CN111505365B - Modular multilevel converter station current signal acquisition system and method - Google Patents
Modular multilevel converter station current signal acquisition system and method Download PDFInfo
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- CN111505365B CN111505365B CN202010246034.4A CN202010246034A CN111505365B CN 111505365 B CN111505365 B CN 111505365B CN 202010246034 A CN202010246034 A CN 202010246034A CN 111505365 B CN111505365 B CN 111505365B
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Abstract
The invention provides a system and a method for acquiring current signals of a modular multilevel converter station, wherein the system comprises the following steps: the power supply module is a low-insulation voltage-resistant multi-port high-redundancy power supply and is interconnected with a direct current capacitor inside a three-phase MMC sub-module closest to the electricity; the current sensor is a kilovolt-level low-insulation voltage-resistant Hall type current sensor, is connected in series in a MMC converter station circuit, collects three-phase upper and lower bridge arm currents and/or direct current port total currents on site, and the analog quantity output of the current sensor is connected with a digital-to-analog conversion collector; and the digital-to-analog conversion collector receives the current signal collected by the current sensor, converts the current signal into a digital signal and transmits the digital signal to a controller of the MMC converter station through an optical fiber communication link. The invention can reduce the voltage-resistant requirement of the acquisition system, reduce the design difficulty of the system, realize the application of the Hall type current sensor in the flexible direct-current transmission project and improve the reliability of the system.
Description
Technical Field
The invention relates to the fields of flexible direct current transmission technology, power electronic technology and the like in a power system, in particular to a novel Modular Multilevel Converter (MMC) Converter station current signal acquisition system and method.
Background
The voltage source type high-voltage direct current transmission technology (VSC-HVDC) is particularly suitable for occasions of renewable energy source grid connection, passive network power supply, urban power grid power supply, asynchronous alternating current power grid interconnection and the like due to the flexibility of control. Therefore, research into VSC-HVDC has received extensive attention in recent years from both academic and engineering communities.
Traditional VSC-HVDC uses a two-level or three-level topology, using a direct series connection of a plurality of switching devices to meet the voltage class requirements. However, the method has high requirements on the consistency of the on and off of the switching devices, and has the problems of high voltage change rate, strong electromagnetic interference, dynamic voltage sharing of the switching devices and the like on connecting reactance of the converter station and the alternating current system. In 2002, german scholars proposed a new type of multilevel topology, namely Modular Multilevel Converters (MMC). The voltage class is improved by the cascade connection of the modules, and the direct series connection between the switching devices is avoided. Therefore, the MMC type converter station has a good application prospect in the development process of the VSC-HVDC technology.
In order to meet the control of the MMC converter station, information such as three-phase upper and lower bridge arm current, direct current output port current and the like needs to be acquired. Limited by the level of insulation withstand voltage, the commonly used hall type current sensor cannot be applied to the MMC converter station of the flexible power transmission system. Therefore, the existing MMC flexible power transmission system converter station mostly adopts a photoelectric current sensor to acquire information, but the price is high.
Disclosure of Invention
The invention aims to provide a novel MMC converter station current signal acquisition system and a novel method, which can reduce the withstand voltage requirement of an acquisition system, reduce the design difficulty of the system, realize the application of a Hall current sensor in flexible direct-current transmission engineering and improve the reliability of the system, aiming at solving the problems that a common Hall current sensor cannot be applied due to the problem of insulation and withstand voltage and a photoelectric current sensor is expensive in the conventional MMC flexible direct-current transmission engineering.
