Control method of microgrid power generation system for electric propulsion aircraft based on fuzzy control strategy

Abstract

The present invention discloses a control method for an electric propulsion aircraft microgrid power generation system based on a fuzzy control strategy. This method belongs to the field of multi-electric aircraft microgrid power generation control. The method jointly models and simulates the control strategy of the power generation system's prime mover and the electric motor supplying energy to the microgrid. The power system is modeled with a small aircraft as the target. Based on the model, a power-following-based double-closed-loop excitation system feedback fuzzy control is designed. A grid-connection control strategy is established according to grid-connection rules. Finally, a power generation system and control system model is established, and simulation experiments are performed to verify the method. The method can effectively suppress the impact of propeller characteristic loads on the power generation system, implement fuzzy control of adjustable parameters, improve control accuracy and dynamic performance, and improve the power generation performance of the electric propulsion aircraft microgrid and the impact response to propeller characteristic loads.

Description

Technical Field

[0001] The present invention relates to the technical field of microgrid power generation control for multi-electric aircraft, and in particular to a control method for a microgrid power generation system of an electric propulsion aircraft based on a fuzzy control strategy. Background Art

[0002] During cruise, the electric motor drives the propeller. The main propulsion motor faces a sudden, heavy load and needs to respond quickly to deliver sufficient power while maintaining microgrid stability. However, due to the characteristics of propeller loads, wind speed fluctuations during flight inevitably cause propeller torque, leading to motor speed fluctuations and thus affecting flight stability. Therefore, improving disturbance rejection becomes another key control system issue. Traditional control methods struggle to address these uncertainties when implementing startup control. Summary of the Invention

[0003] The present invention provides a control method for an electric propulsion aircraft microgrid power generation system based on a fuzzy control strategy, which can improve the control performance of the aircraft microgrid when coping with heavy propeller loads and realize grid-connected control of microgrid units.

[0004] An embodiment of the present invention provides a method for controlling a microgrid power generation system of an electric propulsion aircraft based on a fuzzy control strategy, comprising the following steps:

[0005] Step 1: Construct the descriptive equations of the prime mover and motor speed loop of the power generation system and model each power system subcomponent of the microgrid;

[0006] Step 2: Construct a speed and power dual closed-loop power generation control system, and perform fuzzy control on the PID parameters of the exciter of the power generation control system;

[0007] Step 3: Use fuzzy PID control to correct the PID parameters, compensate and optimize the error feedback control law of the ADRC model, obtain the final error feedback control law, and realize fuzzy control of the power generation control system;

[0008] Step 4: Design the generator grid-connected control strategy based on the microgrid grid-connected requirements and the characteristics of the propeller characteristic load.

[0009] Optionally, in one embodiment of the present invention, the mathematical model of each subsystem of the power generation system is:

[0010] 1) Motor model

[0011] 1-1) Voltage equation

[0012]

[0013] 1-2) Magnetic flux equation

[0014]

[0015] 1-3) Electromagnetic torque equation

[0016]

[0017] 1-4) Mechanical motion equations

[0018]

[0019] Where u d 、u q 、u f are the stator direct axis voltage, stator quadrature axis voltage and rotor excitation voltage respectively, R s 、R f are the resistance values ​​of the armature winding and the field winding respectively, i d 、i q 、i f are the stator direct axis current, stator quadrature axis current and rotor excitation current respectively, p is the Park transformation coefficient, ψ d , ψ q , ψ f are the stator direct-axis flux, stator quadrature-axis flux and rotor excitation flux, L d , L q , L f are the armature reaction inductances of the stator direct axis, quadrature axis and rotor windings, M sf is the mutual inductance between the stator winding and the rotor excitation winding, ω e 、ω m are the rotor electrical angular velocity and machine angular velocity, n p is the number of motor pole pairs, D is the friction coefficient of the system, J is the moment of inertia of the motor, ω m is the mechanical angular velocity of the rotor, T em is the electromagnetic torque of the motor, T L is the load torque;

[0020] 2) Exciter model

[0021] 2-1) Magnetic flux equation

[0022]

[0023] Where ψ is the winding flux, i is the winding current, L is the inductance, and the letters in the subscripts represent: d, q, 0 represent the direct axis, quadrature axis and zero sequence winding respectively, r, s represent the rotor and stator respectively, L m is the mutual inductance between the stator and rotor windings; L1 is the stator winding leakage inductance;

[0024] 2-2) Voltage equation

[0025]

[0026] Where u is the voltage value, R r 、R s are the internal resistance of the rotor winding and the stator winding respectively, ω1 is the excitation electrical angular frequency, ω r is the electrical angular velocity;

[0027] 3) Inverter model

[0028] According to Kirchhoff's voltage law and node current law, the mathematical model of Vienna rectifier in three-phase stationary coordinate system is:

[0029]

[0030] Where, I is current, E is power; R is resistance; L is inductance, U is voltage; t is time, a, b, c are three-phase circuit codes, C1 and C2 are coefficients; I p and I n They are:

[0031]

[0032] S a 、S b 、S c They are:

[0033]

[0034] Assuming that the three-phase input power system is balanced, then assuming C1=C2=C, then U C1 =U C2 =0.5U dc , then the mathematical model of the rectifier in the two-phase rotating coordinate system is:

[0035]

[0036] Among them, i d 、i q is the grid-side current in the two-phase rotating coordinate system, U d 、U q is the grid side voltage, S d 、S q is the switching function S a 、S b 、S c Variables in the dq coordinate system, K d , K q is sign(E a )、sign(E b )、sign(Ec ) variables in the dq coordinate system.

