Design method of amplitude-phase corrector for suppressing flexible direct-current broadband oscillation and related device

Abstract

The invention discloses a design method of an amplitude-phase corrector for suppressing flexible direct-current broadband oscillation. The design method comprises the following steps: acquiring a power grid frequency characteristic curve; constructing impedance transfer functions of an alternating-current power grid side and a current converter side; determining a frequency point which is unstable or low in stability margin; according to the type of the required amplitude-phase corrector, determining a total impedance function of one side containing the amplitude-phase corrector; setting a plurality of frequency points to be corrected; presetting a target phase frequency characteristic curve after actual correction; calculating a phase value of the total impedance function at a frequency point needing to be corrected, and obtaining a target phase frequency characteristic curve after quasi-correction; and constructing a frequency difference objective function according to the target phase frequency characteristic curve subjected to the quasi-correction and the target amplitude phase frequency characteristic curve subjected to the actual correction, and solving to obtain an element parameter value. According to the amplitude-phase corrector designed by the method, the broadband domain range of a system containing the flexible direct current can be stable under the condition that the phase margin is given, so that the problem of broadband oscillation of the flexible direct current is fundamentally solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of direct current transmission, and particularly relates to a design method of a phase-amplitude corrector for flexible direct current wide frequency oscillation suppression. BACKGROUND

[0002] In recent years, with the wide promotion of flexible direct current transmission technology in different application occasions, there have been multiple wide frequency oscillation problems that have not occurred in previous alternating current and conventional direct current projects. For example, in 2015, a 23.6-25.2 Hz low frequency oscillation of direct current occurred in the Xiamen project, in 2017, a 1.2 kHz high frequency oscillation occurred in the Luxi project, and subsequently, a wide frequency oscillation from tens to thousands of Hz occurred in many projects such as the Chongqing-Ezhou back-to-back project and the Zhoushan project. These wide frequency oscillations seriously affect the safe and stable operation of the AC / DC system, and may cause overvoltage insulation breakdown and other hazards to important equipment such as converter transformers and converter valves, which has been paid attention to by power grid operation departments. The reason for the wide frequency oscillation is that in the control system of the flexible direct current, under the comprehensive action of the transfer function link and the delay link, a phase shift of 180° or more may occur between the input and output of the control loop at a specific frequency, which is equivalent to introducing negative damping to amplify the harmonics at these frequencies, so that the system is unstable at these frequencies, causing oscillation.

[0003] The phase-amplitude corrector is a new means for suppressing wide frequency oscillation of the flexible direct current system, and has been applied in the Baihetan-Jiangsu UHVDC project. The phase-amplitude corrector can adjust the impedance of the flexible direct current converter, the AC power grid and the new energy system, adjust the amplitude and phase frequency characteristics of the system, and adjust the phase shift between the input and output of the original control loop to within 180°, so as to solve the problem of wide frequency oscillation of the flexible direct current.

[0004] The phase-amplitude corrector usually includes two categories of series type and parallel type, and each category contains multiple common types of structures. In these forms of structures, the phase-amplitude corrector is usually composed of a total of 2-7 resistors, capacitors and reactors through various series and parallel connections, and the selection of the structure form and the calculation of the device element parameters are the key to determining whether the phase-amplitude corrector can ensure the stability of the power grid system containing the flexible direct current in the wide frequency band.

[0005] The inventor has found through research that, in the prior art, although various application occasions, configuration principles and parameter calculation methods of series or parallel amplitude-phase correctors are given, the given methods are mostly referenced from traditional series reactive compensation devices and parallel filters, only a few parameters are designed at resonance points, and the expected corrected system amplitude-phase frequency characteristics are not considered in the parameter calculation, so the designed amplitude-phase correctors do not necessarily meet the system characteristic requirements such as stability in a wide frequency range, and need to be repeatedly manually adjusted and redesigned. Therefore, a method for optimizing design of amplitude-phase corrector element parameters according to the requirements of the expected corrected system amplitude-phase frequency characteristics under the consideration of a certain phase angle margin is needed. SUMMARY

[0006] The purpose of the present application is to provide a design method of an amplitude-phase corrector for flexible DC wide frequency oscillation suppression in a flexible DC power transmission project.

[0007] The method is based on the criterion principle of stability of the amplitude-phase frequency characteristics of the DC side and the AC side of the flexible DC system, a target amplitude-phase frequency characteristic curve with sufficient stability margin is designed, and intelligent algorithms such as genetic algorithms are applied to optimize calculation of the parameters of various types of series and parallel amplitude-phase correctors, so that the designed amplitude-phase corrector can make the system containing flexible DC stable in a wide frequency range under a given phase margin, thereby fundamentally solving the problem of flexible DC wide frequency oscillation.

[0008] The technical solution adopted by the present application is that: a design method of an amplitude-phase corrector for flexible DC wide frequency oscillation suppression, comprising:

[0009] Obtaining a power grid frequency characteristic curve;

[0010] According to the power grid frequency characteristic curve, an AC power grid side impedance transfer function and a converter side impedance transfer function are constructed;

[0011] According to the AC power grid side impedance transfer function and the converter side impedance transfer function, determine the frequency points that are unstable or have low stability margin;

[0012] According to the type of the required amplitude-phase corrector, determine the undetermined coefficients parms in the amplitude-phase corrector element parameters and construct an amplitude-phase corrector transfer function with undetermined coefficients, and then obtain the total impedance function containing the amplitude-phase corrector side;

[0013] According to the frequency points that are unstable or have low stability margin, set a plurality of frequency points that need to be corrected;

[0014] A preset actual corrected target phase frequency characteristic curve is set, and a corresponding phase correction value is set for each correction frequency point to ensure that the target phase at each correction frequency point on the actual corrected target phase frequency characteristic curve is less than 180°;

[0015] The phase value of the total impedance function at the correction frequency point is calculated to obtain a target phase frequency characteristic curve after correction;

[0016] According to the target phase frequency characteristic curve after correction and the actual corrected target amplitude and phase frequency characteristic curve, a frequency difference target function is constructed;

[0017] The minimum value of the frequency difference target function is calculated, and the corresponding undetermined coefficient is obtained, that is, the element parameter value of the amplitude and phase corrector is obtained.

[0018] The grid frequency characteristic curve is obtained, specifically:

[0019] The actual or simulated alternating current side grid and the MMC converter are respectively subjected to frequency scanning, and the amplitude and phase frequency characteristic curves A grid (ω0), φ grid (ω0), A MMC (ω0), φ MMC (ω0) of the alternating current grid side and the MMC converter side are obtained, and the frequency range is 50Hz to 5000Hz; wherein ω0 is the frequency point of the frequency characteristic curve, A grid (ω0), φ grid (ω0) is the amplitude and phase frequency characteristic curve of the grid side, A MMC (ω0), φ MMC (ω0) is the amplitude and phase frequency characteristic curve of the MMC converter side, and is stored in the form of point set of (angular frequency, amplitude) and (angular frequency, phase).

[0020] The grid frequency characteristic curve is obtained, specifically:

[0021] The amplitude and phase frequency characteristic curves A grid (ω0), φ grid (ω0), A MMC (ω0), φ MMC (ω0) of the alternating current grid side and the MMC converter side are obtained, and the frequency range is 50Hz to 5000Hz; wherein ω0 is the frequency point of the frequency characteristic curve, A grid (s), and the MMC converter side impedance transfer function Z MMC (s) are fitted respectively using a nonlinear transfer function fitting method.

[0022] The frequency point of instability or low stability margin is determined according to the AC grid-side impedance transfer function and the converter-side impedance transfer function, and specifically is:

[0023] The difference between the two impedance transfer functions is calculated as ΔZ(s)=Z MMC (s)-Z grid (s), the frequency f of all intersection points between the amplitude-frequency characteristic curves of the two and the x-axis is recorded, f=ω / 2π, and the phase value corresponding to the phase difference frequency characteristic curve Δφ(ω) is found out, the frequency point of instability with a phase difference greater than 180° and the frequency point of low stability margin with a phase difference of 179°-180° are recorded, and are uniformly referred to as the frequency point of instability or low stability margin ω u .

[0024] According to the type of the required amplitude-phase corrector, the undetermined coefficients in the amplitude-phase corrector element parameters are determined, and an amplitude-phase corrector transfer function with the undetermined coefficients is constructed, and then a total impedance function on the side with the amplitude-phase corrector is obtained, and specifically is:

[0025] According to the actual needs of engineering construction, the type of the amplitude-phase corrector is determined to be a parallel type or a series type;

[0026] According to the type of the amplitude-phase corrector determined, the form of the amplitude-phase corrector is selected, and an amplitude-phase corrector transfer function Z adj (s) with undetermined coefficients is constructed; the resistance, capacitance and inductance element parameters in the expression of the amplitude-phase corrector transfer function Z adj (s) are taken as the undetermined coefficients, and the set of the undetermined coefficients is referred to as parms; and Z adj (s) is regarded as a function of the complex frequency domain variable s and the undetermined coefficients parms, Z adj (parms,s).

