A DC frequency modulation controller control method for a multi-zone asynchronous interconnected power grid

Abstract

The present invention discloses a control method for a DC frequency modulation controller of a multi-partition asynchronous interconnected power grid, and belongs to the technical field of power system stability control. The method includes: constructing a DC frequency control model of a multi-partition asynchronous interconnected power grid; based on the DC frequency control model, obtaining a dynamic response equation of the system frequency; based on the dynamic response equation, obtaining a frequency steady-state deviation value of each partitioned power grid; and considering the disturbance type of each partitioned power grid, the frequency steady-state deviation value of each partitioned power grid, and whether the DC rectifier side and the inverter side between each partitioned power grid participate in frequency modulation, obtaining an optimal coordinated control strategy of the DC frequency modulation controller based on a traversal optimization algorithm; considering the influence of the droop parameter of the DC frequency modulation controller on the frequency steady-state deviation value, adjusting the droop parameter of the DC frequency modulation controller of the multi-partition asynchronous interconnected power grid based on a traversal optimization algorithm. The present invention provides a novel and effective technical solution for the frequency stability of a multi-partitioned DC asynchronous interconnected power grid.

Description

Technical Field

[0001] The invention belongs to the technical field of power system stability control, and in particular relates to a direct current frequency modulation controller control method for a multi-partition asynchronous interconnected power grid. Background Art

[0002] The DC asynchronous interconnection between multiple regional power grids has become an important trend. The isolation effect of DC improves the safety of large power grid operation, but it also restricts the mutual support capabilities between regional power grids in the event of a fault, affecting the safe and stable operation of the power grid frequency. With the continuous increase in the penetration rate of new energy, the inertia and primary frequency regulation capabilities of regional power grids are constantly decreasing, which will further aggravate the frequency instability risk of DC asynchronous interconnected power grids. Therefore, it is urgent to study a technical solution that can fully utilize the advantages of the DC transmission system, realize the sharing of frequency regulation reserve resources between regional power grids, and enable the DC system to actively participate in the frequency control of multi-region asynchronous interconnected power systems.

[0003] In the existing technology, although there have been a few studies on the participation of DC transmission systems in the frequency control of asynchronous interconnected multi-regional power grids, the specific principles and parameter setting methods of the proposed frequency control strategies lack sufficient theoretical support. In addition, there has been no successful case of using DC transmission systems to achieve frequency mutual support between multi-regional power grids in actual engineering applications. Summary of the invention

[0004] The purpose of the present invention is to provide a control method for a DC frequency modulation controller of a multi-zone asynchronous interconnected power grid, so as to ensure that the DC transmission system can more effectively participate in the frequency regulation and control of the multi-zone asynchronous interconnected power grid from the theoretical and methodological perspectives, and provide important technical support for ensuring the frequency stability of future power grids. The technical solution proposed in the present invention not only takes into account the actual needs of the multi-zone asynchronous interconnected power grid, but also deeply studies the coordinated control strategy of the DC frequency modulation controller based on inertia response and its parameter setting method, which has good innovation and practicality.

[0005] To achieve the above object, the present invention provides a control method for a DC frequency modulation controller of a multi-partition asynchronous interconnected power grid, the control method comprising: a coordinated control strategy and a parameter setting method; the control method comprising the following steps: S1, based on a DC frequency modulation response principle considering inertia response, constructing a DC frequency control model of a multi-partition asynchronous interconnected power grid;

[0006] S2. Under the DC frequency control model of the multi-zone asynchronous interconnected power grid, a dynamic response equation of the system frequency is obtained;

[0007] S3. Based on the dynamic response equation, the per-unit value of the frequency steady-state deviation of each sub-area power grid is obtained; and considering the disturbance type of each sub-area power grid, the per-unit value of the frequency steady-state deviation of each sub-area power grid, and whether the DC rectifier side and the inverter side between each sub-area power grid participate in frequency modulation, the optimal coordinated control strategy of the DC frequency modulation controller is obtained based on the ergodic optimization algorithm;

[0008] S4. Considering the influence of the droop parameter of the DC frequency modulation controller on the per-unit value of the frequency steady-state deviation, the droop parameter of the DC frequency modulation controller of the multi-partition asynchronous interconnected power grid is adjusted based on the ergodic optimization algorithm.

[0009] Further preferably, the dynamic response equation is:

[0010]

[0011] in, For regional power grid The per-unit value of the frequency deviation, i=1, 2, 3; and are the inertia time constant and load damping coefficient of the equivalent generator of regional power grid i respectively; k p12 and k d12 They represent the droop parameter and inertia parameter of the DC frequency modulation controller between regional power grid 1 and regional power grid 2 respectively; k p13 and k d13 They represent the droop parameter and inertia parameter of the DC frequency modulation controller between regional power grid 1 and regional power grid 3 respectively; k p23 and k d23 They represent the droop parameter and inertia parameter of the DC frequency modulation controller between the regional power grid 2 and the regional power grid 3 respectively; It is the rectifier side between regional power grid 1 and regional power grid 2; It is the inverter side between regional power grid 1 and regional power grid 2; It is the rectifier side between regional grid 1 and regional grid 3; The inverter side between regional grid 1 and regional grid 3; It is the rectifier side between regional power grid 2 and regional power grid 3; It is the inverter side between regional grid 2 and regional grid 3; P 0dc12 , P 0dc13 and P 0dc23 They represent the reference values ​​of steady-state transmission power of the DC system between regional grid 1 and regional grid 2, between regional grid 1 and regional grid 3, and between regional grid 2 and regional grid 3 respectively; ΔP mi and ΔP Li They represent the per-unit value of the mechanical power variation provided by the equivalent synchronous generator of regional power grid i and the per-unit value of the system load power variation; PSi is the rated capacity of equivalent synchronous generators in regional power grid i.

[0012] Further preferably, when a disturbance occurs randomly in each sub-area power grid, the quantitative expression of the per-unit value of the frequency steady-state deviation of each sub-area power grid is:

[0013]

[0014] Where Δf si represents the per-unit value of the frequency steady-state deviation of regional power grid i; B i represents the frequency deviation coefficient of regional power grid i, where B i = 1 / R i + D i , R i It represents the speed regulation parameters of the equivalent synchronous generator speed regulator of regional power grid i.

[0015] Further preferably, when a random disturbance occurs in the DC blocking between the sub-area power grids, the quantized expression of the per-unit value of the frequency steady-state deviation of each sub-area power grid is:

[0016]

[0017] Where Δf si represents the per-unit value of the frequency steady-state deviation of regional power grid i; B i represents the frequency deviation coefficient of regional power grid i, where B i = 1 / R i + D i , R i represents the speed regulation parameters of the synchronous generator speed regulator of the regional power grid i; represents the DC blocking disturbance between regional power grid i and regional power grid j, where i <j,N ij ∈[0, 1], N ij It represents the ratio of the actual steady-state power transfer between regional grid i and regional grid j to the preset reference value.

[0018] Further preferably, the process of obtaining the optimal coordinated control strategy of the DC frequency modulation controller based on the ergodic optimization algorithm includes:

[0019] Determine the disturbance type and initialize the binary values ​​of parameters q1, q2, q3, q4, q5, and q6 to Q=000000;

[0020] Construct the coefficient matrix M or N and start traversing all values ​​of Q;

[0021] By solving the linear equation, the per-unit value of the steady-state deviation of the power grid frequency in each partition corresponding to the current Q value and the root mean square of the actual value of the steady-state deviation of the power grid frequency in each partition are calculated; the calculation equation for the root mean square of the actual value of the steady-state deviation of the power grid frequency in each partition is:

[0022] ,

[0023] Where n represents the total number of asynchronously interconnected regional power grids; Δf si represents the per-unit value of the frequency steady-state deviation of regional power grid i; F0 represents the rated frequency;

[0024] Record the current Q value, compare and record the minimum RMS value and the Q value corresponding to the minimum RMS value;

[0025] Completed arrive All possible binary combinations of Q output the minimum root mean square, and the optimal coordinated control parameter combination of the DC frequency modulation controller corresponding to Q, wherein the optimal coordinated control parameter combination is a combination of the values ​​of q1, q2, q3, q4, q5, and q6 corresponding to Q.

[0026] Further preferably, the S4 includes:

[0027] S41, based on the optimal coordinated control strategy and state space equation of the DC frequency modulation controller, analyzing the influence of the parameters of the DC frequency modulation controller on the system stability;

[0028] S42. Considering the influence of the DC frequency modulation controller parameters on the quantitative expression of the per-unit value of the frequency steady-state deviation, a droop parameter setting value is obtained based on an ergodic optimization algorithm.

[0029] Further preferably, the state space equation comprises:

[0030] ,

[0031] Where A and B represent the system matrix and input matrix respectively; represents the state vector; u represents the input vector; superscript represents the derivation;

[0032] With given parameter values, the state space equation is transformed into:

[0033]

[0034] in, , , are the per unit values ​​of the frequency deviation of regional power grid 1 , per unit value of frequency deviation of regional power grid 2 , per unit value of regional power grid 3 frequency deviation , , , They are respectively the per-unit value of mechanical power provided by the equivalent synchronous generator of regional power grid 1, the per-unit value of mechanical power provided by the equivalent synchronous generator of regional power grid 2, and the per-unit value of mechanical power provided by the equivalent synchronous generator of regional power grid 3; and They represent the droop parameter and inertia parameter of the DC frequency modulation controller respectively.

[0035] Further preferably, the method for obtaining the droop parameter setting value based on the ergodic optimization algorithm includes:

[0036] Input the frequency deviation coefficient of each regional power grid, the rated capacity of equivalent synchronous generators, the steady-state DC power transmitted between regional power grids, inertia parameters, and set fixed values ​​of q1 to q6 based on the optimal coordinated control strategy;

[0037] Determine the droop parameter k p The value range of k is set and the parameters are initialized, the system matrix is ​​constructed, the root mean square of the actual value of the steady-state deviation of the power grid frequency in each partition is calculated, and the difference between different k p The root mean square of the actual value of the frequency steady-state deviation corresponding to the value, identify the minimum root mean square value and the corresponding optimal k p value.

[0038] Compared with the prior art, the present invention has certain innovation. First, the present invention has made beneficial explorations and attempts to address the problem of insufficient research in the field of frequency coordination control of multi-partitioned asynchronous interconnected power grids. Secondly, the present invention innovatively proposes a quantitative expression of the per-unit value of the frequency steady-state deviation of a multi-partitioned asynchronous interconnected power grid considering inertia response and its calculation method, which lays a theoretical foundation for the subsequent control strategy design. On this basis, the present invention further develops a coordinated control strategy and parameter setting method of a DC frequency modulation controller for a multi-partitioned asynchronous interconnected power grid based on a traversal optimization algorithm. Finally, through simulation experiments, the present invention verifies the feasibility and effectiveness of the proposed DC frequency modulation controller coordinated control technical solution, proving that the solution can significantly improve the overall frequency characteristics of each partition of the interconnected power grid and improve the system operation performance. In summary, the present invention has made a certain degree of progress in the field of frequency coordination control of multi-partitioned asynchronous interconnected power grids, has better solved the deficiencies of the prior art, and has provided a novel and effective technical solution for achieving frequency stability of the interconnected power grid, which has a relatively broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] Figure 1 It is a flow chart of a control method of a DC frequency modulation controller for a multi-zone asynchronous interconnected power grid according to an embodiment of the present invention;

[0041] Figure 2 It is a schematic diagram of the inertia and droop coordinated control principle of an embodiment of the present invention;

[0042] Figure 3 This is a transfer function block diagram of a thermal power unit i in a regional power grid according to an embodiment of the present invention;

[0043] Figure 4 This is a transfer function block diagram of a hydropower unit i in a regional power grid according to an embodiment of the present invention;

[0044] Figure 5 It is a block diagram of a DC frequency response model of region 1 of an embodiment of the present invention;

[0045] Figure 6 This is a block diagram of a DC frequency response model of a multi-zone asynchronous interconnected power grid according to an embodiment of the present invention;

[0046] Figure 7 This is a flow chart of a coordinated control strategy of a DC frequency modulation controller for a multi-zone asynchronous interconnected power grid according to an embodiment of the present invention;

[0047] Figure 8 This is a schematic diagram of the configuration of state measurement points of a control system according to an embodiment of the present invention;

[0048] Fig. 9 A distribution characteristic diagram of system characteristic values ​​under the control strategy described in the embodiment of the present invention;

[0049] Fig.10 A curve diagram showing the relationship between the root mean square of the steady-state deviation value of the power grid frequency in each subarea and the droop coefficient in an embodiment of the present invention;

[0050] Fig.11 The figure is a simulation result diagram of the frequency dynamic response of the DC frequency modulation controller under the optimal coordinated control strategy according to the embodiment of the present invention; wherein (a) is a simulation result diagram of scenario 1; (b) is a simulation result diagram of scenario 2;

[0051] Fig.12Schematic diagram of the comparison results of the frequency dynamic response of the DC frequency modulation controller using four different control modes in scenario 1 according to an embodiment of the present invention; (a) is a schematic diagram of the comparison results of regional power grid 1; (b) is a schematic diagram of the comparison results of regional power grid 2; (c) is a schematic diagram of the comparison results of regional power grid 3;

[0052] Fig.13 Schematic diagram of the comparison results of the frequency dynamic response of the DC frequency modulation controller using four different control modes in scenario 2 according to an embodiment of the present invention; (a) is a schematic diagram of the comparison results of regional power grid 1; (b) is a schematic diagram of the comparison results of regional power grid 2; (c) is a schematic diagram of the comparison results of regional power grid 3;

[0053] Fig.14 Schematic diagram of the comparison results of the frequency dynamic response of the DC frequency modulation controller using different parameters in scenario 1 according to an embodiment of the present invention; (a) is a schematic diagram of the comparison results of regional power grid 1; (b) is a schematic diagram of the comparison results of regional power grid 2; (c) is a schematic diagram of the comparison results of regional power grid 3;

[0054] Fig.15 The diagram is a comparison diagram of the frequency dynamic response of the DC frequency modulation controller using different parameters in scenario 2 according to an embodiment of the present invention; (a) is a comparison diagram of the regional power grid 1; (b) is a comparison diagram of the regional power grid 2; and (c) is a comparison diagram of the regional power grid 3. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0057] Embodiment 1:

[0058] like Figure 1 As shown, this embodiment provides a method for controlling the frequency of a multi-regional power grid with direct current asynchronous interconnection. The control method includes: a coordinated control strategy and a parameter setting method.

[0059] The coordinated control strategy includes the following steps: First, the DC frequency modulation controller adopts inertia and droop coordinated control. The inertia and droop coordinated control principle is as follows: Figure 2 shown.

[0060] In DC frequency modulation control, the output DC power expression is:

[0061] , (1)

[0062] in, represents the per-unit value of the frequency deviation of the regional power grid, where: , and They are the per-unit value of the current value of the frequency deviation of the power grid system and the per-unit value of the rated value; and They represent the droop parameter and inertia parameter of the DC frequency modulation controller respectively; Indicates the enable terminal of DC frequency modulation control, and its value is between 0 and 1, which is used to control whether the frequency of the rectifier side or inverter side of each DC line is included in the frequency modulation control; and They respectively represent the reference value and actual value of the steady-state power transmission of the DC system.

[0063] Among them, the transfer function block diagrams of thermal power units and hydropower units participating in frequency regulation are as follows: Figure 3 and Figure 4 As shown. is the per-unit value of the frequency deviation of regional power grid i, i=1, 2, 3; is the speed control parameter of the thermal power unit speed regulator, is the time constant of its servo motor, is the steam volume time constant of its reheat turbine, is the reheater time constant, is the power per unit value of its high voltage stage, is the installed capacity proportion of thermal power plants in regional power grid i, ΔP mTi The per unit value of the mechanical power variation provided by the thermal power unit i in the regional power grid; is the speed regulation parameter of the hydropower unit speed regulator, is the water hammer time constant, is the time constant of its servo motor, is the time constant of its leading link, is the time constant of its lag link, is the installed capacity proportion of hydropower in regional power grid i, ΔP mHi The per unit value of the mechanical power variation provided by the i hydropower unit in the regional power grid; ΔP mi The per-unit value of the mechanical power variation provided by the equivalent synchronous generator of regional power grid i is equal to the sum of the power provided by the thermal power units and hydropower units in the regional power grid.

[0064] The DC frequency response model of area 1 is built based on the DC frequency modulation principle considering inertia response. The DC frequency response model of area 1 is as follows: Figure 5 shown. is the reference value of the per-unit value of the system frequency deviation, H1 and D1 are the inertia time constant and load damping coefficient of the equivalent generator of regional power grid 1, respectively, S1 represents the rated capacity of the equivalent synchronous generator in regional grid 1, ΔP L1 Indicates the per-unit value of the system load power change. The DC system adopts the second-order equivalent model of the ±800kV UHV DC engineering system. is the damping ratio of the second-order system, is the natural frequency, s is the Laplace operator, which represents the frequency variable in the complex frequency domain. The constructed second-order system is as follows:

[0065] , (2)

[0066] Droop control mainly responds to the deviation of the system frequency, thereby participating in the primary frequency modulation of the system; inertia control mainly responds to the differential of the system frequency, thereby providing inertia support to the system. In order to simplify the analysis, this embodiment ignores the influence of the filtering link, dead zone link and power limiting link in the DC frequency modulation control. At the same time, considering that the DC frequency modulation control has the ability to quickly adjust active power at the millisecond level, and the time scale of the power system frequency modulation process is at the second level, the adjustment time of the DC system is ignored. In addition, this embodiment does not take into account the uncertainty of renewable energy generation and its impact on frequency modulation control.

[0067] like Figure 6 As shown in the figure, it is a block diagram of the DC frequency control model of the three-division asynchronous interconnected power grid. For a three-division DC asynchronous interconnected power grid, let one of the divisional grids be regional grid i, i=1, 2, 3, (abbreviated as region i in the figure). The rotor motion equation of the regional grid i is:

[0068] , (3)

[0069] in, and Regional power grid Equivalent generator inertia time constant and load damping factor; and For regional power grid The per-unit value of the frequency deviation and the per-unit value of the total deviation on the power side.

[0070] In a three-regional DC asynchronous interconnected power grid, regional grid 1 transmits power to regional grid 2, regional grid 2 transmits power to regional grid 3, and regional grid 1 transmits power to regional grid 3. Different frequency regulation control strategies can be adopted for the DC between the three grids, including three control strategies: rectifier side, inverter side, and double-side frequency regulation. arrive The value of varies between 1 and 0, corresponding to whether the frequency of the rectifier side and the inverter side of each DC line is included in the frequency modulation control. Specifically, Corresponding to the rectifier side between regional grid 1 and regional grid 2, Corresponding to the inverter side between regional grid 1 and regional grid 2, Corresponding to the rectifier side between regional grid 1 and regional grid 3, Corresponding to the inverter side between regional grid 1 and regional grid 3, Corresponding to the rectifier side between regional grid 2 and regional grid 3, Corresponding to the inverter side between regional power grid 2 and regional power grid 3.

[0071] The per unit value of the total power side deviation of each sub-grid of the three-division DC asynchronous interconnected power grid is:

[0072] (4)

[0073] Among them, P mi and ΔP mi They represent the per-unit value of the mechanical power and the per-unit value of the mechanical power variation provided by the equivalent synchronous generator of regional power grid i respectively; P Li and ΔP Li They represent the per unit value of the system load power and the per unit value of the system load power variation of the regional power grid i respectively; P Si represents the rated capacity of the equivalent synchronous generator of regional power grid i; P dc12 , P dc13 and P dc23 They respectively represent the actual values ​​of the steady-state transmission power of the DC systems between regional grids 1 and 2, between regional grids 1 and 3, and between regional grids 2 and 3; before the disturbance occurs, for each regional grid, the per-unit value of the mechanical power provided by its equivalent synchronous generator, the per-unit value of the system load power and the actual value of the steady-state transmission power of the connected DC system satisfy a balanced relationship, so that the system frequency of each regional grid operates at the nominal value of 50 Hz.

[0074] Among them, the actual value of the steady-state transmission power of the DC system between the power grids is:

[0075] (5)

[0076] Among them, P 0dc12 , P 0dc13 and P 0dc23 k represents the steady-state transmission power reference values ​​of the DC systems between regional grid 1 and regional grid 2, between regional grid 1 and regional grid 3, and between regional grid 2 and regional grid 3 respectively; pij and k dijThey represent the droop parameter and inertia parameter of DC ij, respectively, where DC ij is the DC between regional grid i and regional grid j (i <j);k p12 and k d12 They represent the droop parameter and inertia parameter of the DC frequency modulation controller between regional power grid 1 and regional power grid 2 respectively; k p13 and k d13 They represent the droop parameter and inertia parameter of the DC frequency modulation controller between regional power grid 1 and regional power grid 3 respectively; k p23 and k d23 They respectively represent the droop parameters and inertia parameters of the DC frequency modulation controller between the regional power grid 2 and the regional power grid 3.

[0077] Then the dynamic response equation of the frequency of each partition power grid system is obtained:

[0078] (6)

[0079] After the DC is introduced into the frequency modulation control, the system inertia and system damping of the regional power grid are increased. In this embodiment, the regional power grid 1 is taken as an example, and the situations of the regional power grids 2 and 3 are similar.

[0080] The system inertia increases as follows:

[0081] , (7)

[0082] in, Indicates the increase in system inertia of regional power grid 1.

[0083] System damping is increased as follows:

[0084] , (8)

[0085] in, Represents the increase in system damping of regional power grid 1.

[0086] It can be seen that the DC frequency modulation controller adopts inertia and droop coordinated control to provide support for the system frequency from two aspects of system inertia and system damping.

[0087] Case 1: If all three regional power grids have random disturbances at a certain moment, according to the previous formula (6), after the frequency regulation process of all regional power grids is completed, the speed regulation system of the equivalent synchronous generator set reaches a steady state. At this time, the frequency change rate of each sub-grid power grid is 0, and the per-unit value of the frequency steady-state deviation of each sub-grid power grid is:

[0088] (9)

[0089] Where Δf si represents the per-unit value of the frequency steady-state deviation of regional power grid i; Bi represents the frequency deviation coefficient of regional power grid i, where B i Equal to 1 / R i + D i , R i It represents the speed regulation parameters of the equivalent synchronous generator speed regulator of regional power grid i.

[0090] make , , , , , , we can get the following matrix equation:

[0091] . (10)

[0092] Let the 3*3 matrix on the left side of the above equation be the coefficient matrix M, and the vector is the per-unit value vector F of the frequency steady-state deviation, and the vector is the disturbance vector E. According to Cramer's law, the per-unit value of the frequency steady-state deviation of each sub-grid is obtained:

[0093] (11)

[0094] Among them, |M| is the value of the determinant of the coefficient matrix, |M i | means replace the i-th column with The value of the determinant calculated later.

[0095] Case 2: If the DC blocking disturbances between the three regional power grids are random, assume that the regional power grid and regional power grids The DC blocking disturbance between is: , , , no disturbance occurred in the power grid of each sub-area, that is, , the per unit value of the frequency steady-state deviation of each sub-area power grid is obtained as:

[0096] (12)

[0097] make = , = , = , = , = , = , we can get the matrix equation of the per-unit value of the steady-state frequency deviation of each partition power grid when the DC blocking disturbance occurs:

[0098] . (13)

[0099] Let the 3*3 matrix on the left side of the above equation be the coefficient matrix N, and the vector is the per-unit value vector F of the frequency steady-state deviation, and the vector is the disturbance vector E1, and according to Cramer's law, the per-unit value of the frequency steady-state deviation of each sub-grid is obtained:

[0100] (14)

[0101] Among them, |N| is the value of the determinant of the coefficient matrix, |N i | means replace the i-th column with The value of the determinant calculated later.

[0102] This embodiment considers that different frequency modulation control strategies can be adopted for the DC lines between the three partitioned power grids based on the traversal optimization algorithm. Each DC line can be frequency-controlled on the rectifier side, the inverter side, or both sides. The DC frequency modulation controller coordinated control strategy process is as follows: Figure 7 As shown, the specific process is as follows:

[0103] (1) Determine the disturbance type and initialize relevant parameters.

[0104] (2) Construct the corresponding coefficient matrix or .

[0105] (3) Initialize the binary value Q = 000000 of q1, q2, q3, q4, q5, and q6. Each loop controls the value of a binary variable q, and the value of q is between 0 and 1. Start traversing all the values ​​of Q.

[0106] (4) By solving the linear equation, the per-unit value of the steady-state frequency deviation of each sub-area power grid corresponding to the current Q value and the root mean square of the actual value of the steady-state frequency deviation of each sub-area power grid are calculated; the root mean square calculation equation of the actual value of the steady-state frequency deviation of each sub-area power grid is:

[0107] , (15)

[0108] Where n represents the total number of asynchronously interconnected regional power grids; F0 is the rated frequency.

[0109] (5) Record the current Q value, compare and record the minimum RMS and the Q value corresponding to the minimum RMS.

[0110] (6) Complete the traversal arrive All possible binary combinations of , a total of 64 combinations. Output minimum RMS, and the optimal coordinated control parameter combination of the DC frequency modulation controller corresponding to Q, that is, the combination of the values ​​of q1, q2, q3, q4, q5, q6 corresponding to Q.

[0111] This embodiment also proposes a method for setting droop parameters of DC frequency modulation control of a multi-partition asynchronous interconnected power grid considering inertia response, including:

[0112] (1) The coordinated control of the DC frequency modulation controller can effectively improve the frequency characteristics of the power grid. However, since the virtual inertia control introduces the derivative component, it is necessary to further analyze the stability of the power grid.

[0113] This embodiment uses state space equations to analyze the coordinated control strategy of the DC frequency modulation controller based on the inertia and droop coordinated control method. The state space equation is expressed as:

[0114] , (16)

[0115] Where A and B represent the system matrix and input matrix respectively; represents the state vector; u represents the input vector; superscript Indicates derivative.

[0116] In this embodiment, the per unit value of the frequency deviation of the regional power grid 1 is defined as , per unit value of frequency deviation of regional power grid 2 , per unit value of regional power grid 3 frequency deviation They are , , The per-unit values ​​of the mechanical power provided by the equivalent synchronous generators of regional power grid 1, the per-unit values ​​of the mechanical power provided by the equivalent synchronous generators of regional power grid 2, and the per-unit values ​​of the mechanical power provided by the equivalent synchronous generators of regional power grid 3 are respectively , , , the control system state measurement point configuration diagram is as follows Figure 8 As shown; and They represent the droop parameter and inertia parameter of the DC frequency modulation controller respectively.

[0117] With the above parameter settings, the state space equation is transformed into:

[0118] (17)

[0119] In this embodiment, the matrix is ​​obtained by solving the equation, and the 6 characteristic roots of the matrix are calculated using MATLAB software, and the characteristic roots are plotted as k increases. pand k d The distribution diagram of the changes, with triangles and circles marking k respectively. p and The eigenvalues ​​tend to 0 and positive infinity, such as Fig. 9 shown.

[0120] This embodiment proves that under given parameter values, when a DC frequency modulation control strategy based on droop and inertia control is adopted, the frequency output of each zone power grid in the three-zone asynchronous interconnected power system can maintain asymptotic stability.

[0121] This embodiment shows that the designed control strategy can effectively coordinate the frequencies of various asynchronous partitions, ensure that the system can operate stably after disturbances, and maintain the frequency quality of the power grid. At the same time, this also provides a certain flexibility for the selection of DC frequency coordination control parameters in engineering practice, so that parameter adjustment will not have a negative impact on system stability. Although under given conditions, the values ​​of the DC frequency coordination control proportional coefficient and differential coefficient do not affect the stability of the system, in order to obtain better control performance, the setting of parameters still needs to be further optimized.

[0122] (2) Theoretical method for droop parameter adjustment.

[0123] The first stage, parameter input and initialization:

[0124] Input the frequency deviation coefficients B1, B2 and B3 of each region, and the rated capacity P of the equivalent synchronous generators in each region. S1 , P S2 and P S3 , steady-state DC power reference value P between regions 1 and 2 0dc12 , steady-state DC power reference value P between areas 1 and 3 0dc13 The reference value of the steady-state DC power transmission between areas 2 and 3 is P 0dc23 , inertia parameter k d The above parameters are all given or calculated by the previous steps of the present invention. Based on the optimal coordinated control strategy of the frequency modulation controller proposed by the present invention, a set of fixed q values ​​is set. Determine the droop parameter k p The value range of the calculation result storage array is initialized, and the root mean square value of the actual value of the minimum frequency deviation and the optimal k are set. p The initial value of the value.

[0125] The second stage is model solving and calculation:

[0126] The system matrix M is constructed using formula (10) of the present invention, and then formulas (11) and (15) are used to calculate the per-unit value of the frequency steady-state deviation of each regional power grid and the root mean square of the actual value of the frequency steady-state deviation.

[0127] The third stage, result analysis and optimization:

[0128] In this embodiment, the droop parameter k is traversed p All possible values ​​of value, compared with k p The root mean square of the actual value of the frequency deviation corresponding to the value is used to identify the minimum root mean square value and record the corresponding optimal k p Value. Plot k p The relationship curve between the RMS value is as follows: Fig.10 Given the above parameter values, it is finally determined that when k p =114, the corresponding minimum RMS is approximately 0.0833.

[0129] Embodiment 2:

[0130] In order to verify the correctness of the quantitative expression of the frequency steady-state deviation value, the coordinated control strategy of the DC frequency modulation controller of the multi-partition asynchronous interconnected power grid and the effectiveness of the droop parameter setting method, this embodiment builds a DC frequency control model of the three-partition asynchronous interconnected power grid in MATLAB / Simulink for simulation analysis.

[0131] First, set the parameter values ​​of the three-zone asynchronous interconnected power grid. The reference value of the per-unit value of the system frequency deviation 0. Rated capacity of equivalent synchronous generators in regional power grid 1 The equivalent synchronous generator provides a mechanical power of 55GW, the system load power is 20GW, and the inertia time constant of the equivalent synchronous generator is For 4 seconds, the load damping factor 1; Rated capacity of equivalent synchronous generators in regional power grid 2 The equivalent synchronous generator provides a mechanical power of 70GW, the system load power is 90GW, and the inertia time constant of the equivalent synchronous generator is For 4 seconds, the load damping factor 1; Rated capacity of equivalent synchronous generators in regional power grid 3 The equivalent synchronous generator provides a mechanical power of 25GW, the system load power is 40GW, and the inertia time constant of the equivalent synchronous generator is For 4 seconds, the load damping factor =1; the reference value P of the steady-state transmission power of the DC system between regional grid 1 and regional grid 2 0dc12 The reference value of the steady-state transmission power of the DC system between regional grid 1 and regional grid 3 is P 0dc13 The reference value P of the steady-state transmission power of the DC system between regional grid 2 and regional grid 3 is 10GW. 0dc23 5GW; DC frequency modulation control initial droop parameters Set to 10, the initial inertia parameter Set to 10, the inertia control low-pass filter time constant is 0.2 seconds; the speed control parameters of the thermal power unit speed regulator is 0.04, and the time constant of the servo motor is 0.2 seconds, and the steam volume time constant of the reheat turbine is The reheater time constant is 0.3 seconds. 7 seconds and the power per unit value of its high voltage level is 0.3, and the installed capacity of thermal power plants in regional grid 1, regional grid 2 and regional grid 3 accounts for , and are 0.5, 0.6 and 0.8 respectively; the speed regulation parameters of the speed regulator of the hydropower unit is 0.04, and the time constant of the servo motor The water hammer time constant is 0.2 seconds. is 1.2 seconds, and its leading link time constant is 5, and the time constant of its lag link is The installed capacity of hydropower generators in regional grid 1, regional grid 2 and regional grid 3 accounts for 38 seconds. , and The damping ratio of the second-order DC system is 0.5, 0.4 and 0.2 respectively. =0.59, natural frequency =17.

[0132] The equivalent speed regulation parameter R of the equivalent synchronous generator speed regulator of regional power grid i is i The calculation formula is:

[0133] . (18)

[0134] Based on the above optimal frequency regulation control strategy, consider scenario 1: the load of regional grid 1 suddenly drops by 10GW and scenario 2: there is a 10GW DC interlocking scenario between regional grid 1 and regional grid 2, and compare the frequency steady-state deviation value and its RMS value calculated based on formula (11) and formula (14) with the simulation results of the model built by Simulink. Initial droop parameters of DC frequency regulation Set to 20, and = = = , initial inertia parameters Set to 20, and = = = , and the other parameters are consistent with the above. The simulation results of the frequency dynamic response of the DC frequency modulation controller under the optimal coordinated control strategy obtained by model simulation are shown in Table 1 and Fig.11 As shown, ΔF s is the RMS value of the actual value of the steady-state deviation of the grid frequency in each partition, ΔF si is the actual value of the steady-state frequency deviation of regional power grid i.

[0135] Table 1

[0136]

[0137] In this embodiment, in two scenarios, a sudden load reduction of 10GW in regional grid 1 and a 10GW DC interlock between regional grid 1 and regional grid 2, the DC frequency modulation controller uses four control modes, namely, no frequency modulation control, only inertia control, only droop control, and inertia and droop coordinated control, for simulation comparison. The results are as follows: Fig.12 and Fig.13 The system frequency peak deviation and frequency steady-state deviation values ​​and their improvement values ​​and improvement rates under the two scenarios are shown in Table 2 and Table 3, respectively, where ΔI Fs is the improvement value of the root mean square of the actual value of the steady-state deviation of the grid frequency in each partition, IR Fs is the improvement rate of the root mean square of the actual value of the steady-state deviation of the grid frequency in each partition, ΔI Fp is the improvement value of the root mean square of the actual value of the peak frequency deviation of each partition, IR Fp is the improvement rate of the root mean square of the actual value of the peak frequency deviation of each partition, ΔF p It represents the root mean square of the actual value of the peak frequency deviation of each partition.

[0138] In scenario 1, when a 10GW load power reduction occurs in regional power grid 1:

[0139] For the disturbed regional power grid 1, when droop control and inertia control are not adopted, the DC system does not respond to changes in system frequency, the DC transmission power remains unchanged, and it cannot participate in system frequency regulation, resulting in the worst frequency characteristics of regional power grid 1.

[0140] When only inertia control is used, the peak frequency deviation of regional power grid 1 can be improved, but its frequency steady-state value has no significant effect.

[0141] For the supporting regional grids 2 and 3, when inertia and droop coordinated control is adopted, the frequency growth of regional grid 1 is suppressed by increasing the DC power transmission to these two regions, but it also leads to an increase in the frequency steady-state deviation value of regional grids 2 and 3.

[0142] When inertia and droop coordinated control is adopted, the improvement effect on the system frequency peak deviation and steady-state value deviation is the most significant. Compared with only droop control, it can reduce the rate of change of the system frequency of regional power grid 1, provide more time for the regulation of traditional synchronous generators, and at the same time reduce the amplitude of the peak frequency deviation of regional power grid 1 system and the regulation amplitude of DC power, thereby improving the regulation capability and range of DC frequency regulation control.

[0143] Taking into account the frequency performance of each sub-grid, the coordinated control of inertia and droop can more effectively improve the root mean square of the frequency peak deviation and the frequency steady-state deviation compared with other control methods.

[0144] Table 2

[0145]

[0146] In scenario 2, when a 10GW DC block occurs between regional grid 1 and regional grid 2:

[0147] For the disturbed regional grid 1 and regional grid 2, their frequency performance under different control strategies is similar to that of the disturbed party in the first scenario.

[0148] After adopting the inertia and droop coordinated control, the frequency peak deviation value and frequency steady-state deviation value of regional grid 1 and regional grid 3 are improved.

[0149] For the supporting regional grid 3, when inertia and droop coordinated control is adopted, the frequency deviation of regional grids 1 and 2 is suppressed by increasing the total DC power transmitted to regional grid 3, but it also leads to an increase in the frequency steady-state deviation value of regional grid 3.

[0150] Taking into account the frequency performance of each regional power grid, the use of inertia and droop coordinated control can more effectively improve the root mean square of the frequency peak deviation value and the frequency steady-state deviation value compared with other control methods, and the improvement effect on the disturbed regional power grid 1 and regional power grid 2 is significant.

[0151] Table 3

[0152]

[0153] This embodiment also provides a scheme for verifying the effectiveness of the droop parameter setting method.

[0154] In this scheme, MATLAB / Simulink is used to build a multi-partition asynchronous interconnected power grid model, and three schemes are designed: non-frequency modulation control, inertia and droop coordinated control with the initial parameters of the controller, and inertia and droop coordinated control with the parameters adjusted by the present invention. Through simulation experiments, the comparison results of the system frequency dynamic response of each scheme in scenario 1 and scenario 2 are obtained, as shown in Figure 2. Fig.14 and Fig.15 Table 4 records the root mean square value ΔF of the actual value of the steady-state deviation of the grid frequency in each partition under different combinations. s , and its improvement value ΔI Fs and improvement rate IR Fs ; The root mean square of the actual value of the peak frequency deviation of each partition grid ΔF p , and its improvement value ΔI Fp and improvement rate IR Fp .

[0155] In the above scenario 1, the verification results show that when k p =114, k d =10, the minimum RMS value of the actual value of the frequency steady-state deviation is 0.0833, which is consistent with the calculation result of this method. p =10, k d =10, the RMS values ​​of the actual value of the frequency steady-state deviation and the actual value of the frequency peak deviation increased by 26.37% and 7.51% respectively.

[0156] In the above scenario 2, when k p =114, k d =10, compared with the initial value k p =10, k d While keeping the same condition, the RMS value of the actual value of the frequency steady-state deviation and the RMS value of the actual value of the frequency peak deviation increased by 50.36% and 44.20% respectively.

[0157] The above simulations have verified that the parameter setting method proposed in this embodiment can significantly improve the frequency dynamic response characteristics of the system, effectively improve the performance of DC frequency modulation control, and show good adaptability and superiority in different application scenarios.

[0158] Table 4

[0159] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A control method for a DC frequency modulation controller of a multi-partition asynchronous interconnected power grid, characterized in that: The control method comprises: a coordinated control strategy and a parameter setting method; the control method comprises the following steps: S1. Based on the DC frequency modulation response principle considering inertia response, a DC frequency control model of multi-zone asynchronous interconnected power grid is constructed; S2. Under the DC frequency control model of the multi-zone asynchronous interconnected power grid, a dynamic response equation of the system frequency is obtained; S3. Based on the dynamic response equation, the per-unit value of the frequency steady-state deviation of each sub-area power grid is obtained; and considering the disturbance type of each sub-area power grid, the per-unit value of the frequency steady-state deviation of each sub-area power grid, and whether the DC rectifier side and the inverter side between each sub-area power grid participate in frequency modulation, the optimal coordinated control strategy of the DC frequency modulation controller is obtained based on the ergodic optimization algorithm; S4, considering the influence of the droop parameter of the DC frequency modulation controller on the per-unit value of the frequency steady-state deviation, adjusting the droop parameter of the DC frequency modulation controller of the multi-partition asynchronous interconnected power grid based on the ergodic optimization algorithm; The dynamic response equation is: in, is the per-unit value of the frequency deviation of regional power grid i, i=1, 2, 3; and are the inertia time constant and load damping coefficient of the equivalent generator of regional power grid i respectively; k p12 and k d12 They represent the droop parameter and inertia parameter of the DC frequency modulation controller between regional power grid 1 and regional power grid 2 respectively; k p13 and k d13 They represent the droop parameter and inertia parameter of the DC frequency modulation controller between regional power grid 1 and regional power grid 3 respectively; k p23 and k d23 They represent the droop parameter and inertia parameter of the DC frequency modulation controller between the regional power grid 2 and the regional power grid 3 respectively; It is the rectifier side between regional grid 1 and regional grid 2; It is the inverter side between regional power grid 1 and regional power grid 2; It is the rectifier side between regional grid 1 and regional grid 3; The inverter side between regional grid 1 and regional grid 3; It is the rectifier side between regional power grid 2 and regional power grid 3; The inverter side between regional grid 2 and regional grid 3; P 0dc12 , P 0dc13 and P 0dc23 They represent the reference values ​​of the steady-state transmission power of the DC system between regional grid 1 and regional grid 2, between regional grid 1 and regional grid 3, and between regional grid 2 and regional grid 3 respectively; ΔP mi and ΔP Li They represent the per-unit value of the mechanical power variation provided by the equivalent synchronous generator of regional power grid i and the per-unit value of the system load power variation; P Si is the rated capacity of equivalent synchronous generators in regional power grid i; When random disturbances occur in each sub-area power grid, the quantitative expression of the per-unit value of the frequency steady-state deviation of each sub-area power grid is: Where Δf si represents the per-unit value of the frequency steady-state deviation of regional power grid i; B i represents the frequency deviation coefficient of regional power grid i, where B i = 1 / R i + D i , R i represents the speed regulation parameters of the synchronous generator speed regulator of the regional power grid i; When the DC blocking between the sub-grids is randomly disturbed, the quantitative expression of the per-unit value of the frequency steady-state deviation of each sub-grid is: Where Δf si represents the per-unit value of the frequency steady-state deviation of regional power grid i; B i represents the frequency deviation coefficient of regional power grid i, where B i = 1 / R i + D i , R i represents the speed regulation parameters of the synchronous generator speed regulator of the regional power grid i; represents the DC blocking disturbance between regional power grid i and regional power grid j, where i <j,N ij ∈[0, 1], N ij It represents the ratio of the actual steady-state power transfer between regional grid i and regional grid j to the preset reference value.

2. According to the method for controlling a DC frequency modulation controller of a multi-partition asynchronous interconnected power grid according to claim 1, it is characterized in that: The process of obtaining the optimal coordinated control strategy of the DC frequency modulation controller based on the ergodic optimization algorithm includes: Determine the disturbance type and initialize the binary values ​​of parameters q1, q2, q3, q4, q5, and q6 to Q=000000; Construct the coefficient matrix M or N and start traversing all values ​​of Q; By solving the linear equation, the per-unit value of the steady-state deviation of the power grid frequency in each partition corresponding to the current Q value and the root mean square of the actual value of the steady-state deviation of the power grid frequency in each partition are calculated; the calculation equation for the root mean square of the actual value of the steady-state deviation of the power grid frequency in each partition is: ， Where n represents the total number of asynchronously interconnected regional power grids; Δf si represents the per-unit value of the frequency steady-state deviation of regional power grid i; F0 represents the rated frequency; Record the current Q value, compare and record the minimum RMS value and the Q value corresponding to the minimum RMS value; Completed arrive All possible binary combinations of Q output the minimum root mean square, and the optimal coordinated control parameter combination of the DC frequency modulation controller corresponding to Q, wherein the optimal coordinated control parameter combination is a combination of the values ​​of q1, q2, q3, q4, q5, and q6 corresponding to Q.

3. According to the method for controlling a DC frequency modulation controller of a multi-partition asynchronous interconnected power grid as described in claim 1, it is characterized in that: The S4 includes: S41, based on the optimal coordinated control strategy and state space equation of the DC frequency modulation controller, analyzing the influence of the parameters of the DC frequency modulation controller on the system stability; S42. Considering the influence of the DC frequency modulation controller parameters on the quantitative expression of the per-unit value of the frequency steady-state deviation, a droop parameter setting value is obtained based on an ergodic optimization algorithm.

4. According to claim 3, a DC frequency modulation controller control method for a multi-partition asynchronous interconnected power grid is characterized in that: The state space equations include: ， Where A and B represent the system matrix and input matrix respectively; represents the state vector; u represents the input vector; superscript represents the derivation; With given parameter values, the state space equation is transformed into: in, , , are the per unit values ​​of the frequency deviation of regional power grid 1 , per unit value of frequency deviation of regional power grid 2 , per unit value of regional power grid 3 frequency deviation , , , They are respectively the per-unit value of mechanical power provided by the equivalent synchronous generator of regional power grid 1, the per-unit value of mechanical power provided by the equivalent synchronous generator of regional power grid 2, and the per-unit value of mechanical power provided by the equivalent synchronous generator of regional power grid 3; and They represent the droop parameter and inertia parameter of the DC frequency modulation controller respectively.

5. According to the method for controlling a DC frequency modulation controller of a multi-partition asynchronous interconnected power grid as described in claim 3, it is characterized in that: The methods for obtaining the droop parameter setting value based on the ergodic optimization algorithm include: Input the frequency deviation coefficient of each regional power grid, the rated capacity of equivalent synchronous generators, the steady-state DC power transmitted between regional power grids, inertia parameters, and set fixed values ​​of q1 to q6 based on the optimal coordinated control strategy; Determine the droop parameter k p The value range of k is set and the parameters are initialized, the system matrix is ​​constructed, the root mean square of the actual value of the steady-state deviation of the power grid frequency in each partition is calculated, and the difference between different k p The root mean square of the actual value of the frequency steady-state deviation corresponding to the value, identify the minimum root mean square value and the corresponding optimal k p value.

Images