A method for modeling and controlling a ram air turbine power generation system

Abstract

The application relates to the technical field of power systems, and discloses a modeling and control method of a ram air turbine power generation system. In the modeling process of the ram air turbine power generation system, the characteristic curve of the turbine, the characteristic of the permanent magnet synchronous generator and the cavity effect are considered. The application solves the problems of low precision, slow adjustment and large overshoot in the prior art.

Description

Technical Field

[0001] This invention relates to the field of power system technology, specifically a modeling and control method for a ram air turbine power generation system. Background Technology

[0002] With the increasing power demands of aircraft pods and other equipment, ram-air turbine generator systems, decoupled from the aircraft's electrical system, have received growing attention. When the aircraft operates a ram-air turbine generator system, the intake of ram-air air is regulated by a flow control device. The rotating impeller then drives a synchronous generator to provide power to the equipment, and the air is discharged through the exhaust duct after passing through the central air duct. In actual operation, the two most important performance parameters of the ram-air generator system are voltage and speed. For voltage regulation, the system primarily relies on a fully controlled rectifier controller for voltage rectification. For speed regulation, PID control is generally used in practice—the difference between the actual speed and the set speed is input as the deviation into the PID control component, and the resulting control signal is used to adjust the intake air volume through the turbine guide vanes. Although PID control can give the system good static performance, when the downstream load is a step or repetitive T / R load, the load changes are relatively drastic. When the turbine and generator are coaxially connected, their respective working performances have a strong coupling relationship. The cavity effect caused by the imbalance of inlet and outlet flow of the turbine cannot be ignored. If only PID control is used, problems such as slow adjustment and large overshoot will occur, resulting in a decline in power supply quality and difficulty in normal operation of downstream electrical equipment.

[0003] Patent CN115037023A discloses a ramjet turbine autonomous power generation system and its energy management method. This system stabilizes under step loads by adjusting the flow rate of the damper and supplementing it with batteries and supercapacitors. However, this system is primarily based on an external bypass turbine system. The invention does not model the characteristic curves of key components such as the turbine, resulting in low accuracy. Furthermore, relying solely on PID control for feedback adjustment of system speed leads to high-frequency fluctuations in the speed feedback value, causing problems such as slow adjustment and large overshoot. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a modeling and control method for a ram air turbine power generation system, which solves the problems of low accuracy, slow adjustment, and large overshoot in existing technologies.

[0005] The technical solution adopted by the present invention to solve the above problems is:

[0006] A modeling method for a ram air turbine power generation system is proposed, which considers the turbine characteristic curve, permanent magnet synchronous generator characteristics, and cavity effect during the modeling process of the ram air turbine power generation system.

[0007] As a preferred technical solution, the relationship between the flow difference and pressure difference between the inlet and outlet of the cavity during the dynamic process is obtained by changing the flow rate before and after the cavity. Finally, the turbine power is obtained by combining the turbine characteristic lookup table. At the same time, the port voltage and load power characteristics are obtained based on the permanent magnet synchronous generator model. Then, the difference between the turbine power and the load power is input into the rotor dynamics model to obtain the speed at the next moment, thus realizing the modeling of the ram air turbine power generation system.

[0008] As a preferred technical solution, the steps include:

[0009] S1, using altitude and speed as initial input conditions, calculates the total temperature and total pressure conditions of the air intake;

[0010] S2, the flow regulating device is equivalent to a throttle valve with adjustable opening, and the flow regulating device can adjust the intake air volume to 0% to 100% of the standard intake air volume;

[0011] S3, a cavity is set between the turbine and the exhaust port to calculate the cavity effect under the imbalance of inlet flow and outlet flow;

[0012] S4, the outlet pressure of the cavity is used as the turbine outlet pressure condition;

[0013] S5 provides the turbine's outlet total pressure, total temperature, and output power.

[0014] S6: The gas discharged from the turbine passes through the middle air passage, resulting in pressure loss, and then enters the exhaust passage.

[0015] S7, the generator and turbine share a single shaft, the turbine shaft rotates at the same speed as the generator shaft, and the port voltage and load power characteristics are obtained based on the permanent magnet synchronous generator model;

[0016] S8 inputs the difference between turbine power and load power into the rotor dynamics model to obtain the speed variation of the system, and uses the speed as the input of the turbine until the speed reaches a steady state; the method for determining the steady state is set in advance.

