Power grid inertia demand online evaluation method, device and equipment and storage medium

Abstract

The invention belongs to the field of power system automation, and discloses a power grid inertia demand online evaluation method, device and equipment and a storage medium, and the method comprises the steps: firstly achieving the accurate evaluation of the current system inertia of a power grid through comprehensively considering the current synchronous machine type resource inertia, new energy plant station inertia and load side inertia of the power grid; then, the current system minimum inertia of the power grid is accurately obtained by combining the evaluation of the multi-dimensional system minimum inertia based on the maximum frequency change rate, the lowest frequency point and the minimum inertia constant, and then the current system inertia of the power grid and the system minimum inertia are combined; according to the invention, whether the current inertia level of the power grid is in the safety level range can be judged, a specific inertia difference can be given when the current inertia level of the power grid is insufficient, and the determination of the current inertia demand of the power grid under different demands can be realized based on the preset inertia margin demand. Quantitative targeted guidance can be provided for dispatching operators, and the safety of a power grid is guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of power system automation, and relates to an online evaluation method, device, equipment and storage medium for grid inertia demand. Background Art

[0002] Traditional synchronous machines are directly connected to the power grid. Their constant rotational speed operation has stable kinetic energy, that is, inertia response ability, and can provide inertia support when the grid frequency changes to ensure frequency stability. Synchronous machines have the characteristics of voltage sources and can instantaneously share disturbance power. When there is a power deficit (surplus) in the system, it will be directly reflected in the sudden increase (decrease) of electromagnetic power. The generator rotor responds to the deviation between electromagnetic power and mechanical power caused by system power changes by releasing or absorbing kinetic energy, supports system power balance, and suppresses frequency changes.

[0003] The energy transition has promoted the large-scale grid connection of new energy. New energy will gradually replace traditional generators as the main energy source of the power system, and a large number of synchronous machines are replaced by new energy. However, new energy such as wind power and photovoltaic power does not have the rotational inertia similar to that of synchronous machines. For example, the variable frequency device of the fan decouples the fan speed from the grid frequency. When the grid frequency changes, the fan still follows the maximum power tracking instruction to deliver power to the grid, does not respond to the grid frequency change, and does not actively provide inertia support to the system, resulting in a decline in the system's inertia support ability and poor frequency stability. In addition, the output of new energy has strong volatility and intermittency. If the output fluctuates greatly, the system may have problems with the stability of the regional power grid due to lack of inertia support. The reduction of system inertia makes it possible that once a disturbance such as a unit trip or DC blocking occurs in the power grid, the power grid will experience a rapid frequency drop due to the reduction of system inertia and trigger a series of cascading power outage faults, threatening the safe operation of the power grid. Therefore, how to accurately perceive the current inertia level of the power grid and clarify its specific inertia demand has become an urgent problem to be solved.

[0004] At present, although the industry has proposed an evaluation method for the minimum inertia of the system, this method mainly considers the maximum frequency change rate and the lowest frequency drop point. In many cases, it can only give the minimum inertia value that the system should have, and cannot accurately obtain the current inertia level of the system. Furthermore, it is impossible to accurately evaluate whether the current inertia of the system meets the minimum inertia demand, and it is also difficult to quantitatively clarify the inertia demand difference when the system inertia is insufficient, and it cannot provide strong support for the dispatching operation of the power grid. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide an online evaluation method, device, equipment and storage medium for grid inertia demand.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect of the present invention, an online evaluation method for grid inertia demand is provided, including: obtaining and superimposing the inertia of synchronous machine type resources, the inertia of new energy power plants, and the inertia of the load side in the current grid to obtain the current system inertia of the grid; obtaining the minimum system inertia of the current grid based on the maximum frequency change rate, the lowest frequency point, and the minimum inertia constant, and taking the minimum value to obtain the current system minimum inertia of the grid; and obtaining the current inertia demand of the grid based on a preset inertia margin demand, in combination with the current system inertia and the system minimum inertia of the grid.

[0008] Optionally, the obtaining of the inertia of synchronous machine type resources in the current grid includes: obtaining the rated power and inertia constant of each operating synchronous generator set in the current grid and multiplying them to obtain the inertia of each operating synchronous generator set in the current grid, and superimposing them to obtain the inertia of the synchronous generator sets in the current grid; obtaining the rated power and inertia constant of each operating synchronous condenser in the current grid and multiplying them to obtain the inertia of each operating synchronous condenser in the current grid, and superimposing them to obtain the inertia of the synchronous condensers in the current grid; obtaining the rated power and inertia constant of each operating unit in each pumped storage power station in the current grid and multiplying them to obtain the inertia of each operating unit in each pumped storage power station in the current grid, and superimposing them to obtain the inertia of the pumped storage power stations in the current grid; and superimposing the inertia of the synchronous generator sets, the inertia of the synchronous condensers, and the inertia of the pumped storage power stations in the current grid to obtain the inertia of synchronous machine type resources in the current grid.

[0009] Optionally, obtaining the inertia of new energy power plants in the current grid includes: obtaining the actual output and inertia constant of each target new energy power plant in the current grid and multiplying them to obtain the inertia of each target new energy power plant in the current grid, and superimposing them to obtain the inertia of new energy power plants in the current grid; wherein, the target new energy power plant is a new energy power plant whose ratio of actual output to rated installed capacity is greater than a preset output threshold value.