[0037] Optionally, in one embodiment of the present invention, step 2 includes:

[0038] Step 2-1: Establish a dual closed-loop control strategy for power and speed

[0039] The transfer function is expressed as:

[0040]

[0041] The dual-loop control strategy of the three-stage brushless synchronous motor generator system is obtained:

[0042]

[0043] Where K G ,T g They are the gain and time constant of the AC exciter excitation current to the main motor output voltage, K ef ,T ef is the gain and time constant of the field winding;

[0044] Step 2-2: Simplify the dual-loop control strategy by ignoring the delay of the detection link and omitting the detection link to obtain a simplified dual-loop control strategy:

[0045]

[0046]

[0047] Where K f ,T f is the gain and time constant of terminal voltage detection, K μ ,T μ It is the gain and time constant of AC exciter excitation current detection.

[0048] Optionally, in one embodiment of the present invention, step 3 includes:

[0049] Step 3-1: Establish a fuzzy PI control strategy based on the dual-loop control strategy and the excitation current inner loop control strategy λ The controller implements the open-loop transfer function of the closed-loop control system for the power generation control voltage as follows:

[0050]

[0051] T g s+1 is equivalent to an integral link as a large inertia loop, so Equation (15) can be changed to:

[0052]

[0053] The generator gain increases with the increase of speed, as shown in formula (17):

[0054]

[0055] Where n is the motor speed, ∝ is proportional to;

[0056] In order to maintain the forward path open-loop gain of the system unchanged, the generator voltage P regulator is set to:

[0057]

[0058] Fuzzy PI λ The controller is designed in the voltage outer loop, so the fuzzy PI λ The controller is a two-input, three-output controller. The basic domain of the input is [-6, +6], the voltage error e and the derivative of the error rate of change error e. c , the basic domain of output is K p , K i and the range of λ, e, e c , K p , K i The corresponding linguistic variables of the fuzzy domain are negative big (NB), negative medium (NM), negative small (NS), zero (ZO), positive small (PS), positive medium (PM), and positive big (PB); the fuzzy linguistic variables of λ are set to small (S), smaller (LS), larger (LB), and larger (B);

[0059] Step 3-2: Establish a fuzzy rule base

[0060] Select the Z-shaped membership function on both sides and the triangle membership function in the middle. The larger the slope of the triangle is, the faster the adjustment action will be. The smaller the interval of zero (ZO) can be set to improve the voltage regulation accuracy of the system. The fuzzy rules designed are mainly set according to the following experience: K p The basic domain is [10,28], K i The basic domain of is [100,350], and the basic domain of λ is [0.5,1.0];

[0061] Step 3-3: Defuzzify the transfer function. The defuzzification part is responsible for converting the fuzzy quantity obtained after fuzzy inference into an accurate quantity. The centroid method is used for defuzzification, as shown in formula (19):

[0062]

[0063] Where v0 is the exact value of the fuzzy controller output after defuzzification, v k is the value in the domain of fuzzy control quantity, μ r (vi ) is v k The membership value of .

[0064] Optionally, in one embodiment of the present invention, step 4 includes:

[0065] Step 4-1: Establish grid connection detection judgment logic according to grid connection rules

[0066] The function of voltage amplitude pre-synchronization controller is to collect VSG output voltage amplitude U VSG and the grid voltage amplitude U g The deviation of the voltage amplitude is used to determine whether the voltage amplitude deviation meets the grid connection requirements. The amplitude deviation setting value is ±1V. If the deviation is within this range, that is, |U VSG -U g |≤1, it is considered to meet the voltage amplitude requirements for grid pre-synchronization. If the phase deviation is greater than the set value, that is, |U VSG -U g |>1, the voltage amplitude deviation is fed into the PI controller to form a closed-loop control, and the output of the PI controller is compensated to the VSG output voltage amplitude until the amplitude deviation meets the grid connection requirements of the voltage amplitude, thus achieving voltage amplitude pre-synchronization;

[0067] Step 4-2: The grid-connected pre-synchronization control equation is:

[0068]

[0069] Where f is the frequency, is the phase angle, U is the voltage, the subscript N is the power parameter of the unit to be connected, the subscript g is the power parameter of the grid, and k is the controller parameter. By continuously compensating, detecting and judging the various deviation data, the required deviation amount is controlled in real time;

[0070] Step 4-3: Establish a grid-connected detection and control logic model based on simulation software to obtain the generator grid-connected control strategy.

