Broadband oscillation damping control system and method integrating multiple anti-error measures

Abstract

According to the broadband oscillation damping control system and method integrating multiple anti-error measures, a damping controller takes grid-connected bus voltage, grid-connected bus current and compensation current output by a compensation converter as input signals, and the damping controller outputs a compensation current reference value to the compensation converter; compensating current output by the compensating converter is injected into a grid-connected bus of the new energy station; the damping controller generates a compensation current instruction according to the oscillation characteristic of the input signal, and determines whether the damping controller is unlocked or locked according to the input signal; when the damping controller is switched from the locking state to the unlocking state, uniform slope climbing processing is carried out on the compensation current instruction, and when the damping controller is switched from the unlocking state to the locking state, uniform slope descending processing is carried out on the compensation current instruction; when the amplitude of the processed compensation current instruction exceeds the limit, correcting the processed compensation current instruction and taking the corrected compensation current instruction as a compensation current reference value; otherwise, the processed compensation current instruction serves as a compensation current reference value, and the optimal damping control effect is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power system stability control, and specifically, relates to a damping control system and method for wide-band oscillation management integrating multiple error prevention measures applied to new energy stations. Background Art

[0002] The new power system has the dual characteristics of "high proportion of new energy" and "high proportion of power electronic equipment". This characteristic changes the dynamic behavior of the system dominated by traditional synchronous machines. The diversified power electronic equipment and control strategies bring many problems to the system, such as damage to electrical equipment, twisting of the shaft system of steam turbine generator sets, disconnection of new energy units from the grid, and even local / whole grid safety and stability accidents, which have become an important issue restricting the development of the new power system.

[0003] Various types of oscillation events caused by the grid connection of new energy and power electronic equipment occur frequently, and the broadband stability of the system faces severe challenges. Broadband oscillation suppression provides an effective solution for balancing system stability and new energy consumption. For new energy stations with high oscillation risks, the amplitude-frequency and phase-frequency characteristics of the station port can be improved by adjusting the control parameters of the wind turbine or photovoltaic converter, and the system damping can be improved; and for old units whose converter model parameters cannot be adjusted, the anti-interference ability of the system can be greatly improved by adding a damping controller. However, in the prior art, the broadband suppression method of the wind power grid-connected system focuses on the design of control parameters, and does not involve anti-error protection during control output. The semi-active broadband suppression energy consumption device of the transmission line magnetic negative stiffness broadens the vibration reduction frequency band and realizes efficient suppression of the conductor vibration, but the sampling method of the magnet assembly cannot achieve damping control. The low-pass filter with broadband suppression capability forms an LC resonant circuit through capacitors and inductors to improve the harmonic suppression effect in the high-frequency range, but cannot achieve damping control. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a wide-band oscillation damping control system and method integrating multiple anti-error measures. The wide-band oscillation damping control system is deployed in a new energy station. A power electronic controllable impedance is connected in parallel at the outlet of the station to achieve damping improvement and optimization, and output anti-error measures are implemented. The design of the damping control strategy and the characteristics of the power electronic devices are comprehensively considered. Multiple protection measures are designed from the generation link of the control signal and the processing link before the control signal is sent to the converter to ensure that the current injected by the damping controller into the system side is a pure, effective and reliable suppression signal, thereby achieving the best damping control effect.

[0005] The present invention adopts the following technical solution.

[0006] The present invention proposes a wide-band oscillation damping control system integrating multiple error prevention measures, comprising: a damping controller and a compensation converter; the damping controller takes the grid-connected bus voltage, the grid-connected bus current and the compensation current output by the compensation converter as input signals, and the damping controller outputs a compensation current reference value to the compensation converter; according to the compensation current reference value, the compensation current output by the compensation converter is injected into the grid-connected bus of the new energy station;

[0007] In the damping controller, a compensation current command is generated according to the oscillation characteristics of the input signal, and whether the damping controller is unlocked or locked is determined according to the input signal; when the damping controller switches from locked to unlocked, the generated compensation current command is subjected to uniform climbing processing, and when the damping controller switches from unlocked to locked, the generated compensation current command is subjected to uniform descending processing; when the amplitude of the processed compensation current command exceeds the limit, the processed compensation current command is corrected and used as the compensation current reference value; otherwise, the processed compensation current command is used as the compensation current reference value.

[0008] Preferably, in the damping controller, generating a compensation current instruction according to the oscillation characteristics of the input signal comprises:

[0009] The input signal is sampled and the spectrum of the input signal is obtained by fast Fourier transform;

[0010] Based on the spectrum of the input signal, the extreme point determination method is used to extract the oscillation frequency, and the spectrum line interpolation method is used to determine the oscillation amplitude at the oscillation frequency;

[0011] When the oscillation amplitude at the oscillation frequency exceeds the set threshold value, it is determined that oscillation occurs and the damping controller is started;

[0012] After the damping controller is started, the grid-connected bus current is filtered through the power frequency filter to remove the power frequency component; the grid-connected bus current after the power frequency component is filtered out is passed through a bandpass filter to obtain the current within the target control frequency band; the current within the target control frequency band is subjected to proportional phase shifting to obtain the compensation current instruction.

[0013] Preferably, the threshold value is set to 2% of the rated value; and the target control frequency band is [4,20] Hz.

