Biomass driven Stirling generator cogeneration system and control method thereof

Abstract

A biomass-driven Stirling generator cogeneration system and a control method thereof, the system comprising a fuel distribution subsystem, a heat distribution subsystem and a power generation subsystem, the fuel distribution subsystem comprising a solid biomass particle feed port, a gas preheater, liquefied petroleum gas, and a first blower; the heat distribution subsystem comprising a second blower, a first combustion chamber, a second combustion chamber, a first waste heat recovery device, a second waste heat recovery device, a heat pipe, cooling water, and a residential heating system; the power generation subsystem comprising a Stirling generator, a power converter, an energy storage battery, and a residential power system. The method uses cooling water and a heat source to control the output power of the generator, adjusts the cooling water flow rate by the cooling water temperature error and the cooling water temperature error change rate, adjusts the flow rate by configuring a plurality of valves, and controls the heat source by changing the fuel mixing ratio and supply speed, so that the output power of the generator is controlled, ensuring that the power supply and heating demand of the user matches the system output.

Description

Technical Field

[0001] The invention relates to a Stirling generator cogeneration system, and in particular to a biomass-driven Stirling generator cogeneration system and a control method thereof. Background Art

[0002] Biomass (including solid biomass, liquid biofuels and biogas) is the most abundant resource of all renewable energy sources, and sustainable use of biomass is considered one of the important options for solving environmental problems. Small and micro combined heat and power technologies can use solid biomass fuel for both heating and power generation, and have great potential in reducing energy costs and carbon dioxide emissions in residential and small commercial buildings.

[0003] The combined heat and power system that couples biomass and free piston Stirling generators has attracted widespread attention. Compared with the discontinuous combustion of internal combustion engines, it can achieve continuous combustion, with the advantages of low emissions, less maintenance, low noise, low vibration, and a wide range of fuel sources. In traditional combined heat and power systems, the output power of the free piston Stirling generator is adjusted by changing the heat source supply of the combustion chamber. However, due to uneven air / fuel mixing, unstable heat source output of the combustion chamber, and delayed heat transfer at the hot end of the free piston Stirling generator, it is very difficult to control the output power of the free piston Stirling generator, and it is difficult to achieve effective control of the power supply and heat supply of the combined heat and power system, and the overall efficiency and economy of the system are significantly reduced.

[0004] Uneven mixing of fuel and air in the combustion chamber can lead to local overheating or overcooling, affecting the accuracy of the overall heat source supply; the heat output of the combustion chamber is usually determined by the combustion rate of the fuel and the combustion chamber design. In actual operation, these parameters are affected by the external environment (such as temperature, pressure) and load changes. Fluctuations in the combustion rate can lead to uneven heat source input, which directly affects the output power, efficiency and stability of the Stirling engine; the free-piston Stirling engine relies on the heat exchanger of the heat source to transfer the heat of the combustion chamber to the working fluid, but the response speed of the heat exchanger is limited, the heat source transfer is delayed, and it cannot quickly adapt to changes in the heat output of the combustion chamber. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the above-mentioned background technology and provide a biomass-driven Stirling generator cogeneration system and a control method thereof, which utilizes cooling water and heat source to control the output power of the Stirling generator, adjusts the cooling water flow rate by the cooling water temperature error and the cooling water temperature error change rate, configures a flow rate regulation function through the coordination of multiple valves, changes the fuel mixing ratio and supply speed through mutual coordination, controls the heat source, and effectively controls the output power of the Stirling generator, thereby ensuring that the user's power supply and heating needs match the system output.

[0006] The technical solution adopted by the present invention to solve the technical problem is a biomass-driven Stirling generator cogeneration system, comprising a fuel distribution subsystem, a heat distribution subsystem and a power generation subsystem, wherein the fuel distribution subsystem comprises a solid biomass particle feed port, a gas preheater, liquefied petroleum gas, and a first blower; the heat distribution subsystem comprises a second blower, a first combustion chamber, a second combustion chamber, a first waste heat recovery device, a second waste heat recovery device, a heat pipe, cooling water, and a residential heat system; the power generation subsystem comprises a free piston Stirling generator, a power converter, an energy storage battery, and a residential power system;

[0007] The solid biomass particle feed port is connected to the first combustion chamber through a feed port pipeline, a first valve is provided on the feed port pipeline, a first blower is connected to the feed port pipeline through a first air pipeline, the first blower is connected to the gas preheater through a second air pipeline, the gas preheater is connected to the first combustion chamber through a pipeline, the liquefied petroleum gas is respectively connected to the gas preheater and the second combustion chamber through a three-way valve, the first combustion chamber is connected to the second combustion chamber through a pipeline, the second blower is connected to the second combustion chamber through a third air pipeline, the heat pipe is connected to the first combustion chamber and the second combustion chamber through a second valve, and the heat pipe is connected to a residential heating system;

[0008] The hot end of the free piston Stirling generator is connected to the second combustion chamber, and the second combustion chamber is connected to the first waste heat recovery device; the cold end of the free piston Stirling generator is connected to cooling water, and the cooling water is connected to the second waste heat recovery device, and the second waste heat recovery device is connected to the heat pipe;

[0009] The output end of the free piston Stirling generator is connected to the power converter, and the power converter is connected to the energy storage battery and the residential power system; the energy storage battery is provided with a switch connected to the free piston Stirling generator.

