CN114336668A - Converter transformer tap control method considering reactive power compensation device margin voltage regulation - Google Patents

Abstract

The invention discloses a converter transformer tap control method considering both margin voltage regulation of a reactive power compensation device, and relates to the technical field of tap control of an on-load voltage regulation switch of a converter transformer of a rectification station of an extra-high voltage direct current transmission system. The invention solves the problems of frequent action of the tapping point and low utilization rate of the reactive power compensation device in the traditional angle-fixed control strategy of the on-load tap changer of the converter transformer. According to the control method, voltage regulation starting conditions of an alternating current filter, a parallel capacitor and a low-voltage reactor are added in the original tap action conditions, when an alternating current bus fluctuates beyond a rated range, corresponding reactive compensation devices are preferentially selected to be switched on and off to balance voltage according to different excess amounts, and then the tap is utilized to perform position compensation voltage regulation, so that the tap action times are effectively reduced, and the utilization efficiency of the reactive compensation devices is improved. The invention is suitable for the technical field of rectifier side converter transformer tap control under the constant power operation condition of the ultra-high voltage direct current transmission system, and has good economical efficiency and applicability.

Description

Converter transformer tap control method considering reactive power compensation device margin voltage regulation

Technical Field

The invention relates to the technical field of tap control of an on-load tap changer of a converter transformer of a rectifying station of an extra-high voltage direct current transmission system, in particular to a converter transformer tap control method giving consideration to the margin voltage regulation of a reactive compensation device.

Background

The reactive power compensation device in the high-voltage direct-current transmission system comprises an alternating-current filter and a low-voltage reactor. The alternating current filter is mainly used for meeting the reactive interaction requirement 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. According to the difference of priority, the method is divided into alternating current overvoltage control, absolute minimum filter bank control, voltage limitation, reactive power limitation, minimum filter bank control and reactive power/voltage control. The minimum filter bank control is to meet the filtering requirement of the alternating current system, and the absolute minimum filter bank control is to prevent the overload of the filter. The reactive power control core aims to ensure the reactive power balance of an alternating current and direct current system, and the voltage control core aims to prevent the overvoltage of an alternating current bus and prevent the quality deterioration of the alternating current bus voltage caused by the switching-on and switching-off of a filter. The low-voltage reactor has the functions of reactive power balance and voltage regulation and is used as a supplement of the alternating current filter. The tap control of the converter transformer in the high-voltage direct-current transmission system is matched with a controller of the converter, and when the trigger angle or the direct-current voltage controlled by the converter is out of limit, the tap of the converter transformer is used for adjusting the controlled index to return to the controllable interval. Its outer taps are also affected by the no-load dc voltage limiting, overriding conventional tap control, which is primarily intended to prevent the equipment from being subjected to excessive steady state voltage stress.

At present, the condition of long-term non-full load operation exists in a high-voltage direct-current power transmission system, the maximum direct-current transmission power generally does not exceed 80% of rated power, and reactive power requirements generally account for 30-50% of active transmission power, so that the reactive power compensation device is not fully utilized, and a large amount of reactive power compensation equipment is idle. The converter transformer tap of the rectifier station mostly adopts a fixed angle control strategy, the strategy has good dynamic response capability, but the tap can frequently act, so that the hidden trouble that faults of mechanical transmission equipment and communication devices frequently occur is brought, and the elimination of the converter transformer tap usually requires the cooperation of main equipment and power failure, so that the overhaul cost is increased, and the safety risk of personal equipment is increased. Therefore, there is a need to improve the existing tap control strategy to further reduce the tap action times and improve the utilization efficiency of the station-side reactive power compensation device.

Disclosure of Invention

The invention provides a converter transformer tap control method giving consideration to margin voltage regulation of a reactive compensation device, aiming at solving the problems of frequent action of a tap and low utilization rate of the reactive compensation device in a traditional converter transformer on-load voltage regulation switch fixed angle control strategy.

