CN114336668B - Converter transformer tap control method considering allowance voltage regulation of reactive compensation device - Google Patents

Abstract

The invention discloses a converter transformer tap control method considering both allowance voltage regulation of a reactive compensation device, and relates to the technical field of on-load voltage regulation switch tap control of a rectifier transformer of an extra-high voltage direct current transmission system. The invention solves the problems of frequent tap actions and low utilization rate of a reactive compensation device in the fixed angle control strategy of the on-load voltage regulating switch of the traditional converter transformer. According to the control method, the voltage regulation starting conditions of the alternating current filter, the parallel capacitor and the piezoelectric reactor are added in the original tap operation conditions, when the alternating current bus fluctuates beyond the rated range, the corresponding reactive compensation device is preferably selected to be switched on and off according to the difference of the excess quantity so as to balance the voltage, then the tap is utilized for bit filling and voltage regulation, the tap operation times are effectively reduced, and the utilization efficiency of the reactive compensation device is improved. The method is suitable for the technical field of rectification side converter transformer tap control under the fixed-power operation condition of the extra-high voltage direct current transmission system, and has good economical efficiency and applicability.

Description

Converter transformer tap control method considering allowance voltage regulation of reactive compensation device

Technical Field

The invention relates to the technical field of tap control of an on-load voltage regulating switch of a rectifier station converter transformer of an extra-high voltage direct current transmission system, in particular to a converter transformer tap control method considering allowance voltage regulation of a reactive compensation device.

Background

The reactive compensation device in the high-voltage direct-current transmission system comprises an alternating current filter and a piezoelectric reactor. The alternating current filter is mainly used for meeting reactive interaction requirements of a direct current system, filtering corresponding times of harmonic waves and adjusting alternating current bus voltage. The control process is realized by a reactive power control module integrated in a station-side control system. The ac overvoltage control, the absolute minimum filter bank control, the voltage limitation, the reactive power limitation, the minimum filter bank control, and the reactive power/voltage control are classified according to the difference of priorities. The minimum filter bank control is used for meeting the filtering requirement of the alternating current system, and the absolute minimum filter bank control is used for preventing the filter from being overloaded. The reactive power control core aims to ensure reactive power balance of an alternating current/direct current system, and the voltage control core aims to prevent overvoltage of an alternating current bus and prevent deterioration of voltage quality of the alternating current bus caused by filter switching. The voltage reactor has the functions of reactive power balance and voltage regulation and is used as the supplement of an alternating current filter. The tap control of the converter transformer in the HVDC system is matched with the controller of the converter, and when the trigger angle or DC voltage of the converter control is out of limit, the tap control of the converter transformer is utilized to adjust the controlled index to return to the controllable interval. The external tap is also affected by the amplitude limitation of the no-load direct-current voltage, and is superior to the conventional tap control, and the main purpose of the external tap is to prevent the equipment from being subjected to excessive steady-state voltage stress.

At present, in a high-voltage direct-current transmission system in operation, the condition of long-term non-full-load operation exists, the maximum direct-current transmission power of the system is generally not more than 80% of rated power, and reactive power demand generally accounts for 30-50% of active transmission power, so that the reactive power compensation device is not fully utilized, and a phenomenon that a large amount of reactive power compensation equipment is idle exists. The constant-angle control strategy is adopted for the converter transformer tap of the rectifying station, and the strategy has good dynamic response capability, but can cause frequent actions of the tap, so that hidden danger of frequent faults of mechanical transmission equipment and communication devices is brought, and the defect of the converter transformer tap often needs the matching of main equipment and power failure, so that the maintenance cost is increased, and the safety risk of personal equipment is increased. Therefore, an improvement is required to be provided for the existing tap control strategy, so that the tap action times are further reduced, and meanwhile, the utilization efficiency of the station-side reactive power compensation device is improved.

Disclosure of Invention

The invention provides a converter transformer tap control method considering allowance voltage regulation of a reactive power compensation device in order to solve the problems of frequent tap actions and low utilization rate of the reactive power compensation device in a fixed angle control strategy of a traditional converter transformer on-load voltage regulation switch.

