CN117498355A - Filter design method and system suitable for offshore wind farm harmonic characteristics - Google Patents
Filter design method and system suitable for offshore wind farm harmonic characteristics Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/01—Arrangements for reducing harmonics or ripples
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00001—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by the display of information or by user interaction, e.g. supervisory control and data acquisition systems [SCADA] or graphical user interfaces [GUI]
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00002—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by monitoring
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00032—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/10—Power transmission or distribution systems management focussing at grid-level, e.g. load flow analysis, node profile computation, meshed network optimisation, active network management or spinning reserve management
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/28—The renewable source being wind energy
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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Abstract
The invention discloses a filter design method and a system suitable for the harmonic characteristics of an offshore wind farm, and relates to the technical field of offshore wind power, comprising the steps of collecting operation data and primary equipment parameters of the offshore wind farm, preprocessing, determining the limit value of the electric energy quality index of the offshore wind farm, selecting a proper type of filter, and calculating and obtaining the parameters of the filter; selecting a proper electronic element design circuit and testing the performance of the filter; and monitoring the performance of the filter, and maintaining and adjusting according to the monitoring result to ensure the effectiveness of the filter. According to the invention, the actual power grid operation mode change is considered, after the control of the designed active filter, the grid-connected point harmonic current index of the sea wind power plant can meet the national standard requirement, when the background harmonic voltage of the wind power plant before operation does not exceed the limit value, the control meets the national standard requirement, and when the background harmonic voltage exceeds the limit value, the control can restore the background harmonic level of the wind power plant before operation.
Description
Technical Field
The invention relates to the technical field of offshore wind power, in particular to a filter design method and a system suitable for harmonic characteristics of an offshore wind farm.
Background
The main harmonic source of the power system is a constant current source, the main characteristic of the constant current source is that the current value is unchanged when the external impedance changes, the external impedance of the harmonic source is the impedance of the parallel connection of the inductive impedance of the power system and the capacitive impedance of the capacitor, the distribution of harmonic currents entering the power system and the capacitor is different due to the difference of harmonic times, the parallel capacitor used for reactive compensation in the power supply system can generate over-voltage to cause damage if the parallel resonance occurs between a certain harmonic and the inductive system reactance, the generation of the offshore wind power resonance is the result of matching the inductive reactance of the system with the capacitive reactance of the cable to the ground capacitor at a specific frequency, therefore, when the harmonic for the specific frequency is over-standard due to the resonance effect, the impedance parameter of the system is changed through the series reactance, the frequency of the parallel resonance point, which is over-standard by the harmonic, is moved to other frequency with smaller influence, the aim of inhibiting the harmonic over-standard can be achieved, and the adoption of the harmonic current generated by the harmonic source is an effective measure of inhibiting the harmonic pollution.
At present, a 'passive' alternating current filter device is generally adopted, and harmonic sources are connected in parallel in operation, so that the reactive compensation is required in addition to the filtering effect, the active harmonic compensation device realizes reactive power compensation, harmonic compensation and the like of a power grid by controlling the amplitude and the phase of the output voltage of an inverter, the compensation capacity of the active harmonic compensation device is dependent on the type of harmonic characteristics of loads, and the compensation capacity of equipment for the harmonic waves of the loads with higher harmonic content is determined according to specific load waveform factors because waveform distortion is serious, and peak current is higher, if calculation compensation is carried out according to a current effective value without limitation, the peak overcurrent of IGBT is easy to be caused.
Disclosure of Invention
In view of the problems of the existing filter design method suitable for the harmonic characteristics of the offshore wind farm, the invention provides the method for optimizing the configuration scheme of the offshore wind farm harmonic resonance treatment by taking the current situation of the offshore wind farm harmonic problem and the operation state of the distant view planning into consideration, constructing a harmonic resonance simulation analysis model, selecting a proper harmonic treatment method through the simulation of electromagnetic transient simulation software and analyzing the basic principle of the remote active compensation of the harmonic.
Therefore, the problem to be solved by the present invention is how to provide a filter design method and system suitable for the harmonic characteristics of offshore wind farms.
In order to solve the technical problems, the invention provides the following technical scheme:
in a first aspect, an embodiment of the present invention provides a filter design method suitable for a harmonic characteristic of an offshore wind farm, which includes collecting operation data and primary equipment parameters of the offshore wind farm, preprocessing the operation data, analyzing the collected operation data, determining a limit value of an electric energy quality index of the offshore wind farm, selecting a filter of a proper type, and calculating to obtain filter parameters; selecting an electronic element suitable for design to design a filter circuit according to the calculated filter parameters, testing the performance of the filter, and installing the designed filter; the performance of the filter is monitored regularly, maintenance and adjustment are carried out according to the monitoring result, the effectiveness of the filter is ensured, the performance data of the filter is recorded, and a report is generated for analysis and maintenance.
As a preferred embodiment of the filter design method for the harmonic characteristics of the offshore wind farm according to the present invention, the filter design method comprises: the operation data comprise current, voltage data, normal operation and abnormal situation data; the preprocessing includes removing noise and outliers; the primary equipment parameters comprise main wiring, sea cables, overhead lines, offshore boost transformers, wind turbines and other primary equipment.