The invention is realized by the following technical scheme: a converter transformer tap control method giving consideration to margin 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 rectifier station fluctuates in a dead zone range, considering a constant-power operation condition, and taking direct current voltage as a rated value:

the expression of the rectification side of the high-voltage direct-current transmission system is as follows:

wherein VdR is direct-current voltage at the rectifying side, tau is the number of six-pulse converter valves, VdioR is no-load direct-current voltage at the rectifying side, Xr is phase-change reactance, U is₁Is the primary side alternating voltage of the converter transformer, namely the alternating bus voltage, Tn is the actual tap position, T_NFor the rated tap position, Δ U is the converter shift distance, η_NThe rated transformation ratio of the converter transformer is obtained;

under the operating condition of constant power, the direct current voltage VdR on the rectifying side is unchanged, the direct current Id is a constant value, the VdioR cos alpha is a constant value, if the trigger angle alpha fluctuates in the dead zone range, the tap joint cannot be started to regulate the voltage, and at the moment, U is regulated₁Cos α remains constant, the firing angle α is offset by a margin of 2.5 ° from the nominal value, and 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_1Ncosα_N (3)

wherein, U_1NRated for AC bus, U_1min、U_1maxThe minimum value and the maximum value of the alternating current bus voltage are respectively when the trigger angle of the rectifier station fluctuates in the dead zone range; alpha is alpha_NIs a firing angle rating;

step 2, obtaining a voltage regulating starting fixed value of the low-voltage reactor: u shape_{1max_LVR}、U_{1min_LVR}(ii) a Wherein U is_{1max_LVR}、U_{1min_LVR}Respectively representing the voltage limit values of the alternating-current bus for starting the low-voltage reactor to be switched in and out;

according to the field operation rule of the converter station, when the direct current is locked to operate, the low-voltage reactor adopts' participationCommutation bus voltage control mode when the AC bus voltage is higher than U_{1max_LVR}Time delay putting a group of voltage reactors; when the AC bus voltage is lower than U_{1min_LVR}Time delay cutting off a group of voltage reactors;

step 3, obtaining a starting fixed value of the alternating current filter: u shape_{1max_LIMIT}、U_{1max_LIM_ENBL}、U_{1min_LIM_ENBL}、U_{1min_LIMIT}(ii) a Wherein, U_{1max_LIMIT}、U_{1min_LIMIT}Respectively representing the voltage limit value of an alternating current bus for starting the cut-off or input of the alternating current filter; u shape_{1max_LIM_ENBL}、U_{1min_LIM_ENBL}Respectively representing the voltage limit values of the alternating current bus for prohibiting the input and the cut-off of the alternating current filter;

according to the field operation rule of the converter station, if the voltage exceeds the maximum amplitude limit U_{1max_LIMIT}When the voltage rises, the reactive power control cuts off the filter bank in sequence to prevent the voltage from rising continuously; if the voltage is below the lowest limit U_{1min_LIMIT}In time, reactive power control is also put into the filter bank in order to prevent the voltage from continuously reducing; if a further set of filters is applied, this will cause the voltage to exceed U_{1max_LIM_ENBL}Prohibiting the operation of the filter bank; similarly, if there is a further filter cut-off, this will cause the voltage to fall below U_{1min_LIM_ENBL}The operation of the cut-out filter bank will be disabled;

step 4, determining the allowance of the reactive power compensation device; according to a field reactive power exchange control strategy, a certain deviation exists between actual reactive power exchange and planned reactive power exchange of an alternating current-direct current system, if the reactive power exchange exceeds a deviation limit value, an alternating current filter is put in or cut off, and the following formula is met:

wherein Q is the reactive exchange quantity of the converter station and the alternating current system, Q_refReference value, Q, set for operation and maintenance personnel_dzIs a switching dead zone; in general, Q_refSet to zero, Q to ensure that a backup AC filter can participate in voltage regulation_refTaking rated power of reactive groupAverage value of capacity;

margin n of AC filter_{_ACF}Selecting: when the total number of the configuration of the alternating current filter minus the total number of the operation is more than 1, n_{_ACF}Taking 1, otherwise, taking 0;

parallel capacitor margin n_{_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;

low-voltage reactor margin n_{_LVR}Selecting: when the total configuration number minus the total operation number of the low-voltage reactor is more than 1, n_{_LVR}Taking 1, otherwise, taking 0;

step 5, determining a reactive power compensation device participating in margin voltage regulation, and when an alternating current bus is in overvoltage operation, selecting the last reactive power group which is put into a switching sequence by a margin voltage regulation alternating current filter or a parallel capacitor in order to reduce interference on the existing reactive power balance control strategy and meet a margin condition and a voltage starting condition; when the alternating current bus is in undervoltage operation, the alternating current filter or the parallel capacitor participating in margin voltage regulation selects the last reactive power group which is not put into the switching sequence; the low-voltage reactors participating in margin voltage regulation are randomly selected with the aim of balancing the low impedance of the two contact transformers as much as possible;

and 6, executing a control strategy:

(1) when U is turned_1min≤U₁≤U_1maxDuring the process, the voltage fluctuation of the balanced alternating-current bus is controlled by a trigger angle alpha, and the converter transformer tap and the reactive power compensation device participating in voltage regulation do not act;

(2) when U is turned_1max＜U₁≤U_{1max_LVR}When the trigger angle just exceeds the upper limit, the tap joint enters a waiting period, and if the voltage of the alternating current bus is continuously increased, a voltage regulating program is started;

(3) when U is turned_{1max_LVR}＜U₁≤U_{1max_LIM_ENBL}Firstly judging the allowance n of the low-voltage reactor_{_LVR}If the voltage is 1, starting low-voltage reactor voltage regulation and putting in a low-voltage reactor participating in margin voltage regulation; if the low resistance is added, U₁Is still greater than U_1maxStarting a tap to regulate the voltage; if n is_{_LVR}Is 0, then directly startsTap voltage regulation; after the overvoltage is recovered, the allowance n of the low-voltage reactor is judged preferentially_{_LVR}If the voltage is 1, cutting off the low-voltage reactor participating in margin voltage regulation; if n is_{_LVR}If the voltage is 0, the tap is directly started to regulate the voltage;

(4) when U is turned_{1max_LIM_ENBL}＜U₁≤U_{1max_LIMIT}When the AC filter is in operation, the margin n of the AC filter is determined with priority_{_ACF}If the voltage is 1, starting the AC filter to regulate the voltage, and cutting off the AC filter participating in margin voltage regulation, if the voltage is 0 or after the AC filter is cut off, U₁Is still greater than U_1maxThen, referring to item (3) of step 6, control is performed; after the overvoltage is recovered, preferentially judging whether the cut alternating current filter meets the requirement of discharging time, and if so, inputting the alternating current filter; if not, controlling with reference to item (3) in the step 6;

(5) when U is turned₁＞U_{1max_LIMIT}Firstly, the margin n of the parallel capacitor is judged_{_SC}If the voltage is 1, starting the parallel capacitor to regulate the voltage, cutting off the parallel capacitor participating in margin voltage regulation, if the voltage is 0 or after the parallel capacitor is cut off, U₁Is still greater than U_1maxThen, referring to item (4) of step 6, control is performed; after the overvoltage is recovered, preferentially judging whether the cut parallel capacitor meets the requirement of discharging time, and if so, putting the parallel capacitor into the overvoltage recovery circuit; if not, referring to the item (4) in the step 6 for control;

(6) when U is turned_{1min_LVR}≤U₁＜U_1minWhen the trigger angle just exceeds the lower limit, the tap joint 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 turned_{1min_LIM_ENBL}≤U₁＜U_{1min_LVR}Firstly judging the allowance n of the low-voltage reactor_{_LVR}If the voltage is 1, starting low-voltage reactor voltage regulation, and cutting off a low-voltage reactor participating in margin voltage regulation; if low resistance after excision, U₁Is still less than U_1minStarting a tap to regulate the voltage; if n is_{_LVR}If the voltage is 0, the tap is directly started to regulate the voltage; after the undervoltage is recovered, the allowance n of the low-voltage reactor is judged preferentially_{_LVR}If the value is 1, the participation margin is adjustedA low-voltage reactor for voltage; if n is_{_LVR}If the voltage is 0, the tap is directly started to regulate the voltage;

(8) when U is turned_{1min_LIMIT}≤U₁＜U_{1min_LIM_ENBL}When the AC filter is in operation, the margin n of the AC filter is determined with priority_{_ACF}If the voltage is 1, starting the AC filter to regulate the voltage, and putting the AC filter participating in margin voltage regulation, if the voltage is 0 or after the AC filter is put in, U₁Is still less than U_1minThen, referring to item (7) of step 6, performing control; 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, referring to the item (7) in the step 6 for control;

(9) when U is turned₁＜U_{1min_LIMIT}Firstly, the margin n of the parallel capacitor is judged_{_SC}If the voltage is 1, starting the parallel capacitor to regulate the voltage, and inputting the parallel capacitor participating in margin voltage regulation, if the voltage is 0 or after the parallel capacitor is input, U₁Is still less than U_1minThen, referring to item (8) of step 6, control is performed; after the undervoltage is recovered, preferentially judging whether the switched parallel capacitors meet the interval time requirement, and if so, cutting off the parallel capacitors; if not, the control is performed according to item (8) of step 6.

