Phase modifier optimal configuration method considering decommissioning coal power transformation

Abstract

The invention provides a phase modifier optimal configuration method considering decommissioning coal power transformation, which comprises the following steps of: constructing a multi-direct-current feed-in receiving end power grid containing high-proportion new energy grid connection, and obtaining a decommissioning coal power unit set and a system equivalent impedance matrix in a system; calculating a new energy multi-station short-circuit ratio of each new energy station, and configuring a distributed / centralized phase modifier at a node with the minimum short-circuit ratio; iterating until the new energy multi-station short-circuit ratios all meet the requirements, and executing a second stage of phase modifier configuration; calculating an equivalent direct current electrical correlation coefficient of the nodes of the decommissioned coal power unit to the direct current drop point; the decommissioned coal power unit is transformed into a phase modifier according to the equivalent direct-current electrical correlation coefficient sequence until the multiple direct-current feed-in short-circuit ratios in the system all meet the requirements; and finally, outputting a phase modifier configuration scheme. According to the method, the voltage support strength of the high-proportion new energy receiving-end power grid is guaranteed, and the method has positive significance in reutilization of the decommissioned coal power unit of the receiving-end power grid and improvement of the voltage support strength.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a phase regulator optimization configuration method considering the transformation of retired coal-fired power plants. Background Art

[0002] With the gradual transformation of China's energy system towards low carbonization, the vigorous development of clean energy such as new energy units and DC transmission, the overall power grid has evolved into a low-inertia weak-support power system with high penetration of non-synchronous power sources. The system's reactive power reserve resources are scarce, the voltage support strength is weakened, and voltage and other safety and stability issues are facing severe challenges. For the receiving-end power grid, in a system with multiple DC feeds, the safe operation of DC transmission mainly depends on the reactive power support in the system. However, facing the current situation of a large number of traditional units being retired, large-capacity rotating equipment has dropped sharply, and the voltage support provided to the system is very limited. AC faults make it difficult to maintain the normal level of voltage in the vicinity of the DC landing point, and the safe operation of the new energy units in the vicinity cannot be guaranteed. The voltage stability problem has become an important hidden danger for the safe and stable operation of the power grid.

[0003] As a kind of dynamic reactive power compensation rotating equipment, synchronous condenser can be operated in phase advance or phase lag according to the reactive power demand of the system, and has become an effective measure to enhance the voltage support strength of the power grid in recent years. In order to improve the utilization rate of retired coal-fired power units and save the cost of reactive power compensation equipment, measures to transform retired coal-fired power units into condenser operation have been put into practice; in addition, in the current AC-DC hybrid power grid with a high proportion of new energy grid connection, large-capacity centralized condensers are usually configured on the busbar of the DC converter station or its nearby area, and small distributed condensers are configured on the busbar of the new energy station or the collection station. According to the literature survey, the current research mainly focuses on the voltage support strength of the new energy station, ignoring the problem of weakening the strength of the DC system caused by the large-scale development of new energy. The research on the optimal configuration strategy of condensers that takes into account the voltage support strength of the new energy station and the DC system is of vital importance to the safe and stable operation of the new power system in the future. Therefore, for the high proportion of new energy receiving-end power grid with multiple DC feed-ins, in order to ensure that the short-circuit ratio of the new energy station and the DC system can meet the safety requirements during the high penetration of new energy, how to scientifically configure synchronous condensers under the requirements of economy is the key issue to improve the voltage support strength of the current power system. Summary of the invention

[0004] In view of the deficiencies in the above-mentioned background technology, the present invention proposes a method for optimizing the configuration of phase modulators considering the transformation of retired coal-fired power plants. In the first stage, the sensitivity analysis of the short-circuit ratio on the distribution of phase modulators is used as the basis, and the distributed / centralized phase modulators are configured with the strength requirement MRSCR>2.5 of the new energy station as the key constraint. In the second stage, the order of transforming the phase modulators of retired coal-fired power units is determined by the equivalent DC electrical distance index, and the strength requirement MISCR>3 of the multi-DC system is met as the key constraint. Finally, the final configuration plan of the phase modulators is obtained.

