Determination method and apparatus for minimum startup capacity of thermal power unit based on voltage stabilization

Abstract

A determination method and apparatus for the minimum startup capacity of a thermal power unit based on voltage stabilization, an electronic device, a storage medium, and a computer program product. The method comprises: acquiring the load level and the output level of a power system; if a difference value between the output level and the load level is greater than a preset capacity, determining that the power system is a sending-end power grid, and calculating the minimum startup capacity of a thermal power unit of the sending-end power grid considering the voltage stability constraint; and if the output level is less than the load level, determining that the power system is a receiving-end power grid, and calculating the minimum startup capacity of a thermal power unit of the receiving-end power grid considering the voltage stability constraint. By means of the present method and apparatus, the calculation result is more accurate and reliable. System output arrangement and system thermal power unit planning based on the present method can ensure the system voltage stability and avoid new energy disordered development.

Description

Method and device for determining minimum startup capacity of thermal power units based on voltage stability

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure is based on Chinese patent application number 202310861398.7, application date July 14, 2023, and application name “Method and device for determining the minimum starting capacity of a thermal power unit based on voltage stability”, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into this disclosure as a reference. Technical Field

[0003] The present disclosure relates to, but is not limited to, the field of power system planning technology. Specifically, it relates to a method, device, electronic device, storage medium, and computer program product for determining the minimum startup capacity of a thermal power unit based on voltage stability. Background Art

[0004] As of 2022, my country has completed 33 ultra-high voltage (UHV) projects, including 19 DC and 14 AC. This has formed an ultra-high voltage (UHV) AC ring network in East and North China, highlighting the trend of hybrid AC / DC power grid operation. In recent years, my country has achieved rapid growth in renewable energy, with installed renewable energy capacity reaching a historic 100 GW in 2021. General Secretary Xi Jinping has proposed that by 2030, non-fossil energy will account for approximately 25% of primary energy consumption, and the total installed capacity of wind and solar power will reach over 1.2 GW. Given the current rapid development of renewable energy, which has led to a reduction in the capacity of thermal power units in the system, system security and stability face enormous challenges. While voltage stability is a localized phenomenon, localized voltage instability can trigger a chain reaction, leading to voltage collapse across the entire system. Large-scale DC and renewable energy in AC / DC hybrid systems with a high proportion of renewable energy require voltage support to ensure system security. Therefore, research on voltage stability in systems with a high proportion of renewable energy is necessary.

[0005] At present, there are some minimum startup methods for thermal power units, but there are problems such as insufficient consideration of factors and incompleteness. For example, the impact of serious faults such as DC groups on system voltage stability is not considered, the voltage stability of new energy units is not considered, the impact of short-circuit capacity is not considered, and there are also problems such as small unit range, inability to cover all units in the network, unsuitability for large power grids, and limited applicability.

[0006] Summary of the Invention

[0007] In view of this, the embodiments of the present disclosure propose a method, device, electronic device, storage medium and computer program product for determining the minimum startup capacity of a thermal power unit based on voltage stability, aiming to solve the problems in the existing technology of the minimum startup method of thermal power units, such as insufficient consideration of factors, inability to cover all units in the network, and limited applicability.

[0008] In a first aspect, an embodiment of the present disclosure provides a method for determining the minimum startup capacity of a thermal power unit based on voltage stability, the method comprising: step S101: obtaining the load level and output level of the power system; step S102: if the difference between the output level and the load level is greater than a preset capacity, determining that the power system is a sending-end power grid, and calculating the minimum startup capacity of the thermal power unit of the sending-end power grid considering the voltage stability constraint; step S103: if the output level is less than the load level, determining that the power system is a receiving-end power grid, and calculating the minimum startup capacity of the thermal power unit of the receiving-end power grid considering the voltage stability constraint.

[0009] In the second aspect, the embodiment of the present disclosure also provides a device for determining the minimum startup capacity of a thermal power unit based on voltage stability, the device comprising: a data acquisition part 101, configured to obtain the load level and output level of the power system; a sending-end grid processing part 102, configured to determine that the power system is a sending-end grid if the difference between the output level and the load level is greater than a preset capacity, and calculate the minimum startup capacity of the thermal power unit of the sending-end grid considering the voltage stability constraint; a receiving-end grid processing part 103, configured to determine that the power system is a receiving-end grid if the output level is less than the load level, and calculate the minimum startup capacity of the thermal power unit of the receiving-end grid considering the voltage stability constraint.

[0010] In a third aspect, an embodiment of the present disclosure further provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the methods provided in the above embodiments are implemented.

[0011] In a fourth aspect, an embodiment of the present disclosure further provides an electronic device, comprising: a processor; a memory configured to store executable instructions of the processor; the processor being configured to read the executable instructions from the memory and execute the executable instructions to implement the methods provided in the above embodiments.

[0012] In a fifth aspect, an embodiment of the present disclosure further provides a computer program product, which includes a computer program or instructions. When the computer program or instructions are run on a computer, the computer is enabled to execute the methods provided in the above embodiments.