[0071] Optionally, in one embodiment of the present invention, the grid connection process includes:

[0072] When the host computer issues a grid connection instruction,

[0073] (1) Switch on the phase-locked loop and use it to measure the frequency, amplitude and phase angle of the VSG and grid voltage respectively;

[0074] (2) The frequency reference value ω of the virtual synchronous generator controller is ref From ω n Switch to ω g, and at the same time set the integral parameter K1 of the frequency channel to 30, then a fractional-order PI controller is formed, which makes the frequency approach consistency and meets the grid connection conditions;

[0075] (3) V ref From V n Switch to V g At the same time, the integral parameter K2 of the voltage rate channel is set to 30 to form a fractional-order PI controller, thereby meeting the grid connection conditions and making the voltage amplitude generated by the unit to be connected consistent with the bus;

[0076] (4) The integral parameter and proportional parameter of the PI controller of the phase angle channel are set to 50 and 2 respectively, and the phase angle difference of the two voltages is sent to the PI controller to meet the grid connection conditions so that the current phase of the unit to be connected is consistent with that of the bus;

[0077] (5) After the inverter is adjusted by the VSG pre-synchronization control, the difference between the frequency, amplitude and phase of the output of the unit to be connected and the bus will continue to decrease and approach 0. When the grid connection conditions are met, the unit to be connected will be connected to the grid, and the pre-synchronization control work based on the improved virtual synchronous generator control strategy is completed;

[0078] When the host computer detects that the unit to be connected is successfully connected to the microgrid bus, the grid-connected inverter begins to exit the grid-connected control and enter the autonomous operation state of the VSG. The specific operations are as follows:

[0079] (1) Change the frequency reference from ω g Switch to ω n , set the voltage amplitude reference value V ref from Switch to The purpose of this step is to set the reference frequency and reference voltage of the VSG to the rated values, so that it enters the autonomous primary frequency and voltage regulation control mode;

[0080] (2) Set the integral and proportional parameters of the fractional-order PI controllers of the frequency channel and phase angle improvement channel to 0, making them an inertia link;

[0081] (3) The host computer issues a command to cut out the phase-locked loop, and the inverter enters the VSG autonomous operation state from the VSG pre-synchronization control and enters the conventional VSG control mode. At this point, the pre-synchronization control is completed.

[0082] The control method of the electric propulsion aircraft microgrid power generation system based on the fuzzy control strategy of the embodiment of the present invention has the following features:

[0083] Beneficial effects:

[0084] 1) Achieved stable control of the power generation system when dealing with special propeller loads;

[0085] 2) The system has excellent anti-disturbance capabilities when facing sudden loads of propeller type;

[0086] 3) When the power generation system encounters the disturbance torque of the propeller system, it effectively suppresses the impact of the estimation error caused by the untimely estimation on the entire system, ensuring the control quality;

[0087] 4) By utilizing the fuzzy PID control principle, variable parameter control of the power generation system with a larger control domain is achieved, contributing to the rapid and accurate response of the system;

[0088] 5) The microgrid grid-connected control of the power generation system was realized, and a microgrid unit grid-connected control method was proposed.

[0089] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0091] Figure 1 A diagram of a microgrid power generation control system in an embodiment of the present invention;

[0092] Figure 2 This is a flow chart of a control method for an electric propulsion aircraft microgrid power generation system based on a fuzzy control strategy according to the present invention;

[0093] Figure 3 This is the block diagram of the dual-loop control of the power generation system combined with fuzzy PID;

[0094] Figure 4 This is a simplified dual-loop feedback block diagram of a power generation system according to an embodiment of the present invention;

[0095] Figure 5 This is a block diagram of the inner loop control of the excitation current in an embodiment of the present invention;

[0096] Figure 6 This is a block diagram of the pre-synchronization control strategy in an embodiment of the present invention;

[0097] Figure 7 This is the grid connection detection and control logic model in the embodiment of the present invention;

[0098] Figure 8 This is a diagram showing the frequency phase and voltage difference effects after the grid connection strategy is implemented in an embodiment of the present invention;

[0099] Figure 9 This is a voltage and current diagram after the grid connection strategy is implemented in an embodiment of the present invention;

[0100] Figure 10 This is a voltage curve after a sudden increase in load in an embodiment of the present invention;

[0101] Figure 11 This is a current curve after a sudden increase in load in an embodiment of the present invention. DETAILED DESCRIPTION

[0102] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0103] like Figure 1 As shown, the embodiment of the present invention is based on the electric propulsion aircraft microgrid power generation control system. In order to deal with the impact of the special propeller load on the microgrid, a set of control logic for grid-connected power generation is proposed. The fractional order adjustable parameter K is calculated by fuzzy rules. p ,K d ,μ performs self-tuning, and realizes grid-connected power generation of multiple units through grid-connected detection and control.

