CN115811058A - Emergency frequency control method for electric power system with metallurgical load participating in safety auxiliary service - Google Patents
Emergency frequency control method for electric power system with metallurgical load participating in safety auxiliary service Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/30—Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
- Y02B70/3225—Demand response systems, e.g. load shedding, peak shaving
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
- Y04S20/20—End-user application control systems
- Y04S20/222—Demand response systems, e.g. load shedding, peak shaving
Abstract
The invention relates to the field of safe and stable operation of a power system, in particular to a power system emergency frequency control method for metallurgical load participation safety auxiliary service, which comprises the steps of obtaining an active shortage initial value of a target power grid, monitoring a real-time metallurgical industrial load state, estimating the metallurgical load quantity required to be called, and carrying out demand response compensation pricing through a master-slave game model; based on the rotational inertia and the frequency change condition of the power grid, setting the low-frequency load shedding action cycle, action time and load shedding amount; based on the preset load shedding action and the real-time running state of the metallurgical load, the load is cut by adopting a mode of calling the metallurgical load firstly and calling the common load secondly; carrying out economic compensation on the user based on power grid compensation pricing and the final actual load shedding condition of the user; the invention can quickly restrain the frequency from decreasing by using the large-scale centralized metallurgical load to participate in the emergency frequency control, and can effectively reduce the cutting amount of the common load and the economic loss of important users by fully calling the load side resource.
Description
Technical Field
The invention relates to the field of safe and stable operation of an electric power system, in particular to an emergency frequency control method of an electric power system for metallurgical load to participate in safe auxiliary service.
Background
Wind power and photovoltaic power generation become the growth main body of newly increased electric quantity in the future, and the proportion of installed capacity of various clean energy sources in a power grid also continuously rises. However, the new energy unit also has the problems of large fluctuation, strong randomness, low controllability and the like. Meanwhile, the reverse distribution of power resources and load centers in China needs to realize long-distance trans-regional power transmission through an ultra-high voltage alternating current-direct current line, so that a plurality of transmitting and receiving end systems are formed. Under the condition of large disturbance, the frequency change trends of a sending end and a receiving end are opposite, and after different types of units and loads are cut down by different rotary inertia, the frequency dynamic response of the sending end and the receiving end is different, so that certain difficulty is increased for stable operation and power reliability supply of a power system, and the method is mainly shown in the following steps: the method has the advantages of increasing the difficulty of power grid adjustment, complex interaction of multiple power electronic devices, reducing the anti-interference capability of the system, changing the frequency characteristic of the power grid and the like.
In order to deal with an emergency situation where the overall frequency of the power system is rapidly decreased or greatly fluctuated due to a serious disruption of the active power balance of the power system, a common frequency abnormality control device starts from both load control and power supply control, and when the frequency is increased, a power supply control device such as a high-frequency-switching power generator device or a high-frequency-switching power generation device is mainly considered. When the frequency is reduced, a device for controlling the load is provided, such as a low-frequency load reduction device, a low-frequency voltage reduction device and the like; and devices for controlling power sources, such as low-frequency self-starting generator devices, low-frequency water pumping and power generating devices, and the like. Aiming at load side optimization control, the existing scheme carries out coordination optimization from the aspects of low-frequency load shedding action turns, action time, load shedding index distribution and the like, and guarantees are provided for rapidity, flexibility and reliability of load shedding.
With the increasing of resources that can be adjusted at the load side and the increasing maturity of research on the control modes and means of the resources at the load side, it is necessary to fully utilize various controllable resources in the whole network to reduce the risk of system stability damage.
Chinese patent publication No. CN114123238a discloses a kalman control method for electrolytic aluminum load participating in power system frequency modulation, which obtains system frequency deviation by analyzing specific operating characteristics and frequency response model of the electrolytic aluminum load and using kalman filtering processing, and finally uses a fuzzy controller to control power consumption of the electrolytic aluminum and improve the frequency control performance of the power system. Chinese patent publication No. CN112564128a discloses a "control system and method for electrolytic aluminum load participating in power grid frequency modulation", which controls electrolytic aluminum load output to participate in power grid frequency modulation according to power grid frequency change, frequency change rate and the stage of frequency change. Chinese patent publication No. CN113141015a discloses a method for controlling electrolytic aluminum load to participate in frequency modulation of a transmission-end power grid, which includes estimating the amount of electrolytic aluminum to be adjusted quickly in real time, and adding electrolytic aluminum to stability control measures under different frequency offsets to prevent frequency offset after failure.
