A kind of distant-range high voltage direct current transmission transient overload testing method
Technical field
The present invention relates to a kind of distant-range high voltage direct current transmission transient overload testing method, belong to D.C. high voltage transmission (HVDC) field.
Background technology
High voltage dc transmission technology HVDC has obtained widespread use in electric system networking, formed direct current transportation and ac transmission cooperatively interacts in China, and constituted modern power systems thus.The wiring method of operation of general distant-range high voltage direct current transmission engineering has: the bipolar wiring method of operation, the big earthed return method of operation of one pole and the one pole metallic return method of operation; Under above-mentioned three kinds of modes of connection, all can one pole or bipolar step-down 80% and 70% operation respectively simultaneously.In the bipolar wiring method of operation, under the situation that the two poles of the earth working voltage equates, the DC current of DC engineering grounding electrode electric approaches 0, can not influence the DC engineering environment on the way and the normal operation of AC input transformation device.The final stage of high voltage direct current transmission project construction is the system debug of engineering, and the system debug test also is that last one technology before engineering puts into operation checked on.DC transmission engineering system debug pilot project has more than the hundreds of item, mainly is divided into two classes: a class pilot project is the pilot project of check straight-flow system secondary device performance; Another kind of is the pilot project of check direct current main equipment performance.The direct current transportation overload trial is exactly the pilot project of check direct current main equipment performance, and overload trial is divided into continuous overload, overload in 2 hours and transient overload (overload in short-term) test again.The test of the transient overload of DC engineering system debug in the past is to utilize bipolar large load operation, one utmost point emergency outage is realized an other utmost point transient overload, its result is the big earthed return operation of one pole, the electric current that flows through earthing pole is greater than rated direct current, and big ground current like this can influence DC line AC system substation transformer along the line and normally move; In addition, a utmost point emergency outage, DC power moment is transferred to the another one utmost point, converter valve to an other utmost point also produces bigger stress, in addition, and for the high-capacity direct current engineering, because it is bigger that moment loses the power of conveying, also can produce certain influence for the stable operation of AC system.This invention is utilized the DC bipolar rated load operation exactly, a utmost point step-down 70%, rated current operation, and DC power is transferred to another and is extremely realized the one pole transient overload, finishes the test of straight-flow system transient overload thus.So the inventor based on this, has obtained a kind of new distant-range high voltage direct current transmission transient overload testing method, finishes the present invention thus.
Summary of the invention
The technical issues that need to address of the present invention are AC system equipment not to be constituted under the influence, finish straight-flow system transient overload (overload in short-term) test.But remote high-capacity direct streaming system transient overload test in the past is to utilize DC bipolar high-power (or rated power operation) operation, one utmost point emergency outage, direct current transmission power moment is transferred to an other utmost point, because utmost point of direct current can not bear bipolar DC power, DC control system is limited to DC power moment on the transient overload power level, after several seconds, DC power is reduced to overload in 2 hours automatically, the straight-flow system operation is after 2 hours, and DC power is reduced to continuous overload power level automatically.The objective of the invention is by the bipolar rated load operation of straight-flow system, a utmost point step-down 70%, DC power is transferred to other one and is extremely realized another one utmost point transient overload.This test method has reduced the impact to DC converter valve, also can not produce bigger grounding electrode electric current thus and influences the normal operation of AC system substation transformer.
