101 results about "Thyristor converters" patented technology

The invention discloses a mixed bipolar DC transmission system. The system comprises a rectification converter station and an inversion converter station which are connected through a DC transmission line, wherein the rectification converter station is formed by two thyristor converters through serial connection, and the serial connection node is grounded; and the inversion converter station is formed by two modular multilevel converters (MMCs) through serial connection, the serial connection node is grounded, and positive and negative ends after serial connection are connected with one-way connection power devices. The system has the advantages of low cost and loss, high reliability and the like of the existing thyristor converter, flexible control of the MMCs, low harmonic, active-reactive power decoupling control, low dependence on an alternating current system and the like; and the system is divided into positive and negative poles, so that operating reliability is strengthened, and the power devices provided with the one-way connection capacity and additionally arranged at outlets of inverters can effectively handle DC faults. The system is suitable for occasions such as high-power long-distance high-voltage DC transmission and island current delivery, provided with broad development space, and worthy of being popularized vigorously.

The invention discloses a series hybrid bipolar direct-current transmission system with direct-current fault ride-through capability. The series hybrid bipolar direct-current transmission system comprises a rectifier station and an inverter station, wherein the rectifier station is connected with the inverter station through a direct-current transmission line; positive electrodes and negative electrodes of the rectifier station and the inverter station are formed by connecting thyristor converters and modular converters in series; and each modular converter is formed by connecting one or more modular multilevel converters in parallel. The series hybrid bipolar direct-current transmission system has the advantages of low construction cost, low loss, high reliability and the like of the traditional thyristor converters, and has the advantages of flexible control, low harmonic wave, active and reactive power decoupling control, voltage support capacity on an alternating-current system access point and the like of the modular multilevel converters; the system is divided into the positive electrode and the negative electrode; the operation reliability is enhanced; and a direct-current fault can be removed by the actions of the converters under various faults. Therefore, the series hybrid bipolar direct-current transmission system is suitable for high-voltage direct-current transmission occasions of a remote high-capacity overhead line, has a wide development space and is worthy of strong popularization.

The invention provides electronic equipment with high voltage and high power, which is used for converting alternating current (AC) voltage into direct current (DC) voltage or converting DC voltage into AC voltage, in particular a thyristor converter valve module. A whole valve module is divided into two same segments, and each segment comprises a saturable reactor, a thyristor, a DC equalizing resistor unit, an energy-extracting resistor unit, a damping resistor unit, a damping capacitor unit, a gate electrode unit and a water cooling system, wherein the reactors of the electronic equipment are connected in series to meet the requirements on different transmission powers and different power voltage grades. The equipment is core equipment for high-voltage DC power transmission and can be applied to a DC-AC converting system, meet the requirements of different voltage grades and for the DC converting system with different voltage grades, including the super high voltage of 800 kV or above.

The invention provides a novel valve tower of a thyristor converter valve. The novel valve tower comprises a valve hall, a valve tower body, a valve support (6) and a lightning arrester (9). The valve tower body and the lightning arrester (9) are hung on the lower edge of a steel beam on the top of the valve hall through a suspended insulator chain. The valve tower body is composed of a top shielding case (4), a bottom shielding case (1) and valve layers between the top shielding case (4) and the bottom shielding case (1). The valve tower body is composed of a left half tower body and a right half tower body. Each valve layer is composed of two converter valve modules (2). The valve layers and the bottom shielding case (1) are suspended below the top shielding case (4) through interlayer insulators (3) arranged between the adjacent valve layers and arranged between the valve layers and the bottom shielding case (1). By the adoption of the structure, the valve tower body and the steel beam on the top of the valve hall can swing relatively, the valve layers can also swing relatively, and therefore the valve tower is high in overall flexibly and good in anti-seismic effect.

The invention discloses a hybrid DC (direct current) electric power transmission system comprising a passive filter, a rectifier converter transformer, a thyristor converter, a flat wave reactor, a DC electric power line, a multi-level converter and an inverse converter transformer. A twelve-pulse bridge converter based on a thyristor is arranged at a sending-end rectifier side, and a modularized multi-level converter is arranged at a receiving-end inverter side, thus eliminating the phase conversion failure of the traditional DC electric power transmission system fundamentally and being suitable for supplying power for multi-DC droppoint areas, passive networks or weak alternating current systems and other occasions. Compared with a light-type high-voltage DC electric transmission system, the hybrid DC electric power transmission system provided by the invention has the advantages that the number of expensive full-control devices is greatly decreased, the cost is reduced, the loss is reduced, the reliability is high, the control is flexible, and fewer reactive compensation devices are used. In addition, the hybrid DC electric power transmission system provided by the invention can be used as a black start power supply of a receiving-end alternating current system and is good in engineering application value.

