WO2015184955A1

WO2015184955A1 - Voltage source type dc ice melting and static synchronous compensation device and method for controlling same

Info

Publication number: WO2015184955A1
Application number: PCT/CN2015/079557
Authority: WO
Inventors: 傅闯; 饶宏
Original assignee: 南方电网科学研究院有限责任公司
Priority date: 2014-06-03
Filing date: 2015-05-22
Publication date: 2015-12-10
Also published as: CN104078909B; CN104078909A

Abstract

A voltage source-type DC ice melting and static synchronous compensation device and method for controlling same. The device includes at least a basic converter unit which comprises a link reactor Ls, a modular multi-level converter MMC using a full-bridge submodule , switches K1, K2, K3, K4, and smoothing wave reactors Ld1, Ld2. Methods for transition between different function modes of the device can meet the requirements for safe and rapid deicing of transmission lines at various voltage levels; no harmonic pollution at an access point is caused, and dynamic reactive power compensation can be provided for the access point. The device can be used for a newly-constructed DC deicing project, and can also be used for upgrade and reconstruction of the DC deicing device in a DC deicing project having been constructed.

Description

Voltage source type DC ice melting and static synchronous compensation device and control method thereof

Technical field

The invention relates to a voltage source type DC ice melting and static synchronous compensation device and a control method thereof, in particular to a DC ice melting and static synchronous compensation device of a modular multilevel converter based on a full bridge submodule and The control method relates to the field of high-power power electronics and transmission line melting ice technology.

Background technique

Among the various natural disasters that the power system suffers, ice storms are one of the most serious threats. With the continuous improvement of the level of modernization, the whole society is increasingly dependent on electricity, and higher requirements are placed on the power supply. In recent years, all kinds of meteorological disasters in the world have become more frequent, and extreme weather and climate events have become more abnormal. The loss and impact of power system caused by ice disasters have become more serious, the damage has become more and more serious, the impact has become more and more complex, and the difficulty of response has also been getting bigger. Such as the Swedish ice disaster in October 1921, the Columbia earthquake in January 1972, the ice disaster in the northeastern United States and southeastern Canada in January 1998, the French ice disaster in December 1999, the January 2005 ice disaster in southern Sweden, Germany's ice disaster in November 2005.

China's ice disasters occur frequently, and the impact on the power grid is becoming more and more serious. At the beginning of 2005, the rare low-temperature rain, snow and ice weather in the history of Central China caused serious disasters to China's Central China and North China power grids. At the beginning of 2008, low-temperature rain and snow and freezing weather hit southern China, Central China, and East China, causing large-scale and long-term power outages in Guizhou, Hunan, Guangdong, Yunnan, Guangxi, and Jiangxi provinces, causing huge losses to the national economy and people's lives. . In January 2011, due to the large area of ice coating, the power grids in Guizhou Province, Hunan Province, Jiangxi Province, Guangxi North Guangxi Region, Guangdong Yuebei Region and Yunnan Northeast Yunnan Province were greatly affected. At the beginning of 2012, early 2013, and 2014, China's power grids were affected by ice coating to varying degrees.

After the 2008 ice disaster, Chinese electric power science and technology workers independently developed the DC ice melting technology and equipment, and successfully developed a high-power DC ice melting device with completely independent intellectual property rights, mainly including a DC melting device with a dedicated rectifier transformer ( ZL201010140060.5) and DC ice-melting device without special rectifier transformer (ZL201010140086.X), and then promoted and applied in the country. So far, about 100 sets of DC ice-melting devices have been put into operation, including layout in the southern power grid. There are more than 80 sets. The above two kinds of DC ice melting devices adopt the thyristor controllable rectification technology, which consumes certain reactive power and generates characteristic subharmonics during operation, which has certain influence on the access communication system. In particular, the DC ice-melting device without a dedicated rectifier transformer can only use 6-pulse rectification, and the harmonic pollution during operation is serious. In practical applications, other loads of its access point need to be transferred to other busbars.

Since 2008, there have been related research launches based on DC ice melting devices that can turn off power electronics. However, because the power electronics can be turned off, the voltage and current capacity are still limited, and the high-power voltage source converter is less reliable. Some DC-based ice-melting devices based on voltage source converters are proposed by the industry. The melting ice that can be used for transmission lines of 110kV and below can not provide the minimum melting current required for melting ice of higher voltage transmission lines. Up to now, at home and abroad, there has not been a successful development of a voltage source type DC ice melting device that can replace the thyristor-based, economical and practical application for melting ice of different length and multi-voltage transmission lines.

In recent years, voltage source converters have made great progress. The static synchronous compensator (STATCOM) based on H-bridge has been widely used. The Southern Power Grid is in 500kV Dongguan Substation, Water Town Substation, Beijiao Substation and Kapok. Each substation is equipped with a STATCOM with a capacity of ±200MVAr. Based on the half-H bridge modular multi-level converter (MMC) has also been applied in the field of flexible DC transmission, and shows obvious technical advantages, the world's first VSC-HVDC project using the MMC technology Trans Bay Cable March 2010 In the United States officially put into operation, the world's first multi-terminal flexible DC transmission project - South Australia ± 160 kV multi-terminal flexible DC transmission demonstration project was put into operation in December 2013 in Shantou, China. The reliability of modular multilevel converters is gradually increasing and prices are gradually decreasing. The modular multi-level converter based on the full bridge sub-module has the bidirectional operation capability of DC voltage and DC current, which can meet the requirements of DC ice melting on the operating conditions of the converter, and is applied to DC melting ice to overcome the present There are disadvantages based on thyristor DC ice melting devices.

At this stage, the flow-through capability of fully-controlled devices is still very limited, far from reaching the thyristor flow-through index. Even with the IGBT with the highest current rating, a single device cannot provide the current required for the melting of the 220kV transmission line. It must be connected in parallel or in parallel with the converter. For insulated gate bipolar transistor IGBTs, since the saturation voltage has a positive temperature coefficient over a wide current range, it is easy to achieve current sharing between parallel devices. In addition, even in the case of using a single IGBT device to meet the demand for melting current, since high voltage and high current IGBT devices are very expensive, it is often economical to use multiple IGBT devices with smaller current ratings and inverters in parallel. Program.

The DC ice-melting device can only be used for melting ice during the annual glazing period. If the DC ice-melting device can run in the static synchronous compensation mode during the non-glacial period, it can not only significantly improve the utilization rate of the equipment, but also make the DC ice-melting device. The dynamic reactive power balance and transient voltage support capability of the substation are improved, and the availability of the DC ice melting device during the icing period can also be ensured. Compared with the static var compensator (SVC) using thyristor, the STATCOM with voltage source converter has a small footprint, low operating loss, good harmonic characteristics, and strong dynamic reactive compensation.

Summary of the invention

The object of the present invention is to overcome the shortcomings of the prior art thyristor DC ice melting device and to provide a voltage source type DC ice melting and static synchronous compensation device capable of satisfying the melting requirements of various voltage level transmission lines.

Another object of the present invention is to provide a control method for a voltage source type DC ice melting device in consideration of the above problems. The present invention can realize the conversion between different functional modes, and satisfies the safe and rapid melting of ice on each line, and has no access point. Harmonic pollution and dynamic reactive compensation for the access point.

