A grid-connected converter multi-band control device and method for suppressing broadband oscillation

Abstract

The application provides a multi-frequency-band control device and method for suppressing wide-frequency oscillation of a grid-connected converter, which comprises a cascade multi-scale controller and a wide-frequency oscillation controller. The application performs collaborative damping control on different controllers of the grid-connected converter by adjusting the software control of the grid-connected converter. By collecting oscillation signals of different frequency bands, the oscillation frequency bands are divided into low-frequency bands, medium-frequency bands and high-frequency bands, and damping controllers are arranged in different frequency bands to suppress the wide-frequency oscillation of the grid-connected converter. The wide-frequency oscillation caused by the interaction between the grid-connected converter and the power grid and the interaction between converters under different grid strengths and different operating points can be suppressed, and the stability of the single / multi-machine system of the grid-connected converter is comprehensively improved. Moreover, the method is suitable for wind power grid-connected converters, photovoltaic grid-connected converters, flexible DC power transmission converters, flexible AC system converters and other devices and scenes.

Description

Technical Field

[0001] The present invention relates to the field of grid-connected converter control, and in particular to a multi-band control device and method for a grid-connected converter for suppressing broadband oscillation. Background Art

[0002] In recent years, with the gradual advancement of national strategic demands such as the large-scale development of new energy, the optimization of resource allocation on a larger scale, and the improvement of load energy efficiency, traditional power systems, dominated by electromagnetic conversion equipment such as synchronous machines, transformers, and motors, have gradually shifted to power electronics based on semiconductor devices. It is foreseeable that power electronics will be a key trend in the development of modern power systems. Grid-connected converters serve as key power interface and conversion units in power electronics systems, enabling energy exchange and regulation between generation, transmission, distribution, consumption, and storage.

[0003] However, when large-scale grid-connected converters are connected to the power system, they can cause broadband oscillations, both on electromechanical and electromagnetic timescales. For example, during testing of a STATCOM at a wind farm, oscillations occurred during constant reactive power operation, leading to abnormal 110 kV oscillations. The voltage waveform contained an 84.6 Hz waveform with an amplitude of 6.3% of the fundamental frequency. Over 100 irregular oscillations occurred in one region, with a wide frequency range of 7 to 85 Hz. Some operational flexible direct current (DC) projects have also experienced medium- and high-frequency oscillations (100 Hz to 1 kHz is considered medium frequency, and 1 kHz and above is considered high frequency). For example, one flexible direct current (DC) project experienced high-frequency oscillations around 1270 Hz, while another project experienced medium- and high-frequency oscillations of 700 Hz and 1800 Hz. Broadband oscillations in grid-connected converters can pose significant risks to equipment and may further cause large-scale power grid accidents, resulting in severe economic losses. Therefore, there is an urgent need to develop a reliable and applicable method for suppressing broadband oscillations in grid-connected converters.

[0004] At present, many invention patents also involve measures to suppress broadband oscillations in new energy grid-connected systems. For example, patent CN202310260639.2 calculates the impedance and impedance phase angle, aggregate impedance and aggregate impedance phase angle of each branch of the new energy station at the sub- / supersynchronous oscillation frequency, calculates the projection length of the impedance of each branch in the effective set of emergency control measures in the direction of the aggregate impedance, and cuts off the corresponding branches in turn until the oscillation is suppressed. The method suppresses oscillations by cutting off the corresponding power generation equipment and lines, resulting in a waste of electricity, failing to fully utilize new energy power generation, and is not conducive to improving the penetration rate of new energy. Patent CN202310416869.3 inputs the actual frequency and amplitude of broadband oscillations generated by the new energy grid-connected system into the classifier model, so that the classifier model outputs a broadband oscillation suppression strategy based on the classification conditions; the broadband oscillation suppression strategy is input into the first neural network, and the broadband oscillation suppression parameters are output, and the broadband oscillation of the new energy is suppressed by optimizing the broadband oscillation suppression parameters. The method attempts to suppress broadband oscillations by adaptively optimizing control parameters. However, this variable parameter control strategy has a slow response speed, and it is difficult to adapt to oscillation suppression in different frequency bands through a single controller.