The invention discloses a hybrid direct-current transmission topology structure and a control method. The hybrid direct-current transmission topology structure is characterized in that two groups of thyristor converters are connected in series to form a first converter station, two groups of voltage source type converters are connected in series to form a second converter station, switch elements are respectively mounted at the same positions of the positive ends and the negative ends of the converters, in series connection, of the first converter station or the second converter station or the first converter station and the second converter station, and meanwhile, the same positions of the positive ends and the negative ends of the converters are in parallel connection and crossly connected to the opposite ends through one switch element respectively. The control method includes reducing direct-current power of a direct-current system to zero, and changing states of the switch elements to invert voltage polarity of the direct-current system, thereby achieving overall operation of two poles after inversion of the direct-current voltage polarity or achieving new two-pole direct-current operation by means of crossing of the converters in series connection of the converter stations at both ends. The system of the hybrid direct-current transmission topology structure has advantages of low manufacturing cost as the conventional direct-current transmission and control flexibility as the flexible direct-current transmission, and the like.

The invention discloses a hybrid direct-current transmission system. A first group of thyristor converter units and a second group of thyristor converter units are connected with the same sending end alternating-current power grid through a converter respectively, or connected with different sending end alternating-current power grids. An inversion converter station is composed of at least one group of voltage source converters, direct-current lines at the positive and negative ends of each voltage source converter are respectively equipped with a first switching element and a fourth switching element, and the direct-current lines at the positive and negative ends are wired in parallel and in a cross manner to the opposite-end direct-current lines through the first switching element and the fourth switching element respectively. Converter stations at the two ends are connected by two direct-current lines. The invention further discloses a hybrid direct-current transmission system control method and a hybrid direct-current transmission system power reversal control method. The hybrid direct-current transmission system of the invention has the advantages of low cost of traditional direct current, flexible control on flexible direct current, and the like.

The invention discloses a thyristor converter valve tower for high voltage direct current transmission. The tower comprises insulating support frames, wherein at least two valve modules and at least two reactor modules are arranged in a parallel manner on the insulating support frames at intervals along vertical direction. The thyristor converter valve tower further comprises a water cooling system used for cooling the valve modules and the reactor modules. The water cooling system comprises a cooling-water main pipe and a cooling-water branch pipe, wherein the cooling-water main pipe is arranged in a winding manner at the outside of the corresponding valve module from top to bottom, the cooling-water branch pipe used for guiding the cooling water to the valve modules and the reactor modules is arranged on the cooling-water main pipe in the direction towards the circular inner side, and gaps are formed between the cooling-water main pipe and the corresponding valve module and reactor module. The tower solves the problem that when a pipe of the water cooling system has water leakage, the thyristor converter valve towel of the prior art brings short circuit damage to bottom components, and reduces the service life of the thyristor converter valve tower.

A three-phase power supply with a three-phase three-level DC / DC converter includes a full-bridge thyristor converter with three-set four in-series power switch elements, a three-phase isolated transformer, a full-bridge rectifier, a rectifying circuit, and a low-pass filtering circuit. The three-phase power supply is used to deliver power energy from the AC input voltage to the load. The power switch elements, which separated to each other at 120-degree phase differences, are controlled through a phase shift scheme. Therefore, the three-level circuit structure is provided to reduce withstanding voltage of the power switch elements, further the zero-voltage switching (ZVS) is achieved by the isolated transformer and the power switch elements to increase the efficiency of the DC / DC converter.

The present invention relates to a high-power electrical electronic rectification and inversion apparatus, and specifically relates to a valve tower for thyristor converter valves, applicable in the fields of high-power high-voltage power transmission engineering and high-power direct-current ice melting. The valve tower comprises two or more valve layers which are laminated from top to bottom. Each valve layer includes at least two converter valve assemblies arranged side by side, and adjacent two converter valve assemblies in the same valve layer are arranged with an interval therebetween and fixedly connected together. A maintenance area is formed in the interval between adjacent two converter valve assemblies in the same valve layer, and a maintenance channel for maintenance personnel to get in and out is formed by the maintenance areas in different valve layers in up-down correspondence. According to the invention, the valve tower has the maintenance channel which provides a space for the operation of the maintenance personnel, such that the operation of the maintenance personnel is convenient, and the problem of the inconvenience in the maintenance caused by the small maintenance space of the conventional valve tower for the converter valves is solved.