The invention is realized by the following technical scheme: a converter transformer tap control method taking account of allowance voltage regulation of a reactive compensation device comprises the following steps:

step 1, determining a boundary value of alternating current bus voltage when a trigger angle of a rectifying station fluctuates in a dead zone range, considering a fixed power operation condition, wherein the direct current voltage is a rated value:

the rectification side expression of the HVDC transmission system is as follows:

wherein VdR is rectifying side DC voltage, τ is six pulse converter valve number, vdioR is rectifying side no-load DCVoltage, xr is commutation reactance, U ₁ For primary-side ac voltage of converter transformer, i.e. ac busbar voltage, tn is tap actual gear, T _N For tap rated gear, deltaU is the gear shift, eta _N Setting a transformation ratio for the converter transformer;

under the constant power operation condition, the direct current voltage VdR at the rectifying side is unchanged, the direct current Id is a constant value, the VdioR is a constant value, if the trigger angle alpha fluctuates within the dead zone range, the tap voltage regulation can not be started, and the U is at the moment ₁ * cos α remains constant, the margin of the trigger angle α offset rating is 2.5 °, the boundary value expression of the ac bus voltage is:

U _1min cos(α _N -2.5)＝U _1max cos(α _N +2.5)＝U _1N cosα _N (3)

wherein U is _1N Rated for AC bus voltage, U _1min 、U _1max The minimum and maximum values of the alternating current bus voltage are respectively obtained when the triggering angle of the rectifying station fluctuates in the dead zone range; alpha _N Is the firing angle rating;

step 2, obtaining a voltage regulation starting fixed value of the piezoelectric reactor: u (U) _{1max_LVR} 、U _{1min_LVR} The method comprises the steps of carrying out a first treatment on the surface of the Wherein U is _{1max_LVR} 、U _{1min_LVR} The voltage limit value of the alternating current bus for starting the input and the withdrawal of the low-voltage reactor is respectively shown;

according to the on-site operation regulations of the converter station, when the DC locking operation is performed, the 'participating in the voltage control of the converter bus' is adopted by the piezoelectric reactor, and when the voltage of the AC bus is higher than U _{1max_LVR} A group of voltage reactors are put into time delay; when the voltage of the alternating current bus is lower than U _{1min_LVR} When in time, a group of voltage reactors are cut off in a delayed manner;

step 3, acquiring an alternating current filter starting constant value: u (U) _{1max_LIMIT} 、U _{1max_LIM_ENBL} 、U _{1min_LIM_ENBL} 、U _{1min_LIMIT} The method comprises the steps of carrying out a first treatment on the surface of the Wherein U is _{1max_LIMIT} 、U _{1min_LIMIT} Respectively representing the voltage limit value of an alternating current bus for starting the cutting or input of the alternating current filter; u (U) _{1max_LIM_ENBL} 、U _{1min_LIM_ENBL} Respectively show that the input and the cut of the alternating current filter are forbiddenDividing the voltage limit value of the alternating current bus;

according to the current-station field operation regulations, when the voltage exceeds the maximum limit U _{1max_LIMIT} When the reactive power control cuts off the filter bank in order, the voltage is prevented from rising continuously; if the voltage is below the minimum limit U _{1min_LIMIT} When the reactive power control is carried out, the reactive power control is also put into the filter bank in sequence to prevent the voltage from continuously decreasing; if a filter is put into operation, the voltage will exceed U _{1max_LIM_ENBL} Inhibiting the operation of putting into the filter bank; similarly, if there is more filter cut out, the voltage will be lower than U _{1min_LIM_ENBL} The operation of the cut filter bank will be disabled;

step 4, determining the allowance of the reactive compensation device; according to the on-site reactive power exchange control strategy, certain deviation exists between the actual reactive power exchange and the planned reactive power exchange of the AC/DC system, if the reactive power exchange exceeds the deviation limit value, an AC filter is put into or cut off, and the following formula is satisfied:

wherein Q is reactive exchange quantity of the converter station and the alternating current system, Q _ref Reference value, Q, set for operation and maintenance personnel _dz The dead zone is switched; in general, Q _ref Set to zero, to ensure that the standby AC filter can participate in voltage regulation, Q _ref Taking the average value of rated power capacity of the reactive power group;

ac filter margin n _{_ACF} Selecting: when the total number of ac filter configurations minus the total number of operations is greater than 1, n _{_ACF} Taking 1, otherwise taking 0;

margin n of parallel capacitor _{_SC} Selecting: when the total number of parallel capacitor configurations minus the total number of operations is greater than 1, n _{_SC} Taking 1, otherwise taking 0;

margin n of piezoresistor _{_LVR} Selecting: when the total number of low-voltage reactor configurations minus the total number of operations is greater than 1, n _{_LVR} Taking 1, otherwise taking 0;