[0010] Optionally, obtaining the inertia of the load side in the current grid includes: obtaining the unit load inertia value and the total load in the current grid and multiplying them to obtain the inertia of the load side in the current grid; wherein, the unit load inertia value in the current grid is calculated based on the load model used in the current grid stability calculation, in combination with the latest disturbance calculation.

[0011] Optionally, obtaining the minimum system inertia of the current grid based on the minimum inertia constant includes: obtaining the minimum inertia constant and the total load in the current grid and multiplying them to obtain the minimum system inertia of the current grid based on the minimum inertia constant.

[0012] Optionally, obtaining the current grid inertia demand based on the preset inertia margin requirement and combining the current system inertia and the minimum system inertia of the grid includes: when the inertia margin requirement is to meet the basic system inertia requirement, the current grid inertia demand is obtained in the following manner: when the current system inertia of the grid is not less than the minimum system inertia, the current grid inertia demand is 0; when the current grid inertia demand is less than the minimum system inertia, the current grid inertia demand is: (the current minimum system inertia of the grid - the current system inertia of the grid) × a preset coefficient K; where K is not less than 1; when the inertia margin requirement is that the inertia is abundant and not lower than the preset inertia abundance threshold M, the current grid inertia demand is obtained in the following manner: when the current system inertia of the grid is not less than the minimum system inertia, calculate the current grid inertia abundance R, when R is not less than M, the current grid inertia demand is 0; when R is less than M, the current grid inertia demand is: (the current minimum system inertia of the grid / (1 - M)) - the current system inertia of the grid; when the current system inertia of the grid is less than the minimum system inertia, the current grid inertia demand is: (the current minimum system inertia of the grid / (1 - M)) - the current system inertia of the grid.

[0013] In a second aspect of the present invention, there is provided an on-line evaluation device for grid inertia demand, including: a system inertia evaluation module, configured to obtain the inertia of the synchronous machine type resources, the inertia of the new energy power plant, and the inertia of the load side of the current grid and superimpose them to obtain the current system inertia of the grid; a system minimum inertia evaluation module, configured to obtain the minimum system inertia of the current grid based on the maximum frequency change rate, the lowest frequency point, and the minimum inertia constant and take the minimum value to obtain the current system minimum inertia of the grid; an inertia demand evaluation module, configured to obtain the current grid inertia demand based on the preset inertia margin requirement and combining the current system inertia and the minimum system inertia of the grid.

[0014] Optionally, obtaining the inertia of the synchronous machine type resources of the current grid includes: obtaining the rated power and inertia constant of each operating synchronous generator set in the current grid and multiplying them to obtain the inertia of each operating synchronous generator set in the current grid and superimposing them to obtain the inertia of the synchronous generator sets in the current grid; obtaining the rated power and inertia constant of each operating synchronous condenser in the current grid and multiplying them to obtain the inertia of each operating synchronous condenser in the current grid and superimposing them to obtain the inertia of the synchronous condensers in the current grid; obtaining the rated power and inertia constant of each operating unit of each pumped storage power station in the current grid and multiplying them to obtain the inertia of each operating unit of each pumped storage power station in the current grid and superimposing them to obtain the inertia of the pumped storage power stations in the current grid; superimposing the inertia of the synchronous generator sets, the inertia of the synchronous condensers, and the inertia of the pumped storage power stations in the current grid to obtain the inertia of the synchronous machine type resources of the current grid.

[0015] Optionally, obtaining the current inertia of new energy power plants in the power grid includes: obtaining the actual output and inertia constant of each target new energy power plant in the power grid currently, multiplying them to obtain the inertia of each target new energy power plant in the power grid currently, and adding them up to obtain the current inertia of new energy power plants in the power grid; where the target new energy power plant is a new energy power plant whose ratio of actual output to rated installed capacity is greater than a preset output threshold value.

[0016] Optionally, obtaining the current inertia on the load side of the power grid includes: obtaining the current unit load inertia value and the total load of the power grid currently, multiplying them to obtain the current inertia on the load side of the power grid; where the current unit load inertia value of the power grid is calculated based on the load model used in the current stability calculation of the power grid and combined with the latest disturbance calculation.

[0017] Optionally, obtaining the current system minimum inertia based on the minimum inertia constant of the power grid includes: obtaining the current minimum inertia constant and the total load of the power grid currently, multiplying them to obtain the current system minimum inertia based on the minimum inertia constant of the power grid.

[0018] Optionally, obtaining the current inertia demand of the power grid by combining the current system inertia and system minimum inertia of the power grid based on a preset inertia margin demand includes: when the inertia margin demand is to meet the basic inertia demand of the system, the current inertia demand of the power grid is obtained by the following method: when the current system inertia of the power grid is not less than the system minimum inertia, the current inertia demand of the power grid is 0; when the current inertia demand of the power grid is less than the system minimum inertia, the current inertia demand of the power grid is: (the current system minimum inertia of the power grid - the current system inertia of the power grid) × a preset coefficient K; where K is not less than 1; when the inertia margin demand is that the inertia is abundant and not less than a preset inertia abundance threshold value M, the current inertia demand of the power grid is obtained by the following method: when the current system inertia of the power grid is not less than the system minimum inertia, calculate the current inertia abundance R of the power grid, when R is not less than M, the current inertia demand of the power grid is 0; when R is less than M, the current inertia demand of the power grid is: (the current system minimum inertia of the power grid / (1 - M)) - the current system inertia of the power grid; when the current system inertia of the power grid is less than the system minimum inertia, the current inertia demand of the power grid is: (the current system minimum inertia of the power grid / (1 - M)) - the current system inertia of the power grid.

