Power Flow Analysis of Integrated Wind and Solar Power Generation and Distribution System

Power Flow Analysis of Integrated Wind and Solar Power Generation and Distribution System

P. Yuvasri Lakshmi

P.G Student,

Power System Engineering, Kingston Engineering College, Vellore.

Abstract — Power flow analysis is also known as load flow analysis in which per unit voltage and magnitude of the system is analyzed by the MI POWER SOFTWARE using the Newton Naphsion method. Which is faster on the speed of convergence, but programming is more complex suitable for large size system and the number of iterations does not depend on the size of the system, extra retention memory or remembrance is essential. The power flow is not unable to combine parts in power system analysis the main factor incite is the inability regards the power system to meet the demand for reactive power voltage instability does not always occurs in its pure form. A distinction between angle stability is important for understanding the underlying determinant concerning the problem in order to develop appropriate design and operating procedures

Keyword — Load flow analysis; Newton Raphsion method; Extra retention memory; Reactive power voltage instability.

1. INTRODUCTION

   Load flow analysis can be carried out for small and medium size power systems. It suits for the radial distribution system with high R/X ratio. The load flow analysis helps to identify the overloaded/underloaded buses in the system. It is used to study the optimum location of capacity is and their size to improve unacceptable voltage profile Power flow analysis or load flow analysis is performed in a symmetrical steady-state operating condition of a power system under the normal mode of operation. The solution of load flow gives bus voltages and line/ transformer power flow for a prone load condition. This information is essential for long-term planning and operational planning. In the network of the power system, buses become node and a voltage can be specified for each bus. Load flow analysis is essentially concerned with the persistence of complex bus voltages at all busses, given the network configuration and the bus demands. The bus generation and characterized by complex powers flowing into and out of the buses respectively. A generation inventory is nothing but a combination of MW generation of the various generations should match the given requirement plus the transmission losses. It should be noted that there are many generation schedules available to match the prone system demand and one such schedule is chosen for load flow analysis is Newton Raphsion method

2. CLASSIFICATION OF BUSES

   The following information is essential for long term planning and operational planning.

   1. Long-term Planning

      Load flow analysis helps in investigating the effectiveness of alternative plans and choosing the perfect plan for system expansion to meet the projected operating state.

   2. Operational planning

      It helps in choosing the perfect unit commitment plan and generation schedules to run the system efficiently for the next days load condition without contravening the bus voltages and line flow operating limits.

   3. Steps for load flow analysis

      The following work has to be carried for a load flow study. Representation of the system by single line diagram.

      • Decisive impedance design diagram using the information in the single line diagram

      • Formation of network equation

      • Solution of network equation

        The buses are classified based on the variable specified. There are three types of buses.

        1. Slack bus or swing bus or reference bus.

        2. Generator bus or voltage bus or P-V bus or regulator bus.

        3. Load bus or P-Q bus.

        The following table gives the quantities specified and the quantities to be specified for each bus

        Table I.

        S.No	Bus	Quantities Specified	Quantities to be Specified
        1.	Slack Bus	V,	P, Q
        2.	P-V Bus (or) Generator Bus	P,V	Q,
        3.	P-Q Bus (or) Load bus	P,Q	V,

        At these buses, the active and reactive power are specified, the magnitude and phase angle of the voltage are unknown. These are called as load bus

        Advantages of load flow analysis

        In the power system design and operation there are four things that need to be understand

   4. Slack Bus

      In slack bus, voltage magnitude and phase angle of voltages are specified pertaining to a generator bus usually a large capacity generation bus is chosen. We assume voltage (V) as reference phasor

      I.e., = 0

      Where = Phase angle of voltage.

      This bus makes up the difference between the scheduled load and generated power that are caused by the losses in the network.

