AIRCRAFT GRID PHASE ANGLE TRACKER BASED ON NONLINEAR ACTIVE DISTURBANCE REJECTION

Abstract

The present invention belongs to the technical field of aviation electrics and electric power, and provides an aircraft grid phase angle tracker based on nonlinear active disturbance rejection, which is used to estimate the grid phase angle on AC side of an aircraft grid. A embedded generator in the aircraft grid is arranged inside a compressor of an aviation gas turbine engine, and the embedded generator is directly coupled with the aviation gas turbine engine so that the AC frequency of the embedded generator varies with the speed of the aviation gas turbine engine. 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.

Claims

1. An aircraft grid phase angle tracker based on nonlinear active disturbance rejection, which is a grid synchronization module used to estimate the grid phase angle on AC side of an aircraft grid; a embedded generator in the aircraft grid is arranged inside a compressor of an aviation gas turbine engine, and the embedded generator is directly coupled with the aviation gas turbine engine so that the AC frequency of the embedded generator varies with the speed of the aviation gas turbine engine; therefore, a method for estimating a grid phase angle by the aircraft grid phase angle tracker based on nonlinear active disturbance rejection is designed, comprising the following steps: step 1: firstly, defining a coordinate system, and converting AC V.sub.abc in a three-phase stationary rotating coordinate system to a two-phase stationary coordinate system v.sub.αβ and finally to a two-phase rotating coordinate system v.sub.qd; and then controlling v.sub.d=0 to estimate the grid phase angle, and describing conversion relationships between the coordinate systems with formula (1): $\begin{array}{cc}\{\begin{array}{c}{\upsilon }_{\alpha \beta }=T_s.Math.V_{\mathrm{abc}}\\ {\upsilon }_{\mathrm{qd}}=T_e\left(\hat{\theta }\right).Math.{\upsilon }_{\alpha \beta }\end{array}& \left(1\right)\end{array}$ wherein $V_{\mathrm{abc}}={\left[\begin{array}{ccc}{V}_a& V_b& V_c\end{array}\right]}^T,{\upsilon }_{\alpha \beta }={\left[\begin{array}{cc}{\upsilon }_{\alpha }& {\upsilon }_{\beta }\end{array}\right]}^T,{\upsilon }_{\mathrm{qd}}={\left[\begin{array}{cc}{\upsilon }_q& {\upsilon }_d\end{array}\right]}^T,T_s=\frac{2}{3}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& -\frac{\sqrt{3}}{2}& \frac{\sqrt{3}}{2}\end{array}\right],T_e\left(\hat{\theta }\right)=\left[\begin{array}{cc}\cos \left(\hat{\theta }\right)& -\sin \left(\hat{\theta }\right)\\ \sin \left(\hat{\theta }\right)& \cos \left(\hat{\theta }\right)\end{array}\right]$ {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 nominal grid parameters of the more electric aircraft, with a mathematical expression satisfying formula (2): $\begin{array}{cc}\left[\begin{array}{c}{V}_a\\ V_b\\ V_c\end{array}\right]=V_m\left[\begin{array}{c}\cos \left(\theta \right)\\ \cos \left(\theta -\frac{2}{3}\pi \right)\\ \cos \left(\theta +\frac{2}{3}\pi \right)\end{array}\right]& \left(2\right)\end{array}$ wherein V.sub.a, V.sub.b and V.sub.c are voltage of three-phase AC of the aircraft; θ=ωt is the grid phase angle; ω is three-phase AC frequency; and V.sub.m is a three-phase voltage amplitude; converting AC V.sub.abc under the three-phase stationary rotating coordinate system in the formula (2) to the two-phase rotating coordinate system v.sub.qd, and controlling v.sub.d=0 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 and DC bias respectively correspond to mathematical expressions which satisfy formula (3), formula (4) and formula (5); $\begin{array}{cc}\left[\begin{array}{c}{V}_a\\ V_b\\ V_c\end{array}\right]=V_m\left[\begin{array}{c}\cos \left(\theta \right)\\ \left(1+\beta \right)\cos \left(\theta -\frac{2}{3}\pi \right)\\ \left(1+\gamma \right)\cos \left(\theta +\frac{2}{3}\pi \right)\end{array}\right]& \left(3\right)\end{array}$ $\begin{array}{cc}\left[\begin{array}{c}{V}_a\\ V_b\\ V_c\end{array}\right]=\left[\begin{array}{c}{V}_m\cos \left(\theta \right)+u_5\cos \left(5\theta \right)+.Math.+u_{2n-1}\cos \left(\left(2n-1\right)\theta \right)\\ V_m\cos \left(\theta -\frac{2}{3}\pi \right)+u_5\cos \left(5\left(\theta -\frac{2}{3}\pi \right)\right)+.Math.+u_{2n-1}\cos (\left(2n-1\right)\left(\theta -\frac{2}{3}\pi \right)\\ V_m\cos \left(\theta +\frac{2}{3}\pi \right)+u_5\cos \left(5\left(\theta +\frac{2}{3}\pi \right)\right)+.Math.+u_{2n-1}\cos (\left(2n-1\right)\left(\theta +\frac{2}{3}\pi \right)\end{array}\right]& \left(4\right)\end{array}$ $\begin{array}{cc}\left[\begin{array}{c}{V}_a\\ V_b\\ V_c\end{array}\right]=V_m\left[\begin{array}{c}\cos \left(\theta \right)+V_{\mathrm{ao}}\\ \cos \left(\theta -\frac{2}{3}\pi \right)+V_{\mathrm{bo}}\\ \cos \left(\theta +\frac{2}{3}\pi \right)+V_{\mathrm{co}}\end{array}\right]& \left(5\right)\end{array}$ wherein β and γ are respectively the voltage amplitude imbalance coefficients of the aircraft three-phase grid; v.sub.5 is the amplitude of 5th voltage harmonic components of the aircraft three-phase grid, and is the amplitude of 2n−1th voltage harmonic components of the aircraft three-phase grid; V.sub.ao, V.sub.bo and V.sub.co are the voltage DC biases of the aircraft three-phase grid respectively; step 4: considering the condition of voltage amplitude imbalance of the grid, when v.sub.d=0, a static error exists between the estimated value of the grid phase angle and the true value of the grid phase angle, as shown in formula (6); $\begin{array}{cc}\{\begin{array}{c}\theta -\hat{\theta }=E_{\mathrm{pu}}\cos \left(2\theta +{\varphi }_{\mathrm{pu}}\right)\\ E_{\mathrm{pu}}=\sqrt{{\left(\frac{\beta -\gamma }{2\sqrt{3}}\right)}^2+{\left(\frac{\beta +\gamma }{6}\right)}^2}\\ {\varphi }_{\mathrm{pu}}=-{\tan }^{-1}\left(\frac{1}{\sqrt{3}}\frac{\beta +\gamma }{\beta -\gamma }\right)\end{array}& \left(6\right)\end{array}$ wherein {circumflex over (θ)} is the estimated value of the grid phase angle of the aircraft; step 5: considering the situation of high harmonics in the grid, when v.sub.d=0, obtaining a static error between the estimated value of the grid phase angle and the true value of the grid phase angle, as shown in formula (7); $\begin{array}{cc}\{\begin{array}{c}\theta -\hat{\theta }=E_{6h}\sin 6\theta +E_{12h}\sin 6\theta +.Math.+E_{6\mathrm{nh}}\sin 6n\theta \\ E_{6h}=\frac{u_5-u_7}{V_m}\\ E_{12h}=\frac{u_{11}-u_{13}}{V_m}\\ E_{6\mathrm{nh}}=\frac{u_{6n-1}-u_{6n+1}}{V_m}\end{array}& \left(7\right)\end{array}$ wherein v.sub.5 is the amplitude of 5th voltage harmonics, v.sub.7 is the amplitude of 7th voltage harmonics, is the amplitude of 11th voltage harmonics, x.sub.1, is the amplitude of 13th voltage harmonics, is the amplitude of 6n−1th voltage harmonics, V.sub.6n+1 is the amplitude of 6n+1 voltage harmonics, E.sub.6h is the voltage amplitude synthesized by the amplitudes of 5th and 7th harmonic components, E.sub.12h is the voltage amplitude synthesized by the amplitudes of 11th and 13th harmonic components, E.sub.6h, is the voltage amplitude synthesized by the amplitudes of 6n−1 and 6n+1 harmonic components, and n is a positive integer; step 6: considering the situation of DC bias in the grid, when v.sub.d=0, Obtaining a static error between the estimated value of the grid phase angle and the true value of the grid phase angle, as shown in formula (8); $\begin{array}{cc}\{\begin{array}{c}\theta -\hat{\theta }=E_{\mathrm{do}}\cos \left(\theta +{\varphi }_{\mathrm{do}}\right)\\ E_{\mathrm{do}}=\sqrt{\frac{4}{9}{\left(V_{\mathrm{ao}}+V_{\mathrm{bo}}+V_{\mathrm{co}}\right)}^2+\frac{1}{3}{\left(-V_{\mathrm{bo}}+V_{\mathrm{co}}\right)}^2}\\ {\varphi }_{\mathrm{do}}=-{\tan }^{-1}\left(\frac{2}{3\sqrt{3}}\frac{V_{\mathrm{ao}}+V_{\mathrm{bo}}+V_{\mathrm{co}}}{-V_{\mathrm{bo}}+V_{\mathrm{co}}}\right)\end{array}& \left(8\right)\end{array}$ wherein V.sub.ao, V.sub.bo and V.sub.co are the voltage DC biases of the aircraft three-phase grid respectively, E.sub.do is an amplitude gain coefficient caused by the DC bias of the grid, and ϕ.sub.do is an initial phase angle caused by the DC bias of the grid; step 7: step 4, step 5 and step 6 indicate that the grid has static errors in the estimation of the grid phase angle caused by voltage amplitude imbalance, high harmonics and DC bias; in order to eliminate the static errors, integrating the information of voltage amplitude imbalance, high harmonics and DC bias in the grid into the grid synchronization module; according to the principle of linear superposition, superimposing the information of step 4, step 5 and step 6 into formula (9) to obtain a nominal mathematical model required by the aircraft grid phase angle tracker based on nonlinear active disturbance rejection, as shown in formula (9); $\begin{array}{cc}\{\begin{array}{c}{x}_1^{\&}=b_{0}u+x_2,\\ x_2^{\&}=-q\end{array}.& \left(9\right)\end{array}$ wherein $x_1=\frac{{\upsilon }_d}{V_m},x_2=\left(b-b_0\right)\left(\hat{\omega }-\omega \right)+\frac{d_{\mathrm{total}}}{V_m},u=\hat{\omega }-\omega .d_{\mathrm{total}}=d_{\mathrm{PU}}^{\&}+d_{\mathrm{VO}}^{\&}+d_{\mathrm{VH}}^{\&}+d_{\mathrm{LIN}}^{\&}{d}_{\mathrm{PU}}=V_m\left[\frac{\beta -\gamma }{2\sqrt{3}}\cos \left(2\theta \right)-\frac{\beta +\gamma }{6}\sin \left(2\theta \right)\right],d_{\mathrm{VO}}=E_{\mathrm{do}}\cos \left(\theta +{\varphi }_{\mathrm{do}}\right),d_{\mathrm{VH}}=V_m{E}_{6h}\sin 6\theta +V_m{E}_{12h}\sin 6\theta +.Math.+V_m{E}_{6\mathrm{nh}}\sin 6n\theta ,d_{\mathrm{LIN}}=-\left(\frac{\beta +\gamma }{3}+1\right)V_m\sin \left(\theta -\hat{\theta }\right)+\left(\frac{\beta +\gamma }{3}+1\right)V_m\left(\theta -\hat{\theta }\right)$ wherein b is the gain coefficient of control input, u is the control input, b.sub.0 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, d.sub.total is total disturbance, d.sub.PU is disturbance caused by voltage imbalance, d.sub.VO is disturbance caused by voltage DC bias, d.sub.VH is disturbance caused by voltage high harmonics, and d.sub.LIN is disturbance caused by linearization; step 8: designing the aircraft grid phase angle tracker based on nonlinear active disturbance rejection based on formula (9), which is composed of formula (10) and formula (11); formula (10) is a linear state error feedback law, and formula (11) is a generalized integral nonlinear extended state observer; u calculated in formula (10) is a difference value between the estimated grid frequency and the real grid frequency; the real grid frequency ω is equal to the sum of u and the speed of the aviation gas turbine engine; since the speed of the aviation gas turbine engine can be measured by sensors, the information is known; special attention is paid to that the unit of the speed of the aviation gas turbine engine here should exist in the form of rad/s; and finally, integral calculation is conducted on ω to obtain the phase angle of the aircraft grid; $\begin{array}{cc}\{\begin{array}{c}{e}_2={\upsilon }_d^{*}-{\upsilon }_d\\ u=\frac{u_0+k_p\int \underset{i=1}{\overset{3}{.Math.}}{z}_{2\left({\omega }_{\mathrm{ri}}\right)}\mathrm{dt}-z_{2\left(0\right)}}{b_0}\\ u_0=k_p.Math.e_2\end{array}& \left(10\right)\end{array}$ $\begin{array}{cc}\{\begin{array}{c}{e}_1=z_1-x_1\\ z_1^{\&}=z_2-L_1.Math.e_1+b_{0}u\\ z_2^{\&}=-L_2.Math.\mathrm{fal}\left(e_1,{\alpha }_1\right)+g_1+g_2+g_3\\ d_1^{\&}=g_1\\ d_2^{\&}=g_2\\ d_3^{\&}=g_3\\ g_1^{\&}=-{\omega }_{r1}^2{d}_1+u_1^{\&}{K}_{r1}\\ g_2^{\&}=-{\omega }_{r2}^2{d}_2+u_1^{\&}{K}_{r2}\\ g_3^{\&}=-{\omega }_{r3}^2{d}_3+u_1^{\&}{K}_{r3}\\ u_1=-L_2.Math.\mathrm{fal}\left(e_1,{\alpha }_2\right)\end{array}& \left(11\right)\end{array}$ wherein fal(e.sub.1, α.sub.i)=|e.sub.1|.sup.α.sup.i sign(e.sub.1), i∈{1, 2, 3, 4, 5} wherein v.sub.d* is the reference value of v.sub.d, k.sub.p is a proportionality coefficient, Z.sub.1 is the estimated value of x.sub.1, z.sub.2 is the estimated value of X.sub.2, and L.sub.1 and L.sub.2 are the gain coefficients of the generalized integral nonlinear extended state observer; z.sub.2(ω.sub.r1.sub.)=∫g.sub.1dt; z.sub.2(ω.sub.r2.sub.)=∫g.sub.2dt, z.sub.2(ω.sub.r3.sub.)=∫g.sub.3dt and z.sub.2(0) are unmodeled dynamic estimated values; z.sub.2(ω.sub.r1.sub.)=d.sub.1; z.sub.2(ω.sub.r2.sub.)=d.sub.2; z.sub.2(ω.sub.r3.sub.)=d.sub.3; d.sub.1.sup.& is the derivative of the time of d.sub.1; d.sub.2.sup.& is the derivative of the time of d.sub.2; d.sub.3.sup.& is the derivative of the time of d.sub.3; ω.sub.r1=ω is frequency compensation in the case of DC bias in grid voltage; K.sub.r1 is the gain coefficient of the frequency compensation; ω.sub.r2=2ω is frequency compensation in the case of grid voltage imbalance; K.sub.r2 is the gain coefficient of the frequency compensation; ω.sub.r3=6ω is frequency compensation in the case of the high harmonics in the grid voltage; K.sub.r3 is the gain coefficient of the frequency compensation; u.sub.1.sup.& is the derivative of time of u.sub.1; and α.sub.1 and α.sub.2 are real numbers between 0 and 1.

Description

DESCRIPTION OF DRAWINGS

[0025] FIG. 1 is a local structural block diagram of an aircraft grid.

[0026] FIG. 2 is a whole block diagram of an aircraft grid phase angle tracker.

[0027] FIG. 3 is a schematic diagram of an aircraft grid phase angle tracker based on nonlinear active disturbance rejection.

[0028] FIG. 4 is a schematic diagram of a generalized integral nonlinear extended state observer (GI-ESO) of nonlinear active disturbance rejection.

[0029] FIG. 5(a) is a whole schematic diagram of comparison of grid phase angle errors between two grid phase trackers.

[0030] FIG. 5(b) is a local schematic diagram of comparison of grid phase angle errors between two grid phase trackers.

[0031] FIG. 5(c) is a local schematic diagram of comparison of grid phase angle errors between two grid phase trackers.

[0032] FIG. 5(d) is a local schematic diagram of comparison of grid phase angle errors between two grid phase trackers.

[0033] FIG. 5(e) is a local schematic diagram of comparison of grid phase angle errors between two grid phase trackers.

[0034] FIG. 6 is a comparison diagram of calculated values of grid phase angle errors under integral of time multiplied by the absolute value of error criterion.

DETAILED DESCRIPTION

[0035] 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.

[0036] 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 FIG. 1, is used to estimate the grid phase angle on AC side of an aircraft grid; a embedded generator in the aircraft grid is arranged inside a compressor of an aviation gas turbine engine, and the embedded generator is directly coupled with the aviation gas turbine engine so that the AC frequency of the embedded generator varies with the speed of the aviation gas turbine engine; three-phase AC generated by an AC generator can be specifically describe as

[00001]$V_a=V_m\cos \left(\omega t\right),V_b=V_m\cos \left(\omega t-\frac{2}{3}\pi \right)\mathrm{and}{V}_c=V_m\cos \left(\omega t+\frac{2}{3}\pi \right),$

wherein V.sub.m is the amplitude of the three-phase AC; V.sub.a, V.sub.b and V.sub.c indicate three-phase AC respectively; φ 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:

[0037] Step 1: to facilitate analysis, firstly, defining a coordinate system for the purpose of converting AC V.sub.abc in a three-phase stationary rotating coordinate system to a two-phase stationary coordinate system v.sub.αβ, and finally to a two-phase rotating coordinate system v.sub.qd; the ultimate purpose of converting to the two-phase rotating coordinate system is to control v.sub.d=0 to lay a foundation for estimating the grid phase angle indirectly, and conversion relationships between the coordinate systems are described with formula (1):

[00002]$\begin{array}{cc}\{\begin{array}{c}{\upsilon }_{\alpha \beta }=T_s.Math.V_{\mathrm{abc}}\\ {\upsilon }_{\mathrm{qd}}=T_e\left(\hat{\theta }\right).Math.{\upsilon }_{\alpha \beta }\end{array}& \left(1\right)\end{array}$

[0038] wherein

[00003]$V_{\mathrm{abc}}={\left[\begin{array}{ccc}{V}_a& V_b& V_c\end{array}\right]}^T,{\upsilon }_{\mathrm{\alpha \beta }}={\left[\begin{array}{cc}{\upsilon }_{\alpha }& {\upsilon }_{\beta }\end{array}\right]}^T,{\upsilon }_{\mathrm{qd}}={\left[\begin{array}{cc}{\upsilon }_q& {\upsilon }_d\end{array}\right]}^T,T_s=\frac{2}{3}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& -\frac{\sqrt{3}}{2}& -\frac{\sqrt{3}}{2}\end{array}\right],T_e\left(\hat{\theta }\right)=\left[\begin{array}{cc}\cos \left(\hat{\theta }\right)& -\sin \left(\hat{\theta }\right)\\ \sin \left(\hat{\theta }\right)& \cos \left(\hat{\theta }\right)\end{array}\right]$

{circumflex over (θ)} is an estimated value of the grid phase angle.

[0039] 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):

[00004]$\begin{array}{cc}\left[\begin{array}{c}{V}_a\\ V_b\\ V_c\end{array}\right]=V_m\left[\begin{array}{c}\cos \left(\theta \right)\\ \cos \left(\theta -\frac{2}{3}\pi \right)\\ \cos \left(\theta +\frac{2}{3}\pi \right)\end{array}\right]& \left(2\right)\end{array}$

[0040] wherein V.sub.a, V.sub.b, and V.sub.c are voltage of three-phase AC of the aircraft respectively; θ=ωt is the grid phase angle; φ is three-phase AC frequency; and V.sub.m is a three-phase voltage amplitude. AC V.sub.abc under the three-phase stationary rotating coordinate system in the formula (2) is converted to the two-phase rotating coordinate system v.sub.qd, and v.sub.d=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.

[0041] 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);

[00005]$\begin{array}{cc}\left[\begin{array}{c}{V}_a\\ V_b\\ V_c\end{array}\right]=V_m\left[\begin{array}{c}\cos \left(\theta \right)\\ \left(1+\beta \right)\cos \left(\theta -\frac{2}{3}\pi \right)\\ \left(1+\gamma \right)\cos \left(\theta +\frac{2}{3}\pi \right)\end{array}\right]& \left(3\right)\end{array}$$\begin{array}{cc}\left[\begin{array}{c}{V}_a\\ V_b\\ V_c\end{array}\right]=\left[\begin{array}{c}{V}_m\cos \left(\theta \right)+v_5\cos \left(5\theta \right)+.Math.+v_{2n-1}\cos \left(\left(2n-1\right)\theta \right)\\ V_m\cos \left(\theta -\frac{2}{3}\pi \right)+v_5\cos \left(5\left(\theta -\frac{2}{3}\pi \right)\right)+.Math.+v_{2n-1}\cos (\left(2n-1\right)\left(\theta -\frac{2}{3}\pi \right)\\ V_m\cos \left(\theta +\frac{2}{3}\pi \right)+v_5\cos \left(5\left(\theta +\frac{2}{3}\pi \right)\right)+.Math.+v_{2n-1}\cos (\left(2n-1\right)\left(\theta +\frac{2}{3}\pi \right)\end{array}\right]& \left(4\right)\end{array}$$\begin{array}{cc}\left[\begin{array}{c}{V}_a\\ V_b\\ V_c\end{array}\right]=V_m\left[\begin{array}{c}\cos \left(\theta \right)+V_{ao}\\ \cos \left(\theta -\frac{2}{3}\pi \right)+V_{bo}\\ \cos \left(\theta +\frac{2}{3}\pi \right)+V_{co}\end{array}\right]& \left(5\right)\end{array}$

[0042] wherein β and γ are respectively the voltage amplitude imbalance coefficients of the aircraft three-phase grid. v.sub.5 is the amplitude of 5th voltage harmonic components of the aircraft three-phase grid, and is the amplitude of 2n−1th voltage harmonic components of the aircraft three-phase grid; V.sub.ao, V.sub.bo and V.sub.co are the voltage DC biases of the aircraft three-phase grid respectively.

[0043] Second step, design of the grid phase angle tracker; Step 4: considering the condition of voltage amplitude imbalance of the grid, when v.sub.d=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 (6);

[00006]$\begin{array}{cc}\{\begin{array}{c}\theta -\hat{\theta }=E_{\mathrm{pu}}\cos \left(2\theta +{\varphi }_{\mathrm{pu}}\right)\\ E_{\mathrm{pu}}=\sqrt{{\left(\frac{\beta -\gamma }{2\sqrt{3}}\right)}^2+{\left(\frac{\beta -\gamma }{6}\right)}^2}\\ {\varphi }_{\mathrm{pu}}=-{\tan }^{-1}\left(\frac{1}{\sqrt{3}}\frac{\beta +\gamma }{\beta -\gamma }\right)\end{array}& \left(6\right)\end{array}$

[0044] wherein {circumflex over (θ)} is the estimated value of the aircraft grid phase angle; E.sub.pu is an amplitude gain coefficient caused by the voltage imbalance; and ϕ.sub.pu is an initial phase angle caused by the voltage imbalance.

[0045] Step 5: considering the situation of high harmonics in the grid, when v.sub.d=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);

[00007]$\begin{array}{cc}\{\begin{array}{c}\theta -\hat{\theta }=E_{\mathrm{pu}}\cos \left(2\theta +{\varphi }_{\mathrm{pu}}\right)\\ E_{\mathrm{pu}}=\sqrt{{\left(\frac{\beta -\gamma }{2\sqrt{3}}\right)}^2+{\left(\frac{\beta +\gamma }{6}\right)}^2}\\ {\varphi }_{\mathrm{pu}}=-{\tan }^{-1}\left(\frac{1}{\sqrt{3}}\frac{\beta +\gamma }{\beta -\gamma }\right)\end{array}& \left(6\right)\end{array}$

[0046] wherein v.sub.5 is the amplitude of 5th voltage harmonics, v.sub.7 is the amplitude of 7th voltage harmonics, v.sub.11 is the amplitude of 11th voltage harmonics, v.sub.13 is the amplitude of 13th voltage harmonics, is the amplitude of 6n−1th voltage harmonics, V.sub.6n+1 is the amplitude of 6n+1th voltage harmonics, E.sub.6h is the voltage amplitude synthesized by the amplitudes of 5th and 7th harmonic components, E.sub.12h is the voltage amplitude synthesized by the amplitudes of 11th and 13th harmonic components, E.sub.6h, is the voltage amplitude synthesized by the amplitudes of 6n−1th and 6n+1th harmonic components, and n is a positive integer;

[0047] Step 6: considering the situation of DC bias in the grid, when v.sub.d=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 (8);

[00008]$\begin{array}{cc}\{\begin{array}{c}\theta -\hat{\theta }=E_{\mathrm{do}}\cos \left(\theta +{\varphi }_{\mathrm{do}}\right)\\ E_{\mathrm{do}}=\sqrt{\frac{4}{9}{\left(V_{\mathrm{ao}}+V_{\mathrm{bo}}+V_{\mathrm{co}}\right)}^2+\frac{1}{3}{\left(-V_{\mathrm{bo}}+V_{\mathrm{co}}\right)}^2}\\ {\varphi }_{\mathrm{do}}=-{\tan }^{-1}\left(\frac{2}{3\sqrt{3}}\frac{V_{\mathrm{ao}}+V_{\mathrm{bo}}+V_{\mathrm{co}}}{-V_{\mathrm{bo}}+V_{\mathrm{co}}}\right)\end{array}& \left(8\right)\end{array}$

[0048] wherein V.sub.ao, V.sub.bo and V.sub.co are the voltage DC biases of the aircraft three-phase grid respectively, E.sub.do is an amplitude gain coefficient caused by the DC bias of the grid, and ϕ.sub.do is an initial phase angle caused by the DC bias of the grid.

[0049] 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 FIG. 1; the traditional proportional integral grid phase angle tracker/the proportional integral differential grid phase angle tracker cannot integrate the model information into the grid synchronization (phase-locked loop) module and has poor anti-interference capability; thus, a grid phase angle tracker based on nonlinear active disturbance rejection of model information needs to be designed. Before the grid phase tracker is designed, according to the principle of linear superposition, the information of step 4, step 5 and step 6 is superimposed into formula (9) to obtain a nominal mathematical model required by the grid phase angle tracker based on nonlinear active disturbance rejection, as shown in formula (9);

[00009]$\begin{array}{cc}\{\begin{array}{c}{x}_1^{\&}=b_{0}u+x_2,\\ x_2^{\&}=-q\end{array}.& \left(9\right)\end{array}$

wherein

[00010]$x_1=\frac{{\upsilon }_d}{V_m},x_2=\left(b-b_0\right)\left(\hat{\omega }-\omega \right)+\frac{d_{\mathrm{total}}}{V_m},u=\hat{\omega }-\omega .d_{\mathrm{total}}=d_{\mathrm{PU}}^{\&}+d_{\mathrm{VO}}^{\&}+d_{\mathrm{VH}}^{\&}+d_{\mathrm{LIN}}^{\&}{d}_{\mathrm{PU}}=V_m\left[\frac{\beta -\gamma }{2\sqrt{3}}\cos \left(2\theta \right)-\frac{\beta +\gamma }{6}\sin \left(2\theta \right)\right],d_{\mathrm{VO}}=E_{\mathrm{do}}\cos \left(\theta +{\varphi }_{\mathrm{do}}\right),d_{\mathrm{VH}}=V_m{E}_{6h}\sin 6\theta +V_m{E}_{12h}\sin 6\theta +.Math.+V_m{E}_{6\mathrm{nh}}\sin 6n\theta ,d_{\mathrm{LIN}}=-\left(\frac{\beta +\gamma }{3}+1\right)V_m\sin \left(\theta -\hat{\theta }\right)+\left(\frac{\beta +\gamma }{3}+1\right)V_m\left(\theta -\hat{\theta }\right).$

b is the gain coefficient of control input, u is the control input, b.sub.0 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, d.sub.total is total disturbance, d.sub.PU is disturbance caused by voltage imbalance, d.sub.VO is disturbance caused by voltage DC bias, d.sub.VH is disturbance caused by voltage high harmonics, and d.sub.LIN is disturbance caused by linearization.

[0050] Step 8: designing the grid phase angle tracker based on nonlinear active disturbance rejection based on formula (9), as shown in FIG. 3, which is composed of formula (10) and formula (11); formula (10) is a linear state error feedback law, and formula (11) is a generalized integral nonlinear extended state observer (GI-ESO); formula (11) corresponds to FIG. 4; u calculated in formula (10) is a difference value between the estimated grid frequency and the real grid frequency; the real grid frequency ω is equal to the sum of U and the speed of the aviation gas turbine engine; since the speed of the aviation gas turbine engine can be measured by sensors, the information is known; special attention is paid to that the unit of the speed of the aviation gas turbine engine here should exist in the form of rad/s; and finally, integral calculation is conducted on ω to obtain the phase angle of the aircraft grid. Special note: the nonlinear switching function fal(e.sub.1α.sub.i) is introduced to perform nonlinear transformation on the observation error e.sub.1. Compared with the generalized integral linear extended state observer, nonlinear functions are introduced so that the observation efficiency of the generalized integral nonlinear extended state observer can be increased;

[00011]$\begin{array}{cc}\{\begin{array}{c}{e}_2={\upsilon }_d^{*}-{\upsilon }_d\\ u=\frac{u_0+k_p\int \underset{i=1}{\overset{3}{.Math.}}{z}_{2\left({\omega }_{\mathrm{ri}}\right)}\mathrm{dt}-z_{2\left(0\right)}}{b_0}\\ u_0=k_p.Math.e_2\end{array}& \left(10\right)\end{array}$$\begin{array}{cc}\{\begin{array}{c}{e}_1=z_1-x_1\\ z_1^{\&}=z_2-L_1.Math.e_1+b_{0}u\\ z_2^{\&}=-L_2.Math.\mathrm{fal}\left(e_1,{\alpha }_1\right)+g_1+g_2+g_3\\ d_1^{\&}=g_1\\ d_2^{\&}=g_2\\ d_3^{\&}=g_3\\ g_1^{\&}=-{\omega }_{r1}^2{d}_1+u_1^{\&}{K}_{r1}\\ g_2^{\&}=-{\omega }_{r2}^2{d}_2+u_1^{\&}{K}_{r2}\\ g_3^{\&}=-{\omega }_{r3}^2{d}_3+u_1^{\&}{K}_{r3}\\ u_1=-L_2.Math.\mathrm{fal}\left(e_1,{\alpha }_2\right)\end{array}& \left(11\right)\end{array}$

[0051] wherein fal(e.sub.1, α.sub.i)=|e.sub.1|.sup.α.sup.i sign(e.sub.1), i∈{1, 2, 3, 4, 5}.

[0052] Wherein v.sub.d* is the reference value of v.sub.d, k.sub.p is a proportionality coefficient, z.sub.1 is the estimated value of x.sub.1, z.sub.2 is the estimated value of x.sub.2, and L.sub.1 and L.sub.2 are the gain coefficients of the generalized integral nonlinear extended state observer; z.sub.2(ω.sub.r1.sub.)=∫g.sub.1dt; z.sub.2(ω.sub.r2.sub.)=∫g.sub.2dt, z.sub.2(ω.sub.r3.sub.)=∫g.sub.3dt and z.sub.2(0) are unmodeled dynamic estimated values; z.sub.2(ω.sub.r1.sub.)=d.sub.1; z.sub.2(ω.sub.r2.sub.)=d.sub.2; z.sub.2(ω.sub.r3.sub.)=d.sub.3; d.sub.1.sup.& is the derivative of the time of d.sub.1; d.sub.2.sup.& is the derivative of the time of d.sub.2; D.sub.3.sup.& is the derivative of the time of d.sub.3; ω.sub.r1=ω is frequency compensation in the case of DC bias in grid voltage; K.sub.r1 is the gain coefficient of the frequency compensation; ω.sub.r2=2ω is frequency compensation in the case of grid voltage imbalance; K.sub.r2 is the gain coefficient of the frequency compensation; ω.sub.r3=6ω is frequency compensation in the case of the high harmonics in the grid voltage; K.sub.r3 is the gain coefficient of the frequency compensation; Z is the derivative of time of u.sub.1; and α.sub.1 and α.sub.2 are real numbers between 0 and 1.

[0053] 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 FIG. 5 and FIG. 6. If the calculated value under the integral of time multiplied by the absolute value of error criterion in FIG. 6 is smaller, the performance of the grid phase angle tracker is better, which indicates that the method proposed by the present invention can accurately estimate the grid phase angle.