CN110048443B  Load switching method based on multitime scale energy supply and comprehensive indexes  Google Patents
Load switching method based on multitime scale energy supply and comprehensive indexes Download PDFInfo
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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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Classifications

 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
 H02J3/28—Arrangements for balancing of the load in a network by storage of energy

 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
 H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
 H02J3/381—Dispersed generators
 H02J3/382—Dispersed generators the generators exploiting renewable energy

 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
 H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
 H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
 H02J3/48—Controlling the sharing of the inphase 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 period_{Lt}All of the loads in (1); and according to C_{Lt}The 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
Technical Field
The invention relates to a load switching method based on multitime 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 firstlevel load with high reliability requirement is ensured at first, and the disconnection is not considered under any condition; and after the firstlevel load requirements are met, if the electric energy of the microgrid system is still remained, the rest secondlevel 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 sourcetoload 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 multitime 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 multitime 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 P_{L}Source (excluding energy storage) tocharge complementarity indicator E in the ath to bth periods of the scheduled total cycle_{a～b}Comprises 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, E_{a～b}Embodying 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, β_{t}Representing the degree of sourceload complementation during the t period in the total scheduling period; p_{NET}(t +1) and P_{NET}(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; p_{L}(t +1) and P_{L}(t) loads P at the t +1 th and tth sampling times, respectively_{L}The power of (d);
on the basis of defining sourceload complementarity index and combining with load importance index defining every load P_{L}The comprehensive index Z in the ath to bth periods of the total scheduling cycle_{a～b}Comprises the following steps:
Z_{a～b}＝α·F+β·E_{a～b}
α are weight coefficients respectively representing the relative importance degree of the load importance and the sourceload 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 C_{L}(ii) a At the start of the scheduling total period, C is calculated according to the definition in step 2_{L}The comprehensive index Z of each load in the whole scheduling total period_{1～n}According to the comprehensive index Z_{1～n}Judging whether each load can be put into the whole scheduling total period one by one from large to small (namely longtime scale energy supply, energy supply time scale is nT), and finally determining C_{L}In the load set C which can be invested in the whole scheduling total period_{Lt}；
And 4, step 4: determining investment C in the whole scheduling total period_{Lt}On the basis of all the loads in the system, a set consisting of the rest of the noninput loads is defined as C_{L}Determining, on a timebytime 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 2_{L}' where each load is at the τ th of the total scheduling periodIntegral index Z for tau + k time periods_{τ～τ+k}According to the general index Z_{τ～τ+k}Judging C one by one from big to small_{L}Whether 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 C_{L}' the load that can be input in a short time scale and the input period set C thereof_{Lt}'; wherein tau + k is less than or equal to n;
and 5: investing C at the starting moment of the whole scheduling total period_{Lt}All of the loads in (1); and according to C_{Lt}The 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 C_{L}Importance 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 firststage load demand power at the moment, namely P_{NET0}(t)＝P_{GE}(t)+P_{PV}(t)+P_{W}(t)P_{L0}(t) wherein P_{GE}(t) is the maximum output of the gas engine at the tth sampling moment, P_{PV}(t) and P_{W}(t) photovoltaic power generation and wind power generation power at the tth sampling time, P_{L0}(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 shortterm load of Power systems [ J]Protection and control of electric power systems 2011,39(01): 147; study on shortterm power prediction method based on windsolar hybrid model [ J]Electric power system protection and control 2015,43(18): 6266;
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): 3843;
3.3) calculating C according to the definition in step 2_{L}Sourceload complementarity index E of each load in the whole scheduling total period_{1～n}And a composite index Z_{1～n}；
3.4) hypothetical input C_{L}Middle comprehensive index Z_{1～n}Maximum load P_{L}With a required power of P at each sampling instant_{L}(t)，t＝1,2,...,n；P_{L}(t), t ═ 1, 2.., n, as predicted;
3.5) updating the net electric power at each sampling instant: p_{NET}(t)＝P_{NET}(t)P_{L}(t)，t＝1,2,...,n；
3.6) determining the Net Electrical Power P at the respective sampling instants_{NET}(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 P_{L}It is driven from C_{L}Delete and add to set C_{Lt}(ii) a Then, judging C_{L}If 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 calculated_{BAT}(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: p_{NET}(t)＝P_{NET}(t)+P_{L}(t), t 1,2, n, and from C_{L}Delete the load, and then judge C_{L}If 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 C_{Lt}I.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 moment_{Lt}Net electric power P after medium load_{NET}(t) energy storage charging and discharging power P_{BAT}(t)；
4.2) initializing τ ═ 1;
4.3) judging whether the supply and demand are balanced at the tauth to the tau + kth 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 shown_{NET}(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 spacetime 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 2_{L}' Sourceload complementarity indicator E of each load in the τ to τ + k periods of the total scheduling cycle_{τ～τ+k}And a composite index Z_{τ～τ+k}；
4.5) assume that C is dropped at the tth sampling instant_{L}' middle comprehensive index Z_{τ～τ+k}Maximum load P_{L}With a required power of P at each sampling instant_{L}(t)，t＝1,2,...,n；P_{L}(t), t ═ 1, 2.., n, as predicted;
4.6) update P_{L}Each of the input periods (in the period of tau to tau + k)Net electric power at each sampling instant: p_{NET}(t)＝P_{NET}(t)P_{L}(t)，t＝τ,τ+1,..,τ+k；
4.7) determination of P_{L}Net electric power P at each sampling instant in the commissioning period_{NET}(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 P_{L}It is driven from C_{L}' deleted in (1) and added to set C with its invested period_{Lt}'; then, the maximum value (i.e., max { P) of the net electric power at each sampling time within the invested period is judged_{NET}(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 judged_{L}' 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 spacetime 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 value_{BAT}(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: p_{NET}(t)＝P_{NET}(t)+P_{L}(t), t τ +1, τ + k, and from C_{L}' delete the load, and then judge C_{L}' 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 C_{Lt}'。
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 sourceload 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 multitime scale energy supply is further provided. When a shorttimescale 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 spacetime 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 (sourceload supply and demand difference) is reduced, and the energy utilization efficiency is improved;
(2) a comprehensive index load switching strategy for multitime 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 spacetime 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 multitime 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 P_{L}Source (excluding energy storage) tocharge complementarity indicator E in the ath to bth periods of the scheduled total cycle_{a～b}Comprises 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, E_{a～b}β 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, β_{t}Representing the degree of sourceload complementation during the t period in the total scheduling period; p_{NET}(t +1) and P_{NET}(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; p_{L}(t +1) and P_{L}(t) loads P at the t +1 th and tth sampling times, respectively_{L}The power of (d);
on the basis of defining sourceload complementarity index and combining with load importance index defining every load P_{L}The comprehensive index Z in the ath to bth periods of the total scheduling cycle_{a～b}Comprises the following steps:
Z_{a～b}＝α·F+β·E_{a～b}
α are weight coefficients respectively representing the relative importance degree of the load importance and the sourceload 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 C_{L}(ii) a At the start of the scheduling total period, according to step 2Definition of (C) calculation_{L}The comprehensive index Z of each load in the whole scheduling total period_{1～n}According to the comprehensive index Z_{1～n}Judging whether each load can be put into the whole scheduling total period one by one from large to small (namely longtime scale energy supply, energy supply time scale is nT), and finally determining C_{L}In the load set C which can be invested in the whole scheduling total period_{Lt}；
And 4, step 4: determining investment C in the whole scheduling total period_{Lt}On the basis of all the loads in the system, a set consisting of the rest of the noninput loads is defined as C_{L}Determining, on a timebytime 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 2_{L}' the comprehensive index Z of each load in the period from tau to tau + k of the total scheduling period_{τ～τ+k}According to the general index Z_{τ～τ+k}Judging C one by one from big to small_{L}Whether 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 C_{L}' the load that can be input in a short time scale and the input period set C thereof_{Lt}'; wherein tau + k is less than or equal to n;
and 5: investing C at the starting moment of the whole scheduling total period_{Lt}All of the loads in (1); and according to C_{Lt}The 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 C_{L}Importance 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 firststage load demand power at the moment, namely P_{NET0}(t)＝P_{GE}(t)+P_{PV}(t)+P_{W}(t)P_{L0}(t) wherein P_{GE}(t) is the maximum output of the gas engine at the tth sampling moment, P_{PV}(t) and P_{W}(t) photovoltaic power generation and wind power generation power at the tth sampling time, P_{L0}(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 shortterm power prediction method based on windsolar hybrid model [ J]Electric power system protection and control 2015,43(18): 6266;
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): 3843;
3.3) calculating C according to the definition in step 2_{L}Sourceload complementarity index E of each load in the whole scheduling total period_{1～n}And a composite index Z_{1～n}；
3.4) hypothetical input C_{L}Middle comprehensive index Z_{1～n}Maximum load P_{L}With a required power of P at each sampling instant_{L}(t)，t＝1,2,...,n；P_{L}(t), t ═ 1, 2.., n, as predicted;
3.5) updating the net electric power at each sampling instant: p_{NET}(t)＝P_{NET}(t)P_{L}(t)，t＝1,2,...,n；
3.6) determining the Net Electrical Power P at the respective sampling instants_{NET}(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 P_{L}It is driven from C_{L}Delete and add to set C_{Lt}(ii) a Then, judging C_{L}If 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 calculated_{BAT}(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: p_{NET}(t)＝P_{NET}(t)+P_{L}(t), t 1,2, n, and from C_{L}Delete the load, and then judge C_{L}If 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 C_{Lt}I.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 moment_{Lt}Net electric power P after medium load_{NET}(t) energy storage charging and discharging power P_{BAT}(t)；
4.2) initializing τ ═ 1;
4.3) judging whether the supply and demand are balanced at the tauth to the tau + kth 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 shown_{NET}(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 spacetime 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 2_{L}' Sourceload complementarity indicator E of each load in the τ to τ + k periods of the total scheduling cycle_{τ～τ+k}And a composite index Z_{τ～τ+k}；
4.5) assume that C is dropped at the tth sampling instant_{L}' middle comprehensive index Z_{τ～τ+k}Maximum load P_{L}With a required power of P at each sampling instant_{L}(t)，t＝1,2,...,n；P_{L}(t), t ═ 1, 2.., n, as predicted;
4.6) update P_{L}Net electric power at each sampling instant during the plunge period (during the τ to τ + k periods): p_{NET}(t)＝P_{NET}(t)P_{L}(t)，t＝τ,τ+1,..,τ+k；
4.7) determination of P_{L}Net electric power P at each sampling instant in the commissioning period_{NET}(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 P_{L}It is driven from C_{L}' deleted in (1) and added to set C with its invested period_{Lt}'; then, the maximum value (i.e., max { P) of the net electric power at each sampling time within the invested period is judged_{NET}(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 judged_{L}' 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 spacetime 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 supplied_{BAT}(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: p_{NET}(t)＝P_{NET}(t)+P_{L}(t), t τ +1, τ + k, and from C_{L}' delete the load, and then judge C_{L}' 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 C_{Lt}'。
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 multitime 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 P_{L}Sourcetoload complementarity indicator E in the ath to bth periods of the total scheduling cycle_{a～b}Comprises 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,β_{t}representing the degree of sourceload complementation during the t period in the total scheduling period; p_{NET}(t +1) and P_{NET}(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; p_{L}(t +1) and P_{L}(t) loads P at the t +1 th and tth sampling times, respectively_{L}The power of (d);
defining a load P_{L}The comprehensive index Z in the ath to bth periods of the total scheduling cycle_{a～b}Comprises the following steps:
Z_{a～b}＝α·F+β·E_{a～b}
wherein F represents a load P_{L}α 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 C_{L}(ii) a At the starting time of the scheduling total period, C is calculated according to the definition in step 2_{L}The comprehensive index Z of each load in the whole scheduling total period_{1～n}According to the comprehensive index Z_{1～n}Judging whether each load can be put into the whole scheduling total period one by one from big to small, and finally determining C_{L}In the load set C which can be invested in the whole scheduling total period_{Lt}；
And 4, step 4: let C_{L}'＝C_{L}C_{Lt}Determining, on a timebytime 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 2_{L}' the comprehensive index Z of each load in the period from tau to tau + k of the total scheduling period_{τ～τ+k}According to the general index Z_{τ～τ+k}Judging C one by one from big to small_{L}' whether each load can be invested in the period from tau to tau + k of the total scheduling period; final determination of C_{L}' the load that can be input in a short time scale and the input period set C thereof_{Lt}'; wherein tau + k is less than or equal to n;
and 5: investing C at the starting moment of the whole scheduling total period_{Lt}All of the loads in (1); and according to C_{Lt}Respective 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 multitime 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 C_{L}Importance 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 firststage load demand power at the moment;
3.3) calculating C according to the definition in step 2_{L}Sourceload complementarity index E of each load in the whole scheduling total period_{1～n}And a composite index Z_{1～n}；
3.4) hypothetical input C_{L}Middle comprehensive index Z_{1～n}Maximum load P_{L}With a required power of P at each sampling instant_{L}(t)，t＝1,2,...,n；
3.5) updating the net electric power at each sampling instant: p_{NET}(t)＝P_{NET}(t)P_{L}(t)，t＝1,2,...,n；
3.6) determining the Net Electrical Power P at the respective sampling instants_{NET}(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 P_{L}It is driven from C_{L}Delete and add to set C_{Lt}(ii) a Then, judging C_{L}If 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 moment_{BAT}(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: p_{NET}(t)＝P_{NET}(t)+P_{L}(t), t 1,2, n, and from C_{L}Delete the load, and then judge C_{L}If 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 C_{Lt}I.e. the set of loads that are supplied uninterruptedly throughout the total period of the schedule.
3. The multitime 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 moment_{Lt}Net electric power P after medium load_{NET}(t) and stored energy chargedischarge power P_{BAT}(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 tauth to the tau + kth 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 2_{L}' Sourceload complementarity indicator E of each load in the τ to τ + k periods of the total scheduling cycle_{τ～τ+k}And a composite index Z_{τ～τ+k}；
4.5) assume that C is dropped at the tth sampling instant_{L}' middle comprehensive index Z_{τ～τ+k}Maximum load P_{L}With a required power of P at each sampling instant_{L}(t)，t＝1,2,...,n；
4.6) update P_{L}Net electric power at each sampling instant during the commissioning period: p_{NET}(t)＝P_{NET}(t)P_{L}(t)，t＝τ,τ+1,..,τ+k；
4.7) determination of P_{L}Net electric power P at each sampling instant in the commissioning period_{NET}(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 P_{L}It is driven from C_{L}' deleted in (1) and added to set C with its invested period_{Lt}'; then, judging P_{L}Whether 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 judged_{L}If 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 value_{BAT}(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: p_{NET}(t)＝P_{NET}(t)+P_{L}(t), t τ +1, τ + k, and from C_{L}' delete the load, and then judge C_{L}' 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 C_{Lt}'。
4. The multitimescale energy supply and integration index based load switching method according to claim 1, wherein T is set to 15 min.
5. The multitimescale energy supply and index synthesis based load switching method of claim 4, wherein k is set to 4.
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