[0027] If the type of the amplitude-phase corrector is the parallel type, the total impedance function on the side with the amplitude-phase corrector is Z s (parms,s)=Z grid (s)+Z adj (parms,s); if the type of the amplitude-phase corrector is the series type, the total impedance function on the side with the amplitude-phase corrector is Z p (parms,s)=Z MMC (s) / / Z adj (parms,s).

[0028] According to the type of the amplitude-phase corrector determined, the form of the amplitude-phase corrector is selected, and an amplitude-phase corrector transfer function Z adj (s) with undetermined coefficients is constructed, the amplitude-phase corrector transfer function Z adj(s) the resistance, capacitance and inductance element parameters in the expression are expressed as undetermined coefficients, and the set is denoted as parms; specifically including:

[0029] The form of the amplitude and phase corrector is selected according to the principle of first selecting a simple form and then selecting a complex form if the design result does not meet the requirements; if the determined type of the amplitude and phase corrector is a parallel type, the types of the amplitude and phase corrector from simple to complex are a single-tuned type, a double-tuned type and an HP3 type; if the determined type of the amplitude and phase corrector is a series type, the types of the amplitude and phase corrector from simple to complex are an inductive bypass type, a fundamental series resonant type and a specific harmonic parallel resonant type;

[0030] If the form of the amplitude and phase corrector is the single-tuned type, the transfer function Z adj (s) is:

[0031]

[0032] parms={C1, L1}, C1 and L1 are the capacitance and inductance values in the single-tuned type amplitude and phase corrector;

[0033] If the form of the amplitude and phase corrector is the double-tuned type, the transfer function Z adj (s) is:

[0034]

[0035] parms={R1, R2, R3, L1, L2, C1, C2}, R1, R2, R3, L1, L2, C1, C 21 are the resistance, inductance and capacitance values in the double-tuned type amplitude and phase corrector;

[0036] Wherein, the symbol / / represents impedance parallel calculation;

[0037] If the form of the amplitude and phase corrector is the HP3 type, the transfer function Z adj (s) is:

[0038]

[0039] C2 takes a value that resonates with L1 at the fundamental wave, that is, C2 = 1 / (L1ω1 2 ), ω1 is the fundamental wave angular frequency;

[0040] parms={R1, L1, C1}, R1, L1, C1 and C2 are the resistance, inductance and capacitance values in the HP3 type amplitude and phase corrector;

[0041] If the form of the amplitude and phase corrector is the inductive bypass type, the transfer function Z adj (s) is:

[0042]

[0043] parms={R1,L s1},R1,L s1 These are the resistance and inductance values ​​in an inductor-bypass type amplitude-phase corrector.

[0044] If the amplitude-phase compensator is of the fundamental series resonant type, then the transfer function Z of the amplitude-phase compensator is... adj (s) is:

[0045]

[0046] C1 is taken at the fundamental frequency and L s1 The value that forms resonance, i.e., C1 = 1 / (L s1 ω1 2 );

[0047] parms={R1,L s1},R1,L s1 C1 represents the resistance, inductance, and capacitance values ​​in the fundamental series resonant amplitude-phase corrector.

[0048] If the amplitude-phase compensator is of the specific harmonic parallel resonant type, then the transfer function Z of the amplitude-phase compensator is... adj (s) is:

[0049] ;

[0050] C1 is taken at the fundamental frequency and L s1 The value that forms resonance, i.e., C1 = 1 / (L s1 ω1 2 );

[0051] parms={R1,L1,L s1}, R1,L1,L s1 C1 represents the values ​​of resistors, inductors, and capacitors in a specific harmonic parallel resonant amplitude-phase corrector.

[0052] The step of setting multiple frequency points requiring correction based on the unstable or low stability margin frequency points is as follows:

[0053] Based on the frequency point ω that is found to be unstable or has a low stability margin u Within a wide frequency band encompassing these frequency points, multiple frequency points ω to be corrected are set. i (i=1,2,...,n); The principle for setting the frequency points to be corrected is that for each frequency point ω u Set 2N frequency points ω that need to be corrected. i 1≤N≤5, where N frequency points have frequencies less than ω.u N frequency points are greater than ω u .

[0054] The actual corrected target phase frequency characteristic curve is specifically:

[0055] For a series type amplitude-phase corrector, the actual corrected target phase frequency characteristic curve φ target (ω i )=φ grid (ω i )-Δφ seti +Δφ m ;

[0056] For a parallel type amplitude-phase corrector, the actual corrected target phase frequency characteristic curve φ target (ω i )=φ MMC (ω i )-Δφ seti +Δφ m ;

[0057] Wherein, Δφ seti is a phase correction value, Δφ m is a phase margin, φ grid (ω i ) and φ MMC (ω i ) are phase frequency characteristic functions of grid side impedance Z grid (s) and MMC converter side impedance Z MMC (s) respectively when no amplitude-phase corrector is installed.

[0058] The phase value of the total impedance function at the frequency point to be corrected is calculated to obtain a target phase frequency characteristic curve to be corrected, specifically comprising:

[0059] For a series type amplitude-phase corrector, the phase value φ Zs (parms,ω i ) of the series side impedance Z s (parms,s)=Z grid (s)+Z adj (parms,s) at the above-mentioned frequency point ω i (i=1,2,...,n) with undetermined coefficients is calculated, and φ Zs (parms,ω i ) is a target phase frequency characteristic curve to be corrected;

[0060] For a parallel type amplitude-phase corrector, the phase value φ Zs (parms,ω i ) of the parallel side impedance Z p (parms,s)=Z MMC (s) / / Zadj (parms, s) is the phase value φ i (i = 1, 2,..., n) at the above-mentioned frequency points ω Zp (parms, ω i ), φ Zp (parms, ω i ) is the target phase frequency characteristic curve to be corrected.

[0061] The frequency difference target function is specifically:

[0062] For a series type amplitude and phase corrector, the frequency difference target function is:

[0063]

[0064] For a parallel type amplitude and phase corrector, the frequency difference target function is:

[0065] .

[0066] The minimum value of the frequency difference target function is calculated, and the corresponding undetermined coefficient is obtained, that is, the element parameter value of the amplitude and phase corrector is obtained, specifically: the minimum value of the frequency difference target function is calculated by an optimization algorithm, and the corresponding undetermined coefficient is obtained, so that the element parameter value is obtained; the optimization algorithm is a genetic algorithm or an annealing algorithm.

[0067] The application also provides a design device of a flexible direct current wide frequency oscillation suppression amplitude and phase corrector, comprising:

[0068] A curve acquisition module is configured to acquire a power grid frequency characteristic curve.

[0069] A transfer function construction module is configured to construct an alternating current power grid side impedance transfer function and a converter side impedance transfer function according to the power grid frequency characteristic curve.

[0070] A critical region frequency point determination module is configured to determine frequency points with low stability margin or instability according to the alternating current power grid side impedance transfer function and the converter side impedance transfer function.

[0071] A total impedance function construction module is configured to determine an undetermined coefficient parms in an amplitude and phase corrector element parameter according to the type of the required amplitude and phase corrector, construct an amplitude and phase corrector transfer function with the undetermined coefficient, and further obtain a total impedance function containing the amplitude and phase corrector side.

[0072] A required correction frequency point setting module is configured to set a plurality of required correction frequency points according to the frequency points with low stability margin or instability.

[0073] The actual corrected target phase frequency response curve setting module is used to preset an actual corrected target phase frequency response curve and set corresponding phase correction values ​​for each frequency point to be corrected to ensure that the target phase at each frequency point to be corrected on the actual corrected target phase frequency response curve is less than 180°.

[0074] The module for constructing the target phase frequency response curve after correction is used to calculate the phase value of the total impedance function at the frequency point to be corrected, and to obtain the target phase frequency response curve after correction.

[0075] The frequency difference objective function construction module is used to construct the frequency difference objective function based on the target phase frequency characteristic curve to be corrected and the target amplitude and phase frequency characteristic curve to be actually corrected.

[0076] The component parameter value acquisition module calculates the minimum value of the frequency difference objective function and obtains the corresponding undetermined coefficients, thus obtaining the component parameter values ​​of the amplitude-phase corrector.

