A broadband oscillation suppression method and controller based on energy storage system

Abstract

The present invention discloses a method and controller for suppressing broadband oscillation based on an energy storage system. The energy storage system obtains the voltage variation on the DC bus of an offshore wind power flexible direct current transmission system through a detection device. The energy storage system is connected to the DC bus of the offshore wind power flexible direct current transmission system. By detecting the voltage variation on the DC bus of the offshore wind power flexible direct current transmission system, it is determined whether broadband oscillation occurs on the DC bus and its oscillation frequency band. The DC / DC converter of the energy storage system is controlled to output a reverse-varying voltage to suppress the voltage fluctuation on the DC bus. Furthermore, the control parameters are adjusted according to the suppression effect. Through the above method, the oscillation generated by the offshore wind power flexible direct current transmission system is effectively suppressed by the energy storage system.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-connected renewable energy via flexible direct current transmission, and in particular to a method and controller for suppressing wide-band oscillations based on an energy storage system. Background Art

[0002] With the rapid development of offshore wind power, the risk of broadband oscillation in offshore wind power and its grid-connected flexible direct current (VDC) systems has become increasingly prominent, seriously impacting the safe and stable operation of the systems and equipment. Due to significant differences in the control structures and parameters of power electronic equipment such as offshore wind farms and MMC-HVDC, the impedance of these equipment exhibits negative damping characteristics across different frequency bands, exposing the system to the risk of broadband oscillation and further complicating its mechanisms.

[0003] The problem of broadband oscillation suppression measures can be divided into three sub-problems: the configuration location of oscillation suppression measures, the design of the control loop of oscillation suppression measures, and the parameter adjustment of oscillation suppression measures. As for the configuration location of oscillation suppression measures, from the perspective of traditional power system research, the eigenvalue / participation factor method is often used to find the strongly correlated variables of the oscillation mode. The controller of this variable is the location where the suppression measures are configured. From the perspective of power electronics research, there are two approaches: one is to locate the controller of the corresponding bandwidth according to the frequency band of the oscillation. This controller is the location where suppression measures need to be configured or the controller parameters need to be optimized; the other is to directly configure the suppressor at the location of the voltage and current feedback or feedforward containing the oscillation component. At this stage, the combination of the two approaches from the power electronics perspective is often used in engineering to provide ideas for optimizing controller parameters and design corresponding oscillation suppressors.

[0004] Energy storage systems, with their rapid regulation capabilities, play a vital role in the stable control of offshore wind power flexible direct current transmission systems. This is crucial for ensuring the safe and stable operation of power systems and achieving their low-carbon goals. However, there are no effective, mature, and standardized methods or technical means for using energy storage systems to suppress oscillations generated by offshore wind power flexible direct current transmission systems. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a broadband oscillation suppression method and controller based on an energy storage system, so as to realize the suppression of oscillations generated by an offshore wind power flexible direct current transmission system by utilizing the energy storage system.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A method for suppressing broadband oscillation based on an energy storage system, comprising the steps of:

[0008] S1. The energy storage system obtains the voltage variation on the DC bus of the offshore wind power flexible direct current transmission system through a detection device, and determines the oscillation frequency band characteristics based on the voltage variation;

[0009] The energy storage system is connected to the DC bus of the wind power flexible DC transmission system;

[0010] S2. The energy storage system calculates control parameters for oscillation suppression based on the oscillation frequency band characteristics, and controls the DC / DC converter of the energy storage system to output a reverse voltage to suppress voltage fluctuations on the DC output circuit;

[0011] S3. Adjust the control parameters of the energy storage system according to the oscillation suppression effect of S2.

[0012] In order to solve the above technical problems, another technical solution adopted by the present invention is:

[0013] A controller includes a microprocessor, a drive circuit, a feedback loop, an analog-to-digital converter, and a pulse width modulation controller. When the microprocessor executes control logic through the drive circuit, the feedback loop, the analog-to-digital converter, and the pulse width modulation controller, the steps of the above-mentioned method for suppressing wide-band oscillation based on an energy storage system are implemented.