[0010] Furthermore, it also includes a dust collection subsystem, which includes a dust collector, an air cooler and a dust adsorber. The dust collector is connected to the first combustion chamber and the second combustion chamber, the first waste heat recovery device is connected to the air cooler, and the air cooler is connected to cooling water and the dust adsorber.

[0011] A control method for a biomass-driven Stirling generator cogeneration system comprises the following steps:

[0012] Step S1: Consider the difference between the supply and demand of electricity in a given hour, the difference between the supply and demand of heat in a given hour, and the difference between the charge and discharge of the energy storage battery in a given hour, and define the objective function as follows:

[0013] ,

[0014] In the formula, is the hour corresponding to the current time, is the amount of electricity demanded in a given hour, is the amount of electricity supplied in a given hour, is the caloric requirement for a given hour, is the sum of the calories supplied in a given hour, is the amount of energy storage battery charged in a given hour, is the amount of energy stored in the battery discharged in a given hour. are the weighting coefficients of electricity and heat supply respectively;

[0015] for The calculation formula is as follows:

[0016] ,

[0017] In the formula, is the output power of the free piston Stirling generator, is the instantaneous power of the energy storage battery, is the density of cooling water, is the cooling water flow rate, is the actual value of the cooling water outlet temperature at the cold end of the free piston Stirling generator, is the actual value of the cooling water inlet temperature at the cold end of the free piston Stirling generator, is the control quantity of the second valve, is the heating power corresponding to the maximum control amount of the second valve, is the charging power of the energy storage battery, is the discharge power of the energy storage battery;

[0018] Step S2: Normalize the power generation, heat supply, and energy storage battery capacity, and calculate the current time The corresponding objective function value is obtained by Calculate next time The control command is used to adjust the first valve, three-way valve, second valve and cooling water flow. as close to 0 as possible; the heat supply rate is controlled by the second valve, and the output power of the free piston Stirling generator is controlled by adjusting the cooling water flow and the heat source amount, specifically: the supply rate of solid biomass particles is controlled by the first valve, the supply rate of liquefied petroleum gas is controlled by the three-way valve, and the temperature of the cold end of the free piston Stirling generator is controlled by the cooling water flow.

[0019] Further, in step S2, 24 control instructions are issued within a given day, and the constraints are as follows:

[0020] ,

[0021] in, is the amount of electricity demanded in a given hour, is the amount of electricity supplied in a given hour, is the caloric requirement for a given hour, It is the sum of the calories supplied in a given hour.

[0022] Furthermore, the output power of the free piston Stirling generator is controlled by adjusting the cooling water flow and the heat source. The specific method is as follows:

[0023] Step 1: Determine the output variable as the cooling water flow adjustment , Heat source input adjustment , determine the input variable as the cooling water outlet temperature error , Free piston Stirling generator output power error , Cooling water outlet temperature error change rate , Output power error change rate , the calculation formula is as follows:

[0024] ,

[0025] In the formula, is the cooling water outlet temperature error, is the output power error of the free piston Stirling generator, is the expected value of the cooling water outlet temperature at the cold end of the free piston Stirling generator, is the actual value of the cooling water outlet temperature at the cold end of the free piston Stirling generator, is the expected output power of the free piston Stirling generator, is the output power of the free piston Stirling generator, is the cooling water outlet temperature error change rate, is the output power error change rate of the free piston Stirling generator;

[0026] Step 2: Define fuzzy sets, divide each input variable into five fuzzy sets, namely: large negative NB, small negative NS, zero Z, small positive PS, large positive PB, determine the value range of input and output variables; use triangular membership functions to represent the fuzzy sets of input and output;

[0027] Step 3: Adjust the cooling water flow rate Establish a fuzzy rule base and analyze the cooling water outlet temperature error and cooling water outlet temperature error change rate To adjust the cooling water flow ;when When is positive, increase the cooling water flow to reduce the temperature; when When it is negative, reduce the cooling water flow to avoid overcooling; if , indicating that the temperature changes rapidly, the cooling water flow rate should be adjusted quickly; if , then adjust the cooling water flow smoothly; if , the cooling water flow rate remains stable;

[0028] Adjustment amount for heat source input Establish a fuzzy rule base, when the output power error When it is positive, the heat source input is increased; when the output power error When it is negative, reduce the heat source input; if the output power error change rate , indicating that the error increases or decreases rapidly, then the heat source input should be adjusted quickly; if , then adjust the heat source input smoothly; if , maintain the current input and ensure system stability.

[0029] Furthermore, the value range of the input and output variables is determined as follows:

[0030] .