As a preferred embodiment of the filter design method for the harmonic characteristics of the offshore wind farm according to the present invention, the filter design method comprises: the electric energy quality index limit value comprises a public connection point which meets the public power grid harmonic voltage limit value, and the harmonic current is lower than a specified allowable value when a user injects into the public connection point; specifically, when the minimum short-circuit capacity at the public connection point is different from the corresponding reference capacity, the allowable value of the harmonic current is corrected, and the calculation formula is as follows:
I h ＝S k1 /S k2 ×I hp
wherein S is k1 Minimum short circuit capacity for common connection point; s is S k2 Is the reference short circuit capacity; i hp The allowable value of the h harmonic current in the table is as follows; i h For short circuit capacity S k1 The h harmonic current allowable value; harmonic current allowable value I injected into power grid by each user of same public connection point hi The distribution is carried out according to the ratio of the protocol capacity of the user to the capacity of the power supply equipment of the public connection point, and the calculation formula is as follows:
I hi ＝I n (S i /S t ) 1/a
wherein I is n Is the permitted value of the nth harmonic current; s is S i Power utilization protocol capacity for the ith user; s is S t Power supply equipment capacity for the common connection point; a is the phase superposition coefficient.
As a preferred embodiment of the filter design method for the harmonic characteristics of the offshore wind farm according to the present invention, the filter design method comprises: the filter comprises a passive filter and an active filter, and the passive filter adopts an inductance series capacitance mode to realize the filtering effect on harmonic waves; the active filter HAPF adopts a mode of dynamically restraining harmonic waves and compensating reactive power to flexibly adjust a compensation mode and a compensation frequency band, so as to realize the filtering effect on the harmonic waves; the HAPF control system consists of two parts, namely harmonic current detection and compensation current tracking, wherein the current control mode is divided into a direct current control mode and an indirect current control mode, a main circuit adopts a PWM converter, and when a power grid charges a capacitor at the direct current side of the device, the main circuit works in a rectification state; when the device sends compensation current to the power grid, the main circuit works in an inversion state, and the HAPF working principle is as follows:
i s ＝i L +i c
i L ＝i L1 +i Lh
i c ＝-i Lh
i s ＝i L +i c ＝i L1
wherein i is s Is the grid current, i L Is the load current, i c Is the compensation current, i L1 Is the fundamental component of the grid current and i is the harmonic component.
As a preferred embodiment of the filter design method for the harmonic characteristics of the offshore wind farm according to the present invention, the filter design method comprises: the HAPF adopts CPS-SPWM (Single-stage frequency-doubling carrier phase-shift pulse width modulation) technology, and specifically comprises the following steps of sm In the converters in cascade connection of H-bridge units, modulated wave signals V with 180 DEG phase difference are used c Taking 2N sm The same frequency and the same amplitude but 2/N phase difference sm Triangular carrier signal V of carrier period r The method comprises the steps of carrying out a first treatment on the surface of the The front axle is compared with the forward modulation wave, the rear axle is compared with the reverse modulation wave to modulate, and 2N is generated sm Rectangular pulse sequences with different columns respectively drive IGBT devices of each H-bridge unit to be conducted;
sampling grid-connected line current according to the actual system control target requirement, obtaining a harmonic current component through a harmonic extraction algorithm, and obtaining a final instruction current signal by making a difference with a reference value;
and generating a modulated wave signal through tracking adjustment of the current inner loop, generating a final IGBT driving signal through PWM carrier phase-shifting modulation, and transmitting the final IGBT driving signal to each electronic element to finish the output control of corresponding current.
As a preferred embodiment of the filter design method for the harmonic characteristics of the offshore wind farm according to the present invention, the filter design method comprises: the electronic element comprises a power valve group, a power unit, a transformer, an isolating switch, a circuit breaker, a current transformer, a voltage transformer, a starting loop and a lightning arrester; the power valve group is selected from an IGBT with a 35 kilovolt H bridge cascade topology at 1700V voltage level, the total module quantity of each phase is determined, and the power unit comprises a direct current capacitor and an IGBT type selection; the transformer selects YNy wiring, a primary neutral point is provided with a protection CT for unbalance protection, and iron core magnetic density and winding adjustment optimization are carried out; the effective current value and the short-circuit current of the isolating switch and the circuit breaker are the same, and the isolating switch with rated current and short-circuit current larger than the requirements is selected; the current transformers comprise 220 kilovolt current transformers and 35 kilovolt current transformers, the 220 kilovolt current transformers comprise electromagnetic current transformers CT1 and CT2, and the 35 kilovolt current transformers comprise electromagnetic current transformers CT3; the voltage transformer is a non-grounding system, when a single-phase short circuit to ground occurs, the short circuit current is the capacitance current to ground, and the voltage to ground is monitored to judge whether the single-phase short circuit to ground occurs or not; when the starting loop is started, the starting switch is switched off, the starting switch is switched on after charging is completed, the APF is unlocked and enters a normal working state, a sleeve-type resistor is selected, and the bottom of the sleeve-type resistor is supported through an insulator; the lightning arrester comprises a 220 kilovolt lightning arrester and a 35 kilovolt lightning arrester, and the lightning impulse withstand voltage, the operation impulse withstand voltage and the residual voltage under the lightning impulse overvoltage of the lightning arrester and the residual voltage under the operation impulse overvoltage of the lightning arrester are determined.
