voltage profile improvement in distribution systen using reactive power injection or using companseting devices

1. IMPROVEMENT of VOLTAGE PROFILE
in DISTRIBUTION SYSTEM USING
COMPENSATING DEVICES

2. INTRODUCTION
The current electrical industry consists of central power generation connected by
transmission lines of high voltage.
Electric power is generated at the generating stations and transferred to the load
centers.
The electricity then distributed to the consumers. For this, we have a large network
of low and medium voltages distribution lines.
With the help of these distribution lines electricity is provided to households.
The transmission and Distribution system in combined is known as Delivery
System.

3. Contd..
Transmission Systems:
• Used to evacuate power from the generating stations to the load centers.
Sub-transmission Systems:
• These are usually of reduced capacities and voltage levels.
• These are used to take power from the transmission switching stations or
generation plants and to deliver it to distribution substations.
Primary Distribution Systems:
• These are the basically power networks used to carry power from substations to
distribution transformer.
Secondary Distribution Systems:
• These networks are used to supply power to the end-user/customer.

4. GOALS of POWER DELIVERY SYSTEM
• Cover the utility’s service territory, reaching all consumers who wish to be
connected and purchase power.
• Have sufficient capability to meet the peak demands of these energy
consumers.
• Provide satisfactory continuity of service (reliability) to the consumers.
• Provide stable voltage quality regardless of load level or conditions.
• Maintain the desired power quality to the consumers.

5. BACKGROUND
In the early part of the electric era (1890-1930) most electric utilities
viewed interruptions of service primarily as interruptions in revenue.
The mindset of the utilities changes during the 1930s-1960s due to
the inception of the Digital computer.
The utilities adopt several measures to measure and quantify the
reliability level during 1970-1990, which leads to the development of
supervisory control and data acquisition (SCADA) system, outage
management system etc., to determine which customer is out of
service, and when, and why.
After 1990, the power delivery system undergoes the supervisions of
regulatory commission. In India. This happens after the
implementation of the Electricity Act 2003.

6. According to section 2 (50) Electricity Act 2003,
“Power System” means all aspects of generation, transmission, distribution and
supply of electricity and includes one or more of the following, namely:
a) Generating stations
b) Transmission or Main transmission lines
c) Sub-stations
d) Tie-lines
e) Load dispatch activities
f) Mains or distribution mains
g) Electric supply-lines
h) Overhead Lines
i) Service Lines
Contd…

7. ELECTRICAL DISTRIBUTION SYSTEM
A distribution system constitutes the part of electric power system
between the step-down distribution substation and the consumers’
service switches.
A distributed system is designed to supply continuous and reliable
power at the consumers’ terminal at minimum cost.
The transmitted electric power is stepped down in substations, for
primary for distribution purposes.
This stepped down electric power is fed to the distribution
transformer through primary distribution feeders which provides
power to individual consumer premises.

8. Factors Transmission System Distribution System
Topological Meshed Radial
Load Relatively balanced Unbalanced
Lines Transposed Non-transposed
Power Losses Low High
Fault Occurrence Less More

9. Fig. 1: A Radial Electrical Power Distribution System

10. The development in distribution network with the increase in demand, results
in power loss, voltage drop and unbalancing of load which has an adverse
effect on overall system operation.
With the advancement of computer controlled instruments at distribution side
system, serious issues regarding deteriorated power quality has been
increased.
The renewable energy sources (RES) integrated in the form of DG make it
worse.
Various type of compensating devices are used for the mitigation of these
problems. These devices include series APF, shunt APF and a combination of
both.

11. CUSTOM POWER DEVICES
The concept of Custom Power came into the picture after the advancement in power
electronic controllers.
This concept was first introduced by Hingorani in 1995.
The term custom power means employ power electronic controllers in distribution
system.
Just as FACTS improves the quality, reliability of transmission network by enhancing
power transfer and stability, the custom power enhances the quality as well as
reliability of the power which is being delivered to the consumers.

12. Custom power devices are classified into two categories:
1. Network Reconfiguration Type
2. Compensating Type
1) Network Reconfiguration Type Custom Power Devices :
• These devices are generally GTO or thyristor based switches and also known as
switchgears.

