CN105207236B - Suppression sub-synchronous oscillation adaptive control system based on SVG - Google Patents
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Abstract
The present invention relates to a kind of suppression sub-synchronous oscillation adaptive control system based on SVG, belong to power system stability and control field.A kind of suppression sub-synchronous oscillation adaptive control system based on SVG, including AD data acquisition devices, preposition junction filter, discrete Fourier transform and sub-synchronous oscillation frequency estimation device, multichannel stand-alone mode control ring, online adaptive adjuster and power signal generating means.The control signal that the present invention is obtained by the adaptive control system, the power current for suppressing sub-synchronous oscillation based on the control signal is produced using SVG, it is strong to the frequency adaptivity of sub-synchronous oscillation, it is full-featured, it can effectively suppress power network sub-synchronous oscillation.
Description
Technical Field
The invention relates to the field of power system stabilization and control, in particular to a self-adaptive control system for suppressing subsynchronous oscillation based on SVG.
Background
At present, the development of new energy sources such as wind power stations and photovoltaic power stations in wind power plants in China has the characteristics of large-scale development, centralized grid connection and remote transmission, and a high-voltage direct-current power transmission system is established and operated by a plurality of lines in China as an effective means for solving the problems of large-capacity remote transmission and cross-regional power grid interconnection. However, a HVDC power transmission system for large-scale new energy grid connection of wind power, photovoltaic energy and the like and the rapid active control characteristic of the HVDC power transmission system are easy to cause subsynchronous oscillation, so that a steam turbine generator unit is damaged, and the safe operation of a power system is seriously threatened.
The existing subsynchronous oscillation suppression method mainly comprises a blocking filter, additional excitation damping control realized by SEDC/PSS and additional damping control realized by SVC/SVG.
At present, a new energy grid-connected system such as a wind power station photovoltaic power station and the like generally configures reactive power compensation capacity with certain capacity, but most SVCs or SVGs do not have a subsynchronous oscillation suppression function or have a limited suppression function, mainly because SVC compensation equipment strategies are not suitable, the response speed is low, and the voltage characteristic is poor. On the one hand, the conventional control system for inhibiting the subsynchronous oscillation based on the SVG is based on a rotating speed feedback signal, and on the other hand, the structure is often not capable of obtaining the rotating speed signal in a new energy grid-connected system such as a wind power plant or a photovoltaic power station; on the other hand, the rotating speed input control system is single, the frequency component analysis is simple, and the ideal control effect of the multi-mode oscillation frequency of the unit cannot be achieved.
Disclosure of Invention
Aiming at the problems, the invention provides the SVG-based adaptive control system for suppressing the subsynchronous oscillation, which can suppress the subsynchronous oscillation of a typical wind power plant or a new energy grid-connected system such as photovoltaic power generation and the like and enhance the operation stability and reliability of the system.
The purpose of the invention is realized as follows:
an adaptive control system for suppressing subsynchronous oscillation based on SVG (scalable vector graphics), comprising:
the AD data acquisition device is used for acquiring subsynchronous oscillation voltage, current or power signals of SVG compensation points or common access points of a system where the SVG is located;
the pre-combined filter is used for performing low-pass, band-pass or band-stop filtering on signals containing subsynchronous oscillation voltage, current or power information acquired by the AD data acquisition device so as to obtain subsynchronous and subsynchronous complementary frequency signals in the voltage, current or power signals, and the implementation modes of the pre-combined filter are various and can be a mode of connecting a band-pass filter and a band-stop filter in series, or a mode of connecting a plurality of band-pass filters in parallel, or a mode of using a low-pass filter and the like; the prepositive combination filter is an optional part, and if not, the signal obtained by the AD data acquisition device directly enters the next data processing link;
the device comprises a discrete Fourier transform and subsynchronous oscillation frequency identifier, a frequency conversion module and a frequency conversion module, wherein the discrete Fourier transform and subsynchronous oscillation frequency identifier is used for performing discrete Fourier transform on voltage, current or power signals which are output by an AD data acquisition device or a pre-combination filter and contain subsynchronous and subsynchronous complementary frequency signals so as to acquire the amplitude and the phase of each subsynchronous and subsynchronous complementary frequency signal, and performing subsynchronous oscillation frequency identification on the amplitude and the phase so as to finally acquire the amplitude and the frequency of each frequency subsynchronous and subsynchronous complementary frequency signal;
a multi-channel independent mode control loop including a combined mode filter having a plurality of channels, a combined proportional phase shifter, and a synthetic regulator; the combined mode filter combines the amplitude and the phase of the subsynchronous and subsynchronous complementary frequency signals of each frequency obtained by the discrete Fourier transform and the subsynchronous oscillation frequency identifier to carry out mode filtering on the voltage, current or power signals which are output by the AD data acquisition device or the preposed combined filter and contain the subsynchronous and subsynchronous complementary frequency signals of each frequency to obtain the subsynchronous and subsynchronous complementary frequency signals of each frequency; the combined proportional phase shifter is used for compensating the phase delay of the voltage, current or power signals containing the subsynchronous and subsynchronous complementary frequency signals after passing through the combined mode filter, and converting the signals after phase compensation into mode control signals of the subsynchronous and subsynchronous complementary frequency signals of each frequency after proportional amplification; the comprehensive adjuster is used for summing and amplitude limiting the control signals of all modes obtained by the combined proportional phase shifter to obtain the final control signal of the total mode;
the online self-adaptive regulator is used for starting the automatic regulation of control parameters when the SVG controller monitors that a sub-synchronous component to be compensated occurs in the system under the condition of no sub-synchronous compensation component output, wherein the control parameters comprise the number of channels of mode filtering, the gain of each channel of the combined proportional phase shifter and the comprehensive regulator and the phase shift of each channel;
and the power signal generating device is used for generating a final current instruction and converting the final current instruction into a power switch pulse signal according to a total mode control signal obtained by the multi-channel independent mode control loop and a control signal required by control of SVG (scalable vector graphics) direct-current voltage and the like, and generating current and power capable of inhibiting subsynchronous oscillation.