[0031] Furthermore, PID control is used to control the first valve, and the control quantity The calculation formula is as follows:

[0032] ,

[0033] in, is the control quantity of the rotation speed of the first valve, for The corresponding proportional, integral, and differential gain coefficients, The difference between electricity supply and demand;

[0034] The calculation formula is as follows:

[0035] when hour, ,

[0036] in, is the amount of electricity demanded in a given hour, is the amount of electricity supplied in a given hour, The case with the largest supply of solid biomass particles corresponds to the power generation of the free piston Stirling generator.

[0037] Furthermore, the three-way valve is controlled by proportional control. The calculation formula is as follows:

[0038] ,

[0039] in, for The corresponding proportional gain coefficient is, is the amount of electricity demanded in a given hour, The case with the largest supply of solid biomass particles corresponds to the power generation of the free piston Stirling generator.

[0040] Furthermore, PI control is used to control the second valve, and the control quantity The calculation formula is as follows:

[0041] ,

[0042] in, is the control value of the second valve opening, for The corresponding proportional and integral gain coefficients are: The difference between heat supply and demand;

[0043] The calculation formula is as follows:

[0044] ,

[0045] in, is the caloric requirement for a given hour, It is the sum of the calories supplied in a given hour.

[0046] Furthermore, the following power control is adopted for the control of the energy storage battery:

[0047] ,

[0048] in, is the instantaneous power of the energy storage battery, Power taken from a free-piston Stirling generator for a residential electrical system;

[0049] The current power of the energy storage battery is calculated by the following formula:

[0050] ,

[0051] in, For time The battery charge state of the energy storage module is the current Hourly power, For time The battery charge state of the energy storage module is Hourly power, is the nominal capacity of the battery, is the instantaneous power of the energy storage battery;

[0052] Set the energy storage battery discharge threshold according to user needs And the upper limit of power ,when Less than When Greater than The energy storage battery stops charging.

[0053] Compared with the prior art, the advantages of the present invention are as follows:

[0054] The present invention controls the Stirling generator cogeneration system in real time, uses cooling water and heat source to control the output power of the Stirling generator, adjusts the cooling water flow rate by the cooling water temperature error and the cooling water temperature error change rate, configures the flow rate regulation function through the coordination of multiple valves, changes the fuel mixing ratio and supply speed by mutual coordination, controls the heat source, and effectively controls the output power of the Stirling generator, ensuring that the user's power supply and heating demand match the system output. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a schematic structural diagram of a biomass-driven Stirling generator cogeneration system according to an embodiment of the present invention.

[0056] 1—solid biomass particle feed port, 2—first valve, 3—feed port pipeline, 4—first blower, 5—first air pipeline, 6—second air pipeline, 7—gas preheater, 8—three-way valve, 9—liquefied petroleum gas, 10—first combustion chamber, 11—second blower, 12—third air pipeline, 13—second combustion chamber, 14—dust collector, 15—second valve, 16—heat pipe, 17—first waste heat recovery device, 18—cooling water, 19—free piston Stirling generator, 20—second waste heat recovery device, 21—residential heating system, 22—power converter, 23—switch, 24—energy storage battery, 25—residential power system, 26—air cooler, 27—dust adsorber, DETAILED DESCRIPTION

[0057] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] In view of the problem that the current system has problems such as uneven air / fuel mixing, unstable heat source output in the combustion chamber, and delayed heat transfer at the hot end of the free piston Stirling generator, which leads to difficulty in controlling the output power of the free piston Stirling generator, and the mismatch between power supply and heating demand and system output, resulting in low overall efficiency, the present invention proposes a biomass-driven Stirling generator cogeneration system. Figure 1The system of this embodiment includes a fuel distribution subsystem, a heat distribution subsystem, a power generation subsystem and a dust collection subsystem. The fuel distribution subsystem includes a solid biomass particle feed inlet 1, a gas preheater 7, a liquefied petroleum gas 9, and a first blower 4; the heat distribution subsystem includes a second blower 11, a first combustion chamber 10, a second combustion chamber 13, a first waste heat recovery device 17, a second waste heat recovery device 20, a heat pipe 16, cooling water 18, and a residential heating system 21; the power generation subsystem includes a free piston Stirling generator 19, a power converter 22, an energy storage battery 24, and a residential power system 25; the dust collection subsystem includes a dust collector 14, an air cooler 26, and a dust adsorber 27.

[0059] The solid biomass particle feed port 1 is connected to the first combustion chamber 10 through the feed port pipeline 3, the feed port pipeline 3 is provided with a first valve 2, the first blower 4 is connected to the feed port pipeline 3 through the first air pipeline 5, the first blower 4 is connected to the gas preheater 7 through the second air pipeline 6, the gas preheater 7 is connected to the first combustion chamber 10 through the pipeline, the liquefied petroleum gas 9 is respectively connected to the gas preheater 7 and the second combustion chamber 13 through a three-way valve, the first combustion chamber 10 is connected to the second combustion chamber 13 through the pipeline, the second blower 11 is connected to the second combustion chamber 13 through the third air pipeline 12, the dust collector 14 is connected to the first combustion chamber 10 and the second combustion chamber 13, the heat pipe 16 is connected to the first combustion chamber 10 and the second combustion chamber 13 through the second valve 15, collects the hot air flow, and the heat pipe 16 is connected to the residential heating system 21.

[0060] The hot end of the free piston Stirling generator 19 is connected to the second combustion chamber 13 , the cold end of the free piston Stirling generator 19 is connected to the cooling water 18 , the cooling water 18 is connected to the second waste heat recovery device 20 , and the second waste heat recovery device 20 is connected to the heat pipe 16 .

[0061] The output end of the free piston Stirling generator 19 is connected to the power converter 22 , and the power converter 22 is connected to the energy storage battery 24 and the residential power system 25 ; the energy storage battery 24 is provided with a switch 23 connected to the free piston Stirling generator 19 .

[0062] The second combustion chamber 13 is connected to the first waste heat recovery device 17 , the first waste heat recovery device 17 is connected to the air cooler 26 , and the air cooler 26 is connected to the cooling water 18 and the dust adsorber 27 .

[0063] Solid biomass particles (wood pellets, wood chips, agricultural residues, etc.) are fed and transported from the solid biomass particle feed port 1. The feed speed of the fuel (solid biomass particles) is controlled by the rotation speed of the first valve 2. The fuel enters the first combustion chamber 10 through the feed port pipeline 3 for combustion; the first blower 4 provides air for fuel transportation through the first air pipeline 5, and the air used for fuel transportation is not preheated. The first blower 4 provides air for fuel combustion through the first combustion chamber 10 through the second air pipeline 6. The air in the second air pipeline 6 is preheated by the gas preheater 7 and then sent to the first combustion chamber 10. The air enters the first combustion chamber 10 in a vortex manner. The solid biomass particles are burned once in the first combustion chamber 10 and then enter the second combustion chamber 13 for secondary combustion, so as to achieve full combustion of the biomass fuel. The second blower 11 provides air for fuel combustion through the second combustion chamber 13 through the third air pipeline 12, and the air enters the second combustion chamber 13 without vortex.

[0064] The liquefied petroleum gas 9 has two functions. The first function is to provide a heat source for the gas preheater 7. The second function is that when the biomass-driven Stirling cogeneration system is started, the liquefied petroleum gas 9 is mixed with the air entering the gas preheater 7 for preheating and then enters the first combustion chamber 10, and is mixed with the air in the third air pipeline 12 and enters the second combustion chamber 13, and is mixed with the solid biomass particles and then ignited, so as to ensure that the solid biomass particles are fully fueled at the beginning, to prevent the blockage and accumulation of the pipe mouth, which leads to a decrease in the efficiency of the heat exchanger and a decrease in the heating effect, and at the same time, the temperature of the first combustion chamber 10 and the second combustion chamber 13 quickly reaches the set value, so as to achieve a quick start. The three-way valve 8 is connected to the liquefied petroleum gas 9, the gas preheater 7, and the second combustion chamber 13. The three-way valve 8 controls the supply amount of the liquefied petroleum gas 9 to the first combustion chamber 10 and the second combustion chamber 13. The air entering the gas preheater 7 is mixed with the liquefied petroleum gas 9 and enters the first combustion chamber 10 after being heated by the gas preheater 7. The main function is to help cold start and promote the full combustion of solid biomass particles. The liquefied petroleum gas 9 is mixed with the air in the third air pipeline 12 and enters the second combustion chamber 13 to provide a higher temperature for the second combustion chamber 13. This is very important when higher power consumption and higher heating supply are required.

[0065] The first combustion chamber 10 is an auxiliary combustion chamber. The solid biomass particles are burned once in the first combustion chamber 10 and then enter the second combustion chamber 13 for secondary combustion to achieve full combustion of the biomass fuel, which can reduce scaling and slagging on the boiler wall and the heat exchanger surface. The second combustion chamber 13 is a main combustion chamber, which serves as a heat source for the free piston Stirling generator 19 and the residential heating system 21. The supply speed of the solid biomass particles can be adjusted by the first valve 2, and the supply speed of the liquefied petroleum gas 9 can be adjusted by the three-way valve 8 to control the temperature of the heat source. The heat supply is adjusted by the second valve 15 to adjust the residential heating system 21. The first combustion chamber 10 and the second combustion chamber 13 are lined with refractory materials. During the cold start process, when the first combustion chamber 10 and the second combustion chamber 13 reach the set temperature, the three-way valve 8 is completely closed, and the fuel is completely provided by the solid biomass particles. When the speed of the first valve 2 is the maximum, the combustion chamber temperature cannot be increased by increasing the solid biomass particle supply speed. The three-way valve 8 can be used to adjust the supply amount and supply speed of the liquefied petroleum gas 9, increase the mixing ratio of the liquefied petroleum gas 9 in the fuel supply, and make the combustion chamber temperature continue to increase, thereby increasing the power generation power and heating power.

[0066] The exhaust gas of the free piston Stirling generator 19 passes through the first waste heat recovery device 17, which is a plate-type heat exchanger. The heat recovery forms of the first waste heat recovery device 17 include hot water, boilers, and heating. The second waste heat recovery device 20 is a shell and tube heat exchanger. The heat recovery form of the second waste heat recovery device 20 is hot water. After passing through the first waste heat recovery device 17, the exhaust gas passes through the air cooler 26. The air cooler 26 is cooled by cooling water 18. The exhaust gas cooled by the air cooler 26 passes through the dust adsorber 27 to remove dust particles. The adsorption film is detachable and replaced regularly to reduce air pollution. The operation process and data adopt an online monitoring and recording system. During the operation, ash and smoke are collected at the outlets of the first combustion chamber 10 and the second combustion chamber 13. The flame mode of the combustion chamber is monitored by a high-temperature resistant camera, and the real-time combustion situation of the combustion can be viewed through the side wall and the rear wall.

[0067] The dust collector 14 is connected to the first combustion chamber 10 and the second combustion chamber 13, and is used to collect the ash produced by the combustion of solid biomass particles, and clean it regularly to ensure that the combustion space of the combustion chamber does not change too much, and reduce the scaling and slagging on the boiler wall and the heat exchanger surface to ensure sufficient heat transfer. The second valve 15 controls the heat supply speed of the heat pipe 16, which is a shell and tube heat exchanger type, and provides heat for the residential heat system 21, which includes floor heating, water heaters, boilers, membrane distillation, etc.

[0068] The hot end of the free piston Stirling generator 19 is connected to the second combustion chamber 13, and the cold end is connected to the cooling water 18. The generated power is positively correlated with the temperature of the second combustion chamber 13. The electric energy output by the free piston Stirling generator 19 is stepped up and converted through the power converter 22 to provide electric energy for the residential power system 25. The excess electric energy is stored in the connected energy storage battery 24. When the energy storage battery 24 is full, a first control instruction is sent to the administrator. After the first control instruction is executed, the fuel supply is reduced, and the temperature of the second combustion chamber 13 drops, thereby reducing the power generation of the free piston Stirling generator 19. When the discharge amount of the energy storage battery 24 exceeds a certain threshold, a second control instruction is sent to the administrator. After the second control instruction is executed, the fuel supply is increased, and the temperature of the second combustion chamber 13 rises, thereby increasing the power generation of the free piston Stirling generator 19.

[0069] With respect to the biomass-driven Stirling generator cogeneration system of this embodiment, the present invention proposes a biomass-driven Stirling generator cogeneration system control method, which controls the Stirling cogeneration system in real time, configures a flow rate adjustment function through the coordination of multiple valves, changes the fuel supply speed, and ensures that the user's power supply and heating needs match the system output.

[0070] The objective function is defined by setting the power supply and demand difference and heat supply and demand difference as small as possible within a given hour, minimizing resource waste, reducing the rated capacity of the energy storage battery, and reducing system costs. As follows: (consider three factors)

[0071] ,

[0072] In the above formula, is the hour corresponding to the current time, is the amount of electricity demanded in a given hour, is the amount of electricity supplied in a given hour, is the caloric requirement for a given hour, is the sum of the calories supplied in a given hour, is the amount of energy storage battery charged in a given hour, is the amount of energy stored in the battery discharged in a given hour. They are the weighting coefficients of electricity supply and heat supply respectively.

[0073] In a given day, 24 control instructions are issued, and the constraints are as follows:

[0074] ,

[0075] Normalize the power generation, heat supply, and energy storage battery power to calculate the current time The corresponding objective function value is obtained by Calculate next time The control command is used to adjust the first valve 2, the three-way valve 8, the second valve 15, and the cooling water flow rate. As close to 0 as possible, the control amount of all valves varies from 0 to 100%. The supply rate of solid biomass particles is controlled by the first valve 2, the supply rate of liquefied petroleum gas 9 is controlled by the three-way valve 8, the supply rate of heat is controlled by the second valve 15, and the temperature of the cold end of the free piston Stirling generator is controlled by the cooling water flow.

[0076] for The calculation formula is as follows:

[0077] ,

[0078] In the formula, is the output power of the free piston Stirling generator, is the instantaneous power of the energy storage battery, is the density of cooling water, is the cooling water flow rate, is the actual value of the cooling water outlet temperature at the cold end of the free piston Stirling generator, is the actual value of the cooling water inlet temperature at the cold end of the free piston Stirling generator, is the control quantity of the second valve, is the heating power corresponding to the maximum control amount of the second valve, is the charging power of the energy storage battery, is the discharge power of the energy storage battery.

[0079] The hot end of the free piston Stirling generator 19 obtains heat from the combustion chamber. The amount of heat obtained by the free piston Stirling generator 19 from combustion affects the heating temperature. The heat source supply and cooling water flow of the combustion chamber affect the output power of the free piston Stirling generator 19. The cooling water 18 is connected to the residential heating system 21, such as a water heater, after passing through the second waste heat recovery device 20, affecting the hot water supply temperature. In order to fully consider the dynamic coordinated and stable control of the power supply power, hot water temperature, and heating temperature in the system, the present invention proposes a control method for the free piston Stirling generator, which controls the output power of the free piston Stirling generator by adjusting the cooling water flow and the heat source. Specifically:

[0080] Step 1: Determine the output variable as the cooling water flow adjustment , Heat source input adjustment , determine the input variable as the cooling water outlet temperature error , Free piston Stirling generator output power error , Cooling water outlet temperature error change rate , Output power error change rate , the calculation formula is as follows:

[0081] ,

[0082] In the formula, is the cooling water outlet temperature error, is the output power error of the free piston Stirling generator, is the expected value of the cooling water outlet temperature at the cold end of the free piston Stirling generator, is the actual value of the cooling water outlet temperature at the cold end of the free piston Stirling generator, is the expected output power of the free piston Stirling generator, is the output power of the free piston Stirling generator, is the cooling water outlet temperature error change rate, is the output power error change rate of the free piston Stirling generator.

[0083] Step 2: Define fuzzy sets and divide each input variable into five fuzzy sets, namely: big negative (NB), small negative (NS), zero (Z), small positive (PS), and big positive (PB). Determine the value range of the input and output variables as follows:

[0084] ,

[0085] The triangular membership function is used to represent the fuzzy set of input and output, as shown in Table 1. :

[0086] Table 1 Fuzzy sets of input and output ,

[0087] Step 3: Adjust the cooling water flow rate Establish a fuzzy rule base, combined with the cooling water outlet temperature error and cooling water outlet temperature error change rate , as shown in Table 2, the design is:

[0088] Table 2 Cooling water flow adjustment Fuzzy rule base ,

[0089] In this fuzzy rule base, the elements in the top row represent the input variables. The fuzzy language value of the leftmost column represents the input variable The remaining elements represent the output of the controller (cooling water flow adjustment amount) under the corresponding input conditions. ) fuzzy language value.

[0090] By analyzing the cooling water outlet temperature error and cooling water outlet temperature error change rate To adjust the cooling water flow ;when When it is positive (temperature is high), the cooling water flow rate needs to be increased to reduce the temperature; when When it is negative (low temperature), the cooling water flow rate needs to be reduced to avoid overcooling; the adjustment range is affected by the cooling water temperature error change rate Impact: If , indicating that the temperature changes rapidly and the cooling water flow needs to be adjusted quickly; if , the adjustment should be smoother; if , the cooling water flow can be kept stable to avoid over-adjustment. Dynamically balance the cooling water flow to ensure that the system temperature is stable within the target range.

[0091] Adjustment amount for heat source input Establish a fuzzy rule base, combined with the output power error and output power error change rate , as shown in Table 3, the design is:

[0092] Table 3 Heat source input adjustment Fuzzy rule base ,

[0093] In this fuzzy rule base, the elements in the top row represent the input variables. The fuzzy language value of the leftmost column represents the input variable The remaining elements represent the output of the controller (heat source input adjustment amount) under the corresponding input conditions. ) fuzzy linguistic value.

[0094] When the output power error When the output power is insufficient (positive error), the heat source input needs to be increased; when the output power is too high (negative error), the heat source input needs to be reduced. The adjustment range depends on the size and change trend of the output power error: if the output power error change rate , indicating that the error grows or decreases rapidly and requires stronger adjustment; if , the adjustment can be smooth. , can maintain the current input and ensure system stability. It can achieve dynamic balance of heat source input and realize fast response and stable control of power output.

[0095] Control the input of heat source through the first valve and three-way valve:

[0096] The first valve is controlled by PID control. The calculation formula is as follows:

[0097] ,

[0098] is the control quantity of the rotation speed of the first valve, for The corresponding proportional, integral, and differential gain coefficients, is the difference between electricity supply and demand, and the calculation formula is as follows:

[0099] when hour, ,

[0100] The case with the largest supply of solid biomass particles corresponds to the power generation of the free piston Stirling generator.

[0101] The three-way valve is controlled by proportional control. The calculation formula is as follows:

[0102] ,

[0103] for The corresponding proportional gain coefficient.

[0104] Control the heat output through the second valve:

[0105] The second valve is controlled by PI control. The calculation formula is as follows:

[0106] ,

[0107] is the control value of the second valve opening, for The corresponding proportional and integral gain coefficients are: is the difference between heat supply and demand, calculated as follows:

[0108] ,

[0109] The following power control algorithm is used for the control of energy storage batteries:

[0110] ,

[0111] in, is the instantaneous power of the energy storage battery, Power taken from a free-piston Stirling generator for a residential electrical system.

[0112] The current power of the energy storage battery is calculated by the following formula:

[0113] ,

[0114] in, For time The battery charge state of the energy storage module is the current Hourly power, For time The battery charge state of the energy storage module is Hourly power, is the nominal capacity of the battery, is the instantaneous power of the energy storage battery.

[0115] Set the energy storage battery discharge threshold according to user needs And the upper limit of power ,when Less than When Greater than The energy storage battery stops charging.

[0116] In order to match the power supply and heat supply, we select objective functions with different weights. , that is, choose different The objective function under the value , corresponding to different operation modes, the economic performance of the Stirling cogeneration system is evaluated through interactive iterative calculation. The evaluation function is as follows:

[0117] ,

[0118] Indicates time, Indicates the month in which the Stirling CHP system was put into operation. To level out the cost of electricity, is the initial investment cost, For each month's operating costs, For each month's fuel cost, For each month's operating and maintenance costs, is the discount rate, is the monthly income, is the unit heat price, For each month's electricity generation, For each month's heating supply.

[0119] Through the evaluation of the Stirling cogeneration system, different operating modes are obtained by controlling the instructions, which increases the flexibility of system configuration and meets the daily needs of different types of households. The balance between power supply and heat supply and the balance of system supply and demand are comprehensively considered, which effectively improves the overall efficiency of the Stirling cogeneration system, ensures stable power supply to residential electricity, improves waste heat recovery from exhaust gas and the cold end of the free piston Stirling generator, and reduces heat loss.

[0120] The present invention controls the Stirling generator cogeneration system in real time, uses cooling water and heat source to control the output power of the Stirling generator, adjusts the cooling water flow rate by the cooling water temperature error and the cooling water temperature error change rate, configures the flow rate regulation function through the coordination of multiple valves, changes the fuel mixing ratio and supply speed by mutual coordination, controls the heat source, and effectively controls the output power of the Stirling generator, ensuring that the user's power supply and heating demand match the system output.

[0121] Those skilled in the art may make various modifications and variations to the present invention. If these modifications and variations are within the scope of the claims of the present invention and their equivalents, then these modifications and variations are also within the protection scope of the present invention.

Claims

1. A biomass driven Stirling generator cogeneration system, characterized in that: It includes a fuel distribution subsystem, a heat distribution subsystem and a power generation subsystem, wherein the fuel distribution subsystem includes a solid biomass particle feed port, a gas preheater, liquefied petroleum gas, and a first blower; The heat distribution subsystem includes a second blower, a first combustion chamber, a second combustion chamber, a first waste heat recovery device, a second waste heat recovery device, a heat pipe, cooling water, and a residential heat system; the power generation subsystem includes a free piston Stirling generator, a power converter, an energy storage battery, and a residential power system; The solid biomass particle feed port is connected to the first combustion chamber through a feed port pipeline, a first valve is provided on the feed port pipeline, a first blower is connected to the feed port pipeline through a first air pipeline, the first blower is connected to the gas preheater through a second air pipeline, the gas preheater is connected to the first combustion chamber through a pipeline, the liquefied petroleum gas is respectively connected to the gas preheater and the second combustion chamber through a three-way valve, the first combustion chamber is connected to the second combustion chamber through a pipeline, the second blower is connected to the second combustion chamber through a third air pipeline, the heat pipe is connected to the first combustion chamber and the second combustion chamber through a second valve, and the heat pipe is connected to a residential heating system; The hot end of the free piston Stirling generator is connected to the second combustion chamber, and the second combustion chamber is connected to the first waste heat recovery device; the cold end of the free piston Stirling generator is connected to cooling water, and the cooling water is connected to the second waste heat recovery device, and the second waste heat recovery device is connected to the heat pipe; The output end of the free piston Stirling generator is connected to the power converter, and the power converter is connected to the energy storage battery and the residential power system; the energy storage battery is provided with a switch connected to the free piston Stirling generator.

2. The biomass driven Stirling generator cogeneration system according to claim 1, characterized in that: It also includes a dust collection subsystem, which includes a dust collector, an air cooler and a dust adsorber. The dust collector is connected to the first combustion chamber and the second combustion chamber, the first waste heat recovery device is connected to the air cooler, and the air cooler is connected to cooling water and the dust adsorber.

3. A control method for a biomass-driven Stirling generator cogeneration system applied to the system of claim 1 or 2, characterized in that: The following steps are involved: Step S1: Consider the difference between the supply and demand of electricity in a given hour, the difference between the supply and demand of heat in a given hour, and the difference between the charge and discharge of the energy storage battery in a given hour, and define the objective function as follows: ， In the formula, is the hour corresponding to the current time, is the amount of electricity demanded in a given hour, is the amount of electricity supplied in a given hour, is the caloric requirement for a given hour, is the sum of the calories supplied in a given hour, is the amount of energy storage battery charged in a given hour, is the amount of energy stored in the battery discharged in a given hour. are the weighting coefficients of electricity and heat supply respectively; for The calculation formula is as follows: ， In the formula, is the output power of the free piston Stirling generator, is the instantaneous power of the energy storage battery, is the density of cooling water, is the cooling water flow rate, is the actual value of the cooling water outlet temperature at the cold end of the free piston Stirling generator, is the actual value of the cooling water inlet temperature at the cold end of the free piston Stirling generator, is the control quantity of the second valve, is the heating power corresponding to the maximum control amount of the second valve, is the charging power of the energy storage battery, is the discharge power of the energy storage battery; Step S2: Normalize the power generation, heat supply, and energy storage battery capacity, and calculate the current time The corresponding objective function value is obtained by Calculate next time The control command is used to adjust the first valve, three-way valve, second valve and cooling water flow. as close to 0 as possible; the heat supply rate is controlled by the second valve, and the output power of the free piston Stirling generator is controlled by adjusting the cooling water flow and the heat source amount, specifically: the supply rate of solid biomass particles is controlled by the first valve, the supply rate of liquefied petroleum gas is controlled by the three-way valve, and the temperature of the cold end of the free piston Stirling generator is controlled by the cooling water flow.

4. The control method of the biomass driven Stirling generator cogeneration system according to claim 3, characterized in that: In step S2, 24 control instructions are issued within a given day, and the constraints are as follows: ， in, is the amount of electricity demanded in a given hour, is the amount of electricity supplied in a given hour, is the caloric requirement for a given hour, It is the sum of the calories supplied in a given hour.

5. The biomass driven Stirling generator cogeneration system control method according to claim 3, characterized in that: The output power of the free piston Stirling generator is controlled by adjusting the cooling water flow and the heat source. The specific method is as follows: Step 1: Determine the output variable as the cooling water flow adjustment , Heat source input adjustment , determine the input variable as the cooling water outlet temperature error , Free piston Stirling generator output power error , Cooling water outlet temperature error change rate , Output power error change rate , the calculation formula is as follows: ， In the formula, is the cooling water outlet temperature error, is the output power error of the free piston Stirling generator, is the expected value of the cooling water outlet temperature at the cold end of the free piston Stirling generator, is the actual value of the cooling water outlet temperature at the cold end of the free piston Stirling generator, is the expected output power of the free piston Stirling generator, is the output power of the free piston Stirling generator, is the cooling water outlet temperature error change rate, is the output power error change rate of the free piston Stirling generator; Step 2: Define fuzzy sets, divide each input variable into five fuzzy sets, namely: large negative NB, small negative NS, zero Z, small positive PS, large positive PB, determine the value range of input and output variables; use triangular membership functions to represent the fuzzy sets of input and output; Step 3: Adjust the cooling water flow rate Establish a fuzzy rule base and analyze the cooling water outlet temperature error and cooling water outlet temperature error change rate To adjust the cooling water flow ;when When is positive, increase the cooling water flow to reduce the temperature; when When it is negative, reduce the cooling water flow to avoid overcooling; if , indicating that the temperature changes rapidly, the cooling water flow rate should be adjusted quickly; if , then adjust the cooling water flow smoothly; if , the cooling water flow rate remains stable; Adjustment amount for heat source input Establish a fuzzy rule base, when the output power error When it is positive, the heat source input increases; when the output power error When it is negative, reduce the heat source input; If the output power error change rate , indicating that the error increases or decreases rapidly, then the heat source input should be adjusted quickly; if , then adjust the heat source input smoothly; if , maintain the current input and ensure system stability.

6. The control method of the biomass driven Stirling generator cogeneration system according to claim 5, characterized in that: Determine the value range of input and output variables as follows: 。 7. The control method of the biomass driven Stirling generator cogeneration system according to claim 3, characterized in that: The first valve is controlled by PID control. The calculation formula is as follows: ， in, is the control quantity of the rotation speed of the first valve, for The corresponding proportional, integral, and differential gain coefficients, The difference between electricity supply and demand; The calculation formula is as follows: when hour, , in, is the amount of electricity demanded in a given hour, is the amount of electricity supplied in a given hour, The case with the largest supply of solid biomass particles corresponds to the power generation of the free piston Stirling generator.

8. The biomass driven Stirling generator cogeneration system control method according to claim 3, characterized in that: The three-way valve is controlled by proportional control. The calculation formula is as follows: ， in, for The corresponding proportional gain coefficient, is the amount of electricity demanded in a given hour, The case with the largest supply of solid biomass particles corresponds to the power generation of the free piston Stirling generator.

9. The biomass driven Stirling generator cogeneration system control method according to claim 3, characterized in that: The second valve is controlled by PI control. The calculation formula is as follows: ， in, is the control value of the second valve opening, for The corresponding proportional and integral gain coefficients are: The difference between heat supply and demand; The calculation formula is as follows: ， in, is the caloric requirement for a given hour, It is the sum of the calories supplied in a given hour.

10. The control method of the biomass driven Stirling generator cogeneration system according to claim 3, characterized in that: The following power control is used for the control of energy storage batteries: ， in, is the instantaneous power of the energy storage battery, Power taken from a free-piston Stirling generator for a residential electrical system; The current power of the energy storage battery is calculated by the following formula: ， in, For time The battery charge state of the energy storage module is the current Hourly power, For time The battery charge state of the energy storage module is Hourly power, is the nominal capacity of the battery, is the instantaneous power of the energy storage battery; Set the energy storage battery discharge threshold according to user needs And the upper limit of power ,when Less than When Greater than The energy storage battery stops charging.

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