In this video, we look at developing
a simple grid forming control for remote AC microgrid
using Droop Control.
A microgrid is a type of power network
used to facilitate the incorporation
of renewable energy resources.
The AC microgrid in Simulink has been modeled
with [INAUDIBLE] blocks.
The DC Celsius here represents a [INAUDIBLE]
of typical renewable energy generation
systems such as PV arrays, wind turbines, or battery energy
storage systems.
The concept of microgrid is enabled
by controllers associated with power electronics interfaces
such as these inverters here, between the Celsius
and the network.
This is a natural step forward for mass works given
the controlled design solutions for power electronics systems
already in our products.
Along with inverters and DC celsius
there are three fixed loads consuming
175 kilowatts of AC power from the microgrid with a power
factor of 9.95.
There is also a switchable 75 kilowatt real power load
with a power factor of .98 that connects to the microgrid
through a circuit breaker.
A microgrids typically has a pre-planned load
shedding strategy to reach balanced operations.
Instant load shedding however, is
difficult to implement without a high level energy management
system.
This is where a simple trip controller
can help maintain AC micro-grids' frequency
and voltages around their nominal values.
Each of the inverter subsystems in this model
includes a Droop Controller to maintain a voltage of 380 volts
and a frequency of 60 Hertz.
In this droop controller design the active power frequency
coefficient is set to 2.5%, meaning
that microgrid frequency is allowed
to vary 1.5 Hertz around 60 Hertz with one per unit
change of real power injected from the inverter.
That reactive power voltage droop coefficient
is also set to 2.5%, meaning that the voltage
at each point of common coupling [? bus ?]
is allowed to vary over a range of 9.5 volts
or runs the nominal 380 volts with one per unit
change of reactive power.
The resulting frequency and voltage commands
are used to calculate the B and Q
axis reference voltages which are [INAUDIBLE]
of voltage control loop.
This PID controller regulates the voltages
through the generated three phase PWM switching sequences
fitting to the inverter.
Let us now run simulation and examine
how the droop controller performs
while abrupt 70 kilowatts load is brought up online.
This is the voltage scope of the connected inverters.
We can see that both inverters' voltages are maintained
around one per unit after the load switches on
at around 0.5 seconds.
Likewise, the micro-grid frequency
is also maintained at 60 Hertz.
Looking at the active and reactive power
scopes we see that the increased real and reactive power
loads are shared between both [? celsius ?]
without any high level supervisory control.
In summary, we saw how we can design a simple grid forming
controller with droop control for remote AC
microgrid using Simulink.
In future development from MathWorks
we are planning to demonstrate control strategies
to reconnect such microgrids back to the main grid.
We also plan to demonstrate more advanced grid
forming control technologies such as virtual power plants,
as well as other electrification topics such as stability
analysis workflow of power networks.