Three-Phase Grid-Connected Inverters Equipped with Nonlinear Current- Limiting Control

Abstract

Voltage source inverters are essential devices to integrate renewable energy sources to the main grid and control the injection of real and reactive power. Due to their inherent nonlinear dynamics, the stability and particularly the current limitation of power controlled inverters represent challenging tasks under grid variations or unrealistic power demands. In this paper, using the synchronously rotating dq transformation, a nonlinear current limiting controller is proposed for threephase inverters connected to the grid through an LCL filter. The proposed controller introduces a cascaded control structure with inner current and voltage control loops and an outer power controller that includes a droop function to support the grid and rigorously guarantee a limit for the grid currents. Using nonlinear closed-loop system analysis and based on input-to-state stability theory, the limits for the d-and q-axis grid currents are proven independently from each other without adding any saturation units into the system that can lead to instability. Extensive simulation results of the proposed nonlinear currentlimiting controller are provided to demonstrate its effectiveness and current-limiting property.

Machine Learning-Based Monitoring of DC-DC Converters in Photovoltaic Applications

“…In this case, the errors calculated for each sample belonging to the dataset are saved in a specific matrix without correcting the complex weights. When all samples have been processed, this matrix presents N S rows, as shown in (13). Since the number of samples is greater than the number of weights, an oversized system of equations is obtained, and different techniques can be applied, such as Q-R decomposition and Singular Value Decomposition (SVD), reducing the number of iterations required for the calculation of the corrections.…”

“…For this reason, the development of new algorithms capable of predicting production from renewable sources and managing electrical loads will be a very important field of interest for many researchers [10][11][12]. Furthermore, the development and control of devices used as an interface between generators and the grid, or generators and other devices, play a fundamental role in the correct distribution of energy [13][14][15][16][17]. In this sense, the control of DC-DC converters represents a very important aspect because they can be used as an interface with renewable energy systems producing a Direct Current (DC) and are essential for all those systems powered by batteries, such as electric vehicles.…”

Voltage Support under Grid Faults with Inherent Current Limitation for Three-Phase Droop-Controlled Inverters

“…Opposed to the work presented in [15,38], here the proposed design enables the adaptation of the controller parameters E + max and E − max , and the controller states are attracted on any ellipse E with varying horizontal radius (E + max or E − max ) as analytically proven in Section 3.2. The positive sequence maximum current is set as the amplitude and not the RMS value in order to allow P, Q ∈ [0, S + max ] for the FRT.…”

Optimized control of three-phase inverters to minimize total harmonic distortion in a grid-connected photovoltaic system

“…Therefore, precise monitoring of the mains voltage vector by a PLL system is necessary to guarantee the proper functioning of our control method [24], [25]. After improving and comparing the various controls of the single-phase inverter [26], [27], this part of the ordered object is about a three-phase PV inverter and a new control method with SVPWM and SPWM control. The latter allows indirect control of currents drawn from the grid by converting these inverter currents into active and reactive powers using three-phase systems.…”