Input DC Source Research Articles

Inverter Topology Selection for Photovoltaic Power Systems

This article is devoted to the task of selection of photovoltaic power system inverter that would comprehend to all of the demands that could be applied to it. The challenge of creating efficient and reliable converter for the renewable energy systems that implies solar panels as primary energy sources is well-known since the first day of their existence as a possible choice for the role of the only power source in the system. The great breakthrough in the field of photovoltaic power system converters design was achieved in late 80’s-early 90’s years of the 20th century due to the several positive circumstances that included rapid evolution of the semiconductor industry at whole which sums up in the development of a new generation of power switches that was capable to operate in higher voltage and current ranges which was unreachable for the prior generation switches and new microcontrollers that was able to maintain more complex control algorithms than ones that were used before which in general resulted in significant downsizing of the resulting device and made it possible to practically develop power inverters with complex topologies that was considered over sophisticated and unreliable before. These factors leaded to the development of numerous new topologies with the main goal of transformation losses reduction and power efficiency increase. The desired result was obtained either thru the fulfilling the demands invoked by the photovoltaic sources operation features (z-source topologies) or power system topology features and reduction of output voltage THD ratio (multilevel inverters). But consideration of only one type of factors has not allowed achieving the maximum result in power losses task. Thus solution of the determined task should be started from complete identification and broad consideration of the main factors that define set of demands that converter has to face. In this article parameters of THD ratio of the inverter’s output voltage, photovoltaic source’s operation features and power system topology specifics were considered as the most valuable parameters that affects the power conversion losses values and was discovered in details based on a survey of the existing publications in the field of the study, international and local standards of consumer voltage quality parameters and practical results of the most popular and widespread topologies simulation in order to obtain an output voltage THD ratio. The achieved results demonstrate that inverter topology that would be able to satisfy all of the requirements has to have modular structure to be able to maintain the proper THD ratio and connect to the most popular types of the photovoltaic power system topologies and be based on the z-source topologies to imply the photovoltaic sources operation features. Therefore as a conclusion a cascaded multilevel inverter with a separated input DC sources topology that is based on quasi-z-source modules was recommended as a solution that could also be used as a base for the further power converter development.

Transformerless three-phase Z-source four-wire voltage source inverter-fed grid-connected PV system

A transformerless three-phase Z-source four-wire Voltage Source Inverter (VSI)-fed grid-connected photovoltaic system is implemented and controlled using the 3D-Space Vector Modulation (3D-SVM) technique. Generally, the leakage current problem is the main disadvantage of the transformerless inverter system, which is controlled and reduced using the proposed 3D-SVM method. The cause for leakage in the current problem is common mode voltage, which leads to affect the performance inverter and increases the total harmonic distortion (THD) in the system. This proposed system obtains the dc input source from the photovoltaic system and maximum power is tracked using the maximum power point tracking (MPPT – P & O) method and the output of VSI inverter is connected with the grid-connected system through a coupled inductor. In the proposed transformerless Z-source inverter, the THD and leakage current of the system are minimised. The simulation and hardware results are verified using matlab/simulink and DSP processor, respectively.

Optimal Conversion of DC-DC Converter Considered Optimal Switching Time and Optimal Switching Mode of PWM by Fuzzy based PID Tuning

This paper deals with design method of fuzzy controller for improving efficiency of DC-DC power converter. To design optimal control by fuzzy, this paper introduces optimal switching time and optimal switching mode of PWM. DC-DC Power converter is one of energy conversion device to transfer DC input source to DC output. When they transfer DC to DC, they have been using PID controller or fuzzy controller. Therefore, the efficiency of DC conversion strongly depends on PID parameter. Some papers illustrate tuning method of PID controller for this but have not been mentioning about the switching time and switching mode that can influence on the efficiency of DC-DC conversion. This paper suggests effective DC-DC conversion method by means of introducing switching time and switching mode into fuzzy based PID tuning.

Cross Connected Compact Switched-Capacitor Multilevel Inverter (C3-SCMLI) Topology With Reduced Switch Count

In this brief, a new cross-connected compact switched capacitor (C3SC) cell is introduced for multilevel inverter applications. The proposed CCS cell uses four switches and two diodes for interconnecting the input dc source and floating capacitors (FCs). A nine-level inverter is derived with the proposed C2SC cell requiring only ten switches and two FCs. The proposed C3SC cell-based MLI is self-balancing and has a voltage gain of two. All the switches of the proposed topology have a maximum blocking voltage within the input dc voltage ( v $_{in}$ ) value. The operating principle is detailed, and a simple logic gate based gate pulse generation scheme is presented. Detailed simulations and experimental results obtained from an 850 W prototype with several test cases are presented to validate the operation of the proposed topology. Finally, a detailed comparative assessment is performed with other recent SCMLIs to demonstrate the merits and superiority of the proposed topology.

Transformerless UPS System Based on the Half-Bridge Hybrid Switched-Capacitor Operating as AC–DC and DC–DC Converter

A single-phase transformerless online uninterruptible power supply (UPS) is proposed in this article. This UPS is based on the new half-bridge doubler-boost with switched-capacitor operation. It is capable of operating with ac and dc input sources. The proposed converter provides a high power factor and improves power efficiency for line voltage applications. The switched capacitor concept allows a natural balance of the dc bus capacitor voltages, both in the ac–dc mode and the dc–dc mode. It presents a common point between the line voltage source, load, and batteries. This characteristic makes it possible to eliminate the common mode current, reducing problems with electromagnetic interferences and allowing the use of a simple bypass system. The feasibility of the proposed UPS is verified by experimental results from a 2.5-kW prototype with an efficiency of up to 94.9% and unity power factor.

Fuzzy based optimal switching angle-PWM controller for 27-level asymmetric multi-level inverter

This work aims to improve the operation of multi-level inverter with reduced switching losses, thereby propose a new structure for an MLI with a reduced component count. A 27-level asymmetric Multi Level Inverter (MLI) with a minimal number of static switches is considered as a test system. The proposed MLI is developed with three input DC sources and thirteen power electronic switches. The hardware prototype is developed for 40 V and 3.5 A output. The control logic is developed in dsPIC30F410 controller. The main objective of this work is to effectively bring down the Total Harmonic Distortion (THD) of the resulting output voltage by analyzing the harmonic spectrum of the proposed MLI configuration with various low frequencies switching techniques and optimizing their switching angles and to choose an appropriate switching state using fuzzy logic controller (FLC). The proposed FLC covers wide range of operating conditions i.e. 10 switching states and variables 9*9 rules to predict the suitable switching angel. The performance metrics of the proposed structure of 27-level MLI has been evaluated upon simulation results and experimental results based on hardware prototype. The comparative study also carried out with the recent MLI topologies.

Single-phase thirteen-level dual-boost inverter based shunt active power filter control using resonant and fuzzy logic controllers

This paper address the power quality improvement of a single-phase utility grid using Thirteen-Level Dual-Boost Inverter (TLDBI) — Shunt Active Filter (SAF). The TLDBI uses a single DC source of low voltage magnitude and five switched capacitor arrangement to achieve self-balanced thirteen level output voltages. Moreover, the charging and voltage balancing of capacitor is achieved by proper switching sequence control in a series, through which boosted inverter output voltage levels are obtained. Compare with the tradional H-bridge Multilevel inverters (MLIs), all the elements in the proposed TLDBI are able to withstand a voltage stress which is equal to the input dc source. This feature ensures the performance of the proposed TLDBI in high-frequency applications. The power at the electrical grid is highly affected by wide range of non-linear loads. The proposed SAF is used to measuring and controlling the current flow from source to load. The difference between the targeted and actual currents from the utility grid is measured by using the modified Synchronous Reference Frame (SRF) theory. The estimated error current is used by the controllers to predict the optimum suitable switching angle and Modulation Index (MI) to the TLDBI-SAF. In this work, the traditional Proportional-Integral (PI) controller, Fuzzy Logic Controller (FLC) and Proportional Resonant Controller (PRC) are compared and the results are presented to validate the performance of SAF. The stability and robustness of the proposed controller is evaluated using Bode, Root locus, and Nyquist plots. The modeling and analysis of the proposed system are done using MATLAB/Simulink environments. The simulation results are presented in the various MI of TLDBI and also subjected to non-linear load conditions. The results are also compared to the claim novelty of the proposed work.

Interleaved Current-Fed Switched Inverter

Current-fed switched inverter (CFSI) is a high-gain inverter topology suitable for applications which have limited input dc source voltage, e.g., roof-top solar applications. A very high step-up ratio between ac output and dc input along with inherent shoot-through protection makes it suitable for low-power stand-alone inverter applications. In this article, a novel interleaved topology for CFSI (ICFSI) is proposed to augment its power rating. A pulsewidth modulation (PWM) scheme is also proposed to drive the interleaved topology. Various modes of operation of ICFSI, along with the steady-state model and dynamic analysis, with the proposed PWM scheme, are reported. ICFSI, with the PWM scheme, results in a 33% increase in maximum ac gain as compared to CFSI. In this article, the small-signal model of ICFSI is also derived and verified. An analysis comparing the losses in CFSI and ICFSI is carried out. It is observed that interleaved operation improves the efficiency by 4% at 600 W. The proposed topology and analysis are verified with the experimental results obtained from a 600-W laboratory-developed prototype.

An Approach to Mitigate Line Frequency Harmonics in a Single-Phase PV-Microinverter System

Single-phase microinverters used in household applications draw pulsating power from its input dc source while delivering ac power output to loads. While this introduces double line frequency harmonics into the dc bus of the microinverters, which lead to poor operational efficiencies of input energy sources (like solar arrays and fuel-cells etc.), it also deteriorates the quality of power fed to ac loads. Traditionally, large electrolytic capacitors or auxiliary decoupling circuits are used to mitigate the above-mentioned problems, making the converter system heavy, bulky, and thus increases the cost. In this letter, a new approach based on a simple pulsewidth modulation is proposed for single-phase microinverter system, aimed at mitigating the ill effects of double line frequency harmonics on both the dc side and ac side of the inverter. It is shown that by allowing a voltage swing of about 20% on the dc bus can significantly bring down the capacitance requirement by a factor of 3 to 5. Thus enabling, smaller and more durable film capacitors to be deployed instead of the bulky electrolytic capacitors. The envisaged approach is simulated and experimentally validated to support the claims on a laboratory setup.

Nine‐level voltage‐doubler bi‐polar module for multilevel DC to AC power conversion

A major disadvantage of two-stage topologies of switched capacitors based multilevel inverters is the use of H-bridge switches which endure high peak-inverse-voltage (PIV). In such topologies, the H-bridge stage is preceded by a level-generation stage which synthesises unipolar voltage levels. In this work, a bi-polar module is proposed which can synthesise nine levels at the AC terminals with a single