Chinese patent publication No. CN112993987a discloses a method for controlling an electrolytic aluminum load coordinated power grid with active adjustable capacity coordination, which calculates the system power shortage by monitoring the frequency change on line, and calculates the maximum upward primary frequency modulation power that can be provided by a thermal power generating unit at the present time, so as to obtain the target total adjustment amount of the electrolytic aluminum load participating in the power grid frequency adjustment and the sub-adjustment amounts that each electrolytic aluminum load needs to bear. The above patent utilizes typical metallurgical load-electrolytic aluminum load to participate in power grid control, and controls electrolytic aluminum load output to improve power system frequency stability through research on a specific control method of the electrolytic aluminum load and evaluation on the adjustable quantity of the electrolytic aluminum load. But they are limited to a specific metallurgical load and by default the current operating load can be adjusted to neglect the effect of the grid compensation mechanism on the actual load response rate, and the situation that the actual adjustable load amount is far less than the system power shortage can occur.
The method for controlling the emergency frequency of the power system by utilizing the metallurgical load to participate in the safety auxiliary service is provided from a macroscopic level, and the defect that the original load is unidirectionally and passively adjusted by the power grid is changed. Therefore, how to bring the metallurgical load into a low-frequency load shedding optimization scheme and set a reasonable metallurgical load compensation scheme is a problem to be solved urgently, so that the power system is helped to recover the frequency stability quickly and the influence on the important load is reduced.
Disclosure of Invention
In order to utilize the reducible potential of the metallurgical load to participate in the emergency frequency control of the power grid and make a reasonable compensation strategy to fully call the large-scale metallurgical industrial load to participate in the demand response so as to ensure that the power grid can realize the continuous power supply to the important load on the basis of stable frequency and reduce the breakdown probability and the economic loss of the power grid, the invention provides a power system emergency frequency control method for the metallurgical load to participate in the safety auxiliary service, which specifically comprises the following steps:
s1: acquiring an active power shortage initial value of a target power grid, and monitoring a real-time metallurgical industry load state;
s2: estimating the metallurgical load quantity to be called based on the initial value of the active power shortage and the metallurgical load state;
s3: based on the expected calling of the metallurgical load of the power grid, carrying out demand response compensation pricing through a master-slave game model;
s4: based on the rotational inertia and the frequency change condition of the power grid, setting the low-frequency load shedding action cycle, action time and load shedding amount;
s5: based on the preset load shedding action and the real-time running state of the metallurgical load, the load is cut by adopting a mode of calling the metallurgical load firstly and calling the common load secondly;
s6: and carrying out economic compensation on the user based on the power grid compensation pricing and the final actual load shedding condition of the user.
Further, calculating an active shortage initial value of the target power grid specifically includes:
wherein, Δ P 0 Representing the initial active shortage of the system;
representing the rate of change of the system frequency f with time t; t is sys Representing the equivalent inertia time constant of the system; e sys Representing the total kinetic energy of the system; t is Gi Represents the inertia constant of the synchronous generator i; s Gi Represents the rated capacity of the synchronous generator i; x is a radical of a fluorine atom Gi Indicating the start-stop state of the synchronous unit when x Gi If =1, it means that the synchronous unit is operating, and when x Gi If =0, the synchronous unit is stopped; n represents the number of synchronous generators within the target grid; t is Nj Representing the inertia constant of the new energy source unit j; s Nj Representing the rated capacity of the new energy machine set j; x is the number of Nj Showing the starting and stopping states of the new energy source set when x Nj When the number is not less than 1, the new energy unit is operated, and when the number is x Nj If =0, the new energy machine set is shut down; m represents the number of new energy banks containing inertia in the target power grid.
Further, estimating the metallurgical load quantity to be called based on the initial value of the active power shortage and the metallurgical load state, namely when the adjustable quantity of the metallurgical load is larger than the power shortage of the system, the metallurgical load quantity reduced by the power grid is the total load shedding quantity of low-frequency load shedding; and when the adjustable amount of the metallurgical load is smaller than the power shortage of the system, the expected adjustable amount of the metallurgical load of the power grid is the total reducible power in the current running state.
Furthermore, based on the expected calling of the metallurgical load of the power grid, when demand response compensation pricing is carried out through a master-slave game model, a target function is constructed on the power grid side by taking the total demand response income of the maximized power grid side as a target, and an expression of unit compensation price issued by the power grid is obtained; constructing an objective function by taking the maximized user side response income as the objective function at the user side, substituting the objective function into a unit compensation price expression issued by the power grid and obtained by solving at the power grid side, and solving to obtain the response power delta P of each metallurgical user i The expression (c) of (a),the user response power expression is substituted into a target function at the power grid side, and a value of a unit compensation price issued by the power grid is obtained by solving under the condition that constraint conditions are met; and substituting the value of the unit compensation price issued by the power grid into a user side demand response function to obtain the final value of each user response power.
