Building artificial intelligence algorithm for reconfiguration distribution network problem

MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY *** Ng NGUYEN TUNG LINH BUILDING ARTIFICIAL INTELLIGENCE ALGORITHM FOR RECONFIGURATION DISTRIBUTION NETWORK PROBLEM Code major: Control theory and Optimization control (Automation and Control Engineering Technology) Code: 62 52 02 16 SUMMARY OF ENGINEERING DOCTORAL THESIS Ha Noi - 2018 2 INTRODUCTION 1. Sep up the problem According to the statistics of Vietnam Electricity Corporation, total power loss in recent years is about 9-15% of electricity production volume, in which distribution of the electrical network holds 5-7%. Then, researching methods for power loss reduction in the distribution network is very urgent demand. Reconfiguaration distribution network is one of methods to minimize power loss which is researched most. Currently, solution of reconfiguaration distribution network problem is optimal one under NP-hard class and then in order to solve this problem, there are some following methods to approach and solve the problem: - Seek by optimal mathematical method - Seek heuristic to seek enough good solution. - Seek near correct solution by natural emulation algorithm such as: Simulated Annealing algorithm, genetic algorithm, herd optimum, etc. 2. Objectives and tasks of the thesis  Propose algorithm by Heuristic method to apply for the problem of reconfiguaration distribution network with objective function for capacity loss reduction considered in the case that there is/is not dispersal power connected into electrical distribution network  Research the effect of dispersal power when connect to the electrical distribution network, affecting the network reconstruction problem.  Propose algorithm by new Meta Heuristic method for reconfiguration distribution network problem with a goal of power losses reudction in the the case that there is/is not as well as consideration to the location and capacity of dispersal power source when it is connected to electrical distribution network. 3. Scope of research  Reconfiguaration distribution network problem with objective function of capacity loss reduction in the case that there is/is not dispersal power source connected to the network.  The problem of electrical distribution network under consideration to the location and capacity of dispersal power source when connect to electrical distribution network with objective function of capacity loss reduction. 4. Researching method  The research is applied Heuristic method and artificial intelligence algorithm for the problem of reconfiguaration distribution network  Use emulation method to check accuracy of proposed algorithms through checking sample problems of IEEE 5. New points of the thesis: the thesis achieves some the following researching contents:  Propose method for the problem of reconfiguaration distribution network on “Heuristic” experience rules with objective function of capacity loss reduction under the consideration of two cases: there is not connection to dispersal power source and there is connection to dispersal power source. 3  Propose the improvement for algorithm of metallurgical emulation for the problem of reconfiguaration distribution network with subjective function of power loss reduction.  Propose using genetic algorithm for the reconfiguarationin the consideration of the location and capacity of dispersal power when connect to distribution network with objective function of capacity loss reduction. 6. Practical value of the thesis: Researching results of the thesis achieved some practical value in the problem of re-configuration solution and actual applications  The method which proposes by the way of researching Heuristic, again can affirm that application of experience rules and optimal method for optimum problems are still used well in some cases.  The researching method according to MetaHeuristic for the problem of electrical network re-configuration is proposed by the author to use Simulated Annealing algorithm and genetic algorithm for the problem of reconfiguaration distribution network with objective function of capacity loss reduction in the case there is dispersal power and there is not dispersal power as well as the case considered to the location, dispersal power capacity connected to distribution network  This is supporting tool for deciding design and operation of distribution network when participate into competitive electrical market. 7. Thesis layout: The thesis is divided into 4 chapters Chapter 1: General view of distribution network and the problem of reconfiguaration distribution network Chapter 2: Heuristic method for the problem of electrical reconfiguaration distribution network Chapter 3: MetaHeuristic method for the problem of electrical distribution problem Chapter 4: Genetic algorithm for the problem of Reconfiguaration distribution network in the consideration of dispersal power planning CHAPTER 1: OVERVIEW OF ELECTRICAL DISTRIBUTION NETWORK AND THE PROBLEM OF ELECTRICAL DISTRIBUTION NETWORK RE- CONFIGURATION 1.1 Introduction of electrical distribution network 1.1.1 Characteristics of electrical distribution network Electrical distribution network is an important component in the supply of electricity from the production site to the electricity consumers, spreading across the whole territory of the country. The distribution network can be designed with a loop structure or a beam structure, but for technical reasons and operating conditions, it is operated in a beam structure. Thanks to the open operating structure, the relay protection system only uses over current relay. Distribution network operating conditions must always meet the following conditions: - Open operating structure - All loads are provided with electricity, pressure drop within the allowed range - The relay protection system must be changed suitably 4 - Lines, transformers and other equipment are not overloaded 1.1.2 Introduction of electrical reconfiguration distribution network a. Introduction of electrical reconfiguration distribution network: Electrical reconfiguaration distribution network problem is the status control of switching equipments in the distribution network, in some operation cases to ensure for some objectives. b. Classification of electrical reconfiguaration distribution network *Classification