Enhancement of microgrid application

1. Modelling and Control of a Microgrid
with100kW PV System and
Electrochemical Storage System
Under Guidance of Presented by
Prof. Amarnath Thakur Usman Thommangadan
2015PGEEPE111

2. outline
 Introduction
 Motivation and Objective
 Literature review
 Power electronics converters
 Power conditioning and Control
 Modelling, Simulation and result
 Conclusion
 References
2

3. 1. Introduction
3

4. Introduction
• For the solution of undesired power
quality problems such as voltage sags, swells,
interruptions, black-outs etc……
• New conceptual electrical power system
required. Which may integrate both conventional and non-
conventional energy sources.
• Several concepts proposed up to now
“FRIENDS”, “PREMIUM POWER PARK” and “MICROGRID”
4

5.  Among these approaches “MICROGRID” is the
most exhilarating because it challenges the
entire architecture that have been established
for electricity generation, transmission and
distribution over the past100 years.
5

6.  A group of interconnected loads and distributed
energy resources within clearly defined electrical
boundaries that acts as a single controllable entity
with respect to the grid.
 Enables local power generation for local loads.
 Comprises of various small power generating
sources that makes it highly flexible and efficient.
 It is connected to both the local generating units
and the utility grid thus preventing power outages.
6
Microgrid ?

7. Microgrid ?
 Excess power can be sold to the utility grid.
 Size of the Microgrid may range from housing estate to
municipal regions.
 Advantage of microgrid
 Efficiency
- Reduce fuel consumption.
- Supply close to demand minimise distribution loss
7

8.  Reliability
- Ensuring Power quality and reliability on site
- Optimally manage on site energy resources 24*7
 Energy security
- Ensure energy supply for critical load by utilising on site
generation
 Economic saving
- Reducing transmission line between source and load
- Peak load demand reduces
 Sustainability
- Reduction of carbon footprint by integrating cleaner fuel
resources
8

9. Microgrid – Applications
 Institutional Campus/Hospitals.
 Commercial/Industrial Complex.
 Remote “off grid” communities.
 Military Bases.
 Data Centre’s.
 Small Municipal Area.
9

10. 10
Generalised microgrid structure
Fig 1.1 Typical microgrid

11. Components of microgrid
 Distributed Generator (DG)
 Controller
 Energy storage systems(ES)
 Load
 Point of Common Coupling (PCC)
11

12. Microgrid operating mode
 Grid connected mode
-Microgrid connected to the utility grid and imports or exports
power from or to the utility grid.
12
Fig 1.2 Grid connected mode of Microgrid

13.  Stand-alone/islanded mode
-If any uncertainty happened on utility grid microgrid
switches over to stand-alone mode while still feeding power to
the critical load.
This can be achieved by either (i) disconnecting the entire microgrid by
opening CB4 or (ii) disconnecting feeder A and C by opening CB1 and CB3.
13
Fig 1.3 Islanded mode of Microgrid

14. Application of ESS
 Frequency regulation
 Cold start services.
 Contingency reserves.
 Energy services that shift generation from peak
to off-peak periods.
14

15. Need of ESS in microgrids
 Most renewable energy resources, such as wind and solar
energy, are intermittent in nature.
 Some of them are slow dynamic response like Fuel cell
 To ensure reliability require ESS
 ESS store energy at the time of surplus and redispatch it
when needed
15

16. Energy storage technologies
• Ultracapacitors.
• Superconducting magnetic ESS.
• Compressed air.
• Pumped hydro.
• Fly wheels.
• Electrochemical storage system (battery)s.
16

17. Motivation and Objectives
 To understand the complete model of microgrid, a
detailed study have to be carried out on microgrid
structure, its modelling and control.
 Modelling and simulation of PV system that
charges storage system as well as feeding the
excess power to the utility grid.
 Modelling and simulation of BESS which delivers
power to sensitive/critical load during islanded
mode.
 Realisation of load control program to ensure
stability during islanded mode when BESS feeds
sensitive/critical load.
17

