CN117638899A - Fault adjustment method and device for offshore wind power low-frequency alternating current sending-out system - Google Patents
Fault adjustment method and device for offshore wind power low-frequency alternating current sending-out system Download PDFInfo
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Abstract
The invention discloses a fault adjustment method and device for an offshore wind power low-frequency alternating current sending-out system, wherein the method comprises the following steps: detecting the three-phase alternating-current voltage instantaneous value at the power frequency side of the land frequency conversion station and the submodule capacitor voltage instantaneous value of the modularized multi-level matrix converter in real time; calculating an alternating voltage signal value by adopting a power frequency side three-phase alternating voltage instantaneous value, and performing hysteresis loop segment processing on the alternating voltage signal value to determine whether a power frequency side alternating current fault exists; when the AC fault on the power frequency side is determined to exist, calculating a DC voltage signal value by adopting the instantaneous value of the capacitance voltage of the submodule; based on the direct-current voltage signal value, fault adjustment is carried out by updating the low-frequency side alternating-current voltage amplitude reference value of the land frequency conversion station or putting into an alternating-current energy consumption device. In the whole fault adjustment process, the low-frequency side alternating-current voltage amplitude reference value and the alternating-current energy consumption device are adopted for fault adjustment, so that the rated capacity of the alternating-current energy consumption device can be reduced, and the economy of the offshore wind power low-frequency alternating-current sending system is improved.
Description
Technical Field
The invention relates to the technical field of power transmission and distribution of power systems, in particular to a fault adjustment method and device for an offshore wind power low-frequency alternating current transmission system.
Background
The offshore wind power has the advantages of rich resources, high stability, less requirement on land resources and the like, and plays an important role in the field of new energy power generation.
For the offshore wind power low-frequency alternating current transmission system, the modularized multi-level matrix converter is the most mature technical scheme in the current high-voltage high-capacity transmission occasion, but under the condition of serious alternating current fault on the power frequency side, serious power surplus can occur in the modularized multi-level matrix converter. In order to solve the above problems, in the prior art, an energy consumption device with the same rated power as that of a modularized multi-level matrix converter is generally adopted, which easily results in higher operation and maintenance cost of an offshore wind power low-frequency alternating current transmission system.
Disclosure of Invention
The invention provides a fault adjusting method and device for an offshore wind power low-frequency alternating current transmission system, which solve the technical problem that the operation and maintenance cost of the offshore wind power low-frequency alternating current transmission system is high due to the fact that an energy consumption device with the same input as the rated power of a modularized multi-level matrix converter is required to be adopted when the offshore wind power low-frequency alternating current transmission system faces a serious alternating current fault condition at a power frequency side in the prior art.
The invention provides a fault adjustment method of an offshore wind power low-frequency alternating current transmission system, which comprises an onshore frequency conversion station based on a modularized multi-level matrix converter, wherein two ends of the onshore frequency conversion station are respectively connected with a low-frequency side and a power frequency side; the method comprises the following steps:
detecting the power frequency side three-phase alternating-current voltage instantaneous value of the land frequency conversion station and the submodule capacitance voltage instantaneous value of the modularized multi-level matrix converter in real time;
calculating an alternating voltage signal value by adopting the power frequency side three-phase alternating voltage instantaneous value, and performing hysteresis loop processing on the alternating voltage signal value to determine whether a power frequency side alternating current fault exists;
when the AC fault on the power frequency side is determined to exist, calculating a DC voltage signal value by adopting the instantaneous value of the capacitance voltage of the submodule;
based on the direct-current voltage signal value, fault adjustment is carried out by updating a low-frequency side alternating-current voltage amplitude reference value of the land frequency conversion station or putting into an alternating-current energy consumption device.
Optionally, the step of calculating an ac voltage signal value by using the instantaneous value of the three-phase ac voltage at the power frequency side, performing hysteresis loop processing on the ac voltage signal value, and determining whether there is an ac fault at the power frequency side includes:
after square sum operation is carried out on the three-phase alternating voltage instantaneous value at the power frequency side, square operation is carried out, a first low-pass filter is input for filtering treatment, and an alternating voltage signal value is output;
when the alternating voltage signal value is smaller than the hysteresis voltage lower limit value of the hysteresis loop node for the first time, outputting a first control signal value with the power frequency side alternating current fault;
and outputting a first control signal value without the power frequency side alternating current fault when the alternating current voltage signal value is greater than or equal to the hysteresis voltage lower limit value of the hysteresis loop or the alternating current voltage signal value is greater than the hysteresis voltage upper limit value of the hysteresis loop after outputting the first control signal value with the power frequency side alternating current fault.
Optionally, the modular multilevel matrix converter comprises a plurality of bridge arms, and each bridge arm is cascaded with a plurality of sub-modules; when it is determined that an ac fault exists at the power frequency side, the step of calculating a dc voltage signal value by using the instantaneous value of the capacitance voltage of the submodule includes:
square sum operation is carried out on the instantaneous values of the capacitor voltage of the plurality of sub-modules associated with each bridge arm respectively, and a plurality of square sum values of the instantaneous values of the capacitor voltage are generated;
and after the square sum value of all the capacitor voltage instantaneous values is adopted for open square operation, the total number of the submodules associated with the modularized multi-level matrix converter is subjected to ratio operation, and a second low-pass filter is input for filtering processing to output a direct-current voltage signal value.
Optionally, the step of performing fault adjustment by updating the low-frequency side ac voltage amplitude reference value of the land frequency conversion station or putting into an ac energy consumption device based on the dc voltage signal value includes:
when the power frequency side alternating current fault is determined to exist, performing difference value operation by adopting the direct current voltage signal value and a preset first threshold value, and performing multiplication operation by adopting a preset proportionality coefficient to generate an initial voltage regulating value;
performing amplitude limiting link processing on the initial voltage regulating value to determine a target voltage regulating value;
acquiring a low-frequency side alternating voltage amplitude reference value of the land frequency conversion station, carrying out addition operation on the low-frequency side alternating voltage amplitude reference value and the target voltage regulating value, outputting a new low-frequency side alternating voltage amplitude reference value and regulating the new low-frequency side alternating voltage amplitude reference value;
after the new low-frequency side alternating current voltage amplitude reference value is adopted for adjustment, if the direct current voltage signal value is larger than a preset second threshold value, an alternating current energy consumption device is put into.
Optionally, the step of performing clipping link processing on the initial voltage adjustment value to determine a target voltage adjustment value includes:
if the initial voltage regulating value is judged to be larger than the preset limiting voltage upper limit value through the limiting link, the limiting voltage upper limit value is used as a target voltage regulating value;
if the initial voltage regulating value is less than the preset limiting voltage lower limit value through the limiting link, taking the limiting voltage lower limit value as a target voltage regulating value;
and if the initial voltage regulating value is judged to be not smaller than the lower limit value of the preset limiting voltage and not larger than the upper limit value of the preset limiting voltage through the limiting link, taking the initial voltage regulating value as a target voltage regulating value.
Optionally, the determining process of the target rated capacity of the ac power consumption device includes:
obtaining a simulation model of the offshore wind power low-frequency alternating current transmission system;
when the simulation model is in an alternating current fault state at the power frequency side, inputting an alternating current energy consumption device with the same rated capacity as the modularized multi-level matrix converter, and determining a target state value;
when the simulation model is in a power frequency side alternating current fault state, after the low frequency side alternating current voltage amplitude reference value of the simulation model is adjusted, the rated capacity of an alternating current energy consumption device is iteratively adjusted until a rated capacity critical value meeting the target state value is obtained;
and constructing target rated capacity by taking the sum value of the rated capacity critical value and the preset capacity margin and the rated capacity critical value as interval endpoints.
The invention provides a fault adjusting device of an offshore wind power low-frequency alternating current transmission system, which comprises an onshore frequency conversion station based on a modularized multi-level matrix converter, wherein two ends of the onshore frequency conversion station are respectively connected with a low-frequency side and a power frequency side; the device comprises:
the parameter detection module is used for detecting the power frequency side three-phase alternating voltage instantaneous value of the land frequency conversion station and the submodule capacitance voltage instantaneous value of the modularized multi-level matrix converter in real time;
the fault judging module is used for calculating an alternating voltage signal value by adopting the power frequency side three-phase alternating voltage instantaneous value, carrying out hysteresis loop processing on the alternating voltage signal value and determining whether a power frequency side alternating current fault exists or not;
the direct-current voltage signal value calculation module is used for calculating a direct-current voltage signal value by adopting the instantaneous value of the capacitance voltage of the submodule when the fact that the power frequency side alternating-current fault exists is determined;
and the fault adjustment module is used for carrying out fault adjustment by updating the low-frequency side alternating current voltage amplitude reference value of the land frequency conversion station or putting into an alternating current energy consumption device based on the direct current voltage signal value.
Optionally, the fault judging module is specifically configured to:
after square sum operation is carried out on the three-phase alternating voltage instantaneous value at the power frequency side, square operation is carried out, a first low-pass filter is input for filtering treatment, and an alternating voltage signal value is output;
when the alternating voltage signal value is smaller than the hysteresis voltage lower limit value of the hysteresis loop node for the first time, outputting a first control signal value with the power frequency side alternating current fault;
and outputting a first control signal value without the power frequency side alternating current fault when the alternating current voltage signal value is greater than or equal to the hysteresis voltage lower limit value of the hysteresis loop or the alternating current voltage signal value is greater than the hysteresis voltage upper limit value of the hysteresis loop after outputting the first control signal value with the power frequency side alternating current fault.
Optionally, the modular multilevel matrix converter comprises a plurality of bridge arms, and each bridge arm is cascaded with a plurality of sub-modules; the direct-current voltage signal value calculation module is specifically used for:
square sum operation is carried out on the instantaneous values of the capacitor voltage of the plurality of sub-modules associated with each bridge arm respectively, and a plurality of square sum values of the instantaneous values of the capacitor voltage are generated;
and after the square sum value of all the capacitor voltage instantaneous values is adopted for open square operation, the total number of the submodules associated with the modularized multi-level matrix converter is subjected to ratio operation, and a second low-pass filter is input for filtering processing to output a direct-current voltage signal value.
Optionally, the fault-adjustment module includes:
the initial voltage regulating value generating unit is used for generating an initial voltage regulating value by carrying out multiplication operation on the difference value operation between the direct current voltage signal value and a preset first threshold value and the preset proportionality coefficient when the power frequency side alternating current fault is determined to exist;
the amplitude limiting processing unit is used for carrying out amplitude limiting link processing on the initial voltage regulating value and determining a target voltage regulating value;
the voltage amplitude adjusting unit is used for acquiring a low-frequency side alternating voltage amplitude reference value of the land frequency conversion station, carrying out addition operation on the low-frequency side alternating voltage amplitude reference value and the target voltage adjusting value, outputting a new low-frequency side alternating voltage amplitude reference value and adjusting the new low-frequency side alternating voltage amplitude reference value;
and the alternating current energy consumption device input unit is used for inputting the alternating current energy consumption device if the direct current voltage signal value is larger than a preset second threshold value after the new low-frequency side alternating current voltage amplitude reference value is adopted for adjustment.
From the above technical scheme, the invention has the following advantages:
the invention detects the three-phase alternating voltage instantaneous value at the power frequency side of the land frequency conversion station and the submodule capacitance voltage instantaneous value of the modularized multi-level matrix converter in real time; calculating an alternating voltage signal value by adopting a power frequency side three-phase alternating voltage instantaneous value, and performing hysteresis loop segment processing on the alternating voltage signal value to determine whether a power frequency side alternating current fault exists; when the AC fault on the power frequency side is determined to exist, calculating a DC voltage signal value by adopting the instantaneous value of the capacitance voltage of the submodule; based on the direct-current voltage signal value, fault adjustment is carried out by updating the low-frequency side alternating-current voltage amplitude reference value of the land frequency conversion station or putting into an alternating-current energy consumption device. In the whole process of the power frequency side alternating current fault coordination control of the offshore wind power low-frequency alternating current sending-out system, the amplitude reference value of the alternating current voltage at the low frequency side is regulated to be combined with the input alternating current energy consumption device for fault regulation, so that the implementation is simple, the applicability is strong, the rated capacity of the input alternating current energy consumption device can be effectively reduced, the equipment investment and the operation and maintenance cost are obviously reduced, and the economy of the whole offshore wind power low-frequency alternating current sending-out system is improved.
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In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained from these drawings without inventive faculty for a person skilled in the art.
FIG. 1 is a flow chart of steps of a fault adjustment method for an offshore wind power low-frequency alternating current transmission system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a marine wind power low-frequency AC transmission system according to an embodiment of the present invention;
FIG. 3 is a schematic view of a hysteresis loop according to an embodiment of the present invention;
FIG. 4 is a schematic diagram illustrating generation of a second control signal value according to an embodiment of the present invention;
fig. 5 is a block diagram of a fault adjustment device of an offshore wind power low-frequency ac transmission system according to an embodiment of the present invention.
Detailed Description
The embodiment of the invention provides a fault adjustment method and device for an offshore wind power low-frequency alternating current transmission system, which are used for solving the technical problem that the operation and maintenance cost of the offshore wind power low-frequency alternating current transmission system is high due to the fact that an energy consumption device with the same rated power as a modularized multi-level matrix converter is needed to be adopted when the offshore wind power low-frequency alternating current transmission system faces a serious alternating current fault condition at a power frequency side in the prior art.
In order to make the objects, features and advantages of the present invention more comprehensible, the technical solutions in the embodiments of the present invention are described in detail below with reference to the accompanying drawings, and it is apparent that the embodiments described below are only some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, fig. 1 is a flowchart illustrating a fault adjustment method for an offshore wind power low-frequency ac transmission system according to an embodiment of the present invention.
The invention provides a fault adjustment method of an offshore wind power low-frequency alternating current transmission system, which comprises an onshore frequency conversion station based on a modularized multi-level matrix converter, wherein two ends of the onshore frequency conversion station are respectively connected with a low-frequency side and a power frequency side; the method comprises the following steps:
and 101, detecting the three-phase alternating-current voltage instantaneous value at the power frequency side of the land frequency conversion station and the submodule capacitor voltage instantaneous value of the modularized multi-level matrix converter in real time.
In the embodiment of the invention, as shown in fig. 2, an equivalent fan, a low-frequency medium-voltage alternating current sea cable, an offshore step-up transformer, a low-frequency high-voltage alternating current sea cable, an alternating current bus, an onshore frequency conversion station based on a modularized multi-level matrix converter and an onshore main network are sequentially connected with an offshore wind power low-frequency alternating current transmission system. In the offshore wind power low-frequency alternating current sending-out system, the power output by two equivalent fans is converged to the low-voltage side of an offshore step-up transformer through two low-frequency medium-voltage alternating current sea cables, the power is sent to an onshore frequency conversion station based on a modularized multi-level matrix converter through the low-frequency high-voltage alternating current sea cables after being boosted by the offshore step-up transformer, the power is sent to an onshore main network after being converted by the onshore frequency conversion station, and system parameters are shown in table 1:
TABLE 1
The two ends of the land frequency conversion station are respectively connected with the low-frequency side and the power frequency side, the modularized multi-level matrix converter comprises a plurality of bridge arms, each bridge arm is cascaded with a plurality of submodules, the three-phase alternating-current voltage instantaneous value of the power frequency side of the land frequency conversion station is detected in real time, and the submodule capacitor voltage instantaneous value of each submodule in the modularized multi-level matrix converter is collected.
And 102, calculating an alternating voltage signal value by adopting an instantaneous value of the three-phase alternating voltage at the power frequency side, and performing hysteresis loop processing on the alternating voltage signal value to determine whether the power frequency side alternating current fault exists.
Optionally, step 102 comprises the sub-steps of:
after square sum operation is carried out on the three-phase alternating voltage instantaneous value at the power frequency side, square operation is carried out, a first low-pass filter is input for filtering treatment, and an alternating voltage signal value is output;
when the alternating voltage signal value is smaller than the hysteresis voltage lower limit value of the hysteresis loop for the first time, outputting a first control signal value with the power frequency side alternating current fault;
when the alternating voltage signal value is greater than or equal to the hysteresis voltage lower limit value of the hysteresis loop, or when the alternating voltage signal value is greater than the hysteresis voltage upper limit value of the hysteresis loop after outputting the first control signal value with the power frequency side alternating current fault, outputting the first control signal value without the power frequency side alternating current fault.
In the embodiment of the invention, the square sum operation is firstly carried out on the instantaneous value of the three-phase alternating voltage at the power frequency side, then the square operation is carried out, the effective value of the three-phase alternating voltage at the power frequency side is obtained, and the effective value of the three-phase alternating voltage at the power frequency side is processed by a first low-pass filter and then is used as an alternating voltage signal value. As shown in fig. 3, the hysteresis loop includes a hysteresis voltage upper limit value of 0.85p.u., and a hysteresis voltage lower limit value of 0.8p.u., and when the ac voltage signal value is smaller than the hysteresis voltage lower limit value for the first time, the output first control signal value is 1, which indicates that the ac voltage is too low, i.e., that there is a power frequency side ac fault and control is needed, and then the first control signal value can be changed to 0, i.e., that there is no power frequency side ac fault, only when the ac voltage signal value is greater than the hysteresis voltage upper limit value, and meanwhile, if the ac voltage signal value is always greater than or equal to the hysteresis voltage lower limit value, the output first control signal value is 0. By means of the hysteresis loop, repeated fluctuations of the first control signal value caused by fluctuations of the alternating voltage signal value can be avoided.
Preferably, the first low-pass filter is in a specific form of a first-order inertia link, and the time constant is 2.0 ms-5.0 ms.
And 103, when the existence of the power frequency side alternating current fault is determined, calculating a direct current voltage signal value by adopting the instantaneous value of the capacitance voltage of the submodule.
Optionally, step 103 comprises the sub-steps of:
square sum operation is carried out on the instantaneous values of the capacitor voltage of the plurality of sub-modules associated with each bridge arm respectively, and a plurality of square sum values of the instantaneous values of the capacitor voltage are generated;
and after the square sum value of all the capacitor voltage instantaneous values is adopted for open square operation, the total number of sub-modules related to the modularized multi-level matrix converter is subjected to ratio operation, and a second low-pass filter is input for filtering processing to output a direct-current voltage signal value.
In the embodiment of the invention, for the detected instantaneous values of the capacitor voltage of the submodule, the square sum value V of the instantaneous values of the capacitor voltage of all the submodules in all the 9 bridge arms is calculated first armi (i=1, 2, …, 9), where i is the i-th leg, and then performing an open square operationAnd dividing the calculation result by the total number of the submodules, and inputting the result into a second low-pass filter for filtering processing to output as a direct-current voltage signal value. Since the measured voltage parameter is fluctuating, clutter can be filtered out by a low pass filter.
Preferably, the second low pass filter is embodied as a second order Butterworth filter, characterized by a frequency of 100Hz and a quality factor of 0.707.
Step 104, based on the direct-current voltage signal value, fault adjustment is performed by updating the low-frequency side alternating-current voltage amplitude reference value of the land frequency conversion station or putting into an alternating-current energy consumption device.
Optionally, step 104 comprises the sub-steps of:
s1, when it is determined that an alternating current fault on a power frequency side exists, performing difference operation by adopting a direct current voltage signal value and a preset first threshold value, and performing multiplication operation by adopting a preset proportionality coefficient to generate an initial voltage regulating value;
s2, performing amplitude limiting link processing on the initial voltage regulating value to determine a target voltage regulating value;
s3, acquiring a low-frequency side alternating voltage amplitude reference value of the land frequency conversion station, performing addition operation on the low-frequency side alternating voltage amplitude reference value and a target voltage regulation value, outputting a new low-frequency side alternating voltage amplitude reference value and regulating the new low-frequency side alternating voltage amplitude reference value;
s4, after the new low-frequency side alternating current voltage amplitude reference value is adopted for adjustment, if the direct current voltage signal value is larger than a preset second threshold value, the alternating current energy consumption device is put into.
The initial voltage adjustment value refers to a voltage adjustment value calculated based on the direct current voltage signal value. The target voltage regulating value refers to a voltage regulating value which is actually regulated after the initial voltage regulating value is processed by a limiting link. The voltage regulation value is used as an additional control quantity of the amplitude reference value of the low-frequency side alternating current voltage during the alternating current fault of the power frequency side.
The first threshold value and the second threshold value are used for measuring the direct current overvoltage degree.
In the embodiment of the invention, when it is determined that an ac fault exists on the power frequency side, as shown in fig. 4, a difference value is calculated by using a dc voltage signal value and a preset first threshold value, and an initial voltage adjustment value is obtained by multiplying the difference value by a preset scaling factor, and the initial voltage adjustment value is processed by an amplitude limiting link to be used as a target voltage adjustment value, wherein the first threshold value can be set to be 1.05p.u., the scaling factor can be selected to be-20 to-50, and the amplitude limiting link comprises an amplitude limiting voltage upper limit value 0 and an amplitude limiting voltage lower limit value-1. And (3) adding the original low-frequency side alternating voltage amplitude reference value of the land frequency conversion station with the target voltage regulating value, outputting a new low-frequency side alternating voltage amplitude reference value, regulating according to the new low-frequency side alternating voltage amplitude reference value, and avoiding that the new low-frequency side alternating voltage amplitude reference value deviates by 1.0p.u. too much through a limiting link. The degree of the rise of the direct current voltage can be reflected by comparing the direct current voltage signal value with a preset second threshold value, if the direct current voltage signal value is larger than the preset second threshold value after adjustment, the condition that the alternating current fault at the power frequency side is serious is indicated, and an alternating current energy consumption device is required to be put into parallel connection at the alternating current bus at the low frequency side of the land frequency conversion station, wherein the second threshold value can be set to be 1.1p.u.. If the output first control signal value is 0, the land frequency conversion station keeps the current amplitude reference value of the alternating voltage at the low frequency side.
Specifically, substep S2 comprises:
if the initial voltage regulating value is larger than the preset limiting voltage upper limit value through the limiting link, taking the limiting voltage upper limit value as a target voltage regulating value;
if the initial voltage regulating value is less than the preset limiting voltage lower limit value through the limiting link, taking the limiting voltage lower limit value as a target voltage regulating value;
and if the initial voltage regulating value is judged to be not smaller than the lower limit value of the preset limiting voltage and not larger than the upper limit value of the preset limiting voltage through the limiting link, taking the initial voltage regulating value as a target voltage regulating value.
In the embodiment of the invention, whether the initial voltage regulating value is larger than the preset limiting voltage upper limit value is judged through the limiting link, if so, the limiting voltage upper limit value is used as the target voltage regulating value, if not, whether the initial voltage regulating value is smaller than the preset limiting voltage lower limit value is judged, if so, the limiting voltage lower limit value is used as the target voltage regulating value, and if not, the initial voltage regulating value is used as the target voltage regulating value.
Preferably, the process for determining the target rated capacity of the ac power consumer includes:
obtaining a simulation model of an offshore wind power low-frequency alternating current sending system;
when the simulation model is in the power frequency side alternating current fault state, inputting an alternating current energy consumption device with the same rated capacity as the modularized multi-level matrix converter, and determining a target state value;
when the simulation model is in the power frequency side alternating current fault state, after the low frequency side alternating current voltage amplitude reference value of the simulation model is adjusted, the rated capacity of the alternating current energy consumption device is adjusted in an iteration mode until a rated capacity critical value meeting a target state value is obtained;
and constructing target rated capacity by taking the sum value of the rated capacity critical value and the preset capacity margin and the rated capacity critical value as interval endpoints.
The rated capacity critical value is mapped to the condition that the rated capacity of the alternating current energy consumption device is larger than or equal to the rated capacity critical value and meets the target state value, and the rated capacity of the alternating current energy consumption device is smaller than the rated capacity critical value and does not meet the target state value.
In the embodiment of the invention, when the offshore wind power low-frequency alternating current transmission system has a power frequency side alternating current fault state, the amplitude reference value of the low-frequency side alternating current voltage is firstly regulated, and then the input of the alternating current energy consumption device is considered, so that the rated capacity of the alternating current energy consumption device can be reduced, wherein the actual input rated capacity of the alternating current energy consumption device in the offshore wind power low-frequency alternating current transmission system can be simulated to determine the target rated capacity. The method comprises the steps of simulating a power frequency side alternating current fault state in a simulation model corresponding to an offshore wind power low-frequency alternating current sending system, inputting an alternating current energy consumption device which is 100% of the rated capacity of a modularized multi-level matrix type converter, determining a target state value, firstly adjusting an original low-frequency side alternating current voltage amplitude reference value of an onshore frequency conversion station in the same state in the simulation model, continuously adjusting the rated capacity of the alternating current energy consumption device until a rated capacity critical value meeting the target state value is determined, for example, 20% of the rated capacity of the modularized multi-level matrix type converter, taking a certain margin design into consideration, carrying out sum value operation on the rated capacity critical value and a preset capacity margin, for example, 30% of the rated capacity of the modularized multi-level matrix type converter, and constructing a target rated capacity which is 20% -30% of the rated capacity of the modularized multi-level matrix type converter together with the rated capacity critical value as an interval endpoint. The target state value may be set to be a sub-module capacitance overvoltage value of the bridge arm after the fault, for example, 1.15p.u. that is, the sub-module capacitance overvoltage value of the bridge arm after the fault is 1.15 times of the rated value of the bridge arm sub-module capacitance voltage.
In the embodiment of the invention, the three-phase alternating-current voltage instantaneous value at the power frequency side of the land frequency conversion station and the submodule capacitor voltage instantaneous value of the modularized multi-level matrix converter are detected in real time; calculating an alternating voltage signal value by adopting a power frequency side three-phase alternating voltage instantaneous value, and performing hysteresis loop segment processing on the alternating voltage signal value to determine whether a power frequency side alternating current fault exists; when the AC fault on the power frequency side is determined to exist, calculating a DC voltage signal value by adopting the instantaneous value of the capacitance voltage of the submodule; based on the direct-current voltage signal value, fault adjustment is carried out by updating the low-frequency side alternating-current voltage amplitude reference value of the land frequency conversion station or putting into an alternating-current energy consumption device. In the whole process of the power frequency side alternating current fault coordination control of the offshore wind power low-frequency alternating current sending-out system, the amplitude reference value of the alternating current voltage at the low frequency side is regulated to be combined with the input alternating current energy consumption device for fault regulation, so that the implementation is simple, the applicability is strong, the rated capacity of the input alternating current energy consumption device can be effectively reduced, the equipment investment and the operation and maintenance cost are obviously reduced, and the economy of the whole offshore wind power low-frequency alternating current sending-out system is improved.
Referring to fig. 5, fig. 5 is a block diagram illustrating a fault adjustment device for an offshore wind power low-frequency ac transmission system according to an embodiment of the present invention.
The embodiment of the invention provides a fault adjusting device of an offshore wind power low-frequency alternating current transmission system, which comprises an onshore frequency conversion station based on a modularized multi-level matrix converter, wherein two ends of the onshore frequency conversion station are respectively connected with a low-frequency side and a power frequency side; the device comprises:
the parameter detection module 501 is used for detecting the power frequency side three-phase alternating voltage instantaneous value of the land frequency conversion station and the submodule capacitance voltage instantaneous value of the modularized multi-level matrix converter in real time;
the fault judging module 502 is configured to calculate an ac voltage signal value by using an instantaneous value of the three-phase ac voltage at the power frequency side, and perform hysteresis loop processing on the ac voltage signal value to determine whether there is a power frequency side ac fault;
a dc voltage signal value calculating module 503, configured to calculate a dc voltage signal value by using the instantaneous value of the capacitance voltage of the submodule when it is determined that the ac fault on the power frequency side exists;
the fault adjustment module 504 is configured to perform fault adjustment by updating a low-frequency ac voltage amplitude reference value of the land-based frequency conversion station or putting into an ac power consumption device based on the dc voltage signal value.
Optionally, the fault determination 502 is specifically configured to:
after square sum operation is carried out on the three-phase alternating voltage instantaneous value at the power frequency side, square operation is carried out, a first low-pass filter is input for filtering treatment, and an alternating voltage signal value is output;
when the alternating voltage signal value is smaller than the hysteresis voltage lower limit value of the hysteresis loop for the first time, outputting a first control signal value with the power frequency side alternating current fault;
when the alternating voltage signal value is greater than or equal to the hysteresis voltage lower limit value of the hysteresis loop, or when the alternating voltage signal value is greater than the hysteresis voltage upper limit value of the hysteresis loop after outputting the first control signal value with the power frequency side alternating current fault, outputting the first control signal value without the power frequency side alternating current fault.
Optionally, the modular multilevel matrix converter comprises a plurality of bridge arms, and each bridge arm is cascaded with a plurality of sub-modules; the dc voltage signal value calculating module 503 is specifically configured to:
square sum operation is carried out on the instantaneous values of the capacitor voltage of the plurality of sub-modules associated with each bridge arm respectively, and a plurality of square sum values of the instantaneous values of the capacitor voltage are generated;
and after the square sum value of all the capacitor voltage instantaneous values is adopted for open square operation, the total number of sub-modules related to the modularized multi-level matrix converter is subjected to ratio operation, and a second low-pass filter is input for filtering processing to output a direct-current voltage signal value.
Optionally, the fault-adjustment module 504 includes:
the initial voltage regulating value generating unit is used for generating an initial voltage regulating value by performing a multiplication operation with a preset proportionality coefficient after performing a difference operation by adopting a direct-current voltage signal value and a preset first threshold value when the power frequency side alternating-current fault is determined to exist;
the limiting processing unit is used for carrying out limiting link processing on the initial voltage regulating value and determining a target voltage regulating value;
the voltage amplitude adjusting unit is used for acquiring a low-frequency side alternating voltage amplitude reference value of the land frequency conversion station, carrying out addition operation on the low-frequency side alternating voltage amplitude reference value and a target voltage adjusting value, outputting a new low-frequency side alternating voltage amplitude reference value and adjusting the new low-frequency side alternating voltage amplitude reference value;
and the alternating current energy consumption device input unit is used for inputting the alternating current energy consumption device if the direct current voltage signal value is larger than a preset second threshold value after the new low-frequency side alternating current voltage amplitude reference value is adopted for adjustment.
Optionally, the clipping processing unit is specifically configured to:
if the initial voltage regulating value is larger than the preset limiting voltage upper limit value through the limiting link, taking the limiting voltage upper limit value as a target voltage regulating value;
if the initial voltage regulating value is less than the preset limiting voltage lower limit value through the limiting link, taking the limiting voltage lower limit value as a target voltage regulating value;
and if the initial voltage regulating value is judged to be not smaller than the lower limit value of the preset limiting voltage and not larger than the upper limit value of the preset limiting voltage through the limiting link, taking the initial voltage regulating value as a target voltage regulating value.
Optionally, the determining of the target rated capacity of the ac power consumer includes:
obtaining a simulation model of an offshore wind power low-frequency alternating current sending system;
when the simulation model is in the power frequency side alternating current fault state, inputting an alternating current energy consumption device with the same rated capacity as the modularized multi-level matrix converter, and determining a target state value;
when the simulation model is in the power frequency side alternating current fault state, after the low frequency side alternating current voltage amplitude reference value of the simulation model is adjusted, the rated capacity of the alternating current energy consumption device is adjusted in an iteration mode until a rated capacity critical value meeting a target state value is obtained;
and constructing target rated capacity by taking the sum value of the rated capacity critical value and the preset capacity margin and the rated capacity critical value as interval endpoints.
It will be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working process of the apparatus and modules described above may refer to the corresponding process in the foregoing method embodiment, which is not repeated herein.
In the several embodiments provided in this application, it should be understood that the disclosed apparatus and method may be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative, e.g., the division of the units is merely a logical function division, and there may be additional divisions when actually implemented, e.g., multiple units or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be an indirect coupling or communication connection via some interfaces, devices or units, which may be in electrical, mechanical or other form.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
The above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. The fault adjustment method of the offshore wind power low-frequency alternating current transmission system is characterized in that the offshore wind power low-frequency alternating current transmission system comprises an onshore frequency conversion station based on a modularized multi-level matrix converter, and two ends of the onshore frequency conversion station are respectively connected with a low-frequency side and a power frequency side; the method comprises the following steps:
detecting the power frequency side three-phase alternating-current voltage instantaneous value of the land frequency conversion station and the submodule capacitance voltage instantaneous value of the modularized multi-level matrix converter in real time;
calculating an alternating voltage signal value by adopting the power frequency side three-phase alternating voltage instantaneous value, and performing hysteresis loop processing on the alternating voltage signal value to determine whether a power frequency side alternating current fault exists;
when the AC fault on the power frequency side is determined to exist, calculating a DC voltage signal value by adopting the instantaneous value of the capacitance voltage of the submodule;
based on the direct-current voltage signal value, fault adjustment is carried out by updating a low-frequency side alternating-current voltage amplitude reference value of the land frequency conversion station or putting into an alternating-current energy consumption device.
2. The method for adjusting faults in an offshore wind power low frequency ac transmission system of claim 1, wherein the step of calculating an ac voltage signal value using the instantaneous value of the power frequency side three-phase ac voltage and performing a hysteresis loop process on the ac voltage signal value to determine whether a power frequency side ac fault exists comprises:
after square sum operation is carried out on the three-phase alternating voltage instantaneous value at the power frequency side, square operation is carried out, a first low-pass filter is input for filtering treatment, and an alternating voltage signal value is output;
when the alternating voltage signal value is smaller than the hysteresis voltage lower limit value of the hysteresis loop node for the first time, outputting a first control signal value with the power frequency side alternating current fault;
and outputting a first control signal value without the power frequency side alternating current fault when the alternating current voltage signal value is greater than or equal to the hysteresis voltage lower limit value of the hysteresis loop or the alternating current voltage signal value is greater than the hysteresis voltage upper limit value of the hysteresis loop after outputting the first control signal value with the power frequency side alternating current fault.
3. The fault adjustment method of an offshore wind power low frequency ac transmission system according to claim 1, wherein the modular multilevel matrix converter comprises a plurality of bridge arms, each of the bridge arms cascading a plurality of sub-modules; when it is determined that an ac fault exists at the power frequency side, the step of calculating a dc voltage signal value by using the instantaneous value of the capacitance voltage of the submodule includes:
square sum operation is carried out on the instantaneous values of the capacitor voltage of the plurality of sub-modules associated with each bridge arm respectively, and a plurality of square sum values of the instantaneous values of the capacitor voltage are generated;
and after the square sum value of all the capacitor voltage instantaneous values is adopted for open square operation, the total number of the submodules associated with the modularized multi-level matrix converter is subjected to ratio operation, and a second low-pass filter is input for filtering processing to output a direct-current voltage signal value.
4. The fault adjustment method for a low frequency ac power transmission system for offshore wind power according to claim 1, wherein the step of performing fault adjustment by updating a low frequency side ac voltage amplitude reference value of the land-based inverter or putting into ac power consumption means based on the dc voltage signal value comprises:
when the power frequency side alternating current fault is determined to exist, performing difference value operation by adopting the direct current voltage signal value and a preset first threshold value, and performing multiplication operation by adopting a preset proportionality coefficient to generate an initial voltage regulating value;
performing amplitude limiting link processing on the initial voltage regulating value to determine a target voltage regulating value;
acquiring a low-frequency side alternating voltage amplitude reference value of the land frequency conversion station, carrying out addition operation on the low-frequency side alternating voltage amplitude reference value and the target voltage regulating value, outputting a new low-frequency side alternating voltage amplitude reference value and regulating the new low-frequency side alternating voltage amplitude reference value;
after the new low-frequency side alternating current voltage amplitude reference value is adopted for adjustment, if the direct current voltage signal value is larger than a preset second threshold value, an alternating current energy consumption device is put into.
5. The method for adjusting the fault of the offshore wind power low-frequency ac transmission system according to claim 4, wherein the step of performing a clipping process on the initial voltage adjustment value to determine a target voltage adjustment value comprises:
if the initial voltage regulating value is judged to be larger than the preset limiting voltage upper limit value through the limiting link, the limiting voltage upper limit value is used as a target voltage regulating value;
if the initial voltage regulating value is less than the preset limiting voltage lower limit value through the limiting link, taking the limiting voltage lower limit value as a target voltage regulating value;
and if the initial voltage regulating value is judged to be not smaller than the lower limit value of the preset limiting voltage and not larger than the upper limit value of the preset limiting voltage through the limiting link, taking the initial voltage regulating value as a target voltage regulating value.
6. The method for adjusting the fault of the offshore wind power low frequency ac transmission system according to claim 4, wherein the determining the target rated capacity of the ac power consumption device comprises:
obtaining a simulation model of the offshore wind power low-frequency alternating current transmission system;
when the simulation model is in an alternating current fault state at the power frequency side, inputting an alternating current energy consumption device with the same rated capacity as the modularized multi-level matrix converter, and determining a target state value;
when the simulation model is in a power frequency side alternating current fault state, after the low frequency side alternating current voltage amplitude reference value of the simulation model is adjusted, the rated capacity of an alternating current energy consumption device is iteratively adjusted until a rated capacity critical value meeting the target state value is obtained;
and constructing target rated capacity by taking the sum value of the rated capacity critical value and the preset capacity margin and the rated capacity critical value as interval endpoints.
7. The fault adjusting device of the offshore wind power low-frequency alternating current transmission system is characterized by comprising an onshore frequency conversion station based on a modularized multi-level matrix converter, wherein two ends of the onshore frequency conversion station are respectively connected with a low-frequency side and a power frequency side; the device comprises:
the parameter detection module is used for detecting the power frequency side three-phase alternating voltage instantaneous value of the land frequency conversion station and the submodule capacitance voltage instantaneous value of the modularized multi-level matrix converter in real time;
the fault judging module is used for calculating an alternating voltage signal value by adopting the power frequency side three-phase alternating voltage instantaneous value, carrying out hysteresis loop processing on the alternating voltage signal value and determining whether a power frequency side alternating current fault exists or not;
the direct-current voltage signal value calculation module is used for calculating a direct-current voltage signal value by adopting the instantaneous value of the capacitance voltage of the submodule when the fact that the power frequency side alternating-current fault exists is determined;
and the fault adjustment module is used for carrying out fault adjustment by updating the low-frequency side alternating current voltage amplitude reference value of the land frequency conversion station or putting into an alternating current energy consumption device based on the direct current voltage signal value.
8. The fault adjustment device of an offshore wind power low frequency ac transmission system according to claim 7, wherein the fault determination module is specifically configured to:
after square sum operation is carried out on the three-phase alternating voltage instantaneous value at the power frequency side, square operation is carried out, a first low-pass filter is input for filtering treatment, and an alternating voltage signal value is output;
when the alternating voltage signal value is smaller than the hysteresis voltage lower limit value of the hysteresis loop node for the first time, outputting a first control signal value with the power frequency side alternating current fault;
and outputting a first control signal value without the power frequency side alternating current fault when the alternating current voltage signal value is greater than or equal to the hysteresis voltage lower limit value of the hysteresis loop or the alternating current voltage signal value is greater than the hysteresis voltage upper limit value of the hysteresis loop after outputting the first control signal value with the power frequency side alternating current fault.
9. The fault adjustment device of an offshore wind power low frequency ac transmission system according to claim 7, wherein the modular multilevel matrix converter comprises a plurality of bridge arms, each of the bridge arms cascading a plurality of sub-modules; the direct-current voltage signal value calculation module is specifically used for:
square sum operation is carried out on the instantaneous values of the capacitor voltage of the plurality of sub-modules associated with each bridge arm respectively, and a plurality of square sum values of the instantaneous values of the capacitor voltage are generated;
and after the square sum value of all the capacitor voltage instantaneous values is adopted for open square operation, the total number of the submodules associated with the modularized multi-level matrix converter is subjected to ratio operation, and a second low-pass filter is input for filtering processing to output a direct-current voltage signal value.
10. The fault adjustment device of an offshore wind power low frequency ac export system according to claim 7, wherein the fault adjustment module comprises:
the initial voltage regulating value generating unit is used for generating an initial voltage regulating value by carrying out multiplication operation on the difference value operation between the direct current voltage signal value and a preset first threshold value and the preset proportionality coefficient when the power frequency side alternating current fault is determined to exist;
the amplitude limiting processing unit is used for carrying out amplitude limiting link processing on the initial voltage regulating value and determining a target voltage regulating value;
the voltage amplitude adjusting unit is used for acquiring a low-frequency side alternating voltage amplitude reference value of the land frequency conversion station, carrying out addition operation on the low-frequency side alternating voltage amplitude reference value and the target voltage adjusting value, outputting a new low-frequency side alternating voltage amplitude reference value and adjusting the new low-frequency side alternating voltage amplitude reference value;
and the alternating current energy consumption device input unit is used for inputting the alternating current energy consumption device if the direct current voltage signal value is larger than a preset second threshold value after the new low-frequency side alternating current voltage amplitude reference value is adopted for adjustment.
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| CN202311624353.4A CN117638899A (en) | 2023-11-29 | 2023-11-29 | Fault adjustment method and device for offshore wind power low-frequency alternating current sending-out system |
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