[0017] As a preferred technical solution, the method used in step S3 to calculate the cavity effect under the imbalance of inlet and outlet flow rates is as follows:

[0018] Setting: Cavity inlet flow rate W 1,in Export flow W 1,in The volume is V c1 Temperature T t1The pressure is P t1 The pressure change within the cavity is due to Calculated;

[0019] Where R represents the gas constant and t represents time.

[0020] As a preferred technical solution, in step S5, the method for obtaining the turbine's outlet total pressure, total temperature, and output power is as follows:

[0021] The turbine characteristic curve is used as a turbine characteristic lookup table. The rotational speed is converted based on the total temperature of the incoming flow, the reference temperature, and the reference rotational speed. The turbine outlet pressure conditions given by the cavity and the rotor speed given by the rotor dynamics model are combined. Based on the existing turbine characteristic lookup table, the functional relationship between the pressure drop ratio and the converted flow rate and efficiency under different rotational speed conditions is interpolated and fitted.

[0022] A control method for a ram air turbine power generation system is provided, which adopts the aforementioned modeling method for a ram air turbine power generation system and adds a compensation term that considers step and repetitive frequency load current feedforward in the speed feedback control loop.

[0023] As a preferred technical solution, the steps include:

[0024] A1. Construct a speed feedback control loop, feed back the actual speed signal measured at the generator's rotary transformer to the controller, calculate the difference between the actual speed signal and the set speed signal to obtain the speed deviation, and input the speed deviation into the speed PID feedback control to obtain the control quantity ε1.

[0025] A2, after speed feedback control, add current feedforward control;

[0026] A3. Determine whether the load type is a step load or a repetitive pulse load, and calculate the equivalent load current I. s ;

[0027] A4, Equivalent load current I s The compensation amount Δε for the PID control quantity ε1 of the speed is obtained through the steady-state control equation.

[0028] A5, sum ε1 and Δε as the control input for the flow regulating valve, thereby adjusting the intake volume of the turbine guide vanes;

[0029] A6, due to the change in airflow, the updated intake conditions are input into the ramjet turbine dynamics model based on cavity dynamics for iterative calculation.

[0030] As a preferred technical solution, the method for obtaining the load current in step A3 is as follows:

[0031] For step loads, Is This is the steady-state current value after the step jump;

[0032] As a preferred technical solution, the method for obtaining the load current in step A3 is as follows:

[0033] For high-frequency loads, for inertial systems like rotating shafts, based on the principle of PWM impulse equivalence, the high-frequency pulse load is calculated according to I... s =I m ×D+I l The equivalent processing of ×(1-D) transforms the high-frequency load into a stable load, providing the feedforward current value I. s ;

[0034] Among them, I m I represents the peak current of the pulsed load. l The base current of the pulsed load is represented by , and D represents the duty cycle.

[0035] As a preferred technical solution, the condition for adopting current feedforward is one of the following:

[0036] 1) The electrical load is a step load of T / R radar type;

[0037] 2) The electrical load is a T / R radar type repetition frequency load.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] (1) The present invention adopts a ram air turbine component-level modeling method based on cavity dynamics. Under the condition of large changes in electrical load, it fully considers the cavity effect of the turbine inside the duct and combines the turbine performance curve lookup table to make the model more accurate in reflecting the dynamic characteristics of the whole system.

[0040] (2) The present invention adopts a control method for a ram air turbine generator system with current feedforward. By adding a current feedforward loop to the speed feedback PID control loop, especially for pulse loads, the current feedforward value is selected as the current feedforward value obtained by using the PWM impulse equivalent principle. Then the current feedforward value is input into the steady-state control model to generate the compensation value of the flow regulation control PID signal. By adopting the current feedforward combined with speed feedback, the dynamic adjustment speed of the system speed is improved and the overshoot is reduced. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the ram air turbine power generation system based on the cavity effect used in this invention.

[0042] Figure 2 This is a flowchart of the component-level modeling process for a ram air turbine power generation system based on the cavity effect, which is used in this invention.

[0043] Figure 3 This is a flowchart of the speed feedback control process after adding current feedforward, which is used in this invention. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0045] Example 1

[0046] like Figures 1 to 3 As shown, the purpose of this invention is to provide a modeling and control method for a ram air turbine power generation system, specifically:

[0047] 1) A component-level modeling method for ram air turbine power generation system based on cavity dynamics fully considers the characteristic curve of the turbine and the cavity effect. Using component-level modeling, the accuracy is higher.