[0077] The curve acquisition module is specifically used for:

[0078] Frequency scans were performed on both the actual and simulated AC power grid and the MMC converter to obtain the amplitude-phase frequency response curves A of the AC power grid side and the MMC converter side. grid (ω0), φ grid (ω0), A MMC (ω0), φ MMC (ω0), with a frequency range of 50Hz to 5000Hz; where ω0 is the frequency point of the frequency response curve, A grid (ω0), φ grid (ω0) is the amplitude and phase frequency response curve on the grid side, A MMC (ω0), φ MMC (ω0) represents the amplitude and phase frequency response curves on the MMC converter side, which are stored in the form of point sets of (angular frequency, amplitude) and (angular frequency, phase).

[0079] The transfer function construction module is specifically used for:

[0080] A nonlinear transfer function fitting method is used, utilizing the amplitude-phase-frequency characteristic curves A of the AC-side power grid and the MMC converter side. grid (ω0), φ grid (ω0), A MMC (ω0), φ MMC (ω0), respectively fitting the AC grid side impedance transfer function Z grid (s), Converter-side impedance transfer function Z MMC (s).

[0081] The critical region frequency point determination module is specifically configured to:

[0082] The difference between the two impedance transfer functions is ΔZ(s)=Z MMC (s)-Z grid (s), record the frequency f of all intersection points of the amplitude-frequency characteristic curves of the two and the x-axis, f=ω / 2π, and find the corresponding phase value in the phase difference frequency characteristic curve Δφ(ω), record the unstable frequency point with a phase difference greater than 180° and the frequency point with a low stable margin with a phase difference of 179°-180°, and unify them as the unstable or low stable margin frequency point ω u .

[0083] The total impedance function construction module is specifically configured to:

[0084] According to the actual needs of engineering construction, determine whether the amplitude-phase corrector is in parallel or in series;

[0085] According to the type of the amplitude-phase corrector determined, select the form of the amplitude-phase corrector, and construct the amplitude-phase corrector transfer function Z adj (s) with undetermined coefficients; take the resistance, capacitance and inductance element parameters in the expression of the amplitude-phase corrector transfer function Z adj (s) as undetermined coefficients, and let their set be parms; and regard Z adj (s) as a function of the complex frequency domain variable s and the undetermined coefficients parms Z adj (parms,s);

[0086] If the amplitude-phase corrector is in parallel, the total impedance function Z s (parms,s) containing the side of the amplitude-phase corrector is Z grid (s)+Z adj (parms,s); if the amplitude-phase corrector is in series, the total impedance function Z p (parms,s) containing the side of the amplitude-phase corrector is Z MMC (s) / / Z adj (parms,s).

[0087] The required correction frequency point setting module is specifically configured to:

[0088] According to the unstable or low stable margin frequency point ω u found, set a plurality of required correction frequency points ω i (i=1,2,...,n) in a wide frequency band range containing these frequency points; the setting principle of the required correction frequency points is that for each frequency point ω u , 2N required correction frequency points ω i are set, 1≤N≤5, wherein N frequency points are less than ωu N frequency points are greater than ω u .

[0089] The actual corrected target phase frequency characteristic curve is specifically:

[0090] For a series type amplitude-phase corrector, the actual corrected target phase frequency characteristic curve φ target (ω i )=φ grid (ω i )-Δφ seti +Δφ m ;

[0091] For a parallel type amplitude-phase corrector, the actual corrected target phase frequency characteristic curve φ target (ω i )=φ MMC (ω i )-Δφ seti +Δφ m ;

[0092] Wherein, Δφ seti is a phase correction value, Δφ m is a phase margin, φ grid (ω i ), φ MMC (ω i ) are phase frequency characteristic functions of grid side impedance Z grid (s), MMC converter side impedance Z MMC (s) without installing an amplitude-phase corrector.

[0093] The pseudo-corrected target phase frequency characteristic curve construction module is specifically used for:

[0094] For a series type amplitude-phase corrector, the phase value φ s (parms,ω grid ) of the series side impedance Z adj (parms,s)=Z i (s)+Z Zs (parms,s) at the above-mentioned frequency points ω i (i=1,2,...,n) to be corrected is calculated, and φ Zs (parms,ω i ) is a pseudo-corrected target phase frequency characteristic curve;

[0095] For a parallel type amplitude-phase corrector, the parallel side impedance Z p (parms,s)=Z MMC (s) / / Z adjThe phase value φ at the frequency point ω i (i=1,2,...,n) where the frequency difference target function is Zp (parms,ω i ), φ Zp (parms,ω i ) is the target phase frequency characteristic curve to be corrected.

[0096] The frequency difference target function is specifically:

[0097] For a series type amplitude-phase corrector, the frequency difference target function is:

[0098]

[0099] For a parallel type amplitude-phase corrector, the frequency difference target function is:

[0100] .

[0101] The element parameter value obtaining module is specifically configured to: calculate the minimum value of the frequency difference target function by using an optimization algorithm, obtain the corresponding undetermined coefficient , and obtain the element parameter value.

[0102] Another aspect of the present application provides an electronic device, which comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the design method of the amplitude-phase corrector for flexible DC wide frequency oscillation suppression when executing the computer program.

[0103] Another aspect of the present application provides a non-transitory computer readable storage medium, which stores a computer program, and the computer program is executable on a processor to implement the design method of the amplitude-phase corrector for flexible DC wide frequency oscillation suppression.

[0104] Compared with the prior art, the present application has the following advantages:

[0105] The existing amplitude and phase corrector parameter design method is similar to the design method of traditional AC / DC filter, that is, a few pre-set series and parallel resonance points are taken as the target to design the parameters of the amplitude and phase corrector. However, in the actual operation process of the flexible DC transmission project, the system resonance point is not always constant, and the high-frequency resonance point often changes with the power grid operation mode, the converter valve operation mode, the system power flow and other factors; in addition, the actual resonance point may be different from the pre-set value due to the access of the amplitude and phase corrector. In addition, the existing design method cannot be designed under the given stability margin. Therefore, the existing design method has certain randomness and blindness, and the resistance, capacitor and reactor parameters of part of the amplitude and phase corrector need to be manually adjusted repeatedly to have a probability of successful design, and the resonance suppression cannot be guaranteed to be effective in the full frequency range. According to the amplitude and phase frequency characteristic curve of the AC / DC system containing the flexible DC converter, a pre-designed target amplitude and phase frequency characteristic curve is designed artificially, and the system transfer function of the amplitude and phase corrector is constructed based on the target, so as to serve as the target of the amplitude and phase corrector parameter design; and based on the optimization algorithm such as genetic algorithm, the resistance, reactor and capacitor of three series and three parallel amplitude and phase correctors are optimized and designed, so that the corrected system amplitude and phase frequency characteristic curve approximates to the pre-designed target curve as much as possible, and the system stability requirement under the given margin is met.

[0106] In the present application, the corrected target amplitude and phase frequency characteristic curve is pre-designed artificially according to the actual operation requirement and phase margin, and can guarantee to meet the system stability requirement in a wide frequency range. Through the optimization algorithm for the optimization design of the amplitude and phase corrector parameters, the system approximates to the pre-designed target amplitude and phase frequency characteristic curve as much as possible, and has high certainty and operability. BRIEF DESCRIPTION OF DRAWINGS

[0107] Figure 1 The embodiment step flowchart of the present application.

[0108] Figure 2 The impedance schematic diagram of the parallel type amplitude and phase corrector.

[0109] Figure 3 The impedance schematic diagram of the series type amplitude and phase corrector.

[0110] Figure 4 The impedance schematic diagram of the amplitude and phase corrector.

[0111] Figure 5 The basic form of the parallel type amplitude and phase corrector.

[0112] Figure 6 The basic form of the series type amplitude and phase corrector.

[0113] Figure 7 The frequency characteristic curve of the MMC converter side.

[0114] Figure 8 is the frequency characteristic curve of the grid side.

[0115] Figure 9 is the frequency characteristic curve of the difference between the impedance transfer functions of the two sides.

[0116] Figure 10 is the comparison of the correction effect of the amplitude and phase corrector. DETAILED DESCRIPTION

[0117] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0118] The first aspect of the present application provides a contact defect diagnosis method for a double-break disconnecting switch type device, as shown in the following figure, specifically comprising: 1, amplitude and phase corrector design preparation, 2, amplitude and phase corrector structure design, 3, amplitude and phase corrector parameter calculation, 4, amplitude and phase corrector design verification. Figure 1

[0119] 1, Amplitude and phase corrector design preparation

[0120] 1) Obtain the frequency characteristic curve of the grid

[0121] The actual or simulated alternating current side grid and MMC converter are respectively subjected to frequency scanning to obtain the amplitude and phase frequency characteristic curves A grid (ω0) of the alternating current grid side and the MMC converter side grid (ω0) of the alternating current grid side and the MMC converter side MMC (ω0) of the alternating current grid side and the MMC converter side MMC (ω0) of the alternating current grid side and the MMC converter side, and the frequency range is near 50Hz to 5000Hz. Wherein ω0 is the frequency point of the frequency characteristic curve, A grid (ω0) of the alternating current grid side and the MMC converter side grid (ω0) of the alternating current grid side and the MMC converter side MMC (ω0) of the alternating current grid side and the MMC converter side MMC (ω0) of the alternating current grid side and the MMC converter side are stored in the form of point sets of (angular frequency, amplitude) and (angular frequency, phase).