[0014] Preferably, determining whether the damping controller is unlocked or locked according to the input signal comprises:

[0015] 1) Oscillation characteristic identification, specifically: when the grid-connected bus voltage or grid-connected bus current oscillates, and the oscillation frequency is within the set target control frequency band and the oscillation amplitude exceeds the set threshold value, the damping controller unlocking signal based on the oscillation characteristic identification is set to 1, otherwise the damping controller unlocking signal based on the oscillation characteristic identification is set to 0;

[0016] 2) Grid current mutation judgment, specifically: when the real-time sampling value of the grid current has a mutation, the damping controller unlocking signal based on the grid current mutation judgment is set to 0, otherwise the damping controller unlocking signal based on the oscillation characteristic identification is set to 1;

[0017] 3) Suppression effect judgment, specifically: when the compensation current output by the damping controller is a positive damping characteristic, the damping controller unlocking signal based on the suppression effect judgment is set to 1, otherwise the damping controller unlocking signal based on the suppression effect judgment is set to 0;

[0018] When the damping controller unlocking signals corresponding to the above three items are all 1, it is determined that the damping controller is unlocked; otherwise, it is determined that the damping controller is locked.

[0019] Preferably, the power frequency effective value of the three-phase current of the grid-connected bus is calculated using the sampled value of the three-phase current of the grid-connected bus, satisfying the following relationship:

[0020]

[0021] In the formula, i a (k), i b (k), i c (k) is the kth sampling sample of the three-phase current of the grid-connected busbar, N is the total number of sampling points within the whole cycle of the power frequency, i rms_a 、i rms_b 、i rms_c It is the power frequency effective value of the three-phase current of the grid-connected bus;

[0022] When the change in the industrial frequency effective value of any phase current of the grid-connected bus within two judgment intervals is greater than 0.2 times the rated value, the unlocking signal of the damping controller based on the grid current mutation judgment is set to 0 to lock the damping controller; otherwise, the unlocking signal of the damping controller based on the oscillation characteristic identification is set to 1 to unlock the damping controller.

[0023] Preferably, the grid-connected bus voltage and the compensation current are sampled, and the frequency spectrum of the grid-connected bus voltage and the compensation current is obtained by fast Fourier transform;

[0024] Based on the frequency spectrum of the grid-connected bus voltage and compensation current, the extreme point is determined by the spectrum line extreme value method, and the voltage phasor at each frequency point is determined by the interpolation algorithm in the frequency domain. and current phasor j represents the jth frequency point, j = 1, ..., m, m is the total number of frequency points;

[0025] The positive-sequence voltage phasor at each frequency point is calculated using the voltage phasor at each frequency point, the positive-sequence current phasor at each frequency point is calculated using the current phasor at each frequency point, and the positive-sequence impedance phasor at each frequency point and the positive-sequence current phasor at each frequency point are calculated; when the real part of the positive-sequence impedance phasor at the j-th frequency point is less than zero, it is determined that the positive-sequence resistance at the j-th frequency point presents a negative resistance characteristic; otherwise, it is determined that the positive-sequence resistance at the j-th frequency point presents a positive resistance characteristic;

[0026] The negative-sequence voltage phasor at each frequency point is calculated using the voltage phasor at each frequency point, the negative-sequence current phasor at each frequency point is calculated using the current phasor at each frequency point, and the negative-sequence impedance phasor at each frequency point and the negative-sequence current phasor at each frequency point are calculated; when the real part of the negative-sequence impedance phasor at the j-th frequency point is less than zero, it is determined that the negative-sequence resistance at the j-th frequency point presents a negative resistance characteristic; otherwise, it is determined that the negative-sequence resistance at the j-th frequency point presents a positive resistance characteristic;

[0027] When the positive-sequence resistance or negative-sequence resistance at the jth frequency point presents a negative resistance characteristic, the unlocking signal of the damping controller based on the suppression effect judgment is set to 0 to lock the damping controller; otherwise, the unlocking signal of the damping controller based on the suppression effect judgment is set to 1 to unlock the damping controller.

[0028] Preferably, when the damping controller is locked, the compensation current command generated by the damping controller is set to zero.

[0029] Preferably, when the damping controller switches from locking to unlocking, the compensation current command is subjected to uniform climbing processing, including: within a set time period, the value of the compensation current command increases from 0 to the amplitude of the compensation current command generated according to the oscillation characteristics of the input signal; the compensation current command after the uniform climbing processing satisfies the following relationship:

[0030]

[0031] In the formula, I r ' ef is the compensation current command at time t after uniform ramp processing, I ref is the compensation current command generated according to the oscillation characteristics of the input signal, t s ,t e are the starting time and ending time of the set time period of uniform climbing processing respectively;

[0032] When the damping controller switches from unlocking to locking, the compensation current command is subjected to uniform slope reduction processing, including: within a set time period, the value of the compensation current command is reduced from the amplitude of the compensation current command generated according to the oscillation characteristics of the input signal to 0; the compensation current command after the uniform slope reduction processing satisfies the following relationship:

[0033]

[0034] In the formula, I r ″ ef is the compensation current command at time t after uniform slope reduction, I ref is the compensation current command generated according to the oscillation characteristics of the input signal, t s ,t e They are respectively the starting time and the ending time of the set time period for the uniform slope reduction process.

[0035] Preferably, when the processed compensation current instruction is less than the limit value, the instantaneous value of the processed compensation current instruction is used as the compensation current reference value; when the processed compensation current instruction is greater than the limit value, the ratio between the limit value and the amplitude of the compensation current instruction is used as the correction factor, and the product between the correction factor and the instantaneous value of the processed compensation current instruction is used as the compensation current reference value, and the limit value is 1pu; the specific implementation process is as follows:

[0036] Get the instantaneous value i of the compensation current command at the current time t after processing out_a (t), i out_b (t), i out_c (t), the amplitude of the compensation current command at the current moment t is calculated using the following relationship:

[0037]

[0038] In the formula, i amp (t) is the amplitude of the compensation current instruction at the current moment t;

[0039] If the amplitude i of the compensation current command at the current time t is amp (t) not greater than the limit value I lim , then the instantaneous value i of the compensation current instruction at the current time t after processing is out_a (t), i out_b (t), i out_c (t) is the compensation current instruction i sent by the damping controller to the compensation converter ref_a (t), i ref_b (t), i ref_c (t);

[0040] If the amplitude i of the compensation current command at the current time t is amp (t) is greater than the limit value I lim , then the limit value I lim The amplitude i of the compensation current command at the current time t amp (t) is used as the correction factor, and the compensation current instruction i sent by the damping controller to the compensation converter is ref_a (t), iref_b (t), i ref_c (t) satisfies the following relationship:

[0041] i ref_a (t) = k × i out_a (t)

[0042] i ref_b (t) = k × i out_b (t)

[0043] i ref_c (t) = k × i out_c (t)

[0044] In the formula, k is the correction factor, satisfying k = I lim i amp (t).

