This work proposes a modified high gain DC‐DC converter integrated with two boost converter stages, based on a boost cell and a Z‐source (ZS) cell with a switched capacitor (SC). The proposed converter architecture is simple, with a continuous input current and a wide range of input voltage fluctuation handling capabilities. It also provides a high voltage gain while minimizing voltage stress on semiconductor components. Because of the aforementioned characteristics, the proposed converter is suitable for combining with low‐voltage DC‐sources to high‐voltage DC bus in a variety of applications such as solar photovoltaic (SPV), fuel‐cell, and LED lighting. The operational principles, thermal modeling, steady‐state, and dynamic performance analysis are meticulously carried out on a 400 W laboratory prototype of the proposed converter. The converter's performance is carefully compared with similar existing topologies in terms of total device count and size, the voltage stress on power semiconductors, voltage gain, and peak efficiency. Furthermore, experimental findings show that a 12 V input is boosted to 98.8 V at a duty ratio of 0.3, demonstrating the efficacy of the proposed converter over a comparable structure.

A modified Z‐source switched‐capacitor based non‐isolated high gain DC‐DC converter for photovoltaic applications

Rogowski coils are key measurement instruments in several applications due to their flexibility, large bandwidth, linearity, and so on. Like the majority of the instrument transformers (ITs), Rogowski coils are standardized and their use is regulated almost for every application. This article focuses on a smart way for the equivalent parameters’ computation of the Rogowski coil. The parameter computation is performed by evaluating the Rogowski response when subjected to a single waveform generated to fulfill a specific requirement on its frequency content. Results demonstrate the equivalency of the presented method compared to the typical frequency sweep test. In addition, the results have been used to validate Rogowski’s output estimate procedure presented by the authors in a previous work.

A Smart Frequency Domain-Based Modeling Procedure of Rogowski Coil for Power Systems Applications

In this study, a single-phase single-stage grid-connected structure without transformer is presented. The proposed structure has the ability to boost the input voltage level without adding an extra dc-dc stage. In addition, being transformer-less makes it cost-efficient and small. Since in positive and negative half cycles there is a route for the capacitor to get charged, the capacitor has less volume compared with traditional topologies. It makes the inverter benefit from more power density. Peak Current Controller (PCC) has been used as the control system of the inverter to support powers (active and reactive) by providing modulation signals for the nine switches. The proposed converter is compared with similar solutions in a comparison table. Simulation results are demonstrated in order to validate the theoretical investigations.

A Single-Stage Transformer-less Five-Level Grid-Tied Inverter with Boosting Capability

Islanded microgrids are small networks that work independently from the main grid. The frequency and voltage in islanded microgrids are affected directly by the output power of distributed generators and power demand variations. In this work, a real-time driven primary regulation, which relies on optimized P-f droop coefficients, is proposed. In all operating conditions, it minimizes the power losses for islanded microgrids. The proposed configuration will allow the optimization modules to interact with each other and adjust parameters producing a suitable power sharing among generators. The methodology is tested based on a hardware-in-the-loop experimental set-up where distributed generators are connected to a group of loads. A parametric analysis is implemented for verification of the effectiveness of the proposed configuration as well as the improvement of the system reliability.

https://www.mdpi.com/1996-1073/13/2/451/pdf

Real-Time Minimization Power Losses by Driven Primary Regulation in Islanded Microgrids

The behaviour of a power transformer is complex and difficult to predict during transient conditions or during operation at frequencies below or above its nominal frequency, a phenomenon common in renewable energy plants due to harmonic distortion. Furthermore, the accuracy of a power system simulation depends on the models of critical subsystems such as the power transformers. This paper presents the use of a unique excitation waveform comprising of pseudo-random current impulses to accurately identify the wideband characteristics of a power transformer. By injecting the excitation waveform to the relevant transformer terminals, frequency responses are determined by cross-correlation of the perturbation signal, and the measured response. Compared to the traditional transformer identification methods, the pseudo-random current impulses offer a wideband excitation with a higher degree of controllability such that its spectral energy can be focused in the frequency band of interest. The proposed method was investigated on a 16 kVA, 22 kV/240 V single-phase transformer. The obtained wideband frequency responses provide useful information in harmonic penetration and over-voltage studies and are also used to estimate, with a high degree of accuracy, the lumped parameters of the equivalent transformer broadband circuit model.

https://ijpeds.iaescore.com/index.php/IJPEDS/article/download/21514/13587

Characterizing power transformer frequency responses using bipolar pseudo-random current impulses

A new dual-coupled inductor (CI) single-switch high step-up dc–dc topology featuring high power density is proposed in this study. Various capacitive power transfer methods, as well as inductive power transfer techniques, are utilized to act as a more efficient power interface between the input and the load. Three ports in the output terminal are employed to distribute the overall output voltage, diminish the voltage ripple in high-voltage gain ratios, and decrease the voltage stress on the port component. In the proposed converter, first, the voltage gain is high in lower duty cycles of the switching. Second, the stored energy of magnetizing and leakage inductances is recycled in both Cls. Third, the switch voltage spikes are alleviated. Fourth, the operation is done with no circulating current. Fifth, low-size passive components are presented. Sixth, high power density is obtained, and the voltage range is widened. Finally, a simple pulsewidth modulation (PWM) utilizing a wide control range is provided. In this study, the steady-state operation is analyzed under both continuous conduction mode (CCM) and discontinuous conduction mode (DCM), and the performance of the converter is evaluated using comparisons with similar works. In addition, the experimental results have been provided to justify the feasibility of the design.

/pdf/operation-and-design-consideration-of-an-ultrahigh-step-up-3mf6smvyo6.pdf

Operation and Design Consideration of an Ultrahigh Step-Up DC–DC Converter Featuring High Power Density

In this study, a new five-level common grounded grid-connected inverter is presented. In the proposed multilevel inverter, the charging and discharging process of the applied capacitors generate the output voltage waveform. Also, the proposed topology is based on neutral point clamped (NPC) topology. So, it can overcome the parasitic current issue in the photovoltaic (PV) system, which is the major problem in grid-tied PV applications. Additional significant features include-reduced filter size, lower total harmonic distortion (THD) of the injected current to the grid, and voltage boosting capability. The proposed grid-tied Inverter is based on Switched Capacitor (SC) cells in which the proposed structure is a five-level inverter which is capable of boosting the voltage with voltage gain of 1.5. Hence, in grid-tied applications, there is no need to an extra boost stage to make the output voltage peak value compatible with the highest amount of the grid voltage. The key point is that the boosting capability is obtained by a single input voltage source which makes the proposed structure compact and more efficient. Furthermore, the implemented capacitors are self-balanced and no control scheme is required to make a balance over their voltage. The feasibility of the proposed MLI has been simulated in MATLAB/Simulink environment.

Five-Level NPC Based Grid-Tied Inverter with Voltage Boosting Capability and Elimnated Leakage Current

High voltage gain DC-DC boost converters are used widely in grid-connected applications through integration with the Renewable Energy Sources (RESs). Photovoltaic (PV) arrays or Fuel Cells (FCs) generate a limited value of the DC voltages and then for high power and high voltage applications, at the first stage, these voltages should be increased. This study presents a high gain, single-switched, and efficient DC-DC boost converter using the switched-capacitor and switched-inductor cells. These blocks easily can enhance the voltage and present an input current with the less values of the ripples. This will be done through replacing the location of the input inductors and by applying a switched-inductor block. Magnetizing in parallel and demagnetizing in series for the inductors present the smaller input current stresses. A single switch is used for the proposed boost converter that directly decreases the complexity of the control circuit for obtaining a fixed DC voltage at the output side for flexible input voltages or loads. More voltages will be presented by the used switched-capacitor cell simply by adding several diodes and capacitors. A deep and detailed mathematical analysis will be presented for continuous (CCM) and discontinuous conduction modes (DCM) and a 200 W laboratory-scaled prototype is presented. The results of the hardware tests confirm the correctness of the theoretical analysis and simulation results.

https://ieeexplore.ieee.org/ielx7/6287639/9668973/09739700.pdf

A Novel and High-Gain Switched-Capacitor and Switched-Inductor-based DC/DC Boost Converter with Low Input Current Ripple and Mitigated Voltage Stresses

With the recent development in smart grid systems, there is now a growing interest in the development of on-line monitoring techniques. This is to reduce the maintenance costs as well as minimizing the probability of unexpected outages, or potentially to prevent catastrophic failures in the electrical network.

Saeed Rahimpour

Papers

Operation and Design Consideration of an Ultrahigh Step-Up DC–DC Converter Featuring High Power Density

Five-Level NPC Based Grid-Tied Inverter with Voltage Boosting Capability and Elimnated Leakage Current

A Novel and High-Gain Switched-Capacitor and Switched-Inductor-based DC/DC Boost Converter with Low Input Current Ripple and Mitigated Voltage Stresses

A Single-Stage Transformer-less Five-Level Grid-Tied Inverter with Boosting Capability

Online monitoring of power transformers using impulse frequency response analysis