[0122] 2) Construct the impedance transfer function of the alternating current grid side and the converter

[0123] A nonlinear transfer function fitting method is used to utilize the frequency characteristic curves A​grid (ω0), φ grid (ω0), A MMC (ω0), φ MMC (ω0), respectively, fitting the alternating current grid side impedance transfer function Z grid (s), the converter side impedance transfer function Z MMC (s). Wherein, Z grid (s) has 2 poles and 1 zero; Z MMC (s) has 2 poles and 2 zeros. The basic expression is:

[0124]

[0125]

[0126] Wherein, s is a complex variable in the complex frequency domain, a g0 ,a g1 are the coefficients of each order of the denominator of Z grid (s), b g0 ,b g1 ,b g2 are the coefficients of each order of the numerator of Z grid (s), a m0 ,a m1 are the coefficients of each order of the denominator of Z MMC (s), b m0 ,b m1 are the coefficients of each order of the numerator of Z MMC (s).

[0127] According to A grid (ω0), φ grid (ω0) curve fitting alternating current grid side impedance transfer function Z grid (s) method is:

[0128] ① Use the frd function of Python frequency response toolbox to obtain the frequency response complex frequency domain data set of alternating current grid side impedance, the call format is: frd grid (ω0)=frd(G grid (ω0), ω0); Wherein G grid (ω0)=A grid (ω0)e i φgrid(ω0) , where e is the natural logarithm base, i is the unit complex number, φ grid (ω0) take radian.

[0129] ② Use the tfest function of Python nonlinear transfer function fitting toolbox to obtain a grid ,a g0 in Z g1,b g0 ,b g1 ,b g2 Numeric values, called in the format: Z grid (s)=tfest(frd grid (ω0),2,2); where the coefficients 2 and 2 represent the number of zeros and poles, respectively. Using tfest, we can fit the result to obtain a. g0 ,a g1 ,b g0 ,b g1 ,b g2 The value.

[0130] According to A MMC (ω0), φ MMC (ω0) Curved converter-side impedance transfer function Z MMC The method of (s) is:

[0131] ① Use the `frd` function from the Python Frequency Response Toolbox to obtain the complex frequency domain dataset of the converter-side impedance. The calling format is: `frd` MMC (ω0)=frd(G MMC (ω0),ω0); where G MMC (ω0)=A MMC (ω0)e iφMMC(ω0) Where e is the base of the natural logarithm, i is the complex unit, and φ MMC (ω0) is taken in radians.

[0132] ② Use the tfest function from the Python nonlinear transfer function fitting toolbox to obtain Z. MMC a in (s) m0 ,a m1 ,b m0 ,b m1 Numeric values, called in the format: Z MMC (s)=tfest(frd MMC (ω0), 1, 2); where coefficients 1 and 2 represent the number of zeros and poles, respectively. Using tfest, we can fit the result to obtain a. m0 ,a m1 ,b m0 ,b m1 The value.

[0133] 3) Find the frequency point ω that is unstable or has a low stability margin. u

[0134] Find the difference in impedance transfer functions on both sides, ΔZ(s) = Z. MMC (s)-Z grid(s), record the frequency f (f = ω / 2π) of all intersection points of the two amplitude-frequency characteristic curves and the x-axis, and find the corresponding phase value in the phase difference frequency characteristic curve Δφ(ω). Record the unstable point where the phase difference is greater than 180° and the frequency point where the stable margin is low near 180° (179°-180°), which is ω u .

[0135] 2. Amplitude and phase corrector structure design

[0136] 1) Determine the connection mode of the amplitude and phase corrector

[0137] According to the actual needs of engineering construction, determine the parallel or series type of the amplitude and phase corrector. The parallel type of the amplitude and phase corrector is connected in parallel between the flexible DC converter station AC power grid and the ground, and the series type of the amplitude and phase corrector is connected in series at the outgoing side of the flexible DC converter station AC power grid.

[0138] 2) Construct a unified impedance model of the series and parallel type of the amplitude and phase corrector

[0139] If the parallel type of the amplitude and phase corrector is selected, the side without the amplitude and phase corrector of the system is a series side, and the impedance is Z s (s)=Z grid (s). If the series type of the amplitude and phase corrector is selected, the side without the amplitude and phase corrector of the system is a parallel side, and the impedance is Z p (s)=Z MMC (s), so that the elements of the circuit diagram of the parallel and series type of the amplitude and phase corrector in Figure 2 , Figure 3 are unified, as shown in Figure 4 .

[0140] 3) Determine the type of the amplitude and phase corrector

[0141] According to the actual needs of engineering construction, determine the type of the amplitude and phase corrector. If the parallel type of the amplitude and phase corrector is selected, the types that can be selected from simple to complex include single-tuned type, double-tuned type, and HP3 type, as shown in Figure 5 . If the series type of the amplitude and phase corrector is selected, the types that can be selected from simple to complex include inductance bypass type, fundamental series resonance type, and specific harmonic parallel resonance type, as shown in Figure 6 . Generally, the simpler type is selected first, and if the design result does not meet the requirements, the more complex type is selected.

[0142] 4) Given the undetermined coefficients (element parameters) of the amplitude and phase corrector and construct the transfer function of the amplitude and phase corrector

[0143] According to the selected form of the amplitude and phase corrector, construct the transfer function of the amplitude and phase corrector with undetermined coefficients Z adj (s), where for the parallel type: the basic form of the parallel type of the amplitude and phase corrector isFigure 5 as shown.

[0144] Single tuning type:

[0145]

[0146] parms={C1,L1}, C1, L1 are the capacitance, inductance values in the single tuning type amplitude and phase corrector, see attached Figure 5 ;

[0147] Double tuning type:

[0148]

[0149] parms={R1,R2,R3,L1,L2,C1,C2}, R1, R2, R3, L1, L2, C1, C2 are the resistance, inductance, capacitance values in the double tuning type amplitude and phase corrector, see attached 21 ; Figure 5 ;

[0150] In the above formula, / / symbol represents impedance parallel calculation, such as , same below.

[0151] HP3 type:

[0152]

[0153] C2 takes the value of resonance with L1 at the fundamental, i.e. C2 = 1 / (L1 ω1 2 ), ω1 is the fundamental angular frequency;

[0154] parms={R1,L1,C1}, R1, L1, C1, C2 are the resistance, inductance, capacitance values in the HP3 type amplitude and phase corrector, see attached Figure 5 ;

[0155] For series type:

[0156] Inductance bypass type:

[0157]

[0158] parms={R1,L s1}, R1, L s1 are the resistance, inductance values in the inductance bypass type amplitude and phase corrector, see attached Figure 6 ;

[0159] Fundamental series resonance type:

[0160]

[0161] C1 takes the value of resonance with L s1The value that forms resonance, i.e., C1 = 1 / (L s1 ω1 2 );

[0162] parms={R1,L s1},R1,L s1 C1 represents the resistance, inductance, and capacitance values ​​in the fundamental series resonant amplitude-phase corrector, as shown in the appendix. Figure 6 ;

[0163] Specific harmonic parallel resonance type:

[0164]

[0165] C1 is taken at the fundamental frequency and L s1 The value that forms resonance, i.e., C1 = 1 / (L s1 ω1 2 );

[0166] parms={R1,L1,L s1}, R1,L1,L s1 C1 represents the values ​​of the resistors, inductors, and capacitors in a specific harmonic parallel resonant amplitude-phase corrector, as shown in the appendix. Figure 6 .

[0167] The above Z adj In expression (s), some component parameters are treated as undetermined coefficients, denoted as parms; others are treated as given parameters, and Z is used as the set of undetermined coefficients. adj Z is considered as a function of the complex frequency domain variable s and the undetermined coefficients parms. adj (parms,s). For a fundamental series resonant type, the component parameters include R1, L... s1 C1, where parms={R1,L s1 C1 is taken at the fundamental frequency and L s1 The numerical value that forms resonance.

[0168] 5) Calculate the total impedance on the side containing the amplitude and phase corrector.

[0169] If a parallel amplitude-phase compensator is selected, the side of the system containing the amplitude-phase compensator is the parallel side, and the total impedance is Z. p (parms,s)=Z MMC (s) / / Z adj (parms,s), Z p (parms,s) is a function of the undetermined coefficients parms. If a series-type amplitude-phase compensator is selected, the side of the system containing the amplitude-phase compensator is the series side, and the total impedance is Z. s (parms,s)=Z grid (s)+Z adj (parms,s),Zs (parms,s) is a function of the to-be-determined coefficients parms.

