CN105515021A - Multi-mode additional sub/super synchronous oscillation control method and control system - Google Patents

Abstract

The invention discloses a multi-mode additional sub/super synchronous oscillation control method and control system. The method comprises the following steps: collecting total three phase current ic at a fan side or total three phase current iL at a circuit side; according to the total three phase current ic at the fan side or the total three phase current iL at the circuit side, calculating to obtain multiple mode control signals; performing addition operation on the multiple mode control signals, so as to obtain an additional control signal; performing amplitude limiting processing on the additional control signal, so that the amplitude value of the additional control signal is located in a first preset range. The method can effectively inhibit sub/super synchronous oscillation of a system when a wind power plant is connected.

Description

Multi-mode additional subsynchronous/supersynchronous oscillation control method and control system

Technical Field

The invention relates to the technical field of power system control, in particular to a multi-mode additional subsynchronous/supersynchronous oscillation control method and a control system.

Background

Wind energy is a clean and sustainable energy which is widely distributed, and wind power generation in China is continuously and rapidly developed. Considering the reverse distribution of resources and load centers in China, large-scale wind power long-distance delivery becomes a necessary trend. When the wind power plant sends power out through a power transmission line with a series compensation capacitor, secondary/super-synchronous resonance or oscillation which mainly takes an induction generator effect may occur, and the safe and stable operation of a power system is influenced.

Disclosure of Invention

The present invention is directed to solving at least one of the above problems.

Therefore, the invention aims to provide a multi-mode additional subsynchronous/supersynchronous oscillation control method which can effectively inhibit subsynchronous/supersynchronous oscillation of a system when a wind power plant is accessed.

It is another object of the present invention to provide a multi-mode additional sub/super-synchronous oscillation control system.

In order to achieve the above object, an embodiment of the first aspect of the present invention discloses a multi-mode additional sub/super-synchronous oscillation control method, including the following steps: s1: collecting total three-phase current i of fan side_cOr total three-phase current i on the line side_L(ii) a S2: according to the total three-phase current i of the fan side_cOr total three-phase current i on the line side_LCalculating to obtain a plurality of mode control signals; s3: summing the plurality of mode control signals to obtain an additional control signal; and S4: and carrying out amplitude limiting processing on the additional control signal so that the amplitude of the additional control signal is within a first preset range.

According to the multi-mode additional subsynchronous/supersynchronous oscillation control method provided by the embodiment of the invention, the total current of the side of the wind turbine or the side of the line is collected in real time, the additional control signal is calculated, and the static var generator is controlled to be equivalent to the inductive impedance connected in parallel with the bus at the subsynchronous/supersynchronous frequency of the oscillation, so that the oscillation generation condition of the system is damaged, and the subsynchronous/supersynchronous oscillation of the system when the wind power plant is accessed is effectively inhibited.

In addition, the multi-mode additional sub/super synchronous oscillation control method according to the above embodiment of the present invention may further have the following additional technical features:

further, the S2 further includes: s21: to total three-phase current i of the fan side_cOr the total three-phase current i of the line side_LFiltering to filter out subsynchronous and supersynchronous harmonic components; s22: compensating for phase delays generated by the measurement, filter and said static var generator, and/or performing predetermined phase offset and amplitude compensation; s23: converting the phase compensated and/or offset current signal into a three-phase reference current I of a static var generator_SVG,abc,kThe method specifically comprises the following steps:

when the collected signal is the total three-phase current i of the fan side_cWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{I_{c,abc,k}\left(s\right)}{1+\frac{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{R_L+{\mathrm{sL}}_L}},$

when the collected signal is the total three-phase current i at the line side_LWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{R_L+{\mathrm{sL}}_L}{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{I}_{L,abc,k}\left(s\right),$

wherein, I_L,abc,k(s) and I_c,abc,k(s) represents the three-phase current of a, b, c on the line side and the fan side after the signal processing in the mode k, k is 1, …, N, N is the total number of the controlled modes, I_SVG,abc,k(s) a, b, c three-phase values, R, of the three-phase reference currents of the SVG calculated in mode k_L、L_LRespectively representing the equivalent resistance and inductance, R, of the line side_SVG,k、L_SVG,kThe additional equivalent resistance and the inductance of the static var generator which can be set in the mode k are respectively expressed as control parameters; s24: according to the three-phase reference current I of the static var generator_SVG,abc,kCalculating a plurality of mode control signals sent to the static var generator according to the reference values received by the static var generator; s25: performing clipping processing on the plurality of mode control signals toAnd enabling the amplitudes of the plurality of mode control signals to be within a second preset range.

Further, the S21 further includes: obtaining the subsynchronous harmonic component and the supersynchronous harmonic component through a band-pass filter; and/or filtering out the total three-phase current i of the fan side by connecting a band-pass filter with a band-stop filter or a low-pass/high-pass filter in series_cOr the total three-phase current i of the line side_LAnd obtaining the subsynchronous and supersynchronous harmonic components.