[0013] The method, device, electronic device, storage medium and computer program product provided in the embodiments of the present disclosure determine the minimum startup capacity of thermal power units based on voltage stability. The method determines whether the power grid is a sending-end power grid or a receiving-end power grid by output level and load level, and calculates the minimum startup capacity of thermal power units in the sending-end power grid and the minimum startup capacity of thermal power units in the receiving-end power grid considering voltage stability constraints according to the different characteristics of the sending-end power grid and the receiving-end power grid, respectively. The calculation results are more accurate and reliable. System output arrangement according to the method provided in the embodiments of the present disclosure can ensure system voltage stability. System thermal power unit planning according to the method provided in the embodiments of the present disclosure, combined with the planning of hydropower, nuclear power, pumped storage and other units in the system, can be further applied to the planning of new energy consumption scale to avoid disorderly development of new energy.

[0014] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments of the present disclosure will be described below.

[0016] The accompanying drawings herein are incorporated into and constitute a part of the specification. These drawings illustrate embodiments consistent with the present disclosure and, together with the specification, are used to explain the technical solutions of the present disclosure.

[0017] FIG1 shows an exemplary flow chart of a method for determining the minimum operating capacity of a thermal power unit based on voltage stability according to an embodiment of the present disclosure;

[0018] FIG2 shows an exemplary flow chart of a method for calculating the minimum operating capacity of thermal power generating units in a power grid at the sending end considering voltage stability constraints according to an embodiment of the present disclosure;

[0019] FIG3 shows an exemplary flow chart of a method for calculating the minimum operating capacity of a thermal power generating unit in a receiving-end power grid considering voltage stability constraints according to an embodiment of the present disclosure;

[0020] FIG4 is a schematic diagram showing the voltages of key bus nodes in the case of a three-phase commutation failure of the Qingningxin DC group according to an embodiment of the present disclosure, wherein FIG4(a) is a schematic diagram showing the voltages of Qingqingnan and Ningtiandu, and FIG4(b) is a schematic diagram showing the voltages of Guokumu and Xinhamichang;

[0021] FIG5 shows a schematic structural diagram of an apparatus for determining the minimum operating capacity of a thermal power generation unit based on voltage stability according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] Exemplary embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, the present disclosure may be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to provide a detailed and complete disclosure of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present disclosure. In the accompanying drawings, identical parts / elements are denoted by the same reference numerals.

[0023] Unless otherwise specified, the terms used herein (including technical terms) have the meanings commonly understood by those skilled in the art. In addition, it is understood that terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0024] FIG1 shows an exemplary flow chart of a method for determining the minimum operating capacity of a thermal power generation unit based on voltage stability according to an embodiment of the present disclosure.

[0025] As shown in FIG1 , the method includes:

[0026] Step S101: Obtain the load level and output level of the power system.

[0027] Collect basic parameters such as system load level, new energy, conventional units, and DC capacity, maintenance schedule, and system grid structure to form a basic power grid planning scheme. Based on the system load and output level, determine whether the planned power grid is a sending-end grid or a receiving-end grid.

[0028] Step S102: If the difference between the output level and the load level is greater than the preset capacity, the power system is determined to be a sending-end power grid, and the minimum startup capacity of the thermal power units in the sending-end power grid considering the voltage stability constraint is calculated.

[0029] By limiting the difference between output and load to be greater than a preset capacity, the power system is ensured to be a typical sending-end power grid. For example, the preset capacity is 3000MW.

[0030] FIG2 shows an exemplary flow chart of a method for calculating the minimum operating capacity of thermal power generating units in a sending-end power grid considering voltage stability constraints according to an embodiment of the present disclosure.

[0031] As shown in FIG2 , in some embodiments, calculating the minimum operating capacity of thermal power units in the sending-end power grid considering voltage stability constraints includes:

[0032] Step S201: Obtain and divide the power system into several DC groups based on the grid structure;

[0033] Each faulty DC group among the plurality of DC groups is sequentially selected as a target DC group, and steps S202 to S203 are performed until all faulty DC groups in the power system are traversed:

[0034] Step S202: Obtaining and obtaining a first contribution rate index of each thermal power unit to the system voltage based on the voltage changes of each DC bus before and after the fault and the voltage changes of each DC bus node when shutting down each thermal power unit, and sorting all the thermal power units in ascending order of the first contribution rate index to obtain a first thermal power unit shutdown sequence;

[0035] Step S203: Obtain and determine whether any of the DC bus voltage changes before and after the fault, the DC multi-infeed short-circuit ratio, and the renewable energy short-circuit ratio exceed their respective threshold ranges. If not, shut down the thermal power units one by one according to the first thermal power unit shutdown sequence until, after shutting down one thermal power unit, any of the DC bus voltage changes before and after the fault, the DC multi-infeed short-circuit ratio, and the renewable energy short-circuit ratio exceed their respective threshold ranges. The total capacity of the thermal power units before the fault is used as the minimum system startup capacity considering the voltage stability constraint of the target DC group after the fault.