13. 2) Compensating Type Custom Power Devices:
These devices are generally used for load balancing, active and reactive
power control, mitigation of voltage sag and swell, VAR compensation,
attenuation of flicker, etc. applications.
The compensating devices generally consists series, shunt and hybrid
compensators.
These custom power devices are primarily designed for improving the power
quality at their point of installation not to improve quality of power of entire
system.

15. D-STATCOM
D-STATCOM stands for Distribution Static Synchronous Compensator.
D-STATCOM is a shunt compensator based on the synchronous machine
principles which is mostly used for reactive power compensation.
The term static indicates that it is based on solid state power electronic
switching devices with no moving or rotating components
A D-STATCOM is a fast-response, solid-state power controller that provides
power quality improvements at the point of connection to the utility
distribution feeder.

16. D-STATCOM also used to regulate the terminal voltage, suppress voltage
flicker, and improve voltage balance in three-phase systems.
It maintains bus voltage sags at the required level by supplying or receiving
reactive power in the distribution system.
One of the major factors in advancing the DSTATCOM technology is the
advent of fast, self-commutating solid-state devices.
It is the most important controller for distribution networks. It has been widely
used to precisely regulate the system voltage and/or for load compensation.
Contd…

17.  In the initial stages, BJTS and power MOSFETs have been used to
develop D-STATCOMS
 With the introduction of IGBTS. the DSTATCOM technology has got a
real boost and at present it is considered as an ideal solid-state device
for D-STATCOMS.
 The improved sensor technology, especially Hall effect current and
voltage sensors, has also contributed to the enhanced performance of
DSTATCOMS.
 The next breakthrough in DSTATCOM development has resulted from
the microelectronics (DSP, microprocessor, etc) revolution.
Contd…

18. Using the D-STATCOM, the reactive power compensation and
unbalanced current compensation are achieved in all the control
algorithms.
In addition, zero voltage regulation (ZVR) at PCC is also achieved
by modifying the control algorithm suitably.

19. BASIC CONFIGURATION OF D-STATCOM
Fig. 2: VSC- Based DSTATCOM

20. CLASSIFICATIONS OF D-STATCOM
D-STATCOMs can be classified based on the type of converter used, topology,
and the number of phases.
The converter used in the D-STATCOM can be either a current source converter
or a voltage source converter.
Different topologies of D-STATCOMs can be realized by using transformers and
various circuits of VSCs.
The third classification is based on the number of phases, namely, single-phase
two wire, three-phase three-wire, and three-phase four-wire systems.

21. REVIEW OF LITERATURE
Hingorani (1988) discussed on the role of power electronics in electric
utilities or role of power electronics in future power systems.
Teng and Chang (2002) presented a load-flow solution for unbalanced
radial distribution networks. They used the Jacobian matrix formation
algorithm to form the matrix in spite of old time-consuming approaches.
Their suggested technique could easily incorporate the distribution
equipment model. They compared the results obtained by the proposed
method with that of other existing best methods and found the proposed
technique suitable for enormous distribution setups.

22. • Ranjan et al. (2004) presented an algorithm for power-flow studies of
unbalanced radial distribution networks. They formed their algorithm by
using basic concepts of network analysis and mutual coupling between the
phases for making the network model. The key benefit of the planned
technique is that all the records are kept in the vector form. Their method
gave the results efficiently and fast, so that it could be used for various
power-flow study applications viz. reconfiguration of network and
SCADA.
• Jazebi et al. (2011) had first introduced the D-STATCOM allocation in the
distribution system for the sake of power loss minimization. They
suggested to place D-STATCOM after reconfiguration for the better power
loss minimization. Since the distribution system suffers from high X/R
ratio, the Gauss-Seidel method which was proposed by them for load flow
is not suitable for analysis.

23. Chang et al. (2018) proposed improvements in bidirectional power-flow
balancing and electric power quality of a microgrid with unbalanced
distributed generators and loads by using shunt compensators. They used
shunt compensator in a three-phase, radial-type microgrid with unbalanced
DGs and loads to achieve bidirectional power-flow balancing and improve
the electrical power quality.

24. MATERIALS AND METHODS
• Operating System: Windows 10 (version 1909 ),
• Windows Server 2019
• Tools: Mathworks MATLAB 2015a
• IEEE Standard 33 Bus System

25. LOAD FLOW ANALYSIS
 Load Flow studies are performed to know the steady state operating condition
of a power system.
In power system, powers are known quantities rather than currents. Thus the
equations used in load flow studies are in terms of power.
These power flow equations are non-linear and solved by iterative techniques.
Load Flow studies are used for planning, operation, economic scheduling and
exchange of power between utilities.

