1. Microgrid Control Architectures
Centralized v/s Distributed Control Systems

2. Centralized Control System: General Features

3. Centralized Control System
Advantages:
Guarantees performance
More efficient
Trusted control architecture; conventional

4. Centralized Control System
Disadvantages:
1. Ensuring reliability is a problem; failure of the master/central controller can be problematic
2. Scalability and expansion is a complicated task; limited by the I/O ports of master
3. System maintenance requires complete shutdown
4. Redundancy of master is very expensive (often); limited options for network redundancy
5. Debugging is difficult due to complex isolation of code blocks
6. Large hardware requirements, CPU+Memory

5. Centralized Control System: Control Method
V/f Control
Voltage/Frequency control method
The master controller’s role is to maintain a certain voltage and frequency for the microgrid; the local generators work in PQ mode----- they output a certain value of active and reactive power as commanded by the Microgrid Central Controller (MGCC)
Parameters monitored: Voltage, frequency, active power and reactive power of the bus

6. Centralized Control system

7. Distributed Control System: Peer to peer communication

12. Distributed Control System: General Features

13. Distributed Control System
Advantages:
1. The failure of one controller does not have a big impact as replacement capacity can be bought online immediately
Easily scalable and extendable
Because of independence and modularity, it is easier to develop updates
Communication redundancy can be easily achieved
Each node is autonomous yet a part of an integrated system
Maintenance of the system can be accomplished easily
Peer to peer communication systems based on Ethernet increase interoperability and compatibility with other standard protocols

14. Distributed Control System
Disadvantages:
Less efficient than centralized control
Guarantees robustness but not performance
Inherent network latency
Increases overall complexity

15. Distributed Control System: Control Method
Automatic/self-adjusting of parameters enabled by a unique control algorithm based on ‘Droop-control’.
f-P and V-Q Control:
The frequency and voltage of the microgrid is measured and a reference active and reactive power value is decided for the generators by their respective local controllers.
P-f and Q-V Control:
The active power P and reactive power Q of the distributed generators is communicated among each other by the ‘peers’. The data is fed to the control algorithm and ---it outputs a frequency and voltage value for the microgrid to operate at.
P = Active Power, Q = Reactive Power, f = Frequency. Peers = individual DERs o

16. PLL = Phase Locked Loop
P-f and V-Q Control

17. Distributed Control Architecture: Ethernet based network communication

18. Main Distribution Panel
ADP
STS
PDP
ADP = Auxiliary Distribution Panel; PDP = Process Distribution Panel; STS = Static Transfer Switch; STC = Steam Turbine Controller; BPC = Boiler Process Controller. Figure from: Shashank Vyas, Rajesh Kumar, “Sizing and strategic scheduling of distributed
generators in a smart microgrid for the indian pulp and paper industry,”
in Proc. India Smart Grid Week 2015, March 2015, pp. 287–292.
STC
1.608 MWe
1.616 MWt
KW AC
BPC