[0019] In the third aspect of the present invention, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the above-mentioned online evaluation method for power grid inertia demand are implemented.

[0020] In a fourth aspect of the present invention, there is provided a computer-readable storage medium storing a computer program which, when executed by a processor, implements the steps of the above-mentioned online evaluation method for grid inertia requirements.

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

[0022] The online evaluation method for grid inertia requirements of the present invention first accurately evaluates the current system inertia of the grid by comprehensively considering the inertia of synchronous machine type resources, the inertia of new energy power plants, and the inertia of the load side in the grid. Then, by combining the evaluation of the system minimum inertia based on the maximum frequency change rate, the minimum frequency point, and the minimum inertia constant in multiple dimensions, the current system minimum inertia of the grid is accurately obtained. Furthermore, by combining the current system inertia and the system minimum inertia of the grid, it is not only possible to determine whether the current inertia level of the grid is within the safe level range, but also to give a specific inertia difference when the current inertia level of the grid is insufficient, and the current inertia requirements of the grid under different requirements can be determined based on the preset inertia margin requirements, which can provide quantitative and targeted guidance for dispatching and operation personnel during grid inertia regulation, thereby effectively improving the safe operation level of the grid and ensuring grid safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flowchart of the online evaluation method for grid inertia requirements according to an embodiment of the present invention.

[0024] Figure 2 It is a schematic diagram of the calculation principle of the current system inertia of the grid according to an embodiment of the present invention.

[0025] Figure 3 It is a schematic diagram of the calculation principle of the current system minimum inertia of the grid according to an embodiment of the present invention.

[0026] Figure 4 It is a flowchart of the determination of the current inertia requirements of the grid according to an embodiment of the present invention.

[0027] Figure 5 It is a block diagram of the structure of the online evaluation system for grid inertia requirements according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] It should be noted that the terms "first", "second", etc. in the description, claims and the above-mentioned drawings of the present invention are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such data used can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that comprises a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0030] The present invention will be further described in detail below with reference to the accompanying drawings:

[0031] See Figure 1 , in an embodiment of the present invention, an online evaluation method for grid inertia demand is provided, which can give specific grid inertia demand, and further provide quantitative and targeted guidance for dispatching and operation personnel when adjusting the inertia of the grid, and can effectively improve the safe operation level of the grid and ensure the safety of the grid.

[0032] Specifically, the online evaluation method for grid inertia demand of the present invention includes the following steps:

[0033] S1: Obtain and superimpose the inertia of synchronous machine type resources, the inertia of new energy power plants, and the inertia of the load side in the current grid to obtain the current system inertia of the grid.

[0034] S2: Obtain the minimum system inertia of the current grid based on the maximum frequency change rate, the lowest frequency point, and the minimum inertia constant, and take the minimum value to obtain the current system minimum inertia of the grid.

[0035] S3: Based on the preset inertia margin requirement, combine the current system inertia and the system minimum inertia of the grid to obtain the current inertia demand of the grid.

[0036] The on-line evaluation method for the grid inertia demand of the present invention first accurately evaluates the current system inertia of the grid by comprehensively considering the inertia of synchronous machine type resources, the inertia of new energy power plants, and the inertia of the load side in the current grid. Then, by combining the evaluation of the system minimum inertia based on the maximum frequency change rate, the lowest frequency point, and the minimum inertia constant in multiple dimensions, the current system minimum inertia of the grid is accurately obtained. Furthermore, by combining the current system inertia and the system minimum inertia of the grid, it is not only possible to determine whether the current inertia level of the grid is within the safe level range, but also to give a specific inertia difference when the current inertia level of the grid is insufficient. Moreover, based on the preset inertia margin demand, the current grid inertia demand under different demands can be determined, which can provide quantitative and targeted guidance for dispatching and operation personnel when adjusting the grid inertia, thereby effectively improving the safe operation level of the grid and ensuring grid safety.

[0037] Explanatory, by accurately evaluating the grid inertia demand, on the one hand, it can effectively analyze whether there is a problem of insufficient inertia in the entire grid, facilitating the dispatching personnel to timely adjust the dispatching strategy. At the same time, through the calculation and analysis of the inertia demand, the specific current inertia demand is clarified, providing quantitative guidance for the dispatching personnel to carry out inertia adjustment. This can make the entire operation more targeted and effectively prevent load shedding events caused by a large drop in the grid frequency after a large disturbance occurs at a low inertia level, reducing the occurrence of power outage accidents.

[0038] Currently, the main method for calculating the system inertia of the grid is to count the inertia of all synchronous generators operating in parallel and use the aggregated result as the total system inertia. This calculation method can more accurately reflect the true level of system inertia in the context of synchronous machines as the main power source. However, with the large-scale grid connection of a high proportion of new energy, the proportion of synchronous machine power sources gradually decreases. In this context, it is necessary to fully consider the inertia resources of the entire grid to obtain accurate grid inertia. See Figure 2 , the overall idea of this application is to summarize and analyze according to three aspects: the inertia of synchronous machine type resources, the inertia of new energy power plants, and the inertia of the load side.