      The power balance equation is

      • Generation (Type, capacity,forecast and others too)

      • Distribution network A = cross section area

   At 300 metre Resistance R = 0.3021 At 400 metre Resistance R = 0.402 At 200 metre Resistance R = 0.201 At 50 metre Resistance R = 0.0503

   H. The Formula to find Reactance

   X=XL XC

   Where

   XC = 1

   2

   =

   =

   XL = 2fL

   =1

   =1

   =1

   The Formula to find Inductance

   P depends on I2 R loss in the transmission line and

   L=2l[ ((2) (1 + 1 + ( ) 2))

   L

   transformer of the network. The individual current in the various lines of the network cannot be calculated until after

   1 + ( ) 2 + + ( )]

   2

   the voltage magnitude and angle are known at every bus of the system. Therefore, PL is initially unknown. Real and reactive power is not specified for slack bus. In power flow

   Where

   2

   4 2

   problem,we assume one generator bus as a slack bus at which power generation is Prespecified. After the power flow problem has been solved, the difference between the total specified real power going into the system at all the other buses and the total power consumed by loads plus I2 R losses are assigned to the slack bus. Therefore a generator bus must be selected as the slack bus. The slack bus is needed to account for transmission line losses.

   1. Generator bus or P-V bus or Regulated bus

      At these buses, the real power and voltage magnitude are specified. The phase angle of the voltage and the reactive power are also specified.

      In order to maintain a good voltage profile over the system, Automatic Voltage Regulator (AVR) is used.Static VAR compensator buses are called as buses because real power and voltage magnitude are specified at these buses

   2. Load Bus or P-Q Bus

      • Load (Types of Load, demand and forecast).

      • Protection

   3. Calculation of Resistance and reactance of system

      The Formula to find Resistance (R)

      R=

      Where

      = Resistivity L = Length

      d = Diameter

      l =length

      At 300 m Inductance L = 0.000688H At 400 m Inductance L = 0.000939H At 50 m Inductance L = 0.0000966H At 200 m Inductance L = 0.000442H

      Formula for cylindrical Capacitor

      C = 2

      ()

      At 300 m capacitance C = 0.0677F

      At 400 m capacitance C = 0.0810 F

      At 50 m capacitance C = 1.01293×10-8 F At 200 m cpacitance C = 0.04006 F Reactance of 300 m 0.1638

      Reactance of 400 m 0.2556

      Reactance of 50 m 0.28363

      Reactance of 200 m 0.05933

3. SINGLE LINE DIAGRAM

   A single line diagram is a diagrammatic representation of power system in which the components are represented by their symbols and the interconnection between them are shown by a single straight line (even though the system is a three phase system). The ratings and the impedance of the component are also marked on the single line diagram

   20MVa

   250 KVa

   381.97Kw

   • Single phase transformer equivalents are shown as ideal transformers with transformer impedance indicated on appropriate side.

   • Magnetization reactance of the transformers have

     0.33021+0.1638

     0.402+0.2556j

     1. +0.05933j

        Admin

        Main Block 109 Kw

        0.0503+0.2

        63j

        0.0503+0.2

        63j

        E.B

        been neglected.

        • Generator are represented as voltage sources with series resistance and inductive reactance

     1. Steps to draw per unit impedance diagram

        83

        83

        • Choose a common MVA or base MVA for the system (Mostly highest generator rating is taken).

          110Kw

          Hotel Block

          250KVa

          Block

          223.85Kw

          110Kw

          125KVa

          Block

          125KVa

          • Choose an appropriate base KV for each and every section

     2. Applications of Y bus matrix

   • Y-bus is used in solving load flow problems.

   • It has gained applications owing to the simplicity in data preparation

   • It can be easily formed and modified for any

   changes in the network

   Fig. 1. Power system Network

   The scope of the single line diagram is to supply in concise form of the significant information about the system. The power system network is represented by one line diagram using suitable symbols for generator, motor, transformer, transmission line and loads.

