CN114977285A - System, method, equipment and storage medium for direct current transmission of wind power grid diode - Google Patents
System, method, equipment and storage medium for direct current transmission of wind power grid diode 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
- H02J3/38—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
- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
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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
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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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
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
- H02J2003/365—Reducing harmonics or oscillations in HVDC
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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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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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Abstract
The invention provides a wind power grid diode direct current sending system, a method, equipment and a storage medium, wherein the system comprises: the direct current input end of the multi-fan grid side converter is connected with a machine side converter direct current bus capacitor, and the alternating current output end of the multi-fan grid side converter is connected with an alternating current collection network of a wind power plant; the alternating current input end of the twelve-pulse diode rectifier is connected to a public coupling point of an alternating current collection network of a wind power plant through a converter transformer, the direct current output end is connected to the positive end and the negative end of a direct current transmission line to serve as a rectifier station, and the reactive compensation filter device is connected to the public coupling point of the alternating current collection network of the wind power plant; the direct-current input end of the direct-current voltage variable modular multilevel converter receives rectified wind power through a direct-current transmission line, and the alternating-current output end of the direct-current voltage variable modular multilevel converter is connected to a receiving-end power grid through direct-current-alternating-current inversion to realize wind power grid connection. The invention improves the reliability of the alternating current network-building system of the fan, and leads the classic alternating current system control theory to be applicable to the diode sending-out system of the fan network-building.
Description
Technical Field
The invention relates to the field of wind power plant direct current transmission, in particular to a wind power plant grid diode direct current transmission system, method equipment and storage medium.
Background
The large-scale centralized wind power integration is an important means for promoting the double-carbon target and realizing the sustainable development of clean energy in China. The wind power is transmitted by direct current and is connected to the grid, large-scale long-distance wind power transmission can be achieved, and the wind power transmission system is particularly suitable for the field of offshore wind power transmission. However, the traditional modular multilevel converter platform based on the full-control device has the defects of high cost, large volume and heavy weight, and is more prominent in the future offshore wind power scene. Therefore, a wind power integration scheme based on diode direct current output appears.
For the wind power diode direct current sending scheme, the key problem is the network construction control problem of an alternating current wind power plant. Because the diode does not have the network-building function, the control strategy of the fan converter needs to be changed, and therefore the fan converter becomes a network-building type fan. The grid-structured fan can play the role of establishing alternating voltage and frequency of a wind power plant and simultaneously can meet the functions of active output control, reactive power distribution control and the like. The wind power grid control applied to diode direct current output is a problem to be researched and solved at present.
In the existing wind turbine grid-building diode direct-current sending-out system, the most important mode is that the wind turbine adopts a grid-building control technology to realize the control of the voltage and the frequency of an alternating-current system of a wind power plant. Because the active output of the diode rectifier is realized by controlling the voltage of the alternating-current grid-connected point, the active output is controlled by controlling the voltage of the machine terminal. One of the modes is an active-voltage and reactive-frequency droop control method, wherein the voltage of a controller realizes active control, and the frequency of the controller end realizes reactive distribution. This approach, however, results in a strong active-reactive coupling because, as in conventional ac systems, the active flow between machines is frequency dependent and the reactive flow is voltage dependent. The other method adopts active-frequency and reactive-voltage droop control, meanwhile, the machine-end measuring frequency is added with an entering voltage instruction through a PI controller, and the added quantity is utilized to adjust the alternating voltage of the grid-connected point of the diode so as to realize the control of the output active of the diode. Although this method reduces the coupling between active and reactive power, the reactive and active power still have coupling due to different frequencies at the machine end, and the PI integrator may bring about the error of reactive power distribution.
At present, a receiving end of a diode direct current sending-out system adopts a modular multilevel converter. However, the converter adopts a constant direct-current voltage control mode to maintain the voltage of a direct-current system to be constant, and the active power output by the diode rectifier is realized by controlling the voltage of an alternating-current power grid of the wind power plant by a fan.