The pre-combining filter can be set to be one of the following five implementation modes:
the first mode is to set two filters for series combination of voltage and current signals, the first filter is a second-order band-pass filter, the transfer function of which is formula 1, the second filter is a second-order fundamental wave band-stop filter, the transfer function of which is formula 2:
in the formula 1, G 01 Is the pass band gain, omega, of a band-pass filter 01 Is the central angular frequency, xi, of the band-pass filter 01 Is the damping coefficient of the band-pass filter;
in the formula 2, G 02 For fundamental pass band gain, omega, of band-stop filters 02 Is the central angular frequency, xi, of the band-stop filter 02 The damping coefficient of the band elimination filter;
in a second mode, two band-pass filters are arranged for parallel combination of voltage and current signals, the first filter and the second filter are both second-order band-pass filters, and the transfer function is formula 3:
in formula 3, G 03 Is the pass band gain, omega, of a band-pass filter 03 Is the central angular frequency, xi, of the band-pass filter 03 Is the damping coefficient of the filter;
in a third mode, 1 second-order low-pass filter is set for the voltage and current signals, and the transfer function of the filter is equation 4:
in the formula 4, G 04 Is the pass band gain, omega, of a low-pass filter 04 Is the natural angular frequency, xi, of the low-pass filter 04 Is the damping coefficient of the filter;
and a fourth mode, setting 1 second-order band-pass filter or more than 1 band-pass and low-pass filter combination aiming at the voltage, current or power signal, wherein the transfer function of the low-pass filter is formula 4, and the transfer function of the band-pass filter is formula 5:
in formula 5, G 05 Pass band gain, omega, of a band-pass filter 05 Is the central angular frequency, xi, of the band-pass filter 05 Is the damping coefficient of the filter;
in a fifth mode, the pre-combined filter is an optional part for voltage and current signals, under the condition, the acquired subsynchronous oscillation voltage, current and power signals are not processed, and the data signals acquired by the AD data acquisition device directly enter the next data processing link.
The discrete Fourier transform and subsynchronous oscillation frequency identifier can realize the self-adaptive identification of subsynchronous oscillation frequency of full-time synchronous bandwidth and complementary frequency thereof, and the self-adaptive identification process specifically comprises the following steps:
firstly, obtaining two arrays by discrete Fourier calculation, wherein an array F = [ F1, \8230 ], an array F represents the frequency of each signal of voltage, current or power, m frequency components are counted, an array A = [ A1, \8230 ], and an array Am represents the amplitude of each frequency component corresponding to a frequency signal array;
then, the subsynchronous oscillation frequency and amplitude set is identified according to the following process:
step 1, setting a subsynchronous frequency set as Fs = [ ], initially setting the subsynchronous frequency set as null, and presetting an initial bandwidth delta f to be 4-10 Hz;
step 2, setting signal amplitudes corresponding to all frequencies as Aj (j =1, \8230;, m), and setting Aj to 0 if Aj is smaller than or equal to a preset threshold amplitude Ath;
step 3, with the frequency as abscissa X and the amplitude as ordinate Y, plotting a frequency signal array [ F1, \8230;, fm ] and amplitude signal array [ A1, \8230;, am ] into a frequency spectrogram, finding out amplitude peak points corresponding to all frequency components in the spectrogram according to the frequency spectrogram, setting the frequency signal array FP = [ FP1, \8230;, fpn ], the peak signal array Ap = [ Ap1, \8230;, apn of each corresponding frequency signal, and if Fpj (j =1, \8230, n) is null, indicating that subsynchronous oscillation of the corresponding pj (j =1, \8230;, n) frequencies occurs in the power grid, and turning to step 6;
step 4, if the intervals among the frequencies of the frequency signal arrays Fp corresponding to all the peak value signal arrays Ap are larger than delta f/2, the Fp is the identified subsynchronous oscillation frequency array, the identification is completed, the step 6 is skipped, and otherwise the step 5 is continuously executed;
step 5 for the two amplitude peak point frequencies Fpj and Fpk with the smallest frequency interval of the frequency signal array Fp (where Fpj < Fpk, (j =1, \8230;, n), (k =1, \8230;, n)), the 2 frequencies are absorption combined, and the principle of absorption combination is:
after merging, the new peak point frequency is Fpjk (j =1, \8230;, n), (k =1, \8230;, n):
after merging, the new peak point frequency corresponds to a peak of Apjk (j =1, \8230;, n), (k =1, \8230;, n):
after the new frequency and peak value of each frequency point are updated, updating the set frequency signal array Fp and the peak value signal array Ap, and jumping to the step 4;
and 6, obtaining a frequency signal array Fp and a peak signal array Ap, namely identifying and obtaining a set of subsynchronous frequency point frequency and amplitude thereof, setting K as the number of frequency elements in the frequency signal array Fp, and if K is 0, indicating that the subsynchronous oscillation does not occur in the power grid system.