Compared with the prior art, the converter transformer tap control method considering both margin voltage regulation of the reactive power compensation device has the advantages and positive effects that: (1) the frequency of tap operation can be effectively reduced, the mechanical service life aging speed and the communication and control system failure rate of a transmission mechanism caused by frequent operation of the tap are reduced, and the main equipment coordination power failure caused by maintenance of the on-load voltage regulation device is reduced. (2) The utilization efficiency of the existing reactive power compensation device is improved, and the problem that part of reactive power compensation devices of the converter station are idle for a long time is solved.

Drawings

FIG. 1 is a starting voltage distribution diagram adopted by a converter transformer tap control method considering margin voltage regulation of a reactive power compensation device according to the present invention;

fig. 2 is a control block diagram of a converter transformer tap considering margin voltage regulation of a reactive power compensation device according to the present invention.

Detailed Description

The invention is further described with reference to the following detailed description and the accompanying drawings.

The converter transformer tap control method considering the margin voltage regulation of the reactive power compensation device in the embodiment takes a certain converter station as an example, and the method comprises the following steps:

step 1, determining a boundary value of alternating current bus voltage when a trigger angle of a rectifier station fluctuates in a dead zone range, considering a constant-power operation condition, and taking direct current voltage as a rated value:

the expression of the rectification side of the high-voltage direct-current transmission system is as follows:

wherein VdR is direct-current voltage at the rectifying side, tau is the number of six-pulse converter valves, VdioR is no-load direct-current voltage at the rectifying side, Xr is phase-change reactance, U is₁Is the primary side alternating voltage of the converter transformer, namely the alternating bus voltage, Tn is the actual tap position, T_NFor the rated tap position, Δ U is the converter shift distance, η_NThe rated transformation ratio of the converter transformer is obtained;

under the operating condition of constant power, the direct current voltage VdR on the rectifying side is unchanged, the direct current Id is a constant value, the VdioR cos alpha is a constant value, if the trigger angle alpha fluctuates in the dead zone range, the tap joint cannot be started to regulate the voltage, and at the moment, U is regulated₁Cos α remains constant, the firing angle α is offset by a margin of 2.5 ° from the nominal value, and 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_1Ncosα_N (3)

wherein, U_1NRating ac busVoltage, U_1N＝530kV，α_NFor firing angle rating, α_N＝15°；U_1min、U_1maxRespectively the minimum value and the maximum value of the alternating current bus voltage, U when the trigger angle of the rectifier station fluctuates in the dead zone range_1min、U_1max524kV and 536.8kV respectively;

step 2, obtaining a voltage regulating starting fixed value of the low-voltage reactor: u shape_{1max_LVR}、U_{1min_LVR}(ii) a Wherein U is_{1max_LVR}、U_{1min_LVR}Respectively representing the voltage limit values of the alternating-current bus for starting the low-voltage reactor to be switched in and out;

according to the field operation rule of the converter station, when the direct current is locked to operate, 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 that of the U bus_{1max_LVR}Time delay putting a group of voltage reactors; when the AC bus voltage is lower than U_{1min_LVR}Time delay cutting off a group of voltage reactors;

step 3, obtaining a starting fixed value of the alternating current filter: u shape_{1max_LIMIT}、U_{1max_LIM_ENBL}、U_{1min_LIM_ENBL}、U_{1min_LIMIT}(ii) a Wherein, U_{1max_LIMIT}、U_{1min_LIMIT}Respectively representing the voltage limit value of an alternating current bus for starting the cut-off or input of the alternating current filter; u shape_{1max_LIM_ENBL}、U_{1min_LIM_ENBL}Respectively representing the voltage limit values of the alternating current bus for prohibiting the input and the cut-off of the alternating current filter; according to the field operation regulations of the converter station, U_{1max_LIMIT}Is 550kV and U_{1max_LIM_ENBL}Is 542kV and U_{1min_LIM_ENBL}Is 510kV, U_{1min_LIMIT}Is 500 kV;