The basic reason that the active and reactive decoupling control of a fan network cannot be well realized by the existing method is that on one hand, a fan needs to bear the active-frequency and reactive-voltage-based regulation characteristics of the traditional alternating current power grid, and on the other hand, due to the existence of a diode as a rectifying device, the total active regulation needs to be regulated through network voltage. The three-control-dimension wind power grid current converter is difficult to realize simultaneously. In fact, the control of the active power of the diode can also be realized by adjusting direct-current voltage, therefore, the alternating-current voltage of the wind power grid alternating-current system does not need to be changed, a wind power grid converter can be simplified into a traditional grid control design, and active and reactive decoupling is naturally realized. In order to regulate the dc voltage, a modular multilevel converter with variable dc voltage may be used as an inverter station, for example, a hybrid modular multilevel converter with a small number of full-bridge ratios.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.
Therefore, the invention provides a wind turbine grid-connected diode direct current sending-out system in a first aspect, which utilizes the regulation capacity of a direct current receiving end variable voltage type modular multilevel converter to diode power, combines the grid-connected control of a designed wind turbine converter, realizes active and reactive decoupling control of a wind turbine grid-connected alternating current system, improves the reliability of the wind turbine grid-connected alternating current system, and enables a classical alternating current system control theory to be applicable to the wind turbine grid-connected diode sending-out system.
The second aspect of the invention provides a control method for a wind power grid diode direct current sending-out system.
A third aspect of the invention is directed to a computer device.
A fourth aspect of the present invention is directed to a storage medium.
An embodiment of a first aspect of the present invention provides a wind power grid diode direct current sending system, including: the wind power generation system comprises a fan grid side converter, a twelve-pulse diode rectifier, a reactive compensation filtering device and a direct-current voltage variable modular multilevel converter, wherein the direct-current input end of the fan grid side converter is connected with a machine side converter direct-current bus capacitor, and the alternating-current output end of the fan grid side converter is connected to an alternating-current collecting network of a wind power plant and used for acquiring direct-current-alternating-current inversion of wind power; the alternating current input end of the twelve-pulse diode rectifier is connected to a public coupling point of an alternating current collecting network of a wind power plant through a converter transformer, and the direct current output end is connected to the positive end and the negative end of a direct current transmission line to serve as a rectifier station and used for realizing alternating current-direct current rectification of wind power of the wind power plant; the reactive compensation filtering device is connected to a public coupling point of the alternating current collection network of the wind power plant; the direct-current input end of the direct-current voltage variable modular multilevel converter receives rectified wind power through a direct-current power transmission line, and the alternating-current output end of the direct-current voltage variable modular multilevel converter is connected to a receiving-end power grid through direct-current-alternating-current inversion, so that wind power grid connection is realized.
The wind power grid diode direct current sending-out system provided by the embodiment of the invention realizes active and reactive decoupling control of a wind power grid alternating current system, improves the reliability of the wind power grid alternating current system, and enables a classical alternating current system control theory to be suitable for the wind power grid diode sending-out system.
The embodiment of the second aspect of the invention provides a direct current sending method for a wind power grid diode, which comprises the following steps:
connecting a direct current input end of a fan grid side converter with a direct current bus capacitor of a machine side converter, and connecting an alternating current output end of the fan grid side converter with an alternating current collecting network of a wind power plant to obtain direct current-alternating current inversion of wind power; the AC input end of a twelve-pulse diode rectifier is connected to a public coupling point of an AC current collection network of a wind power plant through a converter transformer, and the DC output end is connected to the positive end and the negative end of a DC power transmission line to be used as a rectifier station, so that AC-DC rectification of wind power of the wind power plant is realized; connecting a reactive compensation filtering device to a public coupling point of an alternating current collection network of the wind power plant; and receiving the rectified wind power at the direct current input end of the direct current voltage variable modular multilevel converter through a direct current transmission line, and connecting the alternating current output end to a receiving end power grid through the direct current-alternating current inversion to realize wind power grid connection.
The control method of the wind turbine grid diode direct current sending-out system in the embodiment of the invention realizes active and reactive decoupling control of a wind turbine grid alternating current system, improves the reliability of the wind turbine grid alternating current system, and enables a classic alternating current system control theory to be suitable for the wind turbine grid diode sending-out system.
