CN110556838B

CN110556838B - Method and device for stabilizing frequency of power supply direct current sending system

Info

Publication number: CN110556838B
Application number: CN201810549653.3A
Authority: CN
Inventors: 贾俊川; 仲悟之; 张健; 易俊; 于强; 刘丽平; 贺庆; 马士聪; 林伟芳; 程势高
Original assignee: State Grid Corp of China SGCC; China Electric Power Research Institute Co Ltd CEPRI
Current assignee: State Grid Corp of China SGCC; China Electric Power Research Institute Co Ltd CEPRI
Priority date: 2018-05-31
Filing date: 2018-05-31
Publication date: 2023-02-03
Anticipated expiration: 2038-05-31
Also published as: CN110556838A

Abstract

The invention provides a method and a system for stabilizing the frequency of a power supply direct current sending system, comprising the following steps: after the direct current blocking fault is calculated, the available resource capacity in the execution station and the total amount of safety control measures to be taken are calculated; calculating the proportional relation between the direct current combined modulation measure of the direct current sending system and the measure of the cutting unit to the suppression frequency amplitude; based on the available resource capacity, the total amount of safety control measures to be taken and the proportional relation, the execution stations needing to execute the safety control actions are calculated, and each execution station executes the corresponding safety control action, so that the problem that the frequency of a power grid sent out after an extra-high voltage direct-current transmission project has a blocking fault, which is greatly increased, is easy to cause unordered tripping of a conventional unit and a new energy source unit in the power grid, and further the frequency of the power grid sent out by direct-current transmission is stable is solved, and the problem that the frequency of the power grid sent out by the conventional unit and the new energy source unit is unordered due to the frequency increase after the direct-current blocking fault, and further the frequency of the power grid sent out by direct current is unstable can be avoided.

Description

Method and device for stabilizing frequency of power supply direct current sending system

Technical Field

The invention relates to the technical field of power system operation and control, in particular to a method and a device for stabilizing the frequency of a power supply direct current sending system.

Background

With the implementation of an air pollution prevention action plan and the gradual promotion of the strategy of vigorously developing new energy and 'west-east power transmission' in China, a new energy power generation technology mainly represented by wind power is continuously developed, and the ultrahigh-voltage direct-current engineering with long distance and large capacity is continuously put into operation. At present, the energy approval of a thermal power generating unit is strict, and the construction and the production are relatively lagged, so that a multi-return-air-fire bundled extra-high voltage direct current transmission project which is constructed and put into operation lacks a matched power supply; on the other hand, the existing planned and about to be built into a large-capacity commissioning ultra-high-voltage direct-current transmission project is used for solving the problem of surplus electric power of some energy provinces, the delivered electric power of the ultra-high-voltage direct-current transmission project is completely collected from the surplus electric power in the network in a long distance, and the ultra-high-voltage direct-current transmission project has important significance for promoting the national optimal allocation of energy resources, relieving the atmosphere pollution control pressure, solving the problem of energy-based ground power accumulation and improving the new energy consumption capacity.

Because the extra-high voltage direct current transmission project has large outgoing power and high capacity-to-outgoing power grid scale occupation ratio, when the extra-high voltage direct current has single and double pole blocking faults, the frequency of the outgoing power grid is rapidly and greatly increased, disordered tripping of a conventional unit and a new energy unit in the outgoing power grid is easily caused, and the frequency of the direct current transmission outgoing power grid is unstable. How to operate quickly, reliably and sufficiently has great significance for the frequency stabilization of a large-capacity direct current transmission system, but no relevant research aiming at the problem exists at present.

Disclosure of Invention

In order to solve the problem that the frequency of a power transmission grid after the locking fault of an extra-high voltage direct current transmission project is greatly increased, which easily causes the disordered tripping of a conventional unit and a new energy unit in the power transmission grid, and further causes the frequency stability of the direct current transmission power transmission grid, the invention provides a method for stabilizing the frequency of a power supply direct current transmission system, which comprises the following steps:

after the direct current blocking fault is calculated, the available resource capacity in the execution station and the total amount of safety control measures to be taken are calculated;

calculating the proportional relation between the direct current combined modulation measure of the direct current sending system and the measure of the cutting unit to the suppression frequency amplitude;

and calculating the execution stations needing to execute the safety control action based on the available resource capacity, the total quantity of the safety control measures needing to be taken and the proportional relation, and executing the corresponding safety control action by each execution station.

Preferably, after the dc blocking fault is calculated, the total amount of safety control measures to be taken includes:

calculating the maximum direct current power allowed by the critical stability of the direct current sending system frequency when safety control measures are not taken after the direct current lockout fault according to the direct current sending system simulation model;

obtaining the variable quantity of active power transmitted by a direct current transmission system before and after a direct current blocking fault;

and calculating the safety control measure quantity required to be taken by the power grid after the direct current blocking fault is sent out according to the variable quantity of the active power transmitted by the direct current power transmission system before and after the direct current blocking fault.

Preferably, after the dc blocking fault is calculated, the executing available resource capacity in the station includes:

calculating available resource capacity in the direct current power emergency modulation execution station;

and calculating the available resource capacity in the execution station of the cutter.

Preferably, the available resource capacity in the dc power emergency modulation execution station is calculated according to the following formula:

P _t∑ ＝P _tup∑ +P _tdn∑

wherein, P _t∑ Performing intra-site available resource capacity for direct current power emergency modulation; p _tup∑ Considering the direct current short-time overload capacity and the maximum speed-rising power sum of stable operation of a power grid at a transmitting end and a receiving end for each direct current transmitted from the system; p _tdn∑ And considering the sum of the minimum direct current power and the maximum speed-reduction power of the safe and stable operation of the power grid at the transmitting end and the receiving end for each direct current input in the system.

Preferably, the capacity of available resources in the cutter execution station is as follows:

P _g∑ ＝P _gw∑ +P _gh∑ +P _gg∑

in the formula, P _g∑ Executing available resource capacity in the station for the cutter; p is _gw∑ For the capacity, P, of a switchable unit in a wind power plant _gh∑ For switchable unit capacity, P, in hydroelectric power stations _gg∑ The capacity of the switchable unit in the thermal power execution station is determined.