Further, the constructing of the objective function by the power grid side with the goal of maximizing the total demand response income of the power grid side includes:
wherein i = {1,2, …, N }, N represents the number of users affected by grid frequency instability; j = {1,2, …, M }, where M represents the number of users participating in demand response; lambda [ alpha ] i The economic loss brought by the i unit electric quantity of the compensation user is represented; delta P i Indicates that user i is at t i Power over which the period is affected; a is 2 Representing the unit compensation price issued by the power grid; p j Indicating the curtailed power of the jth user in the demand response; t is t j Representing load shedding time when the user j participates in demand response; a. The 1 Representing that the loss cost caused to the important load can be avoided; p total The total power of the metallurgical load which can participate in the demand response in real time is expected for the power grid side.
Further, the user side constructs an objective function by taking the maximized user side response income as the objective function, and the objective function of the user j for maximizing the response income thereof includes:
wherein, a 2 Representing the unit compensation price issued by the power grid; delta P j Indicates that user j is at t j Power over which the period is affected; c. C 1 Represents the production yield directly influenced by the average unit reduction power; c. C 2 The production value loss caused by the production state change corresponding to the average unit power is expressed; delta P j_state Indicating load work of varying operating power in the remaining load after load sheddingRate; t is t j_state Indicating the time when the operating power is changed after the load is reduced; delta P j_max Maximum load response capability for user j.
Further, the step of setting the low-frequency load shedding action cycle, the action time and the load shedding amount based on the moment of inertia and the frequency change condition of the power grid comprises the following steps:
determining the maximum power shortage, a frequency recovery target value, a low-frequency load shedding first wheel action frequency and a low-frequency load shedding last wheel action frequency of the system;
setting the load cutting capacity of each basic wheel according to an average principle, and setting a shorter time delay;
a plurality of special wheels are arranged for load shedding, namely the load cutting amount of each wheel of the special wheels is smaller than the load cutting amount of each wheel of the basic wheel; wherein the load per round of cutting of the basic round is as follows:
wherein, Δ P k Representing the k-th round cutting load; delta P max Representing the maximum power shortage of the system; k L Representing a load frequency adjustment coefficient; f. of 0 Represents the steady state frequency; f. of N Indicating the last wheel action frequency.
Further, when the occupation ratio of the new energy source unit is larger than a set threshold, the first wheel load shedding amount is improved, the basic wheel time delay is shortened, and the increased load shedding amount is evenly distributed to the first three wheels of the low-frequency load shedding according to the low-frequency protection fixed value of the new energy source unit.
Further, based on the preset load shedding action and the real-time running state of the metallurgical load, the load shedding method adopting the mode of firstly calling the metallurgical load and secondly calling the common load comprises the following steps:
the method comprises the following steps of (1) prioritizing various loads, wherein the metallurgical load has the highest priority, and the other common loads calculate load priority assessment scores according to indexes of various branches, wherein the indexes at least comprise load user grades, sensitivity, power supply continuity requirements and power failure loss, and the higher the score is, the higher the priority is; the load priority evaluation score of the intelligent power distribution terminal on the ith branch is expressed as:
M i ＝∑W j S j ；
wherein M is i Evaluating scores for the load priority of the intelligent power distribution terminal in the ith branch; w j The weight proportion of the jth index of the branch is taken; s j The final evaluation score of the jth index of the branch;
when the power shortage and the frequency dip of the power system occur, the control center sends load reduction instructions to various loads according to the priority division sequence to determine various load reduction amounts.
According to the method, the reducible load quantity of the different metallurgical loads participating in the emergency frequency control of the power grid is calculated by analyzing the operating characteristics of the different metallurgical loads, then the different loads are given priority, and the priority is counted into the low-frequency load reduction strategy of the power grid according to the priority sequence, so that the power grid can timely save the power grid frequency collapse condition when the new energy fan output fluctuation occurs or the generator quits the operation due to reasons, and the loss of important loads is reduced; meanwhile, through game analysis of the power grid and the user demand response income, the compensation price can be formulated in a marketization mode, and the defect that the existing scheme adopts fixed price compensation is overcome.