[0104] Figure 2 The flowchart of the control method of the electric propulsion aircraft microgrid power generation system based on fuzzy control strategy of the present invention.

[0105] like Figure 2 As shown, the control method of the electric propulsion aircraft microgrid power generation system based on the fuzzy control strategy includes the following steps:

[0106] Step 1: Construct the descriptive equations of the prime mover and motor speed loop of the power generation system and model each power system subcomponent of the microgrid.

[0107] The fractional-order active disturbance rejection control of the present invention is described.

[0108] The mathematical models of each subsystem of the power generation system are:

[0109] 1) Motor model

[0110] 1-1) Voltage equation

[0111]

[0112] 1-2) Magnetic flux equation

[0113]

[0114] 1-3) Electromagnetic torque equation

[0115]

[0116] 1-4) Mechanical motion equations

[0117]

[0118] Where u d 、u q 、u f are the stator direct axis voltage, stator quadrature axis voltage and rotor excitation voltage respectively, R s 、R f are the resistance values ​​of the armature winding and the field winding respectively, i d 、i q 、i f are the stator direct axis current, stator quadrature axis current and rotor excitation current respectively, p is the Park transformation coefficient, ψ d , ψ q , ψ f are the stator direct-axis flux, stator quadrature-axis flux and rotor excitation flux, L d , L q , L f are the armature reaction inductances of the stator direct axis, quadrature axis and rotor windings, M sf is the mutual inductance between the stator winding and the rotor excitation winding, ω e 、ω m are the rotor electrical angular velocity and machine angular velocity, n p is the number of motor pole pairs, D is the friction coefficient of the system, J is the moment of inertia of the motor, ω m is the mechanical angular velocity of the rotor, T em is the electromagnetic torque of the motor, T L is the load torque.

[0119] 2) Exciter model

[0120] 2-1) Magnetic flux equation

[0121]

[0122] Where ψ is the winding flux, i is the winding current, L is the inductance, and the letters in the subscripts represent: d, q, 0 represent the direct axis, quadrature axis and zero sequence winding respectively, r, s represent the rotor and stator respectively, L m is the mutual inductance between the stator and rotor windings; L1 is the stator winding leakage inductance;

[0123] 2-2) Voltage equation

[0124]

[0125] Where u is the voltage value, R r 、R sare the internal resistance of the rotor winding and the stator winding respectively, ω1 is the excitation electrical angular frequency, ω r is the electrical angular velocity;

[0126] 3) Inverter model

[0127] According to Kirchhoff's voltage law and node current law, the mathematical model of the rectifier in the three-phase stationary coordinate system is:

[0128]

[0129] Where, I is current, E is power; R is resistance; L is inductance, U is voltage; t is time, a, b, c are three-phase circuit codes, C1 and C2 are coefficients; I p and I n I p and I n They are:

[0130]

[0131] S a 、S b 、S c They are:

[0132]

[0133] Assuming that the three-phase input power system is balanced, then assuming C1=C2=C, then U C1 =U C2 =0.5U dc , then the mathematical model of the rectifier in the two-phase rotating coordinate system is:

[0134]

[0135] Among them, i d 、i q is the grid-side current in the two-phase rotating coordinate system, U d 、U q is the grid side voltage, S d 、S q is the switching function Sx, S b 、S c Variables in the dq coordinate system, K d , K q is signEa(E a )、sign(E b )、sign(E c ) variables in the dq coordinate system.

[0136] Step 2: Construct a speed and power dual closed-loop power generation control system, and perform fuzzy control on the PID parameters of the exciter of the power generation control system.

[0137] In an embodiment of the present invention, step 2 includes:

[0138] Step 2-1: Establish a dual closed-loop control strategy for power and speed

[0139] The transfer function is expressed as:

[0140]

[0141] like Figure 3 As shown, the dual-loop control strategy of the three-level brushless synchronous motor generator system is obtained:

[0142]

[0143] Where K G ,T g They are the gain and time constant of the AC exciter excitation current to the main motor output voltage, K ef ,T ef is the gain and time constant of the field winding.

[0144] Step 2-2: Simplify the dual-loop control strategy to ignore the delay of the detection link, omit the detection link, and obtain the simplified dual-loop control strategy, such as Figure 4 and Figure 5 As shown:

[0145]

[0146]

[0147] Where K f ,T f is the gain and time constant of terminal voltage detection, K μ ,T μ It is the gain and time constant of AC exciter excitation current detection.

[0148] Step 3: Use fuzzy PID control to correct the PID parameters, compensate and optimize the error feedback control law of the ADRC model, obtain the final error feedback control law, and realize fuzzy control of the power generation control system.