The invention discloses an off-line control method for a mixed direct current transmission system. The method includes (1) reducing direct current to the set value; (2) gradually adjusting a tap of a converter transformer to the largest transformation ratio position; (3) adjusting reactive power between an inversion converter station and a receiving end alternating current power grid to zero and reducing direct current voltage; (4) gradually reducing the direct current from the set value to zero and further increasing the triggering angle of a thyristor converter to 120 degrees; (5) locking the thyristor converter and an MMC and sequentially disconnecting a direct current isolation switch, an alternating current circuit breaker and a three-phase bypass switch; (6) quickly releasing capacitor voltage of sub modules in the MMC to Ucs and then automatically releasing the voltage to zero. The method can ensure the stable fast off-line process, and avoids overvoltage or overcurrent. In addition, in the MMC capacitor discharging link, the extra circuit breaker and discharging resistance are removed in a starting current limit resistance reutilization mode, and the investment cost is saved.

A three-phase power supply with a three-phase three-level DC / DC converter includes a full-bridge thyristor converter with three-set four in-series power switch elements, a three-phase isolated transformer, a full-bridge rectifier, a rectifying circuit, and a low-pass filtering circuit. The three-phase power supply is used to deliver power energy from the AC input voltage to the load. The power switch elements, which separated to each other at 120-degree phase differences, are controlled through a phase shift scheme. Therefore, the three-level circuit structure is provided to reduce withstanding voltage of the power switch elements, further the zero-voltage switching (ZVS) is achieved by the isolated transformer and the power switch elements to increase the efficiency of the DC / DC converter.

The invention relates to a system for measuring the temperature in a thyristor in real time. The system comprises a fiber grating temperature sensor, wherein the fiber grating temperature sensor adopts a fiber made of quartz glass; gratings are etched on the fiber; each grating serves as a measuring point of the measuring system, and the temperature distribution of a thyristor molybdenum sheet layer is realized by using a plurality of gratings; a molybdenum sheet of the thyristor is provided with an open groove for accommodating the fiber; a porcelain ring of the thyristor is provided with an opening; the fiber passes through the opening, and is then connected with a demodulator through a multi-mode fiber; the demodulator is used for demodulating the reflection wavelength of reflected light transmitted by the fiber grating temperature sensor into a temperature signal to obtain real-time information of the temperature in a thyristor copper shell; and the demodulator is used for transmitting demodulated data to a background computer through a cable. The measuring system has the advantages of high stability, high reliability, high stability, high linearity, small errors and the like, the measuring range is between 40 DEG C below zero and 310 DEG C, the maximum error is 1.68 percent, and the testing requirements of various thyristor converter valves can be met.

The invention discloses an online switch-off device and method for a hybrid direct-current transmission system converter. The method comprises the following content that a converter online switch-offcommand is initiated by a master control station, a thyristor converter of a rectifier converter station is controlled to increase a trigger angle, a thyristor bypass pair is switched off, a direct-current side parallel bypass switch is switched on, the thyristor converter is locked, and a bypass knife switch assembly is controlled to isolate the converter; and an inverter converter station is controlled to switch on a direct-current side parallel bypass circuit, a voltage source converter is locked, and the bypass knife switch assembly is controlled to isolate the converter. The difficult problem in online switch-off of the hybrid converter can be effectively solved; online safe switch-off of the VSC is realized; and the safety of the direct-current transmission system can be better protected.

The invention provides a thyristor converter valve tower for high-voltage direct-current power transmission, comprising a lightning arrester and a valve tower body which are vertically arranged and are parallel to each other. The valve tower body comprises a top shield and a bottom shield which are arranged horizontally and thyristor converter valve modules which are arranged in parallel and in the same direction between the top shield and the bottom shield. The thyristor converter valve modules are concave. The lightning arrester is arranged at the outer side of the openings of the concave thyristor converter valve modules, and is connected with the thyristor converter valve modules through flexible tubular buses. The thyristor converter valve tower provided by the invention has the advantages of high flexibility, good anti-seismic effect, lower weight, more stable structure, convenient maintenance, and easy transportation, installation and commissioning on an engineering site.