As a preferred embodiment of the filter design method for the harmonic characteristics of the offshore wind farm according to the present invention, the filter design method comprises: the structure and the insulation design determine the outer dimensions of a power frame layer, a single-layer module and a single power frame, A, B, C three phases are sequentially arranged in a container, a wall bushing introduces three-phase incoming wires into the container, neutral points are connected through cables, each power valve group is supported by an insulator, and each phase of incoming cable is introduced into the container through the wall bushing; the heat dissipation design adopts water cooling and air conditioning for compound heat dissipation, the internal circulation of the water cooling system is liquid cooling, and the external circulation is water-air heat exchange; the protection configuration is used for protecting equipment in real time by monitoring the state of a power grid, the external environment quantity, the external switching quantity, the state of a valve group, the communication state and the states of a power supply and a cooling auxiliary machine in real time in the operation process, and when the equipment is abnormal, alarming, device locking and system tripping are executed according to the influence degree and the effect of the abnormality.
In a second aspect, embodiments of the present invention provide a filter design system suitable for use in the harmonic characteristics of an offshore wind farm, comprising: the acquisition module is used for collecting operation data and primary equipment parameters of the offshore wind farm, preprocessing the operation data, analyzing the collected operation data, determining the limit value of the electric energy quality index of the offshore wind farm, selecting a proper type of filter, and calculating and acquiring the filter parameters; the design module is used for selecting electronic elements suitable for design to design a filter circuit according to the calculated filter parameters, testing the performance of the filter and installing the designed filter; the monitoring module is used for periodically monitoring the performance of the filter, maintaining and adjusting according to the monitoring result, ensuring the effectiveness of the filter, recording the performance data of the filter, and generating a report for analysis and maintenance.
In a third aspect, embodiments of the present invention provide a computer apparatus comprising a memory and a processor, the memory storing a computer program, wherein: the processor, when executing the computer program, implements any of the steps of the method described above.
In a fourth aspect, embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, wherein: which when executed by a processor performs any of the steps of the method described above.
The invention has the beneficial effects that.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Wherein:
FIG. 1 is a flow chart of a filter design method suitable for use in the harmonic characteristics of an offshore wind farm.
FIG. 2 is a schematic diagram of an offshore wind farm system.
FIG. 3 is a primary wiring diagram of a filter design method suitable for use in the harmonic characteristics of an offshore wind farm.
Fig. 4 is a schematic diagram of the operation of an active filter of a filter design method suitable for use in the harmonic characteristics of an offshore wind farm.
FIG. 5 is a schematic diagram of harmonic current detection and compensation control for a filter design method suitable for use in offshore wind farm harmonic characterization.
Detailed Description
So that the manner in which the above recited objects, features and advantages of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments, some of which are illustrated in the appended drawings. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present invention is not limited to the specific embodiments disclosed below.
Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
Example 1
Referring to fig. 1, a first embodiment of the present invention provides a filter design method applicable to harmonic characteristics of an offshore wind farm, including:
s1: and collecting operation data and primary equipment parameters of the offshore wind farm, preprocessing the operation data, analyzing the collected operation data, determining the limit value of the electric energy quality index of the offshore wind farm, selecting a proper type of filter, and calculating to obtain the filter parameters.
Specifically, the operation data includes current, voltage data, normal operation and abnormal situation data; preprocessing includes removing noise and outliers; the primary equipment parameters comprise main wiring, sea cables, overhead lines, offshore boost transformers, wind turbines and other primary equipment.
The electric energy quality index limit value comprises a public connection point which meets the public power grid harmonic voltage limit value, and the harmonic current is lower than a specified allowable value when a user injects into the public connection point; specifically, when the minimum short-circuit capacity at the public connection point is different from the corresponding reference capacity, the allowable value of the harmonic current is corrected, and the calculation formula is as follows:
I h ＝S k1 /S k2 ×I hp
wherein S is k1 Minimum short circuit capacity for common connection point; s is S k2 Is the reference short circuit capacity; i hp The allowable value of the h harmonic current in the above formula; i h For short circuit capacity S k1 The h harmonic current allowable value; harmonic current allowable value I injected into power grid by each user of same public connection point hi The distribution is carried out according to the ratio of the protocol capacity of the user to the capacity of the power supply equipment of the public connection point, and the calculation formula is as follows:
I hi ＝I n (S i /S t ) 1/a
wherein I is n Is the permitted value of the nth harmonic current; s is S i Power utilization protocol capacity for the ith user; s is S t Power supply equipment capacity for the common connection point; a is the phase superposition coefficient.
The filter comprises a passive filter and an active filter, and is determined according to the current situation of wind power harmonic level and the power grid parameter variation factor; the passive filter adopts a mode of connecting inductors in series with capacitors to realize the filtering effect on harmonic waves; the active filter HAPF adopts a mode of dynamically restraining harmonic waves and compensating reactive power to flexibly adjust a compensation mode and a compensation frequency band, so as to realize the filtering effect on the harmonic waves; the HAPF control system consists of two parts, namely harmonic current detection and compensation current tracking, wherein the current control mode is divided into a direct current control mode and an indirect current control mode, a main circuit adopts a PWM converter, and when a power grid charges a capacitor at the direct current side of the device, the main circuit works in a rectification state; when the device sends compensation current to the power grid, the main circuit works in an inversion state, and the HAPF working principle is as follows:
i s ＝i L +i c
i L ＝i L1 +i Lh
i c ＝-i Lh
i s ＝i L +i c ＝i L1
wherein i is s Is the grid current, i L Is the load current, i c Is the compensation current, i L1 Is the fundamental component of the grid current and i is the harmonic component.