[0005] Therefore, early patents often ignored the control characteristics of the mutual coordination of multi-scale control loops of grid-connected converters, and did not discover suitable multi-time-scale controller multi-band collaborative control devices and methods aimed at suppressing broadband oscillations. Summary of the Invention

[0006] The purpose of the present invention is to design a multi-band collaborative control device and method for a grid-connected converter for suppressing broadband oscillations. It is intended to improve the software control method of the grid-connected converter, perform collaborative damping control on different controllers of the grid-connected converter, and suppress the broadband oscillations of the grid-connected converter from the low frequency band, medium frequency band and high frequency band.

[0007] A multi-band control device for a grid-connected converter for suppressing broadband oscillations, characterized by comprising a cascaded multi-scale controller and a broadband oscillation controller;

[0008] The broadband oscillator controller is used to receive the voltage signal u collected by the grid connection point PCC. abc , current signal i abc , the voltage signal u abc , current signal i abc After instantaneous active power calculation, oscillation frequency detection, oscillation signal decomposition and multi-band damper filtering and integration processing, low-frequency oscillation signal, medium-frequency oscillation signal and high-frequency oscillation signal are obtained;

[0009] The cascade multi-scale controller is connected to the wide-band oscillation controller and the three-phase full-bridge inverter circuit, and is used to respectively suppress the input low-frequency oscillation signal, the medium-frequency oscillation signal, and the high-frequency oscillation signal in the low frequency band, the medium frequency band, and the high frequency band to obtain a first modulated voltage d-axis component signal, and obtain a second modulated voltage d-axis component signal based on the converter terminal voltage signal and the converter terminal voltage reference value signal. The first modulated voltage d-axis component signal and the second modulated voltage d-axis component signal are subjected to coordinate transformation and modulation calculation to obtain a PWM signal, and the PWM signal is input into the three-phase full-bridge inverter circuit for control.

[0010] Furthermore, the broadband oscillation suppressor includes an instantaneous active power calculator, an oscillation frequency detector, an oscillation frequency band selector, and a multi-band damper;

[0011] The instantaneous active power calculator is used to convert the voltage signal uabc and the current signal iabc collected by the grid connection point PCC from a three-phase rotating coordinate system to a two-phase coordinate system to calculate the instantaneous active power signal output by the converter;

[0012] The oscillation frequency detector is used to receive the instantaneous active power signal output by the converter, calculate the oscillation frequency and obtain an oscillation signal containing different frequency bands;

[0013] The oscillation frequency band selector is used to receive the oscillation signal and the instantaneous active power signal, and decompose the oscillation signal into an original low-frequency band signal, an original mid-frequency band signal, and an original high-frequency band signal according to different frequency band ranges;

[0014] The multi-band damper is used to receive the original low-frequency band signal, the original medium-frequency band signal and the original high-frequency band signal, and obtain the low-frequency oscillation signal, the medium-frequency oscillation signal and the high-frequency oscillation signal respectively through filtering and integration processing by the multi-band damper.

[0015] Furthermore, the multi-band damping controller includes a low-pass filter, a first proportional device, a first lead-lag module, a band-pass filter, a second proportional device, a second lead-lag module, a high-pass filter, a third proportional device, and a second lead-lag module;

[0016] The low-pass filter is used to perform low-pass filtering on the original low-frequency band signal to obtain a filtered low-frequency band signal;

[0017] The first proportional device is used to calculate the proportion of the filtered low-frequency signal to obtain a conditioned low-frequency signal;

[0018] The first lead-lag module is used to perform lead-lag adjustment on the conditioned low-frequency band signal to obtain a low-frequency oscillation signal, which is subsequently superimposed on a reference instruction for DC voltage or active power control;

[0019] The bandpass filter is used to perform bandpass filtering on the intermediate frequency band signal to obtain a filtered intermediate frequency band signal;

[0020] The second proportional device is used to perform proportional calculation on the filtered intermediate frequency band signal to obtain a conditioned low frequency band signal;

[0021] The second lead-lag module is used to perform lead-lag adjustment on the conditioned low-frequency band signal to obtain a medium-frequency oscillation signal, which is subsequently superimposed on the reference instruction of the d-axis current controller;

[0022] The high-pass filter is used to perform high-pass filtering on the high-frequency band signal to obtain a filtered high-frequency band signal;

[0023] The third proportional device is used to perform proportional calculation on the filtered high-frequency band signal to obtain a conditioned high-frequency band signal;

[0024] The third lead-lag module is used to perform lead-lag adjustment on the conditioned high-frequency band signal to obtain a high-frequency oscillation signal, which is subsequently input into the feedforward control.