by objective function: Problem 1: Determine electrical network by load diagram in certain duration for the operation cost to be minimum. Problem 2: Detetrmine non – changeable electrical network in certain duration for power loss to be minimal. Problem 3: Determine structure of electrical network at a certain time for capacity loss to be minimal. Problem 4: Re-configure distribution network to balance load (among lines, transformers at stations) to improve loading capacity of electrical network. Problem 5: Recover electrical network after incident or cutting off power for repairing Problem 6: Determine structure of electrical network by many objectives such as: capacity loss is minimum, highest loading balance, minimum loading transmission, minimum pressure drop at the end of network concurrently happens out, affects of dispersal power source to re- configuration electrical distribution network, etc. Problem 7: Determine electrical network to ensure for objectives of power reduction and stopping supply or improving reliability of power supply. *Classification by researching methods: Figure 1.3 Classification of reconfiguration distribution network by researching method * Some researching results of reconfiguration distribution network  Problem 3 – Determination of reduction network structure P is the most important problem The problem determines the structure of effective capacity loss reduction network – problem is an important one, it is considered as one module to solve other problems in the system of reconfiguration distribution network. It is proved through alogorithms of last researches.  Problem 1 – Minimal function of operation cost This objective function is very function with distribution network with flexible and low load transmission cost in the operation; network structure can be changed in many times in the day. This function is very suitable with distribution network with flexible and low load transmission cost, network structure can be changed in many time in the day. Classification of methods for electrical distribution network reconfiguration solutions Analytic method Heuristic method (Experience law) Meta Heuristic (Use AI algorithm) 5  Problem 2 – Minimal function of power loss In the fact, evenly in developed industrial countries, load transmission cost affects greatly the decision on network structure changes because sometime these costs are bigger than gained benefits. Thus, for problem 2 – Determine non-changeable electrical network structure in surveying time for power loss to be minimal.  Problem 4 – Balance capacity among lines and transformer stations This algorithm can be applied suitably for areas which are usually affected by overload or incertain loads, In [91], Tim Taylor, etc.  Problem 5 – Re-structure distribution network after incident This is objective which is mentioned by almost scientists in their researches.  Problem 6 – Re-structure network under objective function In the operation of distribution network, there are many operation objectives which the controlid must select suitably with characteristics of local electrical networks. 1.1.3 Current status of electrical distribution network in Vietnam Current status of Vietnam’s electrical network - By history of development and in each country, there many grades of distribution voltages and these grades in regions are also different each other (6.6, 10, 15, 22, 35 kV) - Recloser and loaded cutter (LBS) are not controlled remotely and quantity is not considerable then switching cost is big and time for loading transmission is long. Problems during the process of Vietnam’s electrical grip operation are presentated in problem 1 to problem 7 1.1.4 Model of electrical reconfiguration distribution network a. Mathematical model of reconfiguaration distribution network For mathematics, reconfiguration network is the problem for planning discrete curvilinear by the capacity line running on branches, at [78] the model as presented below. Minimal function F =      n i n j ijij n i n j ijijij LCRIC 1 11 1 2 (1.4) Satisfying with:    n 1i jij DS (1.5) Sij  Sij max (1.6) DVij  DVij max (1.7) max.tf n tf tf SS   (1.8) 1 tf tf   (1.9) Objective function is interrupted, it is very difficult to solve reconfiguration distribution network by the method of mathematical analytics traditionally [11]. 6 b. Some assumptions to simplize reconfiguaration distribution network  Reactive power compensation when consider reconfiguration distribution network Ross Baldick [49]: “It is possible to pass away reactive power compensator in the network after solving the problem of electrical distribution network structure determination.”  Some other assumptions for the problem of electrical distribution network re- configuration - Switching operation to transmiss load does not make electrical system to be incertain - Voltage at loading buttons does not change and has value nearly equal to Uđm - When solve capacity distribution problem in the beam network, pass away power loss. - Reliability of power supply in the distribution network seems not to change when network structure changes. 1.2 Overview of researches on re-configuration solutions with objective functions of power loss reduction 1.2.1 Heuristics combination and optimization a. Merlin and Back algorithms – close loop technique b. Other algorithms 1.2.2 Pure algorithms on Heuristics a. Algorithms of Civanlar and partners – Technique of branch change b. Some other algorithms 1.2.3 Algorithms based on artificial intelligence a. Use ANN to re-structure electrical distribution network b. Re-structure network by gen algorithm c. Re-structure network by algorithm of metallurgical emulation d. Re-structure by Ant Colony Algorithm – ACS e. Re-structure by Tabu Search – TS f. Re-structure network by Fuzzy Logic method g. Re-structure network by herd algorithm h. Re-structure network by expert system 1.3. Comments and evaluation 1.3.1 Electrical reconfiguration distribution network with the objective of electrical network control - Almost reconfiguration problems approach different objectives but all of them use problem 3 – to determine structure of electrical distribution network to reduce power loss as main modules during the re-solution problem. - When solve problem 3, algorithms baseds on the researching method by the technique of branch change of Civanlar [17] or close loop technique of Merlin and Back [65] then they usually fall into local minimal and use algorithms of artificial intelligence and evolution in which the most effective one is Gen algorithm and algorithm of metallurgical emulation - Algorithms in problem 3 find out solutions to reduce directly power loss function value for whole network and then it wastes a lot of time because the problem of power distribution must be solved in many times during the repeating process. 