System dynamic models for hundreds of inverter-based generators are necessary to represent the whole behavior and to perform stability analysis at the transmission and distribution level in the electric power system. Some aggregated models, like DER_A and PVD1, have been suggested in the literature. However, these models include a considerable number of parameters, and so far, there is a lack of a formalized online method for parameterizing them. Several parameterization strategies for this particular model require the use of smooth functions. The parameters of these aggregated models may experience fluctuations and changes in the foreseeable future as the power system becomes more reliant on inverter-based generation. Consequently, an online parameter estimation will be necessary. This research proposes a way for parameter identification via online moving horizon estimation (MHE) for the grid voltage support function of the DER_A model by using a smooth mathematical representation. MATLAB/Simulink simulation shows that the proposed approach using MHE with a smooth representation of the DER_A model closely estimates the grid voltage support function parameters in the presence or absence of measurement noise. This study establishes the groundwork for the potential use in a detailed system including several inverter-based generators, with a primary focus on grid voltage support.

This paper presents a parametric comparative analysis between the virtual synchronous generator (VSG) method and the droop control method to emulate inertia in the voltage-source inverter (VSI). Droop controllers are commonly used to regulate sharing power in microgrids and distribute power generation proportionally among VSI’s depending on their rated power. Additionally, VSG has been used to regulate the Rate-of-Change-of-Frequency (RoCoF) of the microgrid using virtual inertia. Although both methods can be used to regulate the frequency variation, the influence of each method on the closed-loop eigenvalues is not the same. In this work, the transient response of the frequency is analyzed for each method to determine their advantages and disadvantages regarding frequency regulation in microgrid applications. The results were verified by conducting experimental trials using VSI’s. These experiments demonstrated that VSG is more suitable for regulating RoCoF and frequency nadir than droop controllers since it provides inertial support and improves frequency response.

This paper presents a design for a PR controller structure and explains in detail how to calculate their coefficients, for a Voltage Source Converter (VSC) operating in islanding mode. The design is developed in the discrete domain using a state-space model that includes a decoupling of the capacitor voltage technique and a cascade control structure. Moreover, the optimal values of the Proportional-Resonant controller coefficients are found based on the gain and phase margins. The validation of this design considers a 1 kVA VSC with PR controllers, simulation in MATLAB/Simulink, and experimental validation. This also presents a stability study of the proposed design.

This paper presents a voltage control design algorithm for a three-phase voltage source converter (VSC) connected to a linear load using a passive LCL filter. The controller is based on an optimal regulator, combined with the integral of the voltage error, which is called LQI that achieves null tracking of the error. The main objective of this paper is to present an algorithm to design a voltage controller through frequency analysis of the singular values of the system, the weight of the states involved in the system, the movement of the closed poles and their respective step response to evaluate performance and robustness against load changes. The simulation results show a satisfactory operation of the voltage controller with fast recovery after a resistive load change.

This paper presents a formal methodology for the analysis and design for discrete-time proportional-resonant classic (PR) controllers applied to a single-phase DC/AC converter using Sisotool/Matlab. This tool allows observing the response of the system before being simulated or experimentally implemented. Also, it allows to integrate and visualize the classical control theory requirements (overshoot, settling time, etc.) with the design of Proportional Resonant (PR) controllers. Simulations results demonstrate the effectiveness of the methodology presented for the design of PR controllers.

In this work, an optimal power sharing controller for a three-phase Inverter-based Generator (IG) in a synchronous d-q reference frame is presented. The optimization of this controller is computed using a Linear-Quadratic (LQ) tracking index that measures the tracking error. This approach has many advantages regarding to stability and robustness over classical Proportional-Integral (PI) or Proportional-Resonant (PR) controllers that use droop functions for power sharing. In addition, a comprehensive model that represents a grid-connected IG sharing power to the main grid is developed using the superposition principle. This model integrates the Voltage-Current (V-I) and power sharing dynamics in a single state space expression. To the best of our knowledge, although there have been approaches in V-I and power sharing control that improve microgrid stability and transient response, there are no formal methods that integrate both controllers as a single entity. The results of this method were compared against a known Proportional-Resonant controller that use droop functions for power sharing. Results show that the optimal power sharing controller improves transient response, improves power decoupling, and also reduces the quadratic cost associated with microgrid states and inputs.