[0005] The technical solution of the present invention is achieved in this way:

[0006] A phase-converter optimization configuration method considering the transformation of retired coal-fired power plants includes two stages of optimization configuration;

[0007] The specific steps for optimizing the phase shifter configuration in the first stage are:

[0008] S11: Based on the PSD-BPA simulation platform, a multi-DC feed-in receiving-end power grid with a high proportion of renewable energy is built, and the set of retired coal-fired power units in the system is obtained; the system grid structure and line parameters are read, and the system equivalent impedance matrix is ​​obtained;

[0009] S12: Calculate the short-circuit ratio of each new energy station and select the minimum MRSCR min ;

[0010] S13: Determine the minimum short-circuit ratio MRSCR of multiple new energy stations min With critical value MRSCR If the size of MRSCR min ≥ MRSCR , then the new energy station does not need to configure synchronous condensers and directly executes the second stage; otherwise, the new energy station configures synchronous condensers;

[0011] S14: Under the premise of not exceeding the limit on the number of phase regulators configured in new energy stations, min Distributed / centralized phase regulators are configured at renewable energy stations; otherwise, the MRSCR min A phase regulator is configured at the new energy station, and the process goes to step S12;

[0012] The specific steps for optimizing the phase-shifting configuration in the second phase are:

[0013] S21: Calculate the equivalent DC electrical correlation coefficient of the retired coal-fired power unit node to the DC drop point;

[0014] S22: Calculate the multi-DC feed-in short-circuit ratio of each DC line under the phase-converter configuration scheme that meets the short-circuit ratio of multiple renewable energy stations, and select the minimum MISCR min ;

[0015] S23: Determine the minimum value of the short-circuit ratio of multiple DC feeds MISCR min With critical value MISCR If the size of MISCR min ≥ MISCR , then there is no need to configure the phase regulator; otherwise, the order of modifying the phase regulator of the retired coal-fired power units is guided according to the order of the equivalent DC electrical correlation coefficients, and then go to step S22.

[0016] The method for obtaining the system equivalent impedance matrix is ​​as follows: after connecting the synchronous condenser at node i, the condenser is equivalent to the ground impedance z io , that is:

[0017]

[0018] Among them, the element in the pth row and qth column can be expressed as:

[0019]

[0020] Where: Z n is the n-order impedance matrix of the original network; Z n1 is the impedance matrix after the change; Z i The impedance matrix Z n The i-th row of Z i Transpose of the matrix; Z n,pq is the element in the pth row and qth column of the original equivalent impedance matrix; Z n1,pq is the element in the pth row and qth column of the equivalent impedance matrix after the change, Z ii is the equivalent self-impedance of node i, z io The equivalent ground impedance of the phase regulator, Z ip represents the equivalent mutual impedance between node i and node p, Z iq represents the equal mutual impedance of node i and node q.

[0021] The calculation method of the short-circuit ratio of the new energy multi-station is:

[0022] According to the relationship between the short-circuit ratio of multiple renewable energy stations and the elements of the system impedance matrix, if a phase regulator is connected at node i, the MRSCR index expression of renewable energy station r changes to:

[0023]

[0024] Where: subscript w represents the new energy station; P r,w represents the injected power of the new energy station at node r, P p,w represents the injected power of the new energy station at node p; Z rpRepresents the equivalent mutual impedance of nodes p and r of the new energy station grid-connected, Z ip Represents the equivalent mutual impedance of node i and node p of the new energy station grid-connected, Z ir U represents the equivalent mutual impedance of node i and node r of the new energy station grid-connected; r It is the grid-connected bus voltage of the new energy station;

[0025] MRSCR change at new energy station r △MRSCR r It can be expressed as:

[0026]

[0027] The sensitivity of synchronous condensers connected to different locations to the improvement of grid voltage support strength mainly depends on the equivalent mutual impedance Z ir Effect of changes in △MRSCR r The nature of the impact on Z ir Taking partial derivatives we get:

[0028]

[0029] According to the partial derivative results, the mutual impedance Z ir ΔMRSCR r There is a positive correlation, that is, △MRSCR r With Z ir increases with the increase of .