The technical solution of the present invention is: the voltage source type DC ice melting and static synchronous compensation device of the present invention, comprising at least one basic commutation unit including an isolating knife K, a circuit breaker QF, and a connecting reactor Ls, modular multilevel converter MMC with full bridge submodule, knife gate K1, K2, K3, K4, smoothing reactor Ld1, Ld2; modular multilevel converter MMC, connected reactor Ls and knife gates K1, K2, K3, K4 all include three phases a, b, c, and the three-phase structure is identical; wherein one end of the connected reactor Ls is connected to the AC side busbar through the isolating knife K and the circuit breaker QF. The other end is connected to the corresponding phase of the AC input terminal of the modular multilevel converter MMC adopting the full bridge submodule, that is, the a phase connected reactor Ls and the a phase of the modular multilevel converter MMC The connection points of the bridge arms are connected, the b-phase connected reactor Ls is connected to the connection point of the b-phase upper and lower arms of the modular multi-level converter MMC, the c-phase connected reactor Ls and the modular multi-level converter MMC The connection point of the c-phase upper and lower arms is connected, and one end of the knife K1 is combined with the modular multi-level commutation The upper ends of the upper arms of the MMC phases are respectively connected, and the other end of the K4 is short-circuited and connected to one end of the smoothing reactor Ld1; the three-phase of the K4 at the K4 is combined with the MMC of the modular multi-level converter MMC The lower ends of the lower bridge arms are respectively connected, and the other end of the knife gate K4 is short-circuited and connected to one end of the smoothing reactor Ld2; the two ends of the a-phase of the knife gate K2 are respectively connected to the modular multi-level converter MMC a The upper end of the bridge arm and the lower end of the b-phase upper arm, the two ends of the b-phase of the knife gate K2 are respectively connected to the upper end of the b-phase upper arm of the modular multi-level converter MMC and the lower end of the c-phase upper arm, the knife gate The two ends of the c-phase of K2 are respectively connected to the upper end of the c-phase upper arm of the modular multi-level converter MMC and the lower end of the upper arm of the a-phase; the two ends of the a-phase of the K3 switch are respectively connected to the modular multi-level exchange The upper end of the a-phase lower arm and the lower end of the b-phase lower arm of the flow MMC, the two ends of the b-phase of the K3 switch K3 are respectively connected to the b-phase lower arm upper end and the c-phase lower bridge of the modular multi-level converter MMC At the lower end of the arm, the two ends of the c-phase of the knife gate K3 are respectively connected to the upper end of the c-phase lower arm of the modular multi-level converter MMC and the lower end of the lower phase arm of the a-phase.

The basic converter unit is further connected with the knife gates Sd1, Sd2, Sd3, and Sd4, and the ice-melting connection knife gate Sa and the ice-melting short-circuit knife gate Sc. One end of the knife gate Sd1 is connected to one end of the knife gate Sd2 and then connected to the other end of the smoothing reactor Ld1. One end of the knife gate Sd3 is connected to one end of the knife gate Sd4, and then connected to the other end of the smoothing reactor Ld2. The other end of the knife gate Sd1 is connected to one end of the a1 phase of the melting ice bus B in the station, and the knife gate Sd2 The other end is connected to the other end of the knife gate Sd3 and then connected to one end of the b1 phase of the ice melting bus B in the station, and the other end of the knife gate Sd4 is connected to one end of the c1 phase of the ice melting bus B in the station, and the ice bus B in the station is connected. The other end of the a1, b1, and c1 phases is connected to one end of the a2, b2, and c2 phases of the AC line L to be melted by the ice-melting connection knife gate Sa, and the a2, b2, and c2 phases of the ice-exchanged AC line L are connected. The other end is connected to the corresponding end of the melted ice shorting knife gate Sc.

The control method of the voltage source type DC ice melting and static synchronous compensation device of the invention, the conversion method of the different functional modes is as follows:

1) "one relative phase" melting mode: when the a2 phase conductor and the b2 phase conductor are melted in series, the knife gates K1 and K4 are closed, the knife gates K2 and K3 are disconnected; Sd1 and Sd3 are closed, and Sd2 and Sd4 are disconnected; The melting ice connecting knife gate Sa is closed; the melting ice shorting knife gate is closed; the isolating knife gate K and the circuit breaker QF are closed;

2) "Two relative one phase" melting mode: When the a2 and b2 phase conductors are connected in parallel and then melted in series with the c2 phase conductor, the knife gates K1 and K4 are closed, the knife gates K2 and K3 are closed; and Sd1, Sd2 and Sd4 are closed. , Sd3 is disconnected; the melting ice connecting knife gate Sa is closed; the melting ice shorting knife gate is closed; the isolating knife gate K and the circuit breaker QF are closed;

3) DC side open circuit pressure test mode: knife gates K1, K4 are closed, knife gates K2, K3 are open; Sd1, Sd2, Sd3, Sd4 are disconnected; isolation knife gate K and circuit breaker QF are closed;

4) Static synchronous compensation mode: Knife switches K1 and K4 are disconnected, Knife switches K2 and K3 are closed; Isolation Knife K and circuit breaker QF are closed. One basic commutation unit is two parallel triangular connected chain static synchronous compensation. STATCOM device.

The control method of the voltage source type DC ice melting and static synchronous compensation device of the invention, when in the "one relative one phase" melting mode and the "one relative two phase" melting mode, comprises the following control steps:

1) Calculate the modular multilevel converter MMC DC side voltage reference according to the modular multilevel converter MMC DC side current command value I _{dc_ord} and the modular multilevel converter MMC DC side loop DC resistance R _{dc_loop} Value U _{dc_ref} :

U _{dc_ref} =I _{dc_ord} R _loop (1);

2) Subtract the modular multilevel converter MMC DC side current command value I _{dc_ord} minus the modular multilevel converter MMC DC side current measured value I _dc , get the error, and then signalize it to get modular Multi-level converter MMC AC side current active axis component reference value I _dref ; the signal processing method is proportional integral adjustment;

3) The modular multi-level converter MMC reactive power command value Q _{ord is} subtracted from the measured value Q of the reactive power, and the error is obtained. After the signal processing, the modular multi-level converter MMC AC side output is obtained. The current reactive power component reference value I _qref ; the signal processing method is proportional integral adjustment; wherein the reactive power command value Q _ord is manually set or the controller calculates according to the design logic, and the reactive power measured value Q is according to the module. The multi-level converter MMC is connected to the reactor Ls grid voltages (u _sa , u _sb and u _sc ) and currents (i _a , i _b and i _c ) are calculated;

4) The modular multilevel converter MMC AC side currents i _a , i _b and i _c are Park transformed, that is, multiplied by the transformation matrix P _{abc / dq} to obtain the AC side current active axis component measured value i _d and the measured value of the reactive axis component i _q ;

The modular multilevel converter MMC is connected to the reactor Ls network side three-phase voltages u _sa , u _sb and u _sc for Park transformation, that is, multiplied by the transformation matrix P _{abc / dq} to obtain the connected reactor Ls network The measured value of the active voltage component of the side voltage u _sd and the measured value of the reactive power component u _sq ;

Wherein, the transformation matrix P _{abc/dq is in the} form

Where θ = ω ₀ t, ω ₀ is the fundamental frequency of the grid, and t is time.