18. 2. Literature review
18

19. Literature review
19
AUTHOR TITLE CONTENT
Blaabjerg, Frede, Zhe
Chen, and Soeren Baekhoej
Kjaer
Power electronics as
efficient interface in
dispersed power generation
systems." IEEE transactions
on power electronics vol
19, issue no. 5, 2004, pp:
1184-1194.
Describe solar cell
operation, peculiarity and
need of module, array and
panel
Kumar, Deepak
Modeling, simulation and
performance analysis of a grid-
tied voltage source inverter
based photovoltaic system
under balanced and non-linear
load conditions." (ICECCT),
2015 IEEE International
Conference on,. IEEE, 2015,
pp. 1-5
Describes photovoltaic
panel integration through
grid tied inverter
Hanley, Emma S., George
Amarandei, and Bartek A.
Glowacki
Potential of Redox Flow
Batteries and Hydrogen as
Integrated Storage for
Decentralized Energy
Systems." Energy &
Fuels vol 30, issue no.2,
2016 pp: 1477-1486.
Describe battery energy
storage system (BESS)
And its application

20. AUTHOR TITLE CONTENT
Ovshinsky, S. R., M. A.
Fetcenko, and J. RossToby
Considine
A Nickel Metal Hydride
Battery." The Science and
Technology of an American
Genius, 1993, pp: 214
Describes features of NiMH
battery and its application
S.M. Kaplan, F. Sissine
Smart grid: modernizing
electric power transmission
and distribution”. The
Capitol Net Inc, ISBN 1-
58733-162-4, page 217,
2009
Describe Inverter Control
Schemes with BESS
Ibrahim, Hussein, Adrian
Ilinca, and Jean Perron
Energy storage systems
characteristics and
comparisons." Renewable
and sustainable energy
reviews vol 12, issue no. 5 ,
2008: pp:1221-1250.
Load Control requirement
for BESS
20

21. 21
AUTHOR TITLE CONTENT
Chen, Haisheng, Thang
Ngoc Cong, Wei Yang,
Chunqing Tan, Yongliang
Li, and Yulong Ding
Progress in electrical
energy storage system: A
critical review”. Progress
in Natural Science vol 19,
issue no. 3, 2009,pp: 291-
312
Load shedding
requirement of BESS

22. Proposed Microgrid
22
PCC
Utility grid

23. For modelling proposed microgrid
 Include two part
The first part is to converts the input power to a
suitable output power
The second part, which controls the functioning
of the converters by monitoring the input /
output voltages and currents
23

24.  First part
With help of Power Electronic converters
 Second part
With help of Power conditioning and control
unit
24

25. 3.Power electronic converter
25

26. Power electronic converters
Power electronic converters can be used for the
designing in several areas:
 Power processing
 Computation
 Control system
 Automobile industries.
They can also be used in electronic circuitry to
control like
 Current and Voltage magnitude,
 Frequency
26

27. Evolution of PV Inverters
 Centralised inverter technology
PV modules connected in the form of string
to avoid further amplification
This strings are connected in parallel
 Limitations:
• Non flexible design
• Power loss due to centralised MPPT
• High voltage DC cable between PV module
and inverter
• Loss in the string diode
27
Fig 3.1 Centralised inverter technology

28.  String inverter technology
Several strings are interfaced with their
own DC–DC converter to a common
Inverter.
Advantage
Each string can be controlled
individually
Further enlargements are easy
Plug and play
Efficient and flexible
28Fig 3.2 String inverter technology

29.  PV AC Module
One large PV cell is connected to an Inverter.
 The main challenge to develop an inverter that can
amplify the very low voltage, 0.5 ~ 1.0 V and a power
of 100 W/m2, up to an appropriate level for the grid
with out losing efficiency.
 Entirely new converter concepts are required.
Proposed PV inverter technology
 String type inverter technology
 Because of simplicity and efficiency
29
Fig 3.3 PV AC module