[0025] Furthermore, the cascade multi-scale controller includes an AC voltage controller, a q-axis current controller, a q-axis feedforward controller, a low-frequency suppressor, a mid-frequency suppressor, a high-frequency suppressor, and a modulator;

[0026] The low-frequency band suppressor is used to obtain a d-axis current reference value signal by performing a DC voltage superposition and proportional integral calculation on the input low-frequency oscillation signal;

[0027] The intermediate frequency suppressor is used to calculate the intermediate frequency oscillation signal and the d-axis current reference value signal through the proportional integral calculation of the d-axis current controller to obtain the internal potential signal of the d-axis converter;

[0028] A high-frequency band suppressor is used to calculate the high-frequency oscillation signal and the potential signal inside the d-axis converter to obtain a first modulation voltage d-axis component signal;

[0029] The AC voltage controller is used to subtract the converter terminal voltage signal from the converter terminal voltage reference value signal to obtain a terminal voltage error signal, and then perform proportional-integral calculation on the terminal voltage error signal to obtain a q-axis current reference signal and transmit it to the q-axis current controller;

[0030] The q-axis current controller is used to obtain a q-axis current error signal by subtracting the q-axis current reference signal from the q-axis current signal, and then calculate the q-axis current error signal proportionally and integrally to obtain a q-axis converter internal potential signal, which is then transmitted to the q-axis feedforward controller;

[0031] The q-axis feedforward controller is used to perform a feedforward control algorithm calculation on the potential signal inside the d-axis converter and the d and q components of the converter terminal voltage to generate a second modulation voltage d-axis component signal. The second modulation voltage d-axis component signal and the first modulation voltage d-axis component signal are jointly input into the modulator for coordinate conversion and modulation calculation to obtain a PWM signal for controlling the three-phase full-bridge inverter circuit.

[0032] Furthermore, the low-frequency band suppressor includes a subtractor, an adder, and a DC voltage PI controller;

[0033] The subtractor is used to subtract the DC voltage reference signal from the DC voltage signal to obtain a voltage error signal;

[0034] The adder is used to add the voltage error signal transmitted by the subtractor and the low-frequency oscillation signal to obtain a low-frequency error compensation signal;

[0035] The DC voltage PI controller is used to perform proportional integral calculation and processing on the low-frequency error compensation signal to obtain a d-axis current reference value signal.

[0036] Furthermore, the intermediate frequency band suppressor includes a subtractor, an adder, and a d-axis current PI controller;

[0037] The subtractor is used to subtract the d-axis current reference value signal from the d-axis current signal to obtain a d-axis current error signal;

[0038] The adder is used to add the d-axis current error signal transmitted by the subtractor and the intermediate frequency oscillation signal to obtain an intermediate frequency error compensation signal;

[0039] The d-axis current PI controller is used to perform proportional-integral calculation and processing on the intermediate frequency error compensation signal to obtain the internal potential signal of the d-axis converter.

[0040] Furthermore, the high-frequency band suppressor includes a subtractor and an adder;

[0041] The adder is used to add the signal to the voltage signal in the d-axis of the converter to obtain a d-axis voltage composite signal;

[0042] The adder is used to add the d-axis voltage synthesis signal transmitted from the previous stage and the high-frequency oscillation signal to obtain a first modulation voltage d-axis component signal.

[0043] A multi-band control method for a grid-connected converter for suppressing broadband oscillations is implemented using the above-mentioned device, and the method comprises:

[0044] The broadband oscillation controller receives the voltage signal uabc and the current signal iabc collected by the grid connection point PCC, and processes the voltage signal uabc and the current signal iabc through instantaneous active power calculation, oscillation frequency detection, oscillation signal decomposition, and multi-band damper filtering and integration to obtain a low-frequency oscillation signal, a medium-frequency oscillation signal, and a high-frequency oscillation signal;

[0045] The cascade multi-scale controller suppresses the input low-frequency oscillation signal, medium-frequency oscillation signal and high-frequency oscillation signal in the low-frequency band, medium-frequency band and high-frequency band respectively to obtain a first modulated voltage d-axis component signal, and obtains a second modulated voltage d-axis component signal based on the converter terminal voltage signal and the converter terminal voltage reference value signal. The first modulated voltage d-axis component signal and the second modulated voltage d-axis component signal are subjected to coordinate transformation and modulation calculation to obtain a PWM signal, and the PWM signal is input into the three-phase full-bridge inverter circuit for control.

