Power optimization method for key section of power grid considering direct current system putting into operation

Abstract

This invention discloses a power optimization method for critical sections of a power grid considering the implementation of a DC system. In this method, the power of each transmission channel at the critical section of the power grid under any AC / DC fault does not exceed the maximum power limit corresponding to that channel, and the sum of the power of each transmission channel is kept to the maximum. Furthermore, the power of the AC channel within the transmission channel is the sum of the power of the AC channel before the DC system is implemented and the power increment of the AC channel after the DC system is implemented. This method takes into account the impact of the DC system implementation on the power flow distribution at the critical section of the power grid, can adapt to the complex and variable operating modes of large AC / DC hybrid power grids, and can provide a reference for power grid dispatching and operation mode arrangement and power generation plan formulation.

Description

TECHNICAL FIELD

[0001] The application relates to a power optimization method for a power grid key section considering DC system input, and belongs to the technical field of power system operation control. BACKGROUND

[0002] In order to solve the problem of uneven distribution of energy, long-distance AC or DC power transmission is generally adopted at present to meet the load development needs of the area with less energy distribution. In the AC synchronous power grid, the power angle and voltage stability after single-channel fault of long-distance power transmission, and the power transmission capacity of the weak AC transmission section far less than the line thermal capacity make it difficult to effectively utilize the AC line transmission capacity. At the same time, due to the problem of exceeding the short-circuit current of the power grid, it is difficult to improve the power transmission capacity of the AC transmission section by newly building AC transmission lines, and the AC power grid transmission scale is limited.

[0003] As for the power grid key section formed between one region and another region, how to improve the maximum power transmission capacity of the key section under the condition of meeting safety has always been a difficult problem. With the continuous input of DC systems into the power grid, there is still a lack of comprehensive, in-depth and systematic method for maximizing the power transmission capacity of the key section. The existing technical research on the maximum power transmission capacity does not consider the influence of the input of the DC system on the original key AC transmission channel in the hybrid power grid under the condition of considering the static and dynamic constraints of the whole system. SUMMARY

[0004] In order to solve the problems in the prior art, the application provides a power optimization method for a power grid key section considering DC system input.

[0005] The technical scheme of the application is as follows:

[0006] A power optimization method for a power grid key section considering DC system input, the DC system inputting the power grid forms several power transmission channels including AC channels and DC channels on the power grid key section,

[0007] The power of each power transmission channel of the power grid key section under any AC / DC fault is not greater than the corresponding maximum power limit of each power transmission channel, the sum of the powers of the power transmission channels is kept maximum, and the power of the AC channel in the power transmission channel is the sum of the power of the AC channel before the input of the DC system and the power increment of the AC channel after the input of the DC system.

[0008] Preferably, for the power grid key section with n power transmission channels including m AC channels and n-m DC channels, the power P of the xth AC channel of the key section after the input of the DC system is x has the following expression:

[0009]

[0010] wherein,

[0011] wherein, P is the initial power of the xth AC channel of the key section before the DC system is put into operation; P di P is the power of the ith DC system put into operation; P is the power change of the xth AC channel of the key section after the ith DC system is put into operation, x = 1, 2, … m, m is the total number of AC channels, i = 1, 2, …, n-m, n-m is the total number of DC systems put into operation; P is the power change of the xth AC channel of the key section after the ith DC system is put into operation; P di P is the power change of the DC of the key section after the ith DC system is put into operation.

[0012] Preferably, for the key section of the power grid having n power transmission channels including m AC channels and n-m DC channels, the power P x and the power P di has the following expression:

[0013]

[0014] wherein, P is the opening distribution factor of the xth AC channel of the key section when the jth power transmission channel is disconnected corresponding to the zth AC / DC fault, z = 1, 2, …, Z, Z is the total number of AC / DC faults, j = 1, 2, …, n; P j P is the power reduction of the jth power transmission channel after the jth power transmission channel is disconnected; P xmax P is the maximum limit of the power of the xth AC channel of the key section; P dimax P is the maximum limit of the power of the ith DC put into operation.