[0030] The expression of the equivalent DC electrical correlation coefficient is:

[0031]

[0032] Where: Z i is the equivalent DC correlation coefficient between the retired coal-fired power unit node i and each DC d; Ω d is the DC set in the system; ω d is the weight coefficient set according to the strength of each DC system; Z id is the equivalent mutual impedance between the retired coal-fired power unit i and each DC drop point d.

[0033] The calculation method of the multi-DC feed-in short-circuit ratio is:

[0034] After the synchronous condenser is connected to the system, it also has a certain reactive power support effect on the DC system, and the multi-DC feed-in short-circuit ratio index expression changes to:

[0035]

[0036] Where: U d is the node voltage at the DC point d; the subscript h indicates DC; P q,his the DC capacity fed into node q; Z dq is the equivalent mutual impedance between node d and node q where the DC falls, Z id is the equivalent mutual impedance between node i and node d where the DC falls, Z iq is the equivalent mutual impedance between node i and node q where the DC falls.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention proposes a two-stage optimization configuration strategy for phase-converters that takes into account the transformation of retired coal-fired power units for multi-DC feed-in receiving-end power grids containing a high proportion of renewable energy. Based on the correlation between phase-converter distribution and short-circuit ratio, installing phase-converters at the point where the short-circuit ratio is the smallest has the best effect on improving the voltage support strength of the power grid, and this is used to guide the first-stage configuration of synchronous phase-converters, and obtains distributed phase-converters and centralized phase-converters configuration schemes that meet the short-circuit ratio safety requirements of new energy sites; an equivalent DC electrical correlation coefficient is proposed as an evaluation index for the sequence of phase-converters for coal-fired power units to transform, and this is used to guide the second-stage configuration of synchronous phase-converters, and obtains a configuration scheme for phase-converters for the transformation of retired coal-fired power units that meets the DC short-circuit ratio safety requirements; an improved IEEE-39 node system is built on the PSD-BPA platform to perform short-circuit ratio and transient overvoltage verification on the configuration scheme; and based on factors such as investment cost and transient overvoltage suppression effect, the phase-converter configuration scheme is evaluated to obtain the optimal phase-converter configuration scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 work.

[0039] Figure 1 The phase regulator optimization configuration flow chart of the present invention;

[0040] Figure 2 This is a schematic diagram of a multi-DC feed-in receiving-end power grid with a high proportion of new energy grid-connected, built based on PSD-BPA in the present invention;

[0041] Figure 3 The suppression effect of the distributed and centralized phase-shifting configuration schemes of the present invention on transient overvoltage;

[0042] Figure 4 It is a time domain diagram of the reactive power output state of the distributed and centralized phase regulators in the transient process of the present invention;

[0043] Figure 5 It is a schematic diagram of the best configuration scheme of the phase regulator of the present invention. DETAILED DESCRIPTION

[0044] 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.

[0045] like Figure 1 As shown, the embodiment of the present invention provides a phase-shifting optimization configuration method considering the transformation of retired coal-fired power plants, including two-stage optimization configuration;

[0046] The specific steps for optimizing the phase shifter configuration in the first stage are:

[0047] S11: Based on the PSD-BPA simulation platform, a multi-DC feed-in receiving-end power grid with a high proportion of renewable energy is built, such as Figure 2 As shown, the set of retired coal-fired power units in the system is obtained; the system grid structure and line parameters are read, and the system equivalent impedance matrix is ​​obtained.

