a communication interface. The phase detector detects the zero-crossing moment of the grid voltage through a zero-crossing comparator circuit and uploads it to the central control unit in digital form. The common grid connection point is connected to the external power grid through a step-up or step-down transformer.

[0091] The central control unit is implemented using a redundant programmable logic controller (PLC), consisting of a main controller and a backup controller. The main and backup controllers are connected via a synchronous fiber optic cable, and the backup controller automatically takes over within 50ms in the event of a main controller failure. The central control unit integrates data storage, communication interface, analog input, analog output, digital input, and digital output modules. The analog input modules are connected via shielded cables to the outputs of the quality assessment calculation unit, the status feedback terminals of each channel controller, the outputs of each power generation parameter measurement unit, the outputs of the grid parameter measurement terminal, and the outputs of each status monitoring sensor. The digital output modules are connected via control cables to the command input terminals of each channel controller, the control terminals of each gas supply regulating valve, the control terminals of each grid-connected circuit breaker, the command input terminals of each speed governor, the command input terminals of each excitation regulator, and the control terminals of the safety relief valve. The central control unit also integrates unit configuration decision logic, synchronous grid-connected control logic, power distribution logic, fluctuation adaptive adjustment logic, and fault diagnosis and protection logic modules.

[0092] The generator configuration decision logic module selects a generator set combination that matches the current energy quality level from the generator set group based on the received busbar energy quality level code, and sends a start command to the selected generator set through the digital output module and an opening command to the corresponding gas supply regulating valve through the analog output module.

[0093] The synchronous grid-connection control logic module uses grid-side operating parameters as a reference to sequentially control each selected generator set to complete the grid connection operation. Internally, the synchronous grid-connection control logic module includes a master generator set selection submodule and a slave generator set following submodule. The master generator set selection submodule compares the sum of the governor response time constant and the excitation regulator response time constant of each generator set in the online generator set group, selects the generator set with the fastest response speed as the master generator set, and controls it to complete the initial grid connection. The slave generator set following submodule uses the operating parameters of the already connected master generator set as a reference to sequentially control each slave generator set to complete the follow-up grid connection.

[0094] After all online generator sets have been connected to the grid, the power distribution logic module calculates the power distribution coefficient based on the rated capacity ratio of each generator set, and sends adjustment commands to the speed governor and excitation regulator of each generator set to make the ratio of the actual output power of each generator set equal to the ratio of its rated capacity.

[0095] The fluctuation adaptive adjustment logic module triggers the reconfiguration of preprocessing parameters for the access channels and the dynamic reconfiguration of the generator group based on significant changes in raw residual pressure parameters reported by each access channel and changes in quality level reported by the quality assessment calculation unit. Internally, the fluctuation adaptive adjustment logic module includes a smooth transition control submodule, used to perform gradual power transfer control during generator additions or shutdowns, ensuring that the fluctuation range of the total output power does not exceed ±3% of the target total power.

[0096] The fault diagnosis and protection logic module contains multiple comparators. The first input of each comparator is connected to the signal output of its corresponding condition monitoring sensor, and the second input is connected to its corresponding safety threshold register. The output of each comparator is connected to the input of the logic judgment unit. The safety threshold register stores thresholds including the access channel pressure safety threshold, the main pipe pressure safety threshold, the vibration amplitude safety threshold, the bearing temperature safety threshold, the rotational speed safety threshold, the lower and upper limits of the normal range for the power grid frequency, and the lower limit of the normal range for the power grid voltage. The logic judgment unit determines the anomaly type based on the output of each comparator and, according to the anomaly type, retrieves the corresponding protection operation instruction from the protection strategy library stored in the data storage module, outputting it to the corresponding actuator via the digital output module.