[0014] The beneficial effects of the present invention are as follows: a wide-band oscillation suppression method and controller based on an energy storage system of the present invention detects the voltage change on the DC output circuit of the offshore wind power flexible direct current transmission system, and the energy storage system outputs a reverse voltage change according to the voltage change, thereby suppressing the voltage fluctuation on the DC output circuit, and adjusting the control parameters according to the suppression effect, thereby realizing the effective suppression of the oscillation generated by the offshore wind power flexible direct current transmission system by using the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a flow chart of a method for suppressing broadband oscillation based on an energy storage system according to an embodiment of the present invention;

[0016] Figure 2 This is a diagram of a phase-locked loop control structure of a flexible DC converter station based on a wide-band oscillation suppression method of an energy storage system according to an embodiment of the present invention;

[0017] Figure 3 A schematic diagram of a control structure of an energy storage system configuration oscillation suppression measure based on a wide-band oscillation suppression method of an energy storage system according to an embodiment of the present invention;

[0018] Figure 4 This is a specific flow chart of a method for suppressing broadband oscillation based on an energy storage system according to an embodiment of the present invention;

[0019] Figure 5 The topology diagram of the grid-connected offshore wind farm including the energy storage system through the flexible direct current transmission system;

[0020] Figure 6 Schematic diagram of the voltage change on the DC bus after the energy storage system suppression measures are put into use;

[0021] Figure 7 Schematic diagram of the main structure of the energy storage system controller. DETAILED DESCRIPTION

[0022] To illustrate the technical content, achieved objectives and effects of the present invention in detail, the following description is given in conjunction with the embodiments and accompanying drawings.

[0023] Please refer to Figures 1 to 4 , a method for suppressing broadband oscillation based on an energy storage system, comprising the steps of:

[0024] S1. The energy storage system obtains the voltage variation on the DC bus of the offshore wind power flexible direct current transmission system through a detection device, and determines the oscillation frequency band characteristics based on the voltage variation;

[0025] The energy storage system is connected to the DC bus of the wind power flexible DC transmission system;

[0026] S2. The energy storage system calculates control parameters for oscillation suppression based on the oscillation frequency band characteristics, and controls the DC / DC converter of the energy storage system to output a reverse voltage to suppress voltage fluctuations on the DC output circuit;

[0027] S3. Adjust the control parameters of the energy storage system according to the oscillation suppression effect of S2.

[0028] From the above description, it can be seen that the beneficial effects of the present invention are: a wide-band oscillation suppression method and controller based on an energy storage system of the present invention detects the voltage change on the DC output circuit of the offshore wind power flexible direct current transmission system, and the energy storage system outputs a reverse voltage change according to the voltage change, thereby suppressing the voltage fluctuation on the DC output circuit, and realizing the use of the energy storage system to suppress the oscillation generated by the offshore wind power flexible direct current transmission system.

[0029] Furthermore, step S1 includes the steps of:

[0030] S11. Detecting the harmonic frequency of the power grid through a phase-locked loop in the flexible DC converter station;

[0031] S12. Distinguish oscillation frequency band characteristics of the power system based on the detected grid harmonic frequencies.

[0032] As can be seen from the above description, the harmonic frequency of the power grid is detected by a phase-locked loop, and the characteristics of different oscillation frequency bands are distinguished according to the harmonic frequency.

[0033] Furthermore, step S12 is specifically as follows:

[0034] If the harmonic frequency of the power system is between 1-100 Hz, it is considered to be sub / supersynchronous oscillation;

[0035] If the harmonic frequency of the power system is above 100 Hz, it is considered to be medium-high frequency oscillation.

[0036] From the above description, it can be seen that oscillations are divided into subsynchronous / supersynchronous oscillations and medium and high frequency oscillations according to the harmonic frequency.

[0037] Furthermore, step S2 includes the steps of:

[0038] Active damping control is used for the energy storage system. The control parameters include: the gain k of the high-pass filter b , the bandwidth of the high-pass filter ω b The control parameter calculation method is as follows:

[0039] According to impedance theory, the constraints for system stability are:

[0040] S21. Calculating control parameters for power control of an energy storage system according to the harmonic frequency and the oscillation frequency band characteristics;

[0041] S22. Perform power control on the energy storage system according to the control parameters and output it through DC / DC.