[0048] The coal-fired power units at nodes 30, 33, 34, 35, and 36 will be shut down and retired (they will be derated as phase-converting units to be transformed), and new energy stations will be built at the corresponding locations (hereinafter referred to as W30 / W33 / W34 / W35 / W36), and two DC lines will be fed in at nodes 14 and 26 (hereinafter referred to as h1 / h2). In the phase-converting configuration process: the phase-converting configuration of the new energy station in the first stage is divided into two schemes: large-capacity centralized phase-converting (300MVar) and small-capacity distributed phase-converting (50MVar); the phase-converting configuration in the second stage to improve the strength of the DC system is mainly based on the phase-converting scheme of retired coal-fired power units.

[0049] In order to analyze the influence of the phase condenser on the short-circuit ratio after it is connected to the grid, after the synchronous phase condenser is connected at node i, the phase condenser is equivalent to the ground impedance z io , which can be regarded as adding a grounding chain branch with one node at zero potential. According to the branch addition method, the elements in the system impedance matrix are changed, namely:

[0050]

[0051] Among them, the element in the pth row and qth column can be expressed as:

[0052]

[0053] Where: Z n is the n-order impedance matrix of the original network; Z n1is the impedance matrix after the change; Z i The impedance matrix Z n The i-th row of Z i Transpose of the matrix; Z n,pq is the element in the pth row and qth column of the original equivalent impedance matrix; Z n1,pq is the element in the pth row and qth column of the equivalent impedance matrix after the change, Z ii is the equivalent self-impedance of node i, z io The equivalent ground impedance of the phase regulator, Z ip represents the equivalent mutual impedance between node i and node p, Z iq represents the equal mutual impedance of node i and node q.

[0054] S12: Calculate the short-circuit ratio of each new energy station and select the minimum MRSCR min (From the sensitivity analysis of the phase regulator and the short-circuit ratio index, it can be seen that the best effect is to configure the phase regulator at the node with the minimum short-circuit ratio);

[0055] According to the relationship between the short-circuit ratio of multiple renewable energy stations and the elements of the system impedance matrix, if a phase regulator is connected at node i, the MRSCR index expression of renewable energy station r changes to:

[0056]

[0057] Where: subscript w represents the new energy station; P r,w represents the injected power of the new energy station at node r, P p,w represents the injected power of the new energy station at node p; Z rp Represents the equivalent mutual impedance of nodes p and r of the new energy station grid-connected, Z ip Represents the equivalent mutual impedance of node i and node p of the new energy station grid-connected, Z ir U represents the equivalent mutual impedance of node i and node r of the new energy station grid-connected; r It is the grid-connected bus voltage of the new energy station.

[0058] MRSCR change at new energy station r △MRSCR r It can be expressed as:

[0059]

[0060] The sensitivity of synchronous condensers connected to different locations to the improvement of grid voltage support strength mainly depends on the equivalent mutual impedance Z ir Effect of changes in △MRSCR r The nature of the impact on Z ir Taking partial derivatives we get:

[0061]

[0062] According to the partial derivative results, the mutual impedance Z ir ΔMRSCR r There is a positive correlation, that is, △MRSCR r With Z ir According to the correlation between mutual impedance and electrical distance, it is proved that when the phase regulator is connected at the location with the smaller short-circuit ratio of the new energy station in the system, the increase of the short-circuit ratio of other new energy stations will be greater, and the effect of improving the voltage support strength of the system will be most significant.