26. Hence, Load flow analysis is pre-requisite for many operational and planning
problems such as:
Network configuration: it includes load balancing, reduction of loss, service
restoration.
Volt-var control: voltage profile improvement and volt-var optimization are some
examples.
DG and capacitor placement: renewable integration, loss reduction and reactive power
management.
Regular placement and control setting.

27. But in the case of distribution network the X/R ratio is very poor.
Program designed for power systems generally assume X/R ratio as
high.
Therefore, the methods used in transmission system have some
shortcomings such as,
• GS method when used in distribution networks converges very slow.
• while the NR method has a high computation time.

28. DISTRIBUTION LOAD FLOW
The X/R (reactance to resistance) ratio in transmission network is very
high.
Due to this there will be decoupled effect, it means real power P depends
on angle of voltage (δ) and reactive power Q mainly depends on voltage
difference (ΔV).
Because of this decoupling effect Jacobian matrix of NR will be diagonal
dominating and because of this dominance, convergence will be fast.

29. The distribution systems are generally radial or weakly meshed networks.
Although there is a provision of tie-lines which make it more mesh, but in
operation we use them as radial only.
Moreover, in most of the cases the distribution systems are unbalanced and we
have to analysis unbalance system in most of the cases.
Therefore, due to restrictions or limitations of general load flow methods in
distribution networks, BFS method is used in the load flow analysis of
distribution network.
Backward Forward Sweep (BFS) method:

30. This method involves separating the main system into two separate systems and
solving one, with the help of the last result of the other.
This process will be continued until convergence is achieved.
Solving for the currents with the voltages given is called Backward sweep (BS).
Solving for the voltages with the currents given is known as Forward sweep (FS).
Contd...

31. • Algorithm for BFS Load Flow:
Draw single line diagram of the typical distribution network.
Prepare a data file.
Choose appropriate base quantities.
Convert all the quantities to per unit quantities.
Start the algorithm.

32. Step 1. Initialization of voltages: we will initialize voltages of all buses.
𝑽𝒋
(𝟎)
= 𝑽𝒔∠𝟎° 𝒇𝒐𝒓 𝒋 = 𝟐, 𝟑, … … … . . 𝒏
Step 2. Initialization of iteration count k=1.
Step 3. Calculate load currents for j= 2,3, ………n.
𝑰𝒋
𝒌
= 𝒄𝒐𝒏𝒋
𝑷𝑳𝒋 + 𝒋𝑸𝑳𝒋
𝑽𝒋
𝒌−𝟏
𝒇𝒐𝒓 𝒋 = 𝟐, 𝟑, … … … … … 𝒏
Step 4. Backward Sweep: calculating branch current.
𝐼𝑚𝑛= current flowing between branch m and n.
𝑰𝒎𝒏
𝒌
= 𝑰𝒏
(𝒌)
+ 𝜮(𝒂𝒍𝒍 𝒕𝒉𝒆 𝒄𝒖𝒓𝒓𝒆𝒏𝒕𝒔 𝒐𝒇 𝒃𝒓𝒂𝒏𝒄𝒉𝒆𝒔 𝒆𝒎𝒂𝒏𝒂𝒕𝒆𝒅 𝒇𝒓𝒐𝒎 𝒃𝒖𝒔 𝒏)

33. Step 5. Forward Sweep: calculate voltage at each bus.
𝑽𝒏
(𝒌)
= 𝑽𝒎
(𝒌)
− 𝒁𝒎𝒏𝑰𝒎𝒏
(𝒌)
𝒇𝒐𝒓 𝒏 = 𝟐, 𝟑, … … … . . 𝑵
Step 6. Calculate error: error at any 𝑗 𝑡ℎ bus in 𝑘𝑡ℎ iteration,
𝒆𝒋
(𝒌)
= 𝑽𝒋
(𝒌)
− 𝑽𝒋
(𝒌−𝟏)
𝒇𝒐𝒓 𝒋 = 𝟐, 𝟑, … . . 𝑵
Step 7. Find maximum error.
𝒆𝒎𝒂𝒙
(𝒌)
= 𝐦𝐚𝐱(𝒆𝟐
𝒌
, 𝒆𝟑
𝒌
, … … … . . 𝒆𝑵
𝒌
)
Step 8. Compare maximum error with the threshold value.
𝒊𝒇 𝒆𝒎𝒂𝒙
(𝒌)
≤ 𝜺
Print results.
Else, update iteration count, k=k+1 and then goto Step 3.