[0149] In an embodiment of the present invention, step 3 includes:

[0150] Step 3-1: Establish fuzzy PI based on dual-loop control strategy and excitation current inner loop control strategy λ The controller implements the open-loop transfer function of the closed-loop control system for the power generation control voltage as follows:

[0151]

[0152] T g s+1 is equivalent to an integral link as a large inertia loop, so Equation (15) can be changed to:

[0153]

[0154] The generator gain increases with the increase of speed, as shown in formula (17):

[0155]

[0156] Where n is the motor speed, ∝ is proportional to;

[0157] In order to maintain the forward path open-loop gain of the system unchanged, the generator voltage P regulator is set to:

[0158]

[0159] Fuzzy PI λ The controller is designed in the voltage outer loop, so the fuzzy PI λ The controller can be a two-input, three-output controller. The basic domain of the input quantity can be selected from [-6, +6] voltage error e and the derivative e of the error rate of change error e. c , the basic domain of output is K p , K i and the range of λ. e、e c , K p , K i The corresponding linguistic variables of the fuzzy domain are negative big (NB), negative medium (NM), negative small (NS), zero (ZO), positive small (PS), positive medium (PM), and positive big (PB). The fuzzy linguistic variables of λ are set to small (S), smaller (LS), larger (LB), and larger (B);

[0160] Step 3-2: Establish a fuzzy rule base

[0161] The accuracy and speed of the fuzzy controller are closely related to the shape of the membership function. Z-shaped membership functions are selected on both sides and triangular membership functions are selected in the middle. The larger the slope of the triangle, the faster the adjustment action will be. The smaller the interval of zero (ZO) can be set to improve the voltage regulation accuracy of the system. The designed fuzzy rules are mainly set according to the following experience: K p The basic domain is [10,28], K i The basic domain of is [100,350], and the basic domain of λ is [0.5,1.0];

[0162] Table 1 K pFuzzy rules

[0163]

[0164] Table 2K i Fuzzy rules

[0165]

[0166] Table 3 λ fuzzy rules

[0167]

[0168] This controller uses fuzzy neural network to calculate the system deviation e and the rate of change of the deviation e. c Real-time monitoring is carried out, and the PID parameters are optimized through the mapping relationship between its output and input, ultimately achieving the most controllable solution to the impact of instantaneous large load loading of electric propulsion aircraft on the power system, so that the voltage can obtain timely feedback when the load is suddenly increased, maintaining the stability of the power system.

[0169] Fuzzy fractional-order PI λ The control has the advantages of both fuzzy control and fractional order control, and can improve the steady-state and dynamic performance of aircraft variable frequency AC power generation system.

[0170] For power generation systems, if they want to operate in parallel with a large power grid, they need to meet the requirements of quasi-synchronous parallel operation, that is, the voltage amplitude, phase, and frequency deviation on both sides of the grid connection point must comply with the standard regulations. Consulting relevant national standards shows that the difference in the above parameters must meet the requirements shown in Table 1 (in order to reduce the impact current, the allowable range can be appropriately narrowed during actual operation to make the grid connection environment more superior).

[0171] Step 3-3: Defuzzify the transfer function. The defuzzification part is responsible for converting the fuzzy quantity obtained after fuzzy inference into an accurate quantity. The centroid method is used for defuzzification, as shown in formula (19):

[0172]

[0173] Where v0 is the exact value of the fuzzy controller output after defuzzification, v k is the value in the domain of fuzzy control quantity, μ r (v i ) is v k The membership value of .

[0174] Step 4: Design the generator grid-connected control strategy based on the microgrid grid-connected requirements and the characteristics of the propeller characteristic load.

[0175] In an embodiment of the present invention, step 4 includes:

[0176] Step 4-1: Establish grid connection detection judgment logic according to grid connection rules, such as Figure 6 shown.

[0177] The function of voltage amplitude pre-synchronization controller is to collect VSG output voltage amplitude U VSG and the grid voltage amplitude U g The deviation of the voltage amplitude is used to determine whether the voltage amplitude deviation meets the grid connection requirements. The amplitude deviation setting value is ±1V. If the deviation is within this range, that is, |U VSG -U g |≤1, it is considered to meet the voltage amplitude requirements for grid pre-synchronization. If the phase deviation is greater than the set value, that is, |U VSG -U g |>1, the voltage amplitude deviation is fed into the PI controller to form a closed-loop control, and the output of the PI controller is compensated to the VSG output voltage amplitude until the amplitude deviation meets the grid connection requirements of the voltage amplitude, thus achieving voltage amplitude pre-synchronization;

[0178] Step 4-2: According to Figure 6 The control equations for the grid-connected pre-synchronization control block diagram are written as follows:

[0179]

[0180] Where f is the frequency, is the phase angle, U is the voltage, the subscript N is the power parameter of the unit to be connected, the subscript g is the power parameter of the grid, and k is the controller parameter. By continuously compensating, detecting, and judging the various deviation data, the required deviation amount is controlled in real time. The data tracking speed of this method is determined by the detection speed of the voltage parameters on both sides of the grid connection point. The faster the detection speed of the voltage amplitude, phase, and frequency on both sides of the grid connection point, the shorter the calculation time of the parameter deviation, the shorter the pre-synchronization time, and the faster the grid connection speed.