[0063] S13: Determine the minimum short-circuit ratio MRSCR of multiple new energy stations min With critical value MRSCR (usually 2.5) if MRSCR min ≥ MRSCR , then the new energy station does not need to configure synchronous condensers and directly executes the second stage; otherwise, the new energy station configures synchronous condensers;

[0064] S14: Under the premise of not exceeding the limit on the number of phase regulators configured in new energy stations, min Distributed / centralized phase regulators are configured at renewable energy stations; otherwise, the MRSCR min A phase regulator is configured at the new energy station, and the process goes to step S12;

[0065] The specific steps for optimizing the phase-shifting configuration in the second phase are:

[0066] S21: Calculate the equivalent DC electrical correlation coefficient of the retired coal-fired power unit node to the DC drop point;

[0067] Assume that there are n nodes in a power system, and the earth is generally used as the reference node. According to the calculation method of power network flow distribution, the node voltage equation is derived using the node admittance matrix, that is:

[0068] I B =Y B U B

[0069] Where: Y B is the n×n order node admittance matrix; I B U is the column vector of the node injection current; B is the column vector of node voltages.

[0070] Multiply both sides of the equal sign in the above equation by It is equivalent to:

[0071]

[0072] Where: is the n×n order system node impedance matrix.

[0073] Expand the above formula to get:

[0074]

[0075] When the current disturbance △I is injected into node i, the voltage change △U of each node is calculated as follows:

[0076]

[0077] That is, when the injected current △I i When disturbed, the change in node j voltage △U j It can be represented as the mutual impedance value Z between node j and the disturbance current injection node i ij This shows that the larger the mutual impedance value, the stronger the electrical correlation between nodes.

[0078]

[0079] It can be seen from the above formula that mutual impedance can reflect the strength of the electrical correlation between grid nodes and evaluate the supporting role of each coal-fired power unit in the system on the grid voltage. The larger the mutual impedance value, the stronger the electrical correlation, which proves that the coal-fired power unit has a better support effect on the reactive voltage of the grid, and should be given priority as the unit to be transformed in the set of retired coal-fired power units.

[0080] In the receiving-end power grid with multiple DC feeds, each DC converter station is generally equipped with reactive compensation devices to support normal phase switching and other operating conditions of multiple DC. According to the above analysis, the phase regulator installed in the system has a certain voltage support effect on the strength of each DC transmission system. In order to make the units to be transformed have the best comprehensive improvement effect on the voltage support strength of each DC converter station, the equivalent DC electrical correlation coefficient is proposed to characterize the strength of the retired coal-fired power unit node to each DC electrical correlation. The equivalent DC electrical correlation coefficient is calculated and sorted to guide the order of phase regulator transformation of retired coal-fired power units.

[0081]

[0082] Where: Z i is the equivalent DC correlation coefficient between the retired coal-fired power unit node i and each DC d; Ω d is the DC set in the system; ω d is the weight coefficient set according to the strength of each DC system; Z id is the mutual impedance between the retired coal-fired power unit i and each DC drop point d.

[0083] S22: Calculate the multi-DC feed-in short-circuit ratio of each DC line under the phase-converter configuration scheme that meets the short-circuit ratio of multiple renewable energy stations, and select the minimum MISCR min ;

[0084] After the synchronous condenser is connected to the system, it also has a certain reactive power support effect on the DC system, and the multi-DC feed-in short-circuit ratio index expression changes to:

[0085]

[0086] Where: U d is the node voltage at the DC point d; the subscript h indicates DC; P q,h is the DC capacity fed into node q; Z dq is the equivalent mutual impedance between node d and node q where the DC falls, Z id is the equivalent mutual impedance between node i and node d where the DC falls, Z iq is the equivalent mutual impedance between node i and node q where the DC falls.

[0087] S23: Determine the minimum value of the short-circuit ratio of multiple DC feeds MISCR min With critical value MISCR (Usually 3) If MISCR min ≥ MISCR , then there is no need to configure the phase regulator; otherwise, the order of modifying the phase regulator of the retired coal-fired power units is guided according to the order of the equivalent DC electrical correlation coefficients, and then go to step S22.