Further, step S24 further includes: when the reference value received by the static var generator is a current,

${\mathrm{\ΔI}}_{SVG,abc,k}^{*}\left(s\right)=I_{SVG,abc,k}\left(s\right),$

wherein,an additional mode current control signal corresponding to mode k for the static var generator;

when the reference value received by the static var generator is the access bus voltage,

${\mathrm{\ΔV}}_{abc,k}^{*}\left(s\right)=-I_{SVG,abc,k}\left(s\right)*(R_L+{\mathrm{sL}}_L),$

wherein,an additional mode voltage control signal corresponding to mode k for the static var generator;

when the reference value received by the static var generator is reactive power,

${\mathrm{\Δq}}_k^{*}=I_{SVG,abc,k}*V_{abc},$

wherein,additional instantaneous reactive power mode control signal, V, corresponding to mode k for the SVG_abcAnd representing the fundamental components of the three-phase voltage of the access bus of the static var generator.

Further, in the S3, the additional control signal is obtained by directly adding the plurality of mode control signals; or

Setting weights of a plurality of mode control signals, and adding the plurality of mode control signals according to a weight proportion to obtain the additional control signal, specifically comprising:

$X=\underset{k=1}{\overset{N}{\Σ}}{w}_k{X}_k,$

wherein, w_kFor the weighting factors, w is added directly_k＝1，X_kIs the mode control signal corresponding to mode k, X is the additional control signal and N is the total number of modes.

In order to achieve the above object, an embodiment of a second aspect of the present invention discloses a multi-mode additional sub/super-synchronous oscillation control system, comprising: the signal acquisition and conversion module is used for acquiring the total three-phase current i of the side of the fan in real time_cOr total three-phase current i on the line side_LAnd converted into corresponding digital signals; an additional control module for determining a total three-phase current i of the wind turbine side_cOr total three-phase current i on the line side_LCalculating to obtain a plurality of mode control signals; a mode control signal summing module for summing the plurality of mode control signals to obtain additional controlA signal; and the additional control signal amplitude limiting module is used for carrying out amplitude limiting processing on the additional control signal so as to enable the amplitude of the additional control signal to be within a first preset range.

According to the multi-mode additional subsynchronous/supersynchronous oscillation control system provided by the embodiment of the invention, the total three-phase current of the side of a fan or the side of a line is collected in real time, an additional control signal is calculated, and the static var generator is controlled to be equivalent to inductive impedance connected in parallel with a bus at the subsynchronous/supersynchronous frequency of oscillation, so that the oscillation generation condition of the system is damaged, and the subsynchronous/supersynchronous oscillation of the system when a wind power plant is accessed is effectively inhibited.

In addition, the multi-mode additional sub/super synchronous oscillation control system according to the above embodiment of the present invention may further have the following additional technical features:

further, the additional control module includes: a filtering module for filtering a total three-phase current i of the fan side_cOr the total three-phase current i of the line side_LFiltering to filter out subsynchronous and supersynchronous harmonic components; a proportional/phase shift module for compensating for phase delays generated by the measurement, filter and the static var generator, and/or for performing predetermined phase offset and amplitude compensation; a reference current calculation module for converting the phase compensated and/or offset current signal into a three-phase reference current I of the SVG_SVG,abc,kThe method specifically comprises the following steps:

when the collected signal is the total three-phase current i of the fan side_cWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{I_{c,abc,k}\left(s\right)}{1+\frac{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{R_L+{\mathrm{sL}}_L}},$

when the collected signal is the total three-phase current i at the line side_LWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{R_L+{\mathrm{sL}}_L}{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{I}_{L,abc,k}\left(s\right),$

wherein, I_L,abc,k(s) and I_c,abc,k(s) represents the three-phase current of a, b, c on the line side and the fan side after the signal processing in the mode k, k is 1, …, N, N is the total number of the controlled modes, I_SVG,abc,k(s) a, b, c three-phase values, R, of the three-phase reference currents of the SVG calculated in mode k_L、L_LRespectively representing the equivalent resistance and inductance, R, of the line side_SVG,k、L_SVG,kThe additional equivalent resistance and the inductance of the static var generator which can be set in the mode k are respectively expressed as control parameters; a mode control signal calculation module for calculating a three-phase reference current I of the SVG according to the three-phase reference current I_SVG,abc,kCalculating a plurality of mode control signals sent to the static var generator according to the reference values received by the static var generator; and the mode control signal amplitude limiting module is used for carrying out amplitude limiting processing on the plurality of mode control signals so as to enable the amplitudes of the plurality of mode control signals to be within a second preset range.

Further, the filtering module is usedIn the following steps: obtaining the subsynchronous harmonic component and the supersynchronous harmonic component through a band-pass filter; and/or filtering out the total three-phase current i of the fan side by connecting a band-pass filter with a band-stop filter or a low-pass/high-pass filter in series_cOr the total three-phase current i of the line side_LAnd obtaining the subsynchronous and supersynchronous harmonic components.