according to the field operation rule of the converter station, if the voltage exceeds the maximum amplitude limit U_{1max_LIMIT}When the voltage rises, the reactive power control cuts off the filter bank in sequence to prevent the voltage from rising continuously; if the voltage is below the lowest limit U_{1min_LIMIT}In time, reactive power control is also put into the filter bank in order to prevent the voltage from continuously reducing; if a further set of filters is applied, this will cause the voltage to exceed U_{1max_LIM_ENBL}Prohibiting the operation of the filter bank; similarly, if there is a further filter cut-off, this will cause the voltage to fall below U_{1min_LIM_ENBL}The operation of the cut-out filter bank will be disabled;

step 4, determining the allowance of the reactive power compensation device; according to a field reactive power exchange control strategy, a certain deviation exists between actual reactive power exchange and planned reactive power exchange of an alternating current-direct current system, if the reactive power exchange exceeds a deviation limit value, an alternating current filter is put in or cut off, and the following formula is met:

wherein Q is the reactive exchange quantity of the converter station and the alternating current system, Q_refTaking 310MVar as a reference value set for operation and maintenance personnel; for AC filters, Q_dzTaking 220MVar for the dead zone of switching; for AC filters, Q_dzTaking 280MVar for switching dead zones; in general, Q_refSet to zero, Q to ensure that a backup AC filter can participate in voltage regulation_refTaking an average value of rated power capacity of the reactive group;

margin n of AC filter_{_ACF}Selecting: when the total number of the configuration of the alternating current filter minus the total number of the operation is more than 1, n_{_ACF}Taking 1, otherwise, taking 0;

parallel capacitor margin n_{_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;

low-voltage reactor margin n_{_LVR}Selecting: when the total configuration number minus the total operation number of the low-voltage reactor is more than 1, n_{_LVR}Taking 1, otherwise, taking 0;

step 5, determining a reactive power compensation device participating in margin voltage regulation, and when an alternating current bus is in overvoltage operation, selecting the last reactive power group which is put into a switching sequence by a margin voltage regulation alternating current filter or a parallel capacitor in order to reduce interference on the existing reactive power balance control strategy and meet a margin condition and a voltage starting condition; when the alternating current bus is in undervoltage operation, the alternating current filter or the parallel capacitor participating in margin voltage regulation selects the last reactive power group which is not put into the switching sequence; the low-voltage reactors participating in margin voltage regulation are randomly selected with the aim of balancing the low impedance of the two contact transformers as much as possible;

and 6, executing a control strategy:

(1) when 524kV is less than or equal to U₁When the voltage is less than or equal to 536.8kV, the voltage fluctuation of the alternating current bus is controlled and balanced by the trigger angle alpha, and the converter transformer sub-joint and the reactive power compensation device participating in voltage regulation do not act;

(2) when 536.8kV < U₁When the voltage of the alternating current bus is continuously increased, starting a voltage regulating program;

(3) when 537kV is less than U₁When the voltage is less than or equal to 542kV, preferentially judging the allowance n of the low-voltage reactor_{_LVR}If the voltage is 1, starting low-voltage reactor voltage regulation and putting in a low-voltage reactor participating in margin voltage regulation; if the low resistance is added, U₁Is still greater than U_1maxStarting a tap to regulate the voltage; if n is_{_LVR}If the voltage is 0, the tap is directly started to regulate the voltage; after the overvoltage is recovered, the allowance n of the low-voltage reactor is judged preferentially_{_LVR}If the voltage is 1, cutting off the low-voltage reactor participating in margin voltage regulation; if n is_{_LVR}If the voltage is 0, the tap is directly started to regulate the voltage;

(4) when 542kV is less than U₁When the voltage is less than or equal to 550kV, preferentially judging the margin n of the alternating current filter_{_ACF}If the voltage is 1, starting the AC filter to regulate the voltage, and cutting off the AC filter participating in margin voltage regulation, if the voltage is 0 or after the AC filter is cut off, U₁Is still greater than U_1maxThen, referring to item (3) of step 6, control is performed; after the overvoltage is recovered, preferentially judging whether the cut alternating current filter meets the requirement of discharging time, and if so, inputting the alternating current filter; if not, controlling with reference to item (3) in the step 6;