[0046] The present invention designs a multi-band collaborative control device and method for a grid-connected converter for suppressing broadband oscillations. By adjusting the software control method of the grid-connected converter, collaborative damping control is performed on different controllers of the grid-connected converter. By collecting oscillation signals of different frequency bands, the oscillation frequency bands are divided into low frequency bands, medium frequency bands and high frequency bands, and damping controllers are set in different frequency bands to suppress the broadband oscillations of the grid-connected converter. It can suppress broadband oscillations caused by the interaction between the grid-connected converter and the grid, and the interaction between converters under different grid strengths and different working points, and comprehensively improve the stability of the grid-connected converter single-machine / multi-machine system. In addition, this method is applicable to equipment and scenarios such as wind power grid-connected converters, photovoltaic grid-connected converters, flexible direct current transmission converters, and flexible alternating current system converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a topological diagram of a grid-connected converter connected to an AC power grid according to an embodiment of the present invention;

[0048] Figure 2 This is a structural diagram of a broadband oscillation suppressor according to an embodiment of the present invention;

[0049] Figure 3 1 is a structural diagram of a multi-band damper according to an embodiment of the present invention;

[0050] Figure 4 is a structural diagram of a cascaded multi-scale controller according to an embodiment of the present invention;

[0051] Figure 5 is a structural diagram of a low-frequency band suppressor according to an embodiment of the present invention;

[0052] Figure 6 is a structural diagram of a frequency band suppressor according to an embodiment of the present invention;

[0053] Figure 7This is a structural diagram of a high-frequency band suppressor according to an embodiment of the present invention;

[0054] Figure 8 This is a diagram showing the broadband oscillation suppression effect of an embodiment of the present invention. DETAILED DESCRIPTION

[0055] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0056] Power electronic converters, such as wind power and photovoltaic power generation, have dynamic characteristics of multi-time scale cascade sequence. Their large-scale access to the power system will bring new stability problems to the power grid. On the one hand, the interaction between power electronic converters on the electromagnetic time scale will lead to electromagnetic time scale oscillations; on the other hand, the interaction between power electronic converters (such as wind power converters) and synchronous machines will lead to electromechanical time scale oscillations. Therefore, the large-scale access of power electronic converters can cause multi-scale broadband oscillations from the electromagnetic time scale to the electromechanical time scale. The present invention is a multi-band collaborative control device and method for grid-connected converters for suppressing broadband oscillations. It is intended to improve the software control of the grid-connected converter, perform collaborative damping control on different controllers of the grid-connected converter, and suppress the broadband oscillation of the grid-connected converter from the low frequency band, the medium frequency band, and the high frequency band.

[0057] Figure 1 This is a topological diagram of a grid-connected converter connected to an AC power grid, which consists of a three-phase full-bridge inverter circuit 1, a DC power supply 2, a filter inductor 3, a filter capacitor 4, a grid equivalent impedance 5, an AC power grid 6, a cascaded multi-scale controller 7, a wide-band oscillation controller 8, and the like.

[0058] The DC power supply 2, the three-phase full-bridge inverter circuit 1, the filter inductor 3 and the filter capacitor 4 are connected in sequence. The node between the filter inductor 3 and the filter capacitor 4 serves as the grid connection point PCC, which is connected to the AC grid 6 through the grid equivalent impedance 5.

[0059] The multi-band control device for a grid-connected converter for suppressing broadband oscillations according to an embodiment of the present invention comprises a cascaded multi-scale controller 7 and a broadband oscillation controller 8;

[0060] The broadband oscillator controller 8 is used to receive the voltage signal u collected by the grid connection point PCC. abc , current signal i abc , the voltage signal u abc , current signal i abc After instantaneous active power calculation, oscillation frequency detection, oscillation signal decomposition, and multi-band damper filtering and integration processing, a low-frequency oscillation signal 8400, a medium-frequency oscillation signal 8401, and a high-frequency oscillation signal 8402 are obtained;

[0061] The cascade multi-scale controller 7 is connected to the wide-band oscillation controller 8 and the three-phase full-bridge inverter circuit 1, and is used to respectively subject the input low-frequency oscillation signal 8400, the medium-frequency oscillation signal 8401, and the high-frequency oscillation signal 8402 to low-frequency band suppression, medium-frequency band suppression, and high-frequency band suppression to obtain a first modulated voltage d-axis component signal 760, and to obtain a second modulated voltage d-axis component signal 730 based on the converter terminal voltage signal and the converter terminal voltage reference value signal. The first modulated voltage d-axis component signal 760 and the second modulated voltage d-axis component signal 730 are input into the modulator 77, and a PWM signal 78 is obtained through coordinate conversion and modulation calculation. The PWM signal 78 is input into the three-phase full-bridge inverter circuit for control.