Preferably, the calculating the proportional relationship between the measure of the dc joint modulation of the dc sending system and the measure of the cutting unit to the suppression frequency amplitude includes:

the relationship of the dc joint modulation measure to the suppression frequency amplitude is calculated as follows:

k _t ＝ΔP _t /Δf

wherein k is _t For the proportional relation of DC combined modulation measure to the amplitude of the suppression frequency, Δ f is the unit frequency conversion of the sending system, Δ P _t The total amount of the direct current power which is required to be modulated for ensuring the frequency amplitude unit frequency variation of the system to be sent out after the direct current locking fault occurs;

calculating the relationship k of the measure of the cutting unit to the amplitude of the suppression frequency _g As follows:

k _g ＝ΔP _g /Δf

where Δ f is the transmission system unit frequency conversion amount, Δ P _g The total amount of the units which are required to be cut off for ensuring the frequency amplitude unit frequency variation of the sending system after the direct current blocking fault occurs;

calculating the proportional relation of the direct current combined modulation measure and the measure of the cutting unit to the amplitude of the suppression frequency based on the relation of the direct current combined modulation measure to the amplitude of the suppression frequency and the relation of the measure of the cutting unit to the amplitude of the suppression frequency, as shown in the following formula:

k ₀ ＝k _g /k _t ；

wherein k is ₀ The ratio of the direct current combined modulation measure and the measure of the cutting machine set to the amplitude of the suppression frequency is calculated.

Preferably, the calculating, based on the available resource capacity, the total amount of the safety control measures to be taken, and the proportional relationship, an execution station that needs to execute a safety control action includes:

the execution station comprises a direct current power emergency modulation execution station and a cutter execution station;

when the available resource capacity in the direct current power emergency modulation execution station does not meet the total amount of safety control measures to be taken, calculating the total amount of units which need to be cut off by a safety control system after the direct current blocking fault;

based on the total amount of the unit to be cut off by the safety control system, calculating the total amount of actually-taken safety control measures, the number of executing stations participating in the direct-current power emergency modulation and the number of the cutting machine executing stations according to the preset sequence of the executing station actions;

and the total amount of the units required to be cut by the safety control system is less than the total amount of the corresponding units under the number of the generator cutting execution stations.

Preferably, when the available resource capacity in the direct-current power emergency modulation execution station does not satisfy the total amount of safety control measures to be taken, calculating the total amount of the safety control system cut-off units after the direct-current blocking fault is as follows:

P' _g∑ ＝P _Σ -P _t∑ k ₀

of formula (II) to (III)' _g∑ The total amount of the unit is required to be cut off; p _Σ The total amount of safety control measures; p is _tΣ The available resource capacity in the station is performed for the dc power emergency modulation.

Preferably, the number of the direct-current power emergency modulation execution stations and the generator tripping execution stations which need safety control actions is calculated according to a preset sequence of the execution station actions based on the total amount of the cutting unit according to the following formula:

in the formula, P _s I is the sequence number of the direct current power emergency modulation execution station and j is the sequence number of the generator tripping execution station for the total amount of the actually adopted safety control measures; p is _sti Safety control modulation quantity, Z, for i DC power emergency modulation execution stations _t Number of executing stations for emergency modulation of actual DC power, Z _t Is a positive integer; p _sgj Safety control of the cutting machine for j cutting machine execution stations, Z _g Number of stations for actual cutting machines, Z _g To be just neatCounting;

preferably, the predetermined sequence of executing station actions includes: firstly, direct current emergency combined modulation is adopted, and then the unit is cut off according to the sequence of a cutting machine;

the cutter sequence comprises cutter sequences of different types of units and cutter sequences of the same type of units;

wherein, the cutter sequence of different types of units is: sequentially cutting off a wind turbine generator set, a hydroelectric generator set and a thermal power generator set;

the cutter sequence of the same type of unit comprises:

sequentially cutting off the wind turbines according to the sequence from near to far from the direct current converter station, or sequentially cutting off the wind turbines according to the sequence from large to small of transient voltage variation of a bus at the end of the direct current near-zone wind turbine after the direct current blocking fault;

sequentially cutting off the hydroelectric generating sets according to the sequence of the actual output of the hydroelectric generating sets from large to small, or cutting off the actual output of the hydroelectric generating sets according to the sequence of the contribution of the actual output of the hydroelectric generating sets to the short-circuit current of the converter station from small to large;

and sequentially cutting off the thermal power generating units according to the sequence of the actual output of the thermal power generating units from large to small, or sequentially cutting off the thermal power generating units according to the sequence of the contribution of the thermal power generating units to the short-circuit current of the converter station from small to large.

An apparatus for stabilizing the frequency of a power supply DC transmission system, comprising:

a first calculation module: the system is used for calculating the available resource capacity in the execution station and the total amount of safety control measures to be taken after the direct current blocking fault occurs;

a second calculation module: the method is used for calculating the proportional relation between the direct current combined modulation measure of the direct current sending system and the measure of the cutting unit to the suppression frequency amplitude;

a third calculation module: and the execution stations which need to execute the safety control action are calculated based on the available resource capacity, the total quantity of the safety control measures which need to be taken and the proportional relation, and each execution station executes the corresponding safety control action.

Preferably, the first calculation module includes:

a direct current power calculation unit: the system is used for calculating the maximum direct current power allowed by the critical stability of the system frequency when the safety control measures are not taken after the direct current lockout fault is sent out according to the direct current sending out system simulation model;

an acquisition unit: the method comprises the steps of obtaining the variable quantity of active power transmitted by a direct current power transmission system before and after a direct current blocking fault;

a safety control measure quantity calculation unit: and the method is used for calculating the safety control measure quantity required to be taken by the power grid after the direct current blocking fault is sent out according to the variable quantity of the active power transmitted by the direct current power transmission system before and after the direct current blocking fault.

Preferably, the third calculation module includes:

a total amount calculation unit: the method is used for calculating the total amount of the unit to be cut off by the safety control system after the direct current blocking fault when the available resource capacity in the direct current power emergency modulation execution station does not meet the total amount of the safety control measures to be taken;

an execution station count calculation unit: the method is used for calculating the total quantity of the safety control measures actually taken, the quantity of the execution stations participating in the direct-current power emergency modulation and the quantity of the generator tripping execution stations according to the preset sequence of the execution stations actions based on the total quantity of the generator sets required to be cut by the safety control system.