   1. Impedance diagram

      The impedance diagram on the single phase basis under balanced operation conditions can be drawn from one line diagram

      Fig. 2. Single Line Diagram

      • It reduces computer memory and time requirements because of sparse matrix

   Y bus is determined by Two-rule method or inspection method.In the equivalent network generators are replaced by Nortons equivalent, the load is replaced by equivalent admittances and the lines replaced by -equivalent circuits.

4. LOAD FLOW ANALYSIS RESULT

   Load flow analysis is done through newton Raphsion method

   Version number: 8.2

   %% first power system network

   The Largest bus number used 8

   Actual number of buses 8

   Number of 2 wind. Transformer 2

   Number of Transmission lines 5

   Number of Loads 4

   Number of solar plants 1

   Number of Generators 2

   Base MVA 50

   Nominal system Frequency (Hz) 50

   Maximum number of iterations 15

   Bus voltage below which load : 0.75 Model is changed

   Transformer R/X Ratio : 0.05

   Annual percentage interest charges 15

   Annual percent operation & 4

   Life of equipment I years 20

   Maintenance charge

   Table I. Bus Data

   BUS NO.	AREA	ZONE	BUS KV	VMIN (P.U.)	VMAX (P.U)	NAM E
   1	1	1	0.415	0.95	1.05	BUS 1
   2	1	1	33.0	.95	1.05	BUS 2
   3	1	1	0.69	0.95	1.05	BUS 3
   4	1	1	0.415	0.95	1.05	BUS 4
   5	1	1	0.415	0.95	1.0	BUS 5
   6	1	1	0.415	0.95	1.05	BUS 6
   7	1	1	0.415	0.95	1.05	BUS 7
   8	1	1	0.415	0.95	1.05	BUS 8

   Table II. Transformer Data

   STATUS RATING	CKT	FROM NODE	TO NODE	IMPEDENCE
   				R (P.U.)	X(P.U.)
   				MINT AP	MAXT AP
   3	2	2	3	0.005	0.11765
   				0.95	1.05
   3	2	2	1	0.1061 8	2.12357
   				0.9105 1	1.00635

   Table III. Transformer Data

   STATUS RATING	CKT	FROM NODE	TO NODE	NOMINAL TAP
   				TAP	MVA
   				TAPSTEP	SHIFT- DE
   3	2	2	3	0.00588	0.11765
   				0.95	1.05
   3	2	2	1	0.10618	2.12357
   				0.91051	1.00635

   CKT	FROM NODE	FROM NAME	TO NOD E	TO NAME	RATING MVA
   					R(P.U)	X(P.U)
   1	4	Bus4	1	Bus1	17.88360	10.2560
   1	1	Bus1	5	Bus5	17.88360	10.62560
   1	1	Bus1	6	Bus6	17.88360	10.62560
   1	1	Bus1	7	Bus7	17.88360	10.62560
   1	1	Bus1	8	Bus8	17.88360	10.62560

   CKT	FROM NODE	FROM NAME	TO NOD E	TO NAME	RATING MVA
   					R(P.U)	X(P.U)
   1	4	Bus4	1	Bus1	17.88360	10.2560
   1	1	Bus1	5	Bus5	17.88360	10.62560
   1	1	Bus1	6	Bus6	1.88360	10.62560
   1	1	Bus1	7	Bus7	17.88360	10.62560
   1	1	Bus1	8	Bus8	17.88360	10.62560

   Table IV. Transmission line data

   1. NO OF ITERATION

      Iteration count 0 maxp 0.00200 max 0.002945

      Iteration count 1 maxp 0.00003 max 0.000022

      Iteration count 2 maxp 0.0000 maxq 0.0000

      Iteration count 3maxp 0 .0000maxq 0.00000

      Iteration count 4 maxp 0.0000 maxq 0.003894

      Itertion count 5 maxp 0.00002 maxq 0.000035

      • The N-R method is faster, more reliable and the result are accurate

      • Required less number of iterations for convergence

      • The number of iterations are independent of the size of the system

      • Suitable for large size systems.