The invention discloses a fault handling device for a hybrid DC transmission system with a fault restart function, which comprises an acquisition unit, a fault identification unit and a fault handlingunit. The invention also discloses a fault handling method. The DC voltage and the DC of the hybrid DC transmission system and the AC voltage and the AC of an AC power grid connected with a rectifierconverter station and an inverter converter station are acquired; whether the hybrid DC transmission system fails is identified according to the acquired analog; and if fault happens, a thyristor converter is controlled to switch a trigger angle instruction value, and a current source-type converter based on a fully-controlled power electronic device is controlled to switch a DC instruction valueand / or a DC voltage instruction value. the above technical scheme can effectively handle the DC transmission line fault of the hybrid DC transmission system, reliable fault ride through can be realized, fast DC power recovery after the fault disappears can be realized, the stability of the AC / DC transmission system can be better maintained, and the safety of the AC / DC transmission system is protected.

The invention provides a thyristor converter valve reliability evaluation method of considering an operating state. A temperature field model of a thyristor is built on the basis of the fourier heat transfer law; and a formula for the temperature and the fault rate of the thyristor is provided, so that a thyristor reliability model on the basis of the operating state is built. A converter valve reliability evaluation method of considering the operating state is provided by a state partition principle. According to the method, the operating state of the system is considered in the converter valve reliability evaluation; the defect that the actual operating state cannot be considered in the existing converter valve reliability evaluation is overcome; the thyristor-based converter valve reliability evaluation accuracy can be effectively improved; and a relatively reliable basis is provided for planning and operating of a high-voltage direct-current power transmission system.

The invention relates to a high-power electrical electronic rectification and inversion apparatus, and specifically relates to a thyristor converter valve assembly applicable in high-voltage direct-current power transmission, direct-current ice melting equipment, SVC, etc. The thyristor converter valve assembly comprises valve modules and corresponding reactors. The valve module includes a frame. The valve modules and the reactors are fixedly mounted on a rectangular frame-type base in a detachable manner and distributed along the left-right direction of the base. The base includes a front border, a rear border, a left border, a right border and supporting beams bridging the front border and the rear border. The lengths of the left and right borders are smaller than that of the front and rear borders. The left and right borders are made of aluminium section material. One of the front and rear borders is made of aluminium section material, while the other one is made of insulation material. The thyristor converter valve assembly has the advantages of convenience for both transport and on-site assembly.

The invention relates to a full-current composite high-voltage direct current transmission system. The full-current composite high-voltage direct current transmission system includes a rectification station, an inversion station and an overhead power transmission line; the rectification station adopts thyristor converters; the positive pole and negative pole of the rectification station both comprise a twelve-pulse thyristor converter; the inversion station adopts fully-controlled power electronic device-based current source-type converters; the positive pole and negative pole of the inversion station both include two series-connection current source-type converters; positive and negative pole connection points of the rectification station and the inversion station are connected with a grounding pole or an intra-station grounding grid according to situations in which the direct current transmission system is in bipolar, mono-polar ground return or mono-polar metal return operation modes; and the rectification station is connected with the inversion station through the overhead power transmission line. The full-current composite high-voltage direct current transmission system of the invention is advantageous in flexible operation mode and high reliability. The full-current composite high-voltage direct current transmission system of the invention is especially suitable for long-distance high-voltage direct current overhead transmission, and is also particularly applicable to the upgrading and reconstruction of the existing full-thyristor type high-voltage direct current transmission. The full-current composite high-voltage direct current transmission system is further advantageous in convenience and practicability.

Charging time of a capacitor is shortened while avoiding erroneous firing due to distortion of a power supply voltage and sustaining an inrush current at a constant level. In the charge control method of a capacitor in a thyristor converter comprising a thyristor for rectifying an AC voltage, a CPU delivering an on / off control signal to a thyristor driver for driving the thyristor, a voltage detection sensor for measuring the AC voltage and the capacitor charging voltage, and the capacitor connected with a DC circuit, the AC voltage and the capacitor charging voltage are measured by means of the voltage detection sensor, differential voltage between the firing phase voltage of the thyristor and the capacitor charging voltage is determined, and the thyristor is fired only when the firing phase voltage of the thyristor becomes lower than a specified voltage determined from the differential voltage.