[0039] In a possible implementation manner, the obtaining of the inertia of the current synchronous machine type resources of the power grid includes: obtaining the rated power and inertia constant of each in-operation synchronous generator set in the current power grid and multiplying them to obtain the inertia of each in-operation synchronous generator set in the current power grid, and then adding them up to obtain the inertia of the synchronous generator sets in the current power grid; obtaining the rated power and inertia constant of each in-operation synchronous condenser in the current power grid and multiplying them to obtain the inertia of each in-operation synchronous condenser in the current power grid, and then adding them up to obtain the inertia of the synchronous condensers in the current power grid; obtaining the rated power and inertia constant of each in-operation unit of each pumped-storage power station in the current power grid and multiplying them to obtain the inertia of each in-operation unit of each pumped-storage power station in the current power grid, and then adding them up to obtain the inertia of the pumped-storage power stations in the current power grid; adding up the inertia of the synchronous generator sets, the inertia of the synchronous condensers, and the inertia of the pumped-storage power stations in the current power grid to obtain the inertia of the current synchronous machine type resources of the power grid.

[0040] Explanatory, first of all, according to the in-operation status of the synchronous generator sets in each power plant of the power grid, calculate the kinetic energy of each in-operation synchronous generator set, and this kinetic energy value is its inertia. The inertia of each synchronous generator set is directly obtained by multiplying the inertia constant and the rated power, and then the total inertia of the synchronous generator sets in various power plants such as hydropower plants, thermal power plants, and nuclear power plants is statistically summarized. Since the in-operation of each synchronous generator set is executed according to the control instructions of the dispatching, therefore, the inertia of the synchronous generator sets needs to be continuously calculated in a rolling manner at a certain time interval, for example, calculated once every 15 minutes, to ensure that its state can match the most real state of the current power grid and ensure that the obtained is the inertia of the current synchronous generator sets.

[0041] Secondly, according to the operation status of the synchronous condensers, calculate the value obtained by multiplying the rated power and the inertia constant of all in-operation synchronous condensers to obtain its kinetic energy, that is, the inertia of the synchronous condensers. The reason for separately calculating the synchronous condensers is that although the synchronous condensers also have rotational kinetic energy like the synchronous generator sets, the synchronous condensers do not provide active power. The synchronous condensers maintain the frequency stability of the power grid by providing reactive power support, but essentially also provide kinetic energy support, so the synchronous condensers also have inertia.

[0042] There are two different stages of power generation and power consumption in a pumped-storage power station. During the power generation stage, the pumped-storage power station is essentially a hydropower plant. Therefore, the inertia of each in-operation unit is obtained by multiplying the rated power of each in-operation unit and the inertia constant of each in-operation unit, and then the inertia of all in-operation units of the pumped-storage power station is summarized to obtain the inertia of the pumped-storage power station. The inertia of all pumped-storage power stations within the entire power grid is summarized to obtain the inertia of the pumped-storage power stations in the current power grid. If the pumped-storage power station is in the power consumption stage, it is similar to a motor like the synchronous generator sets at this time, but its kinetic energy remains unchanged, so the inertia that can be provided remains unchanged. Therefore, regardless of the operating mode of the pumped-storage power station, as long as it is connected to the power grid, its inertia can be directly obtained.

[0043] Summarize the current synchronous generator inertia, synchronous condenser inertia, and pumped-storage power station inertia in the power grid to obtain the inertia of synchronous machine type resources in the power grid at the current moment. Here, "current" means that this result is calculated continuously and recursively at a certain time interval. For example, it is calculated every 15 minutes. Each time it is calculated, the synchronous generator inertia, synchronous condenser inertia, and pumped-storage power station inertia will be calculated recursively respectively.

[0044] In a possible implementation, obtaining the inertia of current new energy power plants in the power grid includes: obtaining the actual output and inertia constant of each target new energy power plant in the power grid and multiplying them to obtain the inertia of each target new energy power plant in the power grid, and then superimposing them to obtain the inertia of current new energy power plants in the power grid; where the target new energy power plant is a new energy power plant whose ratio of actual output to rated installed capacity is greater than a preset output threshold.

[0045] Explanatorily, neither wind power plants nor photovoltaic power plants have direct rotational inertia. The inertia mentioned here is a virtual inertia, or an equivalent inertia. The unit is the same as that of synchronous machine inertia, which is megawatt-second. Since the output of wind power and photovoltaic power is strongly random and volatile due to weather effects, their inertia also has certain fluctuations and changes.

[0046] The new energy power plant provides virtual inertia for overall evaluation in the unit of the entire power plant. First, calculate the actual output ratio of the new energy power plant, that is, the ratio of the actual output of the new energy power plant to the rated installed capacity, and see if it is greater than the set output threshold Q. In this implementation, the output threshold Q is set to 20%. That is, when the actual output ratio of the new energy power plant is lower than the output threshold Q, it is considered that the new energy power plant does not have inertia response ability, and at this time, the inertia calculation of this new energy power plant is not performed. If the actual output ratio of the new energy power plant is not lower than the output threshold Q, it is considered that the new energy power plant has inertia response ability and is used as the target new energy power plant in the inertia calculation of current new energy power plants in the power grid.

[0047] Since the inertia constant of the new energy power plant can be flexibly adjusted by setting the control parameters of the inverter, the inertia constant of each new energy power plant can also be directly obtained as a rated parameter. However, relevant adjustments are made during specific calculations. That is, after the actual output ratio of the new energy power plant is not lower than the output threshold Q, the inertia of each new energy power plant is obtained by multiplying its actual output by the inertia constant. And since the actual output of the new energy power plant will change continuously, this also means that under this calculation method, the inertia of the new energy power plant obtained will also change dynamically. Therefore, the entire calculation can also be performed recursively at the set time interval, such as every 5 minutes or every 15 minutes, to match the change in the actual output of the new energy power plant.