An embodiment of a third aspect of the present invention provides a computer device, including a processor and a memory; the processor runs a program corresponding to the executable program code by reading the executable program code stored in the memory, so as to realize the control method of the wind mechanism network diode direct current sending system.
A fourth embodiment of the present invention provides a non-transitory computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements a control method for a wind-grid diode dc sending system as described above.
The invention has the beneficial effects that:
the overall output power of the wind power plant is regulated by changing the direct-current voltage by using an inversion-side direct-current voltage variable modular multilevel converter. At the moment, the voltage of the alternating current power grid of the diode rectifier does not need to be regulated, the wind power grid converter is simplified into a classical grid control strategy, and active decoupling and reactive decoupling are completely realized. This results in improved control performance and simplified controller design. Meanwhile, the characteristics of the wind power plant alternating current system adopting the method are similar to those of the traditional alternating current network construction system, the reliability is improved, and the corresponding classical analysis mode can be directly used for guiding analysis design.
Because the direct-current voltage variation range of the diode rectification direct-current system is small, the large-range control of power can be realized, so that the inverter side can adopt a mixed MMC formed by full-bridge sub modules in a small proportion, and the cost is not obviously increased.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic structural diagram of a wind power grid diode dc output system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a wind turbine grid side converter according to an embodiment of the present invention;
fig. 3 is a schematic diagram of a dc transmission twelve-ripple thyristor converter according to an embodiment of the invention;
FIG. 4 is a schematic structural diagram of an alternating current reactive compensation and filtering device of a wind farm according to one embodiment of the invention;
fig. 5 is a schematic diagram of a dc voltage variable modular multilevel converter according to an embodiment of the invention;
FIG. 6 is a schematic diagram of a half-bridge submodule structure according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a full bridge submodule structure according to an embodiment of the present invention;
FIG. 8 is a flow chart of a control method for a wind turbine grid diode DC output system according to an embodiment of the present invention;
FIG. 9 is a schematic block diagram of a wind turbine grid side converter control according to an embodiment of the present invention;
FIG. 10 is a schematic diagram of frequency detection according to one embodiment of the present invention;
fig. 11 is a schematic diagram of a dc transmission inverter side converter control according to an embodiment of the invention.
FIG. 12 is a computer device according to one embodiment of the invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
A wind grid diode dc-out system, method, apparatus, and storage medium according to embodiments of the present invention are described below with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of a wind turbine grid diode dc output system according to an embodiment of the present invention.
As shown in fig. 1, the wind grid diode dc transmission system includes: a fan network side converter 100, a twelve-pulse diode rectifier 200, a reactive compensation filtering device 300 and a direct current voltage variable type modularized multi-level converter 400, wherein,
the direct current input end of the fan grid side converter 100 is connected with a machine side converter direct current bus capacitor, and the alternating current output end is connected with an alternating current collecting network of a wind power plant and used for acquiring direct current-alternating current inversion of wind power;
an alternating current input end of the twelve-pulse diode rectifier 200 is connected to a public coupling point of an alternating current collection network of the wind power plant through a converter transformer, and a direct current output end is connected to positive and negative ends of a direct current transmission line to serve as a rectifier station and is used for realizing alternating current-direct current rectification of wind power of the wind power plant;
the reactive compensation filtering device 300 is connected to a public coupling point of an alternating current collection network of the wind power plant;
the direct-current input end of the direct-current voltage variable modular multilevel converter 400 receives the rectified wind power through a direct-current transmission line, and the alternating-current output end is connected to a receiving-end power grid through direct-current-alternating-current inversion, so that wind power grid connection is realized.
Further, the structures of the wind turbine grid-side converter 100, the twelve-pulse diode rectifier 200 and the reactive compensation filtering device 300 of the present invention are shown in fig. 2, fig. 3 and fig. 4, respectively.