[0048] 2) The speed control method with current feedforward is adopted. The load current feedforward compensation term is added to the speed feedback control loop. The influence of step and pulse load change characteristics on the shaft system is fully considered, which improves the dynamic adjustment speed of the system under dynamic load and reduces the overshoot.

[0049] A component-level modeling method for ram-air turbine power generation systems based on cavity dynamics. A typical cavity-type ram-air turbine power generation system is shown below. Figure 1 As shown, starting from the intake direction, the main components are, in sequence, the intake duct, the flow regulation device, the turbine, the central air duct (containing a generator), and the exhaust duct. During dynamic load operation, pressure changes occur due to the accumulation and release of gas mass and energy within the cavity, causing the inlet and outlet parameters of the airflow to become unequal and satisfying certain dynamic equations. Considering the structural characteristics of the internal duct ram air turbine generator system, the cavity location in the system should be after the turbine, fully considering the pressure changes caused by the accumulation and release of gas mass and energy within the cavity during dynamic processes. By analyzing the flow rate changes before and after the cavity, the relationship between the inlet / outlet flow rate difference and the pressure difference during dynamic processes is obtained. Finally, by combining the characteristic lookup table of the turbine component, the turbine power is obtained. The difference between the turbine power and the load electrical power is then input into the rotor dynamic equation to obtain the rotational speed at the next moment, completing the system modeling and analysis. Figure 2 As shown.

[0050] The specific method is as follows:

[0051] a) Using altitude and speed as initial input conditions, calculate the total temperature and total pressure conditions of the air intake;

[0052] b) The flow regulating device is equivalent to an adjustable throttle valve, which can adjust the intake air volume to 0% to 100% of the standard intake air volume;

[0053] c) A cavity is set between the turbine and the exhaust port to calculate the cavity effect under inlet and outlet flow imbalance. The inlet flow rate W of the cavity is set. 1,in Export flow W 1,in The volume is V c1 Temperature T t1 The pressure is P t1 The pressure change within the cavity can be caused by Calculated;

[0054] d) Use the outlet pressure of the cavity as the turbine outlet pressure condition;

[0055] e) Use the turbine's characteristic curve—flow-pressure ratio-speed-efficiency curve—as a characteristic lookup table, and convert the speed based on the total temperature of the incoming flow, reference temperature, and reference speed. Combine the pressure output given by the cavity and the speed given by the rotor dynamics, and interpolate and fit the existing turbine characteristic lookup table to calculate the functional relationship between the pressure ratio and the converted flow and efficiency under different speed conditions, so as to obtain the turbine's outlet total pressure, total temperature, and output power.

[0056] f) The gas discharged from the turbine passes through the middle air passage, resulting in a certain pressure loss, and then enters the exhaust passage;

[0057] g) The generator and turbine are coaxial, and the port voltage and load power characteristics can be obtained based on the synchronous generator model;

[0058] h) Input the turbine power and load power into the rotor dynamics model to obtain the speed variation of the system, and use the speed as the input of the turbine until the speed reaches the final stability.

[0059] A control method for a ram-air turbine power generation system with current feedforward. When the ram-air turbine power generation system is operating under varying loads, this invention considers the conditions for employing current feedforward:

[0060] 1) Since the bus voltage remains basically constant, the changes in electrical load can be measured by the current, but the system cannot directly control the magnitude of the load current.

[0061] 2) Because the electrical load is a T / R radar type load, the load changes extremely frequently;

[0062] 3) Simply using speed PID feedback control cannot effectively overcome the effects of load disturbances, and the system also requires high speed control accuracy.

[0063] This invention takes into account that feedforward control, as an open-loop control method, can be compensated by the disturbance state of the load current, thus significantly improving the system's response speed. However, since the load current disturbance can only affect the rotational speed itself, it needs to be combined with feedback control to overcome other forms of disturbance, such as the influence of changes in inlet airflow conditions.

[0064] The specific method of current feedforward combined with speed PID feedback control proposed in this invention is as follows:

[0065] a) The speed feedback control loop is as follows: the actual speed signal measured at the generator's rotary transformer is fed back to the controller. The speed deviation can be obtained by subtracting the actual speed signal from the set speed signal. The speed deviation is then input into the speed PID control to obtain the control quantity ε1.