[0048] Exemplarily, when there is an energy storage power station in the power grid, the energy storage power station can be incorporated into the new energy power plant during inertia calculation. The virtual inertia that the energy storage power station can provide is similar to that of the new energy power plant, and the calculation method is the same. It is included in the calculation of the virtual inertia of the new energy power plant together. Since there are no specific threshold requirements for energy storage, its output can trip quickly according to requirements. Therefore, as long as it is connected to the power grid, its inertia support ability is considered.

[0049] In a possible implementation manner, obtaining the current inertia on the load side of the power grid includes: obtaining the current unit load inertia value of the power grid and multiplying it by the total load to obtain the current inertia on the load side of the power grid; wherein, the current unit load inertia value of the power grid is calculated based on the load model adopted in the current stability calculation of the power grid and combined with the latest disturbance.

[0050] Explanatorily, the inertia on the load side is usually used to describe the effect of the load on the frequency by the load static frequency characteristic. Specifically, when the system power imbalance causes the system frequency to change, the energy stored in the electromagnetic field and rotating mass of the system load (such as motor load) will change, preventing the system frequency from changing, which is called the load inertia effect, and is generally represented by the load frequency regulation effect coefficient. Since the load static frequency characteristic mainly comes from the motor load during the inertia response stage, directly describing this characteristic as the motor inertia response can better reflect the dynamic effect of the motor on the frequency. The directly grid-connected asynchronous motor can actively respond to the system frequency disturbance and provide inertia support to the system by releasing the kinetic energy stored on the rotor; other loads (other loads in the system except asynchronous motors) respond through their own characteristics and instantaneously change the magnitude of their own load power according to the system voltage or frequency change, playing a role similar to inertia support. The inertia on the load side is mainly obtained by multiplying the unit load inertia value under the load model calculated based on the load model adopted in the current stability calculation and combined with the latest disturbance by the total load of the power grid at the current moment to obtain the current inertia on the load side of the power grid. Similarly, the calculation of the inertia on the load side is also continuously calculated at a certain time interval. Exemplarily, if the unit load inertia value under the load model is 0.02 s, then in a power grid with a load of 1000 MW, the inertia on the load side is 20 MWS.

[0051] Finally, the current inertia of the synchronous machine type resources, the inertia of the new energy power plant, and the inertia on the load side of the power grid are summarized to obtain the current system inertia of the power grid. The calculation of the current system inertia of the power grid is carried out in a rolling manner at a certain time interval. The time intervals for calculating these three types of inertia, namely the inertia of the synchronous machine type resources, the inertia of the new energy power plant, and the inertia on the load side, can be different from each other or calculated according to a unified time interval. In actual engineering, it is recommended to perform synchronous calculation according to a unified time interval, such as updating once every 15 minutes, etc.

[0052] In a possible implementation, obtaining the system minimum inertia based on the minimum inertia constant of the power grid currently includes: obtaining the current minimum inertia constant and the total load of the power grid and multiplying them to obtain the current system minimum inertia of the power grid based on the minimum inertia constant.

[0053] For explanatory purposes, see Figure 3 , currently there are mainly two methods for evaluating the system minimum inertia of the power grid. One is based on the maximum frequency change rate. According to the maximum frequency change rate (df / dt) under the maximum power loss ΔP max to calculate the system minimum inertia H min : where f N is the power grid frequency. The other is based on the lowest frequency point, and the lowest frequency point for the safe and stable operation of the power grid is used as the calculation basis for the system minimum inertia. Usually, the minimum value of the calculation results of the two is used as the final system minimum inertia. In addition, in this implementation, the current system minimum inertia of the power grid based on the minimum inertia constant is also obtained, that is, according to the minimum inertia constant allowed for the entire power grid, it is multiplied by the current total load of the entire power grid to obtain the system minimum inertia. For example, if the minimum inertia constant allowed for the power grid is 4 s, then if the total load of the entire power grid is 1000 MW, then the system minimum inertia based on the minimum inertia constant at this time is 4000 MWS.

[0054] Finally, by selecting the minimum value among the three calculation results of the current system minimum inertia of the power grid based on the maximum frequency change rate, based on the lowest frequency point, and based on the minimum inertia constant, it is used as the system minimum inertia.

[0055] In a possible implementation, obtaining the current inertia demand of the power grid based on the preset inertia margin requirement and combining the current system inertia and the minimum system inertia of the power grid includes: when the inertia margin requirement is to meet the basic inertia demand of the system, the current inertia demand of the power grid is obtained in the following manner: when the current system inertia of the power grid is not less than the minimum system inertia, the current inertia demand of the power grid is 0; when the current inertia demand of the power grid is less than the minimum system inertia, the current inertia demand of the power grid is: (the current minimum system inertia of the power grid - the current system inertia of the power grid) × a preset coefficient K; where K is not less than 1; when the inertia margin requirement is that the inertia is abundant and not lower than the preset inertia abundance threshold M, the current inertia demand of the power grid is obtained in the following manner: when the current system inertia of the power grid is not less than the minimum system inertia, calculate the current inertia abundance R of the power grid. When R is not less than M, the current inertia demand of the power grid is 0; when R is less than M, the current inertia demand of the power grid is: (the current minimum system inertia of the power grid / (1 - M)) - the current system inertia of the power grid; when the current system inertia of the power grid is less than the minimum system inertia, the current inertia demand of the power grid is: (the current minimum system inertia of the power grid / (1 - M)) - the current system inertia of the power grid.

[0056] For explanatory purposes, see Figure 4 , compare the current system inertia and the minimum system inertia of the power grid. If the system inertia is greater than the minimum system inertia, it is considered that the power grid inertia meets the requirements of power grid safety and stability, and at the same time, evaluate the abundance of the power grid inertia. Subtract the minimum system inertia from the current system inertia of the power grid and then divide by the system inertia to obtain the inertia margin percentage R. If R is greater than the inertia abundance threshold M, it is considered that the power grid inertia is abundant; if R is less than M, it is considered that there is room for further improvement of the power grid inertia. Specifically, the calculated value obtained by dividing the minimum system inertia by (1 - M) and then subtracting the system inertia can be used to obtain the inertia value that needs to be further improved. Exemplarily, assuming M = 20%, if the minimum system inertia is 80 MWS and the system inertia is 90 MWS at this time, although the inertia level exceeds the minimum system inertia at this time, the inertia abundance is less than the inertia abundance threshold. Therefore, an additional 10 MWS of inertia is required to meet the requirement of inertia abundance.

[0057] If the system inertia is less than the minimum system inertia, it is considered that the grid inertia is significantly insufficient. Calculate the difference between the minimum system inertia and the system inertia to obtain the minimum required inertia value V1. Considering the random fluctuations of new energy output and the certain uncertainty of the load, the minimum required inertia value calculated at this moment may not meet the requirements in the next calculation interval. To ensure that the grid inertia can better meet the basic inertia requirements of the system, that is, the minimum inertia requirements, multiply the minimum required inertia value V1 by a preset coefficient K, and use the calculated value V2 as the most basic requirement value of inertia. Exemplarily, the preset coefficient K can be set to 1.1, etc., to ensure that it can meet the minimum inertia requirements for a long time in the future. Optionally, when abundant inertia is required, combine the inertia abundance threshold M, divide the system minimum inertia by (1 - M), subtract the system inertia from the calculated value obtained, and obtain the current inertia requirement of the grid under the requirement of abundant inertia.

[0058] The following is an apparatus embodiment of the present invention, which can be used to execute the method embodiment of the present invention. For details not disclosed in the apparatus embodiment, please refer to the method embodiment of the present invention.

[0059] See Figure 5 , in another embodiment of the present invention, an online evaluation system for grid inertia demand is provided, which can be used to implement the above-mentioned online evaluation method for grid inertia demand. Specifically, the online evaluation system for grid inertia demand includes a system inertia evaluation module, a system minimum inertia evaluation module, and an inertia demand evaluation module.

[0060] Among them, the system inertia evaluation module is used to obtain the synchronous machine type resource inertia, new energy plant station inertia, and load side inertia of the current grid and superimpose them to obtain the current system inertia of the grid; the system minimum inertia evaluation module is used to obtain the system minimum inertia based on the maximum frequency change rate, the lowest frequency point, and the minimum inertia constant of the current grid and take the minimum value to obtain the current system minimum inertia of the grid; the inertia demand evaluation module is used to obtain the current inertia demand of the grid based on the preset inertia margin demand, combined with the current system inertia and system minimum inertia of the grid.

[0061] In a possible implementation manner, obtaining the inertia of the current synchronous machine type resources of the power grid includes: obtaining the rated power and inertia constant of each operating synchronous generator set in the current power grid, multiplying them to obtain the inertia of each operating synchronous generator set in the current power grid, and adding them up to obtain the inertia of the synchronous generator sets in the current power grid; obtaining the rated power and inertia constant of each operating synchronous condenser in the current power grid, multiplying them to obtain the inertia of each operating synchronous condenser in the current power grid, and adding them up to obtain the inertia of the synchronous condensers in the current power grid; obtaining the rated power and inertia constant of each operating unit of each pumped-storage power station in the current power grid, multiplying them to obtain the inertia of each operating unit of each pumped-storage power station in the current power grid, and adding them up to obtain the inertia of the pumped-storage power stations in the current power grid; adding up the inertia of the synchronous generator sets, the inertia of the synchronous condensers, and the inertia of the pumped-storage power stations in the current power grid to obtain the inertia of the current synchronous machine type resources of the power grid.

[0062] In a possible implementation manner, obtaining the inertia of the current new energy power plants and substations of the power grid includes: obtaining the actual output and inertia constant of each target new energy power plant and substation in the current power grid, multiplying them to obtain the inertia of each target new energy power plant and substation in the current power grid, and adding them up to obtain the inertia of the current new energy power plants and substations of the power grid; wherein, the target new energy power plant and substation is a new energy power plant and substation whose ratio of actual output to rated installed capacity is greater than a preset output threshold value.

[0063] In a possible implementation manner, obtaining the inertia of the current load side of the power grid includes: obtaining the unit load inertia value and the total load in the current power grid, multiplying them to obtain the inertia of the current load side of the power grid; wherein, the unit load inertia value in the current power grid is calculated based on the load model used in the current power grid stability calculation and combined with the latest disturbance calculation.

[0064] In a possible implementation manner, obtaining the minimum inertia of the system based on the minimum inertia constant of the current power grid includes: obtaining the minimum inertia constant and the total load in the current power grid, multiplying them to obtain the minimum inertia of the system based on the minimum inertia constant of the current power grid.