[0062] Figure 2 3 is a structural diagram of a broadband oscillation suppressor 8 , which includes an instantaneous active power calculator 81 , an oscillation frequency detector 82 , an oscillation frequency band selector 83 , and a multi-band damper 84 .

[0063] The instantaneous active power calculator 81 is used to convert the voltage signal u collected by the grid connection point PCC into abc , current signal i abc Convert the three-phase rotating coordinate system into a two-phase coordinate system to calculate the instantaneous active power signal output by the converter 810;

[0064] The oscillation frequency detector 82 is used to receive the instantaneous active power signal 810 output by the converter, calculate the oscillation frequency and obtain an oscillation signal 820 containing different frequency bands;

[0065] The oscillation frequency band selector 83 is used to receive the oscillation signal 820 and the instantaneous active power signal 810, and decompose the oscillation signal into an original low-frequency band signal 830, an original mid-frequency band signal 831, and an original high-frequency band signal 832 according to different frequency band ranges;

[0066] The multi-band damper 84 is used to receive the original low-frequency band signal 830, the original intermediate-frequency band signal 831 and the original high-frequency band signal 832, and obtain a low-frequency oscillation signal 8400, an intermediate-frequency oscillation signal 8401 and a high-frequency oscillation signal 8402 through filtering and integration processing by the multi-band damper.

[0067] Figure 3 84 is a structural diagram of the multi-band damping controller 84. The multi-band damping controller 84 includes a low-pass filter 841, a first proportional device 842, a first lead-lag module 843, a band-pass filter 844, a second proportional device 845, a second lead-lag module 846, a high-pass filter 847, a third proportional device 848, and a second lead-lag module 849.

[0068] The low-pass filter 841 is used to perform low-pass filtering on the original low-frequency signal 830 to obtain a filtered low-frequency signal 8411;

[0069] The first scaler 842 is configured to perform proportional calculation on the filtered low-frequency signal 8411 to obtain a conditioned low-frequency signal 8421;

[0070] The first lead-lag module 843 is used to perform lead-lag adjustment on the conditioned low-frequency band signal 8421 to obtain a low-frequency oscillation signal 8400, which is subsequently superimposed on a reference instruction for DC voltage or active power control.

[0071] The bandpass filter 844 is used to perform bandpass filtering on the intermediate frequency signal 831 to obtain a filtered intermediate frequency signal 8441;

[0072] The second scaler 845 is configured to perform proportional calculation on the filtered intermediate frequency signal 8441 to obtain a conditioned low frequency signal 8451;

[0073] The second lead-lag module 846 is used to perform lead-lag adjustment on the conditioned low-frequency signal 8451 to obtain a medium-frequency oscillation signal 8401, which is subsequently superimposed on the reference instruction of the d-axis current controller.

[0074] The high-pass filter 847 is used to perform high-pass filtering on the high-frequency band signal 832 to obtain a filtered high-frequency band signal 8471;

[0075] The third scaler 848 is configured to perform proportional calculation on the filtered high-band signal 8471 to obtain a conditioned high-band signal 8481;

[0076] The third lead-lag module 849 is used to perform lead-lag adjustment on the conditioned high-frequency band signal 8481 to obtain a high-frequency oscillation signal 8402, which is subsequently input into the feedforward control.

[0077] Figure 4 This is a structural diagram of the cascaded multi-scale controller 7. The cascaded multi-scale controller 7 includes an AC voltage controller 71, a q-axis current controller 72, a q-axis feedforward controller 73, a low-frequency band suppressor 74, a mid-frequency band suppressor 75, a high-frequency band suppressor 76, and a modulator 77.

[0078] The low-frequency suppressor 74 is used to obtain a d-axis current reference value signal 740 by performing a DC voltage superposition and proportional integral calculation on the input low-frequency oscillation signal 8400;

[0079] The intermediate frequency suppressor 75 is used to calculate the intermediate frequency oscillation signal 8401 and the d-axis current reference value signal 740 through a d-axis current controller proportional integral calculation to obtain the d-axis converter internal potential signal 750;

[0080] The high frequency band suppressor 76 is used to calculate the high frequency oscillation signal 8402 and the potential signal 750 inside the d-axis converter to obtain a first modulation voltage d-axis component signal 760 .