34. IEEE 33 Bus System
IEEE 33-Bus radial distribution system is
a standard bus system used for test and
comparing various types of DG units.
This bus system consists of 33 buses and
32 distribution lines..
Fig. : Single Line Diagram of IEEE 33-Bus
System

35. FORMULATION OF THE PROBLEM
Studies are performed on IEEE 33 bus standard distribution system.
Backward forward sweep load flow algorithm is used for the
calculations of voltage and current.
Objective Function,
Consider the change in voltage profile as a result of change of power
at the end node n,
∆𝑉𝑖
2
= 𝑉𝑖
′2
− 𝑉𝑖
2
∆𝑉𝑖
2
≥ ∆𝑉𝑖−1
2
≥ ⋯ ∆𝑉0
2
≥ 0
D-STATCOM Limits:
𝑄𝐷𝐶𝑂𝑀𝑚𝑖𝑛,𝑖
𝑘
≤ 𝑄𝐷𝐶𝑂𝑀,𝑖
𝑘
≤ 𝑄𝐷𝐶𝑂𝑀𝑚𝑎𝑥,𝑖
𝑘

36. Power Balance Constraints:
𝑃𝑖
𝑘
= 𝑃𝑔𝑖
𝑘
− 𝑃𝑑𝑖
𝑘
= 𝑉𝑖
𝑘
𝑗=1
𝑛
𝑉
𝑗
𝑘
(𝐺𝑖𝑗cos( 𝛿𝑖
𝑘
− 𝛿𝑗
𝑘
) + 𝐵𝑖𝑗 sin(𝛿𝑖
𝑘
𝛿𝑗
𝑘
))
𝑄𝑖
𝑘
= 𝑄𝑔𝑖
𝑘
− 𝑄𝑑𝑖
𝑘
= 𝑉𝑖
𝑘
𝑗=1
𝑛
𝑉
𝑗
𝑘
(𝐺𝑖𝑗sin(𝛿𝑖
𝑘
− 𝛿𝑗
𝑘
) + 𝐵𝑖𝑗 cos(𝛿𝑖
𝑘
𝛿𝑗
𝑘
))
Inequality constraints:
𝑃𝑔𝑖
𝑚𝑖𝑛
≤ 𝑃𝑔𝑖
𝑘
≤ 𝑃𝑔𝑖
𝑚𝑎𝑥
, i 𝜖 𝑆𝐺 𝑄𝑔𝑖
𝑚𝑖𝑛
≤ 𝑄𝑔𝑖
𝑘
≤ 𝑄𝑔𝑖
𝑚𝑎𝑥
, i 𝜖 𝑆𝐺

37. REFERENCES:
Chang, W. N., Chang, C. M., and Yen, S. K. 2018. Improvements in Bidirectional Power-Flow
Balancing and Electric Power Quality of a Microgrid with Unbalanced Distributed Generators
and Loads by Using Shunt Compensators. Energies, 11(12): 3305.
Hingorani, N. G. 1988. Power Electronics in Electric Utilities: Role of Power Electronics in
Future Power Systems, Proc. IEEE, 76(4): 481-482.
https://www.electrical4u.com/electrical-power-distribution-system-radial-ring-main-electrical-
power-distribution-system.
Jazebi, S., Hosseinian, S. and Vahidi, B. 2011. DSTATCOM Allocation in Distribution
Networks Considering Reconfiguration using Differential Evolution Algorithm. Energy
Convers. Manag., 52(7): 2777-2783.

38. Ranjan, R., Venkatesh, B., Chaturvedi, A., and Das, D. 2004. Power
Flow Solution of Three-Phase Unbalanced Radial Distribution Network.
Electr. Power Compon. Syst., 32(4): 421-433.
Teng, J. H. and Chang, C. Y. 2002. A Novel and Fast Three-Phase Load
Flow for Unbalanced Radial Distribution Systems. IEEE Trans. Power
Syst., 17(4): 1238–1244.

39. THANK
YOU