[0065] In a possible implementation manner, obtaining the current inertia demand of the power grid by combining the preset inertia margin requirement with the current system inertia and the minimum system inertia of the power grid includes: when the inertia margin requirement is to meet the basic inertia demand of the system, the current inertia demand of the power grid is obtained in the following manner: when the current system inertia of the power grid is not less than the minimum system inertia, the current inertia demand of the power grid is 0; when the current inertia demand of the power grid is less than the minimum system inertia, the current inertia demand of the power grid is: (the current minimum system inertia of the power grid - the current system inertia of the power grid) × a preset coefficient K; where K is not less than 1; when the inertia margin requirement is that the inertia is abundant and not lower than a preset inertia abundance threshold M, the current inertia demand of the power grid is obtained in the following manner: when the current system inertia of the power grid is not less than the minimum system inertia, calculate the current inertia abundance R of the power grid. When R is not less than M, the current inertia demand of the power grid is 0; when R is less than M, the current inertia demand of the power grid is: (the current minimum system inertia of the power grid / (1 - M)) - the current system inertia of the power grid; when the current system inertia of the power grid is less than the minimum system inertia, the current inertia demand of the power grid is: (the current minimum system inertia of the power grid / (1 - M)) - the current system inertia of the power grid.

[0066] All relevant contents of each step involved in the embodiment of the foregoing online evaluation method for power grid inertia demand can be cited in the function description of the corresponding functional module of the online evaluation device for power grid inertia demand in the embodiment of the present invention, and will not be elaborated here.

[0067] The division of modules in the embodiments of the present invention is illustrative, and is only a logical function division. In actual implementation, there may be other division methods. In addition, in each embodiment of the present invention, each functional module can be integrated in a processor, or can exist separately physically, or two or more modules can be integrated in one module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules.

[0068] In another embodiment of the present invention, a computer device is provided. The computer device includes a processor and a memory. The memory is used to store a computer program, and the computer program includes program instructions. The processor is used to execute the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function. The processor described in the embodiment of the present invention can be used for the operation of the online evaluation method of grid inertia demand.

[0069] In another embodiment of the present invention, a storage medium is also provided, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in the computer device and is used to store programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and, of course, the extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, and the operating system of the terminal is stored in this storage space. And in this storage space, one or more instructions suitable for being loaded and executed by the processor are also stored. These instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. One or more instructions stored in the computer-readable storage medium can be loaded and executed by the processor to implement the corresponding steps of the online evaluation method of grid inertia demand in the above embodiments.

[0070] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0071] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0072] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0073] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific embodiments of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered by the protection scope of the claims of the present invention.

Claims

1. A method for online evaluation of power grid inertia demand, characterized in that: include: Obtain the current inertia of the synchronous machine type resources, the inertia of the new energy plant and the load side inertia of the power grid and add them together to obtain the current system inertia of the power grid; Obtain the current minimum system inertia of the power grid based on the maximum frequency change rate, the lowest frequency point and the minimum inertia constant and take the minimum value to obtain the current minimum system inertia of the power grid; Based on the preset inertia margin requirement, combined with the current system inertia and the minimum system inertia of the power grid, the current inertia requirement of the power grid is obtained.

2. The online evaluation method for power grid inertia demand according to claim 1, characterized in that: The method of obtaining the current synchronous machine type resource inertia of the power grid includes: The rated power and inertia constant of each synchronous unit currently in operation of the power grid are obtained and multiplied to obtain the inertia of each synchronous unit currently in operation of the power grid and added to obtain the current inertia of the synchronous unit of the power grid; The rated power and inertia constant of each synchronous condenser currently in operation in the power grid are obtained and multiplied to obtain the inertia of each synchronous condenser currently in operation in the power grid and added to obtain the current inertia of the synchronous condenser in the power grid; The rated power and inertia constant of each operating unit of each pumped-storage power station in the power grid are obtained and multiplied to obtain the inertia of each operating unit of each pumped-storage power station in the power grid and added to obtain the inertia of the current pumped-storage power station in the power grid; The current inertia of the synchronous units, synchronous condenser and pumped storage power station inertia of the power grid is added to obtain the current inertia of the synchronous machine type resources in the power grid.

3. The online evaluation method for power grid inertia demand according to claim 1, characterized in that: Obtaining the current inertia of the new energy plant in the power grid includes: The actual output and inertia constant of each target new energy plant in the power grid are obtained and multiplied to obtain the inertia of each target new energy plant in the power grid and superimposed to obtain the current inertia of the new energy plant in the power grid; Among them, the target new energy plant is a new energy plant whose ratio of actual output to rated installed capacity is greater than a preset output threshold.

4. The online evaluation method for power grid inertia demand according to claim 1, characterized in that: Obtaining the current load side inertia of the power grid includes: The current unit load inertia value of the power grid and the total load are obtained and multiplied to obtain the current load side inertia of the power grid; wherein the current unit load inertia value of the power grid is calculated based on the load model used in the current stability calculation of the power grid and combined with the latest disturbance.

5. The online evaluation method for power grid inertia demand according to claim 1, characterized in that: Obtaining the current minimum inertia of the power grid based on the minimum inertia constant of the system includes: The current minimum inertia constant of the power grid and the total load are obtained and multiplied to obtain the current minimum system inertia of the power grid based on the minimum inertia constant.