[0170] 3. Amplitude and phase corrector parameter calculation

[0171] 1) Set multiple frequency points to be corrected and the phase correction values of each point

[0172] According to the found frequency points ω u , set multiple frequency points ω i to be corrected in the wide frequency band range containing these frequency points (i=1,2,...,n). The setting principle is that for each frequency point ω u , at least 2 frequency points to be corrected are set, and at most 10 frequency points to be corrected can be set, half of which are less than ω u , and the other half is greater than ω u . Then set the corresponding phase correction value Δφ seti (i=1,2,...,n) for each frequency point. The setting principle of the phase correction value Δφ seti is:

[0173] For a series type amplitude and phase corrector, ensure that the preset corrected target frequency characteristic function value φ target (ω i )=φ grid (ω i )-Δφ seti +Δφ m is less than 180° at each point ω i ;

[0174] For a parallel type amplitude and phase corrector, ensure that the preset corrected target frequency characteristic function value φ target (ω i )=φ MMC (ω i )-Δφ seti +Δφ m is less than 180° at each point ω i ;

[0175] Where Δφ m is the phase margin, usually set to 1°, φ grid (ω i ), φ MMC (ω i ) are the phase frequency characteristic functions of the grid side and MMC converter side impedances Z grid (s), Z MMC (s) respectively when the amplitude and phase corrector is not installed.

[0176] 2) Calculate the target phase frequency characteristic curve to be corrected

[0177] If a series type phase-amplitude corrector is selected, the series side impedance Z s (s) = Z grid (s) + Z adj (parms, ω i (i = 1, 2,..., n) of the phase value φ Zs (parms, ω i ), that is, the target phase frequency characteristic curve after the correction. φ Zs (parms, ω i ) is a function of the undetermined coefficient parms.

[0178] If a parallel type phase-amplitude corrector is selected, the parallel side impedance Z p (s) = Z MMC (s) / / Z adj (parms, ω i (i = 1, 2,..., n) of the phase value φ Zp (parms, ω i ), that is, the target phase frequency characteristic curve after the correction. φ Zp (parms, ω i ) is a function of the undetermined coefficient parms.

[0179] 3) Construct the target function of the frequency difference between the correction and the actual correction

[0180] The target function of the frequency difference between the correction and the actual correction is:

[0181] Series type:

[0182]

[0183] Parallel type:

[0184]

[0185] 4) Obtain the undetermined coefficient (element parameter) by optimizing the minimum value of the frequency difference target function

[0186] Use methods such as genetic algorithm, annealing algorithm, etc. (usually Python toolbox or call Python function library can be realized), calculate the minimum value of the target function f(parms), obtain the corresponding undetermined coefficient parms, that is, the element parameter value of the phase-amplitude corrector.

[0187] 4, phase-amplitude corrector design verification

[0188] The designed amplitude and phase corrector element parameters can meet the design requirements in the full frequency band. If the results do not meet the requirements, the initial value of the to-be-determined coefficient can be reset and the optimization algorithm is solved again until the requirements are met, or the type of the amplitude and phase corrector is changed and the element parameters are redesigned.

[0189] Specific example: taking a series fundamental series resonance type amplitude and phase corrector as an example, using the transfer function toolbox, nonlinear fitting toolbox, genetic algorithm toolbox and other tools of Python, the specific implementation of the present application is illustrated.

[0190] 1. Amplitude and phase corrector design preparation

[0191] 1) Obtain the frequency characteristic curve of the power grid

[0192] The frequency characteristics of the actual AC side power grid and the MMC converter are scanned respectively to obtain the frequency characteristic curves of the AC side power grid and the MMC converter, as shown in Figure 7 , 8 .

[0193] 2) Construct the impedance transfer functions of the AC side power grid and the converter

[0194] The frequency-response data set of the AC side power grid and the MMC converter is constructed using the frequency response toolbox "frd function" of Python, and then the nonlinear transfer function fitting tool "tfest function" is used to fit the impedance transfer function Z grid (s) of the AC side power grid and the impedance transfer function Z MMC (s) of the MMC converter using the frequency characteristic curves of the AC side power grid and the MMC converter. The obtained expressions are:

[0195]

[0196]

[0197] 3) Find the frequency point with low stability margin or instability

[0198] The difference ΔZ(s)=Z MMC (s)-Z grid (s) between the impedance transfer functions of the two sides is calculated, and the curve is shown in Figure 9 . Among them, the amplitude-frequency characteristic curve has an intersection with the x-axis, f=1007.37Hz. The phase value corresponding to the frequency point in the phase difference frequency characteristic curve Δφ(ω) is found to be 182.40°, which is greater than 180°, that is, the point of instability.

[0199] 2. Amplitude and phase corrector structure design

[0200] 1) Determine the connection mode of the amplitude and phase corrector

[0201] In this case, a series fundamental resonant amplitude-phase corrector is selected.

[0202] 2) Determine the impedance on the side without the amplitude and phase corrector.

[0203] Because a series-type amplitude and phase compensator was chosen, the side of the system without the amplitude and phase compensator is the parallel side, with an impedance of Z. p (s)=Z MMC (s).

[0204] 3) Determine the type of amplitude and phase corrector

[0205] In this case, a fundamental series resonant amplitude-phase corrector is selected.

[0206] 4) Given the undetermined coefficients (component parameters) of the amplitude-phase compensator and construct the transfer function of the amplitude-phase compensator.

[0207] The expression for the impedance transfer function of the fundamental series resonant amplitude-phase corrector is:

[0208]

[0209] 5) Calculate the total impedance on the side containing the amplitude and phase corrector.

[0210] Because a series-type amplitude and phase corrector was chosen, the side of the system containing the amplitude and phase corrector is the series side, with an impedance of Z. s (parms,s)=Z grid (s)+Z adj (parms,s). Z s (parms,s), Z adj (parms,s) is a function of the undetermined coefficients parms, where parms = {R1,L} s1 C1 is taken at the fundamental frequency and L s1 The numerical value that forms resonance.

[0211] 3. Amplitude and phase corrector parameter calculation

[0212] 1) Set the multiple frequency points that need to be corrected and the phase correction value for each point.

[0213] Set 4 frequency points ω that need to be corrected. i (i=1,2,3,4)={500Hz,1000Hz,1500Hz,2000Hz}, the range includes the unstable frequency point of 1007.37Hz and the common frequency range where broadband resonance occurs. The phase margin is set to φ. m =1°, therefore, the corresponding phase correction value Δφ can be set for each frequency point. seti (i=1,2,3,4)={5°,10°,5°,5°}, fromFigure 9 It can be seen that the setting can ensure that the preset corrected frequency characteristic curve φ target (parms,ω i )=φ grid (parms,ω i )-Δφ seti +Δφ m , each of which is less than 180° at each point ω i .

[0214] 2) Calculate the target phase frequency characteristic curve of the quasi-corrected

[0215] Because the selected is a series type amplitude and phase corrector, the series side impedance Z s (parms,s)=Z grid (s)+Z adj (parms,s) with undetermined coefficients is calculated.

[0216] 3) Construct the target function of the quasi-corrected and actual corrected frequency difference

[0217] The target function of the quasi-corrected and actual corrected frequency difference is:

[0218]

[0219] In Python, this transfer function is constructed in the form of a self-built function.

[0220] 4) Obtain the undetermined coefficients (element parameters) by optimizing the minimum value of the frequency difference target function

[0221] The "ga tool" of the Python genetic algorithm toolbox is used to calculate the minimum value of the target function f(parms), and the corresponding undetermined coefficients parms={14.619, 3.689} are obtained, i.e. R1=14.619Ω, L s1 =3.689H, and the non-undetermined coefficient C1=2.747μF is calculated according to the resonance relationship of L s1 and C1 at the fundamental frequency 50Hz.

[0222] 4, amplitude and phase corrector design verification

[0223] The calculated amplitude and phase corrector element parameters are brought in, and the amplitude and phase frequency characteristic curves of the corrected series impedance Z s and the parallel impedance Z p are calculated, such as Figure 10As shown. It can be seen that after correction, at the frequency point f = 1008.5 Hz where the phase difference of the amplitude is 0, the phase difference is Δφ (ω) = 178.35°, which is less than 180° and the margin is greater than the set 1°, thus meeting the design requirements. If a greater margin is required, the phase correction value Δφ seti or the parameter value range of the genetic algorithm.

[0224] The first aspect of the present application provides a design device of a flexible DC wide frequency oscillation suppression amplitude-phase corrector, comprising:

[0225] A curve acquisition module is configured to acquire a power grid frequency characteristic curve.