5) Subtract the measured value of the current active axis component by subtracting the measured value i _d from the MMC AC side active active component reference value I _{dref of the} modular multilevel converter, and subtracting the feedforward amount ω ₀ Li after signal processing _q , then subtract the measured value u _{sd of the} active-axis component of the Ls on the grid side of the connected reactor Ls, and obtain the reference value u _{cd_ref of the} active side component of the MMC AC side of the modular multilevel converter; the signal processing method is proportional integral adjustment ;

The modular multi-level converter MMC AC side current reactive-axis component reference value I _{qref is} subtracted from the measured value i _{q to} obtain the current reactive-axis component error value, and the signal processing is followed by the feedforward amount ω ₀ Li _d , plus the measured value of the voltage reactive component, u _sq , to obtain the modular multilevel converter MMC AC side voltage reactive component reference value u _{cq_ref} ; the signal processing method is proportional integral adjustment;

The L is an equivalent AC network side reactance, which is 1/2 of the bridge arm reactance L _c plus the connection reactance L _s , that is,

6) _Performing Park inverse transformation, ie multiplication by transformation matrix, of the modular multilevel converter MMC AC side voltage active axis component reference value u _{cd_ref} and voltage reactive power component reference value u _{cq_ref}

Obtaining the MMC AC side three-phase voltage reference values u _{ca_ref} , u _{cb_ref} and u _{cc_ref of the modular multilevel converter} ;

Among them, the transformation matrix

In the form of

7) Subtract the a-phase bridge arm reference voltage compensation amount U _{compa_ref} for loop suppression with 1/2 of the modular multilevel converter MMC DC side voltage reference U _{dc —} _ref , and subtract the modular multi-level swap The current-side voltage a phase reference value u _{ca_ref of the} current collector MMC is obtained, and the reference value u _{pa_ref} of the bridge arm voltage on the a-phase is _obtained ; and the a-phase bridge arm reference for loop suppression is subtracted by 1/2 of the DC-side voltage reference value U _{dc_ref} voltage compensation amount _U compb_ref, minus modular multilevel converter MMC phase AC side voltage of the reference value b _u cb_ref, to give the b-phase voltage reference values arm _u pb_ref; DC side voltage of the reference value U _{dc_ref} 1/2 minus the a-phase bridge arm reference voltage compensation amount U _{compc_ref} for the loop suppression, and subtracting the modular multi-level converter MMC AC side voltage c-phase reference value u _{cc_ref} to obtain the c-phase upper arm voltage Reference value u _{pc_ref;}

Subtracting the a-phase arm reference voltage compensation amount U _{compa_ref} for loop suppression with 1/2 of the modular multilevel converter MMC DC side voltage reference U _{dc —} _ref , plus a modular multilevel converter MMC AC side voltage with a reference value _u ca_ref, to give the a-phase lower arm voltage reference value _u na_ref; b-phase arm with DC voltage reference value U _{dc_ref} subtracting the 1/2 of the reference voltage compensation loop suppression the amount of _U compb_ref, plus modular multilevel converter MMC phase AC side voltage of the reference value b _u cb_ref, to obtain the reference value _u nb_ref b-phase lower arm voltage; DC-side voltage reference U _{dc_ref} 1 / 2 Subtracting the c-phase bridge arm reference voltage compensation amount U _{compc_ref} for loop suppression, plus the modular multi-level converter MMC AC side voltage c-phase reference value u _{cc_ref} , to obtain the reference of the c-phase lower arm voltage Value u _{nc_ref} ;

Wherein, the loop suppression uses the double-fundamental frequency negative sequence rotation coordinates to detect the detected multi-level inverter MMC upper and lower arm currents i _pa , i _pb , i _pc , i _na , i _nb and i _nc . After processing, the bridge arm reference voltage compensation amounts U _{compa_ref} , U _{compb_ref} and U _{compc_ref} for loop suppression are obtained by the proportional integrator and feedforward compensation;

8) The obtained modular multilevel converter MMC upper and lower arm voltage reference values u _{pa_ref} , u _{pb_ref} , u _{pc — ref} , u _{na — ref} , u _{nb — ref} and u _{nc — ref are controlled} by a pulse width modulation method to generate corresponding trigger pulses The turn-on and turn-off of the full-control device in each sub-module on the bridge arm enables the actual value of the bridge arm voltage to be the same as the bridge arm voltage reference value, thereby realizing the control of the voltage of each bridge arm;

When the static synchronous compensation is in the DC side open circuit pressure test mode, the following control steps are included:

1) Subtract the modular multilevel converter MMC DC side voltage command value U _{dc_ord} minus the modular multilevel converter MMC DC side voltage measured value U _dc to obtain the error, and then signalize it to obtain modularity. Multi-level converter MMC AC side current active axis component reference value I _dref ; the signal processing method is proportional integral adjustment;

2) The modular multilevel converter MMC AC side currents i _a , i _b and i _c are Park-transformed, that is, multiplied by the transformation matrix P _abc/dq to obtain the measured value of the AC active current component of the AC side. _d and the measured value of the reactive axis component i _q ;

3) Subtract the measured value of the current active axis component by subtracting the measured value i _d from the MMC AC side active active component reference value I _{dref of the} modular multilevel converter, and subtracting the feedforward amount ω ₀ Li after signal processing _q , then subtract the measured value u _{sd of the} active-axis component of the Ls grid side of the connected reactor, and obtain the reference value u _{cd_ref of the} active side component of the MMC AC side of the modular multilevel converter; the signal processing method is proportional integral adjustment ;

In the DC side open circuit pressurization test mode, the reference value I _{qref of the} AC side current reactive power component of the modular multilevel converter MMC is _{set to} zero, and the measured value i _q is subtracted to obtain the current reactive power component. The error value, after signal processing, plus the feedforward amount ω ₀ Li _d , plus the measured value of the voltage reactive power component u _sq , the modular multilevel converter MMC AC side voltage reactive power component reference a value u _{cq_ref} ; the signal processing method is proportional integral adjustment;

4) The modular multi-level converter MMC AC side voltage active axis component reference value u _{cd_ref} and the voltage reactive power component reference value u _{cq_ref} are inversely transformed by Park, that is, multiplied by a transformation matrix

5) Subtract the modular multilevel converter MMC AC side voltage a phase reference value u _{ca_ref} with 1/2 of the modular multilevel converter MMC DC side voltage command value U _{dc_ord to} obtain the a phase upper arm The reference value u _{pa_ref of the} voltage is subtracted from the _modulo multi-level converter MMC AC side voltage b phase reference value u _{cb_ref} by 1/2 of the DC side voltage command value U _{dc_ord to obtain} the reference value of the b-stage upper arm voltage _u pb_ref; 1/2 subtracted value _U dc_ord modular multilevel converter MMC phase AC side voltage of the reference value c _u cc_ref, c to give the reference phase voltage values arm _u pc_ref side DC voltage command;

Using the modular multilevel converter MMC DC side voltage command value U _{dc_ord} 1/2 plus the modular multilevel converter MMC AC side voltage a phase reference value u _{ca_ref} , to obtain the a phase lower arm voltage reference value _u na_ref; _U dc_ord value of DC-side voltage command plus 1/2 of a modular multi-level converter MMC phase AC side voltage reference value b _u cb_ref, to give the b-phase lower arm reference voltage value _u nb_ref Using the 1/2 of the DC side voltage command value U _{dc_ord} plus the modular multilevel converter MMC AC side voltage c phase reference value u _{cc_ref} , the reference value u _{nc_ref} of the c-phase lower arm voltage is _obtained ;

6) The obtained modular multilevel converter MMC upper and lower arm voltage reference values u _{pa_ref} , u _{pb_ref} , u _{pc_ref} , u _{na_ref} , u _{nb_ref} and u _{nc_ref are controlled} by a pulse width modulation method to generate a corresponding trigger pulse The turn-on and turn-off of the fully controlled device in each sub-module of the bridge arm enables the actual value of the bridge arm voltage to be the same as the bridge arm voltage reference value, thereby realizing the control of the voltage of each bridge arm.