[0036] Step S204: Select the maximum value from all minimum operating capacities of the system considering voltage stability constraints after a DC group fault as the minimum operating capacity of the thermal power generating units in the sending-end power grid.

[0037] It is important to understand that each of the DC bus voltage changes before and after the fault, the DC multi-infeed short-circuit ratio, and the renewable energy short-circuit ratio each has its own corresponding threshold range, which can be set according to specific needs. If each value of each of the DC bus voltage changes before and after the fault, the DC multi-infeed short-circuit ratio, and the renewable energy short-circuit ratio does not exceed its respective threshold range, then the thermal power units are shut down one by one according to the first thermal power unit shutdown sequence, and these three data sets are iteratively calculated so that each value gradually approaches its respective threshold range. The case where the three data sets are closest to the threshold range and do not exceed the threshold range is selected as the iterative optimal solution. The capacity of each thermal power unit under the iterative optimal solution is obtained and calculated, and the total capacity of the thermal power units is obtained as the minimum startup capacity of the system considering the voltage stability constraint after the target DC group fault.

[0038] In some implementations, the change in the DC bus voltage before and after the fault is the absolute value of the difference between the DC bus voltage after the fault and the DC bus voltage before the fault.

[0039] In some embodiments, the DC multi-infeed short-circuit ratio of the j-th DC-connected bus node is calculated using the following formula (1):

[0040] Among them, S j is the short-circuit capacity of commutation bus j, PDj is the rated power of DC j, MIIF jk is the multi-feed interaction factor between DC converter station j and converter station k, P Dk is the rated power of DC k, and m is the total number of DC.

[0041] In some embodiments, the new energy short-circuit ratio of the grid-side access point of the new energy power generation equipment or the grid-connected bus node i of the station is calculated using the following formula (2):

[0042] in, is the nominal voltage of the i-th grid-connected busbar node, is the voltage generated by the renewable energy power generation at the i-th node, and the subscript RE represents the renewable energy power generation equipment or station. The equivalent impedance calculated for the system side between the main grid equivalent power source i and the corresponding grid connection point is: is the actual apparent power of the new energy injected into the i-th new energy grid-connected bus node, is the actual apparent power of the new energy injected into the j-th new energy grid-connected bus node, is the complex power conversion factor between the renewable energy grid-connected busbars i and j, and n is the total number of renewable energy stations.

[0043] In some embodiments, the grid structure includes the geographical locations and shared transmission channels between the UHVDC converter stations.

[0044] DC groups are divided according to the geographical location and shared transmission channels between the UHVDC converter stations. That is, different DC groups are formed when the DC converter stations are located in the same regional power grid, the DC sending-end converter stations belong to the same provincial power grid, or the DC stations share a transmission channel.

[0045] In some embodiments, the first contribution rate index of each thermal power unit to the system voltage is calculated using the following formula (3):

[0046] in, is the voltage change of the jth DC bus node when the i-th thermal power unit is shut down, is the voltage change of the jth DC-connected busbar node before and after the fault, and J is the total number of DC-connected busbar nodes affected by the shutdown of the i-th thermal power unit.

[0047] The change in DC bus voltage before and after the fault is the absolute value of the difference between the DC bus voltage after the fault and the DC bus voltage before the fault.

[0048] In some embodiments, the voltage change of the jth DC-connected bus node when the i-th thermal power unit is shut down is calculated using the following formula (4):

[0049] in, is the mutual impedance from node i to node j, is the equivalent impedance at the machine end of the i-th node, is the open circuit voltage of the i-th node.

[0050] In some embodiments, a DC bus voltage change ΔU before and after the fault is calculated according to formula (5) when the system faces a DC bus continuous commutation failure fault impact resulting in a loss of DC bus power ΔP. DCj ΔU DCj =|U′ DCj -U DCj | (5);

[0051] Among them, U′ DCj is the voltage value of the jth DC bus after the fault, U DCj is the voltage value of the jth DC bus before the fault.

[0052] In some embodiments, it is assumed that nodes 1 to m in the AC system are synchronous machine nodes, and nodes m+1 to n are new energy nodes. The node injection current is provided by both the synchronous machine and the new energy, and the node voltage equation is shown in the following formula (6):

[0053] In some embodiments, when the thermal power plant connected to the i-th node is shut down, the voltages of multiple nodes in the system will be affected. The change in system voltage can be calculated using the following formula (7):

[0054] In some embodiments, the voltage change at any node j is calculated using the following formula (8):

[0055] in: is the mutual impedance from node i to node j, is the short-circuit current of the i-th node.

[0056] In some embodiments, the node voltage change of shutting down the generator is calculated using the following formula (9):

[0057] in: is the self-impedance of the node connected to the shut-down generator.

[0058] In some embodiments, the short-circuit current of the system is calculated using the following formula (10):

[0059] in: is the equivalent impedance at the machine end of the i-th node, is the open circuit voltage of the i-th node.

[0060] Then formula (8) can be rewritten as the following formula (11):

[0061] Then the first contribution rate index of each thermal power unit to the system voltage is obtained as follows (12):

[0062] in, is the voltage change modulus of the jth DC bus node when the i-th unit is shut down; V is the voltage change before and after the fault of the jth DC-connected busbar node, and J is the total number of DC-connected busbar nodes affected by the shutdown of generator node i. SEi The larger the value, the greater the impact of the thermal power plant on the system voltage.

[0063] In the above embodiment, for the sending-end power grid, the minimum operating level of its conventional units is solved by considering the contribution of the DC group fault and the thermal power plant units to the DC system voltage.

[0064] Step S103: If the output level is less than the load level, the power system is determined to be a receiving grid, and the minimum startup capacity of the thermal power generating units in the receiving grid is calculated based on the DC bus voltages, taking into account the voltage stability constraint.

[0065] FIG3 shows an exemplary flow chart of a method for calculating the minimum operating capacity of a thermal power generating unit in a receiving-end power grid considering voltage stability constraints according to an embodiment of the present disclosure.

[0066] As shown in FIG3 , in some embodiments, the minimum operating capacity of the thermal power generating units in the receiving-end power grid considering the voltage stability constraint is calculated based on the DC bus voltages, including:

[0067] Step S301: Obtaining and, based on the voltage change of each DC bus node and the DC multi-infeed short-circuit ratio when shutting down each thermal power unit, obtaining a second contribution index of each thermal power unit to the system transient voltage, and sorting all thermal power units in ascending order of the second contribution index to obtain a second thermal power unit shutdown sequence;

[0068] Step S302: Obtain and determine whether the DC multi-infeed short-circuit ratio or the renewable energy short-circuit ratio exceeds their respective threshold ranges. If not, shut down the thermal power units one by one according to the second thermal power unit shutdown sequence until the DC multi-infeed short-circuit ratio or the renewable energy short-circuit ratio exceeds their respective threshold ranges after one thermal power unit is shut down. The total capacity of the thermal power units in the previous shutdown is used as the minimum startup capacity of the thermal power units in the receiving power grid.

[0069] It should be understood that each of the DC multi-feed short-circuit ratio and the new energy short-circuit ratio has its own threshold range, which can be set according to specific needs. If each value of each item in the DC multi-feed short-circuit ratio and the new energy short-circuit ratio does not exceed the respective threshold ranges, the thermal power units are shut down one by one according to the shutdown sequence of the first thermal power unit, and the two data groups are iteratively calculated so that each value gradually approaches the respective threshold ranges. The case where the two data groups are closest to the threshold range and do not exceed the threshold range is selected as the iterative optimal solution, and the capacity of each thermal power unit under the iterative optimal solution is obtained and counted, and the total capacity of the thermal power unit is obtained as the minimum startup capacity of the thermal power unit of the receiving power grid. Among them, the calculation formula of the DC multi-feed short-circuit ratio and the new energy short-circuit ratio is the same as that in the previous step S102 and will not be repeated here.

[0070] In some embodiments, the second contribution index of each thermal power unit to the system transient voltage is calculated using the following formula (13):

[0071] in, MISCR is the voltage change of the jth DC bus node when the i-th thermal power unit is shut down. j is the multi-infeed short-circuit ratio of the j-th DC-connected busbar node, and J is the total number of DC-connected busbar nodes affected by the shutdown of the i-th thermal power unit.

[0072] in, and MISCR j The calculation formula is the same as that in the previous step S102.

[0073] In the above embodiment, for the receiving-end power grid, the minimum startup level of its conventional units is solved based on the contribution of the thermal power units to the system short-circuit ratio and the short-circuit ratio constraint of the DC system.

[0074] In the above embodiment, the power grid is judged as a sending-end power grid or a receiving-end power grid by the output level and the load level, and the minimum startup capacity of the thermal power units in the sending-end power grid and the minimum startup capacity of the thermal power units in the receiving-end power grid considering the voltage stability constraint are calculated respectively according to the different characteristics of the sending-end power grid and the receiving-end power grid. The calculation results are more accurate and reliable. The system output arrangement is performed according to the method provided in the embodiment of the present disclosure, which can ensure the stability of the system voltage. The system thermal power units are planned according to the method provided in the embodiment of the present disclosure. Combined with the planning of hydropower, nuclear power, pumped storage and other units in the system, it can be further applied to the planning of the scale of new energy consumption to avoid disorderly development of new energy.

[0075] Embodiments of the present disclosure

[0076] For the sending grid:

[0077] The 2030 plan projects the total installed capacity of the Northwest Power Grid to reach 720 GW, with coal-fired power, gas-fired power, and hydropower accounting for 230 GW, 12 GW, and 49 GW, respectively. Installed renewable energy capacity will reach 411 GW, including 145 GW of wind power and 266 GW of solar power, with a maximum load of 194 GW. There will be 20 direct current transmission lines, totaling 162 GW. The output level will exceed the load level by over 3,000 MW, making this a typical sending-end grid.

[0078] Based on the point of DC transmission within the same regional grid, the system is divided into four DC groups: seven from Northwest China to Central China, five from Northwest China to North China and Northwest China to East China, and three from Northwest to Southwest China. Taking the Northwest China to Central China DC group as an example, the group is further divided into the Gansu Hexi channel (Qishao + Tianzhong), the Northern Shaanxi DC group (Shaanwu + Yuheng + Henan), and the Qingning New DC group (Qingyu + Ningxiang + Kumtag + Henan + Tianzhong), based on shared transmission paths or electrical distances. When the system faced a consecutive commutation failure in these three DC groups, resulting in a loss of 16,000 / 16,000 / 32,000 MW of DC group power, the calculated changes in DC bus voltage before and after the failure are shown in Table 1.

[0079] Table 1: Northwest-Central China DC group with same transmission and reception

[0080] The system has 729 thermal power units. We calculated the primary contribution rate of each thermal power plant to the system voltage and ranked them from smallest to largest based on this primary contribution rate, forming the primary thermal power unit shutdown sequence. The top and bottom ten units in the first iteration are shown in Table 2.

[0081] Table 2 The top ten and bottom ten thermal power units in the first iteration of the voltage contribution index

[0082] As can be seen from Table 2, the units ranked higher contribute less to the system voltage and can be shut down first. When the capacity of the units in the system changes, the contribution of the thermal power units to the voltage will also change accordingly.

[0083] According to the national standard GB / T50064-2014 on the overvoltage tolerance capability of systems and electrical equipment, the calculation threshold is set as: the voltage change value is not higher than 0.3PU, and the new energy short-circuit ratio is not lower than 1.5.

[0084] During the first calculation, the maximum system voltage change was 0.2735, and the minimum renewable energy short-circuit ratio was 1.5815, both below the threshold. This indicates that the system has sufficient thermal power generation capacity. Therefore, the number of thermal power generation units was gradually reduced according to the thermal power generation shutdown sequence, and the calculation was repeated. After 405 iterations, the maximum node voltage change was 0.2863 (new Hami replacement), indicating that the system's renewable energy short-circuit ratio was close to the critical value of 1.5. Table 3 shows a comparison of the renewable energy short-circuit ratios, sorted from smallest to largest, during the 405th and 406th iterations.

[0085] Table 3 New energy short-circuit ratio calculated for the 405th and 406th iterations

[0086] Therefore, the system thermal power unit capacity of 188.75GW at the 405th calculation is taken as the minimum startup capacity that the system should retain.

[0087] Repeat the above steps to calculate the minimum power generation capacity that the system should retain in the event of a fault in the Hexi Channel DC group and the Shaanxi Northern DC group, which are 160.75GW and 145.75GW respectively.

[0088] Therefore, subject to the constraints of cross-regional DC voltage stability, the minimum thermal power capacity of the Northwest Power Grid in 2030 will be 188.75GW.

[0089] At this thermal power scale, DC group fault verification was performed, and the planning scheme was able to meet voltage stability constraints. Figure 4 shows a schematic diagram of the voltages at key bus nodes in the Qingningxin DC group under the condition of a three-phase commutation failure fault, according to one embodiment of the present disclosure. Figure 4(a) shows the voltages at Qingqingnan and Ningtiandu, and Figure 4(b) shows the voltages at Guokumu and Xinhamichang.

[0090] For the receiving power grid:

[0091] The planned peak load of the East China power grid in 2030 is expected to reach 487 GW. Considering the addition of three DC lines from Badain Jaran to Lianyungang, Ulan Buh to Jiangsu, and Ulan Buh to Anhui, part of the nationally planned "one AC and four DC" and "twelve DC" projects, the total number of DC lines receiving power from outside the region will reach 18, with a total capacity of 125.8 GW, representing a typical receiving-end grid. Total installed capacity will reach 706 GW, including 249 GW of coal-fired power and 68 GW of gas-fired power. Installed renewable energy capacity will reach 272.6 GW, including 95 GW of wind power and 177 GW of solar power. The installed capacity of the grid's power sources is shown in Table 4.

[0092] Table 4 Installed power capacity of East China power grid in 2030

[0093] Unit: GW

[0094] The short-circuit ratios of all DC power systems in the East China 2030 planning scheme are calculated and shown in Table 5.

[0095] Table 5 Short-circuit ratio of DC multi-infeed in East China Power Grid in 2030

[0096] The second contribution rate of thermal power units to the system short-circuit ratio was calculated, and the units were ranked from smallest to largest. Because this indicator is dynamically adjusted, and due to space limitations, only the top and bottom ten units from the first calculation are presented, as shown in Table 6.

[0097] Table 6 The top ten and bottom ten thermal power generating units in East China Power Grid in terms of their contribution to the system during the first iteration calculation

[0098] Using a developed minimum startup procedure for the receiving-end grid that considers inter-regional DC voltage stability, the highest-ranked thermal power units were shut down according to the order shown in Table 6. The DC multi-infeed short-circuit ratio and the renewable energy short-circuit ratio were recalculated. After 483 iterations, the thermal power unit capacity reached 112 GW, the renewable energy short-circuit ratio had a minimum value of 3.46 (at the Suxindong G2 node), and the DC multi-infeed short-circuit ratio reached a critical value close to 2, as shown in Table 7.

[0099] Table 7 System DC short-circuit ratio for the 483rd iteration when the thermal power unit capacity is 112GW

[0100] Therefore, the thermal power generation capacity of 112.7 GW at iteration 482 is taken as the minimum thermal power generation capacity of the system subject to voltage constraints. Under this thermal power capacity, a DC group fault check is performed, and the planning scheme can meet the voltage stability constraints.

[0101] FIG5 shows a schematic structural diagram of an apparatus for determining the minimum operating capacity of a thermal power generation unit based on voltage stability according to an embodiment of the present disclosure.

[0102] As shown in FIG5 , the device includes:

[0103] The data acquisition part 101 is configured to acquire the load level and output level of the power system;

[0104] The sending-end grid processing part 102 is configured to determine that the power system is a sending-end grid if the difference between the output level and the load level is greater than a preset capacity, and calculate the minimum operating capacity of the thermal power units in the sending-end grid considering the voltage stability constraint;

[0105] The receiving grid processing part 103 is configured to determine that the power system is a receiving grid if the output level is less than the load level, and calculate the minimum operating capacity of the thermal power units in the receiving grid considering the voltage stability constraint.

[0106] In some embodiments, calculating the minimum operating capacity of thermal power units in the sending-end power grid considering voltage stability constraints includes:

[0107] Obtain and divide the power system into several DC groups based on the grid structure;

[0108] Each faulty DC group among the multiple DC groups is selected as the target DC group in turn, and the next step is performed until all faulty DC groups in the power system are traversed:

[0109] Obtain and, based on the voltage changes of each DC bus before and after the fault and the voltage changes of each DC-connected bus node when shutting down each thermal power unit, obtain a first contribution rate index of each thermal power unit to the system voltage, and sort all the thermal power units in ascending order of the first contribution rate index to obtain a first thermal power unit shutdown sequence; obtain and determine whether any one of the voltage changes of each DC bus before and after the fault, the DC multi-feed short-circuit ratio, and the new energy short-circuit ratio exceeds the respective threshold ranges; if not, shut down the thermal power units one by one according to the first thermal power unit shutdown sequence until, after shutting down one thermal power unit, any one of the voltage changes of the DC bus before and after the fault, the DC multi-feed short-circuit ratio, and the new energy short-circuit ratio exceeds the respective threshold ranges, and use the total capacity of the previous thermal power unit as the minimum startup capacity of the system considering the voltage stability constraint after the target DC group fault;

[0110] The maximum value is selected from all the system minimum startup capacities considering the voltage stability constraint after the DC group fault as the minimum startup capacity of the thermal power unit in the sending-end power grid.

[0111] In some embodiments, the grid structure includes the geographical locations and shared transmission channels between the UHVDC converter stations.

[0112] In some embodiments, the first contribution rate index of each thermal power unit to the system voltage is calculated using the following formula (3):

[0113] in, is the voltage change of the jth DC bus node when the i-th thermal power unit is shut down, is the voltage change of the jth DC-connected busbar node before and after the fault, and J is the total number of DC-connected busbar nodes affected by the shutdown of the i-th thermal power unit.

[0114] In some embodiments, calculating the minimum operating capacity of a thermal power generating unit in a receiving-end power grid considering voltage stability constraints includes:

[0115] Obtaining and, based on the voltage change of each DC bus node and the DC multi-infeed short-circuit ratio when shutting down each thermal power unit, obtaining a second contribution index of each thermal power unit to the system transient voltage, and sorting all the thermal power units in ascending order of the second contribution index to obtain a second thermal power unit shutdown sequence;

[0116] Obtain and determine whether the DC multi-infeed short-circuit ratio or the renewable energy short-circuit ratio exceeds their respective threshold ranges. If not, shut down the thermal power units one by one according to the second thermal power unit shutdown sequence until the DC multi-infeed short-circuit ratio or the renewable energy short-circuit ratio exceeds their respective threshold ranges. The total capacity of the previous thermal power units is used as the minimum startup capacity of the thermal power units in the receiving power grid.

[0117] In some embodiments, the second contribution index of each thermal power unit to the system transient voltage is calculated using the following formula (13):

[0118] in, MISCR is the voltage change of the jth DC bus node when the i-th thermal power unit is shut down. j is the multi-infeed short-circuit ratio of the j-th DC-connected busbar node, and J is the total number of DC-connected busbar nodes affected by the shutdown of the i-th thermal power unit.

[0119] In some implementations, the change in the DC bus voltage before and after the fault is the absolute value of the difference between the DC bus voltage after the fault and the DC bus voltage before the fault.

[0120] In some embodiments, the voltage change of the jth DC-connected bus node when the i-th thermal power unit is shut down is calculated using the following formula (11):

[0121] in, is the mutual impedance from node i to node j, is the equivalent impedance at the machine end of the i-th node, is the open circuit voltage of the i-th node.

[0122] In some embodiments, the DC multi-infeed short-circuit ratio of the j-th DC-connected bus node is calculated using the following formula (1):

[0123] Among them, S j is the short-circuit capacity of commutation bus j, P Dj is the rated power of DC j, MIIF jk is the multi-feed interaction factor between DC converter station j and converter station k, P Dk is the rated power of DC k, and m is the total number of DC.

[0124] In some embodiments, the new energy short-circuit ratio of the grid-side access point of the new energy power generation equipment or the grid-connected bus node i of the station is calculated using the following formula (2):

[0125] in, is the nominal voltage of the i-th grid-connected busbar node, is the voltage generated by the renewable energy power generation at the i-th node, and the subscript RE represents the renewable energy power generation equipment or station. The equivalent impedance calculated for the system side between the main grid equivalent power source i and the corresponding grid connection point is: is the actual apparent power of the new energy injected into the i-th new energy grid-connected bus node, is the actual apparent power of the new energy injected into the j-th new energy grid-connected bus node, is the complex power conversion factor between the renewable energy grid-connected busbars i and j, and n is the total number of renewable energy stations.

[0126] In the above embodiment, the power grid is judged as a sending-end power grid or a receiving-end power grid based on the output level and load level, and the minimum startup capacity of the thermal power units in the sending-end power grid and the minimum startup capacity of the thermal power units in the receiving-end power grid, taking into account the voltage stability constraint, are calculated based on the different characteristics of the sending-end power grid and the receiving-end power grid, respectively. The calculation results are more accurate and reliable. System output arrangement according to the method provided in the embodiment of the present disclosure can ensure system voltage stability. System thermal power unit planning according to the method provided in the embodiment of the present disclosure, combined with the planning of hydropower, nuclear power, pumped storage and other units in the system, can be further applied to the planning of the scale of new energy consumption to avoid disorderly development of new energy.

[0127] It should be noted that the apparatus provided in the above embodiments is merely illustrated by the division of the above functional modules when implementing its functions. In actual applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the apparatus and method embodiments provided in the above embodiments are based on the same concept, and their specific implementation process is detailed in the method embodiments.

[0128] The embodiments of the present disclosure further provide a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the method for determining the minimum startup capacity of a thermal power unit based on voltage stability provided in the above embodiments is implemented.

[0129] An embodiment of the present disclosure also provides an electronic device, comprising: a processor; a memory configured to store processor-executable instructions; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the method for determining the minimum startup capacity of a thermal power unit based on voltage stability provided in the above-mentioned embodiments.

[0130] The embodiments of the present disclosure further provide a computer program product, which includes a computer program or instructions. When the computer program or instructions are run on a computer, the computer is enabled to execute the methods provided in the above embodiments.

[0131] The present disclosure has been described with reference to a few embodiments. However, it is readily apparent to those skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the present disclosure, as defined by the appended patent claims.

[0132] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / the [means, component, etc.]" are to be interpreted openly as referring to at least one instance of the means, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily need to be performed in the exact order disclosed, unless explicitly stated otherwise.

[0133] Those skilled in the art will appreciate that embodiments of the present disclosure may be provided as methods, systems, or computer program products. Thus, the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present disclosure may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0134] The present disclosure is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present disclosure. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0135] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0136] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure and not to limit them. Although the present disclosure has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present disclosure can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present disclosure should be included in the scope of protection of the claims of the present disclosure.

Claims

1. A method for determining the minimum operating capacity of a thermal power unit based on voltage stability, the method comprising: Step S101: Obtain the load level and output level of the power system; Step S102: if the difference between the output level and the load level is greater than a preset capacity, the power system is determined to be a sending-end power grid, and the minimum startup capacity of the thermal power generating units of the sending-end power grid considering the voltage stability constraint is calculated; Step S103: If the output level is less than the load level, the power system is determined to be a receiving power grid, and the minimum startup capacity of the thermal power generating units of the receiving power grid considering the voltage stability constraint is calculated.

2. According to the method of claim 1, the calculation of the minimum startup capacity of the thermal power generating units in the sending-end power grid considering the voltage stability constraint comprises: Step S201: Obtain and divide the power system into a number of DC groups based on the grid structure; Each faulty DC group among the plurality of DC groups is selected as a target DC group in turn, and steps S202 to S203 are performed until all faulty DC groups in the power system are traversed: Step S202: obtaining and obtaining a first contribution rate index of each thermal power unit to the system voltage based on the voltage change of each DC bus before and after the fault and the voltage change of each DC-connected bus node when shutting down each thermal power unit, and sorting all the thermal power units in ascending order of the first contribution rate index to obtain a shutdown sequence of the first thermal power unit; Step S203: obtaining and judging whether any one of the DC bus voltage variation before and after the fault, the DC multi-feed short-circuit ratio and the new energy short-circuit ratio exceeds the respective threshold ranges; if not, shutting down the thermal power units one by one according to the first thermal power unit shutdown sequence until after shutting down one thermal power unit, any one of the DC bus voltage variation before and after the fault, the DC multi-feed short-circuit ratio and the new energy short-circuit ratio exceeds the respective threshold ranges, and taking the total capacity of the previous thermal power unit as the minimum startup capacity of the system considering the voltage stability constraint after the target DC group fault; Step S204: Select the maximum value from all the system minimum startup capacities that consider the voltage stability constraint after the DC group fault as the minimum startup capacity of the thermal power unit in the sending-end power grid.

3. According to the method of claim 2, the grid structure includes the geographical location and shared transmission channel conditions between each UHV DC converter station.

4. According to the method of claim 2, the first contribution rate index of each thermal power unit to the system voltage is calculated by the following formula: in, is the voltage change of the jth DC-connected bus node when the i-th thermal power unit is shut down, is the voltage change before and after the fault of the jth DC-connected bus node, and J is the total number of DC-connected bus nodes affected by the shutdown of the i-th thermal power unit.

5. According to the method of claim 1, the calculation of the minimum startup capacity of the thermal power generating units of the receiving-end power grid considering the voltage stability constraint comprises: Step S301: obtaining and based on the voltage change of each DC-connected bus node and the DC multi-feed short-circuit ratio when shutting down each thermal power unit, obtaining a second contribution index of each thermal power unit to the system transient voltage, and sorting all the thermal power units in ascending order of the second contribution index to obtain a second thermal power unit shutdown sequence; Step S302: Obtain and determine whether the DC multi-infeed short-circuit ratio or the renewable energy short-circuit ratio exceeds their respective threshold ranges; if not, shut down the thermal power units one by one according to the second thermal power unit shutdown sequence until after shutting down one thermal power unit, the DC multi-infeed short-circuit ratio or the renewable energy short-circuit ratio exceeds their respective threshold ranges, and use the total capacity of the previous thermal power unit as the minimum startup capacity of the thermal power unit in the receiving power grid.

6. According to the method of claim 5, the second contribution index of each thermal power unit to the system transient voltage is calculated by the following formula: in, MISCR is the voltage change of the jth DC-connected bus node when the i-th thermal power unit is shut down. j is the multi-infeed short-circuit ratio of the jth DC-connected bus node, and J is the total number of DC-connected bus nodes affected by the shutdown of the i-th thermal power unit.

7. According to the method of claim 2 or 4, the change in the DC bus voltage before and after the fault is the absolute value of the difference between the DC bus voltage after the fault and the DC bus voltage before the fault.

8. According to the method of claim 4 or 6, the voltage change of the jth DC-connected bus node when shutting down the i-th thermal power unit is calculated by the following formula: in, is the mutual impedance of node i to node j, is the equivalent impedance of the i-th node machine end, is the open circuit voltage of the ith node.

9. According to the method of claim 2, 5 or 6, the DC multi-infeed short-circuit ratio of the j-th DC-connected bus node is calculated using the following formula: in, S j is the short-circuit capacity of commutation bus j, P Dj is the rated power of DC j, MIIF jk is the multi-feed interaction factor of DC converter station j to converter station k, P Dk k is the rated power of DC, and m is the total number of DC.

10. According to the method of claim 2 or 5, the new energy short-circuit ratio of the grid-side access point of the new energy power generation equipment or the grid-connected bus node i of the station is calculated by the following formula: in, is the nominal voltage of the ith grid-connected bus node, is the voltage generated by the renewable energy power generation at the i-th node, and the subscript RE represents the renewable energy power generation equipment or station. The equivalent impedance calculated for the system side between the main grid equivalent power source i and the corresponding grid connection point is: is the actual apparent power of the new energy injected into the i-th new energy grid-connected bus node, is the actual apparent power of the new energy injected into the jth new energy grid-connected bus node, is the complex power conversion factor between the renewable energy grid-connected busbars i and j, and n is the total number of renewable energy stations.

11. A device for determining the minimum operating capacity of a thermal power unit based on voltage stability, the device comprising: The data acquisition part 101 is configured to acquire the load level and output level of the power system; The sending-end grid processing part 102 is configured to determine that the power system is a sending-end grid if the difference between the output level and the load level is greater than a preset capacity, and calculate the voltage stability constraint. Minimum startup capacity of thermal power units in the sending-end power grid; The receiving grid processing part 103 is configured to determine that the power system is a receiving grid if the output level is less than the load level, and calculate the minimum startup capacity of the thermal power units in the receiving grid considering the voltage stability constraint.

12. A computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the method according to any one of claims 1 to 10 is implemented.

13. An electronic device, comprising: processor; a memory configured to store instructions executable by the processor; The processor is configured to read the executable instructions from the memory and execute the executable instructions to implement the method according to any one of claims 1 to 10.

14. A computer program product, comprising a computer program or instructions, which, when the computer program or instructions are run on a computer, enable the computer to perform the method according to any one of claims 1 to 10.

Images