[0088] The first phase configuration results of the phase shifter configuration strategy proposed in the present invention are as follows:

[0089] (1) If the new energy station is equipped with a distributed phase regulator, six iterations are required. Two phase regulators (2*50MVar) are configured at the W36 and W34 stations, and one phase regulator (1*50MVar) is configured at the W33 and W35 stations. After the phase regulators are configured, the MRSCR of each new energy station meets the short-circuit ratio safety requirements, among which the MRSCR of the W35 station is the smallest (2.8020);

[0090] (2) If the new energy station is equipped with a centralized phase regulator, two iterations are required, and one phase regulator (1*300MVar) is configured at W36 and W34 respectively to meet the short-circuit ratio safety requirements. Among them, the MRSCR of the W35 station is the smallest (2.5583). At this time, the first stage of phase regulator configuration is completed.

[0091] (3) First-stage MISCR verification

[0092] After the first phase configuration of the phase condenser is completed, the strength check of the short-circuit ratio of the two DC multi-feeds in the system is performed, as shown in Table 1. It can be seen that after the first phase phase condenser configuration, the short-circuit ratio MISCR of the multi-DC feeds has been improved, but the MISCR of DC h2 still does not meet the short-circuit ratio safety requirements, so the second phase configuration of the phase condenser is required to improve the voltage support strength of the DC system.

[0093] Table 1 MISCR verification under the first stage phase condenser configuration scheme

[0094]

[0095] The second phase configuration result of the phase shifter configuration strategy proposed in the present invention is:

[0096] The second stage configuration of synchronous condensers aims to make the DC short-circuit ratio in the system meet the strength requirements. This stage mainly configures the condensers of the retired coal-fired power units. According to the results in Table 1, the short-circuit ratio of DC h2 is lower than that of DC h1. Therefore, in the process of calculating the equivalent DC electrical correlation coefficient of the retired coal-fired power units to DC, the mutual impedance weight coefficients are taken as: ω1 = 0.4 and ω2 = 0.6. The calculation results are shown in Table 2. According to the order of index results, the coal-fired power units at the node 30 are prioritized for the best voltage support effect on the DC system, and the others are configured in order.

[0097] Table 2 Equivalent DC electrical correlation coefficients of retired coal-fired power unit nodes to DC converter stations

[0098]

[0099] According to the phase condenser configuration results of the first stage and the equivalent DC electrical correlation coefficient index, the phase condenser configuration scheme of the second stage is as follows: (1) Under the distributed phase condenser configuration scheme, it is only necessary to transform the retired coal-fired power unit at node 30 into a phase condenser to meet the short-circuit ratio safety requirements; (2) Under the centralized phase condenser configuration scheme, it is necessary to transform the retired coal-fired power units at nodes 30 and 35 into phase condensers to meet the short-circuit ratio safety requirements. After the second stage phase condenser configuration is completed, the final phase condenser configuration scheme is output to verify the short-circuit ratio of the new energy station and the DC system. The results are shown in Table 3.

[0100] Table 3 Short-circuit ratio index verification of phase-converter configuration scheme

[0101]

[0102] In order to verify the effectiveness of the equivalent DC electrical correlation coefficient index, the configuration scheme of the phase-converter transformation of retired coal-fired power units at nodes 30 and 33 was taken as a comparative example. The MISCR was verified under this scheme, and the results are as follows: MISCR(h1)=3.4305, MISCR(h2)=3.0389. Although both can meet the requirements, the improvement effect on the DC system is slightly inferior to the scheme of the phase-converter transformation of retired coal-fired power units at node 35. This proves that it is feasible to guide the sequence of phase-converter transformation of retired coal-fired power units based on the equivalent DC electrical correlation coefficient.