[0042] From the above description, it can be seen that the energy storage system performs power control based on the harmonic frequency and oscillation frequency band characteristics so that the DC / DC output voltage can suppress oscillation.

[0043] Furthermore, step S21 is specifically as follows:

[0044]

[0045] Among them, ω be is the harmonic frequency, obtained by the phase-locked loop; L dc is the equivalent inductance of the DC side; C be Support capacitors for energy storage systems;

[0046] Multiply both sides of the inequality by the battery energy storage rated voltage E be And process it, we can get ω without considering the bandwidth b The damping controller gain k is b The value range of is:

[0047]

[0048] Among them, P be is the rated capacity of the battery, ZMMC is the impedance of the MMC at the parallel resonant frequency;

[0049] Consider bandwidth ω b After the influence of , we get the following inequality:

[0050]

[0051] in:

[0052] N≈E be ω be C be (ω be L dc -|Z MMC |);

[0053] The solution is:

[0054]

[0055]

[0056] For the damping controller gain k b Take the maximum value within the allowed range, bandwidth ω b Take the minimum value in the allowed range.

[0057] From the above description, we can see that according to impedance theory, if there is no amplitude intersection between the two subsystems, the system must be stable. Therefore, it is necessary to calculate appropriate parameters so that the impedance amplitude Z of the battery energy storage device (bidirectional DC-DC converter) itself is be Less than the MMC's own impedance Z at the parallel resonant frequency MMC Considering the impedance amplitude Z of the battery energy storage device (bidirectional DC-DC converter) itself be is the bandwidth ω b A monotonically decreasing function, we can first let the bandwidth ω b is zero, thus solving the maximum gain coefficient k that must satisfy the constraints b .

[0058] Furthermore, the damping controller uses a first-order high-pass filter with a transfer function of

[0059]

[0060] In the above formula, k b is the gain of the high-pass filter, s is the Laplace operator, ω b is the bandwidth of the high-pass filter.

[0061] From the above description, it can be seen that the active damping controller is selected as a first-order high-pass filter.

[0062] Furthermore, step S3 includes:

[0063] S31, obtaining harmonic content and fundamental wave content, and determining whether the harmonic content is within a preset first range and whether the fundamental wave content is within a preset second range;

[0064] If the harmonic content is within the first range and the fundamental content is within the second range, then the control parameter is not adjusted;

[0065] If the harmonic content exceeds the first range, but the fundamental content is within the second range, then the damping controller gain k is reduced. b , to increase the voltage output by the energy storage system;

[0066] If the harmonic content is within the first range, but the fundamental content is below the second range, then increase the damping controller gain k b , to reduce the voltage output by the energy storage system;

[0067] S32. Repeat step S31 until the harmonic content is within a preset first range and the fundamental wave content is within a preset second range.

[0068] From the above description, we can know that the gain k of the damping controller is adjusted according to the harmonic content and fundamental content. b Adjust the output voltage to achieve better suppression effect.

[0069] A controller includes a microprocessor, a drive circuit, a feedback loop, an analog-to-digital converter, and a pulse width modulation controller. When the microprocessor executes control logic through the drive circuit, the feedback loop, the analog-to-digital converter, and the pulse width modulation controller, the steps of the above-mentioned method for suppressing wide-band oscillation based on an energy storage system are implemented.

[0070] The invention provides a broadband oscillation suppression method and controller based on an energy storage system, which is suitable for scenarios where an offshore wind power flexible direct current transmission system outputs broadband oscillations and oscillation suppression is required.

[0071] Please refer to Figure 1 , embodiment 1 of the present invention is:

[0072] A method for suppressing broadband oscillation based on an energy storage system, comprising the steps of:

[0073] S1. The energy storage system obtains the voltage variation on the DC bus of the offshore wind power flexible direct current transmission system through a detection device, and determines the oscillation frequency band characteristics based on the voltage variation;

[0074] The energy storage system is connected to the DC bus of the wind power flexible DC transmission system;

[0075] In this embodiment, an energy storage system is connected to the DC bus in the established offshore wind power flexible direct current transmission system. When broadband oscillation occurs in the offshore wind power flexible direct current transmission system, the voltage on the DC bus will inevitably fluctuate. At this time, the energy storage system is used to suppress the fluctuation of the voltage on the DC bus.