30.  DC-DC converters
Buck and Boost converter
Using boost converter
If modulation index above 0.9
Difficult to track crossing point between modulating waveform
and carrier waveform
Taking this in consideration
Choose modulation index as 0.8
To produce 400Vrms line voltage require 562V peak value
= ma Vdc
3
2
=peak value of line voltage
From above equation VDC = 800V
30

31.  Solar panel open circuit voltage 440V
 So required boost converter which convert the unregulated DC input to a
controlled DC output at a desired voltage level.
 Boost converter designing
3.4 Boost converter: (a) Circuit diagram; (b)Wave forms
Using Faraday’s law for the boost inductor
Vs D T = Vo − Vs 1 − D T Vs=Vin=Source voltage, D= Duty ratio
Vo= Output voltage, T=Sampling time period
𝑀𝑣 =
𝑉𝑜
𝑉𝑠
=
1
1−𝐷
31

32. D = 1 −
Vs
Vo
= 1 −
440
800
= 0.45
Inductor value taken from the ripple current equation
∆iL =
Vin
2L
D T L = 0.85 mH
Capacitor value taken from ripple voltage equation
∆V =
V𝑜
2RC
D T C = 0.8 mF
Equations and figure are taken
 Prakash Madiwal1, Lakshmikant redy, “Performance and Evaluation of 5MW Grid
Connected Solar PV Plant at Shivanasamudra”, IJST Vol. 4 Issue 1, July 2014
32

33. Inverter
 There are three inverter topology
 Single phase half bridge
 Single phase Full bridge
 Three phase inverter
 Proposed Inverter
 Three phase inverter
 Because of its efficiency and harmonic reduction
It is realised with help of universal bridge functional
block available on MATLAB/SIMULINK. It controlled
with help of gate on that
33

34. Battery Energy storage system (BESS)
 BESS realised with help of library functional block
available on MATLAB/SIMULINK
 Same inverter using for BESS also for reducing no of
component
34

35. 4. Power conditioning and control
35

36.  Power conditioning unit is a key enabler to utilizing
renewables, storage and microgrids on a large scale
 Inverter interfacing PV system with the grid
involves two major tasks.
 One is to ensure that the PV system is operated at the
maximum power point (MPP).
 The other is to inject a sinusoidal Voltage and current into
the grid
 Load control is required to ensure stability when
BESS feeds the sensitive load during islanded mode
36

37. Maximum power point tracking (MPPT)
 Non-linear characteristics of PV arrays and dependence on
environmental conditions needs MPPT
 MPPT extracting maximum power from PV array
37
1 Constant Voltage (CV) Method. 6. Short-Current Pulse Method
2 Open Voltage (OV) Method. 7. Fuzzy Logic Open Voltage
(OV) Method.
3 Incremental Conductance (IC) Methods. 8. Sliding Mode Method.
4 Perturb and Observe (P&Oa and P&Ob)
Methods.
9. Artificial neural network
Method
5 Three Point Weight Comparison.

38.  P&O simple and robust to obtain the MPP.
 If two PV Panel have been connected in series with different solar
irradiance, inducing a local MPP and a global MPP. All the other
tested MPPT algorithms have failed to find the global MPP, but all
have been able to reach the local one.
Fig 4.1 Perturb and Observe Algorithm
 The algorithm P&O continuously increments or decrements the
reference current or voltage based on the value of the previous power
sample. The time complexity of this algorithm is very less but when
reaching very close to the MPP, it doesn’t step at the MPP and keeps on
perturbing in both the directions
38

39. 39
Fig 4.2 Flowchart of Perturb and Observe (P&O) MPPT

40. Fig 4.3 Perturb and Observe (P&O) MPPT integration to DC-DC boost converter
 PWM Grid connected inverter (GCI) Control
 Grid is invariably a rigid voltage source with very low
impedance, power flow from the inverter to the grid
reduces to become simply current flow control.
40

41.  Current control method advantages
 It ensure accurate current tracking and monitoring
 It guarantees overcurrent protection (peak current
projection) and overload protection.
 It reduces the transient period.
 It can provide compensation because of the load
parameter changes (resistance and /or inductance).
 It provides compensation at the DC link and AC
side voltage.
41