[0097] The energy storage device is a lithium iron phosphate battery energy storage system with a rated capacity of 500kWh, connected to the grid bus via an energy storage converter. The energy storage converter is a bidirectional DC-AC converter, with its control signal input connected to the analog output channel of the main control unit. When receiving a charging command, the energy storage converter converts AC bus power into DC power to store in the battery pack; when receiving a discharging command, it converts the DC power from the battery pack into AC power to feed back to the grid bus. When the busbar's energy quality level is low, the energy storage device receives and stores residual energy that cannot be absorbed by the generator set; when the busbar's energy quality level improves, it inverts the stored energy back to the grid bus via the energy storage converter.

[0098] The human-machine interface (HMI) is an industrial touchscreen all-in-one machine that communicates with the central control unit via industrial Ethernet. The HMI displays real-time parameter values ​​and status icons for each access channel, real-time parameter values ​​and energy quality level indicators for the busbar, operating status icons and output power values ​​for each generator set, grid-side parameter values, and a list of fault alarm information. The HMI's operation screen includes start, stop, emergency stop buttons, and parameter setting input boxes for receiving control commands and modifying settings issued by the operator.

[0099] The signal connections between the various components of the above system adopt a redundant communication architecture. The main communication link is an industrial Ethernet network following the TCP / IP protocol, and the backup communication link is an RS485 fieldbus following the Modbus RTU protocol. In the event of a single communication link failure, the system can automatically switch to the backup link within 200ms to continue operation. The power supply for each sensor and actuator is redundantly provided by two independent uninterruptible power supply systems. The battery backup time of each uninterruptible power supply is no less than 30 minutes. When the main power supply fails, the system can still complete all protection operations and maintain normal monitoring operation for at least 15 minutes.

[0100] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for centralized recovery of residual pressure from multiple gas sources and intelligent grid-connected power generation control, characterized in that, Includes the following steps: Multiple residual pressure gas sources are connected to the manifold to form a mixed residual pressure gas source; The mixing parameters of the mixed residual pressure gas source are collected on the manifold, and the comprehensive energy quality index of the manifold is calculated based on the mixing parameters. The comprehensive energy quality index is compared with a preset first quality threshold and a second quality threshold respectively. The first quality threshold is greater than the second quality threshold. When the comprehensive energy quality index is greater than or equal to the first quality threshold, it is determined to be a high energy quality level. When the comprehensive energy quality index is between the first quality threshold and the second quality threshold, it is determined to be a medium energy quality level. When the comprehensive energy quality index is less than the second quality threshold, it is determined to be a low energy quality level. Obtain the rated power and applicable operating conditions of multiple generator sets in the pre-configured generator set group, and select matching generator sets to form an online generator set group according to the energy quality level: when the energy quality level is high, select the first generator set with the largest rated power and the third generator set with the fastest adjustment response to form an online generator set group. When the energy quality level is medium, the second generator set with the middle rated power is selected to form an online generator set group; when the energy quality level is low, the third generator set with the smallest rated power is selected to form an online generator set group, and a charging preparation command is sent to the energy storage device. The mixed residual pressure gas in the manifold is introduced into the expander connected to the online generator set group to drive the online generator set group to generate electricity.

2. The method according to claim 1, characterized in that, Before connecting multiple residual pressure gas sources to the manifold, the process further includes: receiving a multi-source access command; allocating an access channel for each residual pressure gas source according to the multi-source access command; collecting the inlet pressure and inlet temperature values ​​of the corresponding gas source in each access channel; performing graded pre-processing on the gas in each access channel according to the inlet pressure value of each access channel, so that the gas pressure values ​​output by each access channel all fall within a preset manifold pressure range; introducing the graded pre-processed gas from each access channel into the manifold for mixing; the graded pre-processing includes: throttling and depressurization when the inlet pressure value is greater than the upper limit of the manifold pressure range; pressurization and pressure increase when the inlet pressure value is less than the lower limit of the manifold pressure range; and heat exchange and temperature adjustment when the inlet temperature value exceeds a preset temperature range.