In order to achieve the above object, the present invention provides a system for acquiring a current signal of an MMC converter station, including: current sensor, power module, digital-to-analog conversion collector and fiber communication link, wherein:
the power supply module is a low-insulation voltage-resistant multi-port high-redundancy power supply, the insulation voltage resistance is in a kilovolt level of a single submodule and is interconnected with a direct current capacitor inside a three-phase MMC submodule closest to the electrical distance;
the current sensor is a Hall type current sensor with low insulation and voltage resistance, the insulation and voltage resistance is in a single sub-module kilovolt level, the Hall type current sensor is connected in series in a MMC converter station circuit, the current of an upper bridge arm and a lower bridge arm of three phases and/or the total current of a direct current port are collected on site, and the analog quantity output of the current sensor is connected with a digital-to-analog conversion collector;
and the digital-to-analog conversion collector receives the current signal collected by the current sensor, converts the current signal into a digital signal and transmits the digital signal to a controller of the MMC converter station through an optical fiber communication link.
Optionally, the insulation requirement of the input side to the output side of the power supply module is consistent with the capacitance voltage of the MMC submodule, namely, the kilovolt level.
Optionally, the power supply modules adopt a redundant design, and a plurality of output sides of the power supply modules are connected in parallel to supply power to the hall-type current sensor and the digital-to-analog conversion collector in the collection system, so that the power supply reliability of the system is improved.
Optionally, the low-insulation voltage-resistant hall type current sensor has insulation voltage resistance of a single sub-module (kilovolt) level, and because the hall type current sensor has low cost, redundancy can be provided for an acquisition system in a mode of connecting a plurality of sensors in series, and the reliability of the system is improved.
Optionally, the digital-to-analog conversion collector is a multi-channel digital-to-analog conversion collector, and can simultaneously convert multiple analog signals into digital signals, and transmit the converted digital signals to the controller of the MMC converter station through the optical fiber communication link in an optical signal communication manner. Because the current signals are collected on the spot, interference signals can be restrained in the digital-analog conversion collector, and the reliability of the collecting system is improved.
Optionally, the optical fiber communication link is established between the digital-to-analog conversion collector and a controller of the MMC converter station, and electrical isolation is achieved through an electrical-optical-electrical communication mode.
The invention also provides a current signal acquisition method of the MMC converter station, which is realized by adopting the current signal acquisition system of the MMC converter station.
Compared with the prior art, the embodiment of the invention has at least one of the following beneficial effects:
the MMC converter station current signal acquisition system disclosed by the invention realizes the application of the Hall current sensor in the field of flexible direct current transmission, and reduces the system cost.
According to the MMC converter station current signal acquisition system, the insulation requirement and the design difficulty of the system are reduced through a power supply mode of interconnection of the submodules closest to the electrical distance.
According to the MMC converter station current signal acquisition system, the reliability of the acquisition system can be improved in a mode of power supply redundancy, Hall current sensor redundancy and interference signal local inhibition.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
fig. 1 is a schematic wiring diagram of a current signal acquisition system of an MMC converter station according to an embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
Referring to fig. 1, a wiring method of a current signal acquisition system of a novel MMC converter station according to an embodiment of the present invention is disclosed, where the system includes a low-insulation voltage-withstanding hall-type current sensor (kv level), a low-insulation voltage-withstanding multi-port high-redundancy power supply, a digital-to-analog conversion collector, and an optical fiber communication link, and is connected to an MMC controller. The Hall type current sensors are connected in series on two sides of a direct current port of the MMC converter station and used for collecting information of three-phase upper and lower bridge arm currents and total current of the direct current port. The analog output of the Hall type current sensor is collected by a multi-channel analog-digital conversion collector, and is transmitted to a controller of the MMC convertor station through optical fibers of an optical fiber communication link after the conversion from an electric signal to an optical signal is carried out. The optical fiber needs to withstand converter station level voltage, namely, the insulation and voltage resistance level of a direct current power distribution network is dozens of kilovolts, and the insulation and voltage resistance level of a direct current power distribution network is hundreds or even thousands of kilovolts, and is a high-insulation and voltage-resistance optical fiber. The Hall type current sensor and the digital-to-analog conversion collector are powered by a high-redundancy power supply. And at the converter station side, the current data is restored after the optical signals are decoded and calculated, and the current information acquisition is completed.
The MMC converter station current signal acquisition system of the embodiment of the invention realizes the application of a Hall type current sensor with low insulation and voltage resistance (kilovolt level) in the field of flexible direct current transmission, replaces the traditional photoelectric type current sensor to acquire current information, and reduces the cost of the system. And because the Hall type current sensor has lower cost, the method for collecting the current by connecting a plurality of Hall type current sensors in series can avoid the failure of current information collection caused by the damage of a single Hall type current sensor and improve the reliability of a collection system.
In some preferred embodiments, a low dielectric strength (kilovolt level) multi-port high redundancy power supply is interconnected with the internal dc capacitors of the three-phase MMC submodule that is electrically closest. Due to the adoption of the power supply mode with the closest electrical distance, the insulation and voltage resistance requirements of the power supply are greatly reduced, and the design difficulty of a power supply system is reduced. The insulation requirement of the input side of the transformer on the output side is consistent with the voltage of the capacitor of the submodule, namely the kilovolt level. Furthermore, the power supply adopts a redundancy design, for example, three power supply modules can be adopted, the output sides of the three power supply modules are connected in parallel to supply power for the Hall type current sensor and the digital-to-analog conversion collector in the collection system, and the power supply reliability of the system is improved.
In the MMC converter station current signal acquisition system of the embodiment of the invention, the three MMC sub-modules with the nearest electrical distance of the Hall type current sensor supply power to the input side of the power supply, and the output side of the power supply is connected in parallel to supply power to the Hall type current sensor and the digital-to-analog conversion collector. The wiring method with the closest electrical distance reduces the insulation requirement of the input side to the output side of the power supply, the Hall type current sensor and the digital-to-analog conversion collector to the voltage level of a single sub-module capacitor. Compared with the voltage level of hundreds of kilovolts or even more than one thousand kilovolts of direct current of the converter station, the capacitor voltage of a single submodule is only in the kilovolt level. The reduction of insulation requirements reduces the design difficulty of the system, the redundant design ensures the power supply reliability of the system after a certain submodule fails.
In some preferred embodiments, the digital-to-analog converter is a multi-channel digital-to-analog converter (multi-channel a/D converter), which can simultaneously convert multiple analog signals into digital signals, and transmit the converted digital signals to the controller of the MMC converter station via an optical fiber communication link (a converter station voltage level high-insulation and voltage-resistance optical fiber) in an optical signal communication manner. Because the current signals are collected on the spot, interference signals can be restrained in the digital-analog conversion collector, and the reliability of the collecting system is improved.
In some preferred embodiments, the optical fiber communication link is established between the digital-to-analog conversion collector and the controller of the MMC converter station, and electrical isolation is achieved through an electrical-optical-electrical communication mode.
According to the MMC converter station current signal acquisition system provided by the embodiment of the invention, the mode of acquiring current information in situ and transmitting information through optical fiber communication is adopted, so that interference signals can be inhibited in situ in the digital-to-analog converter, and the reliability of the acquisition system is improved.