[0081] The AC voltage controller 71 is used to subtract the converter terminal voltage signal from the converter terminal voltage reference value signal to obtain a terminal voltage error signal, and then perform proportional integral calculation on the terminal voltage error signal to obtain a q-axis current reference signal 710 which is transmitted to the q-axis current controller 72 .

[0082] The q-axis current controller 72 is used to subtract the q-axis current reference signal 710 from the q-axis current signal to obtain a q-axis current error signal, and then perform proportional integral calculation of the q-axis current error signal to obtain a q-axis converter internal potential signal 720 which is transmitted to the q-axis feedforward controller 73.

[0083] The q-axis feedforward controller 73 is used to perform a feedforward control algorithm calculation on the d-axis converter internal potential signal 720 and the converter terminal voltage d and q components to generate a second modulation voltage d-axis component signal 730. The second modulation voltage d-axis component signal 730 and the first modulation voltage d-axis component signal 760 are jointly input into the modulator 77 for coordinate conversion and modulation calculation to obtain a PWM signal 78 for controlling the three-phase full-bridge inverter circuit.

[0084] Figure 5 7 is a structural diagram of the low-band suppressor 74 , which includes a subtractor 741 , an adder 742 , and a DC voltage PI controller 743 .

[0085] The subtractor 741 is used to subtract the DC voltage reference signal from the DC voltage signal to obtain a voltage error signal 7410;

[0086] The adder 742 is used to add the voltage error signal 7410 transmitted by the subtractor and the low-frequency oscillation signal 8400 to obtain a low-frequency error compensation signal 7420;

[0087] The DC voltage PI controller 743 is used to perform proportional-integral calculation and processing on the low-frequency error compensation signal 7420 to obtain the d-axis current reference value signal 740 .

[0088] Figure 6 7 is a structural diagram of the intermediate frequency band suppressor 75 , which includes a subtractor 751 , an adder 752 , and a d-axis current PI controller 753 .

[0089] The subtractor 751 is configured to subtract the d-axis current reference signal 740 from the d-axis current signal to obtain a d-axis current error signal 7510 ;

[0090] The adder 752 is used to add the d-axis current error signal transmitted by the subtractor and the intermediate frequency oscillation signal 8401 to obtain an intermediate frequency error compensation signal 7520;

[0091] The d-axis current PI controller 753 is used to perform proportional-integral calculation and processing on the intermediate frequency error compensation signal 7520 to obtain the d-axis converter internal potential signal 750 .

[0092] Figure 7 7 is a structural diagram of the high-band suppressor 76 . The high-band suppressor 76 includes a subtractor 761 and an adder 762 .

[0093] The adder 761 is used to add the signal 750 and the voltage signal in the d-axis of the converter to obtain a d-axis voltage composite signal 7610;

[0094] The adder 762 is used to add the d-axis voltage synthesis signal 7610 transmitted from the previous stage and the high-frequency oscillation signal 8402 to obtain the first modulated voltage d-axis component signal 760.

[0095] Based on the above conception, the present invention discloses a power electronic converter control device and method for suppressing broadband oscillations. On the one hand, the access of the grid-type converter increases the grid strength of the power system, provides inertia and frequency support for the power system, and is conducive to reducing the instability of the power system operation caused by the access of large-scale wind and solar energy bases, thereby improving the stability and reliability of the power system operation; on the other hand, the introduction of a broadband oscillation controller into the conventional control device and method can adjust and process oscillation signals of different frequency bands, effectively suppress the broadband oscillation of the power system, and improve the safety and stability of the grid-connected operation of the converter.

[0096] The present invention designs a multi-band cooperative control device and method for a grid-connected converter for suppressing broadband oscillations. By adjusting the software control mode of the grid-connected converter, cooperative damping control is performed on different controllers of the grid-connected converter to suppress the broadband oscillations of the grid-connected converter from the low frequency band, the medium frequency band and the high frequency band. A wind power grid-connected system is built in MATLAB / simulink in which a wind farm is connected to an AC power grid with a short-circuit ratio of 1.2. A small interference is set at the 2nd second, and the active power response of the wind farm is observed before and after the wind power converter is added with the multi-band cooperative control device and method for suppressing broadband oscillations of the grid-connected converter described in the present invention, as shown in FIG. Figure 8 Without multi-band coordinated control, the wind farm experienced broadband oscillation instability. With multi-band coordinated control, the wind farm maintained good stability under small disturbances and could operate normally. Therefore, this patent has been implemented with good results.