The invention discloses an economical single-ended cascade hybrid DC transmission system with tidal current bidirectional flow. The system comprises a rectifier station and an inverter station. The DCsides of the rectifier station and the inverter station are connected by a DC transmission line. The rectifier station and the inverter station comprises interconnected thyristor converter LCC and modular converter and also comprises a transmitting end AC grid and a receiving end AC grid, and the thyristor converter LCC and the modular converter are respectively connected to the transmitting endAC grid and the receiving end AC grid through a double-winding transformer. The present invention proposes a new LCC-MCSM(monopole current sub-module)-HVDC type hybrid converter valve, and the bidirectional flowing of DC power flow can be achieved by using the voltage polarity reversal of a DC port.

The invention discloses a withdrawal device and method for a series converter of a hybrid direct-current power transmission system. The method herein includes: controlling a thyristor converter, to bewithdrawn, of a rectifier converter station to close a direct-current side parallel bypass switch, locking the thyristor converter to be withdrawn, opening a direct-current side isolator and openingan alternating-current side incoming wire switch; controlling a voltage source converter, to be withdrawn, of an inverse converter station to make a direct-current side parallel bypass circuit, locking the voltage source converter to be withdrawn, opening the direct-current side isolator, and opening an alternating current side incoming wire switch; resuming operation power of the hybrid direct-current power transmission system. The withdrawal device and method herein have the advantages that the online withdrawal difficulty of a hybrid converter can be effectively overcome, online withdrawalof a series VSC (voltage source converter) is achieved, alternating and direct current shock upon withdrawal is reduced, and safety of an alternating and direct current power transmission system is better protected.

The invention relates to a thyristor converter valve module for HVDC (High Voltage Direct Current) transmission, which is characterized by comprising two valve sections (1 and 2), wherein each valve section is an integrity in structure and comprises a saturated reactor (3), a thyristor unit (4), a DC isobarometric resistor unit, an energy-taking resistor unit, a damping resistor unit (5), a gate unit (6) and a water-cooling system; and in a thyristor-level assembly, the gate unit (6) is arranged at one side of the thyristor unit (4), and the damping resistor unit (5) and a damping capacitor unit (7) are arranged at the other side of the thyristor unit (4). The valve module is watertight, has the advantages of small geometrical size, light weight, convenient assembly and maintenance, simple technical operation and low requirements on operation skills and can effectively improve the mounting efficiency.

The invention discloses a current source for a function test of a DC high-voltage transmission thyristor converter valve component. The current source mainly comprises a three-phase three-winding rectifier transformer T1 and a six-pulse rectifier bridge, wherein the three-phase three-winding rectifier transformer T1 transforms the high voltage and low current of a power supply system to the low voltage and large current on a valve side; the six-pulse rectifier bridge transforms the AC to large DC and provides the test current for a converter valve component sample through a DC bus; the six-pulse rectifier bridge is only one set, and the DC output current of the six-pulse rectifier bridge can reach 7,000 A. The current source can test more samples at lower voltage on the valve side of the transformer and can greatly reduce the secondary side voltage of a converter transformer under the condition that the test requirements are met so as to greatly reduce the capacity of the rectifier transformer in the current source loop.

The invention belongs to the field of high-power converting technology control, and specifically relates to a thyristor synchronization signal processing method applicable to changing frequency. The method comprises the following steps: filtering out the high-frequency component of an original synchronization signal through a first-order RC low-pass filter; converting the filtered synchronization signal into a square wave signal and inputting the square wave signal into a digital signal processor (DSP), and using a capture unit of the DSP to judge the frequency of the square wave signal; calculating the phase shift produced at the frequency based on the phase frequency characteristics of the filter; and predicting the zero-crossing point of a next-cycle synchronization signal based on the zero-crossing point of the square wave signal and the phase shift produced after filtering, and outputting a square wave signal of the same phase as the original synchronization signal to perform subsequent trigger pulse processing. The method has the advantages of accuracy, quickness, strong frequency tracking ability, and capability of improving the trigger precision of thyristor converters.