Specifically, the fan grid side converter 100 of the present invention implements dc-ac inversion of wind power captured by each fan. The direct current input end of the wind power plant is connected with a machine side converter direct current bus capacitor, and the alternating current output end of the wind power plant is connected with an alternating current collection network of the wind power plant. Then, the twelve-pulse diode rectifier 200 collects the alternating current wind power of the wind power plant to realize alternating current-direct current rectification of the wind power plant. An alternating current input end of the wind power plant is connected to a public coupling Point (PCC) of an alternating current collection network of the wind power plant through a converter transformer, and a direct current output end of the wind power plant is connected to a positive end and a negative end of a direct current transmission line and serves as a direct current rectifier station. Since the twelve-pulse diode rectifier 200 can generate alternating current reactive power and harmonic waves, the reactive power compensation filtering device 300 is arranged and is also connected to the wind farm alternating current PCC. The wind power is rectified by the twelve-pulse diode rectifier 200, then is connected to the receiving-end direct-current voltage variable modular multilevel converter 400 through the direct-current transmission line, is connected to the receiving-end power grid through the direct-current-alternating-current inversion and the alternating-current output end, and finally achieves wind power grid connection. The invention also needs a frequency detection communication unit, firstly detects the alternating current grid frequency at the alternating current PCC of the wind farm, and then transmits the alternating current grid frequency to the direct current voltage variable modular multilevel converter 400 through a communication mode for regulating the direct current voltage.
Further, as shown in fig. 5, each phase of the dc voltage variable modular multilevel converter 400 includes an upper bridge arm and a lower bridge arm, each bridge arm is composed of N identical full-controlled half-bridge voltage source sub-modules, as shown in fig. 6, and F identical full-controlled full-bridge voltage source sub-modules are cascaded as shown in fig. 7, the lower end of the upper bridge arm and the upper end of the lower bridge arm of each phase are respectively connected together through an inductor L, the middle point of the inductor becomes an ac output end of the phase, the upper ends of the upper bridge arms of all the phases are connected together to become a dc positive end, and the lower ends of the lower bridge arms of all the phases are connected together to become a dc negative end.
The direct current sending-out system of the wind turbine grid-connected diode realizes active and reactive decoupling control of a wind turbine grid-connected alternating current system, improves the reliability of the wind turbine grid-connected alternating current system, and enables a classic alternating current system control theory to be suitable for the wind turbine grid-connected diode sending-out system.
Next, a control method of a wind turbine grid diode dc-out system according to an embodiment of the present invention is described with reference to the drawings.
Fig. 8 is a flowchart of a control method of a wind turbine grid diode dc-out system according to an embodiment of the present invention.
As shown in fig. 8, the method includes:
s1, connecting a direct current input end of a fan grid side converter with a side converter direct current bus capacitor, and connecting an alternating current output end with an alternating current collecting network of a wind power plant to obtain direct current-alternating current inversion of wind power;
s2, an alternating current input end of a twelve-pulse diode rectifier is connected to a public coupling point of an alternating current collecting network of a wind power plant through a converter transformer, and a direct current output end is connected to positive and negative ends of a direct current transmission line to serve as a rectifier station, so that alternating current-direct current rectification of wind power of the wind power plant is realized;
s3, connecting the reactive compensation filter device to a public coupling point of an alternating current collection network of the wind power plant;
and S4, receiving the rectified wind power at the direct current input end of the direct current voltage variable modular multilevel converter through a direct current transmission line, and connecting the alternating current output end to a receiving-end power grid through direct current-alternating current inversion to realize wind power grid connection.
Specifically, the method of the embodiment of the invention is explained in detail according to the attached drawings.