Further, the mode control signal calculation module is configured to: when the reference value received by the static var generator is a current,

${\mathrm{\ΔI}}_{SVG,abc,k}^{*}\left(s\right)=I_{SVG,abc,k}\left(s\right),$

wherein,an additional mode current control signal corresponding to mode k for the static var generator;

when the reference value received by the static var generator is the access bus voltage,

${\mathrm{\ΔV}}_{abc,k}^{*}\left(s\right)=-I_{SVG,abc,k}\left(s\right)*(R_L+{\mathrm{sL}}_L),$

wherein,an additional mode voltage control signal corresponding to mode k for the static var generator;

when the reference value received by the static var generator is reactive power,

${\mathrm{\Δq}}_k^{*}=I_{SVG,abc,k}*V_{abc},$

wherein,additional instantaneous reactive power mode control signal, V, corresponding to mode k for the SVG_abcPresentation instrumentAnd the static var generator is connected with the three-phase voltage fundamental component of the bus.

Further, wherein the mode control signal summing module is configured to: directly adding the plurality of mode control signals to obtain the additional control signal; or setting weights of a plurality of mode control signals, and adding the plurality of mode control signals according to a weight proportion to obtain the additional control signal, specifically comprising:

$X=\underset{k=1}{\overset{N}{\Σ}}{w}_k{X}_k,$

wherein, w_kFor the weighting factors, w is added directly_k＝1，X_kIs the mode control signal corresponding to mode k, X is the additional control signal and N is the total number of modes.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a flow chart of a multi-mode additional sub/super-synchronous oscillation control method according to one embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating the operation of the multi-mode additional sub/super-synchronous oscillation control method according to an embodiment of the present invention;

FIG. 3 is a schematic overall flow diagram of a multi-mode additional sub/super-synchronous oscillation control method according to one embodiment of the present invention;

FIG. 4 is a block diagram illustrating the structure of a multi-mode additional sub/super-synchronous oscillation control system in accordance with one embodiment of the present invention; and

FIG. 5 is a block diagram of an additional control module according to one embodiment of the invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

These and other aspects of embodiments of the invention will be apparent with reference to the following description and attached drawings. In the description and drawings, particular embodiments of the invention have been disclosed in detail as being indicative of some of the ways in which the principles of the embodiments of the invention may be practiced, but it is understood that the scope of the embodiments of the invention is not limited correspondingly. On the contrary, the embodiments of the invention include all changes, modifications and equivalents coming within the spirit and terms of the claims appended hereto.

The inventor of the application discovers through a great deal of creative work that when the equivalent inductive reactance in the whole system is properly matched with the capacitive reactance parameter (meeting the oscillation condition) after the wind turbine is connected to the grid, the oscillation can be generated, and the effective method for eliminating the oscillation is to change the system operation mode to change the system parameter and destroy the oscillation generation condition. Therefore, one of the most basic solutions to the problem of sub/super synchronous oscillation caused by the access of the wind power plant is to destroy the condition of system oscillation. By adopting certain additional measures, such as a parallel Static Var Generator (SVG) and adopting proper control, the formation of a disadvantageous oscillation loop is avoided, and the subsynchronous/supersynchronous oscillation problem of the system can be effectively suppressed.

The following describes a multi-mode additional sub/super synchronous oscillation control method and a control system according to an embodiment of the invention with reference to the accompanying drawings.

FIG. 1 is a flow chart of a multi-mode additional sub/super-synchronous oscillation control method according to an embodiment of the present invention. Fig. 2 is a schematic diagram illustrating the operation principle of the multi-mode additional sub/super-synchronous oscillation control method according to an embodiment of the present invention. Fig. 3 is a schematic overall flow diagram of a multi-mode additional sub/super-synchronous oscillation control method according to an embodiment of the present invention. With reference to fig. 1, 2 and 3, a multi-mode additional sub/super-synchronous oscillation control method according to an embodiment of the present invention includes the following steps:

s1: collecting total three-phase current i of fan side_cOr total three-phase current i on the line side_L。

Specifically, in order to implement the multi-mode additional sub/super-synchronous oscillation control method of the embodiment of the present invention, it is first required to accurately acquire a system signal. I.e. electrical quantities in the acquisition system and generate corresponding digital signals by means of analog-to-digital conversion. In particular, as shown in fig. 3, in the present example, the collected electrical quantities include: total three-phase current i of the fan side_cOr total three-phase current i on the line side_L。

The signals can be collected according to a fixed-interval sampling method, and analog-to-digital conversion is performed on the collected analog signals to obtain corresponding digital quantities. Methods that can achieve signal acquisition and analog-to-digital conversion are suitable for use with embodiments of the present invention. When the number of the side branches of the fan or the side branches of the power grid is multiple, the current of each line can be collected respectively, and the total current is obtained in a summing mode; and the side with few branches can be preferentially selected for signal acquisition according to the number of the branches in the actual system.

S2: according to the total three-phase current i of the fan side_cOr total three-phase current i on the line side_LA plurality of mode control signals are calculated.

Specifically, the purpose of step S2 is to calculate a plurality of mode control signals from the collected three-phase current signals, and use the mode control signals calculated in the process as the input quantity of the subsequently calculated additional control signals, where each sub/super-synchronous harmonic frequency band in the system corresponds to one sub/super-synchronous oscillation mode, and a mode additional control module is set up for each mode, and the additional control module includes, for example, the following sub-links: mode filtering, scaling/phase shifting, reference current calculation, mode control signal calculation, and mode control signal clipping. The implementation of the mode k is described below by taking the mode k as an example, where k is 1, …, N (N is the total number of controlled modes).