The composition of the invention fully utilizes the characteristics that the full bridge sub-module can output positive, zero and negative three module voltages, so that the converter DC voltage and the direct current can be continuously adjustable between the maximum allowable value and zero, The DC ice melting device can meet the needs of multiple ice melting lines of different lengths, different resistivities and different voltage levels, and in all operating conditions, the power quality of the AC side can be guaranteed, and there is almost no communication system. influential. The invention utilizes the full control type device parallel and inverter parallel technology to meet the large current required for the high voltage level transmission line melting ice, so that the voltage source type DC ice melting device can be used for each voltage level transmission line. The conversion method between the different functional modes of the voltage source type DC ice melting and static synchronous compensation device of the invention is simple and convenient, and the control method of the DC ice melting device is simple and convenient. The voltage source type DC ice melting and static synchronous compensation device of the present invention operates as a static synchronous compensation device using a chain-connected STATCOM device. The invention has reasonable design, convenient and practical, and can be used for newly-built DC ice-melting project, and can also be used for upgrading and transforming a DC ice-melting device in an already established DC ice-melting project, and has broad application prospects.

DRAWINGS

The invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

1 is a schematic structural view of a voltage source type DC ice melting and static synchronous compensation device using a basic converter unit according to Embodiment 1 of the present invention.

2 is a schematic structural view of a voltage source type DC ice melting and static synchronous compensation device using M basic commutation units according to Embodiment 2 of the present invention.

3 is a schematic diagram of a control strategy in a DC melt mode of a voltage source type DC ice melting and static synchronous compensation device according to the present invention.

4 is a schematic diagram of a control strategy in a DC-side open-circuit pressurization test mode of a voltage source type DC ice-melting and static synchronous compensation device according to the present invention.

FIG. 5 is a schematic structural diagram of a full bridge submodule using a single full control device according to Embodiment 3 of the present invention.

FIG. 6 is a schematic structural diagram of a full bridge sub-module in which a dual full control device is connected in parallel according to Embodiment 4 of the present invention.

FIG. 7 is a schematic structural diagram of a full bridge sub-module in which a plurality of fully-controlled devices are connected in parallel according to Embodiment 5 of the present invention.

detailed description

Example 1:

FIG. 1 is a schematic diagram showing the structure of a voltage source type DC ice melting and static synchronous compensation device according to the present invention. The voltage source type DC ice melting and static synchronous compensation device of the present invention includes at least one basic commutation unit, and the basic conversion The flow unit includes an isolation knife gate K, a circuit breaker QF, a connection reactor Ls, a modular multilevel converter MMC with a full bridge submodule, knife switches K1, K2, K3, K4, and a smoothing reactor Ld1. Ld2; wherein the modular multi-level converter MMC, the connected reactor Ls and the knife gates K1, K2, K3, K4 all comprise three phases a, b, c, and the three-phase structure is identical; wherein the reactor Ls is connected One end is connected to the AC side busbar through the isolation knife gate K and the circuit breaker QF, and the other end is connected to the corresponding AC input end of the modular multilevel converter MMC adopting the full bridge submodule, that is, the a phase connection reactance Ls and modular multi-level switching The connection point of the upper and lower arms of the a-phase of the flow device MMC is connected, and the connection phase of the b-phase connected reactor Ls is connected with the connection point of the b-phase upper and lower arms of the modular multi-level converter MMC, and the c-phase connected reactor Ls and modular The multi-level converter MMC is connected to the connection point of the c-phase upper and lower arms, and one end of the K1 is connected to the upper end of the upper arm of the modular multi-level converter MMC, and the other end of the K1 is K3. After short circuiting, it is connected with one end of the smoothing reactor Ld1; the three phases of one end of the knife gate K4 are respectively connected with the lower ends of the lower arm of each phase of the modular multilevel converter MMC, and the other end of the knife gate K4 is short-circuited by three phases. Connected to one end of the smoothing reactor Ld2; the two ends of the a-phase of the knife K2 are respectively connected to the upper end of the a-phase upper arm of the modular multi-level converter MMC and the lower end of the b-phase upper arm, the b of the K2 The two ends of the phase are respectively connected to the upper end of the b-phase upper arm of the modular multi-level converter MMC and the lower end of the c-phase upper arm, and the two ends of the c-phase of the knife K2 are respectively connected to the modular multi-level converter MMC The upper end of the c-phase upper arm and the lower end of the a-phase upper arm; the two ends of the a-phase of the K3 switch K3 are respectively connected to the upper end of the a-phase lower arm of the modular multi-level converter MMC and the b-phase At the lower end of the bridge arm, the two ends of the b-phase of the knife gate K3 are respectively connected to the upper end of the b-phase lower arm of the modular multi-level converter MMC and the lower end of the c-phase lower arm, and the two ends of the c-phase of the knife gate K3 are respectively connected Modular multilevel converter MMC has the lower end of the c-phase lower arm and the lower end of the a-phase lower arm.

In order to realize the voltage source type DC ice melting and static synchronous compensation, the above basic converter unit is also connected with the knife gates Sd1, Sd2, Sd3, Sd4, the ice melting connecting knife gate Sa and the melting ice shorting knife gate Sc. One end of the knife gate Sd1 is connected to one end of the knife gate Sd2 and then connected to the other end of the smoothing reactor Ld1. One end of the knife gate Sd3 is connected to one end of the knife gate Sd4, and then connected to the other end of the smoothing reactor Ld2. The other end of the knife gate Sd1 is connected to one end of the a1 phase of the melting ice bus B in the station, and the other end of the knife gate Sd2 is connected to the other end of the knife gate Sd3, and then connected to one end of the b1 phase of the ice melting bus B in the station. The other end of the Sd4 is connected to one end of the c1 phase of the melting ice bus B in the station, and the other end of the a1, b1, and c1 phases of the melting ice bus B in the station is connected to the a2 and b2 of the AC line L to be melted by the ice melting. One end of the c2 phase is connected, and the other end of the a2, b2, and c2 phases of the ice-melting AC line L is connected to the corresponding end of the ice-shrinking knife gate Sc.

The above-mentioned modular multilevel converter MMC is a three-phase six-bridge arm structure, each bridge arm is composed of a reactor Lc and N full bridge sub-modules SM connected in series, N is a positive integer, and each full bridge sub-module The internal structure is the same; the upper and lower bridge arm reactors of each phase are connected in series in the same direction, that is, the non-identical end of the upper arm reactor Lc and the same end of the lower arm are connected together and connected with the corresponding phase of the connected reactor Ls, three The other ends of the upper arms are connected to form a DC side positive pole, and the other ends of the three lower arms are connected together to form a DC side negative pole.

The full bridge submodule in the modular multilevel converter MMC using the full bridge submodule adopts a full bridge submodule of a single full control device, or a full bridge submodule in which a dual full control device is connected in parallel, or adopts multiple Full-bridge sub-module with full-controlled devices in parallel.

U _{dc_ref} =I _{dc_ord} R _loop (1);

Wherein, the transformation matrix P _{abc/dq is in the} form

5) Subtract the measured value of the current active axis component by subtracting the measured value i _d from the MMC AC side active active component reference value I _{dref of the} modular multilevel converter, and subtracting the feedforward amount ω ₀ Li after signal processing _q , then subtract the measured value u _{sd of the} active-axis component of the Ls grid side of the connected reactor, and obtain the reference value u _{cd_ref of the} active side component of the MMC AC side of the modular multilevel converter; the signal processing method is proportional integral adjustment ;

The modular multi-level converter MMC AC side current reactive-axis component reference value I _{qref is} subtracted from the measured value i _{q to} obtain the current reactive-axis component error value, and the signal processing is followed by the feedforward amount ω ₀ Li _d , plus the measured value of the voltage reactive power component u _sq , to obtain the modular multi-level converter MMC AC side voltage reactive power component reference value u _{cq_ref} ; the signal processing method is proportional integral adjustment;