(5) when U is turned₁When the voltage is more than 550kV, the margin n of the parallel capacitor is judged preferentially_{_SC}If the voltage is 1, starting the parallel capacitor to regulate the voltage, cutting off the parallel capacitor participating in margin voltage regulation, if the voltage is 0 or after the parallel capacitor is cut off, U₁If the voltage is still greater than 536.8kV, the control is carried out according to item (4) in the step 6; after the overvoltage is recovered, whether the cut parallel capacitor meets the discharge condition is judged preferentiallyIf the requirement is met, the parallel capacitor is put into the capacitor; if not, referring to the item (4) in the step 6 for control;

(6) when 523kV is less than or equal to U₁When the voltage is less than 524kV, the lower limit of the trigger angle is just beyond, the tap joint enters a waiting period, and if the voltage of the alternating current bus is continuously reduced, a voltage regulating program is started;

(7) when the voltage of 510kV is less than or equal to U₁When the voltage is less than 523kV, preferentially judging the margin n of the low-voltage reactor_{_LVR}If the voltage is 1, starting low-voltage reactor voltage regulation, and cutting off a low-voltage reactor participating in margin voltage regulation; if low resistance after excision, U₁If the voltage is still less than 524kV, starting a tap for voltage regulation; if n is_{_LVR}If the voltage is 0, the tap is directly started to regulate the voltage; after the undervoltage is recovered, the allowance n of the low-voltage reactor is judged preferentially_{_LVR}If the voltage is 1, a low-voltage reactor participating in margin voltage regulation is put into use; if n is_{_LVR}If the voltage is 0, the tap is directly started to regulate the voltage;

(8) when U is more than or equal to 500kV₁When the voltage is less than 510kV, preferentially judging margin n of the alternating current filter_{_ACF}If the voltage is 1, starting the AC filter to regulate the voltage, and putting the AC filter participating in margin voltage regulation, if the voltage is 0 or after the AC filter is put in, U₁If the voltage is still less than 524kV, the control is carried out according to item (7) in the step 6; 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, referring to the item (7) in the step 6 for control;

(9) when U is turned₁When the voltage is less than 500kV, the margin n of the parallel capacitor is judged preferentially_{_SC}If the voltage is 1, starting the parallel capacitor to regulate the voltage, and inputting the parallel capacitor participating in margin voltage regulation, if the voltage is 0 or after the parallel capacitor is input, U₁If the voltage is still less than 524kV, the control is performed according to item (8) in the step 6; after the undervoltage is recovered, preferentially judging whether the switched parallel capacitors meet the interval time requirement, and if so, cutting off the parallel capacitors; if not, the control is performed according to item (8) of step 6.

The scope of the invention is not limited to the above embodiments, and various modifications and changes may be made by those skilled in the art, and any modifications, improvements and equivalents within the spirit and principle of the invention should be included in the scope of the invention.

Claims (1)

1. A converter transformer tap control method giving consideration to margin voltage regulation of a reactive power compensation device is characterized by comprising the following steps of: the method comprises the following steps:

step 1, determining a boundary value of alternating current bus voltage when a trigger angle of a rectifier station fluctuates in a dead zone range, considering a constant-power operation condition, and taking direct current voltage as a rated value:

the expression of the rectification side of the high-voltage direct-current transmission system is as follows:

wherein VdR is direct-current voltage at the rectifying side, tau is the number of six-pulse converter valves, VdioR is no-load direct-current voltage at the rectifying side, Xr is phase-change reactance, U is₁Is the primary side alternating voltage of the converter transformer, namely the alternating bus voltage, Tn is the actual tap position, T_NFor the rated tap position, Δ U is the converter shift distance, η_NThe rated transformation ratio of the converter transformer is obtained;