[0045] The present invention also proposes a broadband oscillation damping control method integrating multiple error prevention measures, comprising:

[0046] Collecting the grid-connected bus voltage, grid-connected bus current and compensation current output by the compensation converter as input signals of the damping controller;

[0047] The damping controller generates a compensation current command according to the oscillation characteristics of the input signal, and determines whether the damping controller is unlocked or locked according to the input signal;

[0048] When the damping controller switches from locking to unlocking, the generated compensation current instruction is subjected to uniform climbing processing, and when the damping controller switches from unlocking to locking, the generated compensation current instruction is subjected to uniform descending processing; when the amplitude of the processed compensation current instruction exceeds the limit, the processed compensation current instruction is corrected and used as the compensation current reference value; otherwise, the processed compensation current instruction is used as the compensation current reference value;

[0049] The damping controller outputs a compensation current reference value to the compensation converter; according to the compensation current reference value, the compensation current output by the compensation converter is injected into the grid-connected bus of the new energy station.

[0050] The present invention is also a terminal, comprising a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method.

[0051] The present invention is also a computer-readable storage medium having a computer program stored thereon, which implements the steps of the method when executed by a processor.

[0052] The beneficial effects of the present invention are that, compared with the prior art, at least the present invention provides a wide-band oscillation damping control system that integrates multiple anti-error measures and is connected in parallel to a new energy station. The present invention is mainly used to provide an improved device that takes anti-error measures into account and ensures reliable output for the wide-band damping equipment deployed to solve the problem of frequent wide-band oscillations in new power systems, implements control signal output anti-error measures, combines the damping control strategy and the requirements of the control signal for the control device selection design, and performs multiple anti-error processing on the additional damping control signal from multiple aspects such as control frequency band, mutation anti-error, step output, limiting clipping, and suppression effect to ensure that the damping control system continuously and stably outputs safe and effective control signals to the station side, thereby achieving damping optimization of the new energy station. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 The block diagram of the design of the broadband oscillation damping control system integrating multiple error prevention measures proposed by the present invention;

[0054] Figure 2 Schematic diagram of a wind farm to which a broadband oscillation damping control system is connected in an embodiment of the present invention;

[0055] Figure 3 This is a flow chart of signal processing of a damping controller in an embodiment of the present invention;

[0056] Figure 4 Schematic diagram showing various intermediate quantity signals in an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only embodiments of a part of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0058] The present invention proposes a broadband oscillation damping control system integrating multiple error prevention measures, which is installed in new energy stations, such as Figure 1 As shown, it includes a damping controller and a compensating converter. The damping controller takes the grid-connected bus voltage, the grid-connected bus current and the compensating current output by the compensating converter as input signals. The damping controller outputs a compensating current reference value to the compensating converter. The compensating current output by the compensating converter is injected into the grid-connected bus of the new energy station.

[0059] In the damping controller, a compensation current command is generated according to the oscillation characteristics of the input signal, and whether the damping controller is unlocked or locked is determined according to the input signal; when the damping controller switches from locked to unlocked or from unlocked to locked, the generated compensation current command is subjected to uniform climbing processing or uniform descending processing; when the amplitude of the processed compensation current command exceeds the limit, the processed compensation current command is corrected and used as the compensation current reference value; otherwise, the processed compensation current command is used as the compensation current reference value.

[0060] In the embodiment, Figure 1 and Figure 2 As shown, each wind turbine in the #1 wind farm is connected to the 35kV bus through a low-voltage transformer T1 (0.69kV / 35kV), a #1 collector or a #2 collector, and a high-voltage transformer (35kV / 220kV) is passed between the 35kV bus and the 220kV bus; according to the above wiring method, the 220kV bus is also connected to the #2 wind farm and the #3 wind farm, and the 220kV bus is connected to the remote power grid. Zg is the transmission line impedance, and the compensation current output by the broadband oscillation damping control system is injected into the 35kV bus; the input signals of the broadband oscillation damping control system include but are not limited to: the voltage and current of the 220kV bus, the voltage and current of the 35kV bus, and the compensation current output by the broadband oscillation damping control system; Figure 1 In the system, the 35kV bus voltage 35kVUabc, the current 35kV Iabc, and the output current Device Iabc of the broadband oscillation damping control system are used as the input signals of the broadband oscillation damping control system; the damping controller outputs the compensation current reference value I to the compensation converter. abc '.

[0061] Specifically, in the damping controller, a compensation current instruction is generated according to the oscillation characteristics of the input signal, including:

[0062] Sampling the grid-connected bus voltage and grid-connected bus current, and obtaining the frequency spectrum of the grid-connected bus voltage and grid-connected bus current through fast Fourier transform;

[0063] Based on the frequency spectrum of the grid-connected bus voltage and grid-connected bus current, the oscillation frequency is extracted by using the extreme point determination method, and the oscillation amplitude at the oscillation frequency is determined by using the spectrum line interpolation method;

[0064] When the oscillation amplitude at the oscillation frequency exceeds the set threshold value (which can be set to 2% of the rated value), it is determined that oscillation occurs and the damping controller is started;

[0065] In the embodiment, the threshold value is set to 2% of the rated value;

[0066] After the damping controller is started, the grid-connected bus current is filtered through an industrial frequency filter to remove the industrial frequency component; the grid-connected bus current after filtering out the industrial frequency component is passed through a bandpass filter to obtain the current within the target control frequency band; the current within the target control frequency band is subjected to proportional phase shifting to obtain a compensation current instruction; in the embodiment, the target control frequency band is [4,20] Hz.