[0181] Step 4-3: Establish a grid-connected detection and control logic model based on simulation software to obtain the generator grid-connected control strategy.

[0182] The grid connection process includes:

[0183] When the host computer issues a grid connection instruction,

[0184] (1) Switch on the phase-locked loop and use it to measure the frequency, amplitude and phase angle of the VSG and grid voltage respectively;

[0185] (2) The frequency reference value ω of the virtual synchronous generator controller is ref From ω n Switch to ω g, and at the same time set the integral parameter K1 of the frequency channel to 30, then a fractional-order PI controller is formed, which makes the frequency approach consistency and meets the grid connection conditions;

[0186] (3) V ref From V n Switch to V g At the same time, the integral parameter K2 of the voltage rate channel is set to 30 to form a fractional-order PI controller, thereby meeting the grid connection conditions and making the voltage amplitude generated by the unit to be connected consistent with the bus;

[0187] (4) The integral parameter and proportional parameter of the PI controller of the phase angle channel are set to 50 and 2 respectively, and the phase angle difference of the two voltages is fed into the PI controller to meet the grid connection conditions so that the current phase of the unit to be connected is consistent with that of the bus;

[0188] (5) After the inverter is adjusted by the VSG pre-synchronization control, the difference between the frequency, amplitude and phase of the output of the unit to be connected and the bus will continue to decrease and approach 0. When the grid connection conditions are met, the unit to be connected will be connected to the grid, and the pre-synchronization control work based on the improved virtual synchronous generator control strategy is completed;

[0189] When the host computer detects that the unit to be connected is successfully connected to the microgrid bus, the grid-connected inverter begins to exit the grid-connected control and enter the autonomous operation state of the VSG. The specific operations are as follows:

[0190] (1) Change the frequency reference from ω g Switch to ω n , set the voltage amplitude reference value V ref from Switch to The purpose of this step is to set the reference frequency and reference voltage of the VSG to the rated values, so that it enters the autonomous primary frequency and voltage regulation control mode;

[0191] (2) Set the integral and proportional parameters of the fractional-order PI controllers of the frequency channel and phase angle improvement channel to 0, making them an inertia link;

[0192] (3) The host computer issues a command to cut out the phase-locked loop, and the inverter enters the VSG autonomous operation state from the VSG pre-synchronization control and enters the conventional VSG control mode. At this point, the pre-synchronization control is completed.

[0193] Build a grid-connected detection and control logic model based on MATLAB / Simulink, such as Figure 7 As shown in the figure, the grid-connected effect is as follows Figures 8-11 shown.

[0194] In order to verify the correctness and effectiveness of the above-designed starting control method based on improved fractional-order anti-disturbance control, the present invention simulates the process of sudden addition and removal of static load during the startup and operation of a single generator based on MATLAB / Simulink, so as to further verify the application effect of the power system simulation model of a generator set running on the grid. The main experimental process is: the simulation program starts to generate electricity at no-load operation, and after reaching steady state, a static load of 10MW is put into operation. After the operation is stable, the load is gradually increased, and the remaining load is divided into two times, and 10MW of static load is added each time to put into operation until the full load operation is stable. Set the initial parameter to K p =27,K i =150 and λ=0.98.

[0195] like Figure 10-11 As shown, at 0s, the generator was connected to the circuit, and the speed dropped momentarily to 3600 rpm. Then, the engine increased its fuel command, raising its output power and causing the generator speed to rise. The voltage remained around 10.5 kV under the action of the excitation, and the current gradually increased with the power increase. At 80s, the first 10MW static load was applied. This sudden increase in load caused the generator speed to decrease, prompting the speed control system to activate. The engine fuel command increased, and the output power subsequently increased, gradually returning the speed to the rated speed. The excitation voltage also surged at the instant of the load increase, enhancing the system's voltage regulation capability. Thanks to the excitation and voltage regulation system, the grid voltage did not experience significant fluctuations, and the current approximately doubled. Around 200s, the system stabilized. At 400s, the 10MW static load was applied again, and system parameters experienced similar changes as during the first load increase. Around 700s, the system stabilized again. Throughout this process, the grid voltage remained at the rated voltage, with minimal fluctuations, meeting power system stability requirements.

[0196] According to the electric propulsion aircraft microgrid power generation system control method based on fuzzy control strategy proposed in an embodiment of the present invention, the control strategy of the power generation system prime mover and the electric motor supplying energy to the microgrid are jointly modeled and simulated. First, based on the literature, the power system is modeled with a small aircraft as the target for power generation and power system modeling, and based on the model, a double closed-loop excitation system feedback fuzzy control based on power following is designed. The grid connection control strategy is established according to the grid connection rules. Finally, the power generation system and control system models are established in Simulink and verified by simulation experiments. Compared with the existing technology, it can effectively suppress the influence of the propeller characteristic load on the power generation system, realize the fuzzy control of adjustable parameters, improve the control accuracy and dynamic performance, improve the power generation performance of the electric propulsion aircraft microgrid, and improve the impact response to the propeller characteristic load.

