Design of a Generalized Control Algorithm for Parallel
Inverters for Smooth Microgrid Transition Operation
Abstract
In this project, control algorithm is developed to enable the DGs to operate in all three modes
(grid-forming, grid-feeding and grid-supporting) with a single control structure, facilitating the
seamless transition between the operating modes. This feature is obtained by designing the multiloop controller in the inverter control layer using inverse plant modeling techniques, so that the
dynamics of the inverter and the LC filter are fully compensated, virtually transforming the
controlled DG in the unity gain from the application layer perspective. Thus, effects of
disturbances associated with the mode transitions are thus fully eliminated. The effectiveness of
the proposed control algorithm is validated by numerical simulations and hardware-in-the-loop
experiments.
Existing method:
The existing method describes the control and management strategies of DGs are designed on the
basis of the operating conditions and objectives of the microgrid. In grid interactive AC
microgrid, DGs can operate in three different conditions: grid-forming mode, grid-feeding mode
and grid supporting mode [4]. The grid-forming mode refers to the islanded operation, where the
voltage magnitude and frequency of DGs are self-determined based on the droop characteristics.
Thus, the inverter, in this mode, acts as a voltage source to control the voltage and frequency [3][5], achieves stability, shares active and reactive power production with other DGs, in order to
feed the local load demand.
Proposed method:
The proposed method describes several approaches have been proposed for the application layer
to reduce the disturbance caused by frequency or phase jump during the transition of gridconnected and islanded operation, such presynchronization with grid voltage frequency, angle
and
magnitude
adaptivePLLmodified/augmenteddroop-basedcontroltechniquesandself-
synchronized synchnonverters.In particular, modified/augmented droop-based control techniques
Further Details Contact: A Vinay 9030333433, 08772261612
Email: takeoffstudentprojects@gmail.com | www.takeoffprojects.com
are an effective and favored strategy for microgrid seamless transition. In a double-loop droop
control is proposed with the inner loop mimicking the physical droop and an adaptive droop
control in the outer loop that can switch between both grid-connected and islanded mode by readjusting the frequency references. Similar to this approach, reference [24] proposed a doubleloop droop control strategy, and the smooth transition is achieved by readjusting the power droop
in the outer loop.
BLOCK DIAGRAM
Power circuit and control structure of the inverter control layer.
Advantages:
1. By connecting inverters in parallel the addition of load is easy.
2. The microgrid concept over a passive network with distributed generation provides
reliability to its ability to provide uninterrupted power supply when the main grid is lost.
3.
The grid-forming mode the inverter, in this mode, acts as a voltage source to control the
voltage and frequency achieves stability, shares active and reactive power production
with other DGs, in order to feed the local load demand.
Applications:
1. Voltage source inverters are applied for HVDC systems.
2. Control method is applied for the systems to reduce the disturbance caused by frequency
or phase jump during the transition of grid-connected and islanded operation.
Further Details Contact: A Vinay 9030333433, 08772261612
Email: takeoffstudentprojects@gmail.com | www.takeoffprojects.com