CN111864768A - Control method and system for participation of electrolytic aluminum load in primary frequency modulation - Google Patents

Control method and system for participation of electrolytic aluminum load in primary frequency modulation Download PDF

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CN111864768A
CN111864768A CN202010709246.1A CN202010709246A CN111864768A CN 111864768 A CN111864768 A CN 111864768A CN 202010709246 A CN202010709246 A CN 202010709246A CN 111864768 A CN111864768 A CN 111864768A
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series
control
series current
electrolytic aluminum
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张文
鲍鹏
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Shandong University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H02J3/241—The oscillation concerning frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/14—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by switching loads on to, or off from, network, e.g. progressively balanced loading
    • H02J3/144—Demand-response operation of the power transmission or distribution network
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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
    • 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P80/00—Climate change mitigation technologies for sector-wide applications
    • Y02P80/10—Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • 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

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  • Power Engineering (AREA)
  • Electrolytic Production Of Metals (AREA)

Abstract

The present disclosure provides a method and a system for controlling participation of electrolytic aluminum load in primary frequency modulation, wherein a first layer of control is configured to: obtaining a required borne spare capacity value according to the total available capacity of the current electrolytic aluminum plant, and optimizing the spare capacity by taking the minimum control cost as a target to obtain a series current lower limit value; a second tier control configured to: regulating a series current reference value according to the frequency deviation of the electrolysis series, judging whether the series current reference value is lower than a series current lower limit value, if so, enabling the series current reference value to be equal to the series current lower limit value, and stopping regulating the series current reference value; otherwise, continuing to carry out down regulation control on the series current reference values; the upper-layer control carries out optimization control by taking the minimum control cost as a target, and an optimization result is applied to the lower-layer control as a constraint, so that the control economy is improved; the lower-layer control adopts distributed control, and series current is controlled through the self-saturation reactor, so that the continuity and the rapidity of the control are ensured.

Description

Control method and system for participation of electrolytic aluminum load in primary frequency modulation
Technical Field
The disclosure relates to the technical field of demand response of power systems, in particular to a method and a system for controlling electrolytic aluminum load to participate in primary frequency modulation.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
According to GB/T15945-1995, the frequency of the power system is controlled in the range of (50 +/-0.2 Hz) for more than 98%. To meet this criteria, the dispatch center should maintain a sufficient amount of spare capacity. Conventionally, the frequency reserve is taken up by the power generation side, wherein the response time of the primary frequency-modulated reserve should be less than 30 s. However, with the continuing advancement of structural improvements on the energy supply side, installed grid capacity of renewable energy sources (such as wind power, photovoltaic) is also rapidly increasing. The biggest problem of renewable energy is that the output of the renewable energy is influenced by meteorological factors, so that great uncertainty exists, and great challenge is caused to the frequency control of a power system after grid connection. To reduce the impact of renewable energy grid connection, the dispatch center needs to acquire more spare capacity to maintain the frequency within a specified range. Under the background, the standby resources obtained from the power generation side cannot meet the operation requirement of the future power system, and the response from the load side to the demand side becomes the trend of the future development.
An electrolytic aluminum load is typically a load that is energy intensive and has thermal inertia characteristics. The electrolysis process is usually carried out in an electrolysis series (formed by connecting dozens or hundreds of electrolysis baths in series) at 950-970 ℃, and molten aluminum oxide is converted into an aluminum simple substance by using direct current. The power consumption of a single electrolytic series is often dozens to hundreds of megawatts, while the real-time power of the whole electrolytic aluminum plant comprises a plurality of electrolytic series and can reach more than 1000 megawatts. And the power is cut off or the load is reduced for running in a short time, and the quality of the electrolytic aluminum product cannot be damaged as long as the electrolyte in the electrolytic cell is maintained not to be solidified. Meanwhile, the electrolytic aluminum load has better control characteristics, and the continuous and rapid control of the power can be realized by controlling the rectifier unit. Therefore, the electrolytic aluminum load is considered to be suitable for participating in the frequency control of the power system due to the characteristics of concentrated power, large thermal inertia and good control characteristics. In order to fully consider the physical and economic characteristics of the electrolytic aluminum load, it is of great significance to design a control strategy for the electrolytic aluminum load to participate in primary frequency modulation.
