Robust three degrees of freedom based onH∞ controller of voltage/current loops for DG unit in micro grids

Abstract

This study proposes a cascaded voltage-current robust control strategy for a distributed generator (DG) in microgrids. The main objective of the proposed controller is to improve the performance and power quality of a DG by injecting simultaneously a good sinusoidal voltage/current to the different loads connected to the DG. The proposed cascaded voltage/ current controller consists of three degree-of-freedom controller, which is designed by using H∞ control theory based on mixed sensitivity specifications. The choices of appropriate weighting functions W t , W u , W y that satisfy the preset goals to get a robust controller and a transform to a standard H∞ control design problem based on pre-compensator, feedforward and feedback connections are presented. The 3DOF-controller is based on MATLAB R/SimPowerSystems and using RT-EVENTS-toolbox. The controller is evaluated under different scenarios: transient responses with a resistive local load, and loads disturbances in steady-state responses with resistive, resistive inductive, resistive capacitive, and non-linear loads. Simulation and experimental results of resulting waveforms from a DG unit are presented, it confirms the effectiveness of the proposed method in effectively rejecting perturbation and robustness to loads disturbances; both good reference tracking and good transient response, and finally significantly lead to a very low total harmonic distortion.

A Simple Self-Tuning Resonant Control Approach for Power Converters Connected to Micro-Grids With Distorted Voltage Conditions

“…Then, this data must be used to define N properly according to the digital board capabilities and the maximum grid frequency. Nevertheless, the total control algorithm is easy to implement and requires relatively little computational effort, as shown in Table I and the parameters can be found by using the guidelines shown in [14], [16]- [18], among others. Enlarging the maximum grid frequency beyond allows its implementation for many applications.…”

“…This controller has the advantage of reducing all the main harmonics, since it has several infinite gain frequencies. However, this control has slower dynamic behavior when compared with Resonant Control (RC), predictive control and other techniques, as stated in [14]. Meanwhile, in [4] a predictive control is employed for a variable frequency grid.…”

“…A detailed analysis about the model and control parameter design is made, and therefore, the procedure may be followed for any system that needs an RC. Optimal robust controllers are presented in [14][17] [18]. The main contribution of these works is to give a clear procedure for a desired type of response by employing optimization tools to choose the best parameters.…”

Control of distributed generation systems for microgrid applications: A technological review

“…However, the function bared for this is comparatively slow. Bouzid et al introduce three degree‐of‐freedom controller using the H‐∞ control based on mixed sensitivity specifications. The three DOF using H‐∞ controller have the selections of suitable three weighting functions having predefined events based on pre‐compensator, feedforward, and feedback independent connections make them more versatile and stable than standard H‐∞.…”

Non‐linear integral higher‐order sliding mode controller design for islanded operations of T‐type three‐phase inverter‐interfaced distributed energy resources

“…The existing literature presents different control strategies [19–24] to control both islanded single‐ and three‐phase inverters. These strategies include the interconnection and damping assignment passivity‐based controller (IDA‐PBC) [19], model predictive control (MPC) [20], H three degrees of freedom (H‐3DOF) controller [21], deadbeat controller [22], modified linear active disturbance rejection control (MLADRC) [23], and unbalanced synchronous reference frame (USRF) controller [24]. These controllers are robust against uncertainties and have lower THDs while meeting the standard requirements.…”