Moreover, compared with the closest comparison documents, the application also has the following beneficial effects:

1. the application provides a method and a device for stabilizing the frequency of a power supply direct current sending system, after a direct current blocking fault is calculated, the available resource capacity in an execution station and the total quantity of safety control measures to be taken are calculated, the proportional relation of direct current combined modulation measures of the direct current sending system and measures of a cutting unit to the amplitude of suppression frequency is calculated, the execution station needing to execute the safety control action is calculated based on the available resource capacity, the total quantity of the safety control measures to be taken and the proportional relation, each execution station executes corresponding safety control action, and the problems that the frequency is greatly increased after the direct current fault, so that a conventional unit and a new energy unit in a sending power grid are tripped out in an unordered mode, and the frequency of direct current transmission sending out the power grid is unstable can be avoided;

2. according to the method and the device for stabilizing the frequency of the power supply direct current sending-out system, on one hand, the action sequence of each execution station set by the safety control system preferentially adopts multi-direct current emergency combined modulation, so that the total machine switching amount of the sending-out system after a direct current blocking fault can be effectively reduced; on the other hand, the wind power generating unit, the hydroelectric generating unit and the thermal power generating unit are firstly cut off, so that the probability that the thermal power generating unit and even the hydroelectric generating unit are frequently switched can be effectively reduced, the economic benefit of a thermal power plant is kept, and the synchronous and stable operation level of a high-capacity direct current sending system without a matched power supply is ensured not to be greatly weakened;

3. the invention provides a method and a device for stabilizing the frequency of a power supply direct current sending-out system, which can effectively ensure the frequency stability of the sending-out system after the locking fault of a large-capacity direct current transmission project without a matched power supply by calculating the number of execution stations needing to act according to the sequence set by a safety control measure, ensure that the safety control system can still execute sufficient measure even if partial execution stations have no direct current modulation quantity or the power of a unit can be cut, and can cope with the arrangement of a mode with endless change in an actual system;

4. the invention provides a method and a device for stabilizing the frequency of a power supply direct current sending system.A direct current safety control master station uniformly issues safety control instructions, and each execution station executes the safety control instructions respectively, so that the channel time of a safety control channel is reduced, the safety control instructions can be ensured to be issued and executed quickly, and the frequency of the direct current sending system without a matched power supply is effectively prevented from being increased quickly and greatly after a direct current locking fault occurs;

5. the method and the device for stabilizing the frequency of the power supply direct current sending-out system have strong operability, can be used for making and implementing safety control measures of an actual extra-high voltage direct current transmission project and guiding the reliable operation of the extra-high voltage direct current transmission project and the safe and stable operation of an alternating current-direct current hybrid power grid after the extra-high voltage direct current transmission project is put into operation, and have great practical significance.

Drawings

FIG. 1 is a flow chart of the method of the present invention.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

The invention relates to a method and a device for stabilizing the frequency of a power supply direct current sending system, which are explained in detail by combining the embodiment:

example 1

After the direct current blocking fault is calculated, the available resource capacity in the execution station and the total amount of safety control measures to be taken are calculated, and the execution station comprises a direct current power emergency modulation execution station and a switching machine execution station;

calculating the proportional relation between the direct current combined modulation measure of the direct current sending system and the measure of the resection unit to the suppression frequency amplitude, wherein the proportional relation comprises the proportional relation between the direct current combined modulation measure and the measure of the resection unit to the suppression frequency amplitude, which is calculated based on the relation between the direct current combined modulation measure and the suppression frequency amplitude and the relation between the measure of the resection unit and the suppression frequency amplitude;

based on the available resource capacity, the total amount of the safety control measures to be taken and the proportional relation, calculating the execution station which needs to execute the safety control action, and based on the execution station, cutting off the unit, wherein the method comprises the following steps:

and when the total amount of the required cutting machine sets is distributed to the cutting machine execution stations, the actual total amount (actual value) of the cutting machine sets is considered to be larger than the total amount (theoretical value) of the required cutting machine sets calculated in advance.

Example 2

The embodiment of the invention provides a method for stabilizing the frequency of a power supply direct current sending system, which comprises the following specific processes:

s101: acquiring the total amount of safety control measures required by the high-capacity direct-current sending-out system after the direct-current lockout fault, and counting the total amount of available resources in each safety control execution station in the high-capacity direct-current sending-out system without a matched power supply when the direct-current lockout fault occurs;

s102: calculating the proportional relation of the direct-current emergency combined modulation measures of the high-capacity direct-current sending-out system without the matched power supply after the direct-current blocking fault and the measures of the cut-off unit to the suppression frequency amplitude, and then calculating the total quantity of the cut-off unit required for ensuring the sending-out system frequency to be stable and the proportional relation of the direct-current combined modulation measures and the measures of the cut-off unit to the suppression frequency amplitude after the direct-current blocking fault according to the total quantity of the safety control measures required for the sending-out system after the direct-current blocking fault and the proportional relation of the measures of the direct-current combined modulation measures and the measures of the cut-off unit to the suppression frequency amplitude;

s103: and calculating the number of execution stations needing safety control action after the direct current blocking fault according to the action sequence of each execution station set by the safety control system, issuing a safety control instruction to each execution station by the direct current safety control master station system, and executing the received safety control instruction by each execution station.

In the above S101, the specific process of obtaining the total amount of safety control measures to be taken by the sending-out system after the dc blocking fault is as follows:

(1) Establishing a simulation model of a direct current sending system without a matched power supply, calculating the maximum direct current power allowed by the critical stability of the frequency of the direct current sending system without the matched power supply when no safety control measure is taken after the direct current lockout fault according to the simulation model of the direct current sending system without the matched power supply, and setting the maximum direct current power allowed by the critical stability of the frequency of the direct current sending system without the matched power supply to be the maximum power unbalance amount P which can be born by the direct current sending system without the matched power supply when no cutting measure is taken after the direct current lockout fault ₀ ；

The simulation model of the direct current transmission system without the matched power supply refers to actual measurement model parameters including an actual power grid synchronous generator, wind power, extra-high voltage direct current, load and the like, so that the voltage and frequency characteristics after an actual system accident can be accurately fitted.

The above-mentioned frequency critical stability of the dc sending system without the matching power supply means that the transient state maximum frequency of the dc sending system without the matching power supply after the dc single-pole or bipolar blocking fault does not exceed the maximum value of the post-accident frequency specified in the "requirement for stability calculation of power system", for example, 51Hz.