Drawings
FIG. 1 is a logic block diagram of a method for controlling emergency frequency of a metallurgical load participating in a power grid;
FIG. 2 is a schematic diagram of a series of DC power supply for electrolytic aluminum;
FIG. 3 is a flow chart of a steelmaking process;
FIG. 4 is a schematic diagram showing the relationship between the steel-making load reduction time and the maximum reduction power.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides an emergency frequency control method for an electric power system with metallurgical load participating in safety auxiliary service, which specifically comprises the following steps as shown in figure 1:
s1: acquiring an active power shortage initial value of a target power grid, and monitoring a real-time metallurgical industrial load state;
s2: estimating the metallurgical load quantity to be called based on the initial value of the active power shortage and the metallurgical load state;
s3: based on the expected calling of the metallurgical load of the power grid, carrying out demand response compensation pricing through a master-slave game model;
s4: based on the rotational inertia and the frequency change condition of the power grid, setting the low-frequency load shedding action cycle, action time and load shedding amount;
s5: based on the preset load shedding action and the real-time running state of the metallurgical load, the load is cut by adopting a mode of calling the metallurgical load firstly and calling the common load secondly;
s6: and carrying out economic compensation on the user based on the power grid compensation pricing and the final actual load shedding condition of the user.
In this embodiment, the calculation formula of the initial active power shortage of the target grid is as follows:
in the formula: delta P 0 Representing the initial active shortage of the system;
representing the rate of change of the system frequency; t is sys Representing the equivalent inertia time constant of the system; e sys Represents the total kinetic energy of the system; t is Gi Represents the inertia constant of the synchronous generator i; s Gi Represents the rated capacity of the synchronous generator i; x is the number of Gi Indicating the start-stop state of the synchronous unit when x Gi If =1, it means that the synchronous unit is operating, and when x Gi If =0, the synchronous unit is stopped; n represents the number of synchronous generators within the target grid; t is Nj Representing the inertia constant of the new energy source unit j; s. the Nj Representing the rated capacity of the new energy machine set j; x is the number of Nj Showing the start-stop state of the new energy source unit when x is Nj Denotes that the new energy unit is operated when the number is 1, and x Nj If =0, the new energy machine set is shut down; m represents the number of new energy banks containing inertia in the target power grid.
Preferably, when the real-time metallurgical industrial load state is monitored, the target power grid metallurgical load operation state comprises the current total operation power of the load and the relevant parameters of the current production process. Taking an electrolytic aluminum load and a steelmaking load as examples, load information required to be acquired by the electrolytic aluminum load comprises the total operating power of the current electrolytic aluminum, the ton aluminum power consumption, the reduction power percentage and the influence degree of the power reduction time on the production of the electrolytic aluminum; the load information required to be acquired by the steelmaking load comprises the current running total power of the steelmaking load, the smelting period of each steelmaking device, the minimum temperature requirement, the production speed and the inventory capacity.
In the specific implementation process, the total load shedding amount of the low-frequency load shedding can be determined based on the initial value of the active power shortage of the power grid, and when the metallurgical load is large enough, the metallurgical load shedding amount of the power grid is the total load shedding amount of the low-frequency load shedding; and when the metallurgical load is insufficient, the power grid expects to call the metallurgical load amount to be the total reducible power in the current operation state. According to the current running state and the reduction time of the metallurgical load, actual reduction load amount is distributed according to various metallurgical load characteristics in a metallurgical industry user.
The calculation formula of the low-frequency load shedding total load shedding amount is as follows:
P shed ＝1.05*(ΔP 0 -P thr )；
in the formula: p shed The total load shedding amount of the system during low-frequency load shedding; p thr Is the maximum amount of imbalance allowed by the system in the normal range of frequencies.
Taking an electrolytic aluminum load and a steelmaking load as examples, as shown in fig. 2, the electrolytic aluminum load is supplied with direct current by using a rectifying device, is a constant current load during normal operation, can be regarded as a constant power load from a power grid side, and has small load fluctuation and little influence by voltage and frequency in the production process. The common rectifying devices mainly comprise thyristor rectification and diode rectification, and compared with a diode, the thyristor rectification has the advantages of high regulation speed (the response time can reach millisecond level) and continuous regulation. The electrolytic aluminum load rectified by the diode can only be reduced by cutting off the rectifier unit due to the slow response speed of adjustment. Meanwhile, the high-temperature environment required by the electrolytic cell has certain thermal inertia, and can bring about 10% -30% of load regulation capacity to the electrolytic cell. Therefore, the part of electrolytic aluminum load can be used for participating in the emergency load control of the power system, and the normal production of an electrolytic aluminum plant can not be greatly influenced within a certain power regulation range and calling time.