step 5, determining a reactive compensation device participating in margin voltage regulation, wherein in order to reduce interference to the existing reactive balance control strategy, and the margin conditions and the voltage starting conditions are met, when an alternating current bus is in overvoltage operation, the last reactive group which is put into in the switching sequence is selected by the alternating current filter or the parallel capacitor participating in margin voltage regulation; when the alternating current bus runs under the undervoltage, an alternating current filter or a parallel capacitor participating in margin voltage regulation selects the last reactive power group which is not put into in the switching sequence; the low-voltage resistors participating in margin voltage regulation are selected randomly by taking the aim of balancing the low-voltage resistors under the condition of changing two contacts as much as possible;

step 6, executing a control strategy:

(1) When U is _1min ≤U ₁ ≤U _1max When the voltage fluctuation of the balanced alternating current bus is controlled by the trigger angle alpha, the converter transformer tap and the reactive compensation device participating in voltage regulation do not act;

(2) When U is _1max ＜U ₁ ≤U _{1max_LVR} When the trigger angle just exceeds the upper limit, the tap enters a waiting period, and if the voltage of the alternating current bus continues to rise, a voltage regulating program is started;

(3) When U is _{1max_LVR} ＜U ₁ ≤U _{1max_LIM_ENBL} When the voltage reactor allowance n is preferentially judged _{_LVR} If the voltage is 1, starting a low-voltage-resistance voltage regulator, and putting into a voltage-resistance reactor participating in margin voltage regulation; if the investment is low, U ₁ Is still greater than U _1max Starting tap voltage regulation; if n _{_LVR} If the voltage is 0, directly starting tap voltage regulation; after overvoltage recovery, the margin n of the piezoresistor is preferentially judged _{_LVR} If the voltage is 1, cutting off the piezoresistors participating in allowance voltage regulation if the voltage is 1; if n _{_LVR} If the voltage is 0, directly starting tap voltage regulation;

(4) When U is _{1max_LIM_ENBL} ＜U ₁ ≤U _{1max_LIMIT} When the alternating current filter margin n is preferentially judged _{_ACF} If the voltage is 1, starting the alternating current filter to regulate the voltage, cutting off the alternating current filter participating in margin voltage regulation, if the voltage is 0 or after the alternating current filter is cut off, U ₁ Is still greater than U _1max Controlling according to the step 6 (3); after recovery of overvoltage, priority judgmentWhether the cut alternating current filter meets the discharge time requirement or not, and if so, putting the alternating current filter in; if not, controlling according to the step 6 (3);

(5) When U is ₁ ＞U _{1max_LIMIT} When the parallel capacitor margin n is preferentially judged _{_SC} If the voltage is 1, starting the voltage regulation of the parallel capacitor, cutting off the parallel capacitor participating in margin voltage regulation, if the voltage is 0 or after cutting off the parallel capacitor, U ₁ Is still greater than U _1max Controlling according to the step 6 (4); after the overvoltage is recovered, whether the cut parallel capacitor meets the discharge time requirement is preferentially judged, and if so, the parallel capacitor is put into; if not, controlling according to the step 6 (4);

(6) When U is _{1min_LVR} ≤U ₁ ＜U _1min When the trigger angle just crosses the lower limit, the tap enters a waiting period, and if the voltage of the alternating current bus is continuously reduced, a voltage regulating program is started;

(7) When U is _{1min_LIM_ENBL} ≤U ₁ ＜U _{1min_LVR} When the voltage reactor allowance n is preferentially judged _{_LVR} If the voltage is 1, starting low-voltage resistance voltage regulation, and cutting off the voltage resistors participating in margin voltage regulation; after low resistance to excision, U ₁ Is still smaller than U _1min Starting tap voltage regulation; if n _{_LVR} If the voltage is 0, directly starting tap voltage regulation; after the undervoltage is recovered, the margin n of the piezoresistor is preferentially judged _{_LVR} If the voltage is 1, inputting a voltage-resistance participating in margin voltage regulation if the voltage is 1; if n _{_LVR} If the voltage is 0, directly starting tap voltage regulation;

(8) When U is _{1min_LIMIT} ≤U ₁ ＜U _{1min_LIM_ENBL} When the alternating current filter margin n is preferentially judged _{_ACF} If it is 1, starting up AC filter to regulate voltage, adding AC filter participating in allowance voltage regulation, if it is 0 or after AC filter is put into, U ₁ Is still smaller than U _1min Controlling according to the step 6 (7); after the undervoltage is recovered, preferentially judging whether the input alternating current filter meets the interval time requirement, and if so, cutting off the alternating current filter; if not, refer to step 6(7) The strip is controlled;