(2) The method for acquiring the variable quantity of the active power transmitted by the large-capacity direct-current transmission engineering before and after the direct-current blocking fault specifically comprises the following steps:

1) The method comprises the steps of monitoring the running state of a large-capacity direct-current transmission project in real time, wherein the running state comprises monopolar running or bipolar running, normal running or blocking fault and the like, and then respectively recording the active power P transmitted by the direct-current transmission project before and after the direct-current blocking fault ₁ 、P ₂ ；

2) According to P ₁ And P ₂ Obtaining the variable quantity delta P of the active power transmitted by the DC power transmission project without a matched power supply before and after the DC blocking fault, wherein delta P = P ₁ -P ₂ 。

(3) According to the variable quantity of the active power transmitted by the direct current transmission engineering before and after the direct current blocking fault, the total quantity of safety control measures which need to be taken by a direct current transmission system without a matched power supply after the direct current blocking fault is calculated, and the method specifically comprises the following steps:

safety control measure total P needed by system without matched power supply after DC blocking fault _Σ Represented by the formula:

P _Σ ＝ΔP-P ₀

in S101, the counting of the total amount of available resources in each safety control execution station in the high-capacity dc transmission system without the power supply during the dc blocking fault specifically includes:

(1) Monitoring various direct current running states participating in direct current power emergency modulation in a large-capacity direct current sending system without a matched power supply in real time, wherein the direct current running states comprise unipolar running or bipolar running, initial running power, allowed maximum running power, allowed minimum running power and the like;

(2) Respectively calculating the total amount of the rapidly-ascending direct current power and the rapidly-descending direct current power of the direct current power emergency rapid-ascending modulation execution station in the large-capacity direct current sending system without the matched power supply, and calculating the total modulatable direct current power in the direct current power emergency modulation execution station;

available resource capacity P in DC power emergency modulation execution station _t∑ Represented by the formula:

P _t∑ ＝P _tup∑ +P _tdn∑

wherein, P _tup∑ Considering the direct current short-time overload capacity and the maximum speed-rising power sum of stable operation of a power grid at a transmitting end and a receiving end for each direct current transmitted from the system; p is _tdn∑ And considering the sum of the minimum direct current power and the maximum speed-reduction power of the safe and stable operation of the power grid at the transmitting end and the receiving end for each direct current input in the system.

Total P of DC power rise _tup∑ Represented by the formula:

wherein m is a direct current return number which can participate in the power rise rapidly after the direct current lock of the non-matching power supply is carried out; p is _iN 、P _i0 The rated power and the initial running power of the ith return direct current with the power rising rapidly are respectively; k is a radical of _i In order to consider the direct current overload multiple of the ith loop participating in the power tight and rapid rise of the power grid at the transmitting end and the receiving end, the normal k is used for an extra-high voltage direct current project _i Less than or equal to 1.05, and k is usually equal to that of ultrahigh-voltage direct-current engineering _i ≤1.1。

Total P of emergency quick-reducing dc power _tdn∑ Represented by the formula:

wherein n is a direct current return number which can participate in the emergency rapid power reduction after the direct current lock of the matched power supply is not carried out; p _j0 、P _jmin The j-th initial direct current running power and the minimum running power which participate in the power rapid reduction and increase are respectively; k is a radical of _j In order to consider the direct current minimum power coefficient of the jth loop participating in the power emergency speed reduction of the stable operation of the power grid at the transmitting end and the receiving end, k is common _j ≥1。

(3) Respectively calculating the power of a wind power generating set generator tripping execution station, a hydroelectric generating set generator tripping execution station and a thermal power generating set generator tripping execution station in the large-capacity direct-current sending system without the matched power supply;

in the cutting machine execution stationAvailable resource capacity P _g∑ Represented by the formula:

P _g∑ ＝P _gw∑ +P _gh∑ +P _gg∑

wherein, P _gw∑ The capacity P of a switchable unit in a wind power execution station in a high-capacity direct current sending system without a matched power supply _gh∑ The capacity P of a switchable machine set in a hydroelectric execution station in a high-capacity direct-current sending system without a matched power supply _gg∑ The capacity of a switchable machine set in a live-electricity execution station in a high-capacity direct-current sending system without a matched power supply is obtained.

(4) And (3) calculating the sum of the modulatable direct-current capacity of the direct-current power emergency modulation execution station obtained in the step (2) and the switchable unit power of the wind turbine generator system generator tripping execution station, the hydroelectric turbine generator tripping execution station and the thermal turbine generator tripping execution station obtained in the step (3), namely the total amount of available resources in each safety control execution station in the large-capacity direct-current sending system without the matched power supply when the direct-current locking fails.

In the above S102, calculating a proportional relationship between the dc emergency combined modulation measure of the high-capacity dc sending system without the matching power supply after the dc blocking fault and the measure of the cutting unit to the suppression of the frequency increase specifically includes:

relationship k of DC combined modulation measure to suppression of frequency amplitude _t Represented by the formula:

k _t ＝ΔP _t /Δf

where Δ f is the unit frequency conversion (e.g., 1 Hz) of the transmission system, and Δ P _t And D, the total amount of the direct current power which needs to be modulated for ensuring the sending of the frequency amplitude unit frequency variation (1 Hz) of the system after the direct current lockout fault.

Relationship k of cut-off unit measure to suppression frequency amplitude _g Represented by the formula:

k _g ＝ΔP _g /Δf

where Δ f is the unit frequency conversion amount (e.g., 1 Hz) of the transmission system, and Δ P _g The total amount of the units which need to be cut off for ensuring the frequency amplitude unit frequency variation (1 Hz) of the sending-out system after the direct current blocking fault.

Proportional relation of DC combined modulation measure and cut-off unit measure to inhibition frequency amplitudeIs k is ₀ Represented by the formula:

k ₀ ＝k _g /k _t

in step S102, calculating the total amount of the units to be cut off after the dc blocking fault to ensure that the safety control system with stable system frequency is sent out includes:

total amount P 'of units needing to be subjected to supplementary cutting in security control system' _∑g Represented by the formula:

P' _∑g ＝P _Σ -P _t∑ k ₀

wherein, P' _∑g ≤P _∑g 。

In the above step S103, the sequence of actions of each execution station set by the safety control system is to preferentially adopt direct current emergency combined modulation, and then to cut off the units according to the cutting sequence, where the cutting sequence includes cutting sequences of different types of units and cutting sequences of the same type of units;

because a large number of sets need to be cut off after the high-capacity direct current is locked, in order to ensure that the short-circuit capacity and the reactive voltage supporting capacity of a system after the safety control generator tripping are not greatly weakened, the wind generation sets with poor regulating capacity are firstly cut off and then are conventional generator sets according to the sequence of the voltage and frequency regulating characteristics of the sets; in consideration of the starting and stopping speed of the units and the regional seasonal characteristics, heat supply needs to be met in winter in some provinces, and sufficient coal-fired thermal power generating units need to be guaranteed, so that the conventional units are arranged in the sequence of firstly cutting off the hydroelectric power generating units and then cutting off the thermal power generating units. Therefore, the cutting machines of different types of units sequentially cut off the wind turbine generator, the hydroelectric generator and the thermal power generator, namely, under the condition that the wind turbine generator, the hydroelectric generator and the thermal power generator exist, the wind turbine generator is cut off firstly, then the hydroelectric generator is cut off, and finally the thermal power generator is cut off; if the wind power generating set does not exist, the hydroelectric generating set is cut off firstly, and then the thermal generating set is cut off; and if the wind power generating unit and the hydroelectric generating unit do not exist, cutting off the thermal power generating unit.