Among them, the transformation matrix

In the form of

7) Subtract the a-phase bridge arm reference voltage compensation amount U _{compa_ref} for loop suppression with 1/2 of the modular multilevel converter MMC DC side voltage reference U _{dc —} _ref , and subtract the modular multi-level swap The current-side voltage a phase reference value u _{ca_ref of the} current collector MMC is obtained, and the reference value u _{pa_ref} of the bridge arm voltage on the a-phase is _obtained ; and the a-phase bridge arm reference for loop suppression is subtracted by 1/2 of the DC-side voltage reference value U _{dc_ref} voltage compensation amount _U compb_ref, minus modular multilevel converter MMC phase AC side voltage of the reference value b _u cb_ref, to give the b-phase voltage reference values arm _u pb_ref; DC side voltage of the reference value U _{dc_ref} 1/2 minus the a-phase bridge arm reference voltage compensation amount U _{compc_ref} for the loop suppression, and subtracting the modular multi-level converter MMC AC side voltage c-phase reference value u _{cc_ref} to obtain the c-phase upper arm voltage Reference value u _{pc_ref} ;

8) The obtained modular multilevel converter MMC upper and lower arm voltage reference values u _{pa_ref} , u _{pb_ref} , u _{pc — ref} , u _{na — ref} , u _{nb — ref} and u _{nc — ref are controlled} by a pulse width modulation method to generate corresponding trigger pulses The turn-on and turn-off of the fully controlled device in each sub-module of the bridge arm enables the actual value of the bridge arm voltage to be the same as the bridge arm voltage reference value, thereby realizing the control of the voltage of each bridge arm.

The control method of the voltage source type DC ice melting and static synchronous compensation device of the invention, when in the DC side open circuit pressure test mode, comprises the following control steps:

4) _Performing Park inverse transformation, ie multiplication by transformation matrix, of the modular multilevel converter MMC AC side voltage active axis component reference value u _{cd_ref} and voltage reactive power component reference value u _{cq_ref}

5) Subtract the modular multilevel converter MMC AC side voltage a phase reference value u _{ca_ref} with 1/2 of the modular multilevel converter MMC DC side voltage command value U _{dc_ord to} obtain the a phase upper arm The reference value u _{pa_ref of the} voltage is subtracted from the _modulo multi-level converter MMC AC side voltage b phase reference value u _{cb_ref} by 1/2 of the DC side voltage command value U _{dc_ord to obtain} the reference value of the b-stage upper arm voltage _u pb_ref; command value _U dc_ord subtracting 1/2 modular multilevel converter MMC phase AC side voltage of the reference value c _u cc_ref, c obtained reference phase voltage values on the arm with the DC voltage _u pc_ref;

Using the modular multilevel converter MMC DC side voltage command value U _{dc_ord} 1/2 plus the modular multilevel converter MMC AC side voltage a phase reference value u _{ca_ref} , to obtain the a phase lower arm voltage reference value _u na_ref; _U dc_ord value of DC-side voltage command plus 1/2 of a modular multi-level converter MMC phase AC side voltage reference value b _u cb_ref, b obtained with the reference voltage value lower arm _u nb_ref Using the 1/2 of the DC side voltage command value U _{dc_ord} plus the modular multilevel converter MMC AC side voltage c phase reference value u _{cc_ref} , the reference value u _{nc_ref} of the c-phase lower arm voltage is _obtained ;

Example 2:

The structure diagram of the voltage source type DC ice melting and static synchronous compensation device of the present invention is shown in FIG. 2, and includes M basic commutation units, wherein M is a positive integer; M basic wave commutation unit smoothing reactor Ld1 One ends of the smoothing reactors Ld2 of the M basic converter units are connected together, and one ends of the knife switches Sd1 and Sd2 are connected to the other end of the smoothing reactor Ld1 of the M basic converter units. One ends of the knife gates Sd3 and Sd4 are connected to the other end of the smoothing reactor Ld2 of the M basic converter units, and the other end of the knife gate Sd1 is connected to one end of the a1 phase of the ice melting bus bar B in the station, and the knife gate Sd2 After being connected to the other end of Sd3, it is connected to one end of the b1 phase of the melting ice bus B in the station, and the other end of the knife gate Sd4 is connected to one end of the c1 phase of the ice melting bus B in the station, and a1, b1, c1 of the ice bus B in the station are connected. The other end of the phase is connected to the end of the a2, b2, and c2 phases of the AC line L to be melted by the ice-melting connection knife gate Sa, and the other end of the a2, b2, and c2 phases of the ice-melting AC line L is short with the melting ice. The corresponding ends of the knife gates Sc are connected.

The above-mentioned modular multilevel converter MMC is a three-phase six-bridge arm structure, each bridge arm is composed of a reactor Lc and N full bridge sub-modules SM connected in series, N is a positive integer, and each full bridge sub-module Internal structure Same; each phase upper and lower bridge arm reactors are connected in series in the same direction, that is, the non-identical end of the upper arm reactor Lc and the same end of the lower arm are connected together and connected with the corresponding connection of the connected reactor Ls, three upper bridges The other ends of the arms are connected to form a DC side positive electrode, and the other ends of the three lower arms are connected to form a DC side negative electrode.

The full bridge submodule in the modular multilevel converter MMC using the full bridge submodule described above may be a full bridge submodule of a single fully controlled device, or a full bridge submodule in which a dual full control device is connected in parallel, or Full-bridge sub-module with multiple fully-controlled devices in parallel.

Example 3:

The structure of the voltage source type DC ice melting and static synchronous compensation device of the present invention is the same as that of Embodiment 1 or Embodiment 2, wherein the full bridge submodule in the modular multilevel converter MMC adopts a single fully controlled device. The full-bridge sub-module, the schematic diagram of the full-bridge sub-module using a single-full-control device is shown in Figure 5, including four fully-controlled devices S1, S2, S3, S4, four diodes D1, D2, D3, D4 , a capacitor C, a thyristor SCR, a fast switch Ks, the full control device S1 and the diode D1 are anti-parallel, the full control device S2 and the diode D2 are connected in anti-parallel, the full control device S3 and the diode D3 are anti-parallel, The fully-controlled device S4 is connected in parallel with the diode D4, that is, the positive terminal of the fully-controlled device is connected to the negative terminal of the diode, and the negative terminal of the fully-controlled device is connected to the positive terminal of the diode; the negative terminal of the fully-controlled device S1 and the fully-controlled device The positive terminal connection of S2 constitutes one end of the full bridge submodule, and the negative terminal of the full control device S3 is connected with the positive terminal of the full control device S4 to form the other end of the full bridge submodule; the full control device S1 The positive terminal of the positive terminal and the fully controlled device S3 is connected to one end of the capacitor C. The negative terminal of the fully controlled device S4 and the negative terminal of the fully controlled device S2 are connected to the other end of the capacitor C; the fast switch Ks is connected to both ends of the full H-bridge module; the thyristor SCR is connected to the full bridge Both ends of the submodule.