[0076] S2. The energy storage system calculates control parameters for oscillation suppression based on the oscillation frequency band characteristics, and controls the DC / DC converter of the energy storage system to output a reverse voltage to suppress voltage fluctuations on the DC output circuit.

[0077] Based on the offshore wind power flexible direct current transmission system model and the damping controller model, an active damping oscillation suppression model of the offshore wind power flexible direct current transmission system based on the energy storage system is constructed, and the oscillation suppression control strategy is integrated into the energy storage system controller:

[0078] The oscillation suppression control strategy obtains the voltage change on the DC bus of the flexible direct current transmission system through a detection device, and then controls the reverse Δu output by the DC / DC converter of the energy storage system, and uses the energy storage system to suppress the voltage fluctuation on the DC bus, thereby suppressing the broadband oscillation of the offshore wind power flexible direct current transmission system.

[0079] S3. Adjust the control parameters of the energy storage system according to the oscillation suppression effect of S2.

[0080] Please refer to Figures 1 to 4 , the second embodiment of the present invention is:

[0081] A method for suppressing broadband oscillation based on an energy storage system, comprising the steps of:

[0082] S1. The energy storage system obtains the voltage variation on the DC bus of the offshore wind power flexible direct current transmission system through a detection device, and determines the oscillation frequency band characteristics based on the voltage variation;

[0083] The energy storage system is connected to the DC bus of the wind power flexible DC transmission system;

[0084] Step S1 includes the steps of:

[0085] S11. Detecting the harmonic frequency of the power grid through the phase-locked loop in the flexible DC converter station;

[0086] S12. distinguishing the oscillation frequency band characteristics of the power system based on the detected grid harmonic frequencies;

[0087] Step S12 is specifically as follows:

[0088] If the harmonic frequency of the power system is between 1-100 Hz, it is considered to be sub / supersynchronous oscillation;

[0089] If the harmonic frequency of the power system is above 100 Hz, it is considered to be medium-high frequency oscillation.

[0090] In this embodiment, a phase-locked loop in a flexible DC converter station is used to detect the harmonic frequency of the power grid. When broadband oscillation harmonics are detected, the oscillation is divided into sub- / super-synchronous oscillations and medium- and high-frequency oscillations according to the harmonic frequency, thereby distinguishing the characteristics of different oscillation frequency bands.

[0091] The grid harmonic frequency is detected by the phase-locked loop (PLL) in the flexible DC converter station. The phase-locked loop can track the frequency and phase angle of the grid voltage. When the grid voltage contains harmonics, the output frequency of the phase-locked loop will change, and then the frequency signal will be passed to the oscillation suppression parameter calculation link. Specifically, the control structure diagram of the phase-locked loop (PLL) can be as follows: Figure 2 As shown, V abc is the AC voltage at the outlet, which is converted into its d and q axis components V by Park transformation P(θ) d and V q , where V q The PI controller H pll (s) can be used to get the grid voltage frequency ω, and then the grid voltage phase angle can be obtained through the integrator. The expression of the phase-locked loop PI controller is:

[0092]

[0093] In the above formula, K pp and K pi are the proportional coefficient and integral coefficient of the phase-locked loop controller, and s is the Laplace operator;

[0094] After obtaining the grid voltage frequency ω, the grid voltage phase angle is obtained through an integrator. The expression is:

[0095] θ=∫ωdt+θ0;

[0096] The Parker transformation formula is:

[0097]

[0098] Based on the detected grid harmonic frequencies, the characteristics of different oscillation frequency bands are distinguished. Specifically, in this example, if the harmonic frequency of the phase-locked loop output is in the range of 1-100Hz, the system is experiencing sub- / super-synchronous oscillation. If it is above 100Hz, the system is considered to be experiencing medium- and high-frequency oscillation. Sub- / super-synchronous oscillations are characterized by being significantly influenced by various control links in the system, exhibiting constant amplitude oscillations, slowly diverging oscillations, or exhibiting periodic divergence and convergence. The oscillation frequency is accurate to single digits, and a dual frequency component relative to 50Hz exists. Medium- and high-frequency oscillations are characterized by being significantly influenced by system delays, rapidly diverging oscillations, and a frequency range near the center frequency, making it difficult to accurately determine the frequency to single digits. These oscillation characteristics influence the parameter design of oscillation suppression measures.