The cutting sequence of the same type of unit is as follows:

in the process of cutting off the wind turbine generator, the cutting sequence is as follows:

the wind turbines can be sequentially cut off according to the sequence from near to far from the direct current converter station, and also can be sequentially cut off according to the sequence from large to small of transient state voltage variation of a generator-side bus of the direct current near-zone wind turbine after the direct current blocking fault;

in the process of cutting off the hydroelectric generating set, the cutting sequence is as follows:

the hydroelectric generating sets can be sequentially cut off according to the sequence from large to small of the actual output of the hydroelectric generating sets, and also can be sequentially cut off according to the sequence from small to large of the contribution to the short-circuit current of the converter station, and each power plant needs to be ensured to at least keep 1 hydroelectric generating set not to be cut off;

in the process of cutting off the thermal power generating unit, the cutting sequence is as follows:

the thermal power generating units can be sequentially cut off according to the sequence from large to small of the actual output of the thermal power generating units, and also can be sequentially cut off according to the sequence from small to large of the contribution to the short-circuit current of the converter station, and each power plant is required to be ensured to at least keep 1 thermal power generating unit not to be cut off.

In step S103, the calculating the number of execution stations that need security control after the dc blocking fault includes:

the number of executing stations requiring security control action is represented by the following formula:

wherein i and j are sequence numbers of each execution station; p _sti Safety control modulation quantity, Z, for i DC power emergency modulation execution stations _t The number of execution stations which can participate in the emergency modulation of the direct current power in the large-capacity direct current sending system without a matched power supply is increased; p is _sgj Safety control of the cutting machine for the execution stations of j cutting machines, Z _g Sending out the number of internal terminal execution stations of the system for high-capacity direct current without a matched power supply; p _s For all execution stations Z _t +Z _g Total amount of safety control measures of, and P _s ≥P _∑ 。

In the above S103, the issuing of the security control instruction to each execution station by the direct-current security control master station system, where the executing of the security control instruction by each execution station specifically includes:

the direct-current safety control master station is used for uniformly issuing safety control instructions to the z execution stations according to the number of the execution stations needing to act and by combining the setting sequence of the execution stations.

The direct current execution station executes a direct current power emergency modulation instruction, wherein the direct current power emergency modulation instruction comprises a direct current power rapid-up measure or a direct current power rapid-down measure;

the unit execution station executes measures for cutting off the units, including measures for cutting off wind turbine units, hydroelectric generating units and thermal power generating units.

Based on the same inventive concept, the embodiment of the present invention further provides a device for dealing with the frequency stability of the dc sending system without the supporting power supply, and because the principle of solving the problem of these devices is similar to the method for frequency stability of the dc sending system with the power supply, the implementation of these devices can refer to the implementation of the method, and the repeated parts are not described again.

The device for coping with the frequency stability of the direct current sending system without the matched power supply comprises a statistical module, a calculation module and an action module, wherein the functions of the three modules are respectively introduced as follows:

the counting module is used for acquiring the total amount of safety control measures which need to be taken by the direct-current sending system without the matched power supply after the direct-current blocking fault, and counting the total amount of available resources in each safety control execution station in the high-capacity direct-current sending system without the matched power supply when the direct-current blocking fault occurs;

the calculation module is used for calculating the proportional relation between the direct-current emergency combined modulation measure of the high-capacity direct-current sending system without the matched power supply and the measure of the resection unit to the suppression frequency amplitude, calculating the total amount of the resection unit required by the safety control system for ensuring the stable frequency of the sending system after the direct-current lockout fault, and calculating the number of execution stations required by the safety control action after the direct-current lockout fault according to the sequence of the actions of each execution station set by the safety control system;

the generator tripping module is used for issuing the safety control instruction to each execution station by the direct-current safety control master station system, and the safety control execution stations are used for receiving the instruction issued by the master station and executing the received safety control instruction respectively.

The specific process of calculating the total quantity of safety control measures needing to be taken by the system without the matched power supply after the direct current blocking fault by the statistical module is as follows:

1) Establishing a simulation model of the direct current sending system without the matched power supply, calculating the maximum direct current power allowed by the critical stability of the frequency of the direct current sending system without the matched power supply when no safety control measure is taken after the direct current blocking fault is calculated according to the simulation model of the direct current sending system without the matched power supply, wherein the maximum direct current power allowed by the critical stability of the frequency of the direct current sending system without the matched power supply is the unbalance amount of the maximum power which can be born by the direct current sending system without the matched power supply when no generator tripping measure is taken after the direct current blocking fault.

2) The method comprises the following steps of obtaining the variable quantity of active power transmitted by a high-capacity direct-current transmission project before and after a direct-current blocking fault, and specifically:

2-1) monitoring the running state of the large-capacity direct current transmission project in real time, and respectively recording the active power P transmitted by the direct current transmission project before and after the direct current blocking fault ₁ 、P ₂ ；

2-2) according to P ₁ And P ₂ Obtaining the variable quantity delta P of the active power transmitted by the DC power transmission project without a matched power supply before and after the DC blocking fault, wherein delta P = P ₁ -P ₂ 。

3) According to the variable quantity of the active power transmitted by the direct-current transmission project before and after the direct-current blocking fault, the total quantity of safety control measures which need to be taken by a system without a matched power supply after the direct-current blocking fault is calculated, and the specific process is as follows:

safety control measure total P required by system without matched power supply after DC blocking fault _Σ Represented by the formula:

P _Σ ＝ΔP-P ₀

wherein, P ₀ The maximum power unbalance amount which can be borne by a large-capacity direct current sending system without a matched power supply is obtained.