The bidirectional power controller used in the superconducting energy storage is composed of power inverter, low frequency transformer and thyristor converter. The dc side of the power inverter connects with dc side of the power transformation installation used in the electric control of the superconducting energy storage system and its ac side connects with the original boarder of the low frequency transformer. The sub boarder of the low frequency transformer connects with the ac side of the thyristor converter and the dc side of the thyristor converter connects with the superconducting energy storage inductance. Adopting the bidirectional power controller of the invention can realize the control to the superconducting energy storage system with large power and reaches the ideal direct voltage stability, without adding extra voltage stabilizer. It is featured by simple circuit structure and high efficiency.

The invention relates to a thyristor converter valve large component silicon stack structure comprising an outer frame and multiple heat radiators and thyristors which are installed in parallel insidethe outer frame. The outer frame comprises a pair of insulating pull plates which are vertically arranged and a pressing side installing block and a disc spring side installing block which are arranged on the two ends between the two insulating pull plates. Two parallel limiting bolts are arranged side by side on the outer side of the pressing side installing block, and a pressing side bus bar isarranged on the inner side. A disc spring assembly is arranged on the inner side of the disc spring side installing block. A disc spring side bus bar is arranged on the inner side of the disc springassembly. The thyristors are connected in series between two adjacent heat radiators and coaxial with the heat radiators. The same ends of the two adjacent heat radiators are connected in series by awater pipe, and the other end of each heat radiator is respectively connected in parallel with the water inlet pipe and the water outlet pipe. Double helical heat radiation channels are arranged inside the heat radiators. The thyristor converter valve large component silicon stack structure has a simple and compact structure and can avoid bending deformation of the silicon stack under the action of high temperature circulation and has the effect of heat radiation of series and parallel waterways.

The invention discloses a hybrid direct current transmission system and a serial converter input device and method thereof. The method comprises the steps of: controlling a thyristor converter required being input of a rectification convertor station to close a DC side isolating disconnecting link and an AC side incoming line switch to unlock the thyristor converter required being input and disconnect a DC side parallel bypass switch; controlling a voltage source type converter required being input of a inversion convertor station to close the DC side isolating disconnecting link and disconnect the AC side incoming line switch to access a charge resistor and connect an AC side bypass switch to perform pre-charge of the voltage source type converter required being input through the charge resistor, and connecting the AC side bypass switch after the pre-charge is completed; selecting a constant DC voltage control mode for unlocking to disconnect a DC side parallel bypass circuit; and finally, recovering the operation power of the hybrid direct current transmission system. The problems of online input of the hybrid converter are effectively solved to achieve online input of a serial VSC converter, reduce the AC-DC current impact when input and better protect the safety of the AC-DC transmission system.

The present invention relates to a multi-pulse HVDC system which is capable of minimizing the number of thyristors by providing a thyristor auxiliary circuit in a conventional 12-pulse thyristor HVDC(High Voltage Direct Current), not using an additional stack of a thyristor and which is implemented based on an auxiliary circuit having a multi-pulse thyristor HVDC system like 24-pulse / 36-pulse / 48-pulse converters. The multi-pulse HVDC system is characterized in that an upper side thyristor converter 12 and a lower side thyristor converter 13 are installed in a Δ-Δ-Y transformer 11, and two current smoothing reactor 39 and a direct voltage dividing condenser 38 are installed between the upper side thyristor converter 12 and the lower side thyristor converter 13, and two thyristors 32, 33: T2 and T1 are connected to one double winding transformer 31.

The invention discloses a method for configuring structure transformation of double 6-pulse thyristor converter valve groups. The double 6-pulse thyristor converter valve groups include two 6-pulse converter valve groups, fourteen isolating switch groups, four isolating switches and two phase-control electric reactor groups. On and off of the various isolating switches are controlled, so that the double 6-pulse thyristor converter valve groups can be transformed into direct-current ice melting devices to melt ice for circuits when conducting wires are coated by the ice in winters, the electric reactors of the direct-current ice melting devices are used as load for zero-power tests before the ice on the circuits actually begins to be melted, currents can be increased without the circuits, and the double 6-pulse thyristor converter valve groups are used as static var compensators so as to perform dynamic reactive compensation on an alternating-current system in other times. The method for configuring the structure transformation has the advantage that normal ice melting running modes, zero-power test running modes and SVC (static var compensator) running modes of the double 6-pulse thyristor converter valve groups can be quickly and automatically switched over by the aid of the method.