HAPF valve group adopts CPS-SPWM, which is standard modulation method of H bridge cascade multi-level converter, and is characterized by that it adopts N-type carrier phase shift pulse width modulation technique sm In the converters in cascade connection of H-bridge units, modulated wave signals V with 180 DEG phase difference are used c Taking 2N sm The same frequency and the same amplitude but 2/N phase difference sm Triangular carrier signal V of carrier period r The front axle is compared with the forward modulation wave, the rear axle is compared with the reverse modulation wave to modulate, and 2N is generated sm Rectangular pulse sequences with different columns respectively drive IGBT devices of each H-bridge unit to be conducted; taking actual system control target requirements into consideration, sampling grid-connected line current, obtaining 5 times and 7 times harmonic current components through a harmonic extraction algorithm, then differencing with a reference value to obtain a final command current signal, generating a modulated wave signal through current inner loop tracking adjustment, generating a final IGBT driving signal through PWM carrier phase-shifting modulation, and issuing to each sub-module to finish output control of corresponding current.
The integrated pair of passive filtering and active filtering schemes are shown in table 1.
Table 1 comparison of passive and active filtering schemes
| Contrast item | Passive filtering scheme | Active filtering scheme |
| Filtering characteristics | Fixing | Flexible and flexible |
| Grid parameter variation sensitivity | High height | Low and low |
| Reactive power balance problem | Has the following components | Without any means for |
| Cost investment | Lower level | Higher height |
S2: and selecting an electronic element suitable for design to design a filter circuit according to the calculated filter parameters, testing the performance of the filter, and installing the designed filter.
Specifically, by combining the current level of wind power harmonic waves and the fluctuation of the harmonic conditions of a power grid, comprehensively considering factors such as treatment allowance, investment cost and the like, selecting 2.5 times capacity allowance, and calculating 5 times harmonic compensation capacity of 25.15Mvar and 7 times harmonic compensation capacity of 10.67MVar, wherein 5 times and 7 times harmonic rated currents are 66A and 28A respectively.
Total capacity of the device:
in summary, the total capacity of the final selected device is 30Mvar.
The highest operating value of the low-voltage side line voltage of the power valve bank is calculated to obtain 8.87kV of 5-order harmonic voltage and 5.16kV of 7-order harmonic voltage, and the highest operating value of the low-voltage side line voltage is 39.9kV.
The IGBT with 1700V voltage class most commonly used in engineering by adopting a 35KV H bridge cascade topology is considered, the rated voltage at the direct current side is not more than 950V, the reliability of the power unit is ensured, meanwhile, the unbalance of 1.05 times of the voltage of the power unit is considered, and the minimum number (without redundancy) of the power units in each phase is as followsA +2% redundancy configuration was selected, with a total number of modules per phase of 38.
The power unit, the direct-current capacitor selects the film capacitor, meets the requirement of the fluctuation range of the direct-current voltage, and the direct-current capacitor C min And the total capacity is 4.92mF, the total cost, the volume and the electrical performance margin are integrated, 6 820uF thin film capacitors are selected to be connected in parallel to serve as direct current side capacitors of the submodules, and the rated voltage of the thin film capacitors is 1200V. The IGBT is selected, and according to the rated capacity, the 5 th harmonic current effective value of the output side of the HAPF35 kilovolt is 415A, and the 7 th harmonic current effective value is 176A, so the total current effective value is 450A. The maximum current peak considers the worst case of forward superposition of the harmonic current peaks, so the maximum current peak is 836A. In order to ensure engineering application reliability, IGBT with specification above 1000A is required to be selected.
The rated voltage of the transformer is 220kV +/-2 multiplied by 2.5%/35kV. The transformer selects YNy wiring, a primary neutral point is provided with a protection CT for unbalance protection, the actual requirements of transformer design and harmonic wave treatment are considered, 220 kilovolt voltage class is regulated, the short-circuit impedance range of the power transformer with rated capacity of 31.5MVA to 420MVA is 12%, the transformer needs to be subjected to iron core magnetic density and winding adjustment optimization on the basis of conventional design, and the rated capacity of the 63Mvar transformer is selected according to the treatment capacity of 30Mvar.
Table 2 basic parameters of transformers
The effective value of the current at the 220kV side of the isolating switch is 75A, the short-circuit current is about 28.5kA, the isolating switch with rated current and short-circuit current larger than the system requirement is selected, the effective value of the current at the 220kV side of the circuit breaker is 75A, and the short-circuit current is about 28.5kA. The circuit breaker was selected as shown in table 4.
TABLE 3 basic parameters of disconnectors
Table 4 basic parameters of circuit breaker
The effective value of the current transformer at 220kV side of the current transformer at 220kV is 75A, and the short-circuit current is about 28.5kA. Two electromagnetic current transformers (hereinafter referred to as CT1 and CT 2) are provided, each having three windings. Wherein CT1 contains 1 measuring winding of 0.2 level and 2 main transformer protecting windings of 5P30 level. The technical parameters of the CT2 including 2 bus protection windings 5P30, 1 wave recording winding 5P30 and 220 kilovolt current transformer are shown in tables 5 and 6.
TABLE 5 220kVCT1 basic parameters
TABLE 6 220kVCT2 basic parameters
The 35kV current transformer has an effective value of 495A on the 35kV side and a short-circuit current of about 10.4kA. An electromagnetic current transformer is configured, and comprises three windings, 1 harmonic protection winding 5P30 (connected with a protection device), 1 overcurrent protection winding 5P30 (connected with an APF) and 1 wave recording winding 5P 30. The technical parameters are shown in tables 3-6. The low-voltage side of the transformer is provided with a set of 2-winding electromagnetic sleeve CT for main transformer protection.
Table 7 35kV current transformer basic parameters
The voltage transformer is characterized in that a 35kV side is a non-grounding system, when a single-phase short circuit occurs, the short circuit current is a capacitance-to-ground current, the capacitance-to-ground is small due to short circuit, and a CVT is configured on the 35kV side to monitor the voltage-to-ground and is used for judging whether the single-phase short circuit fault occurs or not, and the basic parameters of the CVT are shown in a table 8.
TABLE 8 35kVCVT basic parameters
And starting a loop, wherein a soft start mode is needed for the high-voltage APF in order to avoid the damage of a capacitor and a diode caused by a closing inrush current and reduce the influence of a charging process on the stability of the system voltage. When the APF is started, the starting switch is switched off, the APF is unlocked after the charging is completed, and the APF enters a normal working state. The maximum peak voltage of the starting resistor is 30kV, and the voltage index of the starting resistor is reduced along with the charging process. The peak current at start-up was 19A and the energy absorption of the start-up resistor was 39.7kJ. The dynamic resistor is a sleeve-type resistor with the resistance value of 1500 omega and the rated energy absorption of 100kJ, the bottom of the resistor is supported by a 35kV insulator, the parameters of the starting resistor are shown in Table 9, and an isolating switch of 1250A is selected, so that the temperature rise of the isolating switch is reduced.
TABLE 9 Start resistance parameters
| Model number | Project | Unit (B) | Normal working condition |
| 1 | Rated voltage of system | kV | 35 |
| 2 | Rated resistance | Ω | 1500 |
| 3 | Rated frequency | Hz | 50 |
| 4 | Single energy absorption | kJ | 39.7 |
| 5 | Rated energy absorption | kJ | 100 |
| 6 | Operating voltage (peak value, end-to-end) | kV | 28.4 |
| 7 | Terminal withstand voltage (peak value) | kV | 135 |
Table 10 35kV isolating switch basic parameters
The lightning arrester, 220 kilovolt lightning arrester, 220kV system lightning impulse withstand voltage is 950kV, operation impulse withstand voltage 750kV, residual voltage of the lightning arrester under the lightning impulse overvoltage is 678.5kV, residual voltage under the operation impulse overvoltage is 625kV, and the parameters of the selected lightning arrester are shown in table 11.
Table 11 basic parameters of 220KV lightning arrester
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The lightning arrester of 35 kilovolts, the lightning impulse withstand voltage of 35kV system is 200kV, the residual voltage of the lightning arrester under the lightning impulse overvoltage is 143kV, the 35kV side is the system which is not grounded, the normal phase voltage is the line voltage when the single-phase grounding fault occurs, and the long-term operation voltage of the lightning arrester is not lower than 40.5kV. The continuous operating voltage is not higher than the rated voltage divided by 1.25 and the selected arrester parameters are shown in table 12.
Basic parameter meter for 35kv lightning arrester
| Sequence number | Parameters (parameters) | Unit (B) | Value of |
| 1 | Model specification | YH5W-51/134 | |
| 2 | Rated voltage | kV | 51 |
| 3 | Continuous operating voltage | kV | 40.8 |
| 3 | Nominal discharge current | kA | 5 |
| 4 | Direct current lmA reference voltage | kV | ≥73 |
| 5 | Leakage current under 0.75 times DC lmA reference voltage | μA | <50 |
| 6 | Rated frequency | Hz | 50 |
| 7 | Power frequency reference voltage | kV | ≥51 |
| 8 | Maximum residual voltage (peak value) at 250A operating impact current | kV | ≤114 |
| 9 | Maximum residual voltage (peak value) at 5kA lightning impulse current | kV | ≤134 |
| 10 | Maximum residual voltage (peak value) at 5kA steep wave impact current | kV | ≤154 |
| 11 | High current surge withstand capability, 4/10. Mu.s, 2 times | kA | 65 |
| 12 | Line discharge rating | 2 | |
| 13 | Line discharge rush current peak apparent duration | ms | 2 |
| 14 | 2ms square wave impulse current (peak value) | A | 400 |
| 15 | Power frequency withstand voltage of jacket | kV | 95 |
| 16 | The lightning impulse withstand voltage, peak value of the jacket | kV | 185 |
| 17 | Partial discharge amount | pC | 10 |
The structure and the insulation design are that the power unit is placed vertically and is favorable for water cooling and heat dissipation, the power frame is divided into 3 layers, 7 modules are arranged on each layer, each phase contains 2 back-to-back power frames, 42 positions are all arranged, and the configuration can be flexibly carried out according to different requirements. The individual power frame dimensions are approximately 1920mm (wide) by 800mm (deep) by 2600mm (high) and the frame weight is approximately 1600kg. A. B, C three phases are sequentially arranged in the container, three-phase incoming wires are led into the container by the wall bushing, the neutral points are connected by cables, each power valve group is supported by an insulator, each phase of incoming cable is led into the container by the wall bushing, the safety distance between each phase of incoming cable and the bottom and side wall of the container is more than 470mm, the creepage distance is more than 980, and the creepage ratio distance is more than 35mm/kV.
The heat dissipation design adopts a totally-enclosed water cooling heat dissipation mode, namely water cooling and air conditioning compound heat dissipation, wherein the internal circulation of a water cooling system is liquid cooling, the external circulation is water-air heat exchange, and the totally-enclosed water cooling heat dissipation has the advantages that compared with non-sealing, the influence of external environment factors on the operation of equipment can be reduced, especially under high-pressure application, the operation faults of the equipment caused by dust, foreign matter invasion and the like can be effectively prevented, and the corrosion phenomenon of exposed connecting conductors can be prevented by reducing indoor air humidity, salt alkalinity and the like.
And the heating of the IGBT and the equalizing resistor in the power unit is carried out by the water cooling system, wherein a small part of heating and cooling plates and pipelines radiate into the container, and the total heating power is 596.81kW. Two 300kW heat exchangers are selected, the total heat dissipation capacity is about 600kW, a main water pump with the flow rate of 49.2m < 3 >/h and the power of 11kW is selected as a water cooling main machine part, a main water pump and a standby water pump are adopted to work alternately so as to improve the reliability of a water cooling system, a water supplementing pump is additionally arranged, the power of the water supplementing pump is 0.75kW, and 4 air conditioners with the refrigerating capacity of 7.5kW and 2 air conditioners with the power of 5kW are selected as air conditioners.
The protection configuration is that the HAPF self-control protection device protects the whole equipment in real time by monitoring the power grid state, the external environment quantity, the external switch quantity, the valve group self state, the communication state and the power supply and cooling auxiliary machine state in real time, and when the equipment is abnormal, the alarm, the device locking and the system tripping can be executed according to the influence degree and the result of the abnormality, so that the device is not damaged, and the fault expansion is prevented. The main transformer is configured with main power transformation gas quantity protection according to double configuration, is configured with 1 set of non-electric quantity protection, and adopts a national network standard conventional sampling protection version.
S3: the performance of the filter is monitored regularly, maintenance and adjustment are carried out according to the monitoring result, the effectiveness of the filter is ensured, the performance data of the filter is recorded, and a report is generated for analysis and maintenance.
Further, the present embodiment also provides a filter design system suitable for harmonic characteristics of an offshore wind farm, including: the acquisition module is used for collecting operation data and primary equipment parameters of the offshore wind farm, preprocessing the operation data, analyzing the collected operation data, determining the limit value of the electric energy quality index of the offshore wind farm, selecting a proper type of filter, and calculating and acquiring the filter parameters; the design module is used for selecting electronic elements suitable for design to design a filter circuit according to the calculated filter parameters, testing the performance of the filter and installing the designed filter; the monitoring module is used for periodically monitoring the performance of the filter, maintaining and adjusting according to the monitoring result, ensuring the effectiveness of the filter, recording the performance data of the filter, and generating a report for analysis and maintenance.
The embodiment also provides a computer device, which is suitable for the situation of a filter design method of the harmonic characteristic of the offshore wind farm, and comprises the following steps: a memory and a processor; the memory is used for storing computer executable instructions and the processor is used for executing the computer executable instructions to implement all or part of the steps of the method according to the embodiments of the present invention as set forth in the embodiments above.
The present embodiment also provides a storage medium having stored thereon a computer program which, when executed by a processor, performs the method of any of the alternative implementations of the above embodiments. The storage medium may be implemented by any type or combination of volatile or nonvolatile Memory devices, such as static random access Memory (Static Random Access Memory, SRAM), electrically erasable Programmable Read-Only Memory (Electrically Erasable Programmable Read-Only Memory, EEPROM), erasable Programmable Read-Only Memory (Erasable Programmable Read OnlyMemory, EPROM), programmable Read-Only Memory (PROM), read-Only Memory (ROM), magnetic Memory, flash Memory, magnetic disk, or optical disk.
The storage medium according to the present embodiment belongs to the same inventive concept as the data storage method according to the above embodiment, and technical details not described in detail in the present embodiment can be seen in the above embodiment, and the present embodiment has the same advantageous effects as the above embodiment.
Example 2
Referring to fig. 2 to 5, for a second embodiment of the present invention, the embodiment provides a filter design method suitable for the harmonic characteristics of an offshore wind farm, and in order to verify the beneficial effects of the present invention, scientific demonstration is performed through economic benefit calculation and simulation experiments.
The real controller of the treatment device is connected to the RSCAPD simulation platform through optical fibers, receives system voltage and current signals through cables, receives and transmits switching value signals through cables, and achieves semi-real simulation test on the performance of the controller.
The effectiveness of the technical proposal is verified, and five kinds of simulation working conditions are set: the method comprises the following steps of (1) simulating the treatment effect under the normal steady-state working condition; (2) adaptive simulation when the power grid background harmonic changes; (3) adaptive simulation when the power grid operation mode is changed; and (5) simulating the start-up and stop processes of the treatment device.
The specific simulation working condition setting is shown in table 13, wherein working conditions 1-2 check the treatment effect of the treatment device under normal working conditions; the adaptability of the control device to the background harmonic variation of the power grid is checked under the working conditions 3-4; the working condition 5 checks the adaptability of the treatment device to the change of the power grid operation mode; the adaptability of the treatment device in the transient processes of air-drop sea cable, offshore boost change and the like is checked under the working conditions 6-9.
Table 13 simulation Condition setting
The simulation results of the background harmonic levels (namely, the harmonic voltage levels of the co-constructed 220kV bus before the wind power plant is put into operation) under different power grid operation modes are shown in a table 14.
Table 14 grid background harmonic levels for different grid modes of operation
TABLE 15 5 subharmonic treatment effect under various working conditions
Table 16 effects of treatment with 7 th harmonic under various conditions
And (3) putting the sea wind power plant into operation and putting the sea wind power plant into a treatment device to obtain 5 times and 7 times harmonic treatment effects under the change of the running mode of the power grid. When the power grid operates under the working condition 5.1, after the treatment, the 5 th harmonic current of the grid-connected line is reduced from 42.1A to 4.2A, and the 7 th harmonic current is reduced from 17.5A to 1.2A. When the power grid operates under the working condition 5.2, after the treatment, the 5 th harmonic current of the grid-connected line is reduced to 0.7A from 44.5A, and the 7 th harmonic current is reduced to 0.8A from 17.6A. When the power grid operates under the working condition 5.3, after the treatment, the 5 th harmonic current of the grid-connected line is reduced to 2.2A from 40.0A, and the 7 th harmonic current is reduced to 0.7A from 16.6A. When the power grid operates under the working condition 5.4, after the treatment, the 5 th harmonic current of the grid-connected line is reduced to 2.0A from 22.5A, and the 7 th harmonic current is reduced to 0.6A from 15.5A. When the power grid operates under the working condition of 5.5, after the treatment, the 5 th harmonic current of the grid-connected line is reduced to 1.9A from 15.8A, and the 7 th harmonic current is reduced to 1.1A from 15.0A. When the power grid operates under the working condition of 5.6, after the treatment, the 5 th harmonic current of the grid-connected line is reduced from 42.1A to 4.2A, and the 7 th harmonic current is reduced from 17.5A to 1.2A.
In conclusion, after the designed active filter is used for treatment, indexes of 5 th harmonic current and 7 th harmonic current of the grid-connected point of the sea wind power plant can meet national standard requirements. When the background harmonic voltage of the wind farm before operation does not exceed the national standard limit value, after treatment, the 5 th harmonic voltage and the 7 th harmonic voltage of the grid connection point all meet the national standard requirement. When the background harmonic voltage exceeds the national standard limit value, after treatment, the 5 th harmonic voltage and the 7 th harmonic voltage of the grid connection point can be restored to the background harmonic level before the wind power plant is put into operation.
It should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention may be modified or substituted without departing from the spirit and scope of the technical solution of the present invention, which is intended to be covered in the scope of the claims of the present invention.
Claims (10)
1. A filter design method suitable for the harmonic characteristics of an offshore wind farm is characterized by comprising the following steps: comprising the steps of (a) a step of,
collecting operation data and primary equipment parameters of the offshore wind farm, preprocessing the operation data, analyzing the collected operation data, determining the limit value of the electric energy quality index of the offshore wind farm, selecting a proper type of filter, and calculating to obtain filter parameters;
selecting an electronic element suitable for design to design a filter circuit according to the calculated filter parameters, testing the performance of the filter, and installing the designed filter;
the performance of the filter is monitored regularly, maintenance and adjustment are carried out according to the monitoring result, the effectiveness of the filter is ensured, the performance data of the filter is recorded, and a report is generated for analysis and maintenance.
2. A filter design method suitable for use in offshore wind farm harmonic performance as claimed in claim 1, wherein: the operation data comprise current, voltage data, normal operation and abnormal situation data; the preprocessing includes removing noise and outliers; the primary equipment parameters comprise main wiring, sea cables, overhead lines, offshore boost transformers, wind turbines and other primary equipment.
3. A filter design method suitable for use in offshore wind farm harmonic performance as claimed in claim 2, wherein: the electric energy quality index limit value comprises a public connection point which meets the public power grid harmonic voltage limit value, and the harmonic current is lower than a specified allowable value when a user injects into the public connection point;
specifically, when the minimum short-circuit capacity at the public connection point is different from the corresponding reference capacity, the allowable value of the harmonic current is corrected, and the calculation formula is as follows:
I h ＝S k1 /S k2 ×I hp
wherein S is k1 Minimum short circuit capacity for common connection point; s is S k2 Is the reference short circuit capacity; i hp The allowable value of the h harmonic current in the table is as follows; i h For short circuit capacity S k1 The h harmonic current allowable value;
harmonic current allowable value I injected into power grid by each user of same public connection point hi The distribution is carried out according to the ratio of the protocol capacity of the user to the capacity of the power supply equipment of the public connection point, and the calculation formula is as follows:
I hi ＝I n (S i /S t ) 1/a
wherein I is n Is the permitted value of the nth harmonic current; s is S i Power utilization protocol capacity for the ith user; s is S t Power supply equipment capacity for the common connection point; a is the phase superposition coefficient.
4. A filter design method suitable for use in offshore wind farm harmonic characterization as claimed in claim 3, wherein: the filter comprises a passive filter and an active filter, and the passive filter adopts an inductance series capacitance mode to realize the filtering effect on harmonic waves; the active filter HAPF adopts a mode of dynamically restraining harmonic waves and compensating reactive power to flexibly adjust a compensation mode and a compensation frequency band, so as to realize the filtering effect on the harmonic waves; the HAPF control system consists of two parts, namely harmonic current detection and compensation current tracking, wherein the current control mode is divided into a direct current control mode and an indirect current control mode, a main circuit adopts a PWM converter, and when a power grid charges a capacitor at the direct current side of the device, the main circuit works in a rectification state; when the device sends compensation current to the power grid, the main circuit works in an inversion state, and the HAPF working principle is as follows:
i s ＝i L +i c
i L ＝i L1 +i Lh
i c ＝-i Lh
i s ＝i L +i c ＝i L1
wherein i is s Is the grid current, i L Is the load current, i c Is the compensation current, i L1 Is the fundamental component of the grid current and i is the harmonic component.
5. The method for designing a filter suitable for use in the harmonic characteristics of an offshore wind farm according to claim 4, wherein: the HAPF adopts a CPS-SPWM (single-stage frequency-doubling carrier phase-shift pulse width modulation) technology, which comprises,
at the position of N sm In the converters in cascade connection of H-bridge units, modulated wave signals V with 180 DEG phase difference are used c Taking 2N sm The same frequency and the same amplitude but 2/N phase difference sm Triangular carrier signal V of carrier period r ；
The front axle is compared with the forward modulation wave, the rear axle is compared with the reverse modulation wave to modulate, and 2N is generated sm Rectangular pulse sequences with different columns respectively drive IGBT devices of each H-bridge unit to be conducted;
sampling grid-connected line current according to the actual system control target requirement, obtaining a harmonic current component through a harmonic extraction algorithm, and obtaining a final instruction current signal by making a difference with a reference value;
and generating a modulated wave signal through tracking adjustment of the current inner loop, generating a final IGBT driving signal through PWM carrier phase-shifting modulation, and transmitting the final IGBT driving signal to each electronic element to finish the output control of corresponding current.
6. A filter design method suitable for use in offshore wind farm harmonic performance as claimed in claim 5, wherein: the electronic element comprises a power valve group, a power unit, a transformer, an isolating switch, a circuit breaker, a current transformer, a voltage transformer, a starting loop and a lightning arrester;
determining the total module quantity of each phase in a power valve group, wherein the power unit comprises a direct current capacitor and an IGBT (insulated gate bipolar transistor) type;
the transformer selects YNy wiring, a primary neutral point is provided with a protection CT for unbalance protection, and iron core magnetic density and winding adjustment optimization are carried out; the effective current value and the short-circuit current of the isolating switch and the circuit breaker are the same, and the isolating switch with rated current and short-circuit current larger than the requirements is selected;
the current transformers comprise 220 kilovolt current transformers and 35 kilovolt current transformers, the 220 kilovolt current transformers comprise electromagnetic current transformers CT1 and CT2, and the 35 kilovolt current transformers comprise electromagnetic current transformers CT3;
the voltage transformer is a non-grounding system, when a single-phase short circuit to ground occurs, the short circuit current is the capacitance current to ground, and the voltage to ground is monitored to judge whether the single-phase short circuit to ground occurs or not;
when the starting loop is started, the starting switch is switched off, the starting switch is switched on after charging is completed, the APF is unlocked and enters a normal working state, a sleeve-type resistor is selected, and the bottom of the sleeve-type resistor is supported through an insulator;
the lightning arrester comprises a 220KV lightning arrester and a 35KV lightning arrester, and is used for determining lightning impulse withstand voltage, operation impulse withstand voltage and residual voltage under lightning impulse overvoltage and residual voltage under operation impulse overvoltage of the lightning arrester.
7. The method for designing a filter suitable for use in harmonic characteristics of an offshore wind farm according to claim 6, wherein: the structure and the insulation design determine the outer dimensions of a power frame layer, a single-layer module and a single power frame, A, B, C three phases are sequentially arranged in a container, a wall bushing introduces three-phase incoming wires into the container, neutral points are connected through cables, each power valve group is supported by an insulator, and each phase of incoming cable is introduced into the container through the wall bushing; the heat dissipation design adopts water cooling and air conditioning for compound heat dissipation, the internal circulation of the water cooling system is liquid cooling, and the external circulation is water-air heat exchange;
the protection configuration is used for protecting equipment in real time by monitoring the state of a power grid, the external environment quantity, the external switching quantity, the state of a valve group, the communication state and the states of a power supply and a cooling auxiliary machine in real time in the operation process, and when the equipment is abnormal, alarming, device locking and system tripping are executed according to the influence degree and the effect of the abnormality.
8. A filter design system suitable for the harmonic characteristics of an offshore wind farm, based on the filter design method suitable for the harmonic characteristics of the offshore wind farm according to any one of claims 1 to 7, characterized in that: comprising the steps of (a) a step of,
the acquisition module is used for collecting operation data and primary equipment parameters of the offshore wind farm, preprocessing the operation data, analyzing the collected operation data, determining the limit value of the electric energy quality index of the offshore wind farm, selecting a proper type of filter, and calculating and acquiring the filter parameters;
the design module is used for selecting electronic elements suitable for design to design a filter circuit according to the calculated filter parameters, testing the performance of the filter and installing the designed filter;
the monitoring module is used for periodically monitoring the performance of the filter, maintaining and adjusting according to the monitoring result, ensuring the effectiveness of the filter, recording the performance data of the filter, and generating a report for analysis and maintenance.
9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that: the processor, when executing the computer program, implements the steps of the filter design method according to any one of claims 1-7, which is suitable for the harmonic characteristics of an offshore wind farm.
10. A computer-readable storage medium having stored thereon a computer program, characterized by: the computer program, when executed by a processor, carries out the steps of the filter design method according to any one of claims 1 to 7, which is suitable for use in the harmonic characteristics of an offshore wind farm.
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