[0226] A transfer function construction module is configured to construct an AC power grid side impedance transfer function and a converter side impedance transfer function according to the power grid frequency characteristic curve.

[0227] A critical region frequency point determination module is configured to determine frequency points with low stability margin or instability according to the AC power grid side impedance transfer function and the converter side impedance transfer function.

[0228] A total impedance function construction module is configured to determine undetermined coefficients parms in amplitude-phase corrector element parameters and construct an amplitude-phase corrector transfer function with the undetermined coefficients according to the type of the required amplitude-phase corrector, and further obtain a total impedance function containing the amplitude-phase corrector side.

[0229] A required correction frequency point setting module is configured to set a plurality of required correction frequency points according to the frequency points with low stability margin or instability.

[0230] An actual correction target phase frequency characteristic curve setting module is configured to preset an actual correction target phase frequency characteristic curve and set corresponding phase correction values for each required correction frequency point to ensure that the target phase at each required correction frequency point on the actual correction target phase frequency characteristic curve is less than 180°.

[0231] A target phase frequency characteristic curve construction module is configured to calculate the phase value of the total impedance function at the required correction frequency point to obtain a target phase frequency characteristic curve after correction.

[0232] A frequency difference target function construction module is configured to construct a frequency difference target function according to the target phase frequency characteristic curve after correction and the actual correction target amplitude-phase frequency characteristic curve.

[0233] An element parameter value calculation module is configured to calculate the minimum value of the frequency difference target function and obtain the corresponding undetermined coefficients, i.e., the element parameter value of the amplitude-phase corrector.

[0234] The curve acquisition module is specifically configured to:

[0235] respectively, to obtain the amplitude-phase frequency characteristic curves A grid (ω0), φ grid (ω0), A MMC (ω0), φ MMC (ω0) in the frequency range of 50Hz to 5000Hz; wherein ω0 is a frequency point of the frequency characteristic curve, A grid (ω0), φ grid (ω0) is an amplitude-phase frequency characteristic curve of the grid side, A MMC (ω0), φ MMC (ω0) is an amplitude-phase frequency characteristic curve of the MMC converter side, both in the form of point sets of (angular frequency, amplitude) and (angular frequency, phase).

[0236] The transfer function construction module is specifically configured to:

[0237] using a nonlinear transfer function fitting method, using the amplitude-phase frequency characteristic curves A grid (ω0), φ grid (ω0), A MMC (ω0), φ MMC (ω0) of the AC grid side and the MMC converter side to respectively fit the AC grid side impedance transfer function Z grid (s) and the converter side impedance transfer function Z MMC (s).

[0238] The critical region frequency point determination module is specifically configured to:

[0239] find the difference ΔZ(s)=Z MMC (s)-Z grid (s), record the frequencies f of all intersection points of the amplitude-frequency characteristic curves of the two impedance transfer functions and the x-axis, f=ω / 2π, and find the corresponding phase values in the phase difference frequency characteristic curve Δφ(ω), record the unstable frequency points with a phase difference greater than 180° and the frequency points with a low stability margin with a phase difference of 179°-180°, and unify them as unstable or low stability margin frequency points ω u .

[0240] The total impedance function construction module is specifically configured to:

[0241] determine the type of the amplitude-phase corrector to be parallel or series according to the actual needs of engineering construction;

[0242] select the form of the amplitude-phase corrector according to the determined type of the amplitude-phase corrector, and construct the amplitude-phase corrector transfer function Zadj (s) ; the amplitude-phase corrector transfer function Z adj (s) is expressed as a set of undetermined coefficients, denoted as parms, and Z adj (s) is regarded as a function of both the complex frequency variable s and the undetermined coefficients parms, denoted as Z adj (parms, s) ;

[0243] If the amplitude-phase corrector is of the shunt type, the total impedance function Z s (parms, s) = Z grid (s) + Z adj (parms, s) ; if the amplitude-phase corrector is of the series type, the total impedance function Z p (parms, s) = Z MMC (s) / / Z adj (parms, s).

[0244] The setting of the frequency points to be corrected module is specifically configured to:

[0245] According to the found frequency points ω u , a plurality of frequency points ω i (i = 1, 2,..., n) are set in a wide frequency band range containing these frequency points; the setting principle of the frequency points to be corrected is that, for each frequency point ω u , 2N frequency points ω i , 1≤N≤5, are set, where N frequency points have a frequency less than ω u , and N frequency points have a frequency greater than ω u .

[0246] The actual corrected target phase frequency characteristic curve is specifically:

[0247] For the series type amplitude-phase corrector, the actual corrected target phase frequency characteristic curve φ target (ω i ) = φ grid (ω i ) - Δφ seti + Δφ m .

[0248] For the shunt type amplitude-phase corrector, the actual corrected target phase frequency characteristic curve φ target (ω i ) = φ MMC (ω i ) - Δφ seti + Δφ m .

[0249] Where, Δφ seti The phase correction value is Δφ. m For phase margin, φ grid (ω i ), φ MMC (ω i The impedances Z on the grid side and MMC converter side are respectively the impedances without the amplitude and phase corrector installed. grid (s), Z MMC The phase-frequency characteristic function of (s).

[0250] The module for constructing the target phase frequency response curve to be corrected is specifically used for:

[0251] For a series-type amplitude-phase corrector, calculate the series-side impedance Z with undetermined coefficients. s (parms,s)=Z grid (s)+Z adj (parms,s) at the aforementioned frequency point ω that needs correction i The phase value φ at (i=1,2,...,n) Zs (parms,ω i ), φ Zs (parms,ω i That is, the target phase-frequency response curve after the correction;

[0252] For a parallel-type amplitude-phase corrector, calculate the parallel-side impedance Z with undetermined coefficients. p (parms,s)=Z MMC (s) / / Z adj (parms,s) at the aforementioned frequency point ω that needs correction i The phase value φ at (i=1,2,...,n) Zp (parms,ω i ), φ Zp (parms,ω i That is, the target phase frequency response curve after the correction.

[0253] The specific objective function for the frequency difference is:

[0254] For a series-type amplitude-phase corrector, the objective function for frequency difference is:

[0255]

[0256] For a parallel amplitude-phase compensator, the objective function for frequency difference is:

[0257] .

[0258] The component parameter value acquisition module is specifically used to: calculate the frequency difference objective function through an optimization algorithm. the minimum value of the function to obtain the element parameter value.

[0259] Another aspect of the present application provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable in the processor, wherein the processor implements the design method of the amplitude-phase corrector for flexible DC wide frequency oscillation suppression when executing the computer program.

[0260] Another aspect of the present application provides a non-transitory computer readable storage medium, which stores a computer program, wherein the computer program is executable in a processor to implement the design method of the amplitude-phase corrector for flexible DC wide frequency oscillation suppression.

[0261] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) containing computer-usable program code.

[0262] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus generate a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus for implementing the functions specified in the flowcharts and / or block diagrams.

[0263] These computer program instructions can also be stored in a computer-readable memory that can direct the computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including instruction apparatus, which implements the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 an apparatus for implementing the functions specified in the flowcharts and / or block diagrams.

[0264] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0265] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A design method for a flexible DC broadband oscillation suppression amplitude and phase corrector, characterized in that: include: Obtain the power grid frequency response curve; Based on the power grid frequency characteristic curve, construct the AC power grid-side impedance transfer function and the converter-side impedance transfer function. Based on the AC grid-side impedance transfer function and the converter-side impedance transfer function, determine the frequency points that are unstable or have low stability margin. Based on the type of amplitude-phase corrector required, determine the undetermined coefficients parms in the amplitude-phase corrector component parameters and construct the amplitude-phase corrector transfer function with the undetermined coefficients, thereby obtaining the total impedance function on the side containing the amplitude-phase corrector. Based on the unstable or low stability margin frequency points, multiple frequency points that need to be corrected are set; A target phase frequency response curve after actual correction is preset, and corresponding phase correction values ​​are set for each frequency point that needs to be corrected to ensure that the target phase at each frequency point that needs to be corrected on the target phase frequency response curve after actual correction is less than 180°. Calculate the phase value of the total impedance function at the frequency to be corrected to obtain the target phase frequency response curve after correction; Based on the target phase frequency response curve to be corrected and the target amplitude-phase frequency response curve to be actually corrected, construct the frequency difference objective function; Calculate the minimum value of the frequency difference objective function, find the corresponding undetermined coefficients, and thus obtain the component parameter values ​​of the amplitude-phase corrector.