[0066] b) After the speed feedback control loop, add current feedforward control, selecting the current as the equivalent DC bus current value I. s At this point, it is necessary to determine whether the electrical load is a recurring load. For step loads, I s This is the steady-state current value after the step jump; for a repetitive frequency load, assume I... m I is the peak current of the pulsed load. l Let I be the base current of the pulse load, and D be the duty cycle. For inertial systems like rotating shafts, based on the principle of PWM impulse equivalence, the repetitive frequency load can be calculated as I... s =I m ×D+I l The equivalent processing of ×(1-D) transforms the high-frequency load into a stable load, providing the feedforward current value I. s ;

[0067] c) The equivalent current value is used to obtain the compensation amount Δε of the speed PID control quantity ε1 through the steady-state control equation;

[0068] d) Summing ε1 and Δε is used as the control input for the flow regulating valve, thereby adjusting the intake volume of the turbine guide vanes;

[0069] e) Due to the change in airflow, the updated intake conditions are input into the ram air turbine dynamics model based on cavity dynamics for iterative calculation.

[0070] The technical effects of this invention are as follows:

[0071] (1) The present invention adopts a ram air turbine component-level modeling method based on cavity dynamics. Under the condition of large changes in electrical load, it fully considers the cavity effect of the turbine inside the duct and combines the turbine performance curve lookup table to make the model more accurate in reflecting the dynamic characteristics of the whole system.

[0072] (2) The present invention adopts a control method for a ram air turbine generator system with current feedforward. By adding a current feedforward loop to the speed feedback PID control loop, especially for pulse loads, the current feedforward value is selected as the current feedforward value obtained by using the PWM impulse equivalent principle. Then the current feedforward value is input into the steady-state control model to generate the compensation value of the flow regulation control PID signal. By adopting the current feedforward combined with speed feedback, the dynamic adjustment speed of the system speed is improved and the overshoot is reduced.

[0073] Example 2

[0074] like Figures 1 to 3 As shown, as a further optimization of Embodiment 1, this embodiment also includes the following technical features based on Embodiment 1:

[0075] The workflow of a ram air turbine system switching from a steady-state load to a high-frequency load is as follows: 1) Establish a ram air turbine system model considering the cavity effect according to the model composition, size, and working conditions; 2) Before the switch, the DC bus carries a steady-state current of 82A, and after the switch, it carries a high-frequency load of 1kHz with a duty cycle of 50%, a peak DC bus current of 82A, and a base current of 42A. At this time, using the PWM equivalent principle, the current feedforward value is set to 82×50%+42×50%=62A; 3) After the switch, due to the sudden load drop, the entire system is in an accelerated state. The speed deviation first enters the PID controller to generate the flow regulating valve control quantity ε1; 4) Input the current feedforward value into the steady-state control model to calculate the compensation quantity Δε of the flow regulating valve control quantity; 5) Sum ε1 and Δε as the total control quantity of the flow regulating valve, and then adjust the intake valve opening, so that the control system gradually reaches stability. Compared with the pure PID control algorithm, it was found that the system speed regulation speed increased by 30%, and the overshoot was reduced by more than 50%.

[0076] As described above, the present invention can be implemented well.

[0077] All features disclosed in all embodiments of this specification, or steps in all methods or processes implied in the disclosure, may be combined and / or extended or replaced in any way, except for mutually exclusive features and / or steps.

[0078] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Based on the technical essence of the present invention, any simple modifications, equivalent substitutions, and improvements made to the above embodiments within the spirit and principles of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A modeling method for a ram-air turbine power generation system, characterized in that, In the modeling of the ram air turbine power generation system, the characteristic curve of the turbine, the characteristics of the permanent magnet synchronous generator, and the cavity effect are considered. The aforementioned modeling method for a ram air turbine power generation system includes the following steps: S1, using altitude and speed as initial input conditions, calculates the total temperature and total pressure conditions of the air intake; S2, which equates the flow regulating device to an adjustable flow regulating valve, can adjust the intake air volume to 0%~100% of the standard intake air volume; S3, a cavity is set between the turbine and the exhaust port to calculate the cavity effect under the imbalance of inlet flow and outlet flow; S4, the outlet pressure of the cavity is used as the turbine outlet pressure condition; S5 provides the turbine's outlet total pressure, total temperature, and output power. S6: The gas discharged from the turbine passes through the middle air passage, resulting in pressure loss, and then enters the exhaust passage. S7, the generator and turbine share a single shaft, and the turbine shaft rotates at the same speed as the generator shaft. The port voltage and load power characteristics are obtained based on the permanent magnet synchronous generator model. S8 inputs the difference between turbine power and load power into the rotor dynamics model to obtain the speed variation of the system, and uses the speed as the input of the turbine until the speed reaches a steady state; the method for determining the steady state is set in advance.