The counting module counts the total amount of available resources in each safety control execution station in the large-capacity direct current sending system without the matched power supply when the direct current lockout is in fault, and the specific process is as follows:

monitoring various direct current running states participating in direct current power emergency modulation in a large-capacity direct current sending system without a matched power supply in real time, wherein the direct current running states comprise unipolar running or bipolar running, initial running power, allowed maximum running power, allowed minimum running power and the like;

respectively calculating the total quantity of the direct current power which can be quickly increased and the total quantity of the direct current power which can be quickly decreased and participates in the direct current power emergency speed-up modulation execution station in the large-capacity direct current sending system without the matched power supply, and calculating the total modulable direct current power in the direct current power emergency modulation execution station;

respectively calculating the power of a wind power generating set generator tripping execution station, a hydroelectric generating set generator tripping execution station and a thermal power generating set generator tripping execution station in the large-capacity direct-current sending system without the matched power supply;

and calculating the sum of the modulatable direct current capacity of the direct current power emergency modulation execution station and the power of the switchable units of the wind turbine generator system switching execution station, the hydroelectric generator system switching execution station and the thermal power generator system switching execution station, namely the sum of the modulatable direct current capacity of the direct current power emergency modulation execution station and the power of the switchable units of the wind turbine generator system switching execution station, the hydroelectric generator system switching execution station and the thermal power generator system switching execution station is the total amount of available resources in each safety control execution station in the high-capacity direct current sending system without the matched power supply when the direct current locking fails.

The specific process of calculating the proportional relation between the direct-current emergency combined modulation measure of the high-capacity direct-current sending system without the matched power supply after the direct-current blocking fault and the measure of the cutting unit to the suppression frequency amplitude by the calculating module is as follows:

k _t ＝ΔP _t /Δf

wherein Δ f is 1Hz, Δ P _t And the total amount of the direct current power which needs to be modulated for ensuring that the frequency of the system is increased by 1Hz after the direct current locking fault occurs.

k _g ＝ΔP _g /Δf

wherein Δ f is 1Hz, Δ P _g The total amount of the units which are required to be cut off for ensuring that the frequency of the system is increased by 1Hz after the direct current blocking fault occurs.

Proportional relation k of direct current combined modulation measure and cut-off unit measure to suppression frequency amplitude ₀ Represented by the formula:

k ₀ ＝k _g /k _t

the specific process of the total amount of the cut-off unit which needs to be supplemented by the safety control system for ensuring the stable frequency of the sending-out system after the direct current blocking fault is calculated by the calculating module is as follows:

P' _∑g ＝P _Σ -P _t∑ k ₀

wherein, P' _∑g ≤P _∑g 。

The action module preferentially adopts direct current emergency combined modulation according to the action sequence of each execution station set by the safety control system, and then cuts off the units according to the cutting sequence, wherein the cutting sequence comprises the cutting sequence of different types of units and the cutting sequence of the same type of units;

the wind turbine generator set, the hydroelectric generator set and the thermal power generator set are sequentially cut off by the cutter of different types of the generator sets, namely the wind turbine generator set is cut off firstly, then the hydroelectric generator set is cut off and finally the thermal power generator set is cut off under the condition that the wind turbine generator set, the hydroelectric generator set and the thermal power generator set exist; if the wind power generating set does not exist, the hydroelectric generating set is cut off firstly, and then the thermal generating set is cut off; and if the wind power generating unit and the hydroelectric generating unit do not exist, cutting off the thermal power generating unit.

The cutting sequence of the same type of unit is as follows:

The number of execution stations which need safety control action after the action module calculates the direct current blocking fault is as follows:

wherein i and j are sequence numbers of each execution station; p _sti Safety control modulation quantity, Z, for i DC power emergency modulation execution stations _t The number of execution stations which can participate in the emergency modulation of the direct current power in the large-capacity direct current sending system without a matched power supply is increased; p _sgj Safety control of the cutting machine for the execution stations of j cutting machines, Z _g The number of the internal cutting machine execution stations of the system is the large-capacity direct current output system without a matched power supply; p _s For all execution stations Z _t +Z _g Total amount of safety control measures of, and P _s ≥P _∑ 。

The method comprises the steps that a certain China Direct Current (DC) outward transmission system without a matched power supply is selected, the DC outward transmission system is used for extra-high voltage DC transmission system with the rated capacity of 1000 ten thousand kilowatts for outward transmission of surplus power, the DC transmission system is positioned in the surplus power in a transmission network, the matched power supply is not planned and built in the near area of a DC convertor station, the outward transmission power of a DC transmission project is completely collected from the surplus power of each provincial power grid in a long distance, and a corresponding electromechanical transient simulation calculation model is built based on measured data.

According to simulation calculation, if the transient state highest frequency of the regional power grid after bipolar locking of the extra-high voltage direct current transmission system does not exceed 51Hz, the maximum transmission power of the direct current transmission system is 300 ten thousand kilowatts, namely the maximum power unbalance amount born by the high-capacity transmission system is 300 ten thousand kilowatts.

Before the direct current blocking fault, the bipolar normally operates to transmit 1000 ten thousand kilowatts of active powerActive power delivered after bipolar blocking fault of current is reduced to 0, using P _Σ ＝ΔP-P ₀ After the direct current bipolar locking fault is calculated, in order to ensure that the frequency of the sending-out system does not exceed 51Hz, the total amount of safety control measures required is about 700 ten thousand kilowatts.

Because the large-capacity direct-current sending system without the matched power supply sends out 300 ten thousand kilowatts of direct-current A rated capacity and 300 ten thousand kilowatts of initial operating power, the direct-current power can be improved by 1.1 times of 300-300=30 ten thousand kilowatts according to 1.1 times of overload operating capacity; in addition, the rated capacity of the input direct current B is 75 ten thousand kilowatts, the initial operating power is 20 ten thousand kilowatts, the direct current power can be reduced by 20-8=12 ten thousand kilowatts according to the minimum operating power of 8 ten thousand kilowatts, and therefore the direct current is sent out of the system after the direct current locking fault, the total amount of the modulatable direct current power in the emergency united modulation execution station of the direct current power is about 42 ten thousand kilowatts.

The large-capacity direct current safety control system without the matched power supply is provided with 49 generator set generator executing stations, 14 generator set generator executing stations and 24 generator set generator executing stations, and the total generator set capacity of each executing station is far larger than 700 ten thousand kilowatts.