The combined mode filter is a band-pass filter with adjustable center frequency and bandwidth, and the transfer function of the combined mode filter is formula 6:
in formula 6, G i Is the pass band gain, omega, of a band-pass filter i Is the central angular frequency, xi, of the band-pass filter i For the damping coefficient of the filter, i ∈ [1,N ]]。
7. Wherein, the combined proportional phase shifter is a proportional phase correction filter, and its transfer function is equation 7:
in formula 7, K c For proportional coefficients of proportional phase correction filters, T c The phase shift compensation time constant of the proportional phase correction filter is determined by the frequency of variable subsynchronous and subsynchronous complementary frequency signals, a fixed sampling delay time constant and a fixed control delay time constant;
the proportional phase correction filter is used for performing phase compensation on phase delay caused by analog quantity measurement, combined mode filtering and SVG control delay in signals containing subsynchronous and subsynchronous complementary frequency components obtained by the combined mode filter, phase delay caused by sampling and holding link of the analog quantity measurement, phase shift caused by inconsistent phase shift characteristics of different frequency components of a band-pass filter adopted in the combined mode filter, and delay of generating power signals by the SVG control link, phase deviation needs to be compensated, and the compensation target is that the phase shift at the central frequency of the mode filtering is zero and the phase shift corresponding to the acquisition of the analog quantity and the control delay time constant is compensated.
The online adaptive regulator can perform online adaptive regulation of parameters, and is started when a to-be-compensated subsynchronous component of a system is monitored to appear under the condition that the SVG controller does not output subsynchronous compensation components, the control parameters comprise the number of channels of mode filtering, and online updating can be performed; the adjustment of the channel gain is in direct proportion to a to-be-compensated subsynchronous component peak signal obtained by the discrete Fourier transform and subsynchronous oscillation frequency identifier, and a total mode control signal generated by the multichannel independent mode control loop is not more than 50% of the rated current of the SVG; the basic principle of adjusting the compensation phase of each channel is that the current/power absorbed by the SVG device is in phase with the subsynchronous oscillation current/power existing on the subsynchronous oscillation source side, or the deviation amount in the possible operation mode under various practical working conditions does not exceed 60 degrees.
The beneficial effects of the invention are as follows:
1. the compensation of each subsynchronous oscillation frequency and the complementary frequency wide range and multi-frequency points is realized, and the suppression function is comprehensive.
2. The additional damping control based on the SVG can realize multipoint distribution compensation, does not need extra cost, and has the advantages of simple realization, self-adaptive control and wide applicability.
Drawings
FIG. 1 is a block diagram of a control system of the present invention.
FIG. 2 is a diagram of a sub-synchronous current source waveform of a simulation experiment in an embodiment of the present invention.
FIG. 3 is a graph of the spectrum output by the DFT and SSO frequency identifier of the simulation experiment in the embodiment of the present invention.
FIG. 4 is a diagram showing a comparison of 5Hz original waveforms in multiple frequency components of a simulated experimental simulation subsynchronous oscillation current source and waveforms obtained after processing and restoring by the control system in the embodiment of the invention.
Detailed Description
The invention will be further elucidated with reference to the specific embodiments and the accompanying drawings.
As shown in fig. 1, an SVG-based adaptive control system for suppressing subsynchronous oscillation includes an AD data acquisition device 1, a pre-combining filter 2, a discrete fourier transform and subsynchronous oscillation frequency identifier 3, a multi-channel independent mode control loop 4, an online adaptive regulator 5, and a power signal generation device 6.
And the AD data acquisition device 1 is used for acquiring voltage, current or power signals containing subsynchronous oscillation information of SVG compensation points or common access points of a system where the SVG is located.
And the pre-combined filter 2 is used for performing low-pass, band-pass or band-stop filtering on the subsynchronous oscillation voltage, current or power signals acquired by the AD data acquisition device 1 so as to obtain subsynchronous and subsynchronous complementary frequency signals in the voltage, current or power signals.