[0197] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0198] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "N" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0199] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or N executable instructions for implementing a custom logical function or step of a process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention pertain.

Claims

1. A control method for an electric propulsion aircraft microgrid power generation system based on a fuzzy control strategy, characterized in that: The following steps are involved: Step 1: Construct the descriptive equations of the prime mover and motor speed loop of the power generation system and model each power system subcomponent of the microgrid; Step 2: Construct a speed and power dual closed-loop power generation control system, and perform fuzzy control on the PID parameters of the exciter of the power generation control system; Step 2-1: Establish a power and speed dual closed-loop control strategy; Step 2-2: Simplify the dual-loop control strategy by ignoring the delay of the detection link and omitting the detection link to obtain a simplified dual-loop control strategy; Step 3: Use fuzzy PID control to correct PID parameters, compensate and optimize the error feedback control law of the ADRC model, obtain the final error feedback control law, and implement fuzzy control of the power generation control system. Step 3 includes: Step 3-1: Establish fuzzy PI control strategy based on the dual-loop control strategy and the excitation current inner loop control strategy λ The controller implements the open-loop transfer function of the closed-loop control system for the power generation control voltage as follows: T g s+1 is equivalent to an integral link as a large inertia loop, so Equation (15) can be changed to: The generator gain increases with the increase of speed, as shown in formula (17): K G ∝n (17) Where n is the motor speed, ∝ is proportional to; In order to maintain the forward path open-loop gain of the system unchanged, the generator voltage P regulator is set to: Fuzzy PI λ The controller is designed in the voltage outer loop, so the fuzzy PI λ The controller is a two-input, three-output controller. The basic domain of the input is [-6, +6], the voltage error e and the derivative of the error rate of change error e. c , the basic domain of output is K p , K i and the range of λ, e, e c , K p , K i The corresponding linguistic variables of the fuzzy domain are negative big (NB), negative medium (NM), negative small (NS), zero (ZO), positive small (PS), positive medium (PM), and positive big (PB); the fuzzy linguistic variables of λ are set to small (S), smaller (LS), larger (LB), and larger (B); Step 3-2: Establish a fuzzy rule base Select the Z-shaped membership function on both sides and the triangle membership function in the middle. The larger the slope of the triangle is, the faster the adjustment action will be. The smaller the interval of zero (ZO) can be set to improve the voltage regulation accuracy of the system. The fuzzy rules designed are mainly set according to the following experience: K p The basic domain is [10,28], K i The basic domain of is [100,350], and the basic domain of λ is [0.5,1.0]; Step 3-3: Defuzzify the transfer function. The defuzzification part is responsible for converting the fuzzy quantity obtained after fuzzy inference into an accurate quantity. The centroid method is used for defuzzification, as shown in formula (19): Where v0 is the exact value of the fuzzy controller output after defuzzification, v k is the value in the domain of fuzzy control quantity, μ r (v i ) is v k The membership value of Step 4: Design the generator grid-connected control strategy based on the microgrid grid-connected requirements and the characteristics of the propeller characteristic load.

2. The method according to claim 1, characterized in that In step 1, the mathematical models of the subsystems of the power generation system are: 1) Motor model 1-1) Voltage equation 1-2) Magnetic flux equation 1-3) Electromagnetic torque equation 1-4) Mechanical motion equations Where u d 、u q 、u f are the stator direct axis voltage, stator quadrature axis voltage and rotor excitation voltage respectively, R s 、R f are the resistance values ​​of the armature winding and the field winding respectively, i d 、i q 、i f are the stator direct axis current, stator quadrature axis current and rotor excitation current respectively, p is the Park transformation coefficient, ψ d , ψ q , ψ f are the stator direct-axis flux, stator quadrature-axis flux and rotor excitation flux, L d , L q , L f are the armature reaction inductances of the stator direct axis, quadrature axis and rotor windings, M sf is the mutual inductance between the stator winding and the rotor excitation winding, ω e 、ω m are the rotor electrical angular velocity and machine angular velocity, n p is the number of motor pole pairs, D is the friction coefficient of the system, J is the moment of inertia of the motor, ω m is the mechanical angular velocity of the rotor, T em is the electromagnetic torque of the motor, T L is the load torque; 2) Exciter model 2-1) Magnetic flux equation Where ψ is the winding flux, i is the winding current, L is the inductance, and the letters in the subscripts represent: d, q, 0 represent the direct axis, quadrature axis and zero sequence winding respectively, r, s represent the rotor and stator respectively, L m is the mutual inductance between the stator and rotor windings; L1 is the stator winding leakage inductance; 2-2) Voltage equation Where u is the voltage value, R r 、R s are the internal resistance of the rotor winding and the stator winding respectively, ω1 is the excitation electrical angular frequency, ω r is the electrical angular velocity; 3) Inverter model According to Kirchhoff's voltage law and node current law, the mathematical model of Vienna rectifier in three-phase stationary coordinate system is: Where, I is current, E is power; R is resistance; L is inductance, U is voltage; t is time, a, b, c are three-phase circuit codes, C1 and C2 are coefficients; I p and I n They are: S a 、S b 、S c They are switch signals respectively, and the logic is: Assuming that the three-phase input power system is balanced, then assuming C1=C2=C, then U C1 =U C2 =0.5U dc , then the mathematical model of the rectifier in the two-phase rotating coordinate system is: Among them, i d 、i q is the grid-side current in the two-phase rotating coordinate system, U d 、U q is the grid side voltage, S d 、S q is the switching function S a 、S b 、S c Variables in the dq coordinate system, K d , K q is sign(E a )、sign(E b )、sign(E c ) variables in the dq coordinate system.

3. The method according to claim 2, characterized in that The step 2 includes: The transfer function is expressed as: The dual-loop control strategy of the three-stage brushless synchronous motor generator system is obtained: Where K G ,T g They are the gain and time constant of the AC exciter excitation current to the main motor output voltage, K ef ,T ef is the gain and time constant of the field winding; The transfer functions of the current loop and voltage loop are: Where K f ,T f is the gain and time constant of terminal voltage detection, K μ ,T μ It is the gain and time constant of AC exciter excitation current detection.

4. The method according to claim 1, wherein The step 4 comprises: Step 4-1: Establish grid connection detection judgment logic according to grid connection rules The function of voltage amplitude pre-synchronization controller is to collect VSG output voltage amplitude U VSG and the grid voltage amplitude U g The deviation of the voltage amplitude is used to determine whether the voltage amplitude deviation meets the grid connection requirements. The amplitude deviation setting value is ±1V. If the deviation is within this range, that is, |U VSG -U g |≤1, it is considered to meet the voltage amplitude requirements for grid pre-synchronization. If the phase deviation is greater than the set value, that is, |U VSG -U g |>1, the voltage amplitude deviation is fed into the PI controller to form a closed-loop control, and the output of the PI controller is compensated to the VSG output voltage amplitude until the amplitude deviation meets the grid connection requirements of the voltage amplitude, thus achieving voltage amplitude pre-synchronization; Step 4-2: The grid-connected pre-synchronization control equation is: Where f is the frequency, is the phase angle, U is the voltage, the subscript N is the power parameter of the unit to be connected, the subscript g is the power parameter of the grid, and k is the controller parameter. By continuously compensating, detecting and judging the various deviation data, the required deviation amount is controlled in real time; Step 4-3: Establish a grid-connected detection and control logic model based on simulation software to obtain the generator grid-connected control strategy.

5. The method according to claim 4, characterized in that The grid connection process includes: When the host computer issues a grid connection instruction, (1) Switch on the phase-locked loop and use it to measure the frequency, amplitude and phase angle of the VSG and grid voltage respectively; (2) The frequency reference value ω of the virtual synchronous generator controller is ref From ω n Switch to ω g , and at the same time set the integral parameter K1 of the frequency channel to 30, then a fractional-order PI controller is formed, which makes the frequency approach consistency and meets the grid connection conditions; (3) V ref From V n Switch to V g At the same time, the integral parameter K2 of the voltage rate channel is set to 30 to form a fractional-order PI controller, thereby meeting the grid connection conditions and making the voltage amplitude generated by the unit to be connected consistent with the bus; (4) The integral parameter and proportional parameter of the PI controller of the phase angle channel are set to 50 and 2 respectively, and the phase angle difference of the two voltages is fed into the PI controller to meet the grid connection conditions so that the current phase of the unit to be connected is consistent with that of the bus; (5) After the inverter is adjusted by the VSG pre-synchronization control, the difference between the frequency, amplitude and phase of the output of the unit to be connected and the bus will continue to decrease and approach 0. When the grid connection conditions are met, the unit to be connected will be connected to the grid, and the pre-synchronization control work based on the improved virtual synchronous generator control strategy is completed; When the host computer detects that the unit to be connected is successfully connected to the microgrid bus, the grid-connected inverter begins to exit the grid-connected control and enter the autonomous operation state of the VSG. The specific operations are as follows: (1) Change the frequency reference from ω g Switch to ω n , set the voltage amplitude reference value V ref from Switch to The purpose of this step is to set the reference frequency and reference voltage of the VSG to the rated values, so that it enters the autonomous primary frequency and voltage regulation control mode; (2) Set the integral and proportional parameters of the fractional-order PI controllers of the frequency channel and phase angle improvement channel to 0, making them an inertia link; (3) The host computer issues a command to cut out the phase-locked loop, and the inverter enters the VSG autonomous operation state from the VSG pre-synchronization control and enters the conventional VSG control mode. At this point, the pre-synchronization control is completed.

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