[0099] S2. The energy storage system calculates control parameters for oscillation suppression based on the oscillation frequency band characteristics, and controls the DC / DC converter of the energy storage system to output a reverse voltage to suppress voltage fluctuations on the DC output circuit.

[0100] In this embodiment, refer to Figure 3 The energy storage system configuration oscillation suppression control structure shown in the figure, where i * and i are the reference value and actual measured value of the energy storage system current respectively. sign(x) is the sign function, which is determined by the charge and discharge direction. i * ≥0, sign(i * )=1, on the contrary sign(i * )=-1. i (s) is the current inner loop proportional integral (PI) controller, and its expression is:

[0101]

[0102] In the above formula, K pi and K ii are the proportional coefficient and integral coefficient of the PI controller, and s is the Laplace operator. Figure 3 In, V ref It is the reference voltage generated by the controller of the energy storage system. It controls the on and off of the IGBT in the input modulation link. The oscillation suppression measures are integrated into the DC / DC converter of the energy storage system. The control object is the output voltage, which includes:

[0103] Step S2 includes the steps of:

[0104] The active damping controller is selected as a first-order high-pass filter, and the transfer function is:

[0105]

[0106] In the above formula, k bis the gain of the high-pass filter, s is the Laplace operator, ω b is the bandwidth of the high-pass filter.

[0107] S21. Calculate control parameters for power control of an energy storage system according to the harmonic frequency and the oscillation frequency band characteristics.

[0108] In this embodiment, according to impedance theory, if there is no amplitude intersection between the two subsystems, the system must be stable. Therefore, it is necessary to calculate appropriate parameters so that the impedance amplitude Z of the battery energy storage device (bidirectional DC-DC converter) itself is be Less than the MMC's own impedance Z at the parallel resonant frequency MMC Considering the impedance amplitude Z of the battery energy storage device (bidirectional DC-DC converter) itself be is the bandwidth ω b A monotonically decreasing function, we can first let the bandwidth ω b is zero, thus solving the maximum gain coefficient k that must satisfy the constraints b According to this theory, we have:

[0109] |Z be (jω be )|≤|Z MMC (jω be )+jω be L dc |;

[0110] Right now:

[0111]

[0112] Among them, ω be is the harmonic frequency, obtained by the phase-locked loop; L dc is the equivalent inductance of the DC side; C be Support capacitors for energy storage systems;

[0113] Multiply both sides of the inequality by the battery energy storage rated voltage E be And process it, we can get ω without considering the bandwidth b The damping controller gain k is b The value range of is:

[0114]

[0115] Among them, P be is the rated capacity of the battery, Z MMC is the impedance of the MMC at the parallel resonant frequency;

[0116] Consider bandwidth ω b After the influence of , we get the following inequality:

[0117]

[0118] in:

[0119] N≈E be ω be C be (ω be L dc -|Z MMC |);

[0120] The solution is:

[0121]

[0122]

[0123] For the damping controller gain k b Take the maximum value within the allowed range, bandwidth ω b Take the minimum value in the allowed range.

[0124] S22. Perform power control on the energy storage system according to the control parameters and output it through DC / DC.

[0125] In this embodiment, the controller is put into the oscillation suppression measure control loop. Except for the control and calculation delays, it should be put into use as soon as possible to avoid further divergence of the oscillation.

[0126] S3. Adjust the control parameters of the energy storage system according to the oscillation suppression effect of S2.

[0127] In this embodiment, the oscillation suppression effect is observed. After the above-mentioned oscillation suppression measure control loop is put into operation, the phase-locked loop and the voltage and current detection units work together to examine whether the oscillation can be suppressed and whether it is over-suppressed. The determining factors are the harmonic content and fundamental wave content in the voltage and current waveforms.