Based on the established simulation model, calculation shows that the proportional relation between the direct current A and B emergency combined modulation measures adopted after the large-capacity direct current blocking fault without the matched power supply and the measures of the cutting unit directly adopted to inhibit the frequency amplitude is about 1. Therefore, the total amount of the supplementary cutting machine set required by the safety control system for ensuring that the frequency of the delivery system does not exceed 51Hz after the direct current blocking fault is calculated to be 700-42 multiplied by 0.5=679 ten thousand kilowatts.

After the bipolar blocking fault of the extra-high voltage direct current transmission project occurs, a certain time delay is needed for the pole control system to cut off a filter in the direct current converter station, the voltage of a bus at the end of the converter station and a near-region wind turbine is increased in the time delay, and the closer the electrical distance between the wind turbine generator and the converter station is, the higher the voltage rise is, the easier the grid disconnection due to high voltage is. <xnotran> , , 49 , 567.5 . </xnotran>

In order to ensure the stable frequency of the delivery system, a safety control system is still required to supplement and cut hydroelectric power and even thermal power generating units 679-567.5=111.5 ten thousand kilowatts. The 14 hydroelectric generating set generator execution stations are ranked from small to large according to the contribution of the hydroelectric generating sets to the short-circuit current of the converter station, and the actual output of the hydroelectric generating sets in the 14 hydroelectric generating set generator execution stations is combined, so that the calculation shows that 2 hydroelectric generating set generator execution stations are required to perform actions, and about 120 ten thousand kilowatts are cut off.

For convenience of description, each part of the above apparatus is separately described as being functionally divided into various modules or units. Of course, the functionality of the various modules or units may be implemented in the same one or more pieces of software or hardware when implementing the present application.

Example 3

The invention also relates to a device for stabilizing the frequency of the power supply direct current sending system, which comprises three modules, namely a first calculation module, a second calculation module and a third calculation module;

the first calculation module is used for calculating the available resource capacity in the execution station and the total amount of safety control measures to be taken after the direct current blocking fault occurs, and the first calculation module comprises: a direct current power calculation unit: the system is used for calculating the maximum direct current power allowed by the critical stability of the system frequency when the safety control measures are not taken after the direct current lockout fault is sent out according to the direct current sending out system simulation model;

a safety control measure quantity calculation unit: the safety control measure quantity is used for calculating the safety control measure quantity to be taken by the power grid after the direct current blocking fault is sent out according to the variable quantity of the active power transmitted by the direct current transmission system before and after the direct current blocking fault;

the available resource capacity calculating unit in the emergency execution station is used for calculating the available resource capacity in the direct-current power emergency modulation execution station;

the available resource capacity calculating unit in the cutter execution station is used for calculating the available resource capacity in the cutter execution station;

the available resource capacity in the emergency execution station is calculated by the following formula in the available resource capacity calculation unit in the emergency execution station:

P _t∑ ＝P _tup∑ +P _tdn∑

wherein, P _t∑ Performing intra-site available resource capacity for direct current power emergency modulation; p _tup∑ Considering the direct current short-time overload capacity and the maximum speed-rising power sum of stable operation of a power grid at a transmitting end and a receiving end for each direct current transmitted from the system; p _tdn∑ Considering the sum of the minimum direct current power and the maximum speed-reduction power of safe and stable operation of a power grid at a transmitting end and a receiving end for each received direct current in the system;

the available resource capacity in the power cutting machine execution station available resource capacity calculation unit is as follows:

P _g∑ ＝P _gw∑ +P _gh∑ +P _gg∑

in the formula, P _g∑ Executing available resource capacity in the station for the cutter; p _gw∑ For the switchable unit capacity, P, in the wind power plant _gh∑ For switchable unit capacity, P, in hydroelectric power stations _gg∑ The capacity of a switchable unit in the thermal power execution station is obtained;

the second calculation module is used for calculating the proportional relation between the direct current combined modulation measure of the direct current sending-out system and the measure of the cutting unit to the suppression frequency amplitude;

the second calculation module comprises a first amplitude rising relation calculation unit, a second amplitude rising relation calculation unit and a third amplitude rising relation calculation unit;

the first amplitude relationship calculation unit is used for calculating the relationship of the direct current joint modulation measure to the suppression frequency amplitude, and the relationship is as follows:

k _t ＝ΔP _t /Δf

wherein k is _t For the proportional relation of DC combined modulation measure to the amplitude of the suppression frequency, Δ f is the unit frequency conversion (e.g. 1 Hz) of the sending system, Δ P _t The total amount of the direct current power which needs to be modulated for ensuring the sending of the system frequency amplitude unit frequency variation (1 Hz) after the direct current locking fault;

the second amplitude rising relation calculation unit is used for calculating the relation of the measures of the cutting unit to the amplitude of the suppression frequency, and the relation is as follows:

k _g ＝ΔP _g /Δf

where Δ f is the unit frequency conversion amount (e.g., 1 Hz) of the transmission system, and Δ P _g The total amount of the units which need to be cut off for ensuring the frequency amplitude unit frequency variation (1 Hz) of the system is sent out after the direct current blocking fault occurs;

the third amplitude relationship calculation unit is used for calculating the proportional relationship between the direct current combined modulation measure and the measure of the cutting unit to the amplitude of the suppression frequency based on the relationship between the direct current combined modulation measure and the amplitude of the suppression frequency and the relationship between the measure of the cutting unit and the amplitude of the suppression frequency, and the proportional relationship is as follows:

k ₀ ＝k _g /k _t ；

The third calculation module is used for calculating execution stations needing to execute the safety control action based on the available resource capacity, the total quantity of the safety control measures needing to be taken and the proportional relation, and each execution station executes the corresponding safety control action;

the third calculation module comprises a total amount calculation unit for calculating the total amount of the unit to be cut off by the safety control system after the direct current locking fault when the available resource capacity in the direct current power emergency modulation execution station does not meet the total amount of the safety control measures to be taken;

an execution station count calculation unit: the method is used for calculating the total amount of actually-taken safety control measures, the number of executing stations participating in direct-current power emergency modulation and the number of generator tripping executing stations according to the preset sequence of the executing stations based on the total amount of the generator sets required to be cut by the safety control system.

