The present invention belongs to the technical field of aviation electrics and electric power, and particularly relates to an aircraft grid phase angle tracker.
With the continuous improvement of aircraft electrical level, the more electric aircraft has emerged. The more electric aircraft can reduce the consumption rate of aviation kerosene, increase the working efficiency of aero-engine, and reduce the emissions of nitrogen oxide. The grid is an important part of the more electric aircraft. On the one hand, the aircraft grid provides power for the flight control system and the environmental control system, and furthermore, the aircraft grid provides power for the aircraft starter/generator machine. Its performance directly affects the working state of the aircraft system, and even affects the safety and reliability of the aircraft. The tracking of the grid phase angle is one of the important tasks of the aircraft grid system. Once the tracking of the grid phase angle is inaccurate, the working safety of the aircraft grid is affected, and the quality of the grid is decreased, which will damage the aircraft electrical device at a light level and affect the flight safety of the aircraft at a serious level. Therefore, it is very valuable to accurately track the angle of the aircraft grid, especially in the case of harmonic interference in the grid, which can improve the stability margin of the aircraft grid.
In the aspect of the aircraft grid phase angle tracker, the published literature in China and abroad records that the grid phase angle tracker is designed based on the proportional integral method or proportional integral differential method. Especially in the case of fast varying sinusoidal harmonic disturbances in the grid, the existing methods cannot well attenuate the harmonic disturbances to the angle of the aircraft grid. At the same time, most of the current grid phase angle trackers are based on single grid working frequency. The frequency of the grid of the more electric aircraft varies within the range of 360-800 Hz. The change of the grid frequency also affects the tracking accuracy of the grid phase angle tracker. The existing methods cannot satisfy the requirements of high-accuracy tracking of the aircraft grid phase angle.
For the aircraft grid phase angle tracker, the current design method has gradually failed to satisfy the actual needs of engineering. Therefore, it is an urgent problem to be solved to explore a design method of a high-accuracy grid phase angle tracker which is effective and suitable for engineering practice. Therefore, the high-accuracy tracking of the aircraft grid phase angle has broad research and application prospects.
To solve the problems of complicated operation, low efficiency and low accuracy of tracking of grid phase angle in the prior art, the present invention proposes a high-accuracy tracking method for a nonlinear grid phase angle.
An aircraft grid phase angle tracker based on nonlinear active disturbance rejection comprises the following steps:
Concrete explanation is as follows:
The present invention has the following beneficial effects:
The existing aircraft grid phase angle tracker is difficult to achieve high-precision tracking of the grid phase angle. In engineering practice, at present, the grid phase angle tracker is generally designed by the methods based on proportional integral method, proportional integral differential method or linear active disturbance rejection method. The existing literature indicates that the tracking accuracy of the grid phase angle tracker based on linear active disturbance rejection is higher than that of the grid phase angle tracker based on proportional integral and proportional integral differential. The present invention provides a high-accuracy nonlinear grid phase angle tracking method based on model information, and makes up for the deficiencies of the existing grid phase tracker technology based on linear active disturbance rejection. The present invention applies the nonlinear active disturbance rejection technology to the phase angle tracking of the more electric aircraft grid, is simple in operation and high in accuracy, and can realize high-accuracy tracking of the grid phase angle. The method has certain extensibility and can be extended to other fields.
To make the purpose, technologies and the advantages of the present invention more clear, the present invention will be further described below in detail in combination with the drawings and the embodiments.
An aircraft grid phase angle tracker based on nonlinear active disturbance rejection framework, also known as a grid synchronization (phase-locked loop) module, i.e., the grid synchronization (phase-locked loop) module in
wherein Vm is the amplitude of the three-phase AC; Va, Vb and Vc indicate three-phase AC respectively; ω is the frequency of the three-phase AC; and θ=ωt is the grid phase angle. The core job of the patent is to design an aircraft grid phase angle tracker based on nonlinear active disturbance rejection to estimate the grid phase angle under complex conditions of amplitude change and frequency change of the three-phase AC, voltage amplitude imbalance in the grid, high harmonics in the grid and DC bias, comprising the following steps:
Step 1: to facilitate analysis, firstly, defining a coordinate system for the purpose of converting AC Vabc in a three-phase stationary rotating coordinate system to a two-phase stationary coordinate system ναβ, and finally to a two-phase rotating coordinate system νqd; the ultimate purpose of converting to the two-phase rotating coordinate system is to control νd=0 to lay a foundation for estimating the grid phase angle indirectly, and conversion relationships between the coordinate systems are described with formula (1):
wherein
{circumflex over (θ)} is an estimated value of the grid phase angle.
Step 2: using the embedded generator as an AC voltage source, and obtaining a model of a nominal AC voltage source of a more electric aircraft according to general nominal grid parameters of the more electric aircraft, with a mathematical expression satisfying formula (2):
wherein Va, Vb, and Vc are voltage of three-phase AC of the aircraft respectively; θ=ωt is the grid phase angle; ω is three-phase AC frequency; and Vm is a three-phase voltage amplitude. AC Vabc under the three-phase stationary rotating coordinate system in the formula (2) is converted to the two-phase rotating coordinate system νqd, and νd=0 is controlled to ensure that the estimated value of the grid phase angle ultimately converges to a true value of the grid phase angle.
Step 3: in the case of voltage amplitude imbalance in the grid, high harmonics in the grid and DC bias, the AC in the grid of the more electric aircraft does not satisfy the situation shown in formula (2). The cases of voltage amplitude imbalance in the grid, high harmonics in the grid and DC bias respectively correspond to mathematical expressions which satisfy formula (3), formula (4) and formula (5);
wherein β and γ are respectively the voltage amplitude imbalance coefficients of the aircraft three-phase grid. v5 is the amplitude of 5th voltage harmonic components of the aircraft three-phase grid, and v2n−1 is the amplitude of 2n−1th voltage harmonic components of the aircraft three-phase grid; Vao, Vbo and Vco are the voltage DC biases of the aircraft three-phase grid respectively.
Second step, design of the grid phase angle tracker;
wherein {circumflex over (θ)} is the estimated value of the aircraft grid phase angle; Epu is an amplitude gain coefficient caused by the voltage imbalance; and ϕpu is an initial phase angle caused by the voltage imbalance.
Step 5: considering the situation of high harmonics in the grid, when νd=0, obtaining a static error between the estimated value of the grid phase angle and the true value of the grid phase angle through mathematical derivation, as shown in formula (7);
wherein v5 is the amplitude of 5th voltage harmonics, v7 is the amplitude of 7th voltage harmonics, v11 is the amplitude of 11th voltage harmonics, v13 is the amplitude of 13th voltage harmonics, is the amplitude of 6n−1th voltage harmonics, V6n+1 is the amplitude of 6n+1th voltage harmonics, E6h is the voltage amplitude synthesized by the amplitudes of 5th and 7th harmonic components, E12h is the voltage amplitude synthesized by the amplitudes of 11th and 13th harmonic components, E6h, is the voltage amplitude synthesized by the amplitudes of 6n−1th and 6n+1th harmonic components, and n is a positive integer;
wherein Vao, Vbo and Vco are the voltage DC biases of the aircraft three-phase grid respectively, Edo is an amplitude gain coefficient caused by the DC bias of the grid, and ϕdo is an initial phase angle caused by the DC bias of the grid.
Step 7: brief introduction of step 4, step 5 and step 6 indicates that the grid has static errors in the estimation of the grid phase angle caused by voltage amplitude imbalance, high harmonics in the grid and DC bias; in order to eliminate the static errors, integrating the information of voltage amplitude imbalance, high harmonics in the grid and DC bias in the grid into the grid synchronization (phase-locked loop) module shown in
wherein
b is the gain coefficient of control input, u is the control input, b0 is the estimated value of the gain coefficient of the control input, ω is grid frequency, {circumflex over (ω)} is the estimated value of the grid frequency, dtotal is total disturbance, dPU is disturbance caused by voltage imbalance, dVO is disturbance caused by voltage DC bias, dVH is disturbance caused by voltage high harmonics, and dLIN is disturbance caused by linearization.
Step 8: designing the grid phase angle tracker based on nonlinear active disturbance rejection based on formula (9), as shown in
wherein fal(e1, αi)=|e1|α
Wherein νd* is the reference value of νd, kp is a proportionality coefficient, z1 is the estimated value of x1, z2 is the estimated value of x2, and L1 and L2 are the gain coefficients of the generalized integral nonlinear extended state observer; z2(ω
Step 9: in MATLAB/Simulink environment, building an aircraft grid model and building the aircraft grid phase tracker based on nonlinear active disturbance rejection by a modular modeling technology; verifying the performance of the aircraft grid phase angle tracker based on nonlinear active disturbance rejection; and comparing the estimation error of the aircraft grid phase angle tracker based on nonlinear active disturbance rejection with the estimation error of the aircraft grid phase angle tracker based on linear active disturbance rejection; for the fast varying sinusoidal disturbance of the grid, the accuracy of the aircraft grid phase angle tracker based on nonlinear active disturbance rejection is higher, the convergence rate of the tracking error of the grid phase angle is higher, and the attenuation capacity for sinusoidal disturbance is strong, as shown in
Number | Date | Country | Kind |
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202110149481.2 | Feb 2021 | CN | national |
Filing Document | Filing Date | Country | Kind |
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PCT/CN2021/077161 | 2/22/2021 | WO |
Publishing Document | Publishing Date | Country | Kind |
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WO2022/165861 | 8/11/2022 | WO | A |
Number | Name | Date | Kind |
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10985668 | Banceanu | Apr 2021 | B2 |
11342862 | Al-Areqi | May 2022 | B2 |
20080011091 | Weldon | Jan 2008 | A1 |
20190199213 | Jaldanki | Jun 2019 | A1 |
20190288611 | Li | Sep 2019 | A1 |
Number | Date | Country |
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107831365 | Mar 2018 | CN |
108599261 | Sep 2018 | CN |
109473983 | Mar 2019 | CN |
Entry |
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Office Action and Search Report corresponding to Chinese application No. 202110149481.2 dated Sep. 30, 2021 (with English translation), pp. 14. |
Notification of Grant corresponding to Chinese application No. 202110149481.2 dated Nov. 23, 2021 (with English translation), pp. 5. |
Number | Date | Country | |
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20230003778 A1 | Jan 2023 | US |