[0067] In the embodiment, the compensation current reference value is a control signal generated by extracting a real-time oscillation signal based on a measured signal of an oscillation in a reaction station, and processing the proportional and phase shifting. The damping controller used in the system collects the 35kV bus voltage and station current, and collects the output current of the equipment body, and generates corresponding control instructions according to the oscillation signal through a preset control strategy. The process of starting the output of the damping controller is that the damping controller first extracts the oscillation signal, determines that the oscillation occurs, starts the adjustment, and outputs the control instruction. The process of judging the occurrence of oscillation is as follows: high-frequency sampling of the 35kV bus voltage, station current and the current output by the damping system itself is performed, and spectrum information is obtained through fast Fourier transform. The oscillation frequency is extracted by judging the extreme point, and the accurate oscillation frequency and oscillation amplitude are obtained by spectrum line interpolation. If the oscillation voltage signal extracted from the 35kV bus voltage exceeds the set voltage start threshold value, or the oscillation current signal extracted from the station current exceeds the set current start threshold value, it is considered that the wind farm has oscillated and the adjustment is started; because the on-site current oscillation characteristics are more sensitive, the preset control strategy is to control the direction of the damping system output current through phase shifting based on the direction of the station current, and inject it into the low-voltage side of the main transformer, so that the wind farm presents a positive resistance characteristic to the outside. The specific implementation is to filter the wind farm current through the power frequency filter to remove the power frequency component, and then obtain the current of the target control frequency band through the bandpass filter, and finally obtain the control current through proportional phase shifting.

[0068] Specifically, determining whether the damping controller is unlocked or locked according to the input signal includes:

[0069] 1) Oscillation characteristic identification, specifically: when the grid-connected bus voltage or grid-connected bus current oscillates, and the oscillation frequency is within the set target control frequency band and the oscillation amplitude is within the set threshold value, the damping controller unlocking signal based on the oscillation characteristic identification is set to 1, otherwise the damping controller unlocking signal based on the oscillation characteristic identification is set to 0;

[0070] In the embodiment, when an oscillation signal within the control frequency band is detected in the bus voltage or the station current, and the oscillation amplitude reaches a certain level, the output of the damping control system is unlocked; when the frequency of the oscillation signal is not within the target control frequency band, the signal output is locked to avoid adverse effects; since the damping control strategy is designed for a specific target control frequency band, if an oscillation occurs within a non-target control frequency band, the control strategy will fail and may even have a bad effect. Therefore, locking measures are designed after oscillation occurs in the non-target control frequency band. When an oscillation signal within the non-control frequency band is extracted from the 35kV bus voltage or the station current, the control signal output is locked to avoid adverse effects.

[0071] 2) Grid current mutation judgment, specifically: when the real-time sampling value of the grid current has a mutation, the damping controller unlocking signal based on the grid current mutation judgment is set to 0, otherwise the damping controller unlocking signal based on the grid current mutation judgment is set to 1;

[0072] In the embodiment, if the real-time sampling value of the station current suddenly changes, due to the influence of the filter, an impure signal will be generated, and the output will be locked within the filter response time. According to the above description of the control strategy for generating the compensation current command, since the filter is used in the control strategy, when the original sampling signal undergoes a large mutation, the filter output will generate a non-ideal control signal within the response time, causing the converter to overcurrent or even the injected signal to have an adverse effect on the wind farm. Therefore, a locking measure is designed when the instantaneous sampling value suddenly changes, as follows:

[0073] The power frequency effective value of the three-phase current of the grid-connected bus is calculated using the sampling value of the three-phase current of the grid-connected bus, which satisfies the following relationship:

[0074]

[0075] In the formula, i a (k), i b (k), i c (k) is the kth sampling sample of the three-phase current of the grid-connected busbar, N is the total number of sampling points within the whole cycle of the power frequency, i rms_a 、i rms_b 、i rms_c It is the power frequency effective value of the three-phase current of the grid-connected bus;

[0076] When the power frequency effective value of any phase current of the grid-connected bus changes more than 0.2 times the rated value within two judgment intervals, the damping controller is locked. The time of locking the damping controller is set in combination with the response time of the filter. In this embodiment, the power frequency filter is a 14-order point-stop filter with a response time of 1000ms. Therefore, when a sudden change in the bus current is detected, the damping controller performs a 1000ms locking output to ensure that under any working condition, the damping control system outputs a pure suppression signal.

[0077] 3) Suppression effect judgment, specifically: when the compensation current output by the damping controller is a positive resistance characteristic, the damping controller unlocking signal based on the suppression effect judgment is set to 1, otherwise the damping controller unlocking signal based on the suppression effect judgment is set to 0;

[0078] In the embodiment, the resistance characteristic of the compensation current output by the wide-band oscillation damping control system is detected in real time, and if the device outputs a negative resistance characteristic signal, the output is locked;

[0079] As a suppression device that provides additional positive resistance characteristics, the broadband oscillation damping control system requires the device body to output a positive resistance signal to ensure that it plays a positive role. Therefore, a protection measure is designed to lock the output of the damping controller when the broadband oscillation damping control system outputs a compensation current with a negative resistance characteristic. The specific implementation is: the broadband oscillation damping control system collects the output compensation current in real time and calculates the resistance characteristics of the compensation current. When the output compensation current has a negative resistance characteristic, the damping controller is locked.

