A Multivariable Controller in Synchronous Frame Integrating Phase-Locked Loop to Enhance Performance of Three-Phase Grid-Connected Inverters in Weak Grids: Controller Design and Simulation Files

Citation Author(s):
New York Independent System Operator
Hoseini Zadeh
Submitted by:
Sushil Silwal
Last updated:
Wed, 04/06/2022 - 22:10
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These controller design and simulation files correspond to the paper "A Multivariable Controller in Synchronous Frame Integrating Phase-Locked Loop to Enhance Performance of Three-Phase Grid-connected Inverters in Weak Grids" which presents a new current controller in the synchronous reference frame and its associated design for enhancing the performance of three-phase grid-connected inverters, especially against weak-grid conditions. The existing controllers do not perform strongly during high-impedance grid conditions and lead to oscillations and instability issues due to the interactions between the synchronization and control units. The proposed controller addresses this issue by 1) deriving a linear model of the three-phase phase-locked loop (PLL), 2) integrating the PLL model into the current controller design, 3) using a multivariable control design for multi-input multioutput systems, and 4) designing the controller gains using optimal linear quadratic theory. The proposed controller has superior performance over a substantially wider range of weakgrid conditions compared to conventional controllers. Extensive simulation and experimental results are presented in order to validate and reveal the desirable performance of the proposedcontroller.


The authors have decided to share the controller design and simulation files alongside the paper so as to facilitate fellow researchers quickly replicate the study and speed up their own research. The simulation results presented in the paper are for two cases, 1) High power inverter rating, and 2) Low power inverter rating. The zipped supplementary files contain four Matlab live script files for designing controller gains for four cases, proposed and conventional controllers for low and high power scenarios.  The simulation files in the PSIM platform along with the parameter files for high and low power cases are also included in the supplementary files. Users should disable the unused controller, i.e disable the proposed controller while testing the conventional controller and vice-versa, while running the simulation. Users are also recommended to read the 'Simulation Results' section of the paper before running different real-power jumps and fault withstand capacity tests.

Funding Agency: 
National Science Foundation (NSF) grants under ECCS-EPCN Awards #1902791 and #1902787