Specifically, in one embodiment of the present invention, step S2 further includes:

s21: total three-phase current i to fan side_cOr total three-phase current i on the line side_LAnd filtering to filter out subsynchronous and supersynchronous harmonic components. The filtering step is important for eliminating the influence of the power frequency signal on the additional subsynchronous/supersynchronous oscillation control method and obtaining subsynchronous/supersynchronous harmonic current components contained in the additional subsynchronous/supersynchronous oscillation control method. The main function of the filtering link is to filter out the total three-phase current i at the side of the fan_cOr total three-phase current i on the line side_LFiltering out the sub/super synchronous harmonic current component corresponding to the mode k.

Referring to fig. 3, that is, in step S21, the sub/super synchronous harmonic component corresponding to the pattern k is filtered out from the original three-phase current signal, and the influence of the fundamental wave and the noise is reduced. In one embodiment of the present invention, for example, the following two signal processing methods can be used:

1. and obtaining subsynchronous harmonic components and supersynchronous harmonic components through a band-pass filter. The center frequency of the band-pass filter corresponds to the sub/super synchronous frequency of the mode k to be filtered, and the specific implementation forms are various and are not described herein again. And/or

2. The total three-phase current i of the fan side is filtered by connecting a band-pass filter with a band-stop filter or a low-pass/high-pass filter in series_cOr total three-phase current i on the line side_LThe fundamental component (china corresponds to 50Hz) and the interference of other frequency components, and obtain subsynchronous and supersynchronous harmonic components, and the implementation forms of the methods are various and are not described herein again.

S22: the compensation of the phase delay generated by the measurement, filter and static var generator and/or the predetermined phase offset (set according to the actual control requirements) and amplitude compensation are performed, thereby improving the effect of the additional oscillation control method.

In a specific example, the scaling/phase shifting element in step S22 can be implemented by one of the following methods, for example, according to the system characteristics:

1) the phase shifter aims at carrying out proper phase compensation on the acquired current signals and has various realization methods, such as a high-pass/low-pass filtering phase shifter and the like.

2) And a proportion link, which aims to perform proper amplitude compensation on the acquired signals.

3) A series combination of 1) and 2) above.

The transfer function of a typical implementation is as follows:

$G_k\left(s\right)=g\frac{1+T_{a1,k}s+T_{a2,k}{s}^2+...+T_{am,k}{s}^m}{1+T_{b1,k}s+T_{b2,k}{s}^2+...+T_{bn,k}{s}^n},$

wherein g represents a proportionality coefficient, T_ai,k(i＝1,...,m),T_bi,k(i ═ 1.. times, n) denotes a time constant, m, n denotes the order of the transfer function numerator and denominator, and m, n are positive integers.

It should be noted that different transfer functions can be used for different modes, that is, parameters in the calculation formula of the transfer function can be different according to the controlled mode.

S23: converting the current signal after phase compensation and/or offset into three-phase reference current I of static var generator SVG_SVG,abc,k. Corresponding to different collected current signals, the link is divided into the following two conditions:

when the collected signal is the total three-phase current i of the fan side_cWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{I_{c,abc,k}\left(s\right)}{1+\frac{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{R_L+{\mathrm{sL}}_L}},$

when the collected signal is the total three-phase current i at the line side_LWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{R_L+{\mathrm{sL}}_L}{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{I}_{L,abc,k}\left(s\right),$

wherein, I_L,abc,k(s) and I_c,abc,k(s) represents the three-phase current of a, b, c on the line side and the fan side after the signal processing in the mode k, k is 1, …, N, N is the total number of the controlled modes, I_SVG,abc,k(s) a, b, c three-phase values, R, of the three-phase reference currents of the SVG calculated in mode k_L、L_LRespectively representing the equivalent resistance and inductance, R, of the line side_SVG,k、L_SVG,kFor the control parameters, the additional equivalent resistance and inductance of the static var generator which can be set in mode k are respectively indicated, where R_SVG,kA very small positive or zero value may be taken.

S24: according to the three-phase reference current I of the static var generator_SVG,abc,kAnd calculating a plurality of mode control signals sent to the static var generator by the reference value received by the static var generator. Corresponding to the difference that the SVG receives the reference value, the link can be divided into the following three conditions:

when the reference value received by the static var generator is current,

${\mathrm{\ΔI}}_{SVG,abc,k}^{*}\left(s\right)=I_{SVG,abc,k}\left(s\right),$

wherein,an additional mode current control signal corresponding to mode k for the static var generator.

When the reference value received by the static var generator is the access bus voltage,

${\mathrm{\ΔV}}_{abc,k}^{*}\left(s\right)=-I_{SVG,abc,k}\left(s\right)*(R_L+{\mathrm{sL}}_L),$

wherein,an additional mode voltage control signal corresponding to mode k is for the static var generator.

When the reference value received by the static var generator is reactive power and the inductive reactive power is absorbed as the positive direction, then

${\mathrm{\Δq}}_k^{*}=I_{SVG,abc,k}*V_{abc},$

Wherein,additional instantaneous reactive power mode control signal, V, corresponding to mode k for the SVG_abcAnd the fundamental components of the three-phase voltage of the static var generator connected to the bus are shown.