According to the embodiment, the existing flexible direct current power transmission system adopts an MMC topological structure due to the limitation of power devices, high power transmission voltage grade and the like. In order to meet the control of the MMC converter station, signals such as a direct current output total current of a system, upper and lower bridge arm currents of each phase and the like need to be acquired, and a photoelectric sensor with high insulation and voltage resistance and high cost is often adopted in the existing power transmission application field. The common Hall type current sensor cannot be applied to the field of power transmission due to the problem of insulation and voltage resistance. In order to realize the application of the low-cost Hall type current sensor in the field of power transmission, the embodiment of the invention adopts the digital-to-analog conversion collector to convert the electric analog signal of the Hall type current sensor into the digital signal, and transmits the collected current signal to the controller in a communication mode through the high-insulation and pressure-resistant optical fiber at the voltage level of the converter station. Meanwhile, because the Hall type current sensor and the digital-to-analog conversion collector need a power supply, the embodiment of the invention adopts a multi-port power supply module to be connected with a plurality of sub-modules with close electrical distances in the MMC converter station, and because the MMC sub-modules with close electrical distances are selected, the power supply can adopt a low-insulation voltage-resistant (kilovolt level) design, thereby greatly reducing the design difficulty of the power supply, and adopts a plurality of ports to be connected with a plurality of MMC sub-modules, thereby ensuring that the power supply can still continuously operate after a certain sub-module fails, and improving the reliability. Due to the low cost of the Hall type sensor with low insulation and voltage resistance (kilovolt level) and the power supply, the low-cost redundancy design of the acquisition system can be realized, the acquisition system can be conveniently adopted to carry out local inhibition on interference signals, and the reliability of the system is improved.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes and modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention.
Claims (7)
1. A modular multilevel converter station current signal acquisition system, comprising: current sensor, power module, digital-to-analog conversion collector and fiber communication link, wherein:
the power supply module is a low-insulation voltage-resistant multi-port high-redundancy power supply, the insulation voltage resistance is in a kilovolt level of a single submodule and is interconnected with a direct current capacitor inside a three-phase MMC submodule closest to the electrical distance;
the current sensor is a Hall type current sensor with low insulation and voltage resistance, the insulation and voltage resistance is in a single sub-module kilovolt level, the Hall type current sensor is connected in series in a MMC converter station circuit, the current of an upper bridge arm and a lower bridge arm of three phases and/or the total current of a direct current port are collected on site, and the analog quantity output of the current sensor is connected with a digital-to-analog conversion collector;
the digital-to-analog conversion collector receives the current signal collected by the current sensor, converts the current signal into a digital signal and transmits the digital signal to a controller of the MMC converter station through an optical fiber communication link;
the insulation requirement of the input side of the power supply module to the output side is consistent with the capacitance voltage of the MMC sub-module, namely the kilovolt level;
the power supply module adopts a redundant design, and a plurality of power supply module output sides are connected in parallel to supply power for the current sensor and the digital-to-analog conversion collector.
2. The modular multilevel converter station current signal acquisition system of claim 1, wherein the current sensors provide redundancy for the acquisition system by using a series connection of a plurality of low-insulation and voltage-resistance hall-type current sensors.
3. The system of claim 1, wherein the dac collector is a multi-channel dac collector, and is configured to simultaneously convert multiple analog signals into digital signals and transmit the converted digital signals to the MMC converter station controller via the optical fiber communication link in an optical signal communication manner.
4. The modular multilevel converter station current signal collection system of claim 1, wherein the fiber communication link is established between the digital-to-analog converter collector and the controller of the MMC converter station, and electrical isolation is achieved through an electrical-optical-electrical communication manner.
5. The modular multilevel converter station current signal collection system according to any of claims 1 to 4, wherein the collection system adopts a mode of current information collection in situ and information transmission through optical fiber communication.
6. The modular multilevel converter station current signal acquisition system according to any of claims 1 to 4, wherein the optical fiber communication link, wherein the optical fiber can withstand converter station level voltage, that is, several tens kilovolt level insulation voltage rating of direct current distribution network, and hundreds or even thousands kilovolt level insulation voltage rating of direct current distribution network.
7. A modular multilevel converter station current signal acquisition method, characterized in that the method is implemented by using the modular multilevel converter station current signal acquisition system of any of claims 1-6.
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Effective date of registration: 20230524 Address after: 226600 No. 189, Xiaoxing Avenue, Chengdong Town, Hai'an City, Nantong City, Jiangsu Province Patentee after: JIANGSU BEICHEN HUBANG POWER Co.,Ltd. Address before: 200240 No. 800, Dongchuan Road, Shanghai, Minhang District Patentee before: SHANGHAI JIAO TONG University |
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