According to distant-range high voltage direct current transmission transient overload testing method of the present invention, may further comprise the steps:
(1), straight-flow system bipolar, utmost point I and utmost point II are with rated load operation;
(2), the DC voltage of the utmost point I of straight-flow system is reduced to 70% operation of one pole DC voltage rated power, DC current is a rated current, the transmission power that falls the utmost point I of DC voltage like this is 70% of an one pole rated power, the 30% one pole rated power that utmost point I loses will be transferred on another normal working voltage utmost point II, in very fast step-down process, the DC power of utmost point II will surpass the one pole rated power sum of one pole rated power and 30% moment, if the capability of overload that DC control calculates is equal to or less than one pole rated power, will produce transient overload at utmost point II so;
(3), if the capability of overload that DC control calculates is greater than the one pole rated power sum of one pole rated power and 30%, to can not produce transient overload, keep this method of operation a period of time, during this period, monitoring of environmental, valve hall, converter power transformer, the temperature of smoothing reactor, the overload level value of stipulating in the overload restricted software module in the contrast overloading control device, the temperature for the treatment of equipment or valve hall be increased to make utmost point II overload level drop to 1.25p.u. (one pole rated power and 25% one pole rated power sum) following after, utmost point I is reverted to normal voltage operation, the bipolar rated power operation that reverts to;
(4), once more utmost point I DC voltage is reduced to 70% operation of one pole DC voltage rated power, because utmost point II is in overload last time process, its capability of overload can not reach 1.3p.u. (one pole rated power and 30% one pole rated power sum) again, the capability of overload that DC control calculates necessarily is equal to or less than the one pole rated power sum of one pole rated power and 30%, and this time utmost point II will produce transient overload;
(5), the calculating of the overload time interval and capability of overload: in the direct current transportation design of Controller, the overload time interval and capability of overload are stipulated, during the direct current overload, current DC current and lasting overload restriction difference between currents are fed back to an integrator, when integrator begins the accumulative total difference between current, a counter begins counting, during gate time, the transient overload controller calculates the current limit value that is higher than the persistent current restriction, the transient overload restriction is based on the environment of measurement, valve hall, converter power transformer, the temperature of smoothing reactor, and whether redundant cooling capacity satisfies, after gate time finishes, integrator will stop integration and return then, integration numerical value will drop to 0, do not allow to carry out transient overload during this period, the capability of overload of the direct current utmost point will descend, and the restriction of output is reduced to and continued the overload value.Utmost point I rated power, step-down 70% operation, the 30% one pole rated power that utmost point I loses will be transferred on another normal working voltage utmost point II, if utmost point II can not produce transient overload, under this method of operation, move a period of time so, during this period, monitoring of environmental, valve hall, converter power transformer, the temperature of smoothing reactor, the overload level value of stipulating in the overload restricted software module in the contrast overloading control device, the temperature for the treatment of equipment or valve hall be increased to make utmost point II overload level drop to 1.25p.u. (one pole rated power and 25% one pole rated power sum) following after, utmost point I recovers normal pressure operation, bipolar recovery rated load operation.Then, carry out the utmost point I step-down second time 70%, the test of utmost point II transient overload, because the speed of utmost point I step-down is very fast, the DC power of moment shifts and will produce transient overload at utmost point II;
(6), direct current overload utmost point time of recovering 100% capability of overload how much deciding by the overload capacity that uses in the overload (comprising transient overload) of last time is between action period.
Below the electric current that flows through earthing pole during the direct current overload is described:
1, according to the method for carrying out the direct current transient overload in the past, one utmost point emergency outage is realized an other utmost point transient overload, its result is the big earthed return operation of one pole, grounding electrode electric current is greater than rated current, ground current greater than or can influence the AC system substation transformer near rated current and normally move;
2, if use high voltage direct current transmission transient overload testing method proposed by the invention, it is the bipolar rated load operation of straight-flow system, a utmost point step-down is 70% of an one pole DC voltage rated power, DC power is transferred to other one and is extremely realized another one utmost point transient overload, the electric current that flows through earthing pole deducts rated current for the overload electrode current, be 30% load current value, less than 1/3 of rated current, much smaller than carried out the electric current that direct current transient overload method flows through at earthing pole in the past, can not influence the AC system substation transformer normally moves, DC bipolar carries DC power not suffer a loss substantially simultaneously, has also reduced the impact to system stable operation.
The invention has the advantages that: remote, high capacity high voltage direct current transmission transient overload test is to be 70% of one pole DC voltage rated power by the bipolar rated load operation of straight-flow system, a utmost point step-down, and DC power is transferred to other one and extremely realized another one utmost point transient overload.This test method has reduced the impact to DC converter valve, also can not produce bigger grounding electrode electric current thus and influences the normal operation of AC system substation transformer, reduces the impact to system stable operation simultaneously.