[0103] Transient overvoltage check of the phase-converter configuration scheme of the present invention:

[0104] Since the system may not be able to cope with the transient overvoltage problem caused by excess reactive reverse transmission due to insufficient dynamic reactive reserve under the DC blocking fault, the present invention verifies the effectiveness of the proposed phase-shifting configuration strategy in suppressing transient overvoltage problems based on the PSD-BPA simulation platform under the synchronous phase-shifting configuration scheme. The verification method is: when the system runs to 0.2s, a DC h1 single-pole blocking fault is set, and the transient overvoltage results of the new energy station and the DC landing point and the instantaneous reactive output simulation results of the phase-shifting are shown in Table 4, Figure 3 and Figure 4 shown.

[0105] Table 4 Transient overvoltage extreme values ​​of new energy stations

[0106]

[0107] From the above results, it can be seen that after the synchronous phase regulator is configured, under the DC fault condition, the phase regulator provides reactive voltage support for the system at the moment of the fault, so that the transient overvoltage extreme values ​​of the DC converter station and the grid-connected bus of the new energy station are reduced to a certain extent due to the transient reactive regulation of the phase regulator. The transient overvoltage extreme value of the grid-connected bus of the new energy station is reduced to below 1.09pu, and the transient overvoltage extreme value of the DC converter station bus is reduced by about 1.18pu, which has a certain inhibitory effect on transient overvoltage, improves the voltage support strength of the power grid, and ensures the safe and stable operation of the DC system and new energy.

[0108] According to engineering experience, the construction cost of centralized phase regulators is about four times that of distributed phase regulators and the cost of coal-fired power unit transformation. There are 6 distributed phase regulators and 1 transformed phase regulator in the distributed phase regulator configuration scheme, and 2 centralized phase regulators and 2 transformed phase regulators in the centralized phase regulator configuration scheme. In terms of cost, the scheme of configuring small-capacity distributed phase regulators for new energy stations is more economical. Compared with the configuration without phase regulators, the transient overvoltage of new energy stations under the distributed phase regulator configuration scheme is reduced by 4.6%. The centralized phase regulator has a large configuration capacity and a large reactive power regulation range, so the transient overvoltage of new energy stations is reduced by 5.3%, and the suppression effect is slightly better than that of the distributed phase regulator configuration; and the transient overvoltage extreme values ​​of the DC converter station are almost the same under the two schemes.

[0109] In summary, considering the investment cost, transient overvoltage suppression effect and other factors, the best solution is to configure small-capacity distributed phase regulators at new energy stations. The final solution for phase regulator configuration is: stations W36 and W34 are equipped with 2 distributed phase regulators (2*50MVar), stations W33 and W35 are equipped with 1 distributed phase regulator (1*50MVar), and node 30 is converted into a phase regulator (1*300MVar). The configuration diagram is shown in the figure. Figure 5 shown.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for optimizing phase-shifting configuration considering the transformation of retired coal-fired power plants, characterized in that: It includes two stages of optimization configuration; The specific steps for optimizing the phase shifter configuration in the first stage are: S11: Based on the PSD-BPA simulation platform, a multi-DC feed-in receiving-end power grid with a high proportion of renewable energy grid-connected is built, and the set of retired coal-fired power units in the system is obtained; Read the system grid structure and line parameters, and obtain the system equivalent impedance matrix; S12: Calculate the short-circuit ratio of each new energy station and select the minimum MRSCR min ; S13: Determine the minimum short-circuit ratio MRSCR of multiple new energy stations min and the critical value MRSCR, if MRSCR min ≥MRSCR, the new energy station does not need to configure synchronous condensers and directly executes the second stage; otherwise, the new energy station configures synchronous condensers; S14: Under the premise of not exceeding the limit on the number of phase regulators configured in new energy stations, min Distributed / centralized phase regulators are configured at renewable energy stations; otherwise, the MRSCR min A phase regulator is configured at the new energy station, and the process goes to step S12; The specific steps for optimizing the phase-shifting configuration in the second phase are: S21: Calculate the equivalent DC electrical correlation coefficient of the retired coal-fired power unit node to the DC drop point; S22: Calculate the multi-DC feed-in short-circuit ratio of each DC line under the phase-converter configuration scheme that meets the short-circuit ratio of multiple renewable energy stations, and select the minimum MISCR min ; S23: Determine the minimum value of the short-circuit ratio of multiple DC feeds MISCR min and the critical value MISCR, if MISCR min ≥MISCR, there is no need to configure the phase regulator; otherwise, the order of modifying the phase regulator of the retired coal-fired power units is guided according to the order of the equivalent DC electrical correlation coefficients, and then go to step S22.