[0097] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A multi-band control device for a grid-connected converter for suppressing broadband oscillations, characterized by: Including cascade multi-scale controller and broadband oscillation controller; The broadband oscillator controller is used to receive the voltage signal u collected by the grid connection point PCC. abc , current signal i abc , the voltage signal u abc , current signal i abc After instantaneous active power calculation, oscillation frequency detection, oscillation signal decomposition and multi-band damper filtering and integration processing, low-frequency oscillation signal, medium-frequency oscillation signal and high-frequency oscillation signal are obtained; The cascade multi-scale controller is connected to the wide-band oscillation controller and the three-phase full-bridge inverter circuit, and is used to respectively suppress the input low-frequency oscillation signal, the medium-frequency oscillation signal, and the high-frequency oscillation signal in the low frequency band, the medium frequency band, and the high frequency band to obtain a first modulated voltage d-axis component signal, and to obtain a second modulated voltage d-axis component signal based on the converter terminal voltage signal and the converter terminal voltage reference value signal. The first modulated voltage d-axis component signal and the second modulated voltage d-axis component signal are subjected to coordinate transformation and modulation calculation to obtain a PWM signal, and the PWM signal is input into the three-phase full-bridge inverter circuit for control; The cascade multi-scale controller includes an AC voltage controller, a q-axis current controller, a q-axis feedforward controller, a low-frequency suppressor, a mid-frequency suppressor, a high-frequency suppressor, and a modulator; The low-frequency band suppressor is used to obtain a d-axis current reference value signal by performing a DC voltage superposition and proportional integral calculation on the input low-frequency oscillation signal; The intermediate frequency suppressor is used to calculate the intermediate frequency oscillation signal and the d-axis current reference value signal through the proportional integral calculation of the d-axis current controller to obtain the internal potential signal of the d-axis converter; A high-frequency band suppressor is used to calculate the high-frequency oscillation signal and the potential signal inside the d-axis converter to obtain a first modulation voltage d-axis component signal; The AC voltage controller is used to subtract the converter terminal voltage signal from the converter terminal voltage reference value signal to obtain a terminal voltage error signal, and then perform proportional-integral calculation on the terminal voltage error signal to obtain a q-axis current reference signal and transmit it to the q-axis current controller; The q-axis current controller is used to obtain a q-axis current error signal by subtracting the q-axis current reference signal from the q-axis current signal, and then calculate the q-axis current error signal proportionally and integrally to obtain a q-axis converter internal potential signal, which is then transmitted to the q-axis feedforward controller; The q-axis feedforward controller is used to perform a feedforward control algorithm calculation on the potential signal inside the d-axis converter and the d and q components of the converter terminal voltage to generate a second modulation voltage d-axis component signal. The second modulation voltage d-axis component signal and the first modulation voltage d-axis component signal are jointly input into the modulator for coordinate conversion and modulation calculation to obtain a PWM signal for controlling the three-phase full-bridge inverter circuit.

2. The multi-band control device for a grid-connected converter for suppressing broadband oscillation according to claim 1, characterized in that: The broadband oscillation suppressor includes an instantaneous active power calculator, an oscillation frequency detector, an oscillation frequency band selector, and a multi-band damper; The instantaneous active power calculator is used to convert the voltage signal uabc and the current signal iabc collected by the grid connection point PCC from a three-phase rotating coordinate system to a two-phase coordinate system to calculate the instantaneous active power signal output by the converter; The oscillation frequency detector is used to receive the instantaneous active power signal output by the converter, calculate the oscillation frequency and obtain an oscillation signal containing different frequency bands; The oscillation frequency band selector is used to receive the oscillation signal and the instantaneous active power signal, and decompose the oscillation signal into an original low-frequency band signal, an original mid-frequency band signal, and an original high-frequency band signal according to different frequency band ranges; The multi-band damper is used to receive the original low-frequency band signal, the original medium-frequency band signal and the original high-frequency band signal, and obtain the low-frequency oscillation signal, the medium-frequency oscillation signal and the high-frequency oscillation signal respectively through filtering and integration processing by the multi-band damper.

3. The multi-band control device for a grid-connected converter for suppressing broadband oscillation according to claim 2, characterized in that: The multi-band damping controller includes a low-pass filter, a first proportional device, a first lead-lag module, a band-pass filter, a second proportional device, a second lead-lag module, a high-pass filter, a third proportional device, and a third lead-lag module; The low-pass filter is used to perform low-pass filtering on the original low-frequency band signal to obtain a filtered low-frequency band signal; The first proportional device is used to calculate the proportion of the filtered low-frequency signal to obtain a conditioned low-frequency signal; The first lead-lag module is used to perform lead-lag adjustment on the conditioned low-frequency band signal to obtain a low-frequency oscillation signal, which is subsequently superimposed on a reference instruction for DC voltage or active power control; The bandpass filter is used to perform bandpass filtering on the intermediate frequency band signal to obtain a filtered intermediate frequency band signal; The second proportional device is used to perform proportional calculation on the filtered intermediate frequency band signal to obtain a conditioned low frequency band signal; The second lead-lag module is used to perform lead-lag adjustment on the conditioned low-frequency band signal to obtain a medium-frequency oscillation signal, which is subsequently superimposed on the reference instruction of the d-axis current controller; The high-pass filter is used to perform high-pass filtering on the high-frequency band signal to obtain a filtered high-frequency band signal; The third proportional device is used to perform proportional calculation on the filtered high-frequency band signal to obtain a conditioned high-frequency band signal; The third lead-lag module is used to perform lead-lag adjustment on the conditioned high-frequency band signal to obtain a high-frequency oscillation signal, which is subsequently input into the feedforward control.

4. The multi-band control device for a grid-connected converter for suppressing broadband oscillation according to claim 1, wherein: The low-frequency band suppressor includes a subtractor, an adder, and a DC voltage PI controller; The subtractor is used to subtract the DC voltage reference signal from the DC voltage signal to obtain a voltage error signal; The adder is used to add the voltage error signal transmitted by the subtractor and the low-frequency oscillation signal to obtain a low-frequency error compensation signal; The DC voltage PI controller is used to perform proportional-integral calculation and processing on the low-frequency error compensation signal to obtain a d-axis current reference value signal.

5. The multi-band control device for a grid-connected converter for suppressing broadband oscillation according to claim 1, characterized in that: The intermediate frequency band suppressor comprises a subtractor, an adder, and a d-axis current PI controller; The subtractor is used to subtract the d-axis current reference value signal from the d-axis current signal to obtain a d-axis current error signal; The adder is used to add the d-axis current error signal transmitted by the subtractor and the intermediate frequency oscillation signal to obtain an intermediate frequency error compensation signal; The d-axis current PI controller is used to perform proportional-integral calculation and processing on the intermediate frequency error compensation signal to obtain the internal potential signal of the d-axis converter.

6. The multi-band control device for a grid-connected converter for suppressing broadband oscillation according to claim 1, characterized in that: The high-frequency band suppressor includes a subtractor and an adder; The adder is used to add the signal to the voltage signal in the d-axis of the converter to obtain a d-axis voltage composite signal; The adder is used to add the d-axis voltage synthesis signal transmitted from the previous stage and the high-frequency oscillation signal to obtain a first modulation voltage d-axis component signal.

7. A multi-band control method for a grid-connected converter for suppressing broadband oscillation, characterized in that: The method is carried out using the device according to any one of claims 1 to 6, comprising: The broadband oscillation controller receives the voltage signal uabc and the current signal iabc collected by the grid connection point PCC, and processes the voltage signal uabc and the current signal iabc through instantaneous active power calculation, oscillation frequency detection, oscillation signal decomposition, and multi-band damper filtering and integration to obtain a low-frequency oscillation signal, a medium-frequency oscillation signal, and a high-frequency oscillation signal; The cascade multi-scale controller suppresses the input low-frequency oscillation signal, medium-frequency oscillation signal and high-frequency oscillation signal in the low-frequency band, medium-frequency band and high-frequency band respectively to obtain a first modulated voltage d-axis component signal, and obtains a second modulated voltage d-axis component signal based on the converter terminal voltage signal and the converter terminal voltage reference value signal. The first modulated voltage d-axis component signal and the second modulated voltage d-axis component signal are subjected to coordinate transformation and modulation calculation to obtain a PWM signal, and the PWM signal is input into the three-phase full-bridge inverter circuit for control.

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