Network Reconfiguration in Power Distribution using Tie switches and DG Placements

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The network reconfiguration in power distribution system is done either by opening and closing of tie switches or placing the Distribution Generators (DG) on buses. In this product, we have optimized the tie switch positions and optimal positions of DGs to reduce the active power losses. The network is reconfigured when the tie switches change their positions to minimize the active power losses.

The package contains:

  • Source code for network reconfiguration using optimal placement of tie switches and distribution generators

Note: We don’t claim the documentation file to be plagiarism free and neither support to copy this code for your academic submission. This is to ease your pain to start writing code from scratch. We suggest modifying the code for your work.

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Description

IEEE 33 radial bus system is considered for this case. The optimization used is the hybrid PSO GSA (particles Swarm optimisation and Gravitational Search Algorithm). The IEEE 33 bus system data is loaded and bus loading is changed to demonstrate the effective optimization algorithm. The load is increased by 1.6 times as

loadlevel=1.6; % different loading in the network
Sload=loadlevel.*S(PQb);

Where variable ‘S’ contains the apparent load matrix. backward/Forward Load flow analysis is done on IEEE 33 radial bus system at free-thesis.com. The root soul of our system is the objective function which changes the tie switch positions and place the Distribution generators in the network. For IEEE 33 radial bus system we have a choices of tap switches to be opened or closed, optimal opening/closing of tie switches must be among them during PSOGSA optimization. These are

% switche choices to be opened for network configuration from the loop
% formed by closing tie switches in IEEE 33 radial bus system
tap=[8 9 10 11 21 33 35 0 0
    2 3 4 5 6 7 18 19 20
    12 13 14 34 0 0 0 0 0
    15 16 17 29 30 31 36 32 0
    22 23 24 25 26 27 28 37 0];

Once objective function is called in the optimization, it gets the position of tap switch to be opened, we did it in MATLAB as

BrStatus=X(1:tie);
[baseMVA,bus,branch,tie]=case33radial; % calling data from data file
branch(:,5)=ones(numel(branch(:,5),1));
% open the tie switch of branch in BrStatus
branch(BrStatus,5)=0;

The variable ‘X’ has the status of branch switches and we change the status of tap switch in the IEEE 33 bus data from 1 to 0. To understand it more clearly you must have a look over line data of the IEEE 33 bus system at free-thesis.com

%% Line Data
%   f	t	r(ohm)	x(ohm)	Status	Ratio	RateA
branch=[...
    1	2	0.0922	0.0477	1	0	9990
    2	3	0.493	0.2511	1	0	9990
    3	4	0.366	0.1864	1	0	9990
    4	5	0.3811	0.1941	1	0	9990
    5	6	0.819	0.707	1	0	9990
    6	7	0.1872	0.6188	1	0	9990
    7	8	1.7114	1.2351	1	0	9990
    8	9	1.03	0.74	1	0	9990
    9	10	1.04	0.74	1	0	9990
    10	11	0.1966	0.065	1	0	9990
    11	12	0.3744	0.1238	1	0	9990
    12	13	1.468	1.155	1	0	9990
    13	14	0.5416	0.7129	1	0	9990
    14	15	0.591	0.526	1	0	9990
    15	16	0.7463	0.545	1	0	9990
    16	17	1.289	1.721	1	0	9990
    17	18	0.732	0.574	1	0	9990
    2	19	0.164	0.1565	1	0	9990
    19	20	1.5042	1.3554	1	0	9990
    20	21	0.4095	0.4784	1	0	9990
    21	22	0.7089	0.9373	1	0	9990
    3	23	0.4512	0.3083	1	0	9990
    23	24	0.898	0.7091	1	0	9990
    24	25	0.896	0.7011	1	0	9990
    6	26	0.203	0.1034	1	0	9990
    26	27	0.2842	0.1447	1	0	9990
    27	28	1.059	0.9337	1	0	9990
    28	29	0.8042	0.7006	1	0	9990
    29	30	0.5075	0.2585	1	0	9990
    30	31	0.9744	0.963	1	0	9990
    31	32	0.3105	0.3619	1	0	9990
    32	33	0.341	0.5302	1	0	9990 
     7  20  2.0     2.0     0   0   9990
     8  14  2.0     2.0     0   0   9990
    11  21  2.0     2.0     0   0   9990
    17  32  2.0     2.0     0   0   9990
    24  28  2.0     2.0     0   0   9990 ];
tie=5;

check out the 5th column, it has the last five rows zero as these have tie switches open. After optimization the position of these switches change which is after PSOGSA optimization

==========================================================================================
******************* SIMULATION RESULTS OF 33 BUS DISTRIBUTION NETWORK ********************
==========================================================================================
                       BEFORE RECONFIGURATION              AFTER RECONFIGURATION by PSO             AFTER RECONFIGURATION by PSOGSA
------------------------------------------------------------------------------------------------------------------------------------------------------
Tie switches:              33  34  35  36  37                  10   6  14  31  28                  35   6  13  36  28
------------------------------------------------------------------------------------------------------------------------------------------------------
DGs:                                                      29.95 88.59 62.45 48.39 63.08 50.14     13.60 72.52 80.67 82.73 33.49 33.16
------------------------------------------------------------------------------------------------------------------------------------------------------
Power loss:                603.4308 kW                         427.6137 kW                         254.4125 kW
------------------------------------------------------------------------------------------------------------------------------------------------------
Power loss reduction:      _______                             29.1363 %                             57.839 %
--------------------------------------------------------------------------------------------------------------------------------------------------------
Minimum voltage:           0.83602 pu                          0.94861 pu                          0.94116 pu
---------------------------------------------------------------------------------------------------------------------------------------------------------

We have a constraint here, the change in tap position must respect the radial nature of the system. For this the new network must have determinant of branch injection branch current (BIBC) equal to zero. To calculate the BIBC, power flow analysis must be done for new reconfigured network.

[DistLoadFlowSolution,BIBC]=powerflow (baseMVA,bus,branch,loadlevel); % calling load flow analysis function
% Check on constraint of radial distribution network
%%%%% network will be radial if determinant of Branch incidence matrix will
%%%%% be either 1 or -1
while det(BIBC)==0
       
    for jj=1:dim
        maxL=length(nonzeros(ta(:,jj)));
        BrStatus(jj) = ta(round(1+(maxL-1)*rand),jj);
    end
    [baseMVA,bus,branch,tie]=case33radial; % calling data from data file
    branch(:,5)=ones(numel(branch(:,5),1));
    % open the tie switch of branch in BrStatus
    branch(BrStatus,5)=0;
    [DistLoadFlowSolution,BIBC]=powerflow (baseMVA,bus,branch,loadlevel); % calling load flow analysis function

end

The while loop will check and update the tap positions if radial condition is not met for current set of tap switches.

The distribution generators and its value is also calculated in the objective function. The position is calculated by sensitivity index method.In several research papers the position is also optimally calculated but that only increase the computation overhead, not the accuracy. We adopted the sensitivity index method and find out the buses with highest sensitivity to losses. All buses are arranged in decreasing order of their sensitivity factor and top 6 buses are selected for DG placement. The DG bus power is tuned by optimization and objective function gets the 6 power within range of 0-100 MVA. This power is subtracted from the selected six load buses at free-thesis.com.

    bus(potentialbus,2)=bus(potentialbus,2)-DG;

The second column in ‘bus’ variable contains the IEEE33 bus data’s load values. The power flow analysis is done again and power loss is calculated. Optimization runs till all iterations are not exhausted. Finally by this approach we are able to get the 57.839% for 1.6 time loading in the IEEE 33 radial system.

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