(9) When U is ₁ ＜U _{1min_LIMIT} When the parallel capacitor margin n is preferentially judged _{_SC} If the voltage is 1, starting the voltage regulation of the parallel capacitor, and inputting the parallel capacitor participating in the margin voltage regulation, if the voltage is 0 or after the parallel capacitor is input, U ₁ Is still smaller than U _1min Controlling according to the step 6 (8); after the undervoltage is recovered, preferentially judging whether the input parallel capacitor meets the interval time requirement, and if so, cutting off the parallel capacitor; if not, control is performed with reference to step 6, item (8).

Compared with the prior art, the converter transformer tap control method taking account of allowance voltage regulation of the reactive power compensation device has the advantages that: (1) The tap action times can be effectively reduced, the mechanical life aging speed of the transmission mechanism and the failure rate of the communication and control system caused by frequent tap actions are reduced, and the power failure of the main equipment matched with the on-load voltage regulating device caused by overhauling is reduced. (2) The utilization efficiency of the existing reactive power compensation device is improved, and the problem that the reactive power compensation device of the converter station is idle for a long time is solved.

Drawings

FIG. 1 is a starting voltage distribution diagram used in a converter transformer tap control method for balancing margin voltage regulation of a reactive compensation device;

fig. 2 is a block diagram of converter transformer tap control taking account of margin voltage regulation of a reactive power compensation device.

Detailed Description

The invention is further described below with reference to specific examples and figures of the specification.

The converter transformer tap control method taking a certain converter station as an example for considering allowance voltage regulation of the reactive power compensation device in the embodiment comprises the following steps:

step 1, determining a boundary value of alternating current bus voltage when a trigger angle of a rectifying station fluctuates in a dead zone range, considering a fixed power operation condition, wherein the direct current voltage is a rated value:

the rectification side expression of the HVDC transmission system is as follows:

wherein VdR is rectifying side DC voltage, τ is six pulse converter valve number, vdioR is rectifying side no-load DC voltage, xr is commutation reactance, U ₁ For primary-side ac voltage of converter transformer, i.e. ac busbar voltage, tn is tap actual gear, T _N For tap rated gear, deltaU is the gear shift, eta _N Setting a transformation ratio for the converter transformer;

under the constant power operation condition, the direct current voltage VdR at the rectifying side is unchanged, the direct current Id is a constant value, the VdioR is a constant value, if the trigger angle alpha fluctuates within the dead zone range, the tap voltage regulation can not be started, and the U is at the moment ₁ * cos α remains constant, the margin of the trigger angle α offset rating is 2.5 °, the boundary value expression of the ac bus voltage is:

U _1min cos(α _N -2.5)＝U _1max cos(α _N +2.5)＝U _1N cosα _N (3)

wherein U is _1N Rated for AC bus voltage, U _1N ＝530kV，α _N For the firing angle setpoint value, α _N ＝15°；U _1min 、U _1max The minimum and maximum values of the alternating current bus voltage when the trigger angle of the rectification station fluctuates in the dead zone range are respectively, U _1min 、U _1max 524kV and 536.8kV respectively;

step 2, obtaining a voltage regulation starting fixed value of the piezoelectric reactor: u (U) _{1max_LVR} 、U _{1min_LVR} The method comprises the steps of carrying out a first treatment on the surface of the Wherein U is _{1max_LVR} 、U _{1min_LVR} The voltage limit value of the alternating current bus for starting the input and the withdrawal of the low-voltage reactor is respectively shown;

according to the on-site operation regulations of the converter station, direct currentWhen the locking operation is performed, the low-voltage reactor adopts a mode of participating in the voltage control of the converter bus, and when the voltage of the alternating-current bus is higher than U _{1max_LVR} A group of voltage reactors are put into time delay; when the voltage of the alternating current bus is lower than U _{1min_LVR} When in time, a group of voltage reactors are cut off in a delayed manner;