3. The method according to claim 1, characterized in that, The process of collecting the mixing parameters of the mixed residual pressure gas source on the manifold includes: deploying multiple detection points at intervals along the gas flow direction on the manifold, and collecting the manifold pressure value, manifold temperature value, mixed gas flow rate value, and mixed gas component composition data at each detection point; and taking the average value of the same type of parameters at each detection point to obtain the average value of the manifold pressure, the average value of the manifold temperature, the average value of the mixed gas flow rate, and the average value of the concentration of each component.

4. The method according to claim 3, characterized in that, When calculating the comprehensive energy quality index of the manifold based on the manifold parameters, the average pressure of the manifold is divided by a preset reference pressure value to obtain a pressure factor, the average temperature of the manifold is divided by a preset reference temperature value to obtain a temperature factor, the average flow rate of the mixed gas is divided by a preset reference flow rate to obtain a flow factor, a component correction coefficient is calculated based on the concentration of each component and the corresponding work capacity coefficient, and the pressure factor, temperature factor, flow factor and component correction coefficient are weighted and fused to obtain the comprehensive energy quality index.

5. The method according to claim 1, characterized in that, The first quality threshold is 0.75, and the second quality threshold is 0.

45.

6. The method according to claim 1, characterized in that, The rated power and applicable operating range of the first generator set are higher than those of the second generator set, and the rated power and applicable operating range of the second generator set are higher than those of the third generator set.

7. The method according to claim 1, characterized in that, Also includes: After the online generator set group generates electricity, the real-time operating parameters of the grid side and the power generation side operating parameters of each generator set are collected. Based on the real-time operating parameters of the grid side, the main unit is selected from the online generator set group and the main unit is synchronized. After the output voltage, frequency and phase of the main unit are consistent with the grid side, the main unit is controlled to connect to the grid. Based on the operating parameters of the master unit after grid connection, each slave unit is adjusted sequentially to make the output voltage, frequency and phase of each slave unit consistent with the master unit, and then each slave unit is controlled to connect to the grid.

8. The method according to claim 7, characterized in that, When selecting a main generator set from the online generator set group, the governor response time constant and excitation regulator response time constant of each generator set are obtained respectively. The generator set with the smallest sum of the governor response time constant and the excitation regulator response time constant is selected as the main generator set. When performing synchronous regulation on the main generator set, the intake valve opening of the main generator set is adjusted to adjust the generation frequency, and the excitation current of the main generator set is adjusted to adjust the output voltage, until the absolute value of the difference between the generation frequency and the grid frequency is less than the first frequency difference threshold and the absolute value of the difference between the output voltage and the grid voltage is less than the first voltage difference threshold.

9. The method according to claim 8, characterized in that, When each slave unit performs follow-up adjustment, the current frequency value and current voltage value of the master unit are used as the adjustment target values ​​of each slave unit. The intake valve opening and excitation current of each slave unit are adjusted respectively until the absolute value of the difference between the generation frequency of each slave unit and the frequency of the master unit is less than the second frequency difference threshold, and the absolute value of the difference between the generation voltage of each slave unit and the voltage of the master unit is less than the second voltage difference threshold; the second frequency difference threshold is less than the first frequency difference threshold, and the second voltage difference threshold is less than the first voltage difference threshold.

10. The method according to claim 1, characterized in that, Also includes: During power generation, the intake pressure values ​​of each access channel are continuously collected and their variation range is calculated. When the variation range of the intake pressure value of a certain access channel exceeds the preset variation threshold, the preprocessing parameters of that access channel are adjusted accordingly. The comprehensive energy quality index of the busbar is continuously calculated and its cross-level changes are monitored. When the comprehensive energy quality index undergoes cross-level changes, generator sets are reselected to form a new online generator set group. During the switching of generator sets, the generator set to be added is connected to the grid under no-load conditions and then its output power is increased in a stepwise manner. At the same time, the already connected generator sets reduce their output power synchronously until the power distribution reaches a new balance.

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