Inverter Type Research Articles

Harmonics Forecasting of Wind and Solar Hybrid Model Driven by DFIG and PMSG Using ANN and ANFIS

Grid integration of Renewable Energy Systems (RES) involves various types of power electronics-based converters and inverters. The use of these electronic-based devices results in inducing both current and voltage harmonics to the grid. In order to reduce harmonics, especially for large-scale integration of RES, harmonic forecasting is one of many techniques used to design harmonic mitigation devices. The core objective of this work is to develop a novel forecasting model for accurate and reliable harmonic estimation for RES. To achieve this two hybrid generator models are used. First model consists of wind turbine coupled with Doubly Fed Induction Generator (DFIG) combined with Solar Photo Voltaic (PV) based power generator which are connected to common grid. The second model uses Permanent Magnet Synchronous Generator (PMSG) with wind turbine in conjunction with Solar-PV generator. With real world meteorological data (wind speed and solar irradiation) as inputs, these generators simulate and produce output power with current and voltage waveforms. Harmonics are extracted from these waveforms to record, analyze, arrange and forecast future harmonics. Three parameters namely, Total Harmonics Distortion (THD) and the dominant individual harmonic contents, 11 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> harmonic (h11) and 13 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> harmonic (h13) are forecasted for both voltage and current waveforms. Artificial Neural Networks (ANN) and Adaptive Neuro Fuzzy Inference Systems (ANFIS) are the prominent methods used for forecasting. Three types of three-layered ANN structures namely Cascaded Neural Network with Recurrent Local feedback (3LCRNNL), Cascaded Neural Network with Recurrent Global feedback (3LCRNNG) and Cascaded Neural Network with Local and Global feedback (CRNNGL) have been proposed and utilized in this work with hyperbolic tangent as transfer function to adjust weights and scaled conjugate gradient method as optimizer to reduce training error. ANFIS is also employed with subtractive clustering method to improve adaptability and accuracy of forecasts. The results are compared and presented which shows that ANFIS recorded the best performance for THDV and h13 and 3LCRNNGL for h11 for the Wind DFIG-PV model voltage harmonics forecast. For forecasts of the current harmonics, 3LCRNNGL performed best for THDI and h11, whereas ANFIS performed best for h13. For Wind PMSG-PV generator model, ANFIS yields the best results in every scenario involving voltage and current harmonics.

A Nine Level ANPC Boost Type Inverter Topology With Reduced Component Stress

A Nine Level ANPC Boost Type Inverter Topology With Reduced Component Stress

Artificial-Intelligence-Based Open-Circuit Fault Diagnosis in VSI-Fed PMSMs and a Novel Fault Recovery Method

Artificial intelligence (AI) techniques are widely used in fault diagnosis because they are superior in detection and prediction. The detection of faults in power systems containing electronic components is critical. The switch faults of the voltage source inverter (VSI) have a severe impact on the driving system. Short-circuit switches increase the thermal stress due to their fast and high stator currents. Additionally, open-circuit switches cause unstable motor operation. However, these issues are not sufficiently addressed or accurately predicted for VSI switch faults in the literature. Thus, this paper investigates the use of different AI classifiers for three-phase VSI fault diagnosis. Various AI methods are used, such as naïve Bayes, support vector machine (SVM), artificial neural network (ANN), and decision tree (DT) techniques. These methods are applied to a VSI-fed permanent magnet synchronous motor (PMSM) to detect the faults in the inverter switches. These methods use the drain–source voltage and PWM signals to decide whether the switch is healthy or unhealthy. In addition, they are compared in terms of their detection accuracy. In this regard, the comparative results show that the DT method has the highest accuracy as compared to other methods in the fault diagnosis process. Moreover, this paper proposes a novel and universal voltage compensation loop to compensate for the absence of the voltage portion due to the open switch fault. Thus, the driving system is assisted in operating under its normal operating conditions. The universal term is used because the proposed voltage compensation loop can be implemented in any type of inverter. To validate the results, the proposed system is implemented using two software programs, LTSPICE XVII-USA, WEKA 3.9-New Zealand.

Numerical study of higher-harmonic wave loads and runup on monopiles with and without ice-breaking cones based on a phase-inversion method

Ice-breaking cones are commonly used in the design of marine structures in cold regions. This study investigates the effects of higher-harmonic wave loads and wave runup on a 5-MW offshore wind turbine with and without ice-breaking cones under extreme wave conditions on the Liaodong Peninsula in China. Two ice-breaking cones (upward-downward and inverted types) are considered. The numerical model adopts a two-phase flow by solving unsteady Reynolds-averaged Navier-Stokes (URANS) equations using the volume of fluid (VOF) method. A phase decomposition method through a ‘Stokes-like’ formulation was adopted to obtain the parameters for each harmonics. The presence of the conical part is seen to increase the second-harmonic wave loads by up to 40%, but it has only limited influence on the fourth and fifth harmonics. The upward-downward-type ice-breaking cone increases the third harmonic, while the inverted-type ice-breaking cone decreases the third harmonic. Due to the phase difference between the first-harmonic and higher harmonics, the largest wave runup occurs at 0°, and 135° is the location with the smallest wave runup. This is because at the 135-degree location, the linear component is positive but the other nonlinear components are negative. For the 0-degree location, all harmonics are positive. By contrast, the inverted type has little effect. The high harmonic wave runup of the minimum point is backwards compared with that of the monopile, and most nonlinear wave runups are different upstream of the monopile.

A new protection algorithm for tackling the impact of fault‐resistance and cloud energy storage on coordination of recloser‐fuse protection

AbstractPresenting cloud energy storage system (CESS) in the landscape of storage devices exposes microgrids (MGs) to a substantial change. Employing a specific type of inverter namely synchronverter as the connecting interface for CESS gains high inertial response in MGs with high penetration level of inverter‐based distributed generations (IBDGs). However, high fault contribution of synchronverters can lead to challenging issues. Nevertheless, presence of fault resistance which results in malfunctioning of the recloser‐fuse pair intensifies the cruciality of the dilemma. In this paper, at the outset, the effects of contribution of synchronverter‐based CESS and also fault resistance on recloser‐fuse protection are explored and then, a new algorithm is proposed for tackling these bottlenecks. To overcome these hurdles, the conventional recloser‐fuse scheme is applied at first. Then, by using the obtained schemes for fast and slow operations of the recloser, a specific part of them is set in a manner that the fuse‐saving task is performed properly even when the synchronverter‐based CESS is deployed. On the other hand, the other part of the recloser scheme is altered in a way that the maloperation of the recloser‐fuse pair owing to the fault resistance is alleviated. Adequate numerical analyses are conducted to evaluate the proposed scheme.

Performance evaluation of grid-following and grid-forming inverters on frequency stability in low-inertia power systems by power hardware-in-the-loop testing

Developing advanced control functions for inverter-based resources (IBRs) to replace the inertial response of retiring synchronous generators (SGs) is progressing rapidly. Although various control mechanisms have been proposed for grid-following (GFL) inverters and grid-forming (GFM) inverters, the comprehensive comparison of their performance in contributing to grid stabilization based on hardware testings has not been studied well. This paper performs power hardware-in-the-loop (PHIL) testing for multiple inverter prototypes from different manufacturers and compares their performance concerning the difference in inverter types, control methods, and IBR penetration conditions in the power system. It also tests the possible interference between islanding detection methods (IDMs) and frequency control capabilities of GFL and GFM inverters.

Revisiting Grid-Forming and Grid-Following Inverters: A Duality Theory

Power electronic converters for integrating renewable energy resources into power systems can be divided into grid-forming and grid-following inverters. They possess certain similarities, but several important differences, which means that the relationship between them is quite subtle and sometimes obscure. In this article, a new perspective based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">duality</i> is proposed to create new insights. It successfully unifies the grid interfacing and synchronization characteristics of the two inverter types in a symmetric, elegant, and technology-neutral form. Analysis shows that the grid-forming and grid-following inverters are <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">duals</i> of each other in several ways including a) synchronization controllers: frequency droop control and phase-locked loop (PLL); b) grid-interfacing characteristics: current-following voltage-forming and voltage-following current-forming; c) swing characteristics: current-angle swing and voltage-angle swing; d) inner-loop controllers: output impedance shaping and output admittance shaping; and e) grid strength compatibility: strong-grid instability and weak-grid instability. The swing equations are also derived in dual form, which reveal the dynamic interaction between the grid strength, the synchronization controllers, and the inner-loop controllers. Insights are generated into cases of poor stability in both small-signal and transient/large-signal. The theoretical analysis and simulation results are used to illustrate cases for single-inverter systems, two-inverter systems, and multi-inverter networks.

A Dual-Frequency WPT Based on Multilayer Self-Decoupled Compact Coil and Dual CLCL Hybrid Compensation Topology

This article proposes a dual-frequency wireless power transfer (WPT) with dual <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLCL</i> hybrid compensation topology and multilayer self-decoupled compact coils (MLSDCCs). It extends the transmission distance corresponding to stable high transmission power and efficiency. Based on the parameter constraints of compensation capacitances and inductances, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CLCL</i> hybrid compensation topology realizes simultaneous resonance at fundamental and third harmonic frequencies. A typical inverter can meet the requirements of dual-frequency WPT without complex control or more number and improve the utilization rate of square voltage. According to interleaving and rotary stacking of unipolar and bipolar coils in MLSDCCs, the couplings between layers and unnecessary couplings of magnetic coupling mechanism (MCM) are eliminated. Only the main couplings for power transmission are retained and the volume of MCM is reduced. Finally, a 1 kW experimental platform is built. Compared with the typical single-frequency WPT, the maximum transmission power is increased by 2.8%, while the maximum transmission efficiency is only reduced by 0.53%. The main advantage is that the transmission distance corresponding to continuous high-power transmission (in the range of 95%–100% maximum receiving power) is increased by 2.75 times. When the lateral offset distance of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> -axis is one-sixth of the coil side length, the transmission efficiency decreases by only 1.47%.

Optimal LLC Inverter Design With SiC MOSFETs and Phase Shift Control for Induction Heating Applications

This article presents the analysis of a converter based on an LLC resonant output inverter and its optimal design used in induction heating applications. The new optimal design method improves several operating parameters that leads to an optimization of the dimensioning of the components of the converter. Additionally, this converter achieves an output power factor that can be considered optimal since it allows to minimize the reactive power of the resonant circuit components and reduces the rms values of the output current of the inverter and the current of its switching devices in relation to that found in traditional designs. A complete study of the circuit based on classic models is carried out to introduce simple rules for the design of this type of inverter for induction heating applications and to control its output power based on a phase shift (PS) system. Since the inverter is made with silicon carbide MOSFET transistors, an efficiency greater than 99% is reached. The experimental results were obtained from the test of a 12 kW 20 kHz converter for induction heating application.

A Simple Staircase Modulation for A Cascaded H-bridge Multilevel Inverter

This paper proposes a novel simple staircase modulation to obtain reasonable performance of an output voltage for a cascaded HBridgemultilevel inverter. The motivation of the proposed algorithm is that the inverter phase voltage intersects with an original sinusoidalwaveform at equal points in the y-axis. This modulation technique can calculate the independent switching angles more simply than thetraditional method, which employed Fourier’s series analysis, and can be applied to all kinds of multilevel inverters. In this paper, for the sake of validation, the technique was applied to a cascaded H-bridge inverter with unequal DC sources. Then, it was applied to the seventh, ninth, eleventh, and twenty-seventh levels of the multilevel inverter. In addition, pulse width modulation techniques used in this type of multilevel inverter are complicated. The PSIM software program was used for all simulation examples, and its results are consistent with the experimental results.

A DC Arc Fault Detection Method Based on AR Model for Photovoltaic Systems

DC arc faults are dangerous to photovoltaic (PV) systems and can cause serious electric fire hazards and property damage. Because the PV inverter works in a high−frequency pulse width modulation (PWM) control mode, the arc fault detection is prone to nuisance tripping due to PV inverter noises. An arc fault detection method based on the autoregressive (AR) model is proposed. A test platform collects the database of this research according to the UL1699B standard, in which three different types of PV inverters are taken into consideration to make it more generalized. The arc current can be considered a nonstationary random signal while the noise of the PV inverter is not. According to the difference in randomness features between an arc and the noise, a detection method based on the AR model is proposed. The Burg algorithm is used to determine model coefficients, while the Akaike Information Criterion (AIC) is applied to explore the best order of the proposed model. The correlation coefficient difference of the model coefficients plays a role as a criterion to identify if there is an arc fault. Moreover, a prototype circuit based on the TMS320F28033 MCU is built for algorithm verification. Test results show that the proposed algorithm can identify an arc fault without a false positive under different PV inverter conditions. The fault clearing time is between 60 ms to 80 ms, which can meet the requirement of 200 ms specified by the standard.

Decentralized Circulating Current Attenuation With Model Predictive Control for Distributed/Shunted Single/Three-Phase Grid-Tied Inverters

This letter proposed a decentralized control method to attenuate the circulating current among the grid-connected inverters without extra cost on the communication. Based on the combination of cascaded model predictive control (MPC) and modified <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCL$</tex-math></inline-formula> filter topologies, the developed method can locally limit the circulating current for different types of inverters, e.g., single/three-phase grid-connection, and various applications, e.g., shunted or distributed inverters with/without common dc bus, respectively. The merits of the proposed method include the following. 1) Decentralized circulating current control without the need of a central controller or the corresponding communication to collect the sampling and calculate the common mode components for leakage current attenuation among different inverters. 2) Generalized control method that can be applied to single/three-phase inverters for both shunted and distributed inverters with/without common dc bus applications. 3) No synchronization is needed for pulsewidth modulation signals among different inverters to attenuate the circulating current. 4) Cascaded MPC without the need of individual inverter’s grid side uncertain filter parameters for the attenuation of circulating current and system parametric modeling. 5) Better transient performance with the inner loop MPC. The experimental results verified the proposed method.

Overview of Recent Advanced Topologies for Transformerless Dual-Grounded Inverters

Transformerless inverters, most of which are H-bridge inverters, have been widely used and studied in grid-connected power systems in the last decades. However, the H-bridge inverter is affected by the low- and high-frequency common-mode voltage between the input and output terminals, resulting in a large common-mode leakage current. An alternative solution is to connect the ground of the input terminal to the output load or grid, that is, the dual-grounded inverter. In this case, the low- and high-frequency common-mode voltages can be mitigated or eliminated. As a matter of fact, scholars have made several research results on dual-grounded inverters. However, as of now, there is still no literature that comprehensively and systematically summarizes these research results. To fill this gap, this article classifies different types of dual-grounded inverters from the perspective of topology for the first time, and compares and summarizes their advantages and disadvantages. More than 60 works of literature have been reviewed to identify the practical implementation challenges and research opportunities in the application of dual-grounded inverters.

Research on the Voltage Spike Suppression Strategy for Three-Phase High Frequency Link Matrix-Type Inverter

The problem of high-voltage spikes on the secondary side of a high-frequency transformer (HFT) in the commutation process of a three-phase high-frequency link matrix-type inverter (HFLMI) is studied. Considering the parasitic capacitance of MOSFETs, the mechanism of voltage spikes during HFLMI commutation is revealed. According to the characteristics of the topology, the later stage matrix converter (MC) is decoupled into two groups of conventional three-phase voltage type inverters by the de-re-coupling idea, and the space vector pulsewidth modulation (SVPWM) is carried out, respectively. The zero vector is inserted between two nonzero voltage vectors to accomplish smooth commutation for addressing the problem of voltage overshoot on the secondary side of HFT due to the switching of HFT leakage inductance and filter inductance to the same path. Due to the existence of parasitic capacitance, the voltage spikes caused by its resonance with the system’s stray inductance cannot be solved by optimizing modulation strategies. In order to further suppress voltage spikes, a flyback clamp circuit is proposed to absorb the leakage inductance energy. Ultimately, a prototype with a rated power of 200 W is developed for experimental verification. The results show that the peak efficiency of three-phase HFLMI with the flyback clamp circuit is 92.6% in the full power range, the voltage spikes on the secondary side of HFT are clamped to about 1.2 times the rated voltage, and all switches realize soft-switching.

A Switched-Capacitor Multilevel Inverter Using Series-Parallel Conversion With Reduced Components

The switched-capacitor multilevel inverters (SCMLIs) are the popular type of multilevel inverter. This kind of inverter topology uses the on-off states of switches to control the charging and discharging of capacitors to achieve multilevel output. Most SCMLIs make use of an H-bridge structure to change the polarity of the output voltage, which cause the switches to withstand the peak of the output voltage. The H-bridge is replaced by two half-bridges on both sides of the proposed inverters, and the maximum voltage stress (MVS) on switches in half bridge is kept within 2Vdc, as well as in the extended structure. Therefore, the voltage stress of the switches is greatly reduced. In addition, the topology has a modular structure, which makes the expansion and modulation of the topology simple, while achieving a higher voltage gain. Moreover, with the growth of output levels, the MVS of the switches in the topology remains unchanged, which has good practical application scenarios. In this study, the correctness and feasibility of the topology have been verified by experiments.

Broadband absorber coupled with anti-reflection inverted pyramid type all-dielectric microstructure

In order to improve the absorption efficiency and absorption bandwidth, we propose an inverted pyramid type all-dielectric absorber. Using the anti-reflection interface characteristics of the inverted pyramid microstructure, the designed absorber can achieve 100% perfect absorption in the range of 1.5THz to 1.7THz. Based on the structural diffraction analysis and electromagnetic field distribution characteristics, we have deeply explored the physical mechanism of wave absorption of the designed structure, and revealed the dual physical mechanism of electromagnetic wave diffraction conversion and resonance absorption. Based on the unique wet etching technology, we have experimentally prepared this inverted pyramid type all-dielectric absorber. Through experimental measurement, the consistency of the theoretical design and experimental test was confirmed.

Smart Grid based Wireless Communication in 5G Network for Monitoring and Control Systems in Renewable Energy Management

Wireless networks are becoming ubiquitous and as the cost of equipment decreases and performance increases, it becomes both economically and technologically feasible to deploy wireless networks in power systems and industrial environments for a wide range of applications. They have advantage of providing diverse controlling features through a unified communication platform. Application of such networks in the smart grid/industrial environments is under active research and expected to become an integral part of the power system. This research propose novel technique smart grid communication in wireless 5G networks for monitoring and controlling management. Here the smart grid designing has been done based on wireless communication networks. The smart grid network for renewable energy has been controlled using Stackelberg equilibrium based SCADA (supervisory control and data acquisition) method. The control method based collected data has been monitored for detection of malicious activities in the network using supervised radial basis fuzzy systems. The experimental analysis has been carried out based on control system and network malicious activities. Here the control system based parameters analysed are Scalability of 65%, QoS of 71%, Power consumption of 41%, Network Efficiency of 92%. Then machine learning based malicious activities detection in terms of accuarcy of 96%, network security of 88%, throughput of 94%, Network delay of 41%. Proposed method supports interoperability of multiple types of inverters, is scalable and flexible, and transmits data over a secure communication channel.

Reduction of harmonics emission of a WECS in the electrical grid using multilevel inverters

&lt;span lang="EN-US"&gt;Wind energy conversion system (WECS) is composed of many non-linear power electronic sub systems, which contribute significantly in harmonic emissions that is a threat for the quality of electrical power. Hence, for a better integration of WECS in the electrical grid and in order to satisfy IEEE 519 standards, WECS must inject a quality power with a rate of total harmonics distortion (THD) that is less than 5%. Multilevel Inverters are an emerging solution for having a perfect sinusoidal output voltage with minimum harmonic content and lower switching losses than the two-level inverter so that only a smaller filter size is required. Thus, in this paper we are presenting a significantly improved results of the reduction of the grid injected current THD using three types of inverters (two-levels, three-levels NPC, and five-levels H-bridge cascade) for a WECS and comparing the THD performances of using each of the studied inverter. All results of THD are verified by a Fast Fourier transform simulation using MATLAB/Simulink. &lt;/span&gt;

Method for Deriving Transformerless Common-Ground Voltage Source Inverter Topologies

This article presents a method for generating a family of transformerless inverters with common ground, for the connection of photovoltaic or battery energy storage systems with the electrical grid. Using the proposed method, four common-ground buck type inverter topologies are derived from bidirectional dc–dc converters based on buck–boost, SEPIC, zeta and boost–buck converters, which have in common the static gain given by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${D \mathord{/ {\vphantom {D {(1 - D)}}} } {(1 - D)}}$</tex-math></inline-formula> . The operation of each generated topology is explained and confirmed by computer simulation results. A comparative analysis between the four generated topologies and other transformerless common-ground inverters are included, considering the number of components, voltage ratings, output power, switching frequency, reported efficiency at rated power, and the requirement for filter insertion. Experimental results obtained in the laboratory, with tests performed on a nonoptimized experimental prototype are presented, for the topology based on the bidirectional zeta converter.

A Comprehensive Review on Multilevel Inverters for Grid-Tied System Applications

Multi-level inverters (MLIs) have been widely used in recent years due to their various advantages in industrial and grid-connected applications. Traditional MLI topologies are being hampered by the rapid surge of renewable energy systems (RES) as a result of performance difficulties such as poor power reliability, an economically unviable structure, and a lack of efficiency. These difficulties are due to the traditional MLI topologies’ inability to keep up with the increasing demand for RES. Because of concerns about performance and limitations posed by classic MLI topologies, researchers have found themselves driven to the idea of building innovative hybrid MLI topologies. This study provides a comprehensive analysis of multilevel inverter systems that are wired into the main power supply. Grid-connected inverter types and their configurations are discussed in depth in this review. Diverse multi-level inverter topologies, as well as the different approaches, are divided into various categories and discussed in depth. Additionally, a number of control reference frames for inverters were brought forward for discussion. Furthermore, different inverter control strategies were investigated, followed by a tabular summary of recent developments in the inverter-related literature for the convenience of the readers. Moreover, the recently proposed grid-connected multi-level inverter systems were discussed including their findings and innovations. In conclusion, a brief description of the study’s scope was offered and research directions for future studies were provided.