under the operating condition of constant power, the direct current voltage VdR on the rectifying side is unchanged, the direct current Id is a constant value, the VdioR cos alpha is a constant value, if the trigger angle alpha fluctuates in the dead zone range, the tap joint cannot be started to regulate the voltage, and at the moment, U is regulated₁Cos α remains constant, the firing angle α is offset by a margin of 2.5 ° from the nominal value, and 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_1NRated for AC bus, U_1min、U_1maxThe minimum value and the maximum value of the alternating current bus voltage are respectively when the trigger angle of the rectifier station fluctuates in the dead zone range; alpha is alpha_NIs a firing angle rating;

step 2, obtaining a voltage regulating starting fixed value of the low-voltage reactor: u shape_{1max_LVR}、U_{1min_LVR}(ii) a Wherein U is_{1max_LVR}、U_{1min_LVR}Respectively representing the voltage limit values of the alternating-current bus for starting the low-voltage reactor to be switched in and out;

according to the field operation rule of the converter station, when the direct current is locked to operate, 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 that of the U bus_{1max_LVR}Time delay putting a group of voltage reactors; when the AC bus voltage is lower than U_{1min_LVR}Time delay cutting off a group of voltage reactors;

step 3, obtaining a starting fixed value of the alternating current filter: u shape_{1max_LIMIT}、U_{1max_LIM_ENBL}、U_{1min_LIM_ENBL}、U_{1min_LIMIT}(ii) a Wherein, U_{1max_LIMIT}、U_{1min_LIMIT}Respectively representing the voltage limit value of an alternating current bus for starting the cut-off or input of the alternating current filter; u shape_{1max_LIM_ENBL}、U_{1min_LIM_ENBL}Respectively representing the voltage limit values of the alternating current bus for prohibiting the input and the cut-off of the alternating current filter;

according to the field operation rule of the converter station, if the voltage exceeds the maximum amplitude limit U_{1max_LIMIT}When the voltage rises, the reactive power control cuts off the filter bank in sequence to prevent the voltage from rising continuously; if the voltage is below the lowest limit U_{1min_LIMIT}In time, reactive power control is also put into the filter bank in order to prevent the voltage from continuously reducing; if a further set of filters is applied, this will cause the voltage to exceed U_{1max_LIM_ENBL}Prohibiting the operation of the filter bank; similarly, if there is a further filter cut-off, this will cause the voltage to fall below U_{1min_LIM_ENBL}The operation of the cut-out filter bank will be disabled;

step 4, determining the allowance of the reactive power compensation device; according to a field reactive power exchange control strategy, a certain deviation exists between actual reactive power exchange and planned reactive power exchange of an alternating current-direct current system, if the reactive power exchange exceeds a deviation limit value, an alternating current filter is put in or cut off, and the following formula is met:

wherein Q is the reactive exchange quantity of the converter station and the alternating current system, Q_refReference value, Q, set for operation and maintenance personnel_dzIs a switching dead zone; in general, Q_refSet to zero, Q to ensure that a backup AC filter can participate in voltage regulation_refTaking an average value of rated power capacity of the reactive group;

margin n of AC filter_{_ACF}Selecting: when the total number of the configuration of the alternating current filter minus the total number of the operation is more than 1, n_{_ACF}Taking 1, otherwise, taking 0;

parallel capacitor margin n_{_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;

low-voltage reactor margin n_{_LVR}Selecting: when the total configuration number minus the total operation number of the low-voltage reactor is more than 1, n_{_LVR}Taking 1, otherwise, taking 0;

step 5, determining a reactive power compensation device participating in margin voltage regulation, and when an alternating current bus is in overvoltage operation, selecting the last reactive power group which is put into a switching sequence by a margin voltage regulation alternating current filter or a parallel capacitor in order to reduce interference on the existing reactive power balance control strategy and meet a margin condition and a voltage starting condition; when the alternating current bus is in undervoltage operation, the alternating current filter or the parallel capacitor participating in margin voltage regulation selects the last reactive power group which is not put into the switching sequence; the low-voltage reactors participating in margin voltage regulation are randomly selected with the aim of balancing the low impedance of the two contact transformers as much as possible;

and 6, executing a control strategy:

(1) when U is turned_1min≤U₁≤U_1maxDuring the process, the voltage fluctuation of the balanced alternating-current bus is controlled by a trigger angle alpha, and the converter transformer tap and the reactive power compensation device participating in voltage regulation do not act;