2. The method for optimizing phase-shifting configuration considering the transformation of retired coal-fired power plants according to claim 1 is characterized in that: The method for obtaining the system equivalent impedance matrix is ​​as follows: after connecting the synchronous condenser at node i, the condenser is equivalent to the ground impedance z io , that is: Among them, the element in the pth row and qth column can be expressed as: Where: Z n is the n-order impedance matrix of the original network; Z n1 is the impedance matrix after the change; Z i The impedance matrix Z n The i-th row of Z i Transpose of the matrix; Z n,pq is the element in the pth row and qth column of the original equivalent impedance matrix; Z n1,pq is the element in the pth row and qth column of the equivalent impedance matrix after the change, Z ii is the equivalent self-impedance of node i, z io The equivalent ground impedance of the phase regulator, Z ip represents the equivalent mutual impedance between node i and node p, Z iq represents the equal mutual impedance of node i and node q.

3. The method for optimizing phase-shifting configuration considering the transformation of retired coal-fired power plants according to claim 2 is characterized in that: The calculation method of the short-circuit ratio of the new energy multi-station is: According to the relationship between the short-circuit ratio of multiple renewable energy stations and the elements of the system impedance matrix, if a phase regulator is connected at node i, the MRSCR index expression of renewable energy station r changes to: Where: subscript w represents the new energy station; P r,w represents the injected power of the new energy station at node r, P p,w represents the injected power of the new energy station at node p; Z rp Represents the equivalent mutual impedance of nodes p and r of the new energy station grid-connected, Z ip Represents the equivalent mutual impedance of node i and node p of the new energy station grid-connected, Z ir Represents the equivalent mutual impedance of node i and node r of the new energy station grid connection; U r It is the grid-connected bus voltage of the new energy station; MRSCR change at new energy station r △MRSCR r It can be expressed as: The sensitivity of synchronous condensers connected to different locations to the improvement of grid voltage support strength mainly depends on the equivalent mutual impedance Z ir Effect of changes in △MRSCR r The nature of the impact on Z ir Taking partial derivatives we get: According to the partial derivative results, the mutual impedance Z ir ΔMRSCR r There is a positive correlation, that is, △MRSCR r With Z ir increases with the increase of .

4. The method for optimizing phase-shifting configuration considering the transformation of retired coal-fired power plants according to claim 2 is characterized in that: The expression of the equivalent DC electrical correlation coefficient is: Where: Z i is the equivalent DC correlation coefficient between the retired coal-fired power unit node i and each DC d; Ω d is the DC set in the system; ω d is the weight coefficient set according to the strength of each DC system; Z id is the equivalent mutual impedance between the retired coal-fired power unit i and each DC drop point d.

5. The method for optimizing phase-shifting configuration considering the transformation of retired coal-fired power plants according to claim 4 is characterized in that: The calculation method of the multi-DC feed-in short-circuit ratio is: After the synchronous condenser is connected to the system, it also has a certain reactive power support effect on the DC system, and the multi-DC feed-in short-circuit ratio index expression changes to: Where: U d is the node voltage at the DC point d; the subscript h indicates DC; P q,h is the DC capacity fed into node q; Z dq is the equivalent mutual impedance between the DC point node d and the node q, Z id is the equivalent mutual impedance between node i and node d where the DC falls, Z iq is the equivalent mutual impedance between node i and node q where the DC falls.

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