1、 Abstract Under the grand vision of Energy Internet,distributed generation technology has attracted more and more attention.However,the randomness and volatility of renewable energy power generation put forward new requirements for power system dispatching strategies,which makes the current strategy
2、 need to improve urgently.To solve this problem,we have studied the strategy for ensuring the balance of supply and demand in power systems through high-energy load,furthermore,proposed a multi-objective optimization model that increases the consumption rate of renewable energy generation by high-en
3、ergy load scheduling and provides a reference for power dispatching of distributed generation in Energy Internet.Index Terms Energy Internet,High-energy load,Power dispatching,Multi-objective optimization scheme I.INTRODUCTION T present,many scholars have focused their research on strategies for sma
4、ll capacity and demand side loads,as interruptible loads,directly controllable loads,electric vehicles and energy storage,to participate in renewable energy consumption.Implementing more scientific economic compensation means and control methods for users through electricity prices and incentive mea
5、sures 1-6.However,Chinas electricity market trading mechanism is not yet mature,real-time electricity prices have not made a breakthrough,measuring and control technology fell behind and the range of demand side dispatchable resources is small,which cause the dispatching requirements could not be sa
6、tisfied.Therefore,high-energy load participating in renewable energy Manuscript received July 15,2018.This work was supported in part by State Grid Shanghai Municipal Electric Power Company.Lingdong Kong is with State Grid Shanghai Municipal Electric Power Company,Shanghai,China.(e-mail:).Yang Dong
7、is with State Grid Shanghai Municipal Electric Power Company,Shanghai,China.(phone:+86-17621905693;e-mail:).Ran Geng is with State Grid Shanghai Municipal Electric Power Company,Shanghai,China.consumption has attracted scholars attention because of its advantages of large adjustment capacity and fas
8、t adjustment speed.The participation of high-energy load in power dispatching is to exchange the highest possible social benefits at the lowest possible cost without affecting production.Some researchers have studied the related issues of controllable load participating in power grid dispatching fro
9、m economical perspective of power demand side management.They provided references for us to establish an effective active control model of high-energy load 7,8.This paper establishes a multi-objective dispatching model,which aims to maximize the consumption of renewable energy and the response benef
10、it for enterprises with high-energy load.This model comprehensively considers power balance constraints,regulation characteristics constraints for high-energy load and new energy constraints.The optimal day-ahead dispatching scheme can be get by using modified particle swarm optimization algorithm t
11、o solve the model,which effectively resolve the contradiction between renewable energy consumption and system economic operation.II.THE OPERATION CHARACTERISTICS AND DISPATCHING MODE OF HIGH-ENERGY LOAD It is known from their operation characteristics that different types of high-energy loads have d
12、ifferent response characteristics when participating in the process of load adjustment.According to the difference,high-energy load can be divided into three categories:discretely adjustable load,transferable load,and continuously adjustable load.A.Discretely Adjustable Load Discretely adjustable lo
13、ad refers to the high-energy load that can be reduced or increased quantitative load within a specified time according to the instructions of power grid dispatching center.Its operation characteristic is that the input and interruption require a certain continuous stabilization time.Research on Mult
14、i-objective Optimization Dispatching Scheme Based on High-energy Load LINGDONG KONG1,YANG DONG1,RAN GENG1,XINYANG WU1,ZHE WANG1,WENZHI ZHAO2 1.State Grid Shanghai Municipal Electric Power Company,Shanghai,China 2.Department of Electrical Engineering,Tsinghua University,Beijing,China A 2018 China Int
15、ernational Conference on Electricity Distribution Tianjin,17-19 Sep.2018CICED2018 Paper No.201805280000128 Page1/8 1718 Therefore,it is only used for day-ahead adjustment and cannot be continuously adjusted.Discretely adjustable loads mainly include aluminum electrolytic load,silicon carbide load,an
16、d ferroalloy load.Its characteristic curve is shown in Fig 1.Fig 1.Characteristic curve of discretely adjustable load The mathematical model of discretely adjustable load can be expressed as:1_i _ _(1)t t t tLd Ld i i Ld iP P x P=(1)where _itLdP represents the amount of discretely adjustable load i
17、at t period;_tLd iP represents the adjustment amount of discretely adjustable load i at t period;tix represents the adjustment status of discretely adjustable load:when=1tix,load i doesnt adjust at t period;when=0tix,load i adjusts at t period.B.Transferable Load Transferable load is to allocate the
18、 load of a certain period to other reasonable period within a certain time range under the condition that overall power consumption behavior does not be affected.Thereby alleviating the load pressure during rush hours.There is no load interruption in this type of load,so it is necessary to ensure th
19、at the total amount of electricity remains unchanged before and after transfer.It mainly includes auxiliary equipment for high-energy enterprises,such as batching systems.Its characteristic curve is shown in Fig 2.Fig 2.The characteristic curve of transferable load The mathematical model of transfer
20、able load can be expressed as:1_ _ _t t t tLt j Lt j j Lt jP P x P=+(2)Where _tLt jP represents the amount of transferable load j at t period;_tLt jP represents the adjustment amount of transferable load j at t period;tjx represents the startup status of transferable load:when=1tjx,load j transfers
21、at t period;when=0tjx,load j doesnt transfer at t period.C.Continuously Adjustable Load Continuously adjustable load mainly refers to self-supplied power plant.Its adjustment characteristics are the same as those of conventional thermal power unit.With fast response and continuous adjustment,it can
22、be used for day-ahead and intra-day rolling adjustment.The output should consider the maximum and minimum output power constraints,the climbing rate constraints,and so on.Its characteristic curve is shown in Fig 3.Fig 3.The characteristic curve of continuously adjustable load The mathematical model
23、of continuously adjustable load can be expressed as:_1GkNt t tLc k k Gn knP x P=(3)where _ktLcP represents the amount of continuously adjustable load k at t period;_ GkN represents the amount of power unit in self-supplied plant k;_tGn kP represents the active output of power unit n at t period;_tnk
24、x represents the operation status of power unit n:when _=1tnkx,power unit n operates at t period;when _=0tnkx,power unit n stops at t period.III.MULTI-OBJECTIVE OPTIMIZATION DISPATCHING MODEL FOR HIGH-ENERGY LOAD Power system optimization dispatching model belongs to a 2018 China International Confe
25、rence on Electricity Distribution Tianjin,17-19 Sep.2018CICED2018 Paper No.201805280000128 Page2/8 1719 multi-objective optimization problem.Optimization variables include continuous variables(continuously adjustable load)and discrete variables(discretely adjustable load,transferable load and switch
26、ing status.The model is nonlinear,high dimensional and multi-constrained.The day-ahead dispatching mode of high-energy load studied in this paper mainly refers to Pareto optimal solution theory,by which we get the best solution to the multi-objective optimization problem in this study.Based on 24h p
27、ower output forecast of wind and solar power plants,15 minutes is used as a time period to reasonably adjust the high-energy load regulation plan and the output plan of each wind and solar power plant for a total of 96 time periods.A.Optimization Goal Modeling This paper adopts the multi-objective o
28、ptimization theory,combined with the actual situation,with the goal of maximizing the consumption of renewable energy and the response benefit of high-energy load,to optimize the adjustment of high-energy load participating in day-ahead dispatching plan.1)Maximizing the Consumption of Renewable Ener
29、gy This paper mainly considers the sum of wind power consumption and PV consumption._1 1 1maxWSNN TttNew Wind i Solar it i jE P P T=+(4)where NewE is the consumption of renewable energy;T represents the total number of time periods during a dispatching cycle,there are 96 time periods in day-ahead pl
30、an;tWind iP _ represents the increased power of wind plant i at t period;tSolar jP _ represents the increased power of PV station j at t period;T is the duration of each period;WN is the number of wind plant;SN is the number of PV station.2)Maximizing the Response Benefit of High-energy Load The res
31、ponse benefit of high-energy load is the compensation benefit of renewable energy increased consumption minus the cost of high-energy load adjustment,operation and maintenance.maxH H HB E C=(5)Ld Lt LcN N N Tt t tH H Ld Lt Lct i j kE k P P P=+1 1 1 1(6)()()H Ld Lt LcTttLd Ld Ld LdtTTt t tLt Lt Lc Lc
32、 Lc Lc LcttC C C Cg P h Pr P a P b P c=+=+21211(7)where HE represents the compensation benefits of renewable energy increased consumption paying from power grid dispatching center to high-energy load;HC represents the cost of high-energy load adjustment,operation and maintenance;Hk is compensation c
33、oefficient;tLdP,tLtP and tLcP represent the adjustment amount of discretely adjustable load,transferable load and continuously adjustable load;LdN,LtN and LcN represent the number of discretely adjustable load,transferable load and continuously adjustable load;LdC is the adjustment cost of discretel
34、y adjustable load,Ldg and Ldh are cost parameters;LtC is the adjustment cost of transferable load,in proportion to the adjustment amount,Ltr is the proportional coefficient;LcC is the adjustment cost of continuously adjustable load,that is the adjustment cost of the self-supplied power plant,which i
35、s a quadratic function of the adjustment amount.B.Constraints Modeling Constraints include system power balance constraints,renewable energy constraints,high-energy load regulation constraints,etc.Among them,the high-energy load regulation constraints are divided into three categories:discretely adj
36、ustable load,transferable load and continuously adjustable load.1)System Power Balance Constraints That is the power generated by the wind farm and the photovoltaic power station is equal to the total adjustment of the high-energy load._W S Ld Lt LcN N N N Nt t t t tWind i Solar j Ld Lt Lci j i j kP
37、 P P P P=+=+1 1 1 1 1(8)2)Renewable Energy Constraints _ _ _ _ _ttWind i W abandttSolar j S abandt t tW aband W pre W plant t tS aband S pre S planPPPPP P PP P P=00(9)where tW abandP_ and tS abandP_ represent the abandoned value of wind power and photovoltaic at t period;tW preP_ and tprePS_ represe
38、nt the forecast value of wind power and photovoltaic at t period;tW planP_ and tS planP_ represent the planned value of wind power and photovoltaic at t period.2018 China International Conference on Electricity Distribution Tianjin,17-19 Sep.2018CICED2018 Paper No.201805280000128 Page3/8 1720 3)High
39、-energy Load Regulation Constraints a)Discretely Adjustable Load Constraints(1)Adjustment Amount Constraint Enterprises with high-energy load participate in load regulation under the premise of ensuring product quality.Its adjustment amount is limited.min _ maxtLd Ld i LdP P P(10)Where max LdP and m
40、in LdP represent the upper and lower limits of the adjustable amount of discretely adjustable load.(2)Adjustment Number Constraint The number of adjustment for discretely adjustable load should be less than the maximum number of adjustment.110Ttti i Ldtx x F=(11)where LdF is the maximum number of ad
41、justment for discretely adjustable load.b)Transferable Load Constraints(1)Total load balance constraint 0_1TtLt j Lt jtPP=(12)where 0_ Lt jP is the original total load of transferable load j in the dispatching cycle;T represents the total time period in the dispatching cycle.(2)Transfer Amount Const
42、raint The transfer amount of transferable load is constrained by the maximum transfer amount.max_ Lt j Lt jPP(13)where max_ Lt jP is the maximum transfer amount of transferable load.c)Continuously Adjustable Load Constraint(1)Upper and Lower Limits of Output Power,min _k,maxtGn Gn GnP P P(14)where _
43、 max GnP and _ min GnP represent the upper and lower limits of output power of self-supplied power unit n.(2)Climbing Rate Constraint 1 maxGn_ Gn_ttk k nP P P(15)where maxnP is the maximum allowable power change value of the unit n from time period t-1 to time period t.In summary,the multi-objective
44、 optimization dispatching model for high-energy load can be described as:()()()max,1,2,.0,1,2,0,1,2,ijkf x i ms t h x j pg x k q=(16)where(x),i 1,2,ifm=are objective functions;1(x,x)nx=is n-dimensional decision variable;()0,1,2,jh x j p=are equality constraints;(x)0,1,2,kg k q=are inequality constra
45、ints.IV.MODEL SOLVING METHOD FOR MULTI-OBJECTIVE EVOLUTIONARY ALGORITHM BASED ON DECOMPOSITION The multi-objective evolutionary algorithm based on decomposition(MOEA/D)applied in this section includes two parts:decomposition algorithm and evolutionary algorithm.The decomposition algorithm transforms
46、 the entire optimal frontier approximation problem into several single-objective optimization subproblems.The evolutionary algorithm aims to optimize each sub-problem by evolutionary operation of its neighboring sub-problems.The optimal frontier of multi-objective optimization problem is obtained th
47、rough multiple iterations.Then the optimal trade-off solution is selected by fuzzy membership function,which provides a scientific decision-making basis for power grid dispatching operation.Chebyshev decomposition method and differential evolution(DE)algorithm are used in this paper.The Chebyshev de
48、composition method is insensitive to the shape of the optimal frontier curve and is suitable for solving the problems of non-convexity and discontinuity of Pareto frontier 22.The optimization process of DE algorithm includes steps such as population initialization,mutation,intersection,and selection
49、.Using this algorithm,an optimal day-ahead dispatching scheme can be obtained,which effectively resolves the contradiction between renewable energy generation and system economic operation.The specific process of the algorithm is as follows.A.Constraints Process MOEA/D algorithm was originally propo
50、sed to solve the problem of unconstrained.But the problem of optimization model in this paper is accompanied by equality and inequality constraints,such as renewable energy output balance,high-energy load adjustment range,etc.The MOEA/D algorithm cannot be used directly and needs to be optimized 201