step 3, acquiring an alternating current filter starting constant value: u (U) _{1max_LIMIT} 、U _{1max_LIM_ENBL} 、U _{1min_LIM_ENBL} 、U _{1min_LIMIT} The method comprises the steps of carrying out a first treatment on the surface of the Wherein U is _{1max_LIMIT} 、U _{1min_LIMIT} Respectively representing the voltage limit value of an alternating current bus for starting the cutting or input of the alternating current filter; u (U) _{1max_LIM_ENBL} 、U _{1min_LIM_ENBL} Respectively representing the voltage limit value of the alternating current bus for prohibiting the input and the cutting of the alternating current filter; u according to the on-site operation regulations of the converter station _{1max_LIMIT} 550kV, U _{1max_LIM_ENBL} At 542kV, U _{1min_LIM_ENBL} Is 510kV, U _{1min_LIMIT} 500kV;

according to the current-station field operation regulations, when the voltage exceeds the maximum limit U _{1max_LIMIT} When the reactive power control cuts off the filter bank in order, the voltage is prevented from rising continuously; if the voltage is below the minimum limit U _{1min_LIMIT} When the reactive power control is carried out, the reactive power control is also put into the filter bank in sequence to prevent the voltage from continuously decreasing; if a filter is put into operation, the voltage will exceed U _{1max_LIM_ENBL} Inhibiting the operation of putting into the filter bank; similarly, if there is more filter cut out, the voltage will be lower than U _{1min_LIM_ENBL} The operation of the cut filter bank will be disabled;

step 4, determining the allowance of the reactive compensation device; according to the on-site reactive power exchange control strategy, certain deviation exists between the actual reactive power exchange and the planned reactive power exchange of the AC/DC system, if the reactive power exchange exceeds the deviation limit value, an AC filter is put into or cut off, and the following formula is satisfied:

wherein Q is reactive exchange quantity of the converter station and the alternating current system，Q _ref Taking 310MVar as a reference value set for operation and maintenance personnel; for AC filters, Q _dz For switching dead zones, 220MVar is taken; for AC filters, Q _dz Taking 280MVar for switching dead zones; in general, Q _ref Set to zero, to ensure that the standby AC filter can participate in voltage regulation, Q _ref Taking the average value of rated power capacity of the reactive power group;

ac filter margin n _{_ACF} Selecting: when the total number of ac filter configurations minus the total number of operations is greater than 1, n _{_ACF} Taking 1, otherwise taking 0;

margin n of parallel capacitor _{_SC} Selecting: when the total number of parallel capacitor configurations minus the total number of operations is greater than 1, n _{_SC} Taking 1, otherwise taking 0;

margin n of piezoresistor _{_LVR} Selecting: when the total number of low-voltage reactor configurations minus the total number of operations is greater than 1, n _{_LVR} Taking 1, otherwise taking 0;

step 5, determining a reactive compensation device participating in margin voltage regulation, wherein in order to reduce interference to the existing reactive balance control strategy, and the margin conditions and the voltage starting conditions are met, when an alternating current bus is in overvoltage operation, the last reactive group which is put into in the switching sequence is selected by the alternating current filter or the parallel capacitor participating in margin voltage regulation; when the alternating current bus runs under the undervoltage, an alternating current filter or a parallel capacitor participating in margin voltage regulation selects the last reactive power group which is not put into in the switching sequence; the low-voltage resistors participating in margin voltage regulation are selected randomly by taking the aim of balancing the low-voltage resistors under the condition of changing two contacts as much as possible;

step 6, executing a control strategy:

(1) When 524kV is less than or equal to U ₁ When the voltage is less than or equal to 536.8kV, the trigger angle alpha controls the balance alternating current bus voltage fluctuation, and the converter transformer tap and the reactive power compensation device participating in voltage regulation do not act;

(2) When 536.8kV < U ₁ When the trigger angle is less than or equal to 537kV, the tap enters a waiting period just beyond the upper limit, and if the voltage of the alternating current bus continues to rise, a voltage regulating program is started;

(3) When 537kV < U ₁ When less than or equal to 542kV, give priority toJudging margin n of low-voltage reactor _{_LVR} If the voltage is 1, starting a low-voltage-resistance voltage regulator, and putting into a voltage-resistance reactor participating in margin voltage regulation; if the investment is low, U ₁ Is still greater than U _1max Starting tap voltage regulation; if n _{_LVR} If the voltage is 0, directly starting tap voltage regulation; after overvoltage recovery, the margin n of the piezoresistor is preferentially judged _{_LVR} If the voltage is 1, cutting off the piezoresistors participating in allowance voltage regulation if the voltage is 1; if n _{_LVR} If the voltage is 0, directly starting tap voltage regulation;