The electrolytic aluminum load has three different states of continuous aluminum production state, electrolytic bath heat preservation state and electrolytic bath cooling state according to different reduction powers. Since the long cooling time of the electrolytic aluminum can have a serious influence on the electrolyte and the electrolytic cell, the electrolytic cell should be kept at least in a heat-retaining state after the load of the electrolytic aluminum is reduced in the emergency frequency control. When the electrolytic aluminum series load is diode rectification, a general electrolytic aluminum plant Programmable Logic Controller (PLC) has two modes of main regulation and sub-regulation under the current stabilization control, the sub-regulation completes small closed-loop control, and the current stability of a small-size control unit of a rectifier cabinet body is acquired; the total regulation completes large closed-loop control, and technological conditions and anode working conditions of all rectifier units are integrated to control the stability of series current. If a part of power of the series is cut off, the total regulating current set value needs to be reduced while a part of the rectifier units needs to be cut off. After n rectifier units are cut off, the current of the rest units is not greater than the initial total regulation current setting; meanwhile, in order to ensure that the electrolytic cell does not enter a cooling state, the current of the rest units is not less than the insulation current of the electrolytic cell, and the calculation formula for reducing the load capacity is as follows:
in the formula: delta P is the total load reduction; p rate Rated power for electrolytic aluminum load; n' is the number of all the rectifier units in initial operation; n' is the number of the rectifier units cut off after receiving the load shedding instruction; i is 1 The current of a single residual unit after cutting off; i is 0 Is a single rectifierThe set initial current is the rated current of a single rectifier unit under the normal condition; rho is the heat preservation current coefficient.
As shown in fig. 3, the steel-making process includes making steel in a primary furnace (an electric arc furnace, an open hearth furnace, or a converter), transporting molten steel to a ladle refining furnace through a ladle to heat up or preserve the molten steel, so as to be beneficial to alloy supplement, component adjustment and subsequent continuous casting temperature requirements, simultaneously injecting argon into a gas permeable brick at the bottom of the ladle refining furnace to stir the molten steel, performing vacuum degassing on the molten steel through a steam jet pump, and finally sending the molten steel obtained in the refining stage to a continuous casting machine through the ladle to cast so as to obtain slabs in different shapes. Therefore, when the ladle refining furnace participates in load reduction, the condition that the molten steel in the upstream stock does not overflow, the downstream stock is sufficient and the lowest temperature meets the continuous casting requirement is met. The steel-making load can be mainly reduced to load of the ladle refining furnace, the power consumption is extremely high, the production rhythm is flexible, and the on-load tap-changer can be flexibly adjusted according to requirements on the premise of meeting the normal production and the lowest temperature of an upstream primary refining furnace and a downstream continuous casting machine, so that the purpose of reducing power is achieved.
Wherein, the load reduction calculation formula is as follows:
in the formula: delta P is the total load reduction; p is 0 Is the initial power; p 1 To reduce the load power of the ladle refining furnace; v. of 0 To reduce the speed of molten steel production of the ladle refining furnace before load; v. of 1 To reduce the speed of molten steel production of the ladle refining furnace before load; v. of Furnace with a heat exchanger The rate of production of molten steel for the primary refining furnace; eta is the amount of refined molten steel which can be smelted by molten steel of a primary refining furnace production unit at the upstream of the ladle refining furnace; t is the load reduction time; i is store1 In order to reduce the initial molten steel stock of the ladle in the middle process from the primary refining furnace to the ladle refining furnace; i is store1_max The maximum molten steel stock of the ladle in the middle process from the primary smelting furnace to the ladle refining furnace; v. of Casting of metals The speed of producing a slab for a continuous caster downstream of a ladle refining furnace; lambda is producible per ton of refined molten steelMeasuring the slab quantity; i is store2 In order to reduce the initial refining molten steel stock of a ladle in the middle process from a front ladle refining furnace to a continuous casting machine; t is 0 Is the initial molten steel temperature; v. of t The temperature reduction rate of molten steel produced by the primary smelting furnace in the current environment is shown; t is min Is the lowest temperature allowed for production by the ladle refining furnace equipment.
As shown in FIG. 4, when the load reduction time is short under a certain process parameter and a molten steel inventory, the influence on the upstream and downstream is small, and the maximum load reduction amount can reach the whole operation load of the ladle refining furnace. When the load reduction time is increased, the maximum reducible load is gradually reduced, the maximum load reduction time is limited by the lowest temperature of the ladle refining furnace, and the reduction time range is different from 10min to 40min according to the difference of the initial temperature of molten steel of the primary refining furnace. At the same reduction time, the maximum reducible load amount gradually increases as the initial primary refining furnace molten steel inventory decreases and the initial refined molten steel inventory increases.