The inventor of the present disclosure finds that the current mode of participating in primary frequency modulation of electrolytic aluminum load has the following problems: (1) at present, the design of a control strategy for participating in primary frequency modulation on electrolytic aluminum load is still in a research stage, and in practice, the load reduction mode of the electrolytic aluminum load is to shut down the electrolytic series (one electrolytic aluminum plant comprises a plurality of electrolytic series), so that the control granularity is large and the continuity is not available; (2) in the existing research of participation of the electrolytic aluminum load in the primary frequency modulation control strategy, only the physical characteristics of the electrolytic aluminum load are considered, but the economic characteristics are not considered, so that the control cost of the electrolytic aluminum load (the economic loss of an electrolytic aluminum plant caused by load reduction) cannot be reduced while the control rapidity is ensured.
Disclosure of Invention
In order to solve the defects of the prior art, the present disclosure provides a control method and a control system for participating in primary frequency modulation of electrolytic aluminum load, which are divided into an upper layer control and a lower layer control, wherein the upper layer control carries out optimization control with the aim of minimizing control cost, and the optimization result is used as constraint to be applied to the lower layer control, so that the control economy is improved; the lower-layer control adopts distributed control, and series current is controlled through the self-saturation reactor, so that the continuity and the rapidity of the control are ensured.
In order to achieve the purpose, the following technical scheme is adopted in the disclosure:
the first aspect of the disclosure provides a method for controlling the participation of electrolytic aluminum load in primary frequency modulation.
A control method for electrolytic aluminum load participating in primary frequency modulation performs double-layer control:
a first layer control configured to: obtaining a required borne spare capacity value according to the total available capacity of the current electrolytic aluminum plant, and optimizing the spare capacity by taking the minimum control cost as a target to obtain a series current lower limit value;
a second tier control configured to: regulating a series current reference value according to the frequency deviation of the electrolysis series, judging whether the series current reference value is lower than a series current lower limit value, if so, enabling the series current reference value to be equal to the series current lower limit value, and stopping regulating the series current reference value; otherwise, continuing to carry out the down regulation control of the series of current reference values.
As some possible implementations, the first layer of control specifically includes:
collecting the available capacity of each electrolysis series at the beginning of each scheduling period, and evaluating the total available capacity of the electrolytic aluminum plant based on the sum of the available capacities of all the electrolysis series;
uploading the total available capacity of the electrolytic aluminum plant to the external terminal, and acquiring the value of the required borne spare capacity allocated by the external terminal;
optimally distributing the spare capacity by taking the minimum control cost as a target to obtain an optimal series current lower limit sequence, and applying the optimized series current lower limit value to each electrolysis series controlled by the second layer as a constraint;
judging whether the time interval reaches a scheduling period: and if so, performing the first-layer control again, otherwise, continuously waiting until reaching the next scheduling period.
As some possible implementations, the second layer of control specifically includes:
obtaining the system frequency of the area where the electrolysis series are located;
judging whether the system frequency is lower than an action threshold value, and if so, adjusting down a series current reference value according to the frequency deviation; otherwise, continuously acquiring the system frequency of the area where the electrolysis series are located;
by implementing series current control in the electrolytic aluminum load, the series current value is quickly tracked and stabilized at the series current reference value;
Judging whether the series current reference value is lower than a series current lower limit value set by an upper layer, if so, setting the series current reference value to be equal to the series current lower limit value, and stopping lowering the series current reference value; otherwise, repeating the step after judging whether the system frequency is lower than the action threshold value.
The second aspect of the present disclosure provides a control system for participating in primary frequency modulation of electrolytic aluminum load.
A control system for participating in primary frequency modulation of electrolytic aluminum load comprises:
a first tier control module configured to: obtaining a required borne spare capacity value according to the total available capacity of the current electrolytic aluminum plant, and optimizing the spare capacity by taking the minimum control cost as a target to obtain a series current lower limit value;
a second tier control module configured to: and regulating the series current reference value downwards according to the frequency deviation amount of the electrolysis series, judging whether the series current reference value is lower than the lower limit value of the series current, if so, making the series current reference value equal to the lower limit value of the series current, and stopping regulating the series current reference value downwards, otherwise, continuing to regulate the series current reference value downwards.
A third aspect of the present disclosure provides a medium having a program stored thereon, the program, when executed by a processor, implementing the steps in the method for controlling participation in primary frequency modulation of an electrolytic aluminum load according to the first aspect of the present disclosure.
A fourth aspect of the present disclosure provides an electronic device, which includes a memory, a processor, and a program stored in the memory and executable on the processor, and when the processor executes the program, the processor implements the steps in the method for controlling participation of an electrolytic aluminum load in primary frequency modulation according to the first aspect of the present disclosure.
Compared with the prior art, the beneficial effect of this disclosure is:
1. the method, the system, the medium and the electronic equipment consider the physical characteristics of the electrolytic aluminum load, fully utilize the original series current control scheme in the electrolytic aluminum load in the lower-layer control, and realize the continuous and rapid control of the power of the electrolytic aluminum load.
2. The method, the system, the medium and the electronic equipment provided by the disclosure consider the economic characteristics of the electrolytic aluminum load, carry out fine modeling on the control cost of the electrolytic aluminum load, realize the optimal distribution of the reserve capacity by solving the problem of mixed integer linear programming in the upper-layer control, and effectively reduce the control cost of the electrolytic aluminum load in the process of participating in primary frequency modulation.
3. According to the method, the system, the medium and the electronic equipment, the upper layer control and the lower layer control are mutually independent and are carried out in parallel, and the economical efficiency and the rapidity of the control are considered: the upper layer periodically solves the optimization problem, and applies the optimization result as constraint to the lower layer control to ensure the control economy; the lower layer obeys the upper layer constraint, and meanwhile distributed control is adopted to ensure the rapidity of response.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
Fig. 1 is a flowchart of an implementation of a hierarchical control method for participating in primary frequency modulation of an electrolytic aluminum load considering control cost according to embodiment 1 of the present disclosure.
Fig. 2 is a schematic diagram of a hierarchical control architecture of an aluminum electrolysis plant provided in embodiment 1 of the present disclosure.
Fig. 3 is a schematic diagram of piecewise linearization of the spare capacity optimal allocation problem provided in embodiment 1 of the present disclosure.
Fig. 4 is a lower control block diagram of the electrolytic aluminum load participating in primary frequency modulation provided in embodiment 1 of the present disclosure.
Fig. 5 is a schematic diagram of frequency-series current droop control provided in embodiment 1 of the present disclosure.
Fig. 6 is a wiring diagram of a modified four-machine two-zone arithmetic system provided in embodiment 1 of the present disclosure.
Fig. 7 is a system frequency variation curve resulting from dc blocking failure at different levels of electrolytic aluminum backup provided in example 1 of the present disclosure.
Fig. 8 is a histogram of control cost of an aluminum electrolysis plant with and without hierarchical control under different power reduction scenarios provided in example 1 of the present disclosure.
Detailed Description
The present disclosure is further described with reference to the following drawings and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict.
Example 1:
as shown in fig. 1, embodiment 1 of the present disclosure provides a hierarchical control method for participating in primary frequency modulation of an electrolytic aluminum load considering control cost, and performs double-layer control:
An upper layer control configured to: obtaining a required borne spare capacity value according to the total available capacity of the current electrolytic aluminum plant, and optimizing the spare capacity by taking the minimum control cost as a target to obtain a series current lower limit value;
a lower layer control configured to: regulating a series current reference value according to the frequency deviation of the electrolysis series, judging whether the series current reference value is lower than a series current lower limit value, if so, enabling the series current reference value to be equal to the series current lower limit value, and stopping regulating the series current reference value; otherwise, continuing to carry out the down regulation control of the series of current reference values.
The upper layer control specifically comprises the following steps:
step 101: at the beginning of each scheduling period, the upper computer collects the available capacity of each electrolysis series, and estimates the total available capacity of the electrolytic aluminum plant based on the sum of the available capacities of all the electrolysis series.
Step 102: the upper computer interacts with the dispatching center, uploads the total available capacity of the electrolytic aluminum plant to the dispatching center, and obtains the value of the required bearing capacity assigned by the dispatching center.
Step 103: and obtaining an optimal series current lower limit sequence by solving an optimal allocation problem of the spare capacity with the aim of controlling the minimum cost, and applying the optimized series current lower limit value to each lower-layer electrolysis series as a constraint.
Step 104: determine if the time interval in the timer reaches a scheduling period (15 minutes): if yes, the steps 101 to 104 of upper layer control are carried out again; if not, continuing to wait until reaching the next scheduling period.
The lower layer control specifically comprises the following steps:
step 201: the local controller of the electrolysis series measures the system frequency in real time.
Step 202: judging whether the system frequency is lower than an action threshold value: if the frequency deviation is lower than the action threshold value, the controller adjusts the series current reference value downwards according to the frequency deviation; otherwise, continuing to perform the step 1 of the lower layer control.
Step 203: by implementing series current control in the electrolytic aluminum load, the series current value is quickly tracked and stabilized at the series current reference value.
Step 204: judging whether the series current reference value is lower than a series current lower limit value set by an upper layer, if so, setting the series current reference value to be equal to the series current lower limit value, and stopping lowering the series current reference value; otherwise, the steps 202-204 of the lower layer control are repeated.
In the embodiment, a hierarchical control framework of the participation of the electrolytic aluminum load in the primary frequency modulation is constructed, as shown in fig. 2, so that the economy and the rapidity of the participation of the electrolytic aluminum load in the frequency response are ensured.
In the upper-layer control, the upper computer realizes the optimal allocation of the reserve capacity by solving the mixed integer linear programming problem, and applies the optimization result to the lower-layer control as constraint, thereby effectively reducing the control cost of the electrolytic aluminum load in the process of participating in primary frequency modulation; in the lower layer control, each electrolysis series adopts distributed control, and the continuous and rapid control of the load power of the electrolytic aluminum is realized by utilizing the original series current control scheme in the electrolytic aluminum load.
The detailed steps are as follows:
in the upper control step 101, at the beginning of each scheduling period, the upper computer collects the available capacity of each electrolysis series, and estimates the total available capacity of the electrolytic aluminum plant based on the sum of the available capacities of all the electrolysis series.
Specifically, the available capacity information acquired by the upper computer comprises the available capacities of all electrolysis series in the electrolytic aluminum plant:
Figure BDA0002595938050000081
wherein n is the number of electrolytic series in the electrolytic aluminum plant.
For electrolytic series i, its available capacity Pi aviCan be obtained by the following formula:
Figure BDA0002595938050000082
wherein, Ud,iAnd Id,iSeries voltage and series current for the electrolysis series i;
Figure BDA0002595938050000083
and
Figure BDA0002595938050000084
the lowest values of series voltage and series current which can be reached by a rectifier unit in the electrolysis series i in the regulating range are respectively.
Total available capacity of electrolytic aluminium plant
Figure BDA0002595938050000085
It can be obtained by summing the available capacities for all the electrolytic series:
Figure BDA0002595938050000086
in the step 102 of upper layer control, the upper computer interacts with the scheduling center once in each scheduling period (15 minutes). The upper computer uploads the total available capacity of the electrolytic aluminum plant obtained by the calculation to the dispatching center
Figure BDA0002595938050000087
The dispatching center is analyzed and calculated to finally give a decision value of the needed spare capacity to the electrolytic aluminum plant
Figure BDA0002595938050000088
In the process, the requirements of
Figure BDA0002595938050000089
This means that in the next dispatching cycle, the electrolytic aluminum plant must bear the total value of
Figure BDA00025959380500000810
Primary fm spare capacity.
In the step 103 of upper-layer control, the upper computer obtains an optimal series current lower limit sequence by solving an optimal allocation problem of the reserve capacity with the aim of minimizing the control cost, and applies the optimized series current lower limit value as a constraint to each electrolysis series of the lower layer.
First, the control cost C for the electrolytic series iR,iCan be expressed as:
CR,i＝CPD,i+CPW,i(3)
wherein, CPD,iThe direct loss due to the reduction of the yield of primary aluminum is recorded as the yield cost; cPW,iThe loss of electrical energy consumed for the insulation from the electrolytic aluminum load when no output is present is recorded as the energy cost.
Specifically, cost C is controlled R,iCan be expressed as a series current Id,iThe piecewise quadratic function of (d):
Figure BDA0002595938050000091
wherein alpha, beta and gamma are piecewise quadratic function coefficients, 0.3356 is the electrochemical equivalent of aluminum, eta0,iFor the rated current efficiency of the electrolytic series i, M0,iThe raw aluminum yield (ton/hour) of the electrolysis series i under the rated state, cprftIs the net profit ($/ton), c, per ton of raw aluminumfeeIs the electric energy price ($/MWh), Rd,iAnd Ed,iThe cell resistance value and the back electromotive force value r for the electrolytic series iiFor a zone function flag, riSatisfies the following conditions:
Figure BDA0002595938050000092
when series current Id,iHas a lower limit value of
Figure BDA0002595938050000093
In time, the total control cost of the whole plant after load reduction is not more than
Figure BDA0002595938050000094
Wherein
Figure BDA0002595938050000095
Can be expressed as:
Figure BDA0002595938050000096
Figure BDA0002595938050000097
next, the spare capacity optimal allocation problem can be expressed as a quadratic programming problem as follows:
Figure BDA0002595938050000098
wherein the objective function is the plant control cost
Figure BDA0002595938050000101
Minimum, decision variable is series current lower limit sequence
Figure BDA0002595938050000102
And a flag bit sequence r1…rn. The quadratic terms in the objective function and the constraint condition are piecewise linearized as shown in fig. 3, and the quadratic programming problem can be equivalently expressed as a mixed integer linear programming problem:
Figure BDA0002595938050000103
wherein k isc1,i、kc2,i、bc1,iAnd bc2,iPiecewise linearizing slope and intercept for the objective function; k is a radical ofp1,i、kp2,i、bp1,iAnd bp2,iThe slope and intercept of the piecewise linearization of the constraint, M is a very large constant,
Figure BDA0002595938050000104
Is a new decision variable.
In each scheduling period, obtaining a spare capacity decision value issued by a scheduling center
Figure BDA0002595938050000105
Then, obtaining an optimal series of current lower limit sequences by solving the mixed integer programming problem
Figure BDA0002595938050000106
And applies it as a constraint to the underlying control.
In step 104 of the upper control, it is determined whether the time interval in the timer reaches one scheduling period (15 minutes): if the time interval reaches a scheduling period from the last time of the optimized control, the steps 1 to 4 in the upper layer control are carried out again; if not, continuing to wait until reaching the next scheduling period.
Specifically, during the time interval between two scheduling periods, the lower layer control will adopt the latest obtained series current lower limit sequence
Figure BDA0002595938050000107
As its series current constraint.
In the step 201 of the lower layer control, the local controller of the electrolysis series measures the system frequency in real time. In this step, the measured frequency is the system frequency of the area where the electrolysis series is located, and the frequency information can be shared by the dispatching center of the area, or can be autonomously measured by installing a frequency measuring device in the electrolysis plant.
In the lower control step 202, the controller of the electrolysis series monitors the system frequency in real time, if the system frequency f is lower than the action threshold f trigThen the controller is based onAdjusting a series of current reference values by the frequency deviation delta f; otherwise, the frequency is continuously monitored in real time.
Specifically, as shown in FIGS. 4 and 5, the lower control of the electrolysis series employs frequency-series current droop control, when the frequency deviation is Δ f ≧ fref-ftrigThe controller of the electrolysis series I adjusts down the series current reference value Iref,iThe process satisfies the following conditions:
Iref,i＝Iref0,i-KiΔf (10)
wherein f isref50Hz as standard frequency, ftrig49.9Hz, Iref,iFor a series of current reference values, Iref0,iFor series current rating, KiIs the sag factor
In the step 203 of the lower layer control, by implementing the series current control in the electrolytic aluminum load (as shown in fig. 4), the series current value is quickly tracked and stabilized to the series current reference value to realize the quick and continuous load reduction.
The series current control strategy is a control strategy embedded in an electrolytic aluminum load, and a series current I is controlled by a PI (proportional-integral) controllerd,iControl so that the series current Id,iCan track and stabilize at its reference value Iref,i. Series current control strategies are originally used for current stabilization in electrolytic aluminum loads to improve the production efficiency of electrolytic aluminum. In the embodiment of the invention, the inner ring control of the lower layer control is fully utilized, and the rapid continuous power control of the electrolytic aluminum load in the primary frequency modulation process is realized.
In the step 204 of lower layer control, the controller of the electrolysis series judges whether the series current reference value is lower than the series current lower limit value set by the upper layer, if so, the series current reference value I is setref,iEqual to the lower limit of the series current
Figure BDA0002595938050000121
And stopping the down regulation of the series of current reference values; otherwise, continuously adjusting the series current reference value I according to the droop controlref,i。
As shown in FIGS. 4 and 5, in decentralized control of the lower layer, the series of current reference values need to be subject to constraints imposed by the upper layer
Figure BDA0002595938050000122
When detecting that the series current reference value is adjusted downwards to Iref,iBelow its preset lower limit value
Figure BDA0002595938050000123
At the time, set up
Figure BDA0002595938050000124
And stopping the downward regulation of the series of current reference values to realize the control cost in the upper layer control
Figure BDA0002595938050000125
And (4) optimizing.
The modified four-machine two-zone arithmetic example system shown in fig. 6 was simulated, and an electrolytic aluminum plant with real-time power of 1300MW was connected to node 9, the load power at node 7 was 1767MW, the HVDC capacity at node 8 was 400MW, the generators G1-G3 had capacities of 675MW, and G4 had capacities of 642 MW. The electrolytic aluminum plant at node 9 contained 5 electrolytic series, the data of which came from in-field investigations on the aluminum industry in south of Shandong province.
When t is 5s, the HVDC at the node 8 has a direct current blocking fault. FIG. 7 shows that if the load of the electrolytic aluminum does not participate in the primary frequency modulation, the system frequency drops greatly and the control time is longer under a larger disturbance; under the layered control strategy designed by the invention, the electrolytic aluminum load can respond to the frequency deviation on a second-level time scale and reduce the load power to a specified value, thereby ensuring the rapidity of the electrolytic aluminum load participating in primary frequency modulation. Meanwhile, as the spare capacity borne by the electrolytic aluminum load is increased, the control time of primary frequency modulation is shortened, and the frequency drop values are respectively reduced by 0.11Hz, 0.21Hz and 0.24 Hz.
The control cost of the electrolytic aluminum plant is calculated under the scenes that the reduction power of the electrolytic aluminum plant is 100MW, 150MW, 200MW and 250MW respectively, so as to compare the two situations with the situation without hierarchical control. As can be seen in FIG. 8, when not layeredThe control is directly carried out to reduce the load, most of electrolysis series enter a production stop state after being controlled, and the production cost C is causedPDAnd energy cost CPWAre all higher; when the control cost is optimally calculated according to the hierarchical control strategy provided by the invention, the yield cost C under each scene can be effectively reduced by setting the lower limit of the current for the electrolysis seriesPDAnd energy cost CPWAnd the economy of the electrolytic aluminum plant participating in the primary frequency modulation process is ensured.
Example 2:
the second aspect of the present disclosure provides a control system for participating in primary frequency modulation of electrolytic aluminum load, comprising:
a first tier control module configured to: obtaining a required borne spare capacity value according to the total available capacity of the current electrolytic aluminum plant, and optimizing the spare capacity by taking the minimum control cost as a target to obtain a series current lower limit value;
a second tier control module configured to: and regulating the series current reference value downwards according to the frequency deviation amount of the electrolysis series, judging whether the series current reference value is lower than the lower limit value of the series current, if so, making the series current reference value equal to the lower limit value of the series current, and stopping regulating the series current reference value downwards, otherwise, continuing to regulate the series current reference value downwards.
The working method of the system is the same as the layered control method of the electrolytic aluminum load participating in primary frequency modulation considering the control cost provided by the embodiment 1, and the description is omitted here.
Example 3:
the embodiment 3 of the present disclosure provides a medium, on which a program is stored, and when the program is executed by a processor, the method implements the steps in the method for controlling the participation of the electrolytic aluminum load in the primary frequency modulation according to the embodiment 1 of the present disclosure, and the steps are as follows:
a first layer control configured to: obtaining a required borne spare capacity value according to the total available capacity of the current electrolytic aluminum plant, and optimizing the spare capacity by taking the minimum control cost as a target to obtain a series current lower limit value;
a second tier control configured to: regulating a series current reference value according to the frequency deviation of the electrolysis series, judging whether the series current reference value is lower than a series current lower limit value, if so, enabling the series current reference value to be equal to the series current lower limit value, and stopping regulating the series current reference value; otherwise, continuing to carry out the down regulation control of the series of current reference values.
The detailed steps are the same as the layered control method of the electrolytic aluminum load participating in the primary frequency modulation considering the control cost provided by the embodiment 1, and are not described again here.
Example 4:
the embodiment 4 of the present disclosure provides an electronic device, which includes a memory, a processor, and a program stored in the memory and capable of running on the processor, and when the processor executes the program, the method implements the steps of the method for controlling electrolytic aluminum load to participate in primary frequency modulation according to the embodiment 1 of the present disclosure, where the steps are as follows:
a first layer control configured to: obtaining a required borne spare capacity value according to the total available capacity of the current electrolytic aluminum plant, and optimizing the spare capacity by taking the minimum control cost as a target to obtain a series current lower limit value;
a second tier control configured to: regulating a series current reference value according to the frequency deviation of the electrolysis series, judging whether the series current reference value is lower than a series current lower limit value, if so, enabling the series current reference value to be equal to the series current lower limit value, and stopping regulating the series current reference value; otherwise, continuing to carry out the down regulation control of the series of current reference values.
The detailed steps are the same as the layered control method of the electrolytic aluminum load participating in the primary frequency modulation considering the control cost provided by the embodiment 1, and are not described again here.
As will be appreciated by one skilled in the art, embodiments of the present disclosure may be provided as a method, system, or computer program product. Accordingly, the present disclosure may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present disclosure may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, and the like) having computer-usable program code embodied therein.
The present disclosure is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the disclosure. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims (10)

1. A control method for participation of electrolytic aluminum load in primary frequency modulation is characterized by carrying out double-layer control:
a first layer control configured to: obtaining a required borne spare capacity value according to the total available capacity of the current electrolytic aluminum plant, and optimizing the spare capacity by taking the minimum control cost as a target to obtain a series current lower limit value;
a second tier control configured to: regulating a series current reference value according to the frequency deviation of the electrolysis series, judging whether the series current reference value is lower than a series current lower limit value, if so, enabling the series current reference value to be equal to the series current lower limit value, and stopping regulating the series current reference value; otherwise, continuing to carry out the down regulation control of the series of current reference values.