6. The online evaluation method for power grid inertia demand according to claim 1, characterized in that: The current inertia requirement of the power grid is obtained based on the preset inertia margin requirement and combined with the current system inertia and the minimum system inertia of the power grid, including: When the inertia margin requirement is to meet the basic inertia requirement of the system, the current inertia requirement of the power grid is obtained in the following way: when the current system inertia of the power grid is not less than the minimum system inertia, the current inertia requirement of the power grid is 0; when the current inertia requirement of the power grid is less than the minimum system inertia, the current inertia requirement of the power grid is: (the current minimum system inertia of the power grid - the current system inertia of the power grid) × preset coefficient K; wherein K is not less than 1; When the inertia margin requirement is that the inertia margin is not less than the preset inertia margin threshold M, the current inertia requirement of the power grid is obtained in the following way: when the current system inertia of the power grid is not less than the minimum system inertia, the current inertia margin R of the power grid is calculated. When R is not less than M, the current inertia requirement of the power grid is 0; when R is less than M, the current inertia requirement of the power grid is: (the current minimum system inertia of the power grid / (1-M))-the current system inertia of the power grid; when the current system inertia of the power grid is less than the minimum system inertia, the current inertia requirement of the power grid is: (the current minimum system inertia of the power grid / (1-M))-the current system inertia of the power grid.

7. A device for online evaluation of power grid inertia demand, characterized in that: include: The system inertia evaluation module is used to obtain the current inertia of the synchronous machine type resources, the inertia of the new energy plant and the load side of the power grid and add them together to obtain the current system inertia of the power grid; The system minimum inertia evaluation module is used to obtain the current system minimum inertia of the power grid based on the maximum frequency change rate, the lowest frequency point and the minimum inertia constant and take the minimum value to obtain the current system minimum inertia of the power grid; The inertia requirement evaluation module is used to obtain the current inertia requirement of the power grid based on the preset inertia margin requirement and the current system inertia and the minimum system inertia of the power grid.

8. The online evaluation device for power grid inertia demand according to claim 7, characterized in that: The method of obtaining the current synchronous machine type resource inertia of the power grid includes: The rated power and inertia constant of each synchronous unit currently in operation of the power grid are obtained and multiplied to obtain the inertia of each synchronous unit currently in operation of the power grid and added to obtain the current inertia of the synchronous unit of the power grid; The rated power and inertia constant of each synchronous condenser currently in operation in the power grid are obtained and multiplied to obtain the inertia of each synchronous condenser currently in operation in the power grid and added to obtain the current inertia of the synchronous condenser in the power grid; The rated power and inertia constant of each operating unit of each pumped-storage power station in the power grid are obtained and multiplied to obtain the inertia of each operating unit of each pumped-storage power station in the power grid and added to obtain the inertia of the current pumped-storage power station in the power grid; The current inertia of the synchronous units, synchronous condenser and pumped storage power station inertia of the power grid is added to obtain the current inertia of the synchronous machine type resources in the power grid.

9. The online evaluation device for power grid inertia demand according to claim 7, characterized in that: Obtaining the current inertia of the new energy plant in the power grid includes: The actual output and inertia constant of each target new energy plant in the power grid are obtained and multiplied to obtain the inertia of each target new energy plant in the power grid and added to obtain the current inertia of the new energy plant in the power grid; Among them, the target new energy plant is a new energy plant whose ratio of actual output to rated installed capacity is greater than a preset output threshold.

10. The online evaluation device for power grid inertia demand according to claim 7, characterized in that: Obtaining the current load side inertia of the power grid includes: The current unit load inertia value of the power grid and the total load are obtained and multiplied to obtain the current load side inertia of the power grid; wherein the current unit load inertia value of the power grid is calculated based on the load model used in the current stability calculation of the power grid and combined with the latest disturbance.

11. The online evaluation device for power grid inertia demand according to claim 7, characterized in that: Obtaining the current minimum inertia of the power grid based on the minimum inertia constant of the system includes: The current minimum inertia constant of the power grid and the total load are obtained and multiplied to obtain the current minimum system inertia of the power grid based on the minimum inertia constant.

12. The online evaluation device for power grid inertia demand according to claim 7, characterized in that: The current inertia requirement of the power grid is obtained based on the preset inertia margin requirement and combined with the current system inertia and the minimum system inertia of the power grid, including: When the inertia margin requirement is to meet the basic inertia requirement of the system, the current inertia requirement of the power grid is obtained in the following way: when the current system inertia of the power grid is not less than the minimum system inertia, the current inertia requirement of the power grid is 0; when the current inertia requirement of the power grid is less than the minimum system inertia, the current inertia requirement of the power grid is: (the current minimum system inertia of the power grid - the current system inertia of the power grid) × preset coefficient K; wherein K is not less than 1; When the inertia margin requirement is that the inertia margin is not less than the preset inertia margin threshold M, the current inertia requirement of the power grid is obtained in the following way: when the current system inertia of the power grid is not less than the minimum system inertia, the current inertia margin R of the power grid is calculated. When R is not less than M, the current inertia requirement of the power grid is 0; when R is less than M, the current inertia requirement of the power grid is: (the current minimum system inertia of the power grid / (1-M))-the current system inertia of the power grid; when the current system inertia of the power grid is less than the minimum system inertia, the current inertia requirement of the power grid is: (the current minimum system inertia of the power grid / (1-M))-the current system inertia of the power grid.

13. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method for online evaluation of power grid inertia demand according to any one of claims 1 to 6 are implemented.

14. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method for online evaluation of power grid inertia demand according to any one of claims 1 to 6 are implemented.

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