As shown in fig. 9, fig. 9 is a control method of a wind turbine grid-side converter according to an embodiment of the present invention, including the following steps:
(1) setting active power reference value P output by fan network side converter ref (the reference value is usually from a direct current capacitor voltage control outer ring of the fan converter), active power P output by the fan grid side converter is collected, and a power deviation signal delta P is calculated to be P ref -P；
(2) The power deviation signal delta P passes through a proportional controller and then is compared with a reference frequency omega 0 Summing to obtain a frequency reference value omega;
(3) blower fan net sideIntegrating the frequency reference value omega of the converter with time to obtain a phase reference value theta u ；
(4) Setting reactive power reference value Q output by fan network side converter ref (the reference value can be set to be 0), reactive power Q output by the fan grid side converter is collected, and a reactive deviation signal delta Q is calculated to be Q ref -Q；
(5) The power deviation signal delta Q is processed by a proportional controller and then is compared with a reference voltage u 0 Summing to obtain a voltage reference value u;
(6) and (3) carrying out current amplitude limiting and damping control on the voltage and phase reference value of the fan grid side converter to obtain the amplitude e and the phase theta of the internal potential of the final converter e ；
(7) Calculating to obtain a three-phase internal potential reference value e of the fan grid side converter a 、e b 、e c ：
(8) The three-phase internal potential reference voltage e of the fan network side converter is used a 、e b 、e c And sending the signals into a pulse width modulation link to obtain a control pulse signal of the fan grid side converter.
As shown in fig. 10, fig. 10 is a method for detecting the frequency of the ac collecting network of the wind farm and communicating the detected frequency to the dc transmission dc voltage variable modular multilevel converter according to the embodiment of the present invention, which includes the following steps:
(1) collecting three-phase voltage instantaneous value u at public coupling point of diode rectifier of alternating current collection network of wind power plant sa 、u sb 、u sc Inputting the frequency to a frequency detection unit to obtain a power grid frequency omega;
(2) and transmitting the frequency to the direct current transmission direct current voltage variable modular multilevel converter in a communication mode.
As shown in fig. 11, fig. 11 is a control method of a dc transmission hybrid converter according to an embodiment of the present invention, including the following steps:
(1) setting wind farm AC collectionNetwork frequency reference value omega 0 Calculating a frequency deviation signal [ omega ] -omega from the frequency measurement [ omega ] obtained by the communication 0 ；
(2) After the sub-module capacitor voltage deviation signal delta omega passes through a proportional-integral controller, a direct-current voltage reference value U of the direct-current voltage variable modular multilevel converter is obtained dc_ref ；
(3) Setting the voltage value of the capacitor of the submodule of the direct-current voltage variable modular multilevel converter to be U cap_ref Collecting all the sub-module capacitor voltages of the direct-current voltage variable modular multilevel converter to calculate to obtain a sub-module capacitor voltage average value u cap Calculating the sub-module capacitance voltage deviation signal delta u cap ＝U cap_ref -u cap ；
(4) The sub-module capacitance voltage deviation signal delta u is converted into a voltage deviation signal delta u cap Obtaining an active current amplitude value target value I of the direct-current voltage variable modular multilevel converter after passing through the proportional divider controller p_ref And calculating to obtain a three-phase active current reference value i of the direct-current voltage variable modular multilevel converter p_a_ref 、i p_b_ref 、i p_c_ref ：
(5) Setting reactive active current amplitude value target value I of direct-current voltage variable modular multilevel converter q_ref And calculating to obtain a three-phase reactive current reference value i of the direct-current voltage variable modular multilevel converter q_a_ref 、i q_b_ref 、i q_c_ref ：
(6) According to the three-phase active current reference value i of the direct-current voltage variable modular multilevel converter p_a_ref 、i p_b_ref 、i p_c_ref Reference value i of three-phase reactive current q_a_ref 、i q_b_ref 、i q_c_ref And calculating to obtain the three-phase reference current value i of the direct-current voltage variable modular multilevel converter a_ref 、i b_ref 、i c_ref ：
(7) Three-phase reference current value i of DC voltage variable type modular multilevel converter a_ref 、i b_ref 、i c_ref Inputting the voltage into a current control link to obtain a three-phase alternating voltage reference value u of the direct-current voltage variable modular multilevel converter a_ref 、u b_ref 、u c_ref ；
(8) According to the three-phase AC voltage reference value u a_ref 、u b_ref 、u b_ref And a DC voltage reference value U dc_ref And calculating to obtain reference voltages u of 6 bridge arms of the serial compensation modular multilevel converter ap_ref 、u an_ref 、u bp_ref 、u bn_ref 、u cp_ref 、u cn_ref ：
(9) The reference voltage u of 6 bridge arms of the series compensation modular multilevel converter is used ap_ref ,u an_ref ,u bp_ref ,u bn_ref ,u cp_ref ,u cn_ref And sending the control pulse signal to a pulse width modulation link to obtain a control pulse signal of the direct-current voltage variable modular multilevel converter.
