In this paper, a neural network predictive controller is proposed to regulate the active and the reactive power delivered to the grid generated by a three-phase virtual inertia-based inverter. The concept of the conventional virtual synchronous generator (VSG) is discussed, and it is shown that when the inverter is connected to non-inductive grids, the conventional PI-based VSGs are unable to perform acceptable tracking. The concept of the neural network predictive controller is also discussed to replace the traditional VSGs. This replacement enables inverters to perform in both inductive and non-inductive grids. The simulation results confirm that a well-trained neural network predictive controller illustrates can adapt to any grid impedance angle, compared to the traditional PI-based virtual inertia controllers.

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Neural Network Predictive Controller for Grid-Connected Virtual Synchronous Generator

In this paper a neural network heuristic dynamic programing (HDP) is used for optimal control of the virtual inertia-based control of grid connected three-phase inverters. It is shown that the conventional virtual inertia controllers are not suited for non-inductive grids. A neural network-based controller is proposed to adapt to any impedance angle. Applying an adaptive dynamic programming controller instead of a supervised controlled method enables the system to adjust itself to different conditions. The proposed HDP consists of two subnetworks: critic network and action network. These networks can be trained during the same training cycle to decrease the training time. The simulation results confirm that the proposed neural network HDP controller performs better than the traditional direct-fed voltage and/or reactive power controllers in virtual inertia control schemes.

/pdf/heuristic-dynamic-programming-for-adaptive-virtual-1ufogg6vsw.pdf

Heuristic Dynamic Programming for Adaptive Virtual Synchronous Generators

The control and management of power demand and supply become very crucial due to the penetration of renewables in the electricity networks and energy demand increase in residential and commercial sectors. In this paper, a new approach is presented to bridge the gap between Demand-Side Management (DSM) and microgrid (MG) portfolio, sizing, and placement optimization. Although DSM helps customers to take advantage of recent developments in the utilization of Distributed Energy Resources (DERs) especially microgrids, a huge need for connecting DSM results to microgrid optimization is being felt. Consequently, we propose a novel model that integrates the DSM techniques and microgrid modules in a two-layer configuration. In the first layer, DSM is employed to minimize the electricity demand (e.g., heating and cooling loads) based on zone temperature set-point. Using the optimal load profile obtained from the first layer, all investment and operation costs of a microgrid are then optimized in the second layer. The presented model is based on the existing optimization platform developed by RU-LESS (Laboratory for Energy Smart Systems at Rutgers University) research group. As a demonstration, the developed model has been used to study the impact of smart HVAC control on microgrid compared to traditional HVAC control. The results show a noticeable reduction in the total annual energy consumption and the annual cost of microgrid

Techno-Economic Analysis and Optimization of a Microgrid Considering Demand-Side Management

Transformerless Photovoltaic (PV) grid-connected systems benefit from improved cost, size, weight, and efficiency compared to the isolated alternatives A drawback of the trasnsformerless PV inverters is the leakage current that flows through the parasitic capacitance formed between the PV cells and panel metal frame connected to the earth The leakage current increases the current harmonics injected into the utility grid, the radiated and conducted electromagnetic interference (EMI), and losses In this paper, a two-stage three-phase Filter-Clamped (FC) transformerless PV system is employed that reduces the leakage current and output current THD compared to the conventional three-phase inverters Unlike other transformerless PV inverters, the FC inverter does not require any additional component The FC transformerless PV inverter is analyzed mathematically and its excellence is compared to the conventional three-phase inverter through simulation results

Filter-Clamped Two-Level Three-Phase Transformerless Grid-Connected Photovoltaic Inverter for Leakage Current Reduction

High frequency transformers are an integral part of power electronics devices and their parasitic parameters influence the performance and efficiency of the overall system. In this paper, transformer leakage inductances and parasitic capacitances are analyzed using finite element method (FEM) for different structures and windings arrangements of high frequency transformers. Also, magnetic field, electric field, and voltage distribution within the transformer is simulated and analyzed. Six different high frequency transformers with toroidal, EE, and UU cores with different windings are investigated for a 400(V)/400(V), 8 kVA transformer operating at 10 kHz. Additionally, interleaved windings for EE core are simulated and results compared with previous outcomes. Analysis results will help categorize each structure, based on its balance between leakage inductances and series parasitic capacitance. This information can later be used for optimal selection of transformers as a function of their operating frequency and enable designers to compromise between various parameters in different applications, especially new fast switches such as SiC and GaN.

Analysis of Various Transformer Structures for High Frequency Isolation Applications

In this paper, a high frequency transformer with different conductors and winding arrangements, at presence of eddy currents and skin effect, is studied. By using different winding structures, and conductor types, such as circular, square shaped, and foil wires, the skin effect in the windings is studied and current density within the conductors at a high frequency of 20 MHz and a lower frequency of 20 kHz are investigated using finite element method (FEM) simulation. Moreover, magnetic field distribution in the transformers at 20 MHz is obtained and displayed. Also, magnetizing inductance, leakage inductance and AC winding resistance for all of the transformer types are found and compared, and frequency response for the transformers are obtained and shown. Lastly, based on the results, the skin effect increases the AC winding resistance and decreases the leakage inductance as the frequency increases. Furthermore, different winding arrangements, conductors, and transformer types show a wide range of parasitic and loss behavior, which enable the designers to compromise between various parameters in different applications, especially new fast switches such as SiC and GaN.

Mohamad Saleh Sanjarinia

Papers

Analysis of Various Transformer Structures for High Frequency Isolation Applications

Analysis of Skin Effect in High Frequency Isolation Transformers