The total amount of the safety control system cut-off unit after the direct current blocking fault in the total amount calculation unit is as follows:

P' _g∑ ＝P _Σ -P _t∑ k ₀

of formula (II) to (III)' _g∑ The total amount of the unit is required to be cut off; p _Σ The total amount of safety control measures; p _tΣ Performing intra-site available resource capacity for direct current power emergency modulation;

the quantity of the direct-current power emergency modulation execution stations and the generator tripping execution stations which need safety control actions in the execution station quantity calculation unit is as follows:

in the formula, P _s I is the sequence number of the direct current power emergency modulation execution station and j is the sequence number of the generator tripping execution station for the total amount of the actually adopted safety control measures; p _sti Safety control modulation quantity, Z, for i DC power emergency modulation execution stations _t Number of executing stations for emergency modulation of actual DC power, Z _t Is a positive integer; p _sgj Safety control of the cutting machine for the execution stations of j cutting machines, Z _g Number of stations for actual cutting machines, Z _g Is a positive integer;

as will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

Finally, it should be noted that: the above embodiments are only intended to illustrate the technical solution of the present invention and not to limit the same, and a person of ordinary skill in the art can make modifications or equivalents to the specific embodiments of the present invention with reference to the above embodiments, and such modifications or equivalents without departing from the spirit and scope of the present invention are within the scope of the claims of the present invention as set forth in the claims.

Claims

1. A method for stabilizing the frequency of a power supply dc link system, the method comprising:

based on the available resource capacity, the total quantity of the safety control measures to be taken and the proportional relation, calculating the execution stations needing to execute the safety control action, and executing the corresponding safety control action by each execution station;

the calculating the proportional relation between the direct current combined modulation measure of the direct current sending system and the measure of the cutting unit to the suppression frequency amplitude comprises the following steps:

calculating the relation k of the DC combined modulation measure to the suppression frequency amplitude _t As follows:

k _t ＝ΔP _t /Δf

where Δ f is the transmission system unit frequency conversion amount, Δ P _t The total amount of the direct current power which is required to be modulated for ensuring the frequency amplitude unit frequency variation of the system to be sent out after the direct current locking fault occurs;

k _g ＝ΔP _g /Δf

wherein, Δ P _g The total amount of the units which are required to be cut off for ensuring the frequency amplitude unit frequency variation of the sending system after the direct current blocking fault occurs;

calculating the proportional relation of the direct current combined modulation measure and the cutting unit measure to the suppression frequency amplitude based on the relation of the direct current combined modulation measure to the suppression frequency amplitude and the relation of the cutting unit measure to the suppression frequency amplitude, as shown in the following formula:

k ₀ ＝k _g /k _t ；

wherein k is ₀ The ratio of the direct current combined modulation measure and the measure of the cutting machine set to the suppression frequency amplitude is determined;

the step of calculating the execution station which needs to execute the safety control action based on the available resource capacity, the total quantity of the safety control measures which need to be taken and the proportional relation comprises the following steps:

when the available resource capacity in the direct current power emergency modulation execution station does not meet the total amount of safety control measures to be taken, calculating the total amount of the units to be cut off by the safety control system after the direct current blocking fault as follows:

P′ _g∑ ＝P _Σ -P _t∑ k ₀

2. The method of claim 1, wherein the step of calculating the total amount of safety control measures to be taken after the dc blocking fault comprises:

obtaining the variable quantity of the active power transmitted by the direct current power transmission system before and after the direct current blocking fault;

and calculating the safety control measure quantity required to be taken by sending the direct current blocking fault out of the power grid according to the variable quantity of the active power transmitted by the direct current transmission system before and after the direct current blocking fault.

3. The method of claim 1, wherein calculating the dc blocking fault and then performing in-station available resource capacity comprises:

4. The method as claimed in claim 3, wherein the available resource capacity in the station for performing emergency modulation of DC power is calculated according to the following formula:

P _t∑ ＝P _tup∑ +P _tdn∑

wherein, P _t∑ Performing intra-site available resource capacity for direct current power emergency modulation; p is _tup∑ Considering the direct current short-time overload capacity and the maximum speed-rising power sum of stable operation of a power grid at a transmitting end and a receiving end for each direct current transmitted from the system; p is _tdn∑ And considering the sum of the minimum direct current power and the maximum speed reduction power of safe and stable operation of a power grid at a transmitting end and a receiving end for each received direct current in the system.

5. The method of claim 3, wherein the generator tripping operation is performed in a manner such that the available resource capacity in the generator tripping operation is as follows:

P _g∑ ＝P _gw∑ +P _gh∑ +P _gg∑

in the formula, P _g∑ Executing available resource capacity in the station for the cutter; p _gw∑ For the capacity, P, of a switchable unit in a wind power plant _gh∑ For switchable unit capacity, P, in hydroelectric power stations _gg∑ The capacity of the switchable unit in the thermal power execution station is determined.

6. The method for stabilizing the frequency of the power supply dc transmission system of claim 1, wherein the total amount of safety control measures actually taken, the number of the execution stations participating in the dc power emergency modulation and the number of the generator tripping execution stations are calculated according to the following formula based on the total amount of the control system requiring the cutting machine set and the preset sequence of the execution station actions:

k ₀ the ratio of the direct current combined modulation measure and the measure of the cutting machine set to the amplitude of the suppression frequency is obtained.

7. The method of claim 1, wherein the predetermined sequence of performing station actions comprises: firstly, direct current emergency combined modulation is adopted, and then the units are cut off according to the sequence of a cutting machine;

the cutter sequence of the same type of unit comprises:

sequentially cutting off the wind turbines from near to far according to the distance between the wind turbines and the direct current converter station, or sequentially cutting off the wind turbines according to the sequence that transient state voltage variation of a generator-side bus of the direct current near-zone wind turbines is from large to small after the direct current blocking fault;

and sequentially cutting off the thermal power generating units according to the sequence of the actual output of the thermal power generating units from large to small, or sequentially cutting off the contribution to the short-circuit current of the converter station from small to large.

8. An apparatus for stabilizing a frequency of a power supply dc transmission system, comprising:

a third calculation module: the system comprises a plurality of execution stations, a plurality of monitoring stations and a plurality of monitoring units, wherein the execution stations are used for calculating execution stations needing to execute security control actions based on the available resource capacity, the total quantity of the security control measures needing to be taken and a proportional relation, and each execution station executes corresponding security control actions;

k _t ＝ΔP _t /Δf

k _g ＝ΔP _g /Δf

k ₀ ＝k _g /k _t ；

P _g ' _∑ ＝P _Σ -P _t∑ k ₀

in the formula, P _g ' _∑ The total amount of the unit is required to be cut off; p _Σ The total amount of safety control measures; p _tΣ Performing intra-site available resource capacity for direct current power emergency modulation;

9. The apparatus of claim 8, wherein the first computing module comprises:

10. The apparatus of claim 8, wherein the third computing module comprises: