CN110048443B - Load switching method based on multi-time scale energy supply and comprehensive indexes - Google Patents

Load switching method based on multi-time scale energy supply and comprehensive indexes Download PDF

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CN110048443B
CN110048443B CN201910314317.5A CN201910314317A CN110048443B CN 110048443 B CN110048443 B CN 110048443B CN 201910314317 A CN201910314317 A CN 201910314317A CN 110048443 B CN110048443 B CN 110048443B
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load
period
net
power
energy storage
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CN110048443A (en
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李欣然
刘小龙
刘志谱
张焜
李章溢
刘明爽
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Hunan University
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Hunan University
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28Arrangements for balancing of the load in a network by storage of energy
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381Dispersed generators
    • H02J3/382Dispersed generators the generators exploiting renewable energy
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/48Controlling the sharing of the in-phase component
    • H02J2003/388

Abstract

The invention discloses an energy supply and synthesis device based on multiple time scalesThe method for switching the load according to the indexes comprises the following steps: step 1, dividing a total scheduling period into a plurality of time intervals; step 2: defining a load complementarity index, and defining a load comprehensive index by combining with the load importance index; and step 3: calculating the comprehensive indexes of the loads in the whole scheduling total period, and judging whether the loads can supply energy in the whole scheduling total period one by one according to the descending sequence of the comprehensive indexes; and 4, step 4: judging the loads capable of being powered within a short time scale time interval by time interval on the basis of determining the loads capable of being powered within the whole scheduling total period; step 5, putting in C at the starting time of the whole scheduling total periodLtAll of the loads in (1); and according to CLtThe respective loads and their input periods recorded in' are input with different loads by periods. The invention reduces the imbalance of supply and demand and improves the utilization efficiency of energy.

Description

Load switching method based on multi-time scale energy supply and comprehensive indexes
Technical Field
The invention relates to a load switching method based on multi-time scale energy supply and comprehensive indexes.
Background
When planned power failure occurs, the microgrid system is in an isolated network operation state, and the configured micro power sources are very limited, so that the requirements of cold/heat/electric loads under daily conditions cannot be met. In this case, besides optimizing the output of each micro power supply in the isolated grid, a reasonable load switching (scheduling) strategy needs to be formulated. In practical situations, loads are switched directly according to the importance degree of the loads according to isolated network energy supply conditions. Needless to say, during the planned power failure of the main network, continuous power supply of a first-level load with high reliability requirement is ensured at first, and the disconnection is not considered under any condition; and after the first-level load requirements are met, if the electric energy of the micro-grid system is still remained, the rest second-level load requirements are continuously met. The requirement of secondary load reliability is relatively low, and the economic loss degree is not obviously different. Therefore, in addition to the importance degree of the load, the reasonable load switching scheme can be formulated from the viewpoint of improving the energy utilization rate and the load supply amount.
For a microgrid system containing renewable energy sources such as wind/light and the like, in order to furthest absorb the power generated by the new energy source and improve the energy utilization efficiency, the secondary load demand power can be controlled to be as close as possible to the energy output, the new energy output has great randomness, and if a load switching scheme is determined only according to importance indexes, the problems of repeated switching of loads or low energy utilization rate are easy to occur. The main reason for this problem is the higher importance of the load, and the source-to-load complementarity is not necessarily high.
Therefore, a complementary characteristic evaluation index between a source and a load needs to be introduced to improve a load switching scheme.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a load switching method based on multi-time scale energy supply and comprehensive indexes aiming at the defects of the existing load switching strategy, so that the load importance is considered, the load supply quantity is increased, the load switching times are reduced, and the reliable energy supply of the microgrid system is effectively maintained.
The technical solution of the invention is as follows:
a load switching method based on multi-time scale energy supply and comprehensive indexes comprises the following steps:
step 1: uniformly dividing a total scheduling period, namely planned power failure time into n time periods by taking T as interval time, and taking the starting time and the ending time of each time period as sampling times to obtain n +1 sampling times;
step 2: defining a load PLSource (excluding energy storage) -to-charge complementarity indicator E in the a-th to b-th periods of the scheduled total cyclea~bComprises the following steps:
wherein a and b are positive integers, and satisfy a is more than or equal to 1 and less than or equal to b and less than or equal to n, Ea~bEmbodying the a &β is the negative value of the absolute value of the difference between the source and load power change rates, which reflects the degree of source and load complementation in time periods, wherein, βtRepresenting the degree of source-load complementation during the t period in the total scheduling period; pNET(t +1) and PNET(t) the net electric power of the t +1 th sampling moment and the net electric power of the t th sampling moment are respectively, and the net electric power is equal to the difference between the generated power of all power supply equipment in the microgrid and the required power of all input loads; pL(t +1) and PL(t) loads P at the t +1 th and t-th sampling times, respectivelyLThe power of (d);
on the basis of defining source-load complementarity index and combining with load importance index defining every load PLThe comprehensive index Z in the a-th to b-th periods of the total scheduling cyclea~bComprises the following steps:
Za~b=α·F+β·Ea~b
α are weight coefficients respectively representing the relative importance degree of the load importance and the source-load complementarity, α >0 and α + β are 1, α is determined by an entropy weight method;
and step 3: defining the set formed by all secondary loads in the microgrid as CL(ii) a At the start of the scheduling total period, C is calculated according to the definition in step 2LThe comprehensive index Z of each load in the whole scheduling total period1~nAccording to the comprehensive index Z1~nJudging whether each load can be put into the whole scheduling total period one by one from large to small (namely long-time scale energy supply, energy supply time scale is nT), and finally determining CLIn the load set C which can be invested in the whole scheduling total periodLt
And 4, step 4: determining investment C in the whole scheduling total periodLtOn the basis of all the loads in the system, a set consisting of the rest of the non-input loads is defined as CLDetermining, on a time-by-time basis, the load that can be placed within a short time scale; at the start time τ of each period, C is calculated according to the definition in step 2L' where each load is at the τ th of the total scheduling periodIntegral index Z for tau + k time periodsτ~τ+kAccording to the general index Zτ~τ+kJudging C one by one from big to smallLWhether each load can be put into the scheduling cycle within the time interval from tau to tau + k (namely, the energy is supplied in a short time scale, the energy supply time scale is kT, and kT is less than nT); final determination of CL' the load that can be input in a short time scale and the input period set C thereofLt'; wherein tau + k is less than or equal to n;
and 5: investing C at the starting moment of the whole scheduling total periodLtAll of the loads in (1); and according to CLtThe loads and their input periods recorded in' are input with different loads by periods;
in the step 3 and the step 4, the method for judging whether a load can be input comprises the following steps: and if the sum of the net electric power and the discharge power which can be provided by the energy storage device is more than or equal to 0 in the period from the current moment to the end of the whole scheduling total period after the load is put into use, the load can be put into use, otherwise, the load cannot be put into use.
Further, the step 3 specifically includes the following steps:
3.1) initializing; acquiring an initial state of charge (SOC) of an energy storage device, and acquiring source and charge power prediction data and the like;
3.2) calculating the initial value of the net electric power at each sampling moment and CLImportance indexes of each load;
the initial value of the net electric power at each sampling moment is the difference between the sum of the maximum output of the gas engine, the generated power of new energy such as wind/light and the like and the first-stage load demand power at the moment, namely PNET0(t)=PGE(t)+PPV(t)+PW(t)-PL0(t) wherein PGE(t) is the maximum output of the gas engine at the tth sampling moment, PPV(t) and PW(t) photovoltaic power generation and wind power generation power at the tth sampling time, PL0(t) the power required by the primary important load needing power supply at the tth sampling moment; the initial net electric power is used to supply the secondary load; the wind/light and other new energy power generation power and load power are obtained according to prediction; reference documents: liao, gentle and refreshing, Huzhihong, Mayingying, LuwangOverview of methods for forecasting short-term load of Power systems [ J]Protection and control of electric power systems 2011,39(01): 147-; study on short-term power prediction method based on wind-solar hybrid model [ J]Electric power system protection and control 2015,43(18): 62-66;
load importance index calculation methods references: zhao hui ru, Oudaochang, Zhang qi, etc. evaluation of importance of power users based on ANP grey association [ J ] energy technology economics, 2012,24(7): 38-43;
3.3) calculating C according to the definition in step 2LSource-load complementarity index E of each load in the whole scheduling total period1~nAnd a composite index Z1~n
3.4) hypothetical input CLMiddle comprehensive index Z1~nMaximum load PLWith a required power of P at each sampling instantL(t),t=1,2,...,n;PL(t), t ═ 1, 2.., n, as predicted;
3.5) updating the net electric power at each sampling instant: pNET(t)=PNET(t)-PL(t),t=1,2,...,n;
3.6) determining the Net Electrical Power P at the respective sampling instantsNET(t) whether all the signals are greater than or equal to 0, if so, entering a step 3.7), and otherwise, entering a step 3.8);
3.7) determining the input load PLIt is driven from CLDelete and add to set CLt(ii) a Then, judging CLIf the number of the medium residual loads is more than 0, entering a step 3.3), otherwise, entering a step 3.9);
3.8) judging whether the energy storage device can adjust supply and demand balance: according to the SOC (State of Charge) and the output limit constraint of the energy storage device, the discharge power P which can be provided by the energy storage device at each sampling moment is calculatedBAT(t); if the sum of the net electric power and the discharge power which can be provided by the energy storage device is more than or equal to 0 in the whole scheduling total period after the load is put into use, the step 3.7 is carried out if the sum indicates that the energy storage device can adjust the supply and demand balance, otherwise, the step restores each load if the sum indicates that the energy storage device can not adjust the supply and demand balance (the condition of short supply and short demand occurs), and otherwise, the step restores each load if the sum indicates that the energy storageNet electric power at each sampling instant: pNET(t)=PNET(t)+PL(t), t 1,2, n, and from CLDelete the load, and then judge CLIf the number of the middle residual loads is larger than 0, the step 3.4) is carried out, and if the number of the middle residual loads is equal to 0, the step 3.9) is carried out;
3.9) output CLtI.e. the set of loads that are supplied uninterruptedly during the planned blackout (throughout the total period of the schedule).
Further, the step 4 specifically includes the following steps:
4.1) recording the completion of the input C at each sampling momentLtNet electric power P after medium loadNET(t) energy storage charging and discharging power PBAT(t);
4.2) initializing τ ═ 1;
4.3) judging whether the supply and demand are balanced at the tau-th to the tau + k-th sampling moments (namely the sum of the net electric power and the discharge power which can be provided by the energy storage device is equal to 0) and whether the energy storage devices have discharge states, if so, entering a step 4.10), namely, the energy storage device is not used for supplying energy for other loads in a short time scale, otherwise, the maximum value (namely max { P) in the net electric power at each sampling moment is shownNET(t) | t ═ τ, τ +1,. tau + k }) greater than 0, then go to step 4.4), i.e. continue to supply energy to other loads for a short time scale using the net electric power and the energy storage device; the flexible scheduling rule of the energy storage device is set in the step, so that the energy storage capacity is prevented from being intensively used in a certain time period, and the space-time transfer capacity of the energy storage device in the whole planned power failure period is fully exerted;
4.4) calculating C according to the definition in step 2L' Source-load complementarity indicator E of each load in the τ to τ + k periods of the total scheduling cycleτ~τ+kAnd a composite index Zτ~τ+k
4.5) assume that C is dropped at the t-th sampling instantL' middle comprehensive index Zτ~τ+kMaximum load PLWith a required power of P at each sampling instantL(t),t=1,2,...,n;PL(t), t ═ 1, 2.., n, as predicted;
4.6) update PLEach of the input periods (in the period of tau to tau + k)Net electric power at each sampling instant: pNET(t)=PNET(t)-PL(t),t=τ,τ+1,..,τ+k;
4.7) determination of PLNet electric power P at each sampling instant in the commissioning periodNET(t) whether all the signals are greater than or equal to 0, if so, entering a step 4.8), and if not, entering a step 4.9);
4.8) determining the input load PLIt is driven from CL' deleted in (1) and added to set C with its invested periodLt'; then, the maximum value (i.e., max { P) of the net electric power at each sampling time within the invested period is judgedNET(t) | t ═ τ, τ + 1., τ + k }) is greater than 0, if not, step 4.10) is carried out, namely, the energy storage device is not used for supplying energy to other loads in a short time scale, and if yes, C is judgedL' the number of residual loads in the process; if the number of the residual loads is more than 0, entering a step 4.4), otherwise, entering a step 4.10); the flexible scheduling rule of the energy storage device is set in the step, so that the energy storage capacity is prevented from being intensively used in a certain time period, and the space-time transfer capacity of the energy storage device in the whole planned power failure period is fully exerted;
4.9) judging whether the energy storage device can adjust the supply and demand balance, and calculating the discharge power P which can be provided by the energy storage device at each sampling moment in the period from the tau to the n according to the SOC (State of Charge) of the energy storage device and the constraint of the output limit valueBAT(t), t ═ τ, τ +1,. ·, n + 1; if the sum of the net electric power and the discharge power which can be provided by the energy storage device is greater than or equal to 0 in the period from the t time to the n time, the energy storage device can adjust the supply and demand balance, the step 4.8 is entered, otherwise, the energy storage device discharges and the supply and demand balance cannot be adjusted (the situation of supply and demand shortage occurs), and the net electric power at each sampling time is recovered: pNET(t)=PNET(t)+PL(t), t τ +1, τ + k, and from CL' delete the load, and then judge CL' the number of the residual loads is greater than 0, the step 4.5) is carried out, and otherwise, the step 4.10) is carried out;
4.10) judging whether tau + k is more than or equal to n +1, if so, entering a step 4.11), otherwise, enabling tau to be tau + k, and entering a step 4.3);
4.11) output CLt'。
Further, T is set to 15min, and k is set to 4.
The working principle of the invention is as follows: and starting from the reason that the supply and demand are unbalanced or the load switching frequency is too high in the importance index switching strategy under the isolated network, a source-load complementary characteristic is introduced to improve the load switching strategy. On the basis of defining the complementarity index, a comprehensive index load switching strategy is provided by combining the load importance index. And considering the requirement of the continuity of the secondary load power supply under the actual condition, a comprehensive index load switching strategy for multi-time scale energy supply is further provided. When a short-time-scale energy supply scheme of the load is determined, a flexible scheduling rule of the energy storage device is set so as to prevent the energy storage capacity from being intensively used in a certain time period and fully exert the space-time transfer capacity of the energy storage device in the whole planned power failure period.
The beneficial effects are that:
(1) a complementary load switching strategy is introduced, so that the imbalance of supply and demand (source-load supply and demand difference) is reduced, and the energy utilization efficiency is improved;
(2) a comprehensive index load switching strategy for multi-time scale energy supply is provided, and the load switching frequency is obviously reduced on the premise of ensuring the load importance and the supply quantity;
(3) the energy storage flexible scheduling rule is formulated, the space-time transfer capability of the energy storage in the whole scheduling period is fully exerted, the load switching strategy based on comprehensive indexes is further optimized, the load switching strategy is more suitable for the energy output, the load switching frequency is obviously reduced on the basis of ensuring the load supply quantity, and the load and the stability of the whole system are favorably improved.
Drawings
FIG. 1 is a block diagram of the general concept of the method of the present invention.
FIG. 2 is a flow chart of step 3 of the present invention.
FIG. 3 is a flow chart of step 4 of the present invention.
Detailed Description
The present invention will be described in more detail with reference to the accompanying drawings and embodiments.
The invention discloses a load switching method based on multi-time scale energy supply and comprehensive indexes, which comprises the following steps:
step 1: uniformly dividing a total scheduling period, namely planned power failure time into n time periods by taking T as interval time, and taking the starting time and the ending time of each time period as sampling times to obtain n +1 sampling times;
step 2: defining a load PLSource (excluding energy storage) -to-charge complementarity indicator E in the a-th to b-th periods of the scheduled total cyclea~bComprises the following steps:
wherein a and b are positive integers, and satisfy a is more than or equal to 1 and less than or equal to b and less than or equal to n, Ea~bβ is the negative value of the absolute value of the difference between the source and load power change rates, and represents the source and load complementary degree in the time period, wherein, βtRepresenting the degree of source-load complementation during the t period in the total scheduling period; pNET(t +1) and PNET(t) the net electric power of the t +1 th sampling moment and the net electric power of the t th sampling moment are respectively, and the net electric power is equal to the difference between the generated power of all power supply equipment in the microgrid and the required power of all input loads; pL(t +1) and PL(t) loads P at the t +1 th and t-th sampling times, respectivelyLThe power of (d);
on the basis of defining source-load complementarity index and combining with load importance index defining every load PLThe comprehensive index Z in the a-th to b-th periods of the total scheduling cyclea~bComprises the following steps:
Za~b=α·F+β·Ea~b
α are weight coefficients respectively representing the relative importance degree of the load importance and the source-load complementarity, α >0 and α + β are 1, α is determined by an entropy weight method;
and step 3: defining the set formed by all secondary loads in the microgrid as CL(ii) a At the start of the scheduling total period, according to step 2Definition of (C) calculationLThe comprehensive index Z of each load in the whole scheduling total period1~nAccording to the comprehensive index Z1~nJudging whether each load can be put into the whole scheduling total period one by one from large to small (namely long-time scale energy supply, energy supply time scale is nT), and finally determining CLIn the load set C which can be invested in the whole scheduling total periodLt
And 4, step 4: determining investment C in the whole scheduling total periodLtOn the basis of all the loads in the system, a set consisting of the rest of the non-input loads is defined as CLDetermining, on a time-by-time basis, the load that can be placed within a short time scale; at the start time τ of each period, C is calculated according to the definition in step 2L' the comprehensive index Z of each load in the period from tau to tau + k of the total scheduling periodτ~τ+kAccording to the general index Zτ~τ+kJudging C one by one from big to smallLWhether each load can be put into the scheduling cycle within the time interval from tau to tau + k (namely, the energy is supplied in a short time scale, the energy supply time scale is kT, and kT is less than nT); final determination of CL' the load that can be input in a short time scale and the input period set C thereofLt'; wherein tau + k is less than or equal to n;
and 5: investing C at the starting moment of the whole scheduling total periodLtAll of the loads in (1); and according to CLtThe loads and their input periods recorded in' are input with different loads by periods;
in the step 3 and the step 4, the method for judging whether a load can be input comprises the following steps: and if the sum of the net electric power and the discharge power which can be provided by the energy storage device is more than or equal to 0 in the period from the current moment to the end of the whole scheduling total period after the load is put into use, the load can be put into use, otherwise, the load cannot be put into use.
Further, the step 3 is shown in fig. 2 as a flowchart, and specifically includes the following steps:
3.1) initializing; acquiring an initial state of charge (SOC) of an energy storage device, and acquiring source and charge power prediction data and the like;
3.2) calculating the net electric work at each sampling momentInitial value of rate and CLImportance indexes of each load;
the initial value of the net electric power at each sampling moment is the difference between the sum of the maximum output of the gas engine, the generated power of new energy such as wind/light and the like and the first-stage load demand power at the moment, namely PNET0(t)=PGE(t)+PPV(t)+PW(t)-PL0(t) wherein PGE(t) is the maximum output of the gas engine at the tth sampling moment, PPV(t) and PW(t) photovoltaic power generation and wind power generation power at the tth sampling time, PL0(t) the power required by the primary important load needing power supply at the tth sampling moment; the initial net electric power is used to supply the secondary load; the wind/light and other new energy power generation power and load power are obtained according to prediction; reference documents: liao and gentle glow, Hu Zhi hong, Maling and shining, Luwang, short term load forecasting method review of electric power system [ J]Protection and control of electric power systems 2011,39(01): 147-; study on short-term power prediction method based on wind-solar hybrid model [ J]Electric power system protection and control 2015,43(18): 62-66;
load importance index calculation methods references: zhao hui ru, Oudaochang, Zhang qi, etc. evaluation of importance of power users based on ANP grey association [ J ] energy technology economics, 2012,24(7): 38-43;
3.3) calculating C according to the definition in step 2LSource-load complementarity index E of each load in the whole scheduling total period1~nAnd a composite index Z1~n
3.4) hypothetical input CLMiddle comprehensive index Z1~nMaximum load PLWith a required power of P at each sampling instantL(t),t=1,2,...,n;PL(t), t ═ 1, 2.., n, as predicted;
3.5) updating the net electric power at each sampling instant: pNET(t)=PNET(t)-PL(t),t=1,2,...,n;
3.6) determining the Net Electrical Power P at the respective sampling instantsNET(t) whether all the signals are greater than or equal to 0, if so, entering a step 3.7), and otherwise, entering a step 3.8);
3.7) determining the input load PLIt is driven from CLDelete and add to set CLt(ii) a Then, judging CLIf the number of the medium residual loads is more than 0, entering a step 3.3), otherwise, entering a step 3.9);
3.8) judging whether the energy storage device can adjust supply and demand balance: according to the SOC (State of Charge) and the output limit constraint of the energy storage device, the discharge power P which can be provided by the energy storage device at each sampling moment is calculatedBAT(t); if the sum of the net electric power and the discharge power which can be provided by the energy storage device is more than or equal to 0 in the whole scheduling total period after the load is put into use, the step 3.7 is carried out if the sum indicates that the energy storage device can adjust the supply and demand balance, otherwise, the sum indicates that the energy storage device can not adjust the supply and demand balance (the situation of supply and demand shortage occurs), and the net electric power at each sampling moment is restored: pNET(t)=PNET(t)+PL(t), t 1,2, n, and from CLDelete the load, and then judge CLIf the number of the middle residual loads is larger than 0, the step 3.4) is carried out, and if the number of the middle residual loads is equal to 0, the step 3.9) is carried out;
3.9) output CLtI.e. the set of loads that are supplied uninterruptedly during the planned blackout (throughout the total period of the schedule).
Further, the step 4 is shown in fig. 3, and specifically includes the following steps:
4.1) recording the completion of the input C at each sampling momentLtNet electric power P after medium loadNET(t) energy storage charging and discharging power PBAT(t);
4.2) initializing τ ═ 1;
4.3) judging whether the supply and demand are balanced at the tau-th to the tau + k-th sampling moments (namely the sum of the net electric power and the discharge power which can be provided by the energy storage device is equal to 0) and whether the energy storage devices have discharge states, if so, entering a step 4.10), namely, the energy storage device is not used for supplying energy for other loads in a short time scale, otherwise, the maximum value (namely max { P) in the net electric power at each sampling moment is shownNET(t) | t ═ τ, τ +1,., τ + k }) greater than 0, then step 4.4) is entered, i.e. the time is short while other loads continue to be charged with the net electrical power and the energy storage deviceSupplying energy at an intermediate scale; the flexible scheduling rule of the energy storage device is set in the step, so that the energy storage capacity is prevented from being intensively used in a certain time period, and the space-time transfer capacity of the energy storage device in the whole planned power failure period is fully exerted;
4.4) calculating C according to the definition in step 2L' Source-load complementarity indicator E of each load in the τ to τ + k periods of the total scheduling cycleτ~τ+kAnd a composite index Zτ~τ+k
4.5) assume that C is dropped at the t-th sampling instantL' middle comprehensive index Zτ~τ+kMaximum load PLWith a required power of P at each sampling instantL(t),t=1,2,...,n;PL(t), t ═ 1, 2.., n, as predicted;
4.6) update PLNet electric power at each sampling instant during the plunge period (during the τ to τ + k periods): pNET(t)=PNET(t)-PL(t),t=τ,τ+1,..,τ+k;
4.7) determination of PLNet electric power P at each sampling instant in the commissioning periodNET(t) whether all the signals are greater than or equal to 0, if so, entering a step 4.8), and if not, entering a step 4.9);
4.8) determining the input load PLIt is driven from CL' deleted in (1) and added to set C with its invested periodLt'; then, the maximum value (i.e., max { P) of the net electric power at each sampling time within the invested period is judgedNET(t) | t ═ τ, τ + 1., τ + k }) is greater than 0, if not, step 4.10) is carried out, namely, the energy storage device is not used for supplying energy to other loads in a short time scale, and if yes, C is judgedL' the number of residual loads in the process; if the number of the residual loads is more than 0, entering a step 4.4), otherwise, entering a step 4.10); the flexible scheduling rule of the energy storage device is set in the step, so that the energy storage capacity is prevented from being intensively used in a certain time period, and the space-time transfer capacity of the energy storage device in the whole planned power failure period is fully exerted;
4.9) judging whether the energy storage device can adjust the supply and demand balance, and calculating the energy storage device at each sampling moment in the period from the tau to the n according to the SOC (State of Charge) of the energy storage device and the constraint of the output limit valueSet the discharge power P that can be suppliedBAT(t), t ═ τ, τ +1,. ·, n + 1; if the sum of the net electric power and the discharge power which can be provided by the energy storage device is greater than or equal to 0 in the period from the t time to the n time, the energy storage device can adjust the supply and demand balance, the step 4.8 is entered, otherwise, the energy storage device discharges and the supply and demand balance cannot be adjusted (the situation of supply and demand shortage occurs), and the net electric power at each sampling time is recovered: pNET(t)=PNET(t)+PL(t), t τ +1, τ + k, and from CL' delete the load, and then judge CL' the number of the residual loads is greater than 0, the step 4.5) is carried out, and otherwise, the step 4.10) is carried out;
4.10) judging whether tau + k is more than or equal to n +1, if so, entering a step 4.11), otherwise, enabling tau to be tau + k, and entering a step 4.3);
4.11) output CLt'。
Compared with the load switching method based on only considering the load importance index, the method can effectively improve the utilization efficiency of energy in a long time scale, obviously reduce the switching frequency of the load and is beneficial to improving the stability of the load and the whole system.

Claims (5)

1. A load switching method based on multi-time scale energy supply and comprehensive indexes is characterized by comprising the following steps:
step 1: uniformly dividing a total scheduling period, namely planned power failure time into n time periods by taking T as interval time, and taking the starting time and the ending time of each time period as sampling times to obtain n +1 sampling times;
step 2: defining a load PLSource-to-load complementarity indicator E in the a-th to b-th periods of the total scheduling cyclea~bComprises the following steps:
wherein a and b are positive integers, and satisfy a is more than or equal to 1 and less than or equal to b and less than or equal to n,βtrepresenting the degree of source-load complementation during the t period in the total scheduling period; pNET(t +1) and PNET(t) the net electric power of the t +1 th sampling moment and the net electric power of the t th sampling moment are respectively, and the net electric power is equal to the difference between the generated power of all power supply equipment in the microgrid and the required power of all input loads; pL(t +1) and PL(t) loads P at the t +1 th and t-th sampling times, respectivelyLThe power of (d);
defining a load PLThe comprehensive index Z in the a-th to b-th periods of the total scheduling cyclea~bComprises the following steps:
Za~b=α·F+β·Ea~b
wherein F represents a load PLα and β are weight coefficients, α and β>0 and α + β ═ 1;
and step 3: defining the set formed by all secondary loads in the microgrid as CL(ii) a At the starting time of the scheduling total period, C is calculated according to the definition in step 2LThe comprehensive index Z of each load in the whole scheduling total period1~nAccording to the comprehensive index Z1~nJudging whether each load can be put into the whole scheduling total period one by one from big to small, and finally determining CLIn the load set C which can be invested in the whole scheduling total periodLt
And 4, step 4: let CL'=CL-CLtDetermining, on a time-by-time basis, a load that can be placed within a short time scale; at the start time τ of each period, C is calculated according to the definition in step 2L' the comprehensive index Z of each load in the period from tau to tau + k of the total scheduling periodτ~τ+kAccording to the general index Zτ~τ+kJudging C one by one from big to smallL' whether each load can be invested in the period from tau to tau + k of the total scheduling period; final determination of CL' the load that can be input in a short time scale and the input period set C thereofLt'; wherein tau + k is less than or equal to n;
and 5: investing C at the starting moment of the whole scheduling total periodLtAll of the loads in (1); and according to CLtRespective loads recorded in' and their input timesSegment, throwing different loads one by one;
in the step 3 and the step 4, the method for judging whether a load can be input comprises the following steps: and if the sum of the net electric power and the discharge power which can be provided by the energy storage device is more than or equal to 0 in the period from the starting moment of putting the load to the end of the whole scheduling total period after putting the load, the load can be put in, otherwise, the load cannot be put in.
2. The multi-time scale energy supply and comprehensive index based load switching method according to claim 1, wherein the step 3 specifically comprises the following steps:
3.1) initializing; acquiring initial charge state and source and charge power prediction data of an energy storage device;
3.2) calculating the initial value of the net electric power at each sampling moment and CLImportance indexes of each load; the initial value of the net electric power at each sampling moment is the difference between the sum of the maximum output of the gas engine and the new energy power generation power and the first-stage load demand power at the moment;
3.3) calculating C according to the definition in step 2LSource-load complementarity index E of each load in the whole scheduling total period1~nAnd a composite index Z1~n
3.4) hypothetical input CLMiddle comprehensive index Z1~nMaximum load PLWith a required power of P at each sampling instantL(t),t=1,2,...,n;
3.5) updating the net electric power at each sampling instant: pNET(t)=PNET(t)-PL(t),t=1,2,...,n;
3.6) determining the Net Electrical Power P at the respective sampling instantsNET(t) whether all the signals are greater than or equal to 0, if so, entering a step 3.7), and otherwise, entering a step 3.8);
3.7) determining the input load PLIt is driven from CLDelete and add to set CLt(ii) a Then, judging CLIf the number of the medium residual loads is more than 0, entering a step 3.3), otherwise, entering a step 3.9);
3.8) judging whether the energy storage device can adjust supply and demandBalancing: according to the SOC of the energy storage device and the output limit value constraint, calculating the discharge power P which can be provided by the energy storage device at each sampling momentBAT(t); if the sum of the net electric power and the discharge power which can be provided by the energy storage device is more than or equal to 0 in the whole scheduling total period after the load is put into use, the step 3.7 is carried out if the energy storage device can adjust the supply and demand balance, otherwise, the energy storage device discharges and the supply and demand balance cannot be adjusted, and the net electric power at each sampling moment is restored: pNET(t)=PNET(t)+PL(t), t 1,2, n, and from CLDelete the load, and then judge CLIf the number of the middle residual loads is larger than 0, the step 3.4) is carried out, and if the number of the middle residual loads is equal to 0, the step 3.9) is carried out;
3.9) output CLtI.e. the set of loads that are supplied uninterruptedly throughout the total period of the schedule.
3. The multi-time scale energy supply and comprehensive index based load switching method according to claim 1, wherein the step 4 specifically comprises the following steps:
4.1) recording the completion of the input C at each sampling momentLtNet electric power P after medium loadNET(t) and stored energy charge-discharge power PBAT(t);
4.2) initializing τ ═ 1;
4.3) judging whether the supply and demand are balanced and whether the energy storage devices have a discharge state at the tau-th to the tau + k-th sampling moments, if so, entering a step 4.10), and if not, entering a step 4.4);
4.4) calculating C according to the definition in step 2L' Source-load complementarity indicator E of each load in the τ to τ + k periods of the total scheduling cycleτ~τ+kAnd a composite index Zτ~τ+k
4.5) assume that C is dropped at the t-th sampling instantL' middle comprehensive index Zτ~τ+kMaximum load PLWith a required power of P at each sampling instantL(t),t=1,2,...,n;
4.6) update PLNet electric power at each sampling instant during the commissioning period: pNET(t)=PNET(t)-PL(t),t=τ,τ+1,..,τ+k;
4.7) determination of PLNet electric power P at each sampling instant in the commissioning periodNET(t) whether all the signals are greater than or equal to 0, if so, entering a step 4.8), and if not, entering a step 4.9);
4.8) determining the input load PLIt is driven from CL' deleted in (1) and added to set C with its invested periodLt'; then, judging PLWhether the maximum value in the net electric power at each sampling moment in the input time period is greater than 0 or not is judged, if not, the step 4.10 is carried out, and if yes, C is judgedLIf the number of the residual loads is more than 0, the step 4.4) is carried out, otherwise, the step 4.10) is carried out;
4.9) judging whether the energy storage device can adjust the supply and demand balance, and calculating the discharge power P which can be provided by the energy storage device at each sampling moment in the period from the tau to the n according to the SOC of the energy storage device and the constraint of the output limit valueBAT(t), t ═ τ, τ +1,. ·, n + 1; if the sum of the net electric power and the discharge power which can be provided by the energy storage device is greater than or equal to 0 in the period from the t time to the n time, the energy storage device can adjust the supply and demand balance, then the step 4.8) is carried out, otherwise, the energy storage device discharges and the supply and demand balance cannot be adjusted, and the net electric power at each sampling time is recovered: pNET(t)=PNET(t)+PL(t), t τ +1, τ + k, and from CL' delete the load, and then judge CL' the number of the residual loads is greater than 0, the step 4.4) is carried out, and otherwise, the step 4.10) is carried out;
4.10) judging whether tau + k is more than or equal to n +1, if so, entering a step 4.11), otherwise, enabling tau to be tau + k, and entering a step 4.3);
4.11) output CLt'。
4. The multi-timescale energy supply and integration index based load switching method according to claim 1, wherein T is set to 15 min.
5. The multi-timescale energy supply and index synthesis based load switching method of claim 4, wherein k is set to 4.
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