2. The method for controlling the participation of electrolytic aluminum load in primary frequency modulation according to claim 1, wherein the first layer of control is specifically:
collecting the available capacity of each electrolysis series at the beginning of each scheduling period, and evaluating the total available capacity of the electrolytic aluminum plant based on the sum of the available capacities of all the electrolysis series;
uploading the total available capacity of the electrolytic aluminum plant to the external terminal, and acquiring the value of the required borne spare capacity allocated by the external terminal;
Optimally distributing the spare capacity by taking the minimum control cost as a target to obtain an optimal series current lower limit sequence, and applying the optimized series current lower limit value to each electrolysis series controlled by the second layer as a constraint;
judging whether the time interval reaches a scheduling period: and if so, performing the first-layer control again, otherwise, continuously waiting until reaching the next scheduling period.
3. The method for controlling the participation of electrolytic aluminum load in primary frequency modulation according to claim 1, wherein the second layer of control is specifically:
obtaining the system frequency of the area where the electrolysis series are located;
judging whether the system frequency is lower than an action threshold value, and if so, adjusting down a series current reference value according to the frequency deviation; otherwise, continuously acquiring the system frequency of the area where the electrolysis series are located;
by implementing series current control in the electrolytic aluminum load, the series current value is quickly tracked and stabilized at the series current reference value;
judging whether the series current reference value is lower than a series current lower limit value set by an upper layer, if so, setting the series current reference value to be equal to the series current lower limit value, and stopping lowering the series current reference value; otherwise, repeating the step after judging whether the system frequency is lower than the action threshold value.
4. The method for controlling the participation of the electrolytic aluminum load in the primary frequency modulation according to claim 3, wherein the series of currents in the electrolytic aluminum load is controlled by PI control so that the series of currents can track and be stabilized at the series of current reference values.
5. The method of claim 1, wherein the control cost is a sum of a direct loss due to a reduction in the yield of primary aluminum and a loss of power consumed by the electrolytic aluminum load for maintaining the temperature in the absence of output.
6. The method for controlling the participation of the electrolytic aluminum load in primary frequency modulation according to claim 1, wherein the second layer control adopts frequency-series current droop control, specifically: when the frequency deviation is greater than the difference between the frequency reference and the action threshold, the series current reference is the difference between the series current nominal value and the product of the frequency deviation and the droop coefficient.
7. The method for controlling the participation of electrolytic aluminum load in primary frequency modulation according to claim 1, wherein the available capacity of the electrolytic series is obtained based on the current state value in the electrolytic series and the adjustment range of the rectifier unit, and the total available capacity of the electrolytic aluminum plant is obtained based on the available capacity of the electrolytic series.
8. A control system for participating in primary frequency modulation of electrolytic aluminum load is characterized by comprising:
a first tier control module configured to: obtaining a required borne spare capacity value according to the total available capacity of the current electrolytic aluminum plant, and optimizing the spare capacity by taking the minimum control cost as a target to obtain a series current lower limit value;
a second tier control module configured to: and regulating the series current reference value downwards according to the frequency deviation amount of the electrolysis series, judging whether the series current reference value is lower than the lower limit value of the series current, if so, making the series current reference value equal to the lower limit value of the series current, and stopping regulating the series current reference value downwards, otherwise, continuing to regulate the series current reference value downwards.
9. A medium having a program stored thereon, wherein the program, when executed by a processor, implements the steps in the method of controlling participation in primary frequency modulation of an electrolytic aluminum load according to any one of claims 1 to 7.
10. An electronic device comprising a memory, a processor and a program stored on the memory and executable on the processor, wherein the processor executes the program to implement the steps of the method for controlling participation in primary frequency modulation of an electrolytic aluminum load according to any one of claims 1 to 7.
CN202010709246.1A 2020-07-22 2020-07-22 Control method and system for participation of electrolytic aluminum load in primary frequency modulation Pending CN111864768A (en)

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