[0128] Step S3 includes the steps of:

[0129] S31, obtaining harmonic content and fundamental wave content, and determining whether the harmonic content is within a preset first range and whether the fundamental wave content is within a preset second range;

[0130] If the harmonic content is within the first range and the fundamental content is within the second range, then the control parameter is not adjusted;

[0131] If the harmonic content exceeds the first range, but the fundamental content is within the second range, then the damping controller gain k is reduced. b , to increase the voltage output by the energy storage system;

[0132] If the harmonic content is within the first range, but the fundamental content is below the second range, then increase the damping controller gain k b , to reduce the voltage output by the energy storage system.

[0133] S32. Repeat step S31 until the harmonic content is within a preset first range and the fundamental wave content is within a preset second range.

[0134] In this embodiment, if the harmonics are basically eliminated and the fundamental content returns to normal, it means that the designed parameters are suitable for suppressing oscillations and no fine-tuning is required; if the harmonics are not completely eliminated, consider slightly reducing the damping controller gain k b , increase the output voltage of the energy storage system. If the harmonics are completely eliminated and the fundamental content is also reduced, consider slightly increasing the damping controller gain k b , reduce the voltage output by the energy storage system. When fine-tuning, it is necessary to combine k b 、ω b The corresponding order of magnitude ensures the accuracy and effectiveness of the fine-tuning process.

[0135] The third embodiment of the present invention is:

[0136] A controller includes a microprocessor, a drive circuit, a feedback loop, an analog-to-digital converter, and a pulse width modulation controller. When the microprocessor executes control logic through the drive circuit, the feedback loop, the analog-to-digital converter, and the pulse width modulation controller, the steps of the method for suppressing wide-band oscillation based on an energy storage system described in the first or second embodiment above are implemented.

[0137] Based on the above embodiments, please refer to Figure 5 The structure of an offshore wind farm connected to the grid via flexible HVDC transmission is shown in the diagram. A simulation model was constructed in Matlab / Simulink to validate the proposed broadband oscillation suppression method. The offshore wind farm is equipped with full-power wind turbines using permanent magnet synchronous generators. After the wind farm is boosted to a higher voltage through a step-up transformer, it is connected to the flexible HVDC converter station via a submarine cable. Energy storage devices are installed on the HVDC transmission line to suppress broadband oscillations. Figure 6 This is the voltage change on the DC bus after the energy storage system suppression measures are put into use.

[0138] In summary, the present invention provides a wide-band oscillation suppression method and controller based on an energy storage system. By detecting the voltage change on the DC output circuit of the offshore wind power flexible direct current transmission system, the energy storage system outputs a reverse voltage change according to the voltage change, thereby suppressing the voltage fluctuation on the DC output circuit, thereby realizing the use of the energy storage system to suppress the oscillations generated by the offshore wind power flexible direct current transmission system.

[0139] Compared with the existing technology, the present invention establishes a relationship between the oscillation mode, the energy storage system, and the damping controller parameters. By matching the real-time collected oscillation mode with the known oscillation modes in the database, the present invention selects appropriate energy storage system and damping controller parameters to suppress the oscillation and ensure that it meets the predetermined damping performance. This method provides an effective method and means for suppressing broadband oscillations in offshore wind power flexible direct current transmission systems, helping to improve the stability of the power system.

[0140] First, the performance requirements for energy storage systems to suppress power system oscillations include both the damping ratio and the time-delay stability margin. Compared with traditional oscillation suppression performance requirements based only on the damping ratio, the designed oscillation control strategy has a wider range of adaptability, allowing the energy storage system to meet the expected requirements when suppressing power system oscillations even if there is a signal transmission delay.

[0141] Secondly, the method for suppressing wide-band oscillations of the offshore wind farm through the flexible DC transmission system specifically calculates and designs the oscillation suppressor parameters according to the characteristics of sub- / super-synchronous and medium- and high-frequency oscillations; in conjunction with the resonant frequency sensed by the phase-locked loop, the oscillation suppressor parameters are fine-tuned by judging the oscillation suppression effect until the oscillation suppression requirements are met, thereby being able to suppress harmonics in the entire frequency band.