The control method of the wind turbine grid diode direct current sending-out system in the embodiment of the invention realizes active and reactive decoupling control of a wind turbine grid alternating current system, improves the reliability of the wind turbine grid alternating current system, and enables a classic alternating current system control theory to be suitable for the wind turbine grid diode sending-out system.
In order to implement the method of the above embodiment, the present invention further provides a computer device, as shown in fig. 12, the computer device 600 includes a memory 601, a processor 602; wherein the processor 602 runs the program corresponding to the executable program code by reading the executable program code stored in the memory 601, so as to implement the steps of the method described above.
In order to implement the foregoing embodiments, the present application further proposes a non-transitory computer readable storage medium, on which a computer program is stored, and when the program is executed by a processor, the program implements the control method of the wind grid diode dc transmission system according to the foregoing embodiments.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the description of the specification, reference to the description of "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A fan network construction diode direct current send-out system is characterized by comprising: a fan network side converter, a twelve-pulse diode rectifier, a reactive compensation filter device and a direct current voltage variable modular multilevel converter, wherein,
the direct current input end of the fan grid side converter is connected with a direct current bus capacitor of the fan grid side converter, and the alternating current output end of the fan grid side converter is connected with an alternating current collection network of a wind power plant and used for acquiring direct current-alternating current inversion of wind power;
the alternating current input end of the twelve-pulse diode rectifier is connected to a public coupling point of an alternating current collection network of the wind power plant through a converter transformer, and the direct current output end is connected to the positive end and the negative end of a direct current transmission line to serve as a rectifier station and used for realizing alternating current-direct current rectification of wind power of the wind power plant;
the reactive compensation filtering device is connected to a public coupling point of the alternating current collection network of the wind power plant;
the direct-current input end of the direct-current voltage variable modular multilevel converter receives rectified wind power through a direct-current power transmission line, and the alternating-current output end of the direct-current voltage variable modular multilevel converter is connected to a receiving-end power grid through direct-current-alternating-current inversion, so that wind power grid connection is realized.
2. The system of claim 1, further comprising: and the frequency detection communication unit is used for detecting the power grid frequency at the public coupling point of the alternating current collection network of the wind power plant, and transmitting the power grid frequency to the direct current voltage variable modular multilevel converter for direct current voltage regulation.
3. The system of claim 1, wherein each phase of the dc voltage variable modular multilevel converter comprises an upper leg and a lower leg, each leg being formed by a plurality of identical full-controlled half-bridge voltage source submodules cascaded with a plurality of identical full-controlled full-bridge voltage source submodules.
4. The system of claim 3, wherein the lower ends of the upper bridge arms and the upper ends of the lower bridge arms of each phase are connected through inductors, the upper bridge arms of all the phases are connected to serve as positive DC terminals, and the lower bridge arms of all the phases are connected to serve as negative DC terminals.
5. A control method of a wind power grid diode direct current sending system is characterized by comprising the following steps:
connecting a direct current input end of a fan grid side converter with a direct current bus capacitor of a machine side converter, and connecting an alternating current output end of the fan grid side converter with an alternating current collecting network of a wind power plant to obtain direct current-alternating current inversion of wind power;
the AC input end of a twelve-pulse diode rectifier is connected to a public coupling point of an AC current collection network of a wind power plant through a converter transformer, and the DC output end is connected to the positive end and the negative end of a DC power transmission line to be used as a rectifier station, so that AC-DC rectification of wind power of the wind power plant is realized;
connecting a reactive compensation filtering device to a public coupling point of an alternating current collection network of the wind power plant;
and receiving the rectified wind power at the direct current input end of the direct current voltage variable modular multilevel converter through a direct current transmission line, and connecting the alternating current output end to a receiving end power grid through the direct current-alternating current inversion to realize wind power grid connection.
6. The method according to claim 5, wherein the connecting the direct current input end of the wind turbine grid side converter with the direct current bus capacitor of the side converter and the alternating current output end with the wind farm alternating current collecting network to obtain the direct current-alternating current inversion of the wind power comprises:
setting an active power reference value output by the fan grid side converter, collecting the active power output by the fan grid side converter, and calculating a power deviation signal;
summing the power deviation signal and a reference frequency to obtain a frequency reference value;
integrating the frequency reference value with time to obtain a phase reference value;
setting a reactive power reference value output by the fan grid side converter, collecting the reactive power output by the fan grid side converter, and calculating a reactive deviation signal;
summing the power deviation signal and a reference voltage to obtain a voltage reference value;
the voltage reference value and the phase reference value are subjected to current amplitude limiting and damping control on an inner ring to obtain the amplitude and the phase of the internal potential of the converter;
and calculating to obtain three-phase internal potential reference voltage of the fan grid side converter:
and sending the three-phase internal potential reference voltage of the fan grid side converter to a pulse width modulation link to obtain a control pulse signal of the fan grid side converter.
7. The method of claim 5, further comprising:
and acquiring three-phase voltage instantaneous values at the public coupling point of the alternating current collecting network of the wind power plant, inputting the three-phase voltage instantaneous values into a frequency detection communication unit to obtain power grid frequency, and outputting the power grid frequency to the direct current voltage variable modular multilevel converter for direct current voltage regulation.
8. The method according to claim 7, wherein the collecting instantaneous values of three-phase voltage at the point of common coupling of the ac collecting network of the wind farm, inputting the instantaneous values of three-phase voltage to a frequency detection unit to obtain a grid frequency, and inputting the grid frequency to the dc voltage variable modular multilevel converter for dc voltage regulation comprises:
setting a frequency reference value of an alternating current collection network of a wind power plant, and calculating a frequency deviation signal according to the frequency of a power grid;
after the frequency deviation signal passes through a proportional-integral controller, a direct-current voltage reference value of the direct-current voltage variable modular multilevel converter is obtained;
setting a sub-module capacitor voltage value of the direct-current voltage variable modular multilevel converter, collecting all sub-module capacitor voltages of the direct-current voltage variable modular multilevel converter, calculating to obtain a sub-module capacitor voltage average value, and calculating a sub-module capacitor voltage deviation signal;
after the sub-module capacitor voltage deviation signal passes through a proportional divider controller, obtaining an active current amplitude target value of the direct-current voltage variable modular multilevel converter, and calculating to obtain a three-phase active current reference value of the direct-current voltage variable modular multilevel converter:
setting a reactive active current amplitude value target value of the direct-current voltage variable modular multilevel converter, and calculating to obtain a three-phase reactive current reference value of the direct-current voltage variable modular multilevel converter:
according to the three-phase active current reference value and the three-phase reactive current reference value of the direct-current voltage variable modular multilevel converter, calculating to obtain a three-phase reference current value of the direct-current voltage variable modular multilevel converter:
inputting the three-phase reference current value of the direct-current voltage variable modular multilevel converter to a current control link to obtain a three-phase alternating-current voltage reference value of the direct-current voltage variable modular multilevel converter;
calculating reference voltages of a plurality of bridge arms of the series compensation modular multilevel converter according to the three-phase alternating voltage reference value and the direct current voltage reference value;
and sending the reference voltages of a plurality of bridge arms of the series compensation modular multilevel converter to a pulse width modulation link to obtain a control pulse signal of the direct-current voltage variable modular multilevel converter.
9. A computer device comprising a processor and a memory;
the processor runs a program corresponding to the executable program code by reading the executable program code stored in the memory, so as to realize the control method of the wind grid diode direct current output system according to any one of claims 5 to 8.
10. A non-transitory computer readable storage medium having stored thereon a computer program, wherein the program when executed by a processor implements a method of controlling a wind grid diode dc-feed system as claimed in any one of claims 5 to 8.
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