The implementation manner of the pre-combining filter 2 is that a plurality of filters can be selected to be combined or no filter is selected, and according to different situations, the implementation manner can be specifically set as one of the following five implementation manners:
the first mode is to set two filters for series combination of voltage and current signals, the first filter is a second-order band-pass filter, the transfer function of which is formula 1, the second filter is a second-order fundamental wave band-stop filter, the transfer function of which is formula 2:
in formula 1, G 01 Is the pass band gain, omega, of a band-pass filter 01 Is the central angular frequency, xi, of the band-pass filter 01 The damping coefficient of the band-pass filter;
in the formula 2, G 02 Fundamental passband gain, omega, for a band stop filter 02 Is the central angular frequency, xi, of the band-stop filter 02 The damping coefficient of the band elimination filter;
in a second mode, two band-pass filters are arranged for parallel combination of voltage and current signals, the first filter and the second filter are both second-order band-pass filters, and the transfer function is formula 3:
in formula 3, G 03 Is the pass band gain, omega, of a band-pass filter 03 Is the central angular frequency, xi, of the band-pass filter 03 Is the damping coefficient of the filter;
in a third mode, 1 second-order low-pass filter is set for the voltage and current signals, and the transfer function of the filter is equation 4:
in the formula 4, G 04 Is the pass band gain, omega, of a low-pass filter 04 Is the natural angular frequency, xi, of the low-pass filter 04 Is the damping coefficient of the filter;
and a fourth mode, setting 1 second-order band-pass filter or more than 1 band-pass and low-pass filter combination aiming at the voltage, current or power signal, wherein the transfer function of the low-pass filter is formula 4, and the transfer function of the band-pass filter is formula 5:
in formula 5, G 05 Is the pass band gain, omega, of a band-pass filter 05 Is the central angular frequency, xi, of the band-pass filter 05 Is the damping coefficient of the filter;
in a fifth mode, the pre-combined filter is an optional part for voltage and current signals, under the condition, the acquired subsynchronous oscillation voltage, current and power signals are not processed, and the data signals acquired by the AD data acquisition device directly enter the next data processing link.
The discrete fourier transform and subsynchronous oscillation frequency identifier 3 is configured to perform discrete fourier transform on a voltage, current, or power signal containing a subsynchronous and subsynchronous complementary frequency signal obtained by the AD data acquisition device 1 or the pre-combined filter 2 to obtain an amplitude and a phase of each subsynchronous and subsynchronous complementary frequency signal, and perform subsynchronous oscillation frequency identification on the amplitude and the phase to finally obtain an amplitude and a frequency of each frequency subsynchronous and subsynchronous complementary frequency signal. The discrete fourier transform and sub-synchronous oscillation frequency identifier 3 can realize the self-adaptive identification of the sub-synchronous oscillation frequency of the full sub-synchronous bandwidth and the complementary frequency thereof, wherein the optimal range of the sub-synchronous bandwidth is 2 to 50hz, and the self-adaptive identification process is as follows:
firstly, two arrays are obtained through discrete Fourier calculation, wherein an array F = [ F1, \8230; fm ] represents the frequency of each signal of voltage, current or power, m frequency components are counted, and an array A = [ A1, \8230; am ] represents the amplitude of each frequency component corresponding to the frequency signal array.
Then, the subsynchronous oscillation frequency and amplitude set is identified according to the following process:
step 1, setting a subsynchronous frequency set as Fs = [ ], initially setting the subsynchronous frequency set as null, and presetting an initial bandwidth delta f to be 4-10 Hz;
step 2, setting signal amplitudes corresponding to all frequencies as Aj (j =1, \8230;, m), and setting Aj to 0 if Aj is smaller than or equal to a preset threshold amplitude Ath;
step 3, with the frequency as an abscissa X and the amplitude as an ordinate Y, drawing a frequency spectrum diagram of the frequency signal array [ F1, \8230;, fm ] and the amplitude signal array [ A1, \8230;, am ], finding peak amplitude points corresponding to all frequency components in the diagram according to the frequency spectrum diagram, setting the peak amplitude points as frequency signal arrays Fp = [ Fp1, \8230, fpn ], and corresponding peak signal arrays Ap = [ Ap1, \ 8230;, apn if Fpj =1, \ 8230, n) is null, indicating that subsynchronous oscillation of corresponding pj (j =1, \\ 8230;, n) frequencies occurs in the power grid, and turning to step 6;
step 4, if the intervals among the frequencies of the frequency signal arrays Fp corresponding to all the peak value points of the peak value signal array Ap are larger than delta f/2, the Fp is the identified subsynchronous oscillation frequency array, the identification is finished, the step 6 is skipped, and otherwise the step 5 is continuously executed;
step 5 for the two amplitude peak point frequencies Fpj and Fpk with the smallest frequency separation of the frequency signal array FP (where Fpj < Fpk, (j =1, \8230;, n), (k =1, \8230;, n)), the 2 frequencies are absorption combined, the principle of absorption combination being:
after merging, the new peak point frequency is Fpjk (j =1, \8230;, n), (k =1, \8230;, n):
after combination, the new peak point frequency corresponds to a peak of Apjk (j =1, \8230;, n), (k =1, \8230;, n):
after the new frequency and peak value of each frequency point are updated, updating the set frequency signal array Fp and the peak value signal array Ap, and jumping to the step 4;
and 6, obtaining a frequency signal array Fp and a peak signal array Ap, namely identifying and obtaining a set of subsynchronous frequency point frequency and amplitude thereof, setting K as the number of frequency elements in the frequency signal array Fp, and if K is 0, indicating that the subsynchronous oscillation does not occur in the power grid system.
The multi-channel independent mode control loop 4 comprises a combined mode filter with multiple channels, a combined proportional phase shifter and a complex regulator.