When the master-slave game model is used for carrying out demand response compensation pricing on the metallurgical loads participating in reduction, a game model of a power grid and users is established with the aim of pursuing social welfare maximization, and the compensation electricity price under emergency is obtained through the model. In the embodiment, the aim of maximizing the social welfare is to optimize the profits of the user side and the power grid side, that is, the sum of the profits of the two sides is the maximum.
The real-time demand response income at the power grid side is mainly considered to avoid the cost of loss to important users and the demand response compensation cost; the user-side real-time demand response profit mainly considers demand response compensation profit and the response cost of load reduction.
Therefore, the total profit expression of the grid-side demand response of the present embodiment is as follows:
in the formula: a represents the total yield of the demand response of the power grid side; a. The 1 Representing that the loss cost caused to the important load can be avoided; a. The 2 Representing a demand response compensation cost; i (i =1,2, …, N) denotes a power receiving gridUsers affected by frequency instability; delta P i Indicates that user i is at t i Power over which the period is affected; λ i represents the economic loss brought by the user i unit electricity quantity of compensation; a is 2 Representing the unit compensation price issued by the power grid; j (j =1,2, …, M) represents a user participating in demand response; p j Indicating the curtailed power of the jth user in the demand response; t is t j Representing the load reduction time when the user j participates in the demand response; n represents the number of users affected by grid frequency instability; m represents the number of users participating in the demand response.
Large-scale industrial users generally execute strict production plans, and have corresponding limitations on internal power reduction of enterprises for maintaining equipment power safety and normal production environment. The user determines participation situation and participation load according to the subsidy price issued by the power grid and self situation, but the formulation of the subsidy unit price of the power grid is influenced in turn. The user-side demand response revenue expression is as follows:
in the formula: b represents the total profit of the user side demand response; b is 1,j Representing that the user obtains the benefit of subsidy of demand response; b is 2,j A response cost representing a user load reduction; delta P j Representing that the user j participates in the load reduction amount in the demand response; t is t j Representing the load reduction time when the user j participates in the demand response; c. C 1 Represents the production yield directly influenced by the average unit reduction power; c. C 2 The production value loss caused by the production state change corresponding to the average unit power is expressed; delta P j_state Load power representing a change in operating power in the remaining load after load shedding; t is t j_state Indicating the time at which the operating power changes after load shedding.
In order to seek the optimal subsidy price and ensure abundant load capacity for participating in demand response, a power grid company solves the optimization problem as follows:
in the formula: p total The total power of the metallurgical load which can participate in the demand response in real time is expected for the power grid side.
The user determines the optimal response electric quantity to maximize the self demand response income based on the demand response subsidy price and the self condition published by the power grid company. User j solves the optimization problem as follows:
in the formula: delta P j_max Maximum load response capability for user j.
And (4) setting the low-frequency load shedding action round, action time and load shedding amount based on the rotational inertia and the frequency change condition of the power grid. According to basic regulations of automatic low-frequency load reduction technical regulations of an electric power system, when wind power access is not considered, a low-frequency load reduction scheme is designed by adopting a conventional method, and the method comprises the following steps of:
firstly, determining the maximum power shortage of a system, a frequency recovery target value, and low-frequency first-wheel and last-wheel action frequencies of load shedding; as a preferred implementation, in this embodiment, the maximum power shortage of the system is determined, the steady-state system is restored to a level not lower than 49.5Hz, the low-frequency deloading first-wheel action frequency is set to 49Hz, the last-wheel action frequency is set to 48.02Hz, and 7 basic wheels are arranged;
then, the load cutting amount of each basic wheel is set according to the average principle, and the time delay is 0.3s;
finally, 3-4 special wheel unloading is set to prevent the frequency from suspending below 49.0Hz, the load of each wheel cutting is 1% -3%, and the time delay is 10-30 s; for example, in the present embodiment, 3 rounds of special wheel unloading are provided, each round-cut load amount is 3%, and the 3 rounds of special wheel delay time is set to 15s, 20s, and 25s in sequence.
The basic wheel load per round cutting calculation mode is as follows:
in the formula: delta P i Expressing the ith round cutting load quantity; delta P max Representing the maximum power shortage of the system; k L Representing a load frequency adjustment coefficient; f. of 0 Represents the steady state frequency; f. of N Indicating the last wheel action frequency.