   Fig. 3. Simulation Single Line Diagram Table V. Bus voltage and Powers

   Node No	From name	V-Mag P.U	Angle degree	MW GEN
   1	BUS1	1.0000	0.00	-0.017
   2	BUS2	1.0088	0.24	0.000
   3	BUS3	1.0089	0.25	0.100
   4	BUS4	1.0209	0.27	0.050
   5	BUS5	0.9716	0.18	0.000
   6	BUS6	0.9885	0.07	0.000
   7	BUS7	0.9835	0.1	0.000
   8	BUS8	0.9885	0.07	0.000

   Table VI Bus voltage and Powers

   Node No	From name	MVAr GEN	MW LOAD	MVAr LOAD
   1	BUS1	0.031	0.000	0.000
   2	BUS2	0.000	0.000	0.000
   3	BUS3	0.052	0.000	0.000
   4	BUS4	0.016	0.000	0.000
   5	BUS5	0.000	0.053	0.040
   6	BUS6	0.000	0.022	0.017
   7	BUS7	0.000	0.031	0.024
   8	BUS8	0.000	0.022	0.017

   Table VII. Transformer Flow And Transformer Losses

   Sl. No	CS	FROM NODE	FROM NAME	TO NODE	TO NAME	FORWARD
   						MW	MVAr
   1	1	2	BUS 2	3	BUS 3	-0.100	-0.052
   2	1	2	BUS 2	1	BUS 1	0.100	0.052

   Table VIII.Transformer Flow And Transformer Losses

   Sl. No	CS	FROM NODE	FROM NAME	TO NODE	TO NAME	LOSS
   						MW	MVAr
   1	1	2	BUS 2	3	BUS 3	0.0	0.00
   2	1	2	BUS 2	1	BUS 1	0.0	0.0005

   Table IX. Line Flows And Line Losses

   Sl. No	CS	FROM NAME	TO NAME	FORWARD		Loading
   				MW	MVAr
   3	1	BUS 4	BUS 1	0.050	0.016	60.3
   4	1	BUS 1	BUS 5	0.055	0.041	80.4
   5	1	BUS 1	BUS 6	0.022	0.017	32.5
   6	1	BUS 1	BUS 7	0.032	0.024	46.6
   7	1	BUS 1	BUS 8	0.022	0.017	32.5

5. SUMMARY OF RESULTS Total real power generation

   (CONVENTIONAL) : 0.00 MW

   Tolal reactive power Generation (CONVENTIONAL)

   :0.083 MVAr

   Toal real power generation (WIND)

   :0.100Mw

   Total reat. Power generation (WIND)

   :0.052MVAr

   Total real power generation (WIND)

   : 0.050 MW

   Total reat. Power generation (SOLAR)

   :0.052MVAr

   Total real power load : 0.129MW Total real power drawal(-ve gen) : 0.017MW Total reactive power load : 0.097MVAr

   \

   Fig. 4. Output of Simulation Single Line Diagram

   Load p.f : 0.8

   Total real power loss(AC+DC) : 0.003790 MW

   (0.003790+0.0000)

   Percentage real loss (AC+DC) : 2.527

   Total reactive power loss: : 0.002800MVAr

   A. Zone Wise Distribution Description

   MW generation : -0.0174

   MVAr generation : 0.0312

   MW wind gen. :0.1

   MVAr wind gen. :0.0517

   MW solar gen. :0.0500

   MVAr soalr gen. : 0.0164

   MW load : 0.1288

   MVAr load : 0.0966

   MW loss : 0.0038

   MVAr loss : 0.0028

6. CONCLUSION

From the power flow analysis of a given system optimized power flow stabilized which is having

0.1 MW of generation from wind and 0.5MW of generation from solar to the grid connected system of 20 MW of synchronous generator generation. The corresponding voltage and magnitude are stabilized through reactive power compensation and obtianted per unit voltage of given system is also stabilized.

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