The combined mode filter obtains the subsynchronous and subsynchronous complementary frequency signals of each frequency through the amplitude and the phase of the subsynchronous and subsynchronous complementary frequency signals of each frequency obtained by the discrete Fourier transform and the subsynchronous oscillation frequency identifier 3, and then performs mode filtering on the voltage, current or power signals of the subsynchronous and subsynchronous complementary frequency signals of each frequency obtained by the AD data acquisition device 1 or the pre-combined filter 2. In the system, the combined mode filter specifically adopts a band-pass filter with adjustable center frequency and bandwidth, and the transfer function of the band-pass filter is as shown in formula 6:
in formula 6, G i Pass band gain, omega, of a band-pass filter i Is the central angular frequency, xi, of the band-pass filter i For the damping coefficient of the filter, i ∈ [1,N ]]。
8. The combined proportional phase shifter is used for compensating the phase delay of the voltage, current or power signal which contains the subsynchronous and subsynchronous complementary frequency signals after passing through the combined mode filter, and converting the signal after the phase compensation into the mode control signal of the subsynchronous and subsynchronous complementary frequency signals of each frequency after amplifying the signal in proportion. In the system, the combined proportional phase shifter needs to compensate the phase delay caused by analog quantity measurement, combined mode filtering and SVG control delay in the voltage, current or power signals of subsynchronous and subsynchronous complementary frequency signals containing various frequencies obtained by the combined mode filter, and also needs to compensate the phase delay caused by the sampling and holding link of the analog quantity measurement, the phase shift caused by the inconsistency of the phase shift characteristics of different frequency components of the band-pass filter adopted in the combined mode filter and the phase deviation caused by the delay of the power signal generated by the SVG control link. The compensation target is that the phase shift at the central frequency of the mode filtering is zero, and the phase shift corresponding to the analog quantity acquisition and control delay time constant is compensated. Thus, the combined proportional phase shifter employed in the present system is a proportional phase correction filter with a transfer function of equation 7:
in formula 7, K c For proportional coefficients of proportional phase correction filters, T c The phase shift compensation time constant of the proportional phase correction filter is determined by the frequency of variable subsynchronous and subsynchronous complementary frequency signals, a fixed sampling delay time constant and a fixed control delay time constant;
the comprehensive adjuster is used for summing and limiting the control signals of all modes obtained by the combined proportional phase shifter to finally obtain the control signals of the total mode.
The online adaptive regulator 5 is used for starting automatic regulation of control parameters when the SVG controller monitors that the subsynchronous component to be compensated appears in the system under the condition of no subsynchronous compensation component output, wherein the control parameters comprise the channel number N of mode filtering and the gain K of each channel of the combined proportional phase shifter and the comprehensive regulator i (i =1, \8230N) and the phase shift T of each channel i (i =1, \8230; N). The channel number N of the mode filtering can be updated on line; channel gain K for combined proportional phase shifter and integrated regulator i (i =1, \8230; N) and discrete Fourier transform are just instantiated with a peak value signal of a subsynchronous signal obtained by the subsynchronous oscillation frequency identifier 3, so that a total mode control signal of the multichannel independent mode control loop 4 is matched with the output capacity of the SVG, and is generally controlled to be not more than 50% of the rated current of the SVG; the basic principle of adjusting the compensation phase of each channel is that the current/power absorbed by the SVG device is in phase with the subsynchronous oscillation current/power existing on the subsynchronous oscillation source side, or the deviation amount in the possible operation mode under various practical working conditions does not exceed 60 degrees.
And the power signal generating device 6 is used for generating a final current instruction according to a total mode control signal obtained by the multi-channel independent mode control loop and a control signal required by the direct current control of the SVG, converting the final current instruction into a power switch pulse signal and generating current and power capable of inhibiting subsynchronous oscillation.
Here, the working process of the system is described by an analog embodiment, which specifically includes the following steps:
firstly, acquiring subsynchronous oscillation current of a load side of a SVG compensation point or a system side of a public access point of a system where the SVG is located through an AD data acquisition device 1. The voltage can be collected, and the power signal can be obtained by calculating the collected voltage and current signals. The system adopts MATLAB simulation for preliminary verification, wherein the subsynchronous oscillation multi-frequency current source waveform is shown in figure 2.
It should be noted that, before entering the AD data acquisition device 1, the voltage and current signals should be subjected to proportion or phase conversion, so that the voltage and current output from the SVG or the SVG access point reach a unified magnitude; and the system current or voltage may be not only a subsynchronous component but also a component complementary to the subsynchronous frequency component.
And secondly, performing low-pass, band-pass and band-stop filtering on the acquired subsynchronous oscillation voltage, current and power signals by using the pre-combined filter 2 to filter fundamental frequency and high-frequency signal components in the voltage, the current or the power. The fundamental frequency refers to a 50Hz frequency or a frequency synchronous with a power grid by a controller, and the high frequency refers to a frequency component above 100 Hz.
It should be noted that, the selection of the pre-combining filter 2 selects one of the five implementation manners according to specific situations; and when the number of the filters is more than two, the filters are placed in cascade without strict order relation.
Where the pre-combining filter 2 is chosen to be a low-pass filter, the transfer function is equation 8,
in formula 8, G l Is the pass band gain, omega, of a low-pass filter l Is the natural angular frequency, xi, of the low-pass filter l Is a damping coefficient of a low-pass filter which is preset.
Thirdly, the discrete Fourier transform and subsynchronous oscillation frequency identifier 3 is used for performing discrete Fourier transform on the voltage, current or power signals containing subsynchronous and subsynchronous complementary frequency signals to obtain the amplitude and phase of each subsynchronous and subsynchronous complementary frequency signal, and performing subsynchronous oscillation frequency identification on the amplitude and phase signals to obtain the amplitude and frequency of each frequency subsynchronous and subsynchronous complementary frequency signal.
Specifically, the initial identification bandwidth Δ f is set to be 5Hz, and the signal amplitude threshold amplitude Ath corresponding to the preset frequency is 16.5A, namely, the system current on the 35kV side; finally, a frequency signal array Fp = [ Fp1, fp2, fp3, fp4] = [5,10,25,40], a corresponding peak signal array Ap = [ Ap1, ap2, ap3, ap4] = [50, 200,50] is obtained; the spectrogram is shown in fig. 3.
Fourth, a multi-channel independent mode control loop 4 is used, including a combined mode filter with 4 channels, a combined proportional phase shifter and a complex regulator.
The combined mode filter of each channel is used for carrying out mode filtering on voltage, current or power signals containing subsynchronous and subsynchronous complementary frequency signals of each frequency, wherein each mode filter obtains subsynchronous frequency signals of each frequency of 5Hz,10Hz,25Hz and 40Hz through the amplitude and the frequency of 4 subsynchronous components obtained by the discrete Fourier transform and the subsynchronous oscillation frequency identifier 3. Specifically, taking the combined mode filter 1 as an example to illustrate the working steps, the transfer function of the combined mode filter 1 is formula 9,
in the formula 9, G 1 For the passband gain of the mode 1 bandpass filter, the combined proportional phase shifter will perform a gain proportional adjustment, here set to 1, ω 1 Mode 1 bandpass filter center angle frequency of 10 π, ξ 1 The damping coefficient of the mode 1 band-pass filter is 0.08, and the bandwidth is 0.8Hz.
And the combined proportional phase shifter is used for compensating the phase delay of the voltage, current or power signal which is subjected to the combined mode filter and contains the subsynchronous and subsynchronous complementary frequency signals and is caused by measurement, filtering and control, amplifying the phase-compensated signal in proportion, and converting the signal into the mode control signal of the subsynchronous frequency signal of each frequency by comprehensively considering the passband gain of the mode 1 band-pass filter.
Here, the combined proportional phase shifter specifically employs a proportional phase correction filter with a filter parameter T c The time constant is compensated for phase shift, the value of which is determined based on the frequency of the variable different subsynchronous and subsynchronous complementary frequency components, a fixed sampling delay time constant, a fixed control delay time constant. For 5Hz subsynchronous signals, the filter phase shift compensates the time constant T c1 And T c2 Are all 0.0062, proportional gain K c 0.6, the final combined proportional phase shifter transfer function is equation 10,
FIG. 4 is a comparison graph of 5Hz original waveforms in multi-frequency components of the analog subsynchronous oscillation current source and waveforms obtained after processing and restoring by the control system.
And finally, the comprehensive adjuster is used for summing and limiting the mode control signals obtained by the combined proportional phase shifter to obtain the final total mode control signal.
Fourthly, using the on-line adaptive regulator 5 to start the automatic regulation of the control parameters under the condition that the SVG controller has no subsynchronous compensation component output, wherein the control parameters comprise the channel number N of the mode filtering, the channel gain K of the combined proportional phase shifter and the comprehensive regulator i (i =1, \8230N) and channel phase shift T i (i =1, \ 8230; N); under the basic principle, the working conditions do not need to be simulated, and no adjustment is carried out here.
And fifthly, generating a final current instruction and converting the final current instruction into a power switch pulse signal by using a power signal generating device 6 according to the total mode control signal obtained by the multi-channel independent mode control loop 4 and the control signal required by the direct current control of the SVG, and generating current and power capable of inhibiting subsynchronous oscillation. The power signal generating means 6 used here are standard applications and will not be described here in detail.
The system is simple in engineering realization, other engineering changes or transformation are not needed, and only the SVG controller system is upgraded to have the subsynchronous oscillation suppression function. Meanwhile, aiming at the particularity of signal characteristics such as frequency and amplitude of subsynchronous oscillation signals of different power grid systems, parameters such as proportion, phase shift, amplitude limit and the like of the combined mode filter, the combined proportion phase shifter and the comprehensive regulator need to be debugged and improved by combining site working conditions and requirements to a certain extent, so that the normal exertion of functions is ensured, and the purpose of subsynchronous suppression is achieved.
The above embodiments are merely exemplary embodiments of the present invention, and the specific structure and parameters are not intended to limit the present invention in any way. Any modification, variation and improvement made by those skilled in the art based on the principle of the present disclosure will not affect the essence of the present disclosure, and shall fall within the protection scope of the present disclosure.
Claims (6)
1. A suppression subsynchronous oscillation self-adaptive control system based on SVG comprises:
the AD data acquisition device is used for acquiring voltage, current or power signals containing subsynchronous oscillation information of SVG compensation points or a system public access point where the SVG is located;
the pre-combined filter is used for filtering the voltage, current or power signals acquired by the AD data acquisition device to obtain subsynchronous and subsynchronous complementary frequency signals in the voltage, current or power signals, and the implementation mode comprises a mode of connecting a band-pass filter and a band-stop filter in series, or a mode of connecting a plurality of band-pass filters in parallel, or a mode of using a low-pass filter; the prepositive combination filter is an optional part, and if not, the signal obtained by the AD data acquisition device directly enters the next data processing link;
the device comprises a discrete Fourier transform and subsynchronous oscillation frequency identifier, a signal processing module and a signal processing module, wherein the discrete Fourier transform and subsynchronous oscillation frequency identifier is used for performing discrete Fourier transform on voltage, current or power signals which are output by an AD data acquisition device or a pre-combination filter and contain subsynchronous and subsynchronous complementary frequency signals so as to obtain the amplitude and the phase of each subsynchronous and subsynchronous complementary frequency signal, performing subsynchronous oscillation frequency identification on the amplitude and the phase, and finally obtaining the amplitude and the frequency of each frequency subsynchronous and subsynchronous complementary frequency signal;
a multi-channel independent mode control loop including a combined mode filter having a plurality of channels, a combined proportional phase shifter, and a synthetic regulator; the combined mode filter combines the amplitude and the phase of the subsynchronous and subsynchronous complementary frequency signals of each frequency obtained by the discrete Fourier transform and the subsynchronous oscillation frequency identifier to carry out mode filtering on the voltage, current or power signals which are output by the AD data acquisition device or the preposed combined filter and contain the subsynchronous and subsynchronous complementary frequency signals of each frequency to obtain the subsynchronous and subsynchronous complementary frequency signals of each frequency; the combined proportional phase shifter is used for compensating the phase delay of the voltage, current or power signals containing the subsynchronous and subsynchronous complementary frequency signals after passing through the combined mode filter, and converting the signals after phase compensation into mode control signals of the subsynchronous and subsynchronous complementary frequency signals of each frequency after proportional amplification; the comprehensive adjuster is used for summing and amplitude limiting the control signals of all modes obtained by the combined proportional phase shifter to obtain the final control signal of the total mode;
the online self-adaptive regulator is used for starting the automatic regulation of control parameters when the SVG controller monitors that a sub-synchronous component to be compensated appears in the system under the condition that the SVG controller does not output the sub-synchronous compensation component, wherein the control parameters comprise the number of channels of mode filtering, and the gain and phase shift of each channel of the combined proportional phase shifter and the comprehensive regulator;
and the power signal generating device is used for generating a final current instruction and converting the final current instruction into a power switch pulse signal according to a total mode control signal obtained by the multi-channel independent mode control loop and a control signal required by the SVG direct-current voltage control, so as to generate current and power capable of inhibiting subsynchronous oscillation.
2. The SVG-based subsynchronous oscillation suppression adaptive control system according to claim 1, wherein the pre-combining filter is configurable for one of five implementations:
the first mode is that two filters are arranged for series combination aiming at voltage and current signals, the first filter is a second-order band-pass filter, the transfer function of the first filter is a formula 1, the second filter is a second-order fundamental wave band-stop filter, and the transfer function of the second filter is a formula 2:
in the formula 1, G 01 Is the pass band gain, omega, of a band-pass filter 01 Is the central angular frequency, xi, of the band-pass filter 01 Is the damping coefficient of the band-pass filter;
in formula 2, G 02 For fundamental pass band gain, omega, of band-stop filters 02 Is the central angular frequency, xi, of the band-stop filter 02 The damping coefficient of the band elimination filter;
in a second mode, two band-pass filters are arranged for parallel combination of voltage and current signals, the first filter and the second filter are both second-order band-pass filters, and the transfer function is formula 3:
in formula 3, G 03 Is the pass band gain, omega, of a band-pass filter 03 Is the central angular frequency, xi, of the band-pass filter 03 Is the damping coefficient of the filter;
in a third mode, 1 second-order low-pass filter is set for the voltage and current signals, and the transfer function of the filter is equation 4:
in formula 4, G 04 Is the pass band gain, omega, of a low-pass filter 04 Is the natural angular frequency, xi, of the low-pass filter 04 Is the damping coefficient of the filter;
in a fourth mode, 1 second-order band-pass filter or 1 or more band-pass and low-pass filter combinations are set for the voltage, current or power signals, the transfer function of the low-pass filter is formula 4, and the transfer function of the band-pass filter is formula 5:
in formula 5, G 05 Is the pass band gain, omega, of a band-pass filter 05 Is the central angular frequency, xi, of the band-pass filter 05 Is the damping coefficient of the filter;
and in a fifth mode, the pre-combination filter is an optional part aiming at the voltage and current signals, the acquired subsynchronous oscillation voltage, current and power signals are not processed at all under the condition, and the data signals acquired by the AD data acquisition device directly enter the next data processing link.
3. The SVG-based adaptive control system for suppressing subsynchronous oscillation according to claim 1, wherein said DFT and SSO frequency identifier can realize adaptive identification of SSO frequency of full subsynchronous bandwidth and its complementary frequency, said adaptive identification is realized by following procedures:
firstly, obtaining two arrays through discrete Fourier calculation, wherein an array F = [ F1.,. Fm ] represents the frequency of each signal of voltage, current or power, m frequency components are counted, and an array A = [ A1.,. Am ] represents the amplitude of each corresponding frequency component in a frequency signal array;
then, the subsynchronous oscillation frequency and amplitude set is identified according to the following process:
step 1, setting a subsynchronous frequency set as Fs = [ ], setting the subsynchronous frequency set as null initially, and presetting an initial bandwidth delta f to be 4-10 Hz;
step 2, setting signal amplitudes corresponding to all frequencies as Aj (j = 1.. Multidot.m), and if Aj is smaller than or equal to a preset threshold amplitude Ath, setting Aj to be 0;
step 3, with the frequency as a horizontal coordinate X and the amplitude corresponding to each frequency as a vertical coordinate Y, drawing a frequency signal array [ F1,..,. Fm ] and an amplitude signal array [ A1,..,. Am ] into a frequency spectrogram, finding out amplitude peak points corresponding to all frequency components in the spectrogram according to the frequency spectrogram, setting the frequency signal array FP = [ FP1,..., fpn ], and the corresponding peak signal array AP = [ AP1,..,. APn ], if Fpj is empty, indicating that subsynchronous oscillation of the corresponding pj-th frequency in the power grid does not occur, and turning to step 6;
step 4, if the intervals among the frequencies of the frequency signal arrays FP corresponding to all the peak points of the peak signal array AP are larger than delta f/2, the FP is the identified subsynchronous oscillation frequency array, the identification is finished, the step 6 is skipped, and otherwise the step 5 is continuously executed;
step 5, for two amplitude peak point frequencies Fpj and Fpk with the minimum frequency interval of the frequency signal array FP (where Fpj < Fpk), performing absorption and combination on the 2 frequencies, where the principle of absorption and combination is:
after merging, the new peak point frequency is:
after merging, the peak value corresponding to the new peak value point frequency is:
after the new frequency and peak value of each frequency point are updated, updating the set frequency signal array FP and the peak value signal array AP, and jumping to the step 4;
and 6, obtaining a frequency signal array FP and a peak signal array AP, namely identifying a set of subsynchronous frequency point frequencies and amplitudes thereof, setting K as the number of frequency elements in the frequency signal array FP, and if K is 0, indicating that the subsynchronous oscillation does not occur in the power grid system.
4. The SVG-based adaptive control system for suppressing subsynchronous oscillation according to claim 1, wherein said combined mode filter is a bandpass filter adjustable in both center frequency and bandwidth and having a transfer function of formula 6:
in formula 6, G i Is the pass band gain, omega, of a band-pass filter i Is the central angular frequency, xi, of the band-pass filter i For the damping coefficient of the filter, i ∈ [1,N ]]。
5. The SVG-based adaptive control system for suppressing subsynchronous oscillation according to claim 1, wherein said combined proportional phase shifter is a proportional phase correction filter having a transfer function of equation 7:
in formula 7, K c For proportional coefficients of proportional phase correction filters, T c The time constant is compensated for the phase shift of the proportional phase correction filter, and the value of the time constant is determined by the frequency of variable subsynchronous and subsynchronous complementary frequency signals, a fixed sampling delay time constant and a fixed control delay time constant;
the proportional phase correction filter is used for performing phase compensation on phase delay caused by analog quantity measurement, combined mode filtering and SVG control delay in signals containing subsynchronous and subsynchronous complementary frequency components obtained by the combined mode filter, phase delay caused by sampling and holding link of the analog quantity measurement, phase shift caused by inconsistent phase shift characteristics of different frequency components of a band-pass filter adopted in the combined mode filter, and delay of generating power signals by the SVG control link, phase deviation needs to be compensated, and the compensation target is that the phase shift at the central frequency of the mode filtering is zero and the phase shift corresponding to the acquisition of the analog quantity and the control delay time constant is compensated.
6. The SVG-based subsynchronous oscillation suppression adaptive control system according to claim 1, wherein the online adaptive regulator performs online adaptive regulation of parameters, and when the SVG controller outputs no subsynchronous compensation component, and the system is monitored to have a subsynchronous component to be compensated, the online adaptive regulator is enabled, the control parameters include the number of channels of mode filtering, and online updating can be performed; for the channel gain and the channel phase shift of the combined proportional phase shifter and the comprehensive adjuster of the multi-channel independent mode control loop, the adjustment of the channel gain is in direct proportion to the peak value signal of the sub-synchronous component to be compensated, which is obtained by the discrete Fourier transform and the sub-synchronous oscillation frequency identifier, and the total mode control signal generated by the multi-channel independent mode control loop is not more than 50% of the rated current of the SVG; the basic principle of adjusting the compensation phase of each channel is that the current/power absorbed by the SVG device is in phase with the subsynchronous oscillation current/power existing on the subsynchronous oscillation source side, or the deviation amount in the possible operation mode under various practical working conditions does not exceed 60 degrees.
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| CN105515021B (en) * | 2016-01-20 | 2017-12-19 | 清华大学 | Additional secondary/supersynchronous oscillation control method of multi-mode and control system |
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| CN108957129A (en) * | 2018-07-27 | 2018-12-07 | 中国南方电网有限责任公司 | A kind of new energy grid connection system time/supersynchronous oscillation self-adaptive monitoring method |
| CN109490668A (en) * | 2018-11-16 | 2019-03-19 | 全球能源互联网研究院有限公司 | A kind of sub-synchronous oscillation inhibits rating of set in ring test system and method |
| CN110970927B (en) * | 2019-12-16 | 2021-03-26 | 国家电网公司华北分部 | Method and system for restraining sub-synchronous oscillation of grid-side converter of direct-drive fan |
| CN114188954A (en) * | 2021-11-10 | 2022-03-15 | 华为数字能源技术有限公司 | Power oscillation suppression method, system, controller and storage medium |
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