S25: and carrying out amplitude limiting processing on the plurality of mode control signals so that the amplitudes of the plurality of mode control signals are within a second preset range. Specifically, a larger mode control signal may damage the SVG controller, and therefore, a mode control signal amplitude limiting process is required, which mainly aims to limit the amplitude of the calculated mode control signal within a certain range (a second preset range), and when the input mode control signal is higher than an upper limit value of the second preset range or lower than a lower limit value of the second preset range, the output mode control signal is limited to a certain constant value and is not changed with the input signal, wherein the constant value is within the second preset range.

In step S25, a simple digital bidirectional slicer may be used, for example, and a typical calculation formula is as follows:

$X_{k,out}=\left\{\begin{array}{cc}{X}_{k,max}& X_{k,in}>X_{k,max}\\ X_{k,in}& X_{k,\min }\&le;X_{k,in}\&le;X_{k,max}\\ X_{k,\min }& X_{k,in}<X_{k,\min }\end{array}\right.,$

wherein, X_k,inMode control signals representing the mode clipping element inputs in mode k, corresponding to different reference values, X, received by the SVG_k,outMode control signal, X, representing the actual effect on the SVG output of the clipping element in mode k_k,max、X_k,minRespectively representing the maximum and minimum acceptable mode control signal values, i.e. X, for the SVG due to other constraints_k,max、X_k,minRespectively, an upper limit value and a lower limit value of the second preset range.

Step S3: the plurality of mode control signals are summed to obtain an additional control signal.

In one embodiment of the present invention, in step S3, for each mode control signal amplitude, for example, by directly adding (i.e., directly adding) a plurality of mode control signals to obtain an additional control signal; or

The weights of the plurality of mode control signals may also be set, and the plurality of mode control signals are added according to a weight ratio to obtain an additional control signal, which is specifically implemented as follows:

$X=\underset{k=1}{\overset{N}{\&Sigma;}}{w}_k{X}_k,$

wherein, w_kFor the weighting factors, w is added directly_k＝1，X_kIs the mode control signal corresponding to mode k, X is the additional control signal and N is the total number of modes.

Step S4: the additional control signal is subjected to a clipping process so that the amplitude of the additional control signal is within a first preset range.

Specifically, similar to the mode control signal clipping step described above, the SVG controller may be damaged by a larger additional control signal, and therefore, the additional control signal needs to be clipped, which mainly aims to limit the amplitude of the total additional control signal obtained by summing the mode control signals within a certain range (a first preset range), and when the input additional control signal is higher than the upper limit value of the first preset range or lower than the lower limit value of the first preset range, the output additional control signal is limited to a constant value and does not change with the change of the input signal, where the constant value is within the first preset range.

In a specific example, the clipping process for the additional control signal can be implemented by a simple digital bi-directional clipper, for example, and a typical calculation formula is as follows:

$X_{out}=\left\{\begin{array}{cc}{X}_{max}& X_{in}>X_{max}\\ X_{in}& X_{\min }\&le;X_{in}\&le;X_{max}\\ X_{\min }& X_{in}<X_{\min }\end{array}\right.,$

wherein, X_inAdditional control signals representing the input of the clipping element of the additional control signal, corresponding to different reference values, X, received by the SVG_outAdditional control signal, X, representing the output of the additional control signal clipping element, actually acting on the static var generator_max、X_minRespectively, the maximum and minimum acceptable additional control signal values, i.e. X, due to the SVG or other constraints_max、X_minRespectively, an upper limit value and a lower limit value of the first preset range.

It should be noted that, the signal processing in the above example is performed in the abc three-phase coordinate, or the signal may be subjected to forward Park transformation to obtain a dq coordinate system quantity, and then, the calculation is performed correspondingly to obtain a control quantity in the dq coordinate system, and if the control interface of the static var generator is defined in the dq coordinate system, the control interface may be directly output to the control interface; and if the control interface of the static var generator is defined under the abc coordinate system, obtaining the control signal under the abc coordinate system through reverse Park transformation.

In summary, the multi-mode additional subsynchronous/supersynchronous oscillation control method in the above embodiment of the present invention has a simple principle, and can automatically adjust the control signal of the SVG according to the system characteristics to achieve the purpose of suppressing subsynchronous/supersynchronous oscillation. The whole link of the method comprises signal acquisition and conversion, filtering, amplitude limiting and the like, all can be realized by a simple circuit, the whole structure is simple, engineering realization is easy, a modular structure can be adopted, and the method is flexible and convenient to install and debug and easy to expand. Furthermore, the method adopts a mode-division independent control channel structure for processing signals of subsynchronous oscillation and supersynchronous oscillation, is favorable for carrying out relatively independent design on each mode, lightens the interference among the modes, is expected to realize more precise and efficient control on the multiple modes, and is suitable for the condition that the system has more than one oscillation mode, the modes are mutually influenced, and the consistent gain and the phase-shifting link cannot be adopted.

According to the multi-mode additional subsynchronous/supersynchronous oscillation control method provided by the embodiment of the invention, the total current of the side of the wind turbine or the side of the line is collected in real time, the additional control signal is calculated, and the static var generator is controlled to be equivalent to the inductive impedance connected in parallel with the bus at the subsynchronous/supersynchronous frequency of the oscillation, so that the oscillation generation condition of the system is damaged, and the subsynchronous/supersynchronous oscillation of the system when the wind power plant is accessed is effectively inhibited.

Further embodiments of the present invention also provide a multi-mode additional sub/super-synchronous oscillation control system.

Fig. 4 is a block diagram of a multi-mode additional sub/super-synchronous oscillation control system according to an embodiment of the present invention. As shown in fig. 4, the system 100 includes: a signal acquisition and conversion module 110, an additional control module 120, a mode control signal summation module 130, and an additional control signal clipping module 140.

Specifically, the signal collecting and converting module 110 is used for collecting the total three-phase current i of the wind turbine side in real time_cOr total three-phase current i on the line side_LAnd converted into corresponding digital signals.

The additional control module 120 is used to determine the total three-phase current i on the fan side_cOr total three-phase current i on the line side_LA plurality of mode control signals are calculated.

Further, as shown in fig. 5, the additional control module 120 includes: a filtering module 121, a proportion/phase shift module 122, a reference current calculation module 123, a mode control signal calculation module 124, and a mode control signal clipping module 125.

Wherein, the filtering module 121 is used for the total three-phase current i of the fan side_cOr total three-phase current i on the line side_LAnd filtering to filter out subsynchronous and supersynchronous harmonic components. More specifically, the filtering module 121 is configured to: obtaining subsynchronous and supersynchronous harmonic components through a band-pass filter; and/or the total three-phase current i on the fan side is filtered by connecting a band-pass filter in series with a band-stop filter or a low-pass/high-pass filter_cOr total three-phase current i on the line side_LAnd sub-synchronous and super-synchronous harmonic components are obtained.

The scale/phase shift module 122 is used to compensate for phase delays generated by the measurement, filter and static var generator, and/or to perform predetermined phase offset and amplitude compensation.

The reference current calculation module 123 is configured to convert the phase-compensated and/or offset current signal into a three-phase reference current I of the static var generator_SVG,abc,kThe method specifically comprises the following steps:

when the collected signal is the total three-phase current i of the fan side_cWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{I_{c,abc,k}\left(s\right)}{1+\frac{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{R_L+{\mathrm{sL}}_L}},$

when the collected signal is the total three-phase current i at the line side_LWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{R_L+{\mathrm{sL}}_L}{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{I}_{L,abc,k}\left(s\right),$

wherein, I_L,abc,k(s) and I_c,abc,k(s) represents the three-phase current of a, b, c on the line side and the fan side after the signal processing in the mode k, k is 1, …, N, N is the total number of the controlled modes, I_SVG,abc,k(s) a, b, c three-phase values, R, of the three-phase reference currents of the SVG calculated in mode k_L、L_LRespectively representing the equivalent resistance and inductance, R, of the line side_SVG,k、L_SVG,kFor the control parameters, the additional equivalent resistance and inductance of the static var generator that can be set in mode k are indicated, respectively.

The mode control signal calculation module 124 is used for calculating the three-phase reference current I according to the static var generator_SVG,abc,kAnd calculating a plurality of mode control signals sent to the static var generator by the reference value received by the static var generator. More specifically, the mode control signal calculation module 124 is configured to: when the reference value received by the static var generator is current,

${\mathrm{\&Delta;I}}_{SVG,abc,k}^{*}\left(s\right)=I_{SVG,abc,k}\left(s\right),$

wherein,an additional mode current control signal corresponding to mode k for the static var generator;

when the reference value received by the static var generator is the access bus voltage,

${\mathrm{\&Delta;V}}_{abc,k}^{*}\left(s\right)=-I_{SVG,abc,k}\left(s\right)*(R_L+{\mathrm{sL}}_L),$

wherein,an additional mode voltage control signal corresponding to mode k for the static var generator;

when the reference value received by the static var generator is reactive power,

${\mathrm{\&Delta;q}}_k^{*}=I_{SVG,abc,k}*V_{abc},$

wherein,additional instantaneous reactive power mode control signal, V, corresponding to mode k for the SVG_abcAnd the fundamental components of the three-phase voltage of the static var generator connected to the bus are shown.

The mode control signal clipping module 125 is configured to clip the plurality of mode control signals so that the amplitudes of the plurality of mode control signals are within a second preset range.

The mode control signal summing module 130 is configured to sum the plurality of mode control signals to obtain an additional control signal.

Specifically, the mode control signal summing module 130 is configured to, for example: directly adding the plurality of mode control signals to obtain an additional control signal; or setting weights of a plurality of mode control signals, and adding the plurality of mode control signals according to the weight proportion to obtain an additional control signal, specifically comprising:

$X=\underset{k=1}{\overset{N}{\&Sigma;}}{w}_k{X}_k,$

wherein, w_kFor the weighting factors, w is added directly_k＝1，X_kIs the mode control signal corresponding to mode k, X is the additional control signal and N is the total number of modes.

The additional control signal limiting module 140 is configured to perform a limiting process on the additional control signal so that the amplitude of the additional control signal is within a first preset range.

It should be noted that a specific implementation manner of the multi-mode additional sub/super synchronous oscillation control system according to the embodiment of the present invention is similar to a specific implementation manner of the multi-mode additional sub/super synchronous oscillation control method according to the embodiment of the present invention, and reference is specifically made to the description of the method portion, and details are not repeated in order to reduce redundancy.

In addition, other configurations and functions of the multi-mode additional sub/super-synchronous oscillation control system according to the embodiment of the present invention are known to those skilled in the art, and are not described in detail for reducing redundancy.

In summary, according to the multi-mode additional subsynchronous/supersynchronous oscillation control system provided by the embodiment of the invention, the total current of the wind turbine side or the line side is collected in real time, the additional control signal is calculated, the static var generator is controlled to be equivalent to the inductive impedance connected in parallel with the bus at the subsynchronous/supersynchronous frequency of oscillation, and the oscillation generating condition of the system is destroyed, so that subsynchronous/supersynchronous oscillation of the system when the wind power plant is accessed is effectively inhibited.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims (10)

1. A multi-mode additional subsynchronous/supersynchronous oscillation control method is characterized by comprising the following steps of:

s1: collecting total three-phase current i of fan side_cOr total three-phase current i on the line side_L；

S2: according to the total three-phase current i of the fan side_cOr total three-phase current i on the line side_LCalculating to obtain a plurality of mode control signals;

s3: summing the plurality of mode control signals to obtain an additional control signal; and

s4: and carrying out amplitude limiting processing on the additional control signal so that the amplitude of the additional control signal is within a first preset range.

2. The multi-mode additional sub/super-synchronous oscillation control method of claim 1, wherein the S2 further comprises:

s21: to total three-phase current i of the fan side_cOr the total three-phase current i of the line side_LFiltering to filter out subsynchronous and supersynchronous harmonic components;

s22: compensating for phase delays generated by the measurement, filter and said static var generator, and/or performing predetermined phase offset and amplitude compensation;

s23: converting the phase compensated and/or offset current signal into a three-phase reference current I of a static var generator_SVG,abc,kThe method specifically comprises the following steps:

when the collected signal is the total three-phase current i of the fan side_cWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{I_{c,abc,k}\left(s\right)}{1+\frac{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{R_L+{\mathrm{sL}}_L}},$

when the collected signal is the total three-phase current i at the line side_LWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{R_L+{\mathrm{sL}}_L}{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{I}_{L,abc,k}\left(s\right),$

wherein, I_L,abc,k(s) and I_c,abc,k(s) represents the three-phase current of a, b, c on the line side and the fan side after the signal processing in the mode k, k is 1, …, N, N is the total number of the controlled modes, I_SVG,abc,k(s) a, b, c three-phase values, R, of the three-phase reference currents of the SVG calculated in mode k_L、L_LRespectively representing the equivalent resistance and inductance, R, of the line side_SVG,k、L_SVG,kThe additional equivalent resistance and the inductance of the static var generator which can be set in the mode k are respectively expressed as control parameters;

s24: according to the three-phase reference current I of the static var generator_SVG,abc,kCalculating a plurality of mode control signals sent to the static var generator according to the reference values received by the static var generator;

s25: and carrying out amplitude limiting processing on the plurality of mode control signals so that the amplitudes of the plurality of mode control signals are within a second preset range.

3. The multi-mode additional sub/super-synchronous oscillation control method of claim 2, wherein the S21 further comprises:

obtaining the subsynchronous harmonic component and the supersynchronous harmonic component through a band-pass filter; and/or

Filtering out the total three-phase current i of the fan side by connecting a band-pass filter with a band-stop filter or a low-pass/high-pass filter in series_cOr the total three-phase current i of the line side_LAnd obtaining the subsynchronous and supersynchronous harmonic components.

4. The multi-mode additional sub/super-synchronous oscillation control method according to claim 2, wherein the step S24 further comprises:

when the reference value received by the static var generator is a current,

${\mathrm{\&Delta;I}}_{SVG,abc,k}^{*}\left(s\right)=I_{SVG,abc,k}\left(s\right),$

wherein,an additional mode current control signal corresponding to mode k for the static var generator;

when the reference value received by the static var generator is the access bus voltage,

${\mathrm{\&Delta;V}}_{abc,k}^{*}\left(s\right)=-I_{SVG,abc,k}\left(s\right)*(R_L+{\mathrm{sL}}_L),$

wherein,an additional mode voltage control signal corresponding to mode k for the static var generator;

when the reference value received by the static var generator is reactive power,

${\mathrm{\&Delta;q}}_k^{*}=I_{SVG,abc,k}*V_{abc},$

wherein,additional instantaneous reactive power mode control signal, V, corresponding to mode k for the SVG_abcAnd representing the fundamental components of the three-phase voltage of the access bus of the static var generator.

5. The multi-mode additional sub/super-synchronous oscillation control method according to claim 1, wherein in said S3,

obtaining the additional control signal by directly adding the plurality of mode control signals; or

Setting weights of a plurality of mode control signals, and adding the plurality of mode control signals according to a weight proportion to obtain the additional control signal, specifically comprising:

$X=\underset{k=1}{\overset{N}{\&Sigma;}}{w}_k{X}_k,$

wherein, w_kFor the weighting factors, w is added directly_k＝1，X_kIs the mode control signal corresponding to mode k, X is the additional control signal and N is the total number of modes.

6. A multi-mode additional sub/super-synchronous oscillation control system, comprising:

the signal acquisition and conversion module is used for acquiring the total three-phase current i of the side of the fan in real time_cOr total three-phase current i on the line side_LAnd converted into corresponding digital signals;

an additional control module for determining a total three-phase current i of the wind turbine side_cOr total three-phase current i on the line side_LCalculating to obtain a plurality of mode control signals;

the mode control signal summing module is used for summing the mode control signals to obtain an additional control signal; and

and the additional control signal amplitude limiting module is used for carrying out amplitude limiting processing on the additional control signal so as to enable the amplitude of the additional control signal to be within a first preset range.

7. The multi-mode additional sub/super-synchronous oscillation control system of claim 6 wherein the additional control module comprises:

a filtering module for filtering a total three-phase current i of the fan side_cOr the total three-phase current i of the line side_LFiltering is carried outFiltering out subsynchronous and supersynchronous harmonic components;

a proportional/phase shift module for compensating for phase delays generated by the measurement, filter and the static var generator, and/or for performing predetermined phase offset and amplitude compensation;

a reference current calculation module for converting the phase compensated and/or offset current signal into a three-phase reference current I of the SVG_SVG,abc,kThe method specifically comprises the following steps:

when the collected signal is the total three-phase current i of the fan side_cWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{I_{c,abc,k}\left(s\right)}{1+\frac{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{R_L+{\mathrm{sL}}_L}},$

when the collected signal is the total three-phase current i at the line side_LWhen the temperature of the water is higher than the set temperature,

$I_{SVG,abc,k}\left(s\right)=\frac{R_L+{\mathrm{sL}}_L}{R_{SVG,k}+{\mathrm{sL}}_{SVG,k}}{I}_{L,abc,k}\left(s\right),$

wherein, I_L,abc,k(s) and I_c,abc,k(s) represents the three-phase current of a, b, c on the line side and the fan side after the signal processing in the mode k, k is 1, …, N, N is the total number of the controlled modes, I_SVG,abc,k(s) in the expression pattern kCalculated a, b, c three-phase values, R, of the three-phase reference currents of the SVG_L、L_LRespectively representing the equivalent resistance and inductance, R, of the line side_SVG,k、L_SVG,kThe additional equivalent resistance and the inductance of the static var generator which can be set in the mode k are respectively expressed as control parameters;

a mode control signal calculation module for calculating a three-phase reference current I of the SVG according to the three-phase reference current I_SVG,abc,kCalculating a plurality of mode control signals sent to the static var generator according to the reference values received by the static var generator;

and the mode control signal amplitude limiting module is used for carrying out amplitude limiting processing on the plurality of mode control signals so as to enable the amplitudes of the plurality of mode control signals to be within a second preset range.

8. The multi-mode additional sub/super-synchronous oscillation control system of claim 7, wherein the filtering module is configured to:

obtaining the subsynchronous harmonic component and the supersynchronous harmonic component through a band-pass filter; and/or

Filtering out the total three-phase current i of the fan side by connecting a band-pass filter with a band-stop filter or a low-pass/high-pass filter in series_cOr the total three-phase current i of the line side_LAnd obtaining the subsynchronous and supersynchronous harmonic components.

9. The multi-mode additional sub/super-synchronous oscillation control system of claim 7, wherein the mode control signal calculation module is configured to:

when the reference value received by the static var generator is a current,

${\mathrm{\&Delta;I}}_{SVG,abc,k}^{*}\left(s\right)=I_{SVG,abc,k}\left(s\right),$

wherein,an additional mode current control signal corresponding to mode k for the static var generator;

when the reference value received by the static var generator is the access bus voltage,

${\mathrm{\&Delta;V}}_{abc,k}^{*}\left(s\right)=-I_{SVG,abc,k}\left(s\right)*(R_L+{\mathrm{sL}}_L),$

wherein,an additional mode voltage control signal corresponding to mode k for the static var generator;

when the reference value received by the static var generator is reactive power,

${\mathrm{\&Delta;q}}_k^{*}=I_{SVG,abc,k}*V_{abc},$

wherein,additional instantaneous reactive power mode control signal, V, corresponding to mode k for the SVG_abcAnd representing the fundamental components of the three-phase voltage of the access bus of the static var generator.

10. The multi-mode additional sub/super-synchronous oscillation control system of claim 6, wherein the mode control signal summing module is configured to:

directly adding the plurality of mode control signals to obtain the additional control signal; or

Setting weights of a plurality of mode control signals, and adding the plurality of mode control signals according to a weight proportion to obtain the additional control signal, specifically comprising:

$X=\underset{k=1}{\overset{N}{\&Sigma;}}{w}_k{X}_k,$

wherein, w_kFor the weighting factors, w is added directly_k＝1，X_kIs the mode control signal corresponding to mode k, X is the additional control signal and N is the total number of modes.