[0015] Preferably, for the key section of the power grid having n power transmission channels including m AC channels and n-m DC channels, the opening distribution factor P has the following expression:

[0016]

[0017] wherein,

[0018] wherein, To correspond to the z-th AC / DC fault, the change in unit power at node c on the disconnected j-th transmission channel causes the power transfer distribution factor of the x-th AC channel to increase. To correspond to the z-th AC / DC fault, the unit power change at node d on the disconnected j-th transmission channel causes the power transmission distribution factor of the x-th AC channel to change. To correspond to the z-th AC / DC fault, the change in unit power at node c on the disconnected j-th transmission channel causes the power transmission distribution factor of the j-th AC channel to change. To correspond to the z-th AC / DC fault, the power transfer distribution factor of the j-th AC channel is caused by the unit power change of node d on the disconnected j-th transmission channel. To correspond to the z-th AC / DC fault, the mutual impedance between the starting node a of the x-th AC channel and the starting node c of the disconnected j-th transmission channel; To correspond to the z-th AC / DC fault, the mutual impedance between the starting node b of the x-th AC channel and the starting node c of the disconnected j-th transmission channel; To correspond to the z-th AC / DC fault, the mutual impedance between the starting node a of the x-th AC channel and the starting node d of the disconnected j-th transmission channel; To correspond to the z-th AC / DC fault, the mutual impedance between the starting node b of the x-th AC channel and the starting node d of the disconnected j-th transmission channel; X x Let X be the self-impedance of the x-th AC channel; j Let be the self-impedance of the j-th disconnected transmission channel.

[0019] Preferably, for a critical section of a power grid with n transmission channels including m AC channels and nm DC channels, the power P of the x-th AC channel of the critical section after the DC system is put into operation... x And the power P of the nmth DC system put into operation d(n-m) It has the following expression:

[0020]

[0021] Compared with the prior art, the present invention has the following beneficial effects.

[0022] The application provides a power optimization method for a power grid key section considering DC system input, in which the power of each power transmission channel of the power grid key section under any AC / DC fault is not greater than the corresponding maximum power limit of each power transmission channel, the sum of the powers of the power transmission channels is kept maximum, and the power of the AC channel in the power transmission channel is the sum of the power of the AC channel before the DC system input and the power increment of the AC channel after the DC system input. The method considers the influence of the DC system input on the power flow distribution of the power grid key section, can adapt to the complex and changeable operation mode of a large AC / DC hybrid power grid, and can provide reference for power grid dispatching operation mode arrangement and power generation plan making. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The flowchart of the power optimization method for the power grid key section considering the DC system input of the application is shown. DETAILED DESCRIPTION

[0024] The application will be further described below in combination with specific embodiments and corresponding drawings.

[0025] Embodiment one

[0026] The power optimization method for the power grid key section considering the DC system input of the example, in which, after the DC system input into the power grid, a plurality of power transmission channels including AC channels and DC channels are formed on the power grid key section, the power of each power transmission channel of the power grid key section under any AC / DC fault is not greater than the corresponding maximum power limit of each power transmission channel, the sum of the powers of the power transmission channels is kept maximum, and the power of the AC channel in the power transmission channel is the sum of the power of the AC channel before the DC system input and the power increment of the AC channel after the DC system input.

[0027] The power optimization method for the power grid key section of the application considers the influence of the DC system input on the power flow distribution of the power grid key section, can adapt to the complex and changeable operation mode of a large AC / DC hybrid power grid, and can provide reference for power grid dispatching operation mode arrangement and power generation plan making.

[0028] Embodiment two

[0029] The example is further designed based on embodiment one as follows: for the power grid key section with n power transmission channels including m AC channels and n-m DC channels, the power of the xth AC channel of the key section after the DC system input is P x has the following expression:

[0030]

[0031] wherein,

[0032] In the formula, The initial power of the xth AC channel of the key section before the DC system is put into operation; P di The power of the ith DC system put into operation; The power flow change sensitivity of the xth AC channel of the key section after the ith DC system is put into operation, x = 1, 2, … m, m is the total number of AC channels, i = 1, 2, …, n-m, n-m is the total number of DC systems put into operation; The power change amount of the xth AC channel of the key transmission section after the ith DC system is put into operation; ΔP di The power change amount of the DC of the key section of the power grid after the ith DC system is put into operation.

[0033] The power P of the xth AC channel of the key section after the DC system is put into operation x And the power P of the ith DC system put into operation di Has the following expression:

[0034]

[0035] In the formula, The opening distribution factor of the xth AC channel of the key section when the jth transmission channel is disconnected corresponding to the zth AC / DC fault, z = 1, 2, …, Z, Z is the total number of AC / DC faults, j = 1, 2, …, n; P j The power reduction amount of the jth transmission channel after the jth transmission channel is disconnected; P xmax The maximum limit of the power of the xth AC channel of the key section of the power grid; P dimax The maximum limit of the power of the ith DC put into operation.

[0036] The opening distribution factor of the xth AC channel of the key section when the jth transmission channel is disconnected corresponding to the zth AC / DC fault Has the following expression:

[0037]

[0038] In the formula,

[0039] In the formula, The power transmission distribution factor of the xth AC channel caused by the unit power change of the node c on the disconnected jth transmission channel corresponding to the zth AC / DC fault; The power transmission distribution factor of the xth AC channel caused by the unit power change of the node d on the disconnected jth transmission channel corresponding to the zth AC / DC fault; The power transmission distribution factor of the jth AC channel caused by the unit power change of the node c on the disconnected jth transmission channel corresponding to the zth AC / DC fault; a power transmission distribution factor of the jth AC channel corresponding to the zth AC-DC fault; a mutual impedance between the first end node a of the xth AC channel and the first end node c on the jth broken power transmission channel corresponding to the zth AC-DC fault; a mutual impedance between the first end node b of the xth AC channel and the first end node c on the jth broken power transmission channel corresponding to the zth AC-DC fault; a mutual impedance between the first end node a of the xth AC channel and the first end node d on the jth broken power transmission channel corresponding to the zth AC-DC fault; a mutual impedance between the first end node b of the xth AC channel and the first end node d on the jth broken power transmission channel corresponding to the zth AC-DC fault;X x is a self-impedance of the xth AC channel;X j is a self-impedance of the jth broken power transmission channel.

[0040] a power P of the xth AC channel of a key section of the power grid after the DC system is put into operation x and a power P of the n-mth DC system which is put into operation d(n-m) has the following expression:

[0041]

[0042] Embodiment Three:

[0043] This embodiment gives a simulation implementation process of the method of the application. The preset power grid key section has n power transmission channels including m AC channels and n-m DC channels. There are three kinds of AC-DC faults, which are respectively N-2 broken line AC fault corresponding to the same pole line, N-1 broken line AC fault corresponding to the non-same pole line and DC single pole blocking fault. The simulation implementation process includes the following specific steps:

[0044] s1) obtaining the power grid real-time operation power flow data information before and after the DC system is put into operation in advance, which includes the self-impedance, mutual impedance, branch impedance of each AC channel of the power grid key section, the number and rated power of the DC to be put into operation, and the maximum limit of each AC-DC channel power of the key power transmission section before the DC is put into operation.

[0045] s2) putting the DC system into the power grid in sequence, and calculating the power flow change sensitivity of the AC channel of the power grid key section after the DC system is put into operation and the breaking distribution factor of each AC channel of the power grid key section under each AC-DC fault form according to the obtained information;

[0046] wherein the power flow change sensitivity of the xth AC channel of the key section after the ith DC system is put into operation The calculation formula is as follows:

[0047]

[0048] In the formula, is the power change of the xth AC channel of the key power transmission section after the ith DC system is put into operation; ΔP di is the power change of the DC of the key section of the power grid after the ith DC system is put into operation.

[0049] The opening distribution factors of the AC channels of the key section of the power grid under the above three kinds of AC / DC faults are calculated respectively, wherein, corresponding to the zth AC / DC fault, the opening distribution factor of the xth AC channel of the key section when the jth power transmission channel is disconnected is has the following expression:

[0050]

[0051] In the formula,

[0052] In the formula, z is the sequence number of the AC / DC fault, z = 1, 2, 3; is the power transmission distribution factor of the xth AC channel caused by the unit power change of the node c on the disconnected jth power transmission channel corresponding to the zth AC / DC fault; is the power transmission distribution factor of the xth AC channel caused by the unit power change of the node d on the disconnected jth power transmission channel corresponding to the zth AC / DC fault; is the power transmission distribution factor of the jth AC channel caused by the unit power change of the node c on the disconnected jth power transmission channel corresponding to the zth AC / DC fault; is the power transmission distribution factor of the jth AC channel caused by the unit power change of the node d on the disconnected jth power transmission channel corresponding to the zth AC / DC fault; is the mutual impedance between the starting node a of the xth AC channel and the starting node c on the disconnected jth power transmission channel corresponding to the zth AC / DC fault; is the mutual impedance between the starting node b of the xth AC channel and the starting node c on the disconnected jth power transmission channel corresponding to the zth AC / DC fault; is the mutual impedance between the starting node a of the xth AC channel and the starting node d on the disconnected jth power transmission channel corresponding to the zth AC / DC fault; is the mutual impedance between the starting node b of the xth AC channel and the starting node d on the disconnected jth power transmission channel corresponding to the zth AC / DC fault; X x is the self-impedance of the xth AC channel; X j is the self-impedance of the disconnected jth power transmission channel.

[0053] s3) based on the calculated power flow change sensitivity and the breaking distribution factor, a power optimization model of each power transmission channel of the key section of the power grid is established with the maximum power transmission capacity of the key section of the power grid as the optimization target, and the optimization model is solved based on the stability limit constraint condition, and the power of each power transmission channel of the key section of the power grid is optimized and adjusted according to the output result.

[0054] wherein the power optimization model of each power transmission channel of the key section of the power grid is

[0055]

[0056] The stability limit constraint condition is

[0057]

[0058] wherein P x is the power of the xth AC channel of the key section after the DC system is put into operation; P di is the power of the ith DC system put into operation; is the breaking distribution factor of the xth AC channel of the key section when the jth power transmission channel is disconnected corresponding to the zth AC-DC fault, z = 1, 2, 3, j = 1, 2, …, n; P j is the power reduction amount of the jth power transmission channel after the jth power transmission channel is disconnected; P xmax is the maximum limit of the power of the xth AC channel of the key section of the power grid; P dimax is the maximum limit of the power of the ith DC put into operation.

[0059] In the above power optimization model and stability limit constraint condition, the power P x of the xth AC channel of the key section after the DC system is put into operation has the following expression:

[0060]

[0061] wherein, P0(x) is the initial power of the xth AC channel of the key section before the DC system is put into operation; P di is the power of the ith DC system put into operation; is the power flow change sensitivity of the xth AC channel of the key section after the ith DC system is put into operation, x = 1, 2, …, m, m is the total number of AC channels, i = 1, 2, …, n-m, n-m is the total number of DC systems put into operation.

Claims

1. A power optimization method for a power grid key section considering DC system input, wherein after the DC system is input into the power grid, several power transmission channels including AC channels and DC channels are formed on the power grid key section, and the method is characterized in that: the power of each power transmission channel of the power grid key section under any AC-DC fault is not greater than the maximum power limit of the corresponding power transmission channel, the sum of the powers of each power transmission channel is kept maximum, and the power of the AC channel in the power transmission channel is the sum of the power of the AC channel before the DC system is input and the power increment of the AC channel after the DC system is input; the method comprises the following specific steps: s1) obtaining in advance real-time operation power flow data information of the power grid before and after the DC system is input, which includes the self-impedance and mutual-impedance of the AC channel of the power grid key section, the branch impedance of each AC channel, the number and rated power of the DC input, and the maximum power limit of each AC-DC channel of the key power transmission section before the DC input; s2) inputting the DC system into the power grid in sequence, calculating the power flow change sensitivity of the AC channel of the power grid key section after the DC system is input and the opening distribution factor of each AC-DC fault form of the power grid key section according to the obtained information; s3) based on the calculated power flow change sensitivity and opening distribution factor, taking the maximum power transmission capacity of the power grid key section as the optimization target, establishing a power optimization model for each power transmission channel of the power grid key section, and solving the optimization model established above based on the stability limit constraint condition, and optimizing and adjusting the power of each power transmission channel of the power grid key section according to the output result. ​ ​ ​ for a critical section of an electrical network having n transmission channels comprising m alternating current channels and n-m direct current channels, a clearing distribution factor of an xth alternating current channel of the critical section when the jth transmission channel is opened for a zth alternating direct current fault has the following expression: wherein wherein, is the power transfer distribution factor of the xth AC channel corresponding to the zth AC-DC fault, caused by a unit power change at node c on the jth open DC transmission channel; is the power transfer distribution factor of the xth AC channel corresponding to the zth AC-DC fault, caused by a unit power change at node d on the jth open DC transmission channel; is the power transfer distribution factor of the jth AC channel corresponding to the zth AC-DC fault, caused by a unit power change at node c on the jth open DC transmission channel; is the power transfer distribution factor of the jth AC channel corresponding to the zth AC-DC fault, caused by a unit power change at node d on the jth open DC transmission channel; is the mutual impedance between the first end node a of the xth AC channel and the first end node c on the jth open DC transmission channel corresponding to the zth AC-DC fault; is the mutual impedance between the first end node b of the xth AC channel and the first end node c on the jth open DC transmission channel corresponding to the zth AC-DC fault; is the mutual impedance between the first end node a of the xth AC channel and the first end node d on the jth open DC transmission channel corresponding to the zth AC-DC fault; is the mutual impedance between the first end node b of the xth AC channel and the first end node d on the jth open DC transmission channel corresponding to the zth AC-DC fault;X x is the self-impedance of the xth AC channel;X j is the self-impedance of the jth open DC transmission channel; ​ 2. The method for power optimization of critical section of power grid considering DC system energizing according to claim 1, characterized in that: For a power grid critical section with n power transmission channels including m alternating current channels and n-m direct current channels, wherein the power P of the xth alternating current channel of the critical section after the direct current system is put into operation x has the following expression: wherein, In the formula, Pxi is the initial power of the xth AC channel of the key section before the DC system is put into operation; di P is the power of the ith DC system put into operation; is the power change of the xth AC channel of the key section after the ith DC system is put into operation, x = 1, 2, … m, m is the total number of AC channels, i = 1, 2, …, n-m, n-m is the total number of DC systems put into operation; is the power change of the xth AC channel of the key section after the ith DC system is put into operation, x = 1, 2, … m, m is the total number of AC channels, i = 1, 2, …, n-m, n-m is the total number of DC systems put into operation; di is the power change of the xth AC channel of the key section after the ith DC system is put into operation, x = 1, 2, … m, m is the total number of AC channels, i = 1, 2, …, n-m, n-m is the total number of DC systems put into operation; 3. The method for power optimization of critical section of power grid considering DC system energizing according to claim 2, characterized in that: For the power grid key section with n power transmission channels including m alternating current channels and n-m direct current channels, the power P of the xth alternating current channel of the key section after the direct current system is put into operation x and the power P of the ith direct current system put into operation di has the following expression: In the formula, Pzj is the open distribution factor of the key section xth AC channel when the jth power transmission channel is opened corresponding to the zth AC-DC fault, z = 1, 2, …, Z, Z is the total number of AC-DC faults, j = 1, 2, …, n; P j Pj is the power reduction amount of the jth power transmission channel after the jth power transmission channel is opened; xmax Pmaxx is the maximum limit of the power of the key section xth AC channel of the power grid; dimax Pmaxi is the maximum limit of the power of the ith DC to be put into.

4. The method for power optimization of critical section of power grid considering DC system energizing according to any one of claims 1-3, characterized in that: For the key section of the power grid with n power transmission channels including m alternating current channels and n-m direct current channels, the power P of the xth alternating current channel of the key section after the direct current system is put into operation x and the power P of the ith direct current system put into operation di has the following expression:

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