Oil and gas temperature control method and system for compressed air energy storage system

Abstract

The present invention discloses an oil and gas temperature control method for a compressed air energy storage system, the method is used for a compressed air energy storage system, the compressed air energy storage system includes a multi-stage compressor and a multi-stage oil and gas heat exchanger, the oil volume of the primary oil and gas heat exchanger and the final oil and gas heat exchanger are the same, the method includes the following steps: establishing a cascade control loop for controlling the outlet temperature of the final compressor; introducing an oil temperature correction amount to correct the outlet temperature setting value of the final oil and gas heat exchanger in real time; introducing a compressor air flow correction amount to correct the nonlinearity of the main regulator, and serving as a feedforward correction sub-regulator. The present invention also discloses an oil and gas temperature control system for a compressed air energy storage system. The oil and gas temperature control method and system for a compressed air energy storage system provided by the present invention can control both the outlet oil temperature and the intake air temperature within a reasonable range, has a simple structure, is easy to implement, and is suitable for engineering applications.

Description

Technical Field

[0001] The invention relates to an oil and gas temperature control method and system for a compressed air energy storage system, belonging to the technical field of large-scale physical energy storage. Background Art

[0002] my country has further made renewable energy a development priority for its energy system and proposed to increase the proportion of renewable energy, which means that it will gradually become the main source of incremental energy consumption; however, renewable energy has inherent disadvantages such as intermittency and instability, which makes it impossible for its power generation to quickly adjust the peak, which to some extent undermines the load balance of the power grid. Compressed air energy storage power generation, due to its large scale and strong flexibility, can enhance the power grid's ability to respond to faults and make up for the defect that renewable energy cannot adjust the peak, which is of great strategic significance to the construction of a strong and smart grid.

[0003] Due to the difficulty in manufacturing and installing high-temperature pressure vessels, as well as the operating temperature limit of the equipment, it means that a multi-stage compressor and multi-stage cooling method are required to obtain a higher gas storage pressure. Accurate and effective control strategies can ensure the smooth and efficient operation of the multi-stage compression and cooling thermal air energy storage system. Through the feedforward compensation control strategy, the temperature, pressure and other parameters of each stage of the compressor and the cooling material are guaranteed to be within a reasonable working range, so as to achieve coordinated control between multi-stage equipment, and ultimately ensure the safety and efficiency of the system.

[0004] At present, there is a certain foundation for research on compressor control at home and abroad, but the thermal inertia of multi-stage compressors and multi-stage heat exchanger systems is greater, and control research is not in-depth. Patent application number 202011611660.5 discloses "A method for controlling the inlet temperature of cascade compressors for compressed air energy storage power stations". This patent uses oil temperature as the control target and adjusts the air temperature through nonlinear functions. The disadvantage is that using oil temperature as the control target sacrifices the accuracy of air temperature, and the use of nonlinear functions to adjust the air temperature is prone to over-adjustment or lag. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide an oil and gas temperature control method and system for a compressed air energy storage system, which fills the gap in the current temperature control methods of multi-stage compressors and multi-stage heat exchangers, and can control both the outlet oil temperature and the intake air temperature within a reasonable range. It has a simple structure, is easy to implement, and is suitable for engineering applications.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for controlling oil and gas temperature in a compressed air energy storage system, the method being used in a compressed air energy storage system, the compressed air energy storage system comprising a multi-stage compressor and a multi-stage oil and gas heat exchanger, which are a primary compressor, a primary oil and gas heat exchanger, an intermediate compressor, a final oil and gas heat exchanger and a final compressor in sequence, the primary oil and gas heat exchanger and the final oil and gas heat exchanger having the same oil volume, the method comprising the following steps:

[0008] Establish a cascade control loop to control the outlet temperature of the final compressor;

[0009] Introduce oil temperature correction to correct the set value of the outlet temperature of the final oil-gas heat exchanger in real time;

[0010] The compressor air flow correction is introduced to correct the nonlinearity of the main regulator and serves as a feedforward correction sub-regulator.

[0011] The cascade control loop includes a main regulator, a sub-regulator, an oil valve, a primary oil-gas heat exchanger and a final oil-gas heat exchanger connected in sequence. The main regulator uses the outlet temperature of the final oil-gas heat exchanger as the set value, collects the real-time outlet temperature of the final oil-gas heat exchanger for control, and the sub-regulator uses the outlet temperature of the primary oil-gas heat exchanger as the set value, and uses the oil valve as a sub-loop regulator to adjust the outlet temperature of the primary oil-gas heat exchanger.

[0012] The oil temperature correction value Y(x) is a quadratic equation obtained by fitting the outlet oil temperature and outlet gas temperature data. The outlet temperature of the final oil-gas heat exchanger has an allowable range [T o,min , T o,max ], T o,min and T o,max Represent the minimum outlet temperature and the maximum outlet temperature respectively. When the outlet oil temperature is lower than T o,min +3, the outlet temperature setting value is increased. When the outlet oil temperature is higher than T o，max -3, reduce the outlet temperature setting value.

[0013] The feedforward controller F(x) of the main regulator is fitted according to the change in air flow, the change in required oil volume and the outlet temperature. When the air flow increases or decreases, the corresponding oil volume needs to be increased or decreased to obtain the same outlet temperature.

[0014] The feedforward controller f(x) of the sub-regulator is fitted according to the change in air flow and the change in required oil volume. When the air flow increases or decreases, the corresponding oil volume needs to be increased or decreased to obtain the same outlet temperature.

[0015] The compressed air flow correction amount corrects the nonlinearity of the main regulator as follows: the controlled object is converted into a linear part and a nonlinear part.

[0016] Af (z -1 )y(k+1)=B f (z -1 ) PID (k)+γ(k) (1)

[0017] In the formula, y(k+1) represents the controlled output at time k+1, γ(k) is the nonlinear part, satisfying y(k) represents the controlled output at time k, is the linear model output, u PID (k) represents the output of the main PID controller; z -1 is the unit hysteresis operator; A f , B f Yes -1 Polynomial of:

[0018]

[0019] a1 to and b0 to represents the decomposition coefficients of the linear model;

[0020] The nonlinear main PID controller is expressed as:

[0021] u PID (k) = u PID (k-1)+K P [e(k)-e(k-1)] +K I e(k)+K D [e(k)-2e(k-1)+e(k-2)]+K no γ(k) (3)

[0022] K I , K P , K D and K no They represent the integral, proportional, differential and nonlinear components of the main PID controller respectively, and e(k) represents the controlled quantity deviation;

[0023] Set e(k)=y set Substituting (k)-y(k) into formula (3), we can get:

[0024]

[0025] Among them, y set (k) represents the set value of the controlled quantity,

[0026]

[0027] An oil and gas temperature control system for a compressed air energy storage system includes a cascade control loop, an oil temperature correction module and a compressor air flow correction module. The cascade control loop includes a main regulator, a sub-regulator, an oil valve, a primary oil and gas heat exchanger and a final oil and gas heat exchanger connected in sequence. The main regulator adjusts the outlet temperature of the final oil and gas heat exchanger, and the sub-regulator adjusts the outlet temperature of the primary oil and gas heat exchanger through the oil valve. The oil temperature correction module is used to introduce the oil temperature correction amount into the cascade control loop, and the compressor air flow correction module is used to introduce the compressor air flow correction amount into the cascade control loop.

[0028] Beneficial effects of the invention: The oil and gas temperature control method and system for a compressed air energy storage system provided by the invention fills the gap in the current temperature control methods for multi-stage compressors and multi-stage heat exchangers. When the outlet temperature of the final oil and gas heat exchanger deviates from the set value, it can be quickly corrected back by adjusting the oil valve through the cascade loop. If the oil temperature exceeds the limit during the oil valve adjustment process, the outlet temperature setting value will be adjusted so that the outlet oil temperature and the outlet air temperature are both controlled within a reasonable range. The controller has a simple structure and is easy to implement. In addition, the present invention proposes a solution to the system nonlinearity and thermal inertia problems. The nonlinear problem is solved by a PID method with a nonlinear correction function and a feedforward function correction of the outlet air flow rate. The thermal inertia of the controlled object is reduced by the cascade PID, and the controller is made to act in advance by the feedforward function to solve the thermal inertia problem, which is more practical in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of an oil and gas temperature control method for a compressed air energy storage system according to the present invention;

[0030] Figure 2 A control diagram of the outlet temperature of compressed air energy storage when the control method of the present invention does not reach the temperature limit of the thermal oil;

[0031] Figure 3 This is a control diagram of the compressed air energy storage outlet temperature when the control method of the present invention reaches the lower limit of the thermal oil temperature. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the protection scope of the present invention.

[0033] like Figure 1As shown, the present invention discloses an oil and gas temperature control method for a compressed air energy storage system. The method is used for a compressed air energy storage system. The compressed air energy storage system includes a multi-stage compressor and a multi-stage oil and gas heat exchanger, which are a primary compressor, a primary oil and gas heat exchanger, an intermediate compressor, a final stage oil and gas heat exchanger and a final stage compressor in sequence. The oil volume of the primary oil and gas heat exchanger and the final stage oil and gas heat exchanger is the same.

[0034] The control method of the present invention comprises the following steps:

[0035] A cascade control loop is established to control the outlet temperature of the final compressor. The cascade control loop includes a main regulator, a sub-regulator, an oil valve, a primary oil-gas heat exchanger, and a final oil-gas heat exchanger connected in sequence. The main regulator uses the outlet temperature of the final oil-gas heat exchanger as the set value, collects the real-time outlet temperature of the final oil-gas heat exchanger for control, and the sub-regulator uses the outlet temperature of the primary oil-gas heat exchanger as the set value, and uses the oil valve as the sub-loop regulator to adjust the outlet temperature of the primary oil-gas heat exchanger. When the outlet temperature of the final oil-gas heat exchanger just deviates from the set value, the controller first acts on the sub-loop. The sub-loop has a short delay time and small inertia. The oil valve quickly adjusts the outlet temperature of the primary oil-gas heat exchanger, which directly affects the outlet temperature of the final oil-gas heat exchanger. This loop can solve the problem of long delay time and large inertia in the process of the oil valve controlling the outlet temperature of the final heat exchanger.

[0036] The oil temperature correction is introduced to correct the outlet temperature setting value of the final oil-gas heat exchanger in real time. The oil temperature correction value Y(x) is a quadratic equation obtained by fitting the outlet oil temperature and outlet air temperature data. The outlet temperature of the final oil-gas heat exchanger has an allowable range [T o，min , T o，max ], T o，min and T o，max Represent the minimum outlet temperature and the maximum outlet temperature respectively. In this embodiment, T o，min and T o，max The values ​​are 127℃ and 154℃ respectively. The outlet temperature of oil has an allowable range of [127, 154]℃. When the oil temperature is lower than 130℃, the set value of the outlet temperature is increased. When the oil temperature is higher than 151℃, the set value of the outlet temperature is reduced.

[0037] The compressor air flow correction is introduced to correct the nonlinearity of the main regulator and serve as a feedforward correction sub-regulator. The feedforward controller F(x) of the main regulator is fitted according to the change in air flow, the change in required oil volume and the outlet temperature. When the outlet temperature is 180℃~200℃, F(x)=3x 2 +5.6x+2, x is the gas flow rate, when the outlet temperature is 160℃~180℃, F(x)=2x 2+3.5x+4. When the air flow increases or decreases, the oil volume needs to be increased or decreased accordingly to obtain the same outlet temperature.

[0038] The feedforward controller f(x) of the sub-regulator is fitted according to the change in air flow and the change in required oil volume. f(x) = 0.8x 2 +1.2x+0.5. When the air flow increases or decreases, the oil volume needs to be increased or decreased accordingly to obtain the same outlet temperature.

[0039] The compressed air flow correction amount corrects the nonlinearity of the main regulator as follows: the controlled object is converted into a linear part and a nonlinear part.

[0040] A f (z -1 )y(k+1)=B f (z -1 ) PID (k)+γ(k) (1)

[0041] In the formula, y(k+1) represents the controlled output at time k+1, γ(k) is the nonlinear part, satisfying y(k) represents the controlled output at time k, is the linear model output, u PID (k) represents the output of the main PID controller; z -1 is the unit hysteresis operator; A f , B f Yes -1 Polynomial of:

[0042]

[0043] a1 to and b0 to represents the decomposition coefficients of the linear model;

[0044] The nonlinear main PID controller is expressed as:

[0045] u PID (k) = u PID (k-1)+K P [e(k)-e(k-1)] +K I e(k)+K D [e(k)-2e(k-1)+e(k-2)]+K no γ(k) (3)

[0046] K I , K P , K D and K noRespectively represent the integral, proportional, differential and nonlinear components of the main PID controller, where K D It is obtained by identification calculation of compressed air flow. e(k) represents the deviation of the controlled quantity;

[0047] Set e(k)=y set Substituting (k)-y(k) into formula (3), we can get:

[0048]

[0049] Among them, y set (k) represents the set value of the controlled quantity,

[0050]

[0051] The present invention also discloses an oil and gas temperature control system for a compressed air energy storage system, comprising a cascade control loop, an oil temperature correction module and a compressor air flow correction module, the cascade control loop comprising a main regulator, a sub-regulator, an oil valve, a primary oil and gas heat exchanger and a final oil and gas heat exchanger connected in sequence, the main regulator adjusts the outlet temperature of the final oil and gas heat exchanger, the sub-regulator adjusts the outlet temperature of the primary oil and gas heat exchanger through the oil valve, the oil temperature correction module is used to introduce the oil temperature correction amount into the cascade control loop, and the compressor air flow correction module is used to introduce the compressor air flow correction amount into the cascade control loop.

[0052] When the oil and gas temperature control method of the present invention is used for control, when the oil temperature limit is not reached, it can be obtained Figure 2 The control effect. Figure 2 (a) It can be seen that the air temperature of the final heat exchanger can return to the set value in about 250s, and the control is smooth without oscillation. Figure 2 (b) It can be seen that the heat transfer oil flow rate reaches stability at around 150s. When the oil temperature limit is reached, it can be obtained Figure 3 The control effect. Figure 3 (a) It can be seen that the outlet temperature of the final heat exchanger reaches stability at around 400s. Figure 3 (b) It can be seen that the outlet temperature of the heat transfer oil reaches stability at around 400s. Figure 3 (c) It can be seen that the heat transfer oil flow rate reaches stability at around 300s. The control method of the present application can effectively ensure that the outlet gas temperature and the outlet oil temperature are within a reasonable range with a fast response speed.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for controlling oil and gas temperature in a compressed air energy storage system, characterized in that: The compressed air energy storage system comprises a multi-stage compressor and a multi-stage oil-gas heat exchanger, the oil volume of the primary oil-gas heat exchanger and the final oil-gas heat exchanger is the same; a cascade control loop is established to control the outlet temperature of the final compressor of the compressed air energy storage system, and the method comprises: The oil temperature correction value is introduced into the established cascade control loop to correct the outlet temperature setting value of the final oil-gas heat exchanger in real time; The compressor air flow correction is introduced into the established cascade control loop to correct the nonlinearity of the main regulator and serve as a feedforward correction sub-regulator; The nonlinearity correction of the main regulator is as follows: the controlled object is converted into a linear part and a nonlinear part. （1） In the formula, represents the controlled quantity output at time k+1, is the nonlinear part, satisfying , represents the controlled quantity output at time k, is the linear model output, Represents the main PID controller output; is the unit hysteresis operator; , yes Polynomial of: （2） arrive and b0 to represents the decomposition coefficients of the linear model; The nonlinear main PID controller is expressed as: （3） , , and Represent the integral, proportional, differential and nonlinear components of the main PID controller, Indicates the deviation of the controlled quantity; Will Substituting into formula (3), we can get: （4） Among them, y set (k) represents the set value of the controlled quantity, （5）。 2. The oil and gas temperature control method for a compressed air energy storage system according to claim 1, characterized in that: The compressed air energy storage system comprises a primary compressor, a primary oil-gas heat exchanger, a mid-stage compressor, a final-stage oil-gas heat exchanger and a final-stage compressor in sequence.

3. The oil and gas temperature control method for a compressed air energy storage system according to claim 1, characterized in that: The cascade control loop includes a main regulator, a sub-regulator, an oil valve, a primary oil-gas heat exchanger and a final oil-gas heat exchanger connected in sequence. The main regulator uses the outlet temperature of the final oil-gas heat exchanger as the set value, collects the real-time outlet temperature of the final oil-gas heat exchanger for control, and the sub-regulator uses the outlet temperature of the primary oil-gas heat exchanger as the set value, and uses the oil valve as a sub-loop regulator to adjust the outlet temperature of the primary oil-gas heat exchanger.

4. The oil and gas temperature control method for a compressed air energy storage system according to claim 1, characterized in that: The oil temperature correction value Y(x) is a quadratic equation obtained by fitting the outlet oil temperature and outlet gas temperature data. The outlet temperature of the final oil-gas heat exchanger has an allowable range [T o,min , T o,max ], T o,min and T o,max represent the minimum outlet temperature and the maximum outlet temperature respectively, When the outlet oil temperature is lower than T o,min +3, the outlet temperature setting value is increased. When the outlet oil temperature is higher than T o,max -3, reduce the outlet temperature setting value.

5. The oil and gas temperature control method for a compressed air energy storage system according to claim 1, characterized in that: The feedforward controller F(x) of the main regulator is fitted according to the change in air flow, the change in required oil volume and the outlet temperature. When the air flow increases or decreases, the corresponding oil volume is increased or decreased to obtain the same outlet temperature.

6. The oil and gas temperature control method for a compressed air energy storage system according to claim 1, characterized in that: The feedforward controller f(x) of the sub-regulator is fitted according to the change in air flow and the change in required oil volume. When the air flow increases or decreases, the corresponding oil volume is increased or decreased to obtain the same outlet temperature.

7. An oil and gas temperature control system for a compressed air energy storage system, characterized in that: An oil and gas temperature control method for a compressed air energy storage system as described in claim 1 includes a cascade control loop, an oil temperature correction module and a compressor air flow correction module, the cascade control loop includes a main regulator, a sub-regulator, an oil valve, a primary oil and gas heat exchanger and a final oil and gas heat exchanger connected in sequence, the main regulator adjusts the outlet temperature of the final oil and gas heat exchanger, the sub-regulator adjusts the outlet temperature of the primary oil and gas heat exchanger through the oil valve, the oil temperature correction module is used to introduce the oil temperature correction amount into the cascade control loop, and the compressor air flow correction module is used to introduce the compressor air flow correction amount into the cascade control loop.

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