Description of drawings
Referring to the following drawings, in the nonrestrictive one exemplary embodiment hereinafter, other features of the present invention and advantage will be conspicuous, and accompanying drawing is:
Fig. 1 is remote DC transmission engineering major loop wiring diagram;
Fig. 2 is the capability of overload parameter list of DC transmission engineering converter valve.
Embodiment
Referring to Fig. 1-2, the specified transmission power 3000MW of high voltage direct current transmission project, rated current 3000A, rated voltage ± 500kV.
Bipolar DC system major loop equipment (is example with the utmost point I of converting plant) and key property thereof with Fig. 1 is described below below:
0F1Q is a utmost point I DC converter valve;
011PB is a utmost point I smoothing reactor;
011B and 012B are the converter power transformer of utmost point I;
011LB and 012LB are the DC filter of utmost point I;
050127,050117,051107,001207 is valve Room ground connection disconnecting link;
05105 is utmost point I utmost point dc bus isolation switch;
051057 and 0510517 is utmost point I utmost point busbar grounding disconnecting link;
05121 is an isolation switch of utmost point II the earth/metallic return conversion operation, and 05122 is an isolation switch of utmost point I the earth/metallic return conversion operation, and 051217 is a ground connection disconnecting link of metallic return bus;
05111 and 00111 is the access disconnecting link of utmost point I DC filter (12/24 subharmonic), and 051117 and 001117 is the ground connection disconnecting link of utmost point I DC filter (12/24 subharmonic);
05112 and 00112 is the access disconnecting link of utmost point I DC filter (12/36 subharmonic), and 051127 and 001127 is the ground connection disconnecting link of utmost point I DC filter (12/36 subharmonic);
0010 is utmost point I neutral bus switch, and 001007 and 001037 is utmost point I neutral bus ground connection disconnecting link;
00102 is the isolation switch that utmost point I neutral bus and utmost point II neutral bus are isolated, and 00103 is an isolation switch of utmost point I neutral bus;
0030 transfers metallic return mode run switch to for the big earthed return mode of one pole;
0040 transfers big earthed return mode run switch to for one pole metallic return mode;
0060 is temporary grounding switch in the current conversion station.
Under the one pole metallic return method of operation, Inverter Station is passed through 0050 disconnecting link through the earth polar line-to-ground of inversion side joint.
Utmost point II is identical with the equipment disposition of utmost point I, no longer repeats at this; The equipment of Inverter Station and the equipment of converting plant are also basic identical, also repeat no more at this.
Send outside in the DC transmission engineering system debug process at Three Gorges Power, carry out the test of direct current one pole transient overload in the system debug test, experience according to DC engineering system debug in the past, the test of one pole transient overload is to utilize bipolar large load operation, one utmost point emergency outage is realized an other utmost point transient overload, its result is the big earthed return operation of one pole, and electric current is greater than 3000A.And can influencing the AC system substation transformer greater than 3000A, ground current normally moves; In addition, a utmost point emergency outage, DC power moment is transferred to the another one utmost point, and the converter valve of an other utmost point is also produced bigger stress.So the inventor utilizes method of the present invention, take bipolar rated load 3000MW operation, control utmost point II brownout operation a period of time earlier, running overload a period of time of utmost point I, utmost point I capability of overload can not reach 1.3p.u. (1950MW), it is to pass through environment temperature that its capability of overload of DC control calculates, converter valve, the change of current becomes, the capability of overload of smoothing reactor and change of current change sleeve pipe and the capacity of redundant cooling draw, then, control utmost point II recovers the normal voltage operation, at this moment, the capability of overload of utmost point I is limited in continuous overload power level, then control utmost point II once more step-down be 70% of one pole DC voltage rated power, rated current 3000A operation, power is the 1050MW operation, utmost point I overload, transmission power 1705MW, and started transient overload, finished the test of direct current one pole transient overload.
The present invention has been described according to preferred embodiment.Obviously, reading and understanding above-mentioned detailed description postscript and can make multiple correction and replacement.What this invention is intended to is that the application is built into all these corrections and the replacement that has comprised within the scope that falls into the appended claims or its equivalent.