2. The modeling method for a ram air turbine power generation system according to claim 1, characterized in that, By observing the flow rate changes before and after the cavity, the relationship between the flow rate difference and pressure difference at the inlet and outlet of the cavity during the dynamic process is obtained. Finally, combined with the turbine characteristic lookup table, the turbine power is obtained. At the same time, based on the permanent magnet synchronous generator model, the port voltage and load power characteristics are obtained. Then, the difference between the turbine power and the load power is input into the rotor dynamics model to obtain the rotational speed at the next moment, thus realizing the modeling of the ram air turbine power generation system.

3. The modeling method for a ram air turbine power generation system according to claim 1, characterized in that, In step S3, the method used to calculate the cavity effect under the imbalance of inlet and outlet flow rates is as follows: Settings: Cavity inlet flow rate W 1,in Export flow W 1,out The volume is V c1 Temperature is T t1 Pressure is P t1 The pressure change within the cavity is due to Calculated; in, R Represents the gas constant. t Indicates time.

4. The modeling method for a ram air turbine power generation system according to claim 3, characterized in that, In step S5, the method for obtaining the turbine's outlet total pressure, total temperature, and output power is as follows: The turbine characteristic curve is used as a turbine characteristic lookup table. The rotational speed is converted based on the total temperature of the incoming flow, the reference temperature, and the reference rotational speed. The turbine outlet pressure conditions given by the cavity and the rotor speed given by the rotor dynamics model are combined. Based on the existing turbine characteristic lookup table, the functional relationship between the pressure drop ratio and the converted flow rate and efficiency under different rotational speed conditions is interpolated and fitted.

5. A control method for a ram air turbine power generation system, characterized in that, The modeling method for a ram air turbine power generation system according to any one of claims 1 to 4 incorporates a compensation term that considers step and repetitive frequency load current feedforward in the speed feedback control loop. The control method for a ram air turbine power generation system includes the following steps: A1. Construct a speed feedback control loop, feeding back the actual speed signal measured at the generator's rotary transformer to the controller. The difference between the actual speed signal and the set speed signal is used to obtain the speed deviation, which is then input into the speed PID feedback control to obtain the control quantity. ε 1; A2, after speed feedback control, add current feedforward control; A3. Determine whether the load type is a step load or a repetitive pulse load, and calculate the equivalent load current. I s ; A4, Equivalent load current I s The PID control quantity of the rotational speed is obtained through the steady-state control model. ε 1 compensation amount Δ ε ; A5, will ε 1 and Δ ε The summation is used as the control input for the flow regulating valve, thereby adjusting the intake volume of the turbine guide vanes; A6, due to the change in airflow, the updated intake conditions are input into the ramjet turbine dynamics model based on cavity dynamics for iterative calculation.

6. The control method for a ram air turbine power generation system according to claim 5, characterized in that, In step A3, the method for obtaining the load current is as follows: For step loads I s This is the steady-state current value after the step jump.

7. The control method for a ram air turbine power generation system according to claim 5, characterized in that, In step A3, the method for obtaining the load current is as follows: For high-frequency loads, for inertial systems like rotating shafts, based on the principle of PWM impulse equivalence, the high-frequency pulse load is calculated according to... By performing equivalent processing, the high-frequency load is treated as a stable load, and the feedforward current value is given. I s ; in, I m This indicates the peak current of the pulsed load. I l This represents the base current of the pulsed load. D Indicates the duty cycle.

8. A control method for a ram air turbine power generation system according to any one of claims 5 to 7, characterized in that, The following conditions must be met for current feedforward to be used: 1) The electrical load is a step load of T / R radar type; 2) The electrical load is a T / R radar type repetition frequency load.

Images