[0142] Therefore, the present invention realizes the suppression of power system oscillations by the offshore wind farm through the flexible DC transmission system energy storage system, provides an effective method for better exerting the stable control function of the energy storage system, helps to improve the safe and stable control level of the power system, and ensures the safe and stable operation of the low-carbon power system.

[0143] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's description and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for suppressing broadband oscillation based on an energy storage system, characterized in that: Including steps: S1. The energy storage system obtains the voltage variation on the DC bus of the offshore wind power flexible direct current transmission system through a detection device, and determines the oscillation frequency band characteristics based on the voltage variation; Step S1 includes the steps of: S11. Detecting the harmonic frequency of the power grid through a phase-locked loop in the flexible DC converter station; S12. distinguishing the oscillation frequency band characteristics of the power system based on the detected grid harmonic frequencies; The energy storage system is connected to the DC bus of the wind power flexible DC transmission system; S2. The energy storage system calculates control parameters for oscillation suppression based on the oscillation frequency band characteristics, and controls the DC / DC converter of the energy storage system to output a reverse voltage to suppress voltage fluctuations on the DC output circuit; Step S2 includes the steps of: S21. Calculating control parameters for power control of an energy storage system according to the harmonic frequency and the oscillation frequency band characteristics; Step S21 is specifically as follows: Active damping control is used for the energy storage system. The control parameters include: the gain of the high-pass filter , the bandwidth of the high-pass filter , the control parameter calculation method is as follows: According to impedance theory, the constraints for system stability are: ； in, is the harmonic frequency, obtained by the phase-locked loop; L dc is the equivalent inductance of the DC side; C be Support capacitors for energy storage systems; Multiply both sides of the inequality by the rated voltage E of the battery energy storage be And process it, you can get it without considering bandwidth The damping controller gain k is b The value range of is: ； in, is the rated capacity of the battery, Z MMC is the impedance of the MMC at the parallel resonant frequency; Consider bandwidth After the influence of , we get the following inequality: ； in: ； The solution is: ； ； For the damping controller gain k b Take the maximum value within the allowed range, bandwidth Take the minimum value within the allowed range; S22, controlling the power of the energy storage system according to the control parameters and outputting the power through a DC / DC converter; S3. Adjust the control parameters of the energy storage system according to the oscillation suppression effect of S2.

2. A method for suppressing broadband oscillation based on an energy storage system according to claim 1, characterized in that: Step S12 is specifically as follows: If the harmonic frequency of the power system is between 1-100 Hz, it is considered to be sub / supersynchronous oscillation; If the harmonic frequency of the power system is above 100 Hz, it is considered to be medium-high frequency oscillation.

3. The method for suppressing broadband oscillation based on an energy storage system according to claim 1, characterized in that: The damping controller uses a first-order high-pass filter with a transfer function of ； In the above formula, is the gain of the high-pass filter, is the Laplace operator, is the bandwidth of the high-pass filter.

4. The method for suppressing broadband oscillation based on an energy storage system according to claim 1, characterized in that: The step S3 comprises: S31, obtaining harmonic content and fundamental wave content, and determining whether the harmonic content is within a preset first range and whether the fundamental wave content is within a preset second range; If the harmonic content is within the first range and the fundamental content is within the second range, then the control parameter is not adjusted; If the harmonic content exceeds the first range, but the fundamental content is within the second range, then the damping controller gain k is reduced. b , to increase the voltage output by the energy storage system; If the harmonic content is within the first range, but the fundamental content is below the second range, then increase the damping controller gain k b , to reduce the voltage output by the energy storage system; S32. Repeat step S31 until the harmonic content is within a preset first range and the fundamental wave content is within a preset second range.

5. A controller comprising a microprocessor, a drive circuit, a feedback loop, an analog-to-digital converter, and a pulse width modulation controller, wherein the microprocessor, when executing control logic through the drive circuit, the feedback loop, the analog-to-digital converter, and the pulse width modulation controller, implements the steps of the method for suppressing wide-band oscillation based on an energy storage system according to any one of claims 1 to 4.

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