1.3.2 Technique for solving electrical network re-structure problem - When approach electrical reconfiguration distribution network, scientists determine that mathematical analystics is not as effective as search algorithm. 7 - Search algorithms are used in the electrical reconfiguration distribution network can be divided into three main directions such as: heuristic search algorithm combines with optimal algorithm; algorithm only uses heuristic rule in expert system; use artificial intelligence including expert system, genetic algorithm, noron network, etc. - Almost algorithms of network re-structure do not show out that network structure has minimal power loss, not prove the point to find out minimal point in overall. Under above reasons, in the own research, the author propses the search of electrical reconfiguration distribution network by 2 directions: research by the way of using Heuristic and MetaHeuristic methods with objective function on power loss reduction. CHAPTER 2: HEURISTIC METHOD FOR ELECTRICAL RECONFIGURATION DISTRIBUTION NETWORK 2.1 Heuristic method for electrical reconfiguration distribution network 2.1.1 Introduction Heuristic algorithm is an expansion to algorithm definition. It presents problem solution with the following characteristics: - Usually seek good solution (but not surely for the best solution) - Solve problem by Heuristic algorithm easily and quickly to give out results rather than optimal algorithm. - Heuristic algorithm is regularly presented naturally, nearly with the thinking way and action of human In the electrical reconfiguration distribution network, Heuristic algorithm was used since long time. Since 1975 until now, there are nearly 80 researches on this problem by using Heuristic as published on famous magazines. 2.1.2 Emulation of electrical reconfiguration distribution network Emulation of electrical network and conventions: Convention: - IPi, IQi are action and reactive current of the branch i; Ri electrical resistance of branch i, - Call k as electrical switch number to ensure for open electrical network operation. On the branch, there is open electrical switch at the jth with the sign: MNj and j = 1...k. Convention choose a set of independent loops in order for each independent loop to cross unique one open electrical switch MNj; the positive direction is counter to the switchwise in the figure 2.1. as hereafter: - Vjh is the set of crossing branches between loop j and loop h; - Vjj is the set under the loop j; - Rj loop is resistance of loop j; - MNj is the branch with openning switch of the jth loop. Indicator Aij states the correlation between the j th loop and natural distribution direction at the the ith branch in the open network Aij = 1: when direction of j loop is the same to directions of IPi and IQi; Aij = -1: When direction of j loop is counter to directions of IPi and IQi; Aij = 0: when the i th branch does not belong to j loop b. Mathematical description of load re-distribution operation. Following with the figure 2.3 8 Consider a simple distribution network consisting of: a single source and a closed loop at the MN branch, as shown in Figure 2.3 (or at the MN branch with IPMN = 0 and IQMN = 0). We need to determine the key to open (on the circuit) to minimize power loss. (Open key may include on-openning key). Assuming that the result is a switch on the MN branch and un switch on the branch AB, then the change in load distribution can be similar to the in / out of the two poles on the branch MN at the current until the current on the AB line is zero c. Conditions for power loss to be minimal after re-distributing P branch load on branches of electrical networks after re-distributing load:                                  K j MNj MN Qj K j MNj MN Pj i n i L l K j MN Qjij DG QlilQii n i L l K j MN Pjij DG PlilPi sau RIRI RIAIBIRIAIBIP 1 2 1 2 2 1 1 1 2 1 1 1 .. 2.1.3 Comments and evaluation - With any distribution network, deriven from a certain (non-optimal) open configuration, if inject/ draw out at the opening switch of an electric current by the formula (2.11), (2.12) to create loop currents through branches, the objective function P will be smallest. - The switch dependent ring number on the loop to inject in / draw out an electric current. Theoretically, if switch is selected for the loop current to inject in or draw out equally to 0, then it is the optimal point. - The expression (2.13) is the sum of the voltage drops on the branches of the j independent circuit if the circuit is pure (or homogeneous circuit). This shows that the optimum value of obtained current under (2.11) and (2.12) is the branch line of the closed distribution network. When close all electrical switches, the losses P in the distribution network are minimal. - - When there are DG resources involved in the distribution network, the optimal expression for the received current will be added to the second component (in expressions (2.11) and (2.12). 2.2 Propose Heuristic algorithm for electrical reconfiguration distribution network 2.2.1 Objective function of the problem. Objective funciton of the problem:            K j K j jvòng j optMN j jvong j optMN Qj jvong j optMN Pj RIRIRIG 1 1 2)(2)(2)( min.. (2.15) 2.2.2 Proposal of new algorithm: Performance procedures follow with two stages as follows: This algorithm has the following characteristics: The objective function shown in this section takes into account the resistance factor of the independent loop. This is a new objective function (previous studies often used to reduce the function P = I2R directly, or simply to find the branch to have the smallest current). G function is meaningful as a comparison criterion, so finding the distribution network configuration with increasing P has at least been taken to the problem of determining the power loss increase function (G function) on distribution network. This enables the algorithm