(4) When 542kV is less than U ₁ When the voltage is less than or equal to 550kV, the margin n of the alternating current filter is preferentially judged _{_ACF} If the voltage is 1, starting the alternating current filter to regulate the voltage, cutting off the alternating current filter participating in margin voltage regulation, if the voltage is 0 or after the alternating current filter is cut off, U ₁ Is still greater than U _1max Controlling according to the step 6 (3); after the overvoltage is recovered, preferentially judging whether the cut alternating current filter meets the discharge time requirement, and if so, putting the alternating current filter in; if not, controlling according to the step 6 (3);

(5) When U is ₁ When the voltage is more than 550kV, the margin n of the parallel capacitor is preferentially judged _{_SC} If the voltage is 1, starting the voltage regulation of the parallel capacitor, cutting off the parallel capacitor participating in margin voltage regulation, if the voltage is 0 or after cutting off the parallel capacitor, U ₁ Still greater than 536.8kV, then controlling with reference to step 6, item (4); after the overvoltage is recovered, whether the cut parallel capacitor meets the discharge time requirement is preferentially judged, and if so, the parallel capacitor is put into; if not, controlling according to the step 6 (4);

(6) When 523kV is less than or equal to U ₁ When the trigger angle is smaller than 524kV, the tap enters a waiting period just beyond the lower limit, and if the voltage of the alternating current bus is continuously reduced, a voltage regulating program is started;

(7) When 510kV is less than or equal to U ₁ When the voltage is less than 523kV, the margin n of the piezoresistor is preferentially judged _{_LVR} If the voltage is 1, starting low-voltage resistance voltage regulation, and cutting off the voltage resistors participating in margin voltage regulation; after low resistance to excision, U ₁ Still less than 524kV, starting tap voltage regulation; if n _{_LVR} 0, then directly start the splitRegulating the pressure of the joint; after the undervoltage is recovered, the margin n of the piezoresistor is preferentially judged _{_LVR} If the voltage is 1, inputting a voltage-resistance participating in margin voltage regulation if the voltage is 1; if n _{_LVR} If the voltage is 0, directly starting tap voltage regulation;

(8) When 500kV is less than or equal to U ₁ When the voltage is less than 510kV, the margin n of the alternating current filter is preferentially judged _{_ACF} If it is 1, starting up AC filter to regulate voltage, adding AC filter participating in allowance voltage regulation, if it is 0 or after AC filter is put into, U ₁ Still less than 524kV, controlling according to the step 6, namely (7); after the undervoltage is recovered, preferentially judging whether the input alternating current filter meets the interval time requirement, and if so, cutting off the alternating current filter; if not, controlling according to the step 6, namely (7);

(9) When U is ₁ When the voltage is less than 500kV, the margin n of the parallel capacitor is preferentially judged _{_SC} If the voltage is 1, starting the voltage regulation of the parallel capacitor, and inputting the parallel capacitor participating in the margin voltage regulation, if the voltage is 0 or after the parallel capacitor is input, U ₁ Still less than 524kV, controlling according to the step 6, namely (8); after the undervoltage is recovered, preferentially judging whether the input parallel capacitor meets the interval time requirement, and if so, cutting off the parallel capacitor; if not, control is performed with reference to step 6, item (8).

The scope of the present invention is not limited to the above embodiments, and various modifications and alterations of the present invention will become apparent to those skilled in the art, and any modifications, improvements and equivalents within the spirit and principle of the present invention are intended to be included in the scope of the present invention.

Claims (1)

1. A converter transformer tap control method taking account of allowance voltage regulation of a reactive compensation device is characterized in that: the method comprises the following steps:

step 1, determining a boundary value of alternating current bus voltage when a trigger angle of a rectifying station fluctuates in a dead zone range, considering a fixed power operation condition, wherein the direct current voltage is a rated value:

the rectification side expression of the HVDC transmission system is as follows:

wherein VdR is rectifying side DC voltage, τ is six pulse converter valve number, vdioR is rectifying side no-load DC voltage, xr is commutation reactance, U ₁ For primary-side ac voltage of converter transformer, i.e. ac busbar voltage, tn is tap actual gear, T _N For tap rated gear, deltaU is the gear shift, eta _N Setting a transformation ratio for the converter transformer;

under the constant power operation condition, the direct current voltage VdR at the rectifying side is unchanged, the direct current Id is a constant value, the VdioR is a constant value, if the trigger angle alpha fluctuates within the dead zone range, the tap voltage regulation can not be started, and the U is at the moment ₁ * cos α remains constant, the margin of the trigger angle α offset rating is 2.5 °, the boundary value expression of the ac bus voltage is:

U _1min cos(α _N -2.5)＝U _1max cos(α _N +2.5)＝U _1N cosα _N (3)

wherein U is _1N Rated for AC bus voltage, U _1min 、U _1max The minimum and maximum values of the alternating current bus voltage are respectively obtained when the triggering angle of the rectifying station fluctuates in the dead zone range; alpha _N Is the firing angle rating;

step 2, obtaining a voltage regulation starting fixed value of the piezoelectric reactor: u (U) _{1max_LVR} 、U _{1min_LVR} The method comprises the steps of carrying out a first treatment on the surface of the Wherein U is _{1max_LVR} 、U _{1min_LVR} The voltage limit value of the alternating current bus for starting the input and the withdrawal of the low-voltage reactor is respectively shown;

according to the on-site operation regulations of the converter station, when the DC locking operation is performed, the 'participating in the voltage control of the converter bus' is adopted by the piezoelectric reactor, and when the voltage of the AC bus is higher than U _{1max_LVR} A group of voltage reactors are put into time delay; when the voltage of the alternating current bus is lower than U _{1min_LVR} When in time, a group of voltage reactors are cut off in a delayed manner;

step 3, acquiring an alternating current filter starting constant value: u (U) _{1max_LIMIT} 、U _{1max_LIM_ENBL} 、U _{1min_LIM_ENBL} 、U _{1min_LIMIT} The method comprises the steps of carrying out a first treatment on the surface of the Wherein U is _{1max_LIMIT} 、U _{1min_LIMIT} Respectively representing the voltage limit value of an alternating current bus for starting the cutting or input of the alternating current filter; u (U) _{1max_LIM_ENBL} 、U _{1min_LIM_ENBL} Respectively representing the voltage limit value of the alternating current bus for prohibiting the input and the cutting of the alternating current filter;

according to the current-station field operation regulations, when the voltage exceeds the maximum limit U _{1max_LIMIT} When the reactive power control cuts off the filter bank in order, the voltage is prevented from rising continuously; if the voltage is below the minimum limit U _{1min_LIMIT} When the reactive power control is carried out, the reactive power control is also put into the filter bank in sequence to prevent the voltage from continuously decreasing; if a filter is put into operation, the voltage will exceed U _{1max_LIM_ENBL} Inhibiting the operation of putting into the filter bank; similarly, if there is more filter cut out, the voltage will be lower than U _{1min_LIM_ENBL} The operation of the cut filter bank will be disabled;

step 4, determining the allowance of the reactive compensation device; according to the on-site reactive power exchange control strategy, certain deviation exists between the actual reactive power exchange and the planned reactive power exchange of the AC/DC system, if the reactive power exchange exceeds the deviation limit value, an AC filter is put into or cut off, and the following formula is satisfied:

wherein Q is reactive exchange quantity of the converter station and the alternating current system, Q _ref Reference value, Q, set for operation and maintenance personnel _dz The dead zone is switched; in general, Q _ref Set to zero, to ensure that the standby AC filter can participate in voltage regulation, Q _ref Taking the average value of rated power capacity of the reactive power group;

ac filter marginn _{_ACF} Selecting: when the total number of ac filter configurations minus the total number of operations is greater than 1, n _{_ACF} Taking 1, otherwise taking 0;

margin n of parallel capacitor _{_SC} Selecting: when the total number of parallel capacitor configurations minus the total number of operations is greater than 1, n _{_SC} Taking 1, otherwise taking 0;

margin n of piezoresistor _{_LVR} Selecting: when the total number of low-voltage reactor configurations minus the total number of operations is greater than 1, n _{_LVR} Taking 1, otherwise taking 0;

step 5, determining a reactive compensation device participating in margin voltage regulation, wherein in order to reduce interference to the existing reactive balance control strategy, and the margin conditions and the voltage starting conditions are met, when an alternating current bus is in overvoltage operation, the last reactive group which is put into in the switching sequence is selected by the alternating current filter or the parallel capacitor participating in margin voltage regulation; when the alternating current bus runs under the undervoltage, an alternating current filter or a parallel capacitor participating in margin voltage regulation selects the last reactive power group which is not put into in the switching sequence; the low-voltage resistors participating in margin voltage regulation are selected randomly by taking the aim of balancing the low-voltage resistors under the condition of changing two contacts as much as possible;

step 6, executing a control strategy:

(1) When U is _1min ≤U ₁ ≤U _1max When the voltage fluctuation of the balanced alternating current bus is controlled by the trigger angle alpha, the converter transformer tap and the reactive compensation device participating in voltage regulation do not act;

(2) When U is _1max ＜U ₁ ≤U _{1max_LVR} When the trigger angle just exceeds the upper limit, the tap enters a waiting period, and if the voltage of the alternating current bus continues to rise, a voltage regulating program is started;

(3) When U is _{1max_LVR} ＜U ₁ ≤U _{1max_LIM_ENBL} When the voltage reactor allowance n is preferentially judged _{_LVR} If the voltage is 1, starting a low-voltage-resistance voltage regulator, and putting into a voltage-resistance reactor participating in margin voltage regulation; if the investment is low, U ₁ Is still greater than U _1max Starting tap voltage regulation; if n _{_LVR} If the voltage is 0, directly starting tap voltage regulation; after overvoltage recovery, the margin n of the piezoresistor is preferentially judged _{_LVR} Whether or not to useIf the voltage is 1, cutting off the piezoresistors participating in allowance voltage regulation; if n _{_LVR} If the voltage is 0, directly starting tap voltage regulation;

(4) When U is _{1max_LIM_ENBL} ＜U ₁ ≤U _{1max_LIMIT} When the alternating current filter margin n is preferentially judged _{_ACF} If the voltage is 1, starting the alternating current filter to regulate the voltage, cutting off the alternating current filter participating in margin voltage regulation, if the voltage is 0 or after the alternating current filter is cut off, U ₁ Is still greater than U _1max Controlling according to the step 6 (3); after the overvoltage is recovered, preferentially judging whether the cut alternating current filter meets the discharge time requirement, and if so, putting the alternating current filter in; if not, controlling according to the step 6 (3);

(5) When U is ₁ ＞U _{1max_LIMIT} When the parallel capacitor margin n is preferentially judged _{_SC} If the voltage is 1, starting the voltage regulation of the parallel capacitor, cutting off the parallel capacitor participating in margin voltage regulation, if the voltage is 0 or after cutting off the parallel capacitor, U ₁ Is still greater than U _1max Controlling according to the step 6 (4); after the overvoltage is recovered, whether the cut parallel capacitor meets the discharge time requirement is preferentially judged, and if so, the parallel capacitor is put into; if not, controlling according to the step 6 (4);

(6) When U is _{1min_LVR} ≤U ₁ ＜U _1min When the trigger angle just crosses the lower limit, the tap enters a waiting period, and if the voltage of the alternating current bus is continuously reduced, a voltage regulating program is started;

(7) When U is _{1min_LIM_ENBL} ≤U ₁ ＜U _{1min_LVR} When the voltage reactor allowance n is preferentially judged _{_LVR} If the voltage is 1, starting low-voltage resistance voltage regulation, and cutting off the voltage resistors participating in margin voltage regulation; after low resistance to excision, U ₁ Is still smaller than U _1min Starting tap voltage regulation; if n _{_LVR} If the voltage is 0, directly starting tap voltage regulation; after the undervoltage is recovered, the margin n of the piezoresistor is preferentially judged _{_LVR} If the voltage is 1, inputting a voltage-resistance participating in margin voltage regulation if the voltage is 1; if n _{_LVR} If the voltage is 0, directly starting tap voltage regulation;

(8) When U is _{1min_LIMIT} ≤U ₁ ＜U _{1min_LIM_ENBL} When the alternating current filter margin n is preferentially judged _{_ACF} If it is 1, starting up AC filter to regulate voltage, adding AC filter participating in allowance voltage regulation, if it is 0 or after AC filter is put into, U ₁ Is still smaller than U _1min Controlling according to the step 6 (7); after the undervoltage is recovered, preferentially judging whether the input alternating current filter meets the interval time requirement, and if so, cutting off the alternating current filter; if not, controlling according to the step 6, namely (7);

(9) When U is ₁ ＜U _{1min_LIMIT} When the parallel capacitor margin n is preferentially judged _{_SC} If the voltage is 1, starting the voltage regulation of the parallel capacitor, and inputting the parallel capacitor participating in the margin voltage regulation, if the voltage is 0 or after the parallel capacitor is input, U ₁ Is still smaller than U _1min Controlling according to the step 6 (8); after the undervoltage is recovered, preferentially judging whether the input parallel capacitor meets the interval time requirement, and if so, cutting off the parallel capacitor; if not, control is performed with reference to step 6, item (8).

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