Example 4:

The structure of the voltage source type DC ice melting and static synchronous compensating device of the present invention is the same as that of Embodiment 1 or Embodiment 2, wherein the full bridge submodule in the modular multilevel converter MMC is connected in parallel by a dual full control device. The full-bridge sub-module, the schematic diagram of the full-bridge sub-module with dual full-control devices connected in parallel is shown in Figure 6, including eight fully-controlled devices S11, S21, S31, S41, S12, S22, S32, S42, and eight. Diodes D11, D21, D31, D41, D12, D22, D32, D42, a capacitor C, a thyristor SCR, a fast switch Ks, in which the fully-controlled device S11 and the diode D11 are connected in anti-parallel, the fully-controlled device S21 and Diode D21 is anti-parallel, full-controlled device S31 and diode D31 are connected in anti-parallel, full-controlled device S41 and diode D41 are connected in anti-parallel, full-control device S12 and diode D12 are connected in anti-parallel, fully-controlled device S22 and diode D22 Reverse parallel, full-controlled device S32 and diode D32 are connected in anti-parallel, fully-controlled device S42 The parallel connection with the diode D42; the negative terminal of the full control device S11 and the negative terminal of the fully controlled device S12 are connected with the positive terminal of the full control device S21 and the positive terminal of the full control device S22 to form the full bridge submodule At one end, the negative terminal of the fully-controlled device S31 and the negative terminal of the fully-controlled device S32 are connected to the positive terminal of the full-control device S41 and the positive terminal of the full-control device S42 to form the other end of the full-bridge sub-module; The positive terminal of the device S11 and the positive terminal of the fully-controlled device S12 are connected to the positive terminal of the full-control device S31 and the positive terminal of the fully-controlled device S32, and are connected to one end of the capacitor C, and the negative terminal of the fully-controlled device S41. The negative terminal of the full control device S42 is connected to the negative terminal of the full control device S21 and the negative terminal of the full control device S22, and is connected to the other end of the capacitor C; the fast switch Ks is connected to both ends of the full bridge submodule; The thyristor SCR is connected to both ends of the full bridge sub-module, that is, a fully-controlled device corresponding to the position of the full-bridge sub-module of the single-full-control device-diode anti-parallel pair is changed into two parallel-connected full-control devices- The diodes are anti-parallel pairs.

Example 5:

The structure of the voltage source type DC ice melting and static synchronous compensation device of the present invention is the same as that of Embodiment 1 or Embodiment 2, wherein the full bridge submodule in the modular multilevel converter MMC uses a plurality of fully controlled devices. Parallel connection, the schematic diagram of the full-bridge sub-module with multiple fully-controlled devices connected in parallel is shown in Figure 7. A fully-controlled device corresponding to the position of the full-bridge sub-module of the single-full-control device will be used. For multi-parallel fully controlled devices - diode anti-parallel pairs.

Claims

A voltage source type DC ice melting and static synchronous compensation device comprises: at least one basic commutation unit; the basic commutation unit comprises: an isolating knife gate K, a circuit breaker QF, a connected reactor Ls, and a full bridge submodule Modular multilevel converter MMC, knife gates K1, K2, K3, K4, smoothing reactors Ld1, Ld2;

The modular multilevel converter MMC, the connected reactor Ls, and the knife gates K1, K2, K3, and K4 all include three phases a, b, and c, and the three-phase structures are identical;

Wherein, one end of the connected reactor Ls is connected to the AC side busbar through the isolating knife K and the circuit breaker QF, and the other end is corresponding to the AC input end of the modular multilevel converter MMC using the full bridge submodule. Connected separately, that is, the a-phase connected reactor Ls is connected to the connection point of the a-phase upper and lower arms of the modular multi-level converter MMC, and the b-phase connected reactor Ls and the b-phase of the modular multi-level converter MMC The connection points of the upper and lower arms are connected, and the c-phase connected reactor Ls is connected to the connection point of the c-phase upper and lower arms of the modular multi-level converter MMC. One end of the K1 is connected to the modular multi-level converter MMC The upper ends of the upper arm of each phase are respectively connected, and the other end of the knife K1 is short-circuited and connected to one end of the smoothing reactor Ld1; the three-phase of the K4 at the K4 is combined with the modular multi-level converter MMC The lower ends of the bridge arms are respectively connected, and the other end of the knife gate 4 is short-circuited and connected to one end of the smoothing reactor Ld2; the two ends of the a-phase of the knife gate K2 are respectively connected to the phase a of the modular multi-level converter MMC The upper end of the upper arm and the lower end of the b-phase upper arm, the two ends of the b-phase of the knife K2 are respectively connected to the modular multi-level converter MMC The upper end of the b-phase upper arm and the lower end of the c-phase upper arm, the two ends of the c-phase of the knife K2 are respectively connected to the upper end of the c-phase upper arm of the modular multi-level converter MMC and the lower end of the upper arm of the a-phase; The two ends of the a-phase of the gate K3 are respectively connected to the upper end of the a-phase lower arm of the modular multi-level converter MMC and the lower end of the b-phase lower arm, and the two ends of the b-phase of the knife K3 are respectively connected to the modular multi-level The lower end of the b-phase lower arm of the converter MMC and the lower end of the lower arm of the c-phase, the two ends of the c-phase of the knife K3 are respectively connected to the upper end of the c-phase lower arm of the modular multi-level converter MMC and the a phase The lower end of the bridge arm.
The voltage source type DC ice-melting and static synchronous compensation device according to claim 1, wherein the basic commutation unit is further connected with knife gates Sd1, Sd2, Sd3, and Sd4, and the ice-melting connection knife gate Sa and the fusion device. The ice short-circuiting knife gate Sc, one end of the knife gate Sd1 is connected with one end of the knife gate Sd2 and then connected to the other end of the smoothing reactor Ld1, one end of the knife gate Sd3 is connected with one end of the knife gate Sd4 and then with the smoothing reactance The other end of the device Ld2 is connected, and the other end of the knife gate Sd1 is connected to one end of the a1 phase of the ice melting bus B in the station, and the knife gate Sd2 The other end is connected to the other end of the knife gate Sd3 and then connected to one end of the b1 phase of the ice melting bus B in the station, and the other end of the knife gate Sd4 is connected to one end of the c1 phase of the ice melting bus B in the station, and the ice bus B in the station is connected. The other end of the a1, b1, and c1 phases is connected to one end of the a2, b2, and c2 phases of the AC line L to be melted by the ice-melting connection knife gate Sa, and the a2, b2, and c2 phases of the ice-exchanged AC line L are connected. The other end is connected to the corresponding end of the melted ice shorting knife gate Sc.
The voltage source type DC ice-melting and static synchronization compensating apparatus according to claim 1, wherein said apparatus comprises M basic commutation units, wherein M is a positive integer; and flat waves of M basic commutation units are provided. One ends of the reactor Ld1 are connected together, one ends of the smoothing reactors Ld2 of the M basic converter units are connected together, and one end of the knife gate Sd1 is connected to one end of the knife gate Sd2 and then connected to the M basic converter units. The other end of the wave reactor Ld1 is connected, one end of the knife switch Sd3 is connected to one end of the knife gate Sd4, and then connected to the other end of the smoothing reactor Ld2 of the M basic converter units, and the other end of the knife gate Sd1 is integrated with the station inside. One end of the a1 phase of the ice bus B is connected, and the other end of the knife gate Sd2 is connected to the other end of the Sd3, and then connected to one end of the b1 phase of the ice bus B in the station, and the other end of the knife gate Sd4 and the ice bus B of the station One end of the c1 phase is connected, and the other end of the a1, b1, and c1 phases of the ice-melting bus B in the station is connected to one end of the a2, b2, and c2 phases of the AC line L to be melted by the ice-melting connection knife Sa, to be melted. The other end of the a2, b2, and c2 phases of the AC line L and the melted ice short circuit switch Sc The corresponding terminal.
The voltage source type DC ice melting and static synchronous compensation device according to claim 1, wherein the modular multilevel converter MMC is a three-phase six-bridge arm structure, and each bridge arm is composed of a reactor. Lc and N full bridge submodules SM are formed in series, N is a positive integer, and the internal structure of each full bridge submodule is the same; each phase upper and lower bridge arm reactors are connected in series in the same direction, that is, the non-same name of the upper arm reactor Lc The end of the same name of the lower arm and the lower end of the lower arm are connected to the corresponding phase of the connected reactor Ls, and the other ends of the three upper arms are connected to form a DC positive pole, and the other ends of the three lower arms are connected together. DC side negative.
The voltage source type DC ice melting and static synchronous compensation device according to any one of claims 1 to 4, characterized in that: the full bridge in the modular multilevel converter MMC using the full bridge submodule The module adopts a full-bridge sub-module of a single-full-control device, or a full-bridge sub-module in which a dual-full-control device is connected in parallel, or a full-bridge sub-module in which multiple fully-controlled devices are connected in parallel.
The voltage source type DC ice melting and static synchronous compensation device according to claim 5, wherein the full bridge submodule adopting a single full control device comprises four full control devices S1, S2, S3, and S4. , four diodes D1, D2, D3, D4, a capacitor C, a thyristor SCR, a fast switch Ks, The fully-controlled device S1 and the diode D1 are connected in anti-parallel, the fully-controlled device S2 and the diode D2 are connected in anti-parallel, the fully-controlled device S3 and the diode D3 are connected in anti-parallel, and the fully-controlled device S4 and the diode D4 are connected in anti-parallel, that is, The positive terminal of the control device is connected to the negative terminal of the diode, and the negative terminal of the full control device is connected with the positive terminal of the diode; the negative terminal of the fully controlled device S1 is connected with the positive terminal of the fully controlled device S2 to form one end of the full bridge submodule. The negative terminal of the full control device S3 is connected to the positive terminal of the full control device S4 to form the other end of the full bridge submodule; the positive terminal of the full control device S1 and the positive terminal of the fully controlled device S3 and the capacitor C One end is connected, the negative terminal of the full control device S4 and the negative terminal of the full control device S2 are connected to the other end of the capacitor C; the fast switch Ks is connected to both ends of the full H bridge module; the thyristor SCR is connected to Both ends of the full bridge submodule.
The voltage source type DC ice-melting and static synchronous compensation device according to claim 5, wherein the full-bridge sub-module adopting the dual-full-control device in parallel comprises eight fully-controlled devices S11, S21, and S31. S41, S12, S22, S32, S42, eight diodes D11, D21, D31, D41, D12, D22, D32, D42, one capacitor C, one thyristor SCR, one fast switch Ks, of which fully controlled device S11 and diode D11 anti-parallel, full control device S21 and diode D21 anti-parallel, full control device S31 and diode D31 anti-parallel, full control device S41 and diode D41 anti-parallel, full control device S12 and diode D12 anti Parallel connection, full control device S22 and diode D22 are connected in reverse parallel, full control device S32 and diode D32 are connected in anti-parallel, full control device S42 and diode D42 are connected in parallel; negative control and full control of full control device S11 The negative terminal of the device S12 is connected with the positive terminal of the full control device S21 and the positive terminal of the full control device S22 to form one end of the full bridge submodule, the negative terminal of the full control device S31 and the negative terminal of the fully controlled device S32. Positive and full control type with fully controlled device S41 The positive terminal of the device S42 is connected to form the other end of the full bridge submodule; the positive terminal of the fully controlled device S11 and the positive terminal of the fully controlled device S12 and the positive terminal of the fully controlled device S31 and the positive control device S32 are positive. The terminal is connected and connected to one end of the capacitor C. The negative terminal of the full control device S41 and the negative terminal of the full control device S42 are connected to the negative terminal of the full control device S21 and the negative terminal of the full control device S22, and the capacitor The other end of the C is connected; the fast switch Ks is connected to the two ends of the full bridge submodule; the thyristor SCR is connected to the two ends of the full bridge submodule, that is, a full position of the full bridge submodule corresponding to the single full control device is used. The control device-diode anti-parallel pair is changed to two parallel fully-controlled devices-diode anti-parallel pairs.
The voltage source type DC ice-melting and static synchronous compensation device according to claim 5, wherein the full-bridge sub-module in which the multi-fully controlled device is connected in parallel is to be corresponding to a full-bridge sub-module of a single fully-controlled device. Position of a fully controlled device - diode anti-parallel pair changed to multiple parallel fully controlled devices - two The pole tube is anti-parallel.
A control method for a voltage source type DC ice melting and static synchronous compensation device is characterized in that: the conversion methods of different functional modes are as follows:

1) "one relative phase" melting mode: when the a2 phase conductor and the b2 phase conductor are melted in series, the knife gates K1 and K4 are closed, the knife gates K2 and K3 are disconnected; Sd1 and Sd3 are closed, and Sd2 and Sd4 are disconnected; The melting ice connecting knife gate Sa is closed; the melting ice shorting knife gate is closed; the isolating knife gate K and the circuit breaker QF are closed;

2) "Two relative one phase" melting mode: When the a2 and b2 phase conductors are connected in parallel and then melted in series with the c2 phase conductor, the knife gates K1 and K4 are closed, the knife gates K2 and K3 are closed; and Sd1, Sd2 and Sd4 are closed. , Sd3 is disconnected; the melting ice connecting knife gate Sa is closed; the melting ice shorting knife gate is closed; the isolating knife gate K and the circuit breaker QF are closed;

3) DC side open circuit pressure test mode: knife gates K1, K4 are closed, knife gates K2, K3 are open; Sd1, Sd2, Sd3, Sd4 are disconnected; isolation knife gate K and circuit breaker QF are closed;

4) Static synchronous compensation mode: Knife switches K1 and K4 are disconnected, Knife switches K2 and K3 are closed; Isolation Knife K and circuit breaker QF are closed. One basic commutation unit is two parallel triangular connected chain static synchronous compensation. STATCOM device.
The control method of the voltage source type DC ice-melting and static synchronization compensating device according to claim 9, characterized in that, when in the "one relative one phase" melting mode and the "one relative two phase" melting mode, the following includes Control steps:

1) Calculate the modular multilevel converter MMC DC side voltage reference according to the modular multilevel converter MMC DC side current command value I dc_ord and the modular multilevel converter MMC DC side loop DC resistance R dc_loop Value U dc_ref :

U dc_ref =I dc_ord R loop (1);

2) Subtract the modular multilevel converter MMC DC side current command value I dc_ord minus the modular multilevel converter MMC DC side current measured value I dc , get the error, and then signalize it to get modular Multi-level converter MMC AC side current active axis component reference value I dref ; the signal processing method is proportional integral adjustment;

3) The modular multi-level converter MMC reactive power command value Q ord is subtracted from the measured value Q of the reactive power, and the error is obtained. After the signal processing, the modular multi-level converter MMC AC side output is obtained. The current reactive power component reference value I qref ; the signal processing method is proportional integral adjustment; wherein the reactive power command value Q ord is manually set or the controller calculates according to the design logic, and the reactive power measured value Q is calculated based on the modular multilevel converter MMC connected reactor Ls grid side voltages (u sa , u sb and u sc ) and currents (i a , i b and i c );

4) The modular multilevel converter MMC AC side currents i a , i b and i c are Park transformed, that is, multiplied by the transformation matrix P abc / dq to obtain the AC side current active axis component measured value i d and the measured value of the reactive axis component i q ;

The modular multilevel converter MMC is connected to the reactor Ls network side three-phase voltages u sa , u sb and u sc for Park transformation, that is, multiplied by the transformation matrix P abc / dq to obtain the connected reactor Ls network The measured value of the active voltage component of the side voltage u sd and the measured value of the reactive power component u sq ;

Wherein, the transformation matrix P abc/dq is in the form

Where θ = ω 0 t, ω 0 is the fundamental frequency of the grid, and t is time.