[0080] The detection method of the resistance characteristic of the compensation current is as follows:

[0081] The grid-connected bus voltage and compensation current are sampled, and the frequency spectrum of the grid-connected bus voltage and compensation current is obtained by fast Fourier transform;

[0082] Based on the frequency spectrum of the grid-connected bus voltage and compensation current, the extreme point is determined by the spectrum line extreme value method, and the voltage phasor at each frequency point is determined by the interpolation algorithm in the frequency domain. and current phasor j represents the jth frequency point, j = 1, ..., m, m is the total number of frequency points;

[0083] The positive-sequence voltage phasor at each frequency point is calculated using the voltage phasor at each frequency point, the positive-sequence current phasor at each frequency point is calculated using the current phasor at each frequency point, and the positive-sequence impedance phasor at each frequency point and the positive-sequence current phasor at each frequency point are calculated; when the real part of the positive-sequence impedance phasor at the j-th frequency point is less than zero, it is determined that the positive-sequence resistance at the j-th frequency point presents a negative resistance characteristic; otherwise, it is determined that the positive-sequence resistance at the j-th frequency point presents a positive resistance characteristic;

[0084] The negative-sequence voltage phasor at each frequency point is calculated using the voltage phasor at each frequency point, the negative-sequence current phasor at each frequency point is calculated using the current phasor at each frequency point, and the negative-sequence impedance phasor at each frequency point and the negative-sequence current phasor at each frequency point are calculated; when the real part of the negative-sequence impedance phasor at the j-th frequency point is less than zero, it is determined that the negative-sequence resistance at the j-th frequency point presents a negative resistance characteristic; otherwise, it is determined that the negative-sequence resistance at the j-th frequency point presents a positive resistance characteristic;

[0085] When the positive-sequence resistance or the negative-sequence resistance at the jth frequency point presents a negative resistance characteristic, the damping controller is locked; otherwise, the damping controller is unlocked.

[0086] When the damping controller unlocking signals corresponding to the above three items are all 1, it is determined that the damping controller is unlocked; otherwise, it is determined that the damping controller is locked.

[0087] In the embodiment, when the damping controller is locked, the compensation current command generated by the damping controller is set to zero.

[0088] When the compensation current instruction is output, the characteristics of the power electronic converter are taken into consideration. When the compensation current instruction is directly set to 0 from a large value or directly changes from 0 to a large value, it is easy to cause overcurrent protection of the converter. Therefore, the processing of the anti-error measures also considers the uniform climbing and descending of the signal at the moment when the instruction signal is locked and unlocked; in addition, in view of the possible waveform distortion caused by peak clipping after the control signal reaches the limit value, a variable gain adjustment measure is added. After being processed by multiple anti-error measures, the final instruction current is formed and injected into the compensation converter. The system proposed in the present invention designs multiple anti-error measures based on the requirements of the compensation converter for the output signal and the requirements of the damping controller control strategy design.

[0089] The compensation converter used in the damping control system is a high-voltage cascade power electronic converter. To avoid damage to the equipment due to converter overvoltage or overcurrent, the injected control signal is required to rise or fall slowly and cannot jump in a step. Therefore, when the damping controller switches from locking to unlocking or from unlocking to locking, the compensation current command is processed uniformly by climbing or descending; the details are as follows:

[0090] When the damping controller switches from locking to unlocking, the compensation current command is subjected to uniform climbing processing, including: within a set time period, the value of the compensation current command is increased from 0 to the amplitude of the compensation current command generated according to the oscillation characteristics of the input signal; in a non-limiting preferred embodiment, a linear fitting method is used to determine the uniform climbing constraint model of the compensation current command;

[0091] The compensation current command after uniform ramp processing satisfies the following relationship:

[0092]

[0093] In the formula, I r ' ef is the compensation current command at time t after uniform ramp processing, I ref is the compensation current command generated according to the oscillation characteristics of the input signal, t s ,t e are the starting time and ending time of the set time period of uniform climbing processing respectively;

[0094] When the damping controller switches from unlocking to locking, the compensation current command is subjected to uniform slope reduction processing, including: within a set time period, the value of the compensation current command is reduced from the amplitude of the compensation current command generated according to the oscillation characteristics of the input signal to 0; in a non-limiting preferred embodiment, a linear fitting method is used to determine the uniform slope reduction constraint model of the compensation current command;

[0095] The compensation current command after uniform slope reduction satisfies the following relationship:

[0096]

[0097] In the formula, I r ″ ef is the compensation current command at time t after uniform slope reduction, I ref is the compensation current command generated according to the oscillation characteristics of the input signal, t s ,t e They are respectively the starting time and the ending time of the set time period for the uniform slope reduction process;

[0098] In the embodiment, in order to meet the requirement that the control signal cannot jump in a step-like manner, when the control signal changes from the locked output to the unlocked output, the compensation current instruction changes from the current value of 0 to the larger value at the next moment. To avoid sudden changes, a uniform ramp-down process is performed within a specified time (such as 200 milliseconds), and the real-time value of the compensation current instruction is proportionally scaled according to the proportion of the current output moment in the specified time period (such as 200 milliseconds) to generate an actual control instruction. After 200 milliseconds, the control instruction is output according to the compensation current instruction. Similarly, when the control signal changes from the unlocked output to the locked output, the compensation current instruction changes from the larger value at the current moment to the value of 0 at the next moment. To avoid sudden changes, a uniform ramp-down process is performed within a specified time (such as 200 milliseconds), and the current reference value at the locking moment is proportionally scaled according to the proportion of the current output moment in the time period (such as 200 milliseconds) to be uniformly reduced to 0.