2. The design method of the amplitude and phase corrector for flexible DC broadband oscillation suppression according to claim 1, characterized in that: The acquisition of the power grid frequency characteristic curve is specifically as follows: Frequency scans were performed on both the actual and simulated AC power grid and the MMC converter to obtain the amplitude-phase frequency response curves A of the AC power grid side and the MMC converter side. grid (ω0), φ grid (ω0), A MMC (ω0), φ MMC (ω0), with a frequency range of 50Hz to 5000Hz; where ω0 is the frequency point of the frequency response curve, A grid (ω0), φ grid (ω0) is the amplitude and phase frequency response curve on the grid side, A MMC (ω0), φ MMC (ω0) represents the amplitude and phase frequency response curves on the MMC converter side, which are stored in the form of point sets of (angular frequency, amplitude) and (angular frequency, phase).

3. The design method of the amplitude and phase corrector for flexible DC broadband oscillation suppression according to claim 2, characterized in that: The construction of the AC grid-side impedance transfer function and the converter-side impedance transfer function based on the grid frequency characteristic curve is as follows: A nonlinear transfer function fitting method is used, utilizing the amplitude-phase-frequency characteristic curves A of the AC-side power grid and the MMC converter side. grid (ω0), φ grid (ω0), A MMC (ω0), φ MMC (ω0), respectively fitting the AC grid side impedance transfer function Z grid (s), Converter-side impedance transfer function Z MMC (s).

4. The design method of the amplitude and phase corrector for flexible DC broadband oscillation suppression according to claim 3, characterized in that: The step of determining the unstable or low-stability-margin frequency points based on the AC grid-side impedance transfer function and the converter-side impedance transfer function specifically involves: Find the difference in impedance transfer functions on both sides, ΔZ(s) = Z. MMC (s)-Z grid (s), record the frequencies f of all intersection points between the amplitude-frequency response curves and the x-axis, f = ω / 2π, and find the corresponding phase values ​​in the phase difference frequency response curve Δφ(ω). Record the unstable frequency points with a phase difference greater than 180° and the frequency points with a low stability margin with a phase difference of 179°-180°, and uniformly record them as unstable or low stability margin frequency points ω. u .

5. The design method of the amplitude and phase corrector for flexible DC broadband oscillation suppression according to claim 4, characterized in that: Based on the required type of amplitude-phase corrector, the undetermined coefficients in the amplitude-phase corrector element parameters are determined, and the amplitude-phase corrector transfer function with the undetermined coefficients is constructed, thereby obtaining the total impedance function on the side containing the amplitude-phase corrector, specifically: Based on the actual needs of the project construction, the type of amplitude and phase corrector is determined to be either parallel or series. Based on the determined amplitude-phase compensator type, the form of the amplitude-phase compensator is selected, and the transfer function Z of the amplitude-phase compensator with undetermined coefficients is constructed. adj (s); the transfer function Z of the amplitude and phase corrector adj The resistance, capacitance, and inductance parameters in expression (s) are treated as undetermined coefficients, and their set is denoted as parms; and Z is... adj Z is considered as a function of the complex frequency domain variable s and the undetermined coefficients parms. adj (parms,s); If the amplitude and phase compensator type is parallel, then the total impedance function Z on the side containing the amplitude and phase compensator is... s (parms,s)=Z grid (s)+Z adj (parms,s); If the amplitude-phase compensator is of series type, then the total impedance function Z on the side containing the amplitude-phase compensator is... p (parms,s)=Z MMC (s) / / Z adj (parms,s).

6. The design method of the amplitude and phase corrector for flexible DC broadband oscillation suppression according to claim 5, characterized in that: Based on the determined amplitude-phase corrector type, the form of the amplitude-phase corrector is selected, and the amplitude-phase corrector transfer function Z with undetermined coefficients is constructed. adj (s), the amplitude-phase corrector transfer function Z adj The resistance, capacitance and inductance parameters in the expression (s) are taken as undetermined coefficients, and their set is denoted as parms; Specifically, it includes: The amplitude and phase corrector type is selected based on the principle of first choosing a simple form and then choosing a complex form if the design results do not meet the requirements. If the determined amplitude and phase corrector type is parallel, the types of amplitude and phase correctors that can be selected from simple to complex are single-tuned type, double-tuned type, and HP3 type. If the determined amplitude and phase corrector type is series, the types of amplitude and phase correctors that can be selected from simple to complex are inductor bypass type, fundamental frequency series resonant type, and specific harmonic parallel resonant type. If the amplitude-phase corrector is a single-tuned type, then the transfer function Z of the amplitude-phase corrector is... adj (s) is: ； parms={C1,L1}, ​​where C1 and L1 are the capacitance and inductance values ​​in a single-tuned amplitude-phase corrector; If the amplitude-phase corrector is a double-tuned type, then the amplitude-phase corrector transfer function Z adj (s) is: ； parms={R1,R2,R3,L1,L2,C1,C2},R1,R2,R3,L1,L2,C1,C 21 These are the values ​​of the resistors, inductors, and capacitors in the dual-tuned amplitude-phase corrector; Where the / / symbol represents impedance parallel calculation; If the amplitude-phase corrector is of type HP3, then the amplitude-phase corrector transfer function Z adj (s) is: ； C2 is taken as the value that resonates with L1 at the fundamental frequency, i.e., C2 = 1 / (L1ω1) 2 ), where ω1 is the fundamental angular frequency; parms={R1,L1,C1}, where R1,L1,C1,C2 are the values ​​of the resistors, inductors, and capacitors in the HP3 type amplitude and phase corrector; If the amplitude-phase compensator is of the inductor bypass type, then the transfer function Z of the amplitude-phase compensator is... adj (s) is: ； parms={R1,L s1 },R1,L s1 These are the resistance and inductance values ​​in an inductor-bypass type amplitude-phase corrector. If the amplitude-phase compensator is of the fundamental series resonant type, then the transfer function Z of the amplitude-phase compensator is... adj (s) is: ； C1 is taken at the fundamental frequency and L s1 The value that forms resonance, i.e., C1 = 1 / (L s1 ω1 2 ); parms={R1,L s1 },R1,L s1 C1 represents the resistance, inductance, and capacitance values ​​in the fundamental series resonant amplitude-phase corrector. If the amplitude-phase compensator is of the specific harmonic parallel resonant type, then the transfer function Z of the amplitude-phase compensator is... adj (s) is: ； C1 is taken at the fundamental frequency and L s1 The value that forms resonance, i.e., C1 = 1 / (L s1 ω1 2 ); parms={R1,L1,L s1 }, R1,L1,L s1 C1 represents the values ​​of resistors, inductors, and capacitors in a specific harmonic parallel resonant amplitude-phase corrector.

7. The design method of the amplitude and phase corrector for flexible DC broadband oscillation suppression according to claim 6, characterized in that: The step of setting multiple frequency points requiring correction based on the unstable or low stability margin frequency points is as follows: Based on the frequency point ω that is found to be unstable or has a low stability margin u Within a wide frequency band encompassing these frequency points, multiple frequency points ω to be corrected are set. i (i=1,2,...,n); The principle for setting the frequency points to be corrected is that for each frequency point ω u Set 2N frequency points ω that need to be corrected. i 1≤N≤5, where N frequency points have frequencies less than ω. u N frequency points with frequencies greater than ω u .

8. The design method of the amplitude and phase corrector for flexible DC broadband oscillation suppression according to claim 7, characterized in that: The actual corrected target phase frequency response curve is as follows: For a series-type amplitude-phase compensator, the actual corrected target phase frequency response curve φ target (ω i )=φ grid (ω i )-Δφ seti +Δφ m ; For a parallel amplitude-phase compensator, the actual corrected target phase frequency response curve φ target (ω i )=φ MMC (ω i )-Δφ seti +Δφ m ; Where, Δφ seti The phase correction value is Δφ. m For phase margin, φ grid (ω i ), φ MMC (ω i The impedances Z on the grid side and MMC converter side are respectively the impedances without the amplitude and phase corrector installed. grid (s), Z MMC The phase-frequency characteristic function of (s).

9. The design method of the amplitude and phase corrector for flexible DC broadband oscillation suppression according to claim 7, characterized in that: The calculation of the phase value of the total impedance function at the frequency point to be corrected, to obtain the target phase-frequency response curve after correction, specifically includes: For a series-type amplitude-phase corrector, calculate the series-side impedance Z with undetermined coefficients. s (parms,s)=Z grid (s)+Z adj (parms,s) at the aforementioned frequency point ω that needs correction i The phase value φ at (i=1,2,...,n) Zs (parms,ω i ), φ Zs (parms,ω i That is, the target phase-frequency response curve after the correction; For a parallel-type amplitude-phase corrector, calculate the parallel-side impedance Z with undetermined coefficients. p (parms,s)=Z MMC (s) / / Z adj (parms,s) at the aforementioned frequency point ω that needs correction i The phase value φ at (i=1,2,...,n) Zp (parms,ω i ), φ Zp (parms,ω i That is, the target phase frequency response curve after the correction.

