CN114006386B - Control method and system for inhibiting grid-connected broadband oscillation of full-power converter - Google Patents
Control method and system for inhibiting grid-connected broadband oscillation of full-power converter Download PDFInfo
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- CN114006386B CN114006386B CN202111337712.9A CN202111337712A CN114006386B CN 114006386 B CN114006386 B CN 114006386B CN 202111337712 A CN202111337712 A CN 202111337712A CN 114006386 B CN114006386 B CN 114006386B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
- H02J3/241—The oscillation concerning frequency
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
- H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
Abstract
The invention discloses a control method and a system for restraining grid-connected broadband oscillation of a full-power converter, which are used for carrying out on-line monitoring on three-phase current at the alternating side of a main controller of the full-power converter, extracting the frequency of the current maximum oscillation component in real time, automatically identifying the current oscillation frequency when oscillation of any frequency occurs, and accurately adding additional damping at the current oscillation frequency through dynamic band-pass filtering so as to restrain the oscillation, so that the possible oscillation frequency does not need to be known in advance, and the design of the whole additional damping control does not depend on a specific frequency range; when the system condition changes or the oscillation frequency changes in a large range due to other reasons, the passband range of the bandpass filter also changes, so that the frequency range of the additional damping is changed pertinently, the same oscillation suppression effect is achieved, and no manual change is required to the structure and parameters of the existing additional damping control.
Description
Technical Field
The invention relates to the technical field of full-power converters, in particular to a control method and a control system for restraining grid-connected broadband oscillation of a full-power converter.
Background
The full-power converter is common power electronic equipment, can realize the bidirectional conversion of direct current and alternating current power with larger capacity, and is widely applied to the fields of wind power generation, photovoltaics, flexible direct current transmission, electric vehicle charging and the like. As shown in FIG. 1, the main controller of the full-power converter mainly comprises the following links: voltage-current sampling, phase-locked loop, dq coordinate transformation, voltage (or power) outer loop, current inner loop, pulse Width Modulation (PWM) signal generation.
The broadband oscillation problem is a type of problem which can occur in a power system, and is mainly characterized in that (1) the broadband oscillation problem is caused by new energy, power electronic equipment and a controller thereof without participation of shafting mechanical modes; (2) Because the bandwidth range of the controller of each link of the power electronic equipment is large, the typical frequency range of broadband oscillation can span from 3Hz to more than 1000 Hz. The problem of broadband oscillation suppression has become an important technical problem for restricting the development of a high-proportion new energy power system, and the problem is more complex along with the factors of the increase of the grid-connected scale of the new energy, the diversification of the running mode of a power grid and the like, so that the safe and stable running of the power system is seriously jeopardized.
The existing broadband oscillation suppression method is only suitable for a deterministic system with clear model structure, known system parameters and control parameters, single oscillation frequency and no large-range change, which can clearly appear, has poor applicability, and is difficult to meet the intelligent requirement of the intelligent power grid.
Disclosure of Invention
The invention provides a control method and a control system for restraining grid-connected broadband oscillation of a full-power converter, which are used for solving the technical problems that the existing broadband oscillation restraining method is only suitable for a deterministic system with clear model structure, known system parameters and control parameters, single oscillation frequency and no large-range change, and has poor applicability and difficulty in meeting the intelligent requirement of a smart grid.
In view of the above, the first aspect of the present invention provides a control method for suppressing grid-connected broadband oscillation of a full-power converter, including:
reading a three-phase current signal at the alternating current side of a main controller of the full-power converter, extracting the maximum oscillation component of the three-phase current signal at the alternating current side, and recording the current value, the oscillation frequency and the duration of the maximum oscillation component;
if the duration time of the single oscillation is not less than the threshold value, entering a damping control state, and judging whether the oscillation frequency is less than 100Hz;
if the oscillation frequency is less than 100Hz, setting a first filter damping ratio to construct a band-pass filter according to the synchronous/super-synchronous oscillation condition, reading the current value of the three-phase current signal at the alternating side, multiplying the band-pass filter constructed according to the first filter damping ratio by damping gain to obtain an additional modulation voltage signal, and overlapping the additional modulation voltage signal to the input end of a pulse width modulator of a full-power converter main controller;
if the oscillation frequency is not less than 100Hz, setting a second filter damping ratio to construct a band-pass filter according to the intermediate frequency/high frequency oscillation condition, reading the current value of the three-phase current signal at the alternating side, multiplying the band-pass filter constructed according to the second filter damping ratio by damping gain to obtain an additional modulation voltage signal, and overlapping the additional modulation voltage signal to the input end of a pulse width modulator of a full-power converter main controller;
and evaluating the broadband oscillation suppression effect of the full-power converter after the additional damping control is input, judging whether the oscillation component meets the requirement, if so, maintaining the current additional damping control parameter unchanged and exiting the damping control state, otherwise, performing online fine tuning on the damping gain according to the broadband oscillation suppression effect until the oscillation component is eliminated.
Optionally, the first filter damping ratio is 0.5 and the second filter damping ratio is 0.707.
Optionally, evaluating the broadband oscillation suppression effect of the full-power converter after the additional damping control is input, judging whether the oscillation component meets the requirement, if so, maintaining the current additional damping control parameter unchanged, otherwise, performing online fine tuning on the damping gain according to the broadband oscillation suppression effect until the oscillation component is eliminated, and specifically comprising the following steps:
evaluating the broadband oscillation suppression effect of the full-power converter after the additional damping control is input;
judging whether the oscillation component is eliminated;
if the broken oscillation component is eliminated and the fundamental wave component is recovered to be normal, maintaining the current additional damping control parameter unchanged and exiting the damping control state;
if the broken oscillation component is not completely eliminated, on-line fine tuning is performed to increase the damping gain, and the broadband oscillation suppression effect of the full-power converter after additional damping control is continuously evaluated;
if the broken oscillation component is eliminated but the fundamental wave component is obviously restrained, the damping gain is reduced by on-line fine adjustment, and the broadband oscillation restraining effect of the full-power converter after the additional damping control is input is continuously evaluated.
Optionally, reading an ac side three-phase current signal of the full-power converter main controller, extracting a maximum oscillation component of the ac side three-phase current signal, and recording a current value, an oscillation frequency and a duration of the maximum oscillation component, which specifically includes:
reading a three-phase current signal of the alternating-current side of the main controller of the full-power converter;
performing fast Fourier transform on the three-phase current signal at the alternating current side to extract frequency spectrum information;
and extracting the maximum oscillation component of the three-phase current signal at the alternating current side according to the frequency spectrum information, and recording the current value, the oscillation frequency and the duration of the maximum oscillation component.
The invention provides a control device for inhibiting grid-connected broadband oscillation of a full-power converter, which comprises an oscillation component extraction module, a dynamic damping gain control module, a band-pass filter construction module, an enabling control module, an AND gate logic module and an oscillation inhibition effect evaluation module, wherein the oscillation component extraction module is used for extracting a dynamic damping gain;
the input end of the oscillation component extraction module is connected with the alternating current side of the full-power converter main controller, the output end of the oscillation component extraction module is connected with the enabling control module, and the oscillation component extraction module is used for reading the three-phase current signal of the alternating current side of the full-power converter main controller, extracting the maximum oscillation component of the three-phase current signal of the alternating current side, recording the current value, the oscillation frequency and the duration of the maximum oscillation component, and sending the current value, the oscillation frequency and the duration of the maximum oscillation component to the enabling control module;
the enabling control module is used for judging whether the duration time of single oscillation is not less than a threshold value according to the received duration time, if so, entering a damping control state, sending an enabling signal with the enabling control signal of 1 and the oscillation frequency of the maximum oscillation component to the band-pass filter construction module, otherwise, keeping the current standby state, and sending an enabling signal with the enabling control signal of 0 to the AND gate logic module;
the band-pass filter construction module is used for judging whether the oscillation frequency is smaller than 100Hz, if the oscillation frequency is smaller than 100Hz, setting a first filter damping ratio according to the synchronous/super-synchronous oscillation condition to construct a band-pass filter, and if the oscillation frequency is not smaller than 100Hz, setting a second filter damping ratio according to the intermediate frequency/high frequency oscillation condition to construct the band-pass filter;
the dynamic damping gain control module is used for reading the current value of the three-phase current signal at the alternating side from the oscillation component extraction module, multiplying the current value by the damping gain after passing through a band-pass filter constructed according to the damping ratio of the first filter to obtain an additional modulation voltage signal, and superposing the additional modulation voltage signal to the AND gate logic module;
or the current value of the three-phase current signal on the alternating current side is read from the oscillation component extraction module, the additional modulation voltage signal is obtained by multiplying the current value by the damping gain after passing through a band-pass filter constructed according to the damping ratio of the second filter, and the additional modulation voltage signal is superposed to the AND gate logic module;
the AND gate logic module is used for performing AND logic operation according to the output of the enabling control module and the output of the dynamic damping gain control module, and superposing the operation result to the input end of the pulse width modulator of the full-power converter main controller;
and the oscillation suppression effect evaluation module is used for evaluating the broadband oscillation suppression effect of the full-power converter after the additional damping control is input, judging whether the oscillation component meets the requirement, if so, maintaining the current additional damping control parameter unchanged and exiting the damping control state, otherwise, performing on-line fine tuning on the damping gain through the dynamic damping gain control module according to the broadband oscillation suppression effect until the oscillation component is eliminated.
Optionally, the first filter damping ratio is 0.5 and the second filter damping ratio is 0.707.
Optionally, the oscillation suppression effect evaluation module is specifically configured to:
evaluating the broadband oscillation suppression effect of the full-power converter after the additional damping control is input;
judging whether the oscillation component is eliminated;
if the broken oscillation component is eliminated and the fundamental wave component is recovered to be normal, maintaining the current additional damping control parameter unchanged and exiting the damping control state;
if the broken oscillation component is not completely eliminated, the damping gain is increased by on-line fine adjustment of the dynamic damping gain control module, and the broadband oscillation suppression effect of the full-power converter after the additional damping control is input is continuously evaluated;
if the broken oscillation component is eliminated but the fundamental wave component is obviously inhibited, the damping gain is reduced by on-line fine adjustment of the dynamic damping gain control module, and the broadband oscillation inhibition effect of the full-power converter after the additional damping control is input is continuously evaluated.
Optionally, the oscillation component extraction module is specifically configured to:
reading a three-phase current signal of the alternating-current side of the main controller of the full-power converter;
performing fast Fourier transform on the three-phase current signal at the alternating current side to extract frequency spectrum information;
and extracting the maximum oscillation component of the three-phase current signal at the alternating current side according to the frequency spectrum information, recording the current value, the oscillation frequency and the duration of the maximum oscillation component, and sending the current value, the oscillation frequency and the duration of the maximum oscillation component to the enabling control module.
According to the technical scheme, the control method for inhibiting the grid-connected broadband oscillation of the full-power converter has the following advantages:
according to the control method for restraining the grid-connected broadband oscillation of the full-power converter, the three-phase current on the alternating current side of the main controller of the full-power converter is monitored on line, the frequency of the current maximum oscillation component is extracted in real time, when oscillation of any frequency occurs, the current oscillation frequency is automatically recognized, then the current oscillation frequency is accurately added with additional damping through dynamic band-pass filtering, so that the oscillation is restrained, therefore, the possible oscillation frequency does not need to be known in advance, and the design of the whole additional damping control does not depend on a specific frequency range; when the system conditions (such as the nearby grid structure, the scale of the grid-connected point connected converter, the control parameters of the converter and the like) change or the oscillation frequency changes in a large range due to other reasons (namely, the broadband oscillation), the passband range of the band-pass filter also changes, so that the frequency range of the additional damping is changed pertinently, the same oscillation suppression effect (namely, the self-adaption) is achieved, and no manual change is needed to the structure and the parameters of the existing additional damping control. The method solves the technical problems that the existing broadband oscillation suppression method is only suitable for a deterministic system with clear model structure, known system parameters and control parameters, single oscillation frequency and no large-range change of oscillation frequency which can appear clearly, has poor applicability and is difficult to meet the intelligent requirement of the intelligent power grid.
Drawings
For a clearer description of embodiments of the invention or of solutions according to the prior art, the figures which are used in the description of the embodiments or of the prior art will be briefly described, it being obvious that the figures in the description below are only some embodiments of the invention, from which, without the aid of inventive efforts, other relevant figures can be obtained for a person skilled in the art.
Fig. 1 is a diagram showing a structure of a main controller of a conventional full-power converter;
fig. 2 is a schematic flow chart of a control method for suppressing grid-connected broadband oscillation of a full-power converter according to the present invention;
fig. 3 is a schematic diagram of the present invention in which additional modulation voltage signals are superimposed at the three-phase voltage modulation signals at the main controller of the full power converter;
FIG. 4 is a schematic block diagram of a control method for suppressing grid-connected broadband oscillation of a full-power converter according to the present invention;
fig. 5 is a schematic structural diagram of a control system for suppressing grid-connected broadband oscillation of a full-power converter.
Detailed Description
In order to make the present invention better understood by those skilled in the art, the following description will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
For easy understanding, referring to fig. 2 to fig. 4, an embodiment of a control method for suppressing grid-connected broadband oscillation of a full-power converter is provided in the present invention, including:
and 101, reading a three-phase current signal at the alternating-current side of the main controller of the full-power converter, extracting the maximum oscillation component of the three-phase current signal at the alternating-current side, and recording the current value, the oscillation frequency and the duration of the maximum oscillation component.
As shown in fig. 3, the purpose of the present invention is to generate an additional modulation voltage signal to be superimposed on the three-phase voltage modulation signal, so as to suppress the grid-connected broadband oscillation of the full-power converter.
When the full-power converter works normally, the additional damping control is in a standby state, and in the standby state, the three-phase current signal of the alternating-current side of the main controller of the full-power converter is continuously read all the time, the maximum oscillation component of the three-phase current signal of the alternating-current side is extracted, and the current value, the oscillation frequency and the duration of the maximum oscillation component are recorded. In one embodiment, a Fast Fourier Transform (FFT) may be performed on the ac side three-phase current signal, spectrum information is extracted, a maximum oscillation component of the ac side three-phase current signal is identified according to the spectrum information, and a current value, an oscillation frequency fR, and a duration TR of the maximum oscillation component are recorded.
And 102, if the duration time of the single oscillation is not less than the threshold value, entering a damping control state, and judging whether the oscillation frequency is less than 100Hz.
If the duration of the single oscillation is less than the threshold TS, the standby state is maintained and the timer is restarted. If the duration of single oscillation is not less than the threshold TS, the damping control state is entered, and whether the oscillation frequency is less than 100Hz (i.e. twice the power frequency) is judged. Step 103 is performed if the oscillation frequency is less than 100Hz, otherwise step 104 is performed.
And 103, if the oscillation frequency is smaller than 100Hz, setting a first filter damping ratio to construct a band-pass filter according to the synchronous/super-synchronous oscillation condition, reading the current value of the three-phase current signal at the alternating side, multiplying the band-pass filter constructed according to the first filter damping ratio by damping gain to obtain an additional modulation voltage signal, and overlapping the additional modulation voltage signal to the input end of the pulse width modulator of the full-power converter main controller.
104, if the oscillation frequency is not less than 100Hz, setting a second filter damping ratio to construct a band-pass filter according to the intermediate frequency/high frequency oscillation condition, reading the current value of the three-phase current signal at the alternating side, multiplying the band-pass filter constructed according to the second filter damping ratio by damping gain Kb to obtain an additional modulation voltage signal, and overlapping the additional modulation voltage signal to the input end of the pulse width modulator of the full-power converter main controller.
The lower limit frequency f_down and the upper limit frequency f_up of the band-pass filter (the bandwidth of the band-pass filter is known) and the filter damping ratio damp can be determined from the oscillation frequency fR, so that the band-pass filter can be constructed from these parameters. If the oscillation frequency fR is less than 100Hz, the filter damping ratio damp takes a value of 0.5, and if the oscillation frequency fR is greater than or equal to 100Hz, the filter damping ratio damp takes a value of 0.707.
And 105, evaluating the broadband oscillation suppression effect of the full-power converter after the additional damping control is input, judging whether the oscillation component meets the requirement, if so, maintaining the current additional damping control parameter unchanged and exiting the damping control state, otherwise, performing online fine tuning on the damping gain Kb according to the broadband oscillation suppression effect until the oscillation component is eliminated.
In the embodiment of the invention, the damping gain Kb is not a fixed value, but a variation value which can be continuously subjected to online fine adjustment according to the real-time oscillation suppression effect. After the additional modulation voltage signal is superimposed on the input end of the pulse width modulator of the full-power converter main controller, the broadband oscillation suppression effect of the full-power converter needs to be evaluated, and whether the oscillation component meets the requirement is judged, which is as follows:
if the oscillation component is not completely eliminated, the damping gain Kb is insufficient, the damping gain Kb needs to be finely adjusted and increased, and then the oscillation suppression effect is continuously evaluated;
if the oscillation component is eliminated, but the fundamental wave component is obviously inhibited, the damping gain Kb is excessively large, fine adjustment is needed to reduce the damping gain Kb, and then the oscillation inhibition effect is continuously evaluated;
if the oscillation component is eliminated and the fundamental component is also recovered to be normal, the fine tuning of the damping gain Kb is not required, the current additional damping control parameter should be maintained unchanged, and the additional damping control state can be exited at this time to return to the standby state.
According to the control method for suppressing the grid-connected broadband oscillation of the full-power converter, which is provided by the embodiment of the invention, the three-phase current on the alternating side of the main controller of the full-power converter is monitored on line, the frequency of the current maximum oscillation component is extracted in real time, the current oscillation frequency is automatically identified when the oscillation of any frequency occurs, and then the current oscillation frequency is accurately additionally damped through dynamic band-pass filtering, so that the oscillation is suppressed, therefore, the possible oscillation frequency does not need to be known in advance, and the design of the whole additional damping control does not depend on a specific frequency range; when the system conditions (such as the nearby grid structure, the scale of the grid-connected point connected converter, the control parameters of the converter and the like) change or the oscillation frequency changes in a large range due to other reasons (namely, the broadband oscillation), the passband range of the band-pass filter also changes, so that the frequency range of the additional damping is changed pertinently, the same oscillation suppression effect (namely, the self-adaption) is achieved, and no manual change is needed to the structure and the parameters of the existing additional damping control. The method solves the technical problems that the existing broadband oscillation suppression method is only suitable for a deterministic system with clear model structure, known system parameters and control parameters, single oscillation frequency and no large-range change of oscillation frequency which can appear clearly, has poor applicability and is difficult to meet the intelligent requirement of the intelligent power grid.
In order to facilitate understanding, referring to fig. 5, the invention provides a control system for suppressing grid-connected broadband oscillation of a full-power converter, which comprises an oscillation component extraction module, a dynamic damping gain control module, a band-pass filter construction module, an enabling control module, an and gate logic module and an oscillation suppression effect evaluation module;
the input end of the oscillation component extraction module is connected with the alternating current side of the full-power converter main controller, the output end of the oscillation component extraction module is connected with the enabling control module, and the oscillation component extraction module is used for reading the three-phase current signal of the alternating current side of the full-power converter main controller, extracting the maximum oscillation component of the three-phase current signal of the alternating current side, recording the current value, the oscillation frequency and the duration of the maximum oscillation component, and sending the current value, the oscillation frequency and the duration of the maximum oscillation component to the enabling control module;
the enabling control module is used for judging whether the duration time of single oscillation is not less than a threshold value according to the received duration time, if so, entering a damping control state, sending an enabling signal with the enabling control signal of 1 and the oscillation frequency of the maximum oscillation component to the band-pass filter construction module, otherwise, keeping the current standby state, and sending an enabling signal with the enabling control signal of 0 to the AND gate logic module;
the band-pass filter construction module is used for judging whether the oscillation frequency is smaller than 100Hz, if the oscillation frequency is smaller than 100Hz, setting a first filter damping ratio according to the synchronous/super-synchronous oscillation condition to construct a band-pass filter, and if the oscillation frequency is not smaller than 100Hz, setting a second filter damping ratio according to the intermediate frequency/high frequency oscillation condition to construct the band-pass filter;
the dynamic damping gain control module is used for reading the current value of the three-phase current signal at the alternating side from the oscillation component extraction module, multiplying the current value by the damping gain after passing through a band-pass filter constructed according to the damping ratio of the first filter to obtain an additional modulation voltage signal, and superposing the additional modulation voltage signal to the AND gate logic module;
or the current value of the three-phase current signal on the alternating current side is read from the oscillation component extraction module, the additional modulation voltage signal is obtained by multiplying the current value by the damping gain after passing through a band-pass filter constructed according to the damping ratio of the second filter, and the additional modulation voltage signal is superposed to the AND gate logic module;
the AND gate logic module is used for performing AND logic operation according to the output of the enabling control module and the output of the dynamic damping gain control module, and superposing the operation result to the input end of the pulse width modulator of the full-power converter main controller;
and the oscillation suppression effect evaluation module is used for evaluating the broadband oscillation suppression effect of the full-power converter after the additional damping control is input, judging whether the oscillation component meets the requirement, if so, maintaining the current additional damping control parameter unchanged and exiting the damping control state, otherwise, performing on-line fine tuning on the damping gain through the dynamic damping gain control module according to the broadband oscillation suppression effect until the oscillation component is eliminated.
The control system for inhibiting the grid-connected broadband oscillation of the full-power converter provided by the embodiment of the invention has the working principle that:
the oscillation component extraction module reads three-phase current signals i on the alternating-current side of the main controller of the full-power converter c The maximum oscillation component of the ac side three-phase current signal is extracted (the maximum oscillation component of the ac side three-phase current signal is identified from the spectral information by performing a Fast Fourier Transform (FFT) on the ac side three-phase current signal), the current value, the oscillation frequency fR and the duration TR of the maximum oscillation component are recorded, and the current value, the oscillation frequency fR and the duration TR of the maximum oscillation component are transmitted to the enable control module.
The enabling control module judges whether the single oscillation duration TR is not less than a threshold value TS according to the received duration TR, if yes, enters a damping control state, sends an enabling signal (i.e., ea=1) with an enabling control signal of 1 and an oscillation frequency fR of the maximum oscillation component to the band-pass filter construction module, otherwise, keeps the current standby state, and sends an enabling signal (i.e., ea=0) with an enabling control signal of 0 to the and gate logic module (i.e., & in fig. 4).
The band-pass filter construction module judges whether the oscillation frequency fR is smaller than 100Hz, if the oscillation frequency fR is smaller than 100Hz, the first filter damping ratio is set according to the synchronous/super-synchronous oscillation condition to construct the band-pass filter, and if the oscillation frequency fR is not smaller than 100Hz, the second filter damping ratio is set according to the intermediate frequency/high frequency oscillation condition to construct the band-pass filter. It should be noted that, based on the oscillation frequency fR, the lower limit frequency f_down and the upper limit frequency f_up of the band-pass filter (the bandwidth of the band-pass filter is known), and the filter damping ratio damp may be determined, so that the band-pass filter may be constructed based on these parameters. If the oscillation frequency fR is less than 100Hz, the filter damping ratio damp takes a value of 0.5, and if the oscillation frequency fR is greater than or equal to 100Hz, the filter damping ratio damp takes a value of 0.707.
The dynamic damping gain control module reads the current value of the three-phase current signal at the alternating side from the oscillation component extraction module, multiplies the current value by the damping gain Kb after passing through a band-pass filter constructed according to the damping ratio of the first filter to obtain an additional modulation voltage signal, and superimposes the additional modulation voltage signal on the AND gate logic module. Or reading the current value of the three-phase current signal at the alternating current side from the oscillation component extraction module, multiplying the current value by the damping gain Kb after passing through a band-pass filter constructed according to the damping ratio of the second filter to obtain an additional modulation voltage signal, and superposing the additional modulation voltage signal on the AND gate logic module.
And the AND logic module performs AND logic operation according to the output of the enabling control module (namely Ea=1 or Ea=0) and the output of the dynamic damping gain control module, and the operation result is superposed on the input end of the pulse width modulator of the full-power converter main controller. That is, if the output of the enable control module is ea=1, the operation result of the and gate logic module is the output of the dynamic damping gain control module, and if the output of the enable control module is ea=0, no additional modulation voltage signal is superimposed on the input terminal of the pulse width modulator of the full power converter main controller.
After the additional damping control is input, the oscillation suppression effect evaluation module evaluates the broadband oscillation suppression effect of the full-power converter, judges whether the oscillation component meets the requirement, if so, maintains the current additional damping control parameter unchanged and exits the damping control state, otherwise, on-line fine-adjusts the damping gain Kb through the dynamic damping gain control module according to the broadband oscillation suppression effect until the oscillation component is eliminated. If the oscillation component is not completely eliminated, the damping gain Kb is insufficient, the damping gain Kb needs to be finely adjusted and increased, and then the oscillation suppression effect is continuously evaluated; if the oscillation component is eliminated, but the fundamental wave component is obviously inhibited, the damping gain Kb is excessively large, fine adjustment is needed to reduce the damping gain Kb, and then the oscillation inhibition effect is continuously evaluated; if the oscillation component is eliminated and the fundamental component is also recovered to be normal, the fine tuning of the damping gain Kb is not required, the current additional damping control parameter should be maintained unchanged, and the additional damping control state can be exited at this time to return to the standby state.
According to the control system for suppressing the grid-connected broadband oscillation of the full-power converter, which is provided by the embodiment of the invention, the three-phase current on the alternating side of the main controller of the full-power converter is monitored on line, the frequency of the current maximum oscillation component is extracted in real time, the current oscillation frequency is automatically identified when the oscillation of any frequency occurs, and then the current oscillation frequency is accurately additionally damped through dynamic band-pass filtering, so that the oscillation is suppressed, therefore, the possible oscillation frequency does not need to be known in advance, and the design of the whole additional damping control does not depend on a specific frequency range; when the system conditions (such as the nearby grid structure, the scale of the grid-connected point connected converter, the control parameters of the converter and the like) change or the oscillation frequency changes in a large range due to other reasons (namely, the broadband oscillation), the passband range of the band-pass filter also changes, so that the frequency range of the additional damping is changed pertinently, the same oscillation suppression effect (namely, the self-adaption) is achieved, and no manual change is needed to the structure and the parameters of the existing additional damping control. The method solves the technical problems that the existing broadband oscillation suppression method is only suitable for a deterministic system with clear model structure, known system parameters and control parameters, single oscillation frequency and no large-range change of oscillation frequency which can appear clearly, has poor applicability and is difficult to meet the intelligent requirement of the intelligent power grid.
The above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. A control method for inhibiting grid-connected broadband oscillation of a full-power converter is characterized by comprising the following steps:
reading a three-phase current signal at the alternating current side of a main controller of the full-power converter, extracting the maximum oscillation component of the three-phase current signal at the alternating current side, and recording the current value, the oscillation frequency and the duration of the maximum oscillation component;
if the duration time of the single oscillation is not less than the threshold value, entering a damping control state, and judging whether the oscillation frequency is less than 100Hz;
if the oscillation frequency is less than 100Hz, setting a first filter damping ratio to construct a band-pass filter according to the synchronous/super-synchronous oscillation condition, reading the current value of the three-phase current signal at the alternating side, multiplying the band-pass filter constructed according to the first filter damping ratio by damping gain to obtain an additional modulation voltage signal, and overlapping the additional modulation voltage signal to the input end of a pulse width modulator of a full-power converter main controller;
if the oscillation frequency is not less than 100Hz, setting a second filter damping ratio to construct a band-pass filter according to the intermediate frequency/high frequency oscillation condition, reading the current value of the three-phase current signal at the alternating side, multiplying the band-pass filter constructed according to the second filter damping ratio by damping gain to obtain an additional modulation voltage signal, and overlapping the additional modulation voltage signal to the input end of a pulse width modulator of a full-power converter main controller;
and evaluating the broadband oscillation suppression effect of the full-power converter after the additional damping control is input, judging whether the oscillation component meets the requirement, if so, maintaining the current additional damping control parameter unchanged and exiting the damping control state, otherwise, performing online fine tuning on the damping gain according to the broadband oscillation suppression effect until the oscillation component is eliminated.
2. The control method for suppressing grid-connected broadband oscillation of a full-power converter according to claim 1, wherein the damping ratio of the first filter is 0.5 and the damping ratio of the second filter is 0.707.
3. The control method for suppressing grid-connected broadband oscillation of a full-power converter according to claim 1, wherein the method is characterized by evaluating a broadband oscillation suppression effect of the full-power converter after additional damping control is input, judging whether an oscillation component meets a requirement, if yes, maintaining a current additional damping control parameter unchanged, otherwise, performing online fine tuning on damping gain according to the broadband oscillation suppression effect until the oscillation component is eliminated, and specifically comprising:
evaluating the broadband oscillation suppression effect of the full-power converter after the additional damping control is input;
judging whether the oscillation component is eliminated;
if the broken oscillation component is eliminated and the fundamental wave component is recovered to be normal, maintaining the current additional damping control parameter unchanged and exiting the damping control state;
if the broken oscillation component is not completely eliminated, on-line fine tuning is performed to increase the damping gain, and the broadband oscillation suppression effect of the full-power converter after additional damping control is continuously evaluated;
if the broken oscillation component is eliminated but the fundamental wave component is obviously restrained, the damping gain is reduced by on-line fine adjustment, and the broadband oscillation restraining effect of the full-power converter after the additional damping control is input is continuously evaluated.
4. The control method for suppressing grid-connected broadband oscillation of a full-power converter according to claim 1, wherein the method is characterized by reading a three-phase current signal at an alternating-current side of a main controller of the full-power converter, extracting a maximum oscillation component of the three-phase current signal at the alternating-current side, and recording a current value, an oscillation frequency and a duration of the maximum oscillation component, and specifically comprises the steps of:
reading a three-phase current signal of the alternating-current side of the main controller of the full-power converter;
performing fast Fourier transform on the three-phase current signal at the alternating current side to extract frequency spectrum information;
and extracting the maximum oscillation component of the three-phase current signal at the alternating current side according to the frequency spectrum information, and recording the current value, the oscillation frequency and the duration of the maximum oscillation component.
5. The control system for suppressing the grid-connected broadband oscillation of the full-power converter is characterized by comprising an oscillation component extraction module, a dynamic damping gain control module, a band-pass filter construction module, an enabling control module, an AND gate logic module and an oscillation suppression effect evaluation module;
the input end of the oscillation component extraction module is connected with the alternating current side of the full-power converter main controller, the output end of the oscillation component extraction module is connected with the enabling control module, and the oscillation component extraction module is used for reading the three-phase current signal of the alternating current side of the full-power converter main controller, extracting the maximum oscillation component of the three-phase current signal of the alternating current side, recording the current value, the oscillation frequency and the duration of the maximum oscillation component, and sending the current value, the oscillation frequency and the duration of the maximum oscillation component to the enabling control module;
the enabling control module is used for judging whether the duration time of single oscillation is not less than a threshold value according to the received duration time, if so, entering a damping control state, sending an enabling signal with the enabling control signal of 1 and the oscillation frequency of the maximum oscillation component to the band-pass filter construction module, otherwise, keeping the current standby state, and sending an enabling signal with the enabling control signal of 0 to the AND gate logic module;
the band-pass filter construction module is used for judging whether the oscillation frequency is smaller than 100Hz, if the oscillation frequency is smaller than 100Hz, setting a first filter damping ratio according to the synchronous/super-synchronous oscillation condition to construct a band-pass filter, and if the oscillation frequency is not smaller than 100Hz, setting a second filter damping ratio according to the intermediate frequency/high frequency oscillation condition to construct the band-pass filter;
the dynamic damping gain control module is used for reading the current value of the three-phase current signal at the alternating side from the oscillation component extraction module, multiplying the current value by the damping gain after passing through a band-pass filter constructed according to the damping ratio of the first filter to obtain an additional modulation voltage signal, and superposing the additional modulation voltage signal to the AND gate logic module;
or the current value of the three-phase current signal on the alternating current side is read from the oscillation component extraction module, the additional modulation voltage signal is obtained by multiplying the current value by the damping gain after passing through a band-pass filter constructed according to the damping ratio of the second filter, and the additional modulation voltage signal is superposed to the AND gate logic module;
the AND gate logic module is used for performing AND logic operation according to the output of the enabling control module and the output of the dynamic damping gain control module, and superposing the operation result to the input end of the pulse width modulator of the full-power converter main controller;
and the oscillation suppression effect evaluation module is used for evaluating the broadband oscillation suppression effect of the full-power converter after the additional damping control is input, judging whether the oscillation component meets the requirement, if so, maintaining the current additional damping control parameter unchanged and exiting the damping control state, otherwise, performing on-line fine tuning on the damping gain through the dynamic damping gain control module according to the broadband oscillation suppression effect until the oscillation component is eliminated.
6. The control system for suppressing grid-tied broadband oscillation of a full power converter as defined in claim 5, wherein the first filter damping ratio is 0.5 and the second filter damping ratio is 0.707.
7. The control system for suppressing grid-connected broadband oscillation of a full-power converter according to claim 5, wherein the oscillation suppression effect evaluation module is specifically configured to:
evaluating the broadband oscillation suppression effect of the full-power converter after the additional damping control is input;
judging whether the oscillation component is eliminated;
if the broken oscillation component is eliminated and the fundamental wave component is recovered to be normal, maintaining the current additional damping control parameter unchanged and exiting the damping control state;
if the broken oscillation component is not completely eliminated, the damping gain is increased by on-line fine adjustment of the dynamic damping gain control module, and the broadband oscillation suppression effect of the full-power converter after the additional damping control is input is continuously evaluated;
if the broken oscillation component is eliminated but the fundamental wave component is obviously inhibited, the damping gain is reduced by on-line fine adjustment of the dynamic damping gain control module, and the broadband oscillation inhibition effect of the full-power converter after the additional damping control is input is continuously evaluated.
8. The control system for suppressing grid-connected broadband oscillation of a full-power converter according to claim 5, wherein the oscillation component extraction module is specifically configured to:
reading a three-phase current signal of the alternating-current side of the main controller of the full-power converter;
performing fast Fourier transform on the three-phase current signal at the alternating current side to extract frequency spectrum information;
and extracting the maximum oscillation component of the three-phase current signal at the alternating current side according to the frequency spectrum information, recording the current value, the oscillation frequency and the duration of the maximum oscillation component, and sending the current value, the oscillation frequency and the duration of the maximum oscillation component to the enabling control module.
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| EP3322060A1 (en) * | 2016-11-14 | 2018-05-16 | Nordex Energy GmbH | Method of damping electromechanical oscillations on a power system |
| CN112436537A (en) * | 2020-11-11 | 2021-03-02 | 许继电气股份有限公司 | Broadband oscillation suppression method for flexible direct current sending system of offshore wind farm |
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| EP3322060A1 (en) * | 2016-11-14 | 2018-05-16 | Nordex Energy GmbH | Method of damping electromechanical oscillations on a power system |
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| CN113258592A (en) * | 2021-06-25 | 2021-08-13 | 广东电网有限责任公司 | Additional damping suppression system and method for sub-synchronous and super-synchronous oscillation of offshore wind power |
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