[0099] The compensation converter used in the damping control system is selected according to the required capacity, and the injected control signal cannot exceed the capacity limit to avoid converter damage. Therefore, when the processed compensation current command exceeds the limit, the compensation current command is corrected and used as the compensation current reference value; otherwise, the processed compensation current command is used as the compensation current reference value; the details are as follows:

[0100] When the processed compensation current instruction is less than the limit value, the instantaneous value of the processed compensation current instruction is used as the compensation current reference value; when the processed compensation current instruction is greater than the limit value, the ratio between the limit value and the amplitude of the compensation current instruction is used as the correction factor, and the product between the correction factor and the instantaneous value of the processed compensation current instruction is used as the compensation current reference value; in the embodiment, the limit value is 1pu;

[0101] In the embodiment, in order to meet the requirement that the compensation current instruction must be limited, if the generated compensation current instruction exceeds the limit value, it cannot be directly set to the limit value to cause clipping, which will cause waveform distortion and cause the converter to overcurrent, and even generate signals in the non-controlled frequency band to be injected into the station. To solve this problem, a variable gain adjustment measure based on the real-time oscillation amplitude is designed to detect the amplitude of the compensation current instruction in real time. After reaching the limit value, a proportional factor is generated based on the current amplitude and the limit value. The compensation current instruction is multiplied by the proportional factor as the actual current reference value to ensure that when the compensation current instruction exceeds the limit value, a standard sinusoidal signal with an amplitude of the limit value can still be output. The specific implementation process is as follows:

[0102] Get the instantaneous value i of the compensation current command at the current time t after processing out_a (t), i out_b (t), i out_c (t), the amplitude of the compensation current command at the current moment t is calculated using the following relationship:

[0103]

[0104] In the formula, i amp (t) is the amplitude of the compensation current instruction at the current moment t;

[0105] If the amplitude i of the compensation current command at the current time t is amp (t) not greater than the limit value I lim , then the instantaneous value i of the compensation current instruction at the current time t after processing is out_a (t), i out_b (t), i out_c (t) is the compensation current instruction i sent by the damping controller to the compensation converter ref_a (t), i ref_b (t), i ref_c (t);

[0106] If the amplitude i of the compensation current command at the current time t is amp (t) is greater than the limit value I lim , then the limit value I lim The amplitude i of the compensation current command at the current time t amp (t) is used as the correction factor, and the compensation current instruction i sent by the damping controller to the compensation converter is ref_a (t), i ref_b (t), i ref_c (t) satisfies the following relationship:

[0107] i ref_a (t) = k × i out_a (t)

[0108] i ref_b (t) = k × i out_b (t)

[0109] i ref_c (t) = k × i out_c (t)

[0110] In the formula, k is the correction factor, satisfying k = I lim i amp (t).

[0111] The present invention also proposes a broadband oscillation damping control method integrating multiple error prevention measures, comprising:

[0112] Collecting the grid-connected bus voltage, grid-connected bus current and compensation current output by the compensation converter as input signals of the damping controller;

[0113] The damping controller generates a compensation current command according to the oscillation characteristics of the input signal, and determines whether the damping controller is unlocked or locked according to the input signal;

[0114] When the damping controller switches from locking to unlocking, the generated compensation current instruction is subjected to uniform climbing processing, and when the damping controller switches from unlocking to locking, the generated compensation current instruction is subjected to uniform descending processing; when the amplitude of the processed compensation current instruction exceeds the limit, the processed compensation current instruction is corrected and used as the compensation current reference value; otherwise, the processed compensation current instruction is used as the compensation current reference value;

[0115] The damping controller outputs a compensation current reference value to the compensation converter; according to the compensation current reference value, the compensation current output by the compensation converter is injected into the grid-connected bus of the new energy station.

[0116] According to Figure 3The control process shown in the figure performs high-frequency synchronous sampling of the three-phase voltage, three-phase current, 35kV bus voltage, low-voltage side current of the main transformer, and compensation current output by the damping control system converter of a new energy station, with a sampling rate of 12800Hz. The sampling position determines the positive direction of the current according to the outflow bus.

[0117] Perform FFT spectrum calculation on the collected data to calculate the oscillation characteristic quantity (including oscillation frequency, oscillation amplitude and oscillation impedance). Figure 4 As shown, at 14.3 seconds, an oscillation component with an oscillation frequency of 8 Hz and an oscillation amplitude of 0.05 pu was detected in the current on the low-voltage side of the main transformer; there was also an oscillation component of 8 Hz in the bus voltage, and the oscillation amplitude was 0.01 pu.

[0118] Since the oscillation current component is greater than the oscillation threshold value 0.02pu and the oscillation frequency is 8Hz, within the target control frequency band, the unlocking signal of the damping controller based on oscillation feature identification is set to 1.

[0119] At 14.3 seconds, due to the sudden change of the current on the low-voltage side of the main transformer, the unlocking signal of the damping controller based on the grid-connected current sudden change blocking is set to 0, that is, the sudden change blocking signal is set to 1 and remains set for 1 second. During this period, it can be seen that the calculated value of the control command transitions from the distorted signal at the moment of the sudden change to a smooth signal.

[0120] After a delay of 1 second, the unlocking signal of the damping controller based on the grid-connected current mutation blocking is set to 1. The current damping controller has not unlocked the output. The unlocking signal of the damping controller based on the suppression effect judgment is set to 1 by default. Combined with the current unlocking signal of the damping controller based on oscillation feature identification is 1, the damping controller is unlocked and the output is turned on.

[0121] The damping controller output gradually increases from 0, and the amplitude of the control command calculation value is detected in real time. Since the amplitude of the calculation value reaches 2pu, which exceeds the converter limit value of 1pu, the actual output value at any moment selects the command calculation value at the current moment multiplied by 0.5 as the final value. The actual output value is a smooth sinusoidal signal that reaches the limit value of 1pu.

[0122] After the damping controller starts outputting, there is an oscillating current component with an amplitude of 8Hz and 1pu in the collected compensation current signal. The resistance characteristics of the damping control system are calculated in real time, and the damping control system outputs a positive-sequence component. The calculated positive-sequence resistance amplitude is 0.01pu and the angle is 60 degrees. The damping control system outputs a positive resistance signal to the outside. The unlocking signal of the damping controller based on the suppression effect judgment is set to 1, and the damping controller continues to output.

[0123] Existing broadband oscillation suppression-related technologies mainly focus on the optimization and improvement of control strategies, such as how to accurately extract oscillation characteristic information and how to design control strategies for better robustness. The present invention proposes a protection measure that comprehensively considers the characteristics of the power electronic converter and the control effect when outputting after the control signal is generated, and performs multiple locking designs. Targeted anti-error designs are carried out from multiple aspects such as the applicable frequency band of the control strategy, the smooth transition of the control signal, the purification processing, the peak clipping processing, and the verification of the effectiveness of the suppression effect, to ensure that the control current actually injected into the grid side is a reliable, safe, and effective suppression signal under any working conditions, thereby realizing broadband oscillation damping control of new energy sites.

[0124] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0125] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0126] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0127] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A broadband oscillation damping control system integrating multiple error prevention measures, It is characterized in that It includes: a damping controller and a compensating converter; the damping controller takes the grid-connected bus voltage, the grid-connected bus current and the compensating current output by the compensating converter as input signals, and the damping controller outputs a compensating current reference value to the compensating converter; according to the compensating current reference value, the compensating current output by the compensating converter is injected into the grid-connected bus of the new energy station; In the damping controller, a compensation current command is generated according to the oscillation characteristics of the input signal, and whether the damping controller is unlocked or locked is determined according to the input signal; when the damping controller switches from locked to unlocked, the generated compensation current command is subjected to uniform climbing processing, and when the damping controller switches from unlocked to locked, the generated compensation current command is subjected to uniform descending processing; when the amplitude of the processed compensation current command exceeds the limit, the processed compensation current command is corrected and used as the compensation current reference value; otherwise, the processed compensation current command is used as the compensation current reference value.

2. The broadband oscillation damping control system integrating multiple error prevention measures according to claim 1 is characterized in that: In the damping controller, a compensation current command is generated according to the oscillation characteristics of the input signal, including: The input signal is sampled and the spectrum of the input signal is obtained by fast Fourier transform; Based on the spectrum of the input signal, the extreme point determination method is used to extract the oscillation frequency, and the spectrum line interpolation method is used to determine the oscillation amplitude at the oscillation frequency; When the oscillation amplitude at the oscillation frequency exceeds the set threshold value, it is determined that oscillation occurs and the damping controller is started; After the damping controller is started, the grid-connected bus current is filtered through the power frequency filter to remove the power frequency component; the grid-connected bus current after the power frequency component is filtered out is passed through a bandpass filter to obtain the current within the target control frequency band; the current within the target control frequency band is subjected to proportional phase shifting to obtain the compensation current instruction.

3. The broadband oscillation damping control system integrating multiple error prevention measures according to claim 2 is characterized in that: The threshold value is set to 2% of the rated value; the target control frequency band is [4,20] Hz.

4. The broadband oscillation damping control system integrating multiple error prevention measures according to claim 2 is characterized in that: Determine whether the damping controller is unlocked or locked according to the input signal, including: 1) Oscillation characteristic identification, specifically: when the grid-connected bus voltage or grid-connected bus current oscillates, and the oscillation frequency is within the set target control frequency band and the oscillation amplitude exceeds the set threshold value, the damping controller unlocking signal based on the oscillation characteristic identification is set to 1, otherwise the damping controller unlocking signal based on the oscillation characteristic identification is set to 0; 2) Grid current mutation judgment, specifically: when the real-time sampling value of the grid current has a mutation, the damping controller unlocking signal based on the grid current mutation judgment is set to 0, otherwise the damping controller unlocking signal based on the oscillation characteristic identification is set to 1; 3) Suppression effect judgment, specifically: when the compensation current output by the damping controller is a positive damping characteristic, the damping controller unlocking signal based on the suppression effect judgment is set to 1, otherwise the damping controller unlocking signal based on the suppression effect judgment is set to 0; When the damping controller unlocking signals corresponding to the above three items are all 1, it is determined that the damping controller is unlocked; otherwise, it is determined that the damping controller is locked.

5. The broadband oscillation damping control system integrating multiple error prevention measures according to claim 4 is characterized in that: The power frequency effective value of the three-phase current of the grid-connected bus is calculated using the sampling value of the three-phase current of the grid-connected bus, which satisfies the following relationship: In the formula, i a (k), i b (k), i c (k) is the kth sampling sample of the three-phase current of the grid-connected busbar, N is the total number of sampling points within the whole cycle of the power frequency, i rms_a 、i rms_b 、i rms_c It is the power frequency effective value of the three-phase current of the grid-connected bus; When the power frequency effective value of any phase current of the grid-connected bus changes more than 0.2 times the rated value within two judgment intervals, the unlocking signal of the damping controller based on the grid-connected current mutation judgment is set to 0 to lock the damping controller; On the contrary, the damping controller unlocking signal based on oscillation characteristic identification is set to 1 to unlock the damping controller.

6. The broadband oscillation damping control system integrating multiple error prevention measures according to claim 4 is characterized in that: The grid-connected bus voltage and compensation current are sampled, and the frequency spectrum of the grid-connected bus voltage and compensation current is obtained by fast Fourier transform; Based on the frequency spectrum of the grid-connected bus voltage and compensation current, the extreme point is determined by the spectrum line extreme value method, and the voltage phasor at each frequency point is determined by the interpolation algorithm in the frequency domain. and current phasor j represents the jth frequency point, j = 1, ..., m, m is the total number of frequency points; The positive-sequence voltage phasor at each frequency point is calculated using the voltage phasor at each frequency point, the positive-sequence current phasor at each frequency point is calculated using the current phasor at each frequency point, and the positive-sequence impedance phasor at each frequency point and the positive-sequence current phasor at each frequency point are calculated; when the real part of the positive-sequence impedance phasor at the j-th frequency point is less than zero, it is determined that the positive-sequence resistance at the j-th frequency point presents a negative resistance characteristic; otherwise, it is determined that the positive-sequence resistance at the j-th frequency point presents a positive resistance characteristic; The negative-sequence voltage phasor at each frequency point is calculated using the voltage phasor at each frequency point, the negative-sequence current phasor at each frequency point is calculated using the current phasor at each frequency point, and the negative-sequence impedance phasor at each frequency point and the negative-sequence current phasor at each frequency point are calculated; when the real part of the negative-sequence impedance phasor at the j-th frequency point is less than zero, it is determined that the negative-sequence resistance at the j-th frequency point presents a negative resistance characteristic; otherwise, it is determined that the negative-sequence resistance at the j-th frequency point presents a positive resistance characteristic; When the positive sequence resistance or negative sequence resistance at the jth frequency point presents a negative resistance characteristic, the unlocking signal of the damping controller based on the suppression effect judgment is set to 0 to lock the damping controller; Otherwise, the damping controller unlocking signal based on the suppression effect judgment is set to 1 to unlock the damping controller.

7. The broadband oscillation damping control system integrating multiple error prevention measures according to claim 4 is characterized in that: When the damping controller is locked, the compensation current command generated by the damping controller is set to 0.

8. The broadband oscillation damping control system integrating multiple error prevention measures according to claim 7 is characterized in that: When the damping controller switches from locking to unlocking, the compensation current command is subjected to uniform ramp-up processing, including: within a set time period, the value of the compensation current command increases from 0 to the amplitude of the compensation current command generated according to the oscillation characteristics of the input signal; the compensation current command after the uniform ramp-up processing satisfies the following relationship: In the formula, I r ' ef is the compensation current command at time t after uniform ramp processing, I ref is the compensation current command generated according to the oscillation characteristics of the input signal, t s ,t e are the starting time and the ending time of the set time period of the uniform climbing process respectively; When the damping controller switches from unlocking to locking, the compensation current command is subjected to uniform slope reduction processing, including: within a set time period, the value of the compensation current command is reduced from the amplitude of the compensation current command generated according to the oscillation characteristics of the input signal to 0; the compensation current command after the uniform slope reduction processing satisfies the following relationship: In the formula, I r ″ ef is the compensation current command at time t after uniform slope reduction, I ref is the compensation current command generated according to the oscillation characteristics of the input signal, t s ,t e They are respectively the starting time and the ending time of the set time period for the uniform slope reduction process.

9. The broadband oscillation damping control system integrating multiple error prevention measures according to claim 8, characterized in that: When the processed compensation current instruction is less than the limit value, the instantaneous value of the processed compensation current instruction is used as the compensation current reference value; when the processed compensation current instruction is greater than the limit value, the ratio between the limit value and the amplitude of the compensation current instruction is used as the correction factor, and the product of the correction factor and the instantaneous value of the processed compensation current instruction is used as the compensation current reference value, and the limit value is 1pu; the specific implementation process is as follows: Get the instantaneous value i of the compensation current command at the current time t after processing out_a (t), i out_b (t), i out_c (t), the amplitude of the compensation current command at the current moment t is calculated using the following relationship: In the formula, i amp (t) is the amplitude of the compensation current instruction at the current moment t; If the amplitude i of the compensation current command at the current time t is amp (t) not greater than the limit value I lim , then the instantaneous value i of the compensation current instruction at the current moment t after processing is out_a (t), i out_b (t), i out_c (t) is the compensation current instruction i sent by the damping controller to the compensation converter ref_a (t), i ref_b (t), i ref_c (t); If the amplitude i of the compensation current command at the current time t is amp (t) is greater than the limit value I lim , then the limit value I lim The amplitude i of the compensation current command at the current time t amp (t) is used as the correction factor, and the compensation current instruction i sent by the damping controller to the compensation converter is ref_a (t), i ref_b (t), i ref_c (t) satisfies the following relationship: i ref_a (t)=k×i out_a (t) i ref_b (t)=k×i out_b (t) i ref_c (t)=k×i out_c (t) In the formula, k is the correction factor, satisfying k = I lim i amp (t).

10. A broadband oscillation damping control method integrating multiple error prevention measures, characterized in that: include: Collecting the grid-connected bus voltage, grid-connected bus current and compensation current output by the compensation converter as input signals of the damping controller; The damping controller generates a compensation current command according to the oscillation characteristics of the input signal, and determines whether the damping controller is unlocked or locked according to the input signal; When the damping controller switches from locking to unlocking, the generated compensation current command is subjected to uniform climbing processing, and when the damping controller switches from unlocking to locking, the generated compensation current command is subjected to uniform descending processing; When the amplitude of the processed compensation current instruction exceeds the limit, the processed compensation current instruction is corrected and used as a compensation current reference value; Otherwise, the processed compensation current instruction is used as the compensation current reference value; The damping controller outputs a compensation current reference value to the compensation converter; According to the compensation current reference value, the compensation current output by the compensation converter is injected into the grid-connected bus of the new energy station.

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