10. The design method of the amplitude and phase corrector for flexible DC broadband oscillation suppression according to claim 9, characterized in that: The specific objective function for the frequency difference is: For a series-type amplitude-phase corrector, the objective function for frequency difference is: ； For a parallel amplitude-phase compensator, the objective function for frequency difference is: 。 11. The design method of the amplitude and phase corrector for flexible DC broadband oscillation suppression according to claim 10, characterized in that: The process of calculating the minimum value of the frequency difference objective function and determining the corresponding undetermined coefficients, thereby obtaining the component parameter values ​​of the amplitude-phase corrector, specifically involves: calculating the frequency difference objective function using an optimization algorithm. Find the minimum value of and determine the corresponding undetermined coefficients. The component parameter values ​​are obtained; the optimization algorithm is a genetic algorithm or an annealing algorithm.

12. A design device for a flexible DC broadband oscillation suppression amplitude and phase corrector, characterized in that: include: The curve acquisition module is used to acquire the power grid frequency characteristic curve; The transfer function construction module is used to construct the AC grid-side impedance transfer function and the converter-side impedance transfer function based on the grid frequency characteristic curve. The critical region frequency point determination module is used to determine the unstable or low stability margin frequency points based on the AC grid-side impedance transfer function and the converter-side impedance transfer function. The total impedance function construction module is used to determine the undetermined coefficients parms in the parameters of the amplitude and phase corrector components according to the type of required amplitude and phase corrector, and construct the transfer function of the amplitude and phase corrector with the undetermined coefficients, thereby obtaining the total impedance function on the side containing the amplitude and phase corrector. The frequency point setting module is used to set multiple frequency points to be calibrated based on the unstable or low stability margin frequency points. The actual corrected target phase frequency response curve setting module is used to preset an actual corrected target phase frequency response curve and set corresponding phase correction values ​​for each frequency point to be corrected to ensure that the target phase at each frequency point to be corrected on the actual corrected target phase frequency response curve is less than 180°. The module for constructing the target phase frequency response curve after correction is used to calculate the phase value of the total impedance function at the frequency point to be corrected, and to obtain the target phase frequency response curve after correction. The frequency difference objective function construction module is used to construct the frequency difference objective function based on the target phase frequency characteristic curve to be corrected and the target amplitude and phase frequency characteristic curve to be actually corrected. The component parameter value acquisition module calculates the minimum value of the frequency difference objective function and obtains the corresponding undetermined coefficients, thus obtaining the component parameter values ​​of the amplitude-phase corrector.

13. The design device for a flexible DC broadband oscillation suppression amplitude and phase corrector according to claim 12, characterized in that: The curve acquisition module is specifically used for: Frequency scans were performed on both the actual and simulated AC power grid and the MMC converter to obtain the amplitude-phase frequency response curves A of the AC power grid side and the MMC converter side. grid (ω0), φ grid (ω0), A MMC (ω0), φ MMC (ω0), with a frequency range of 50Hz to 5000Hz; where ω0 is the frequency point of the frequency response curve, A grid (ω0), φ grid (ω0) is the amplitude and phase frequency response curve on the grid side, A MMC (ω0), φ MMC (ω0) represents the amplitude and phase frequency response curves on the MMC converter side, which are stored in the form of point sets of (angular frequency, amplitude) and (angular frequency, phase).

14. The design apparatus for a flexible DC broadband oscillation suppression amplitude and phase corrector according to claim 13, characterized in that: The transfer function construction module is specifically used for: A nonlinear transfer function fitting method is used, utilizing the amplitude-phase-frequency characteristic curves A of the AC-side power grid and the MMC converter side. grid (ω0), φ grid (ω0), A MMC (ω0), φ MMC (ω0), respectively fitting the AC grid side impedance transfer function Z grid (s), Converter-side impedance transfer function Z MMC (s).

15. The design apparatus for a flexible DC broadband oscillation suppression amplitude and phase corrector according to claim 14, characterized in that: The critical region frequency point determination module is specifically used for: Find the difference in impedance transfer functions on both sides, ΔZ(s) = Z. MMC (s)-Z grid (s), record the frequencies f of all intersection points between the amplitude-frequency response curves and the x-axis, f = ω / 2π, and find the corresponding phase values ​​in the phase difference frequency response curve Δφ(ω). Record the unstable frequency points with a phase difference greater than 180° and the frequency points with a low stability margin with a phase difference of 179°-180°, and uniformly record them as unstable or low stability margin frequency points ω. u .

16. The design apparatus for a flexible DC broadband oscillation suppression amplitude and phase corrector according to claim 15, characterized in that: The total impedance function construction module is specifically used for: Based on the actual needs of the project construction, the type of amplitude and phase corrector is determined to be either parallel or series. Based on the determined amplitude-phase compensator type, the form of the amplitude-phase compensator is selected, and the transfer function Z of the amplitude-phase compensator with undetermined coefficients is constructed. adj (s); the transfer function Z of the amplitude and phase corrector adj The resistance, capacitance, and inductance parameters in expression (s) are treated as undetermined coefficients, and their set is denoted as parms; and Z is... adj Z is considered as a function of the complex frequency domain variable s and the undetermined coefficients parms. adj (parms,s); If the amplitude and phase compensator type is parallel, then the total impedance function Z on the side containing the amplitude and phase compensator is... s (parms,s)=Z grid (s)+Z adj (parms,s); If the amplitude-phase compensator is of series type, then the total impedance function Z on the side containing the amplitude-phase compensator is... p (parms,s)=Z MMC (s) / / Z adj (parms,s).

17. The design apparatus for a flexible DC broadband oscillation suppression amplitude and phase corrector according to claim 16, characterized in that: The frequency point setting module that needs to be corrected is specifically used for: Based on the frequency point ω that is found to be unstable or has a low stability margin u Within a wide frequency band encompassing these frequency points, multiple frequency points ω to be corrected are set. i (i=1,2,...,n); The principle for setting the frequency points to be corrected is that for each frequency point ω u Set 2N frequency points ω that need to be corrected. i 1≤N≤5, where N frequency points have frequencies less than ω. u N frequency points with frequencies greater than ω u .

18. The design apparatus for a flexible DC broadband oscillation suppression amplitude and phase corrector according to claim 17, characterized in that: The actual corrected target phase frequency response curve is as follows: For a series-type amplitude-phase compensator, the actual corrected target phase frequency response curve φ target (ω i )=φ grid (ω i )-Δφ seti +Δφ m ; For a parallel amplitude-phase compensator, the actual corrected target phase frequency response curve φ target (ω i )=φ MMC (ω i )-Δφ seti +Δφ m ; Where, Δφ seti The phase correction value is Δφ. m For phase margin, φ grid (ω i ), φ MMC (ω i The impedances Z on the grid side and MMC converter side are respectively the impedances without the amplitude and phase corrector installed. grid (s), Z MMC The phase-frequency characteristic function of (s).

19. The design apparatus for a flexible DC broadband oscillation suppression amplitude and phase corrector according to claim 18, characterized in that: The module for constructing the target phase frequency response curve to be corrected is specifically used for: For a series-type amplitude-phase corrector, calculate the series-side impedance Z with undetermined coefficients. s (parms,s)=Z grid (s)+Z adj (parms,s) at the aforementioned frequency point ω that needs correction i The phase value φ at (i=1,2,...,n) Zs (parms,ω i ), φ Zs (parms,ω i That is, the target phase-frequency response curve after the correction; For a parallel-type amplitude-phase corrector, calculate the parallel-side impedance Z with undetermined coefficients. p (parms,s)=Z MMC (s) / / Z adj (parms,s) at the aforementioned frequency point ω that needs correction i The phase value φ at (i=1,2,...,n) Zp (parms,ω i ), φ Zp (parms,ω i That is, the target phase frequency response curve after the correction.

20. The design apparatus for a flexible DC broadband oscillation suppression amplitude and phase corrector according to claim 19, characterized in that: The specific objective function for the frequency difference is: For a series-type amplitude-phase corrector, the objective function for frequency difference is: ； For a parallel amplitude-phase compensator, the objective function for frequency difference is: 。 21. The design device for a flexible DC broadband oscillation suppression amplitude and phase corrector according to claim 20, characterized in that: The component parameter value acquisition module is specifically used to: calculate the frequency difference objective function through an optimization algorithm. Find the minimum value of and determine the corresponding undetermined coefficients. This yields the component parameter values.

22. An electronic device, characterized in that: It includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the design method of the amplitude and phase corrector for the flexible DC broadband oscillation suppression as described in any one of claims 1-11.

23. A non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the design method of a flexible DC broadband oscillation suppressor amplitude and phase corrector as described in any one of claims 1-11.

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