(2) when U is turned_1max＜U₁≤U_{1max_LVR}When the trigger angle just exceeds the upper limit, the tap joint enters a waiting period, and if the voltage of the alternating current bus is continuously increased, a voltage regulating program is started;

(3) when U is turned_{1max_LVR}＜U₁≤U_{1max_LIM_ENBL}Firstly judging the allowance n of the low-voltage reactor_{_LVR}If the voltage is 1, starting low-voltage reactor voltage regulation and putting in a low-voltage reactor participating in margin voltage regulation; if the low resistance is added, U₁Is still greater than U_1maxStarting a tap to regulate the voltage; if n is_{_LVR}If the voltage is 0, the tap is directly started to regulate the voltage; after the overvoltage is recovered, the allowance n of the low-voltage reactor is judged preferentially_{_LVR}If the voltage is 1, cutting off the low-voltage reactor participating in margin voltage regulation; if n is_{_LVR}If the voltage is 0, the tap is directly started to regulate the voltage;

(4) when U is turned_{1max_LIM_ENBL}＜U₁≤U_{1max_LIMIT}When the AC filter is in operation, the margin n of the AC filter is determined with priority_{_ACF}If the voltage is 1, starting the AC filter to regulate the voltage, and cutting off the AC filter participating in margin voltage regulation, if the voltage is 0 or after the AC filter is cut off, U₁Is still greater than U_1maxThen, referring to item (3) of step 6, control is performed; after the overvoltage is recovered, preferentially judging whether the cut alternating current filter meets the requirement of discharging time, and if so, inputting the alternating current filter; if not, controlling with reference to item (3) in the step 6;

(5) when U is turned₁＞U_{1max_LIMIT}Firstly, the margin n of the parallel capacitor is judged_{_SC}If the voltage is 1, starting the parallel capacitor to regulate the voltage, cutting off the parallel capacitor participating in margin voltage regulation, if the voltage is 0 or after the parallel capacitor is cut off, U₁Is still greater than U_1maxThen, referring to item (4) of step 6, control is performed; after the overvoltage is recovered, preferentially judging whether the cut parallel capacitor meets the requirement of discharging time, and if so, putting the parallel capacitor into the overvoltage recovery circuit; if not, referring to the item (4) in the step 6 for control;

(6) when U is turned_{1min_LVR}≤U₁＜U_1minWhen the trigger angle just goes beyond the lower limit, the tap enters a waiting period, if the voltage of the alternating current bus is continuously reduced,starting a voltage regulating program;

(7) when U is turned_{1min_LIM_ENBL}≤U₁＜U_{1min_LVR}Firstly judging the allowance n of the low-voltage reactor_{_LVR}If the voltage is 1, starting low-voltage reactor voltage regulation, and cutting off a low-voltage reactor participating in margin voltage regulation; if low resistance after excision, U₁Is still less than U_1minStarting a tap to regulate the voltage; if n is_{_LVR}If the voltage is 0, the tap is directly started to regulate the voltage; after the undervoltage is recovered, the allowance n of the low-voltage reactor is judged preferentially_{_LVR}If the voltage is 1, a low-voltage reactor participating in margin voltage regulation is put into use; if n is_{_LVR}If the voltage is 0, the tap is directly started to regulate the voltage;

(8) when U is turned_{1min_LIMIT}≤U₁＜U_{1min_LIM_ENBL}When the AC filter is in operation, the margin n of the AC filter is determined with priority_{_ACF}If the voltage is 1, starting the AC filter to regulate the voltage, and putting the AC filter participating in margin voltage regulation, if the voltage is 0 or after the AC filter is put in, U₁Is still less than U_1minThen, referring to item (7) of step 6, performing control; 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, referring to the item (7) in the step 6 for control;

(9) when U is turned₁＜U_{1min_LIMIT}Firstly, the margin n of the parallel capacitor is judged_{_SC}If the voltage is 1, starting the parallel capacitor to regulate the voltage, and inputting the parallel capacitor participating in margin voltage regulation, if the voltage is 0 or after the parallel capacitor is input, U₁Is still less than U_1minThen, referring to item (8) of step 6, control is performed; after the undervoltage is recovered, preferentially judging whether the switched parallel capacitors meet the interval time requirement, and if so, cutting off the parallel capacitors; if not, the control is performed according to item (8) of step 6.

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