42. 42
Fig 4.4 Classification of current control methods

43.  Hysteresis control scheme is used
 Simplicity in implementation .
 It offers a fast response current loop
 Does not need knowledge of the load parameters and
switching frequencies
 Hysteresis current control
 It force the grid injected current to follows a reference current
Fig 4.5 (a) Hysteresis Current Controller Block Diagram (b) Hysteresis Current Controller
Operational Waveform 43

44. Fig 4.6(a)Basic principles of hysteresis current regulation
 The controller can be easily extended to a three-phase VSI using
an independent hysteresis controller for each phase leg as shown
Fig 4.6 (b) Conventional two-level level hysteresis current- controlled three- phase VSI44

45.  Grid synchronisation
 When Stand alone inverter going for grid synchronization
 Tracking of grid frequency required.
 Normally grid frequency is varying according to load
variations.
 Any mismatch on frequency may lead to generation of
unwanted circulating currents and may lead to damage of
electronic devices.
 phase-locked loop (PLL) is widely a preferred technique that
enables tracking the grid frequency.
45

46.  Filters
 To meet the power quality requirements. The presence of
harmonics at the output voltage attenuated by connecting a filter
between the inverter system and the load
 the size of the filter depends on the switching frequency chosen
for the inverter.
 At high speed switching frequency, the size of inverter is small
and at low speed frequency the size of inverter bulky
 LC filter
 L-filter achieves low attenuation of the inverter switching
components
 shunt element is needed to further attenuate the switching
frequency components
 low reactance on switching frequency, High impedance of control
frequency range 46

47.  Load shedding
Table 4.1Microgrid operating mode
 In mode IV, the micro-grid is islanding state
 Required power is larger than the maximum power of BESS, or
the battery is in a low state of charge (SOC).
 In order to maintain the system stability load shedding is required.
For that controlling program need
47

48. 48Flow chart for load shedding

49. 5. Modelling, simulation and result
49

50.  PV Panel and DC-DC Boost converter with MPPT
50
Fig 5.1 Simulink Library functional block of
solar panel
No of series connected cell = 500
Open circuit voltage = 440V
Short circuit current = 430 A
No of module in series = 40
No of module in parallel = 60
Fig 5.2Simulink model PV panel and DC-DC converter with MPPT

51.  Battery Energy Storage System (BESS) with Load controller
51
Battery type = Nickel-Metal-Hydride
Nominal Voltage = 220 V
Rated Capacity = 100 Ah
Initial State of Charge = 85%
Display Show
1. Charging Status
2. State of charge (SOC)
3. Terminal Voltage of battery
Fig 5.3 Simulink Library functional block of BESS along with load
control MATLAB code

52.  Inverter and LC Filter
52
Fig 5.4Simulink Library functional block universal bridge along LC filter

53.  Hysteresis Current Control and PLL
53
Fig 5.5 Simulink model of Hysteresis current control and PLL

54.  Complete MATLAB/SIMULINK model of proposed microgrid
54
Fig 5.6Complete MATLAB/ SIMULINK model of proposed microgrid

55.  Simulation and results
55
Fig 5.7 Irradiation (W/m2) as input to the solar panel
Fig 5.8 Simulation result of DC – DC boost converter output terminal voltage

56.  Charging of BESS
 Discharging of BESS
56
Fig 5.8 Simulation result of Charging status, SOC, Terminal voltage during charging
Fig 5.9 Simulation result of SOC, terminal voltage of BESS during discharging

57.  Output voltage across load
57
Fig 5.10 Simulation result of Voltage and Current wave form across load

58. Conclusion
58

59.  Main contribution
 The application of Battery Energy Storage System
(BESS) in the field of microgrid is for the dedicated
operation. i.e energy is storing during excess energy
generation by renewable resources and retrieval of the
energy during the period when PV not available.
 Load shedding importance was studied and it was
realised through load controller MATLAB program for
stable operation when BESS feeding sensitive load
59

60. 60
References

61. 61

62. 62

63. 63

64. 64

65. Thank you
65