5) Subtract the measured value of the current active axis component by subtracting the measured value i d from the MMC AC side active active component reference value I dref of the modular multilevel converter, and subtracting the feedforward amount ω 0 Li after signal processing q , then subtract the measured value u sd of the active-axis component of the Ls grid side of the connected reactor, and obtain the reference value u cd_ref of the active side component of the MMC AC side of the modular multilevel converter; the signal processing method is proportional integral adjustment The modular multi-level converter MMC AC side current reactive axis component reference value I qref is subtracted from the measured value i q to obtain the current reactive axis component error value, and the signal processing is followed by the feedforward amount ω 0 Li d , plus the measured value of the voltage reactive component, u sq , obtains the modular multilevel converter MMC AC side voltage reactive component reference value u cq_ref ; the signal processing method is proportional integral adjustment;

The L is an equivalent AC network side reactance, which is 1/2 of the bridge arm reactance L c plus the connection reactance L s , that is,

6) Performing Park inverse transformation, ie multiplication by transformation matrix, of the modular multilevel converter MMC AC side voltage active axis component reference value u cd_ref and voltage reactive power component reference value u cq_ref
Obtaining the MMC AC side three-phase voltage reference values u ca_ref , u cb_ref and u cc_ref of the modular multilevel converter ; wherein, the transformation matrix
In the form of

7) Subtract the a-phase bridge arm reference voltage compensation amount U compa_ref for loop suppression with 1/2 of the modular multilevel converter MMC DC side voltage reference U dc — ref , and subtract the modular multi-level swap The current-side voltage a phase reference value u ca_ref of the current collector MMC is obtained, and the reference value u pa_ref of the bridge arm voltage on the a-phase is obtained ; and the a-phase bridge arm reference for loop suppression is subtracted by 1/2 of the DC-side voltage reference value U dc_ref voltage compensation amount U compb_ref, minus modular multilevel converter MMC phase AC side voltage of the reference value b u cb_ref, to give the b-phase voltage reference values arm u pb_ref; DC side voltage of the reference value U dc_ref 1/2 minus the a-phase bridge arm reference voltage compensation amount U compc_ref for the loop suppression, and subtracting the modular multi-level converter MMC AC side voltage c-phase reference value u cc_ref to obtain the c-phase upper arm voltage Reference value u pc_ref ; subtract the a-phase bridge arm reference voltage compensation amount U compa_ref for loop suppression with 1/2 of the modular multilevel converter MMC DC side voltage reference U dc — ref , plus modularity Multi-level converter MMC AC side voltage a phase reference value u ca_ref , get a phase lower arm U na_ref reference voltage; DC-side voltage reference U dc_ref 1/2 subtracting the b-phase arm suppress circulating reference voltage compensation amount U compb_ref, together with the multi-level modular MMC AC converter The side voltage b phase reference value u cb_re f, the reference value u nb_ref of the b-phase lower arm voltage is obtained ; the c-phase bridge arm reference voltage compensation amount for the loop suppression is subtracted by 1/2 of the DC side voltage reference value U dc_ref U compc_ref, plus modular multilevel converter MMC phase AC side voltage of the reference value c u cc_ref, to obtain the reference value c of the lower arm voltage u nc_ref;

Wherein, the loop suppression uses the double-fundamental frequency negative sequence rotation coordinates to detect the detected multi-level inverter MMC upper and lower arm currents i pa , i pb , i pc , i na , i nb and i nc . After processing, the bridge arm reference voltage compensation amounts U compa_ref , U compb_ref and U compc_ref for loop suppression are obtained by the proportional integrator and feedforward compensation;

8) The obtained modular multilevel converter MMC upper and lower arm voltage reference values u pa_ref , u pb_ref , u pc — ref , u na — ref , u nb — ref and u nc — ref are controlled by a pulse width modulation method to generate corresponding trigger pulses The turn-on and turn-off of the full-control device in each sub-module on the bridge arm enables the actual value of the bridge arm voltage to be the same as the bridge arm voltage reference value, thereby realizing the control of the voltage of each bridge arm;

Static Synchronous Compensation When in the DC side open circuit pressurization test mode, the following control steps are included:

1) Subtract the modular multilevel converter MMC DC side voltage command value U dc_ord minus the modular multilevel converter MMC DC side voltage measured value U dc to obtain the error, and then signalize it to obtain modularity. Multi-level converter MMC AC side current active axis component reference value I dref ; the signal processing method is proportional integral adjustment;

2) The modular multilevel converter MMC AC side currents i a , i b and i c are Park-transformed, that is, multiplied by the transformation matrix P abc/dq to obtain the measured value of the AC active current component of the AC side. d and the measured value of the reactive axis component i q ;

The modular multilevel converter MMC is connected to the reactor Ls network side three-phase voltages u sa , u sb and u sc for Park transformation, that is, multiplied by the transformation matrix P abc / dq to obtain the connected reactor Ls network The measured value of the active voltage component of the side voltage u sd and the measured value of the reactive power component u sq ;

3) Subtract the measured value of the current active axis component by subtracting the measured value i d from the MMC AC side active active component reference value I dref of the modular multilevel converter, and subtracting the feedforward amount ω 0 Li after signal processing q , then subtract the measured value u sd of the active-axis component of the Ls grid side of the connected reactor, and obtain the reference value u cd_ref of the active side component of the MMC AC side of the modular multilevel converter; the signal processing method is proportional integral adjustment In the DC side open circuit pressurization test mode, set the reference value I qref of the AC side current reactive power component of the modular multilevel converter MMC to zero, and subtract the measured value i q to obtain the current reactive power axis. The component error value, after signal processing, plus the feedforward amount ω 0 Li d , plus the measured value of the voltage reactive power component u sq , the modular multilevel converter MMC AC side voltage reactive power component Reference value u cq_ref ; the signal processing method is proportional integral adjustment;

4) Performing Park inverse transformation, ie multiplication by transformation matrix, of the modular multilevel converter MMC AC side voltage active axis component reference value u cd_ref and voltage reactive power component reference value u cq_ref
Obtaining the MMC AC side three-phase voltage reference values u ca_ref , u cb_ref and u cc_ref of the modular multilevel converter ;

5) Subtract the modular multilevel converter MMC AC side voltage a phase reference value u ca_ref with 1/2 of the modular multilevel converter MMC DC side voltage command value U dc_ord to obtain the a phase upper arm The reference value u pa_ref of the voltage is subtracted from the modulo multi-level converter MMC AC side voltage b phase reference value u cb_ref by 1/2 of the DC side voltage command value U dc_ord to obtain the reference value of the b-stage upper arm voltage u pb_ref; 1/2 subtracted value U dc_ord modular multilevel converter MMC phase AC side voltage of the reference value c u cc_ref, c to give the reference phase voltage values arm u pc_ref side DC voltage command;

Using the modular multilevel converter MMC DC side voltage command value U dc_ord 1/2 plus the modular multilevel converter MMC AC side voltage a phase reference value u ca_ref , to obtain the a phase lower arm voltage Reference value u na_ref ; plus 1/2 of the DC side voltage command value U dc_ord plus the modular multilevel converter MMC AC side voltage b phase reference value u cb_ref , to obtain the reference value of the b phase lower arm voltage u nb_ref Using the 1/2 of the DC side voltage command value U dc_ord plus the modular multilevel converter MMC AC side voltage c phase reference value u cc_ref , the reference value u nc_ref of the c-phase lower arm voltage is obtained ;

6) The obtained modular multilevel converter MMC upper and lower arm voltage reference values u pa_ref , u pb_ref , u pc_ref , u na_ref , u nb_ref and u nc_ref are controlled by a pulse width modulation method to generate a corresponding trigger pulse The turn-on and turn-off of the fully controlled device in each sub-module of the bridge arm enables the actual value of the bridge arm voltage to be the same as the bridge arm voltage reference value, thereby realizing the control of the voltage of each bridge arm.