The difference of the proportion of the new energy fan in the system influences the frequency change condition of the system inertia and under large disturbance, and when the wind turbine generator is high in proportion, the first-wheel load reduction amount can be properly improved, and the basic wheel delay can be shortened. Considering that the wind turbine generator may be off-grid due to low-frequency protection, the increased load shedding amount needs to be evenly divided into the first rounds of low-frequency load shedding according to the actual low-frequency protection fixed value of the wind turbine generator, and preferably, the increased load shedding amount is selected to be evenly divided into the first three rounds of low-frequency load shedding in the embodiment.
Based on the preset load shedding action and the real-time running state of the metallurgical load, the load is cut by adopting a mode of firstly calling the metallurgical load and then calling the common load, and the method specifically comprises the following steps:
firstly, various loads are prioritized, the metallurgical load priority is highest, the rest of common loads are counted according to attributes such as user grade, sensitivity, power supply continuity requirements, power failure loss and the like of each branch load, the evaluation scores obtained finally are summarized through conversion calculation with different weights, and the load priorities are divided according to the scoring conditions;
finally, when the power shortage and the frequency of the power system suddenly drop, the control center sends a load reduction instruction to various loads according to the priority division sequence.
The load priority assessment score is calculated as follows:
M i ＝∑W j S j ；
in the formula: m i Weighting scores of the intelligent power distribution terminal in the ith branch; w is a group of j The weight proportion of the jth index of the branch is taken; s j The final evaluation score for the jth index for that branch.
And calculating the compensation amount of the user based on the compensation pricing of the power grid and the actual participation reduction condition of the metallurgical industry user load, performing economic compensation on the user, and finishing the control of the emergency frequency of the power system.
It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that, while the invention has been described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Meanwhile, the common knowledge of the specific load characteristics and the like known in the embodiments is not described in excess. Finally, the scope of the claims should be determined by the content of the claims, and the description of the embodiments and the like in the specification should be used for interpreting the content of the claims.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (9)
1. An emergency frequency control method for an electric power system with metallurgical load participating in safety auxiliary service is characterized by comprising the following steps:
s1: acquiring an active power shortage initial value of a target power grid, and monitoring a real-time metallurgical industrial load state;
s2: estimating the metallurgical load quantity to be called based on the initial value of the active power shortage and the metallurgical load state;
s3: based on the expected calling of the metallurgical load of the power grid, carrying out demand response compensation pricing through a master-slave game model;
s4: based on the rotational inertia and the frequency change condition of the power grid, setting the low-frequency load shedding action cycle, action time and load shedding amount;
s5: based on the preset load shedding action and the real-time running state of the metallurgical load, the load is cut by adopting a mode of calling the metallurgical load firstly and calling the common load secondly;
s6: and carrying out economic compensation on the user based on the power grid compensation pricing and the final actual load shedding condition of the user.
2. The method according to claim 1, wherein the calculating of the initial value of the active deficit of the target grid specifically comprises:
wherein, Δ P 0 Representing the initial active shortage of the system;
representing the rate of change of the system frequency f with time t; t is sys Representing the equivalent inertia time constant of the system; e sys Represents the total kinetic energy of the system; t is Gi Represents the inertia constant of the synchronous generator i; s Gi Represents the rated capacity of the synchronous generator i; x is the number of Gi Indicating the start-stop state of the synchronous unit when x Gi If =1, it means that the synchronous unit is operating, and when x Gi If =0, the synchronous unit is stopped; n represents the number of synchronous generators within the target grid; t is Nj Representing the inertia constant of the new energy source unit j; s Nj Representing the rated capacity of the new energy machine set j; x is the number of Nj Showing the start-stop state of the new energy unit when x is Nj When the number is not less than 1, the new energy unit is operated, and when the number is x Nj If =0, the new energy machine set is shut down; m represents the number of new energy banks containing inertia in the target power grid.
3. The method for controlling the emergency frequency of the power system with the metallurgical load participating in the safety auxiliary service is characterized in that the metallurgical load amount required to be called is estimated based on the initial value of the active deficit and the metallurgical load state, namely when the adjustable amount of the metallurgical load is larger than the power deficit of the system, the metallurgical load amount of the power grid reduction is the total load shedding amount of the low-frequency load shedding; and when the adjustable amount of the metallurgical load is smaller than the power shortage of the system, the expected adjustable amount of the metallurgical load of the power grid is the total reducible power in the current running state.
4. The method for controlling the emergency frequency of the power system with the metallurgical load participating in the safety auxiliary service is characterized in that a target function is constructed on the power grid side by taking the total demand response income of the maximized power grid side as a target when demand response compensation pricing is carried out through a master-slave game model based on the expected calling of the power grid, and an expression of unit compensation price issued by the power grid is obtained; constructing an objective function by taking the maximized user side response income as the objective function at the user side, substituting the objective function into a unit compensation price expression issued by the power grid and obtained by solving at the power grid side, and solving to obtain the response power delta P of each metallurgical user i The expression of (2) is obtained, each user response power expression is substituted into a target function at the power grid side, and a value of a unit compensation price issued by the power grid is obtained by solving under the condition that constraint conditions are met; and substituting the value of the unit compensation price issued by the power grid into a user side demand response function to obtain the final value of each user response power.
5. The method as claimed in claim 4, wherein the step of constructing the objective function by the grid side with the goal of maximizing the total demand response revenue of the grid side includes:
wherein i = {1,2, …, N }, N represents the number of users affected by grid frequency instability; j = {1,2, …, M }, where M represents the number of users participating in demand response; lambda [ alpha ] i The economic loss brought by the i unit electric quantity of the compensation user is represented; delta P i Indicates that user i is at t i Power over which the period is affected; a is 2 Representing the unit compensation price issued by the power grid; p j Indicating the curtailed power of the jth user in the demand response; t is t j Representing the load reduction time when the user j participates in the demand response; a. The 1 Can representLoss cost caused by important load is avoided; p total The total power of the metallurgical load which can participate in the demand response in real time is expected for the power grid side.
6. The method as claimed in claim 4, wherein the objective function is constructed by the user side with the objective function of maximizing the user side response yield, and the objective function of maximizing the user j response yield comprises:
wherein, a 2 The unit compensation price issued by the power grid is represented; delta P j Indicates that user j is at t j Power over which the period is affected; c. C 1 Represents the production yield directly influenced by the average unit reduction power; c. C 2 The production value loss caused by the production state change corresponding to the average unit power is expressed; delta P j_state Load power representing a change in operating power in the remaining load after load shedding; t is t j_state Indicating the time when the operating power is changed after the load is reduced; delta P j_max Maximum load response capability for user j.
7. The method for controlling the emergency frequency of the power system with metallurgical load participating in the safety auxiliary service as claimed in claim 1, wherein the step of performing the low-frequency deloading action round, action time and deloading amount setting based on the moment of inertia and frequency change of the power grid comprises the following steps:
determining the maximum power shortage, a frequency recovery target value, a low-frequency load shedding first wheel action frequency and a low-frequency load shedding last wheel action frequency of the system;
the load cutting amount of each basic wheel is set according to the average principle, and shorter time delay is set;
a plurality of special wheels are arranged for load shedding, namely the load shedding amount of each wheel of the special wheels is smaller than the load shedding amount of each wheel of the basic wheel; wherein the load cutting amount of each round of the basic round is as follows:
wherein, Δ P k Representing the k-th round cutting load; delta P max Representing the maximum power shortage of the system; k L Representing a load frequency adjustment coefficient; f. of 0 Represents the steady state frequency; f. of N Indicating the last wheel action frequency.
8. The method as claimed in claim 7, wherein when the percentage of the new energy source unit is greater than the predetermined threshold, the first-wheel load shedding amount is increased and the basic wheel delay is shortened, and the increased load shedding amount is divided into the first three low-frequency load shedding rounds according to the low-frequency protection constant value of the new energy source unit.
9. The method for controlling the emergency frequency of the power system with the metallurgical load participating in the safety auxiliary service as claimed in claim 1, wherein the load shedding method adopting the mode of calling the metallurgical load firstly and calling the ordinary load secondly based on the preset load shedding action and the real-time running state of the metallurgical load comprises the following steps:
the method comprises the following steps of (1) prioritizing various loads, wherein the metallurgical load has the highest priority, and the other common loads calculate load priority assessment scores according to indexes of various branches, wherein the indexes at least comprise load user grades, sensitivity, power supply continuity requirements and power failure loss, and the higher the score is, the higher the priority is; the load priority evaluation score of the intelligent power distribution terminal on the ith branch is expressed as:
M i ＝∑W j S j ；
wherein M is i Evaluating scores for the load priority of the intelligent power distribution terminal in the ith branch; w j The weight proportion of the jth index of the branch is taken; s j The final evaluation score of the jth index of the branch;
when the power shortage and the frequency dip of the power system occur, the control center sends load reduction instructions to various loads according to the priority division sequence to determine various load reduction amounts.
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| CN116345451A (en) * | 2023-05-26 | 2023-06-27 | 电子科技大学 | Operation control method and device for variable frequency temperature control load and terminal equipment |
| CN116345451B (en) * | 2023-05-26 | 2023-08-11 | 电子科技大学 | Operation control method and device for variable frequency temperature control load and terminal equipment |
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