Large-scale air turbine generator set primary frequency modulation model, control parameter tuning method and control model

Abstract

The invention discloses a primary frequency modulation control parameter tuning method and a control model for a large air turbine generator set, and the method comprises the steps: building a primary frequency modulation control model which comprises a PID controller, an air turbine model, a speed regulator model and a salt cavern thermodynamic dynamic model, and carrying out the parameter optimization of the PID controller through employing an improved PSO algorithm for increasing a contraction factor. A step disturbance test is carried out on the primary frequency modulation control model, and dynamic response indexes of primary frequency modulation active power regulation time, rise time, overshoot and oscillation frequency oscillation are counted and analyzed; and the influence of the primary frequency modulation action of the unit on safe and stable operation of the gas storage device (salt cavern) is evaluated. According to the invention, primary frequency modulation control parameter tuning based on simulation verification can be obtained, and the method can be used for aiding design engineering actual primary frequency modulation control strategy and parameter setting; quantitative analysis of primary frequency modulation dynamic characteristics of a large-scale compressed air energy storage power station is realized, and the method has certain guiding significance for design optimization, field debugging and testing of unit matching host equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of large-scale physical energy storage, and in particular to a primary frequency regulation control parameter tuning method for a large-scale air turbine generator set, and a primary frequency regulation control model. Background Art

[0002] In the process of low-carbonization of the power system, it is imperative to adjust the power structure, and a new power system that widely absorbs new energy will be gradually built. The inherent volatility and uncertainty of new energy power generation, as well as the high proportion of power electronics in its power equipment, will bring many challenges to the safe and stable operation of the power grid. In this context, mechanical physical energy storage represented by compressed air energy storage has become the preferred solution to support the safe and stable operation of the new power system, promote the efficient absorption of new energy power generation, and help achieve the dual carbon goals with its long-term migration ability of power and energy, good stable output and frequency and peak regulation capabilities, friendly environmental adaptability and access system capabilities.

[0003] The basic principle of compressed air energy storage is: during the energy storage process, electric energy drives the compressor to generate high-pressure air and store it in the air storage device; during the energy release process, the air in the air storage device expands to drive the turbine generator to generate electricity. According to different standards, compressed air energy storage is classified as follows: according to whether the combustion chamber needs to preheat the air, it is divided into supplementary combustion system and non-supplementary combustion system; according to the energy storage scale, it is divided into large system, small system and micro system; according to whether the compression heat is used, it is divided into non-adiabatic, adiabatic and constant temperature. At present, the domestic compressed air energy storage industry is accelerating its development in the direction of large-scale, high efficiency, low cost, systematization and industrialization.

[0004] Primary frequency regulation refers to the automatic control process in which the control system of the unit automatically controls the increase or decrease of the unit's active power when the frequency of the power grid deviates from the rated value, limits the change of the power grid frequency, and maintains a stable power grid frequency. Primary frequency regulation requires a short reaction time and can respond quickly to frequency changes. At present, there is no report on the primary frequency regulation function and characteristics of large-scale compressed air energy storage power stations.

[0005] Among the various grid-related functions of compressed air energy storage power stations, such as peak regulation, frequency regulation, phase regulation, inertia support, and black start, primary frequency regulation is particularly important in utilizing the advantages of compressed air energy storage, giving full play to the value of power auxiliary services, and maintaining the safe and stable operation of the power grid. However, the existing grid-connected power model library lacks a large-scale compressed air energy storage speed regulation system model suitable for power grid stability analysis. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for tuning the primary frequency regulation control parameters of a large air turbine generator set. The method establishes a primary frequency regulation control model of a large air turbine generator set that includes a salt cavern thermodynamic dynamic model and is suitable for power grid stability analysis. An improved PSO algorithm with an increased contraction factor is used to optimize the controller parameters to obtain excellent control quality, and the primary frequency regulation control parameter tuning based on simulation verification is obtained to assist in the design of actual primary frequency regulation control strategies and parameter setting in engineering.

[0007] The purpose of the present invention is also to provide a method for tuning the primary frequency regulation control parameters of a large air turbine generator set, and a primary frequency regulation control model, which is used to implement the method for tuning the primary frequency regulation control parameters of a compressed air energy storage generator set of a large air turbine, enrich the existing grid-connected power supply model library, provide a theoretical basis for the actual measurement and modeling of on-site speed regulation system parameters, and play a basic guarantee role in the safe and stable operation of the power grid.

[0008] The method of the present invention comprises the following steps:

[0009] Step 1: Based on the basic laws of thermodynamics and the ideal gas state equation, a thermodynamic dynamic model of the salt cavern during the energy release process of the large-scale compressed air energy storage generator set is established to obtain a differential equation group model that can characterize the dynamic change law of the salt cavern pressure ratio and temperature during the energy release process;

[0010]

[0011] In the formula, h c is the salt cavern wall heat transfer coefficient, w / m 2 K; A is the salt cavern wall area, m 2 ; T rw and T are the wall temperature and gas temperature, K respectively; c v is the specific heat at constant volume, J / (kg*K); c p is the specific heat at constant pressure J / kg*K; R g is the gas constant, 287 J / kg*K;

[0012] Step 2, establish an air turbine model and obtain parameters in the model: according to the structure and size data of the three-stage expansion air turbine, the concentrated parameter method is used to obtain the volume time constant of the high-pressure air inlet chamber, the volume time constant of the pipes before and after the first-stage heat exchanger, and the volume time constant parameters of the pipes before and after the second-stage heat exchanger;

[0013] Step 3, calculating the natural over-modulation coefficient λ of the high-pressure cylinder power;

[0014] Step 4: Establish a governor model that meets the actual engineering situation to accurately control the speed and load of the air turbine; the governor model includes a limit link and a rate limit link, and the proportional coefficient K GIt is the inverse of the air turbine speed inequality, and is generally taken as 24 to 25;

[0015] Step 5: Integrate the above-established salt cavern thermodynamic dynamic model, air turbine model, and speed regulator model to obtain a primary frequency regulation model of a large air turbine generator set that takes into account the thermodynamic characteristics of the salt cavern;

[0016] Step 6: Introduce the parallel PID commonly used in engineering practice.

[0017] Its transfer function expression is:

[0018] Among them, Kp is the proportional coefficient, Ki is the integral time constant, and Kd is the differential time constant, and the three are parameters to be optimized and set; thus, a primary frequency modulation control model of a large air turbine generator set is formed, and the model includes a PID controller, an air turbine model, a speed regulator model, and a salt cavern thermodynamic dynamic model. The control loop excitation signal adopts a small frequency difference disturbance, a large frequency difference step disturbance, or a method of simulating the real frequency of the power grid; the control loop excitation signal refers to the excitation signal of the closed-loop control loop "primary frequency modulation control model of a large air turbine generator set";

[0019] Step 7: Introduce an improved particle swarm algorithm to iteratively optimize the PID controller parameters. Add a contraction factor on the basis of the conventional standard PSO algorithm, which can effectively control the flight speed of particles and stimulate the ability of particles to explore new areas, so that the algorithm can achieve an effective balance between global detection and local mining, and ensure the convergence of the algorithm. The particle speed update formula is as follows;

[0020]

[0021] where φ is called the shrinkage factor, C = c1 + c2, and C > 4;

[0022] The control system performance evaluation uses the IAE index, that is, the integral absolute error index. The smaller the IAE index, the higher the accuracy of the system.

[0023] Step 8: According to the above algorithm steps, set the number of particles, learning factor, and number of iterations to achieve the improved particle swarm algorithm to optimize the parameters of the air turbine primary frequency modulation PID controller, and finally optimize the PID controller parameters Kp, Ki, and Kd;

[0024] Step 9: Conduct a step disturbance test on the primary frequency modulation control model of the large air turbine generator set, and statistically analyze various dynamic response indicators such as primary frequency modulation active power adjustment time, rise time, overshoot, and oscillation frequency;

[0025] Step 10: Statistically analyze the decrease in salt cavern pressure and temperature during the primary frequency modulation action compared with those without the primary frequency modulation action, and evaluate the impact of the primary frequency modulation action of the unit on the safe and stable operation of the salt cavern.

[0026] In step 2 of the present invention, an air turbine model is established, and the parameters in the model are obtained as follows:

[0027] According to the continuity equation, the time constant of gas flowing through the pipe is:

[0028]

[0029] Where T' is the time constant, s; p' is the constant pipeline pressure, Pa; Q' is the gas flow rate, kg / s; V is the pipeline volume, m 3 ; K is the density change caused by pressure change under constant temperature conditions, s 2 / m 2 .v s is the specific volume assuming constant temperature in a pipeline, m 3 / kg; t0 is the pipeline temperature, which is set to a constant value.

[0030] Assuming that p2 and p1 are a certain pressure range, and v2 and v1 are their corresponding specific volumes, equation (5) can be rewritten as:

[0031]

[0032] Combining equations (4) to (6), the volume time constants of the high-pressure air inlet chamber, the first-stage heat exchanger, and the pipes before and after the second-stage heat exchanger can be calculated as follows:

[0033] {T CH 、T RH 、T CO} (7)

[0034] For each expansion stage of the air turbine, the output power of each cylinder is:

[0035] P K =Q K (h ink -h outk ) (8)

[0036] Where P K is the output power of a certain section of turbine cylinder, kJ / s; Q K is the flow rate of this section, kg / s; h ink and h outk are the inlet and outlet enthalpies of this section, kJ / kg respectively.

[0037] According to formula (8), the power coefficients of high, medium and low pressure cylinders can be calculated as follows:

[0038] {F HP 、F IP 、F LP} (9)

[0039] The natural overmodulation coefficient λ of the high-pressure cylinder power is calculated in step 3 of the present invention as follows:

[0040]

[0041] In the formula, k is the adiabatic coefficient. For ideal gas, k = 1.4; ε is the high-pressure cylinder pressure ratio.

[0042] In step 9 of the present invention, the step disturbance test is performed by applying a large frequency difference disturbance signal to the primary frequency modulation control model of this large air turbine generator set, and performing a quantitative analysis of the dynamic characteristics of the primary frequency modulation of the large compressed air energy storage unit and an analysis of the changing laws of thermodynamic parameters such as salt cavern temperature, flow, and pressure.

[0043] A primary frequency modulation control model of a large air turbine generator set of the present invention comprises a salt cavern thermodynamic dynamic model, an air turbine model, a speed regulator model and a regulating valve to form the primary frequency modulation model, a PID controller is added to the primary frequency modulation model to realize a primary frequency modulation control model of a large air turbine generator set with closed-loop control; in the primary frequency modulation control model of the large air turbine generator set, an improved PSO algorithm assigns values ​​to the PID controller to determine control parameters; the speed regulator model is connected to the regulating valve; the regulating valve is respectively connected to the salt cavern model and the air turbine model; a frequency difference signal is passed through a primary frequency modulation load compensation module to generate a deviation between a primary frequency modulation power target value and an actual frequency modulation power, which is input into the PID controller; the PID controller is connected to the primary frequency modulation model, and the primary frequency modulation model receives instructions from the PID controller.

[0044] The primary frequency regulation model of the large air turbine generator set of the present invention obtains the model time constant of the pipelines before and after the first and second stage heat exchangers respectively by the lumped parameter method according to the structure and size data of the large air turbine; the speed regulator model meets the actual engineering situation and includes a limiting link and a rate limiting link; and the thermodynamic dynamic model of the salt cavern in the energy release stage is established according to the basic equations of working fluid and energy balance.

[0045] In the present invention, step 1 establishes a salt cavern thermodynamic dynamic model, steps 2 and 3 establish an air turbine model, step 4 establishes a speed regulator model, and step 5 integrates the above models to obtain a primary frequency modulation model of a large air turbine generator set. The above are objects to be controlled. Step 6 introduces a parallel PID to constitute a primary frequency modulation control model of a large air turbine generator set. The parameters of the PID are the parameters to be optimized. In step 7, an improved PSO algorithm is introduced. Step 8 uses the algorithm to optimize the PID parameters. Steps 9 and 10 are simulation verification and analysis.

[0046] Compared with the prior art, the present invention has the following beneficial technical effects:

[0047] The large-scale compressed air energy storage primary frequency regulation model suitable for power grid stability analysis proposed in the present invention enriches the existing grid-connected power supply model library, provides a theoretical basis for the actual measurement and modeling of on-site speed regulation system parameters, and plays a basic role in ensuring the safe and stable operation of the power grid.

[0048] The primary frequency regulation model and control parameter tuning method of a large air turbine generator set provided by the present invention can obtain the primary frequency regulation control parameter tuning based on simulation verification, and can be used to assist in the design of the actual primary frequency regulation control strategy and parameter setting of the engineering. An improved PSO algorithm with an increased contraction factor is used to optimize the controller parameters. The design process involved, such as the fitness function, optimization step length and direction, and iterative update of individual positions, is clear in meaning, and the parameter setting is simple, which has strong engineering practical value;

[0049] The present invention realizes quantitative analysis of primary frequency modulation dynamic characteristics of large-scale compressed air energy storage units, design optimization of supporting host equipment of the units, safe operation evaluation of gas storage devices, on-site debugging and testing, and has certain guiding significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a structural diagram of a primary frequency modulation control model of a three-stage expansion air turbine generator set according to an embodiment of the present invention;

[0051] Figure 2-1 is a salt cavern pressure ratio curve diagram of the energy release process in an embodiment of the present invention;

[0052] Figure 2-2 is a salt cavern temperature curve diagram of the energy release process in an embodiment of the present invention;

[0053] Figure 3 is a structural diagram of an air turbine model in an embodiment of the present invention;

[0054] Figure 4 is a structural diagram of a speed regulator model in an embodiment of the present invention;

[0055] Figure 5 is the adaptability curve of the primary frequency modulation control system in the embodiment of the present invention;

[0056] Figure 6 is a step response curve of a primary frequency modulation control system in an embodiment of the present invention;

[0057] Figure 7 This is a curve of salt cavern pressure change during a frequency modulation action in an embodiment of the present invention;

[0058] Figure 8This is a curve of the change of salt cavern temperature during a frequency modulation action in an embodiment of the present invention. DETAILED DESCRIPTION

[0059] The present invention will be further described below in conjunction with the accompanying drawings, attached tables and examples. It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. It should be noted that all technical and scientific terms used herein have the same meanings as those commonly understood by those of ordinary skill in the art to which the present invention belongs.

[0060] Figure 1 The figure shows the primary frequency modulation control model of the three-stage expansion air turbine generator set of the present invention, which is composed of a salt cavern thermodynamic dynamic model 1, an air turbine model 2, a speed regulator model 3, and a regulating valve 4. The primary frequency modulation model is added with a PID controller 5 to realize the primary frequency modulation control model of the three-stage expansion air turbine generator set with closed-loop control; in the primary frequency modulation control model of the three-stage expansion air turbine generator set, the improved PSO algorithm 6 assigns values ​​to the PID controller 5 to determine the control parameters; the speed regulator model 3 is connected to the regulating valve 4; the regulating valve 4 is respectively connected to the salt cavern thermodynamic dynamic model 1 and the air turbine model 2; the frequency difference signal is passed through the primary frequency modulation load compensation module 7 to generate the deviation between the primary frequency modulation power target value and the actual frequency modulation power, which is input into the PID controller 5; the PID controller 5 is connected to the primary frequency modulation model, and the primary frequency modulation model receives the instruction from the PID controller 5.

[0061] Example 1: A thermodynamic dynamic model of a salt cavern during the energy release process of a 300MW-class large-scale compressed air energy storage generator set was established, and the dimensions and thermodynamic parameters of the gas storage device (salt cavern) were collected. To simplify the calculation and in combination with the actual project, the following assumptions were made: (1) The convection heat transfer coefficient between the gas and the wall in the salt cavern remains constant, and the thermal conductivity of the wall is infinite; (2) The air used to do work is an ideal gas that satisfies the ideal gas equation. For a constant volume and constant wall temperature salt cavern, the gas in any process satisfies the first law of thermodynamics:

[0062] δQ=dU+h out δm out -h in δm in +δW (A)

[0063] Where, δQ is the heat exchange between the salt cavern and the outside world, J; dU is the change in energy within the salt cavern, J; h in 、h out are the specific enthalpy of the gas at the salt cavern inlet and outlet, J / kg; δm in ,δm out are the gas mass flow rates in and out of the salt cavern, kg / s; δW is the work done by the salt cavern gas, J.

[0064] In the energy release stage, the initial state parameters of the salt cavern, such as temperature and pressure, are known. During the energy release process, δm in =0, and for a constant volume salt cavern, δW = 0, the above formula can be simplified to:

[0065] δQ=d(mu)+h out δm out =h c A(T rw -T)dt (B)

[0066] In the formula, h c is the salt cavern wall heat transfer coefficient, w / m 2 K, A is the wall area of ​​the salt cavern, m 2 , T rw and T are the wall temperature and gas temperature respectively, K. is the temperature unit.

[0067] According to the above assumptions, for an ideal gas: u = c v T (C)

[0068] h=c p T (D)

[0069] PV=mR g T (E)

[0070] In the formula, c v is the specific heat at constant volume, J / (kg*K); c p is the specific heat at constant pressure J / kg*K; R g is the gas constant, 287J / kg*K.

[0071] By differentiating equation (E) and combining it with equations (A) to (D), we can get the relationship between the pressure ratio in the salt cavern and time during the energy release stage (1). By differentiating equation (C), dividing both sides of the equation by dt and combining it with equation (1), we can get the relationship between the gas temperature in the salt cavern and time during the energy release stage (2):

[0072]

[0073] In this embodiment, the air turbine is a 300MW high, medium and low pressure three-stage expansion air turbine with a rated high-pressure inlet pressure of 7.0MPa and a rated high-pressure inlet temperature of 170°C. The unit adopts a sliding pressure operation mode with a sliding pressure range of 6.0 to 8.0MPa.

[0074] 2 is a curve diagram of the thermodynamic model of the salt cavern during the energy release process in an example of the present invention. Under the conditions of an initial salt cavern pressure of 7.0 MPa and a temperature of 330 K, it reflects the pressure ratio and temperature changes of the salt cavern under the 75% Pe condition.

[0075] See also Figure 3, using the steam turbine model structure including the high-pressure cylinder power overregulation coefficient given in DL / T 1235-2019 "Guidelines for the Measurement and Modeling of Synchronous Generator Prime Mover and Its Regulation System Parameters", the parameters to be obtained are the volume time constants of the high-pressure air intake chamber and the pipes before and after the first and second heat exchangers. In the following, based on the structure and size data of the three-stage expansion air turbine, the model parameters of the high-pressure air intake chamber and the pipes before and after the first and second heat exchangers are respectively obtained by the concentrated parameter method. In the example of the present invention, the modeling is carried out based on the operating point of 7MPa main air pressure, 170℃ intake air temperature and 75% rated load of the air turbine generator set, and other operating conditions are similar.

[0076] According to the continuity equation, the time constant of gas flowing through the pipe is:

[0077]

[0078] Where T' is the time constant, s; p' is the constant pipeline pressure, Pa; Q' is the gas flow rate, kg / s; V is the pipeline volume, m 3 ; K is the density change caused by pressure change under constant temperature conditions, s 2 / m 2 .v s is the specific volume assuming constant temperature in a pipeline, m 3 / kg; t0 is the pipeline temperature, which is set to a constant value.

[0079] Assuming that p2 and p1 are a certain pressure range, and v2 and v1 are their corresponding specific volumes, equation (G) can be rewritten as:

[0080]

[0081] Combining equations (F) and (H), the volume time constants of the high-pressure air inlet chamber, the first-stage heat exchanger, and the pipes before and after the second-stage heat exchanger can be calculated as follows:

[0082]

[0083] For each expansion stage of the air turbine, the output power of each cylinder is: P K =Q K (h ink -h outk )(J)In the formula, P K is the output power of a certain section of turbine cylinder, kJ / s; Q K is the flow rate of this section, kg / s; h ink and h outk are the inlet and outlet enthalpies of this section, kJ / kg respectively.

[0084] From formula (J), the power coefficients of high, medium and low pressure cylinders can be calculated as follows:

[0085]

[0086] According to the calculation data of air turbine thermal balance and the fluid continuity equation, the natural overmodulation coefficient λ of high-pressure cylinder power is calculated to characterize the overmodulation phenomenon caused by the failure of high-pressure cylinder exhaust pressure to follow the adjustment in time due to the existence of reheat volume.

[0087]

[0088] In the formula, k is the adiabatic coefficient. For ideal gas, k = 1.4; ε is the high-pressure cylinder pressure ratio.

[0089] See also Figure 4 , establish a governor model that meets the actual engineering situation, which is used to accurately control the speed and load of the air turbine, and includes the limit link and rate limit link, and the proportional coefficient K G It is the inverse of the air turbine speed inequality, and is generally set to 24 to 25. The governor model consists of the speed limiter and the server. In this example, it is set to 25. The modeling parameters of other links are shown in Table 1.

[0090] Table 1

[0091]

[0092]

[0093] The above-established salt cavern thermodynamic dynamic model, air turbine model, and speed regulator model are integrated to obtain a three-stage expansion air turbine primary frequency modulation model that takes into account the thermodynamic characteristics of the salt cavern.

[0094] After calculating the primary frequency modulation model of the air turbine generator set, an improved PSO algorithm with an increased contraction factor is used to optimize the controller parameters. For the convenience of engineering application, a parallel PID is used, and its transfer function is as follows, where Kp is the proportional coefficient, Ki is the integral time constant, and Kd is the differential time constant, and the three are the parameters to be optimized. Thus, the primary frequency modulation control model of the three-stage expansion air turbine generator set is formed. The model includes a PID controller, an air turbine model, a speed regulator model, and a salt cavern thermodynamic dynamic model. The control loop excitation signal can be a small frequency difference disturbance, a large frequency difference step disturbance, or a simulation of the real frequency of the power grid. The control system performance evaluation uses the IAE index, that is, the absolute error integral index. The smaller the IAE index, the higher the accuracy of the system.

[0095]

[0096] An improved particle swarm algorithm is introduced to iteratively optimize the parameters of the PID controller. On the basis of the conventional standard PSO algorithm, a contraction factor is added to effectively control the flight speed of particles and stimulate the ability of particles to explore new areas, so that the algorithm can achieve an effective balance between global detection and local mining, and ensure the convergence of the algorithm. The particle speed update formula is as follows:

[0097]

[0098] where φ is called the shrinkage factor, C=c1+c2, and C>4.

[0099] In this embodiment, the number of particles is 20, the learning factor c1 is 2.8, the learning factor c2 is 2.2, and the number of iterations is 20. According to the algorithm steps, the improved particle swarm algorithm is used to optimize the parameters of the air turbine primary frequency modulation PID controller. The fitness value change curve during the iteration process is as follows: Figure 5 As shown, the parameters finally optimized are Kp=4.2583, Ki=6.0005, and Kd=1.0355.

[0100] According to GB / T 40595-2021 "Technical Regulations and Test Guidelines for Primary Frequency Regulation of Grid-connected Power Supply" and other relevant technical standards, a step disturbance test was carried out on the three-stage expansion air turbine closed-loop primary frequency regulation model, and the dynamic response indicators such as primary frequency regulation active power adjustment time, rise time, overshoot, and number of oscillations were statistically analyzed.

[0101] The decrease in salt cavern pressure and temperature during the primary frequency modulation period compared with those without the primary frequency modulation were statistically analyzed to evaluate the impact of the primary frequency modulation of the unit on the safe and stable operation of the salt cavern.

[0102] An effective slip of 15 rpm is applied to the primary frequency modulation control model in the embodiment of the present invention, and a primary frequency modulation amplitude limiting test is performed, and the active power target value is 0.1 pu, that is, 30 MW. Figure 6 In the slip step disturbance test, the primary frequency modulation active power adjustment time is about 20s, the rise time is about 2s, there is no overshoot, no oscillation, and the primary frequency modulation response dynamic characteristics are excellent. Therefore, the control parameters obtained by the improved particle swarm algorithm have fast dynamic response, no overshoot, small static deviation, high accuracy, and faster convergence in the process of setting value step response, which verifies the superiority of the improved algorithm.

[0103] See also Figure 7 , Figure 8In the energy release process, a primary frequency modulation test with the maximum slip step was applied in the time period from 20s to 100s. The primary frequency modulation model taking into account the thermodynamic characteristics of the salt cavern has the following characteristics: (1) Due to the use of a non-supplementary compressed air energy storage system, there is no external energy replenishment during the energy release and power generation process, and the salt cavern temperature and pressure ratio show a dynamic decrease phenomenon; (2) When the primary frequency modulation action is 80s, the flow rate entering the air turbine changes by about 100kg / s, the salt cavern pressure decreases by 1500Pa compared with the case without primary frequency modulation action, and the salt cavern temperature decreases by 0.02K compared with the case without primary frequency modulation action. The participation of the unit in primary frequency modulation has little effect on the safe and stable operation of the salt cavern.

Claims

1. A method for optimizing primary frequency modulation control parameters of a large air turbine generator set, characterized in that: The following steps are involved: Step 1: Establish a thermodynamic dynamic model of the salt cavern during the energy release process of a large compressed air energy storage generator set, and obtain a differential equation model that can characterize the dynamic change law of the salt cavern pressure ratio and temperature during the energy release process; In the formula, h c is the salt cavern wall heat transfer coefficient, w / m 2 K; A is the salt cavern wall area, m 2 ; T rw and T are the wall temperature and gas temperature, K respectively; c v is the specific heat at constant volume, J / (kg*K); c p is the specific heat at constant pressure J / kg*K; R g is the gas constant, 287 J / kg*K; Step 2, establish an air turbine model and obtain parameters in the model: according to the structure and size data of the three-stage expansion air turbine, the concentrated parameter method is used to obtain the volume time constant of the high-pressure air inlet chamber, the volume time constant of the pipes before and after the first-stage heat exchanger, and the volume time constant parameters of the pipes before and after the second-stage heat exchanger; Step 3, calculating the natural over-modulation coefficient λ of the high-pressure cylinder power; Step 4: Establish a governor model to accurately control the speed and load of the air turbine; the governor model includes a limit link and a rate limit link, and the proportional coefficient K G It is the inverse of the air turbine speed inequality, and is generally taken as 24 to 25; Step 5: Integrate the above-established salt cavern thermodynamic dynamic model, air turbine model, and speed regulator model to obtain a primary frequency regulation model of a large air turbine generator set that takes into account the thermodynamic characteristics of the salt cavern; Step 6: Introduce parallel PID, Its transfer function expression is: Among them, Kp is the proportional coefficient, Ki is the integral time constant, and Kd is the differential time constant, and the three are parameters to be optimized and set; thus, a primary frequency regulation control model of a large air turbine generator set is formed, and the primary frequency regulation control model of a large air turbine generator set includes a PID controller, an air turbine model, a speed regulator model, and a salt cavern thermodynamic dynamic model. The control loop excitation signal adopts a small frequency difference disturbance, a large frequency difference step disturbance, or a method of simulating the real frequency of the power grid; Step 7: Introduce an improved particle swarm algorithm to iteratively optimize the PID controller parameters, increase the shrinkage factor, and the particle speed update formula is as follows; where φ is called the shrinkage factor, C = c1 + c2, and C > 4; The control system performance evaluation uses the IAE index, that is, the integral absolute error index. The smaller the IAE index, the higher the accuracy of the system. Step 8. According to the above algorithm steps, set the number of particles, learning factor, and number of iterations to implement the improved particle swarm algorithm to optimize the parameters of the air turbine primary frequency modulation PID controller, and finally optimize the PID controller parameters Kp, Ki, and Kd. Step 9: Conduct a step disturbance test on the primary frequency regulation control model of the large air turbine generator set, and statistically analyze the dynamic response indicators of the primary frequency regulation active power regulation time, rise time, overshoot, and oscillation frequency. Step 10: Statistically analyze the change in the salt cavern pressure and the change in the salt cavern temperature during the primary frequency modulation action compared to the period without the primary frequency modulation action, and evaluate the impact of the unit's primary frequency modulation action on the safe and stable operation of the salt cavern.

2. The method for optimizing the primary frequency regulation control parameters of a large air turbine generator set according to claim 1, characterized in that In step 2, an air turbine model is established, and the parameters in the model are obtained as follows: According to the continuity equation, the time constant of gas flowing through the pipe is: Where T' is the time constant, s; p' is the constant pipeline pressure, Pa; Q' is the gas flow rate, kg / s; V is the pipeline volume, m 3 ; K is the density change caused by pressure change under constant temperature conditions, s 2 / m 2 .v s is the specific volume assuming constant temperature in a pipeline, m 3 / kg; t0 is the pipeline temperature, which is set to a constant value. Assuming that p2 and p1 are a certain pressure range, and v2 and v1 are their corresponding specific volumes, equation (5) can be rewritten as: Combining equations (4) to (6), the volume time constants of the high-pressure air inlet chamber, the first-stage heat exchanger, and the pipes before and after the second-stage heat exchanger can be calculated as follows: {T CH 、T RH 、T CO } (7) For each expansion stage of the air turbine, the output power of each cylinder is: P K =Q K (h ink -h outk ) (8) Where P K is the output power of a certain section of turbine cylinder, kJ / s; Q K is the flow rate of this section, kg / s; h ink and h outk are the inlet and outlet enthalpies of this section, kJ / kg respectively. From formula (8), the power coefficients of high, medium and low pressure cylinders can be calculated as follows: {F HP 、F IP 、F LP } (9) 3. The method for optimizing primary frequency modulation control parameters of a large air turbine generator set according to claim 1, characterized in that The natural overshoot coefficient λ of the high-pressure cylinder power is calculated in step 3 as follows: In the formula, k is the adiabatic coefficient. For ideal gas, k = 1.4; ε is the high-pressure cylinder pressure ratio.

4. The method for optimizing primary frequency modulation control parameters of a large air turbine generator set according to claim 1, characterized in that: In step 5, the control loop excitation signal adopts a small frequency difference disturbance, a large frequency difference step disturbance, or a method of simulating the real frequency of the power grid.

5. The method for optimizing primary frequency modulation control parameters of a large air turbine generator set according to claim 1, characterized in that: In step 9, the step disturbance test is performed by applying a large frequency difference disturbance signal to the primary frequency modulation control model of the large air turbine generator set to quantitatively analyze the dynamic characteristics of the primary frequency modulation of the large compressed air energy storage unit and the change rules of thermodynamic parameters such as salt cavern temperature, flow, pressure, etc.

6. A primary frequency modulation control model for a large air turbine generator set, characterized in that: The primary frequency modulation model is composed of a salt cavern thermodynamic dynamic model (1), an air turbine model (2), a speed regulator model (3), and a regulating valve (4). The primary frequency modulation model is added with a PID controller to realize a primary frequency modulation control model of a large air turbine generator set with closed-loop control. In the primary frequency modulation control model of the large air turbine generator set, an improved PSO algorithm (6) assigns values ​​to the PID controller (5) to determine control parameters. The speed regulator model (3) is connected to the regulating valve (4). The regulating valve (4) is respectively connected to the salt cavern thermodynamic dynamic model (1) and the air turbine model (2). The frequency difference signal is passed through a primary frequency modulation load compensation module (7) to generate a deviation between a primary frequency modulation power target value and an actual frequency modulation power, which is input into the PID controller (5). The PID controller (5) is connected to the primary frequency modulation model, and the primary frequency modulation model receives instructions from the PID controller (5).

7. The primary frequency modulation control model of a large air turbine generator set according to claim 6 is characterized in that: According to the structure and size data of the large air turbine model, the model time constants of the pipes before and after the first and second stage heat exchangers are calculated by the lumped parameter method. The thermodynamic dynamic model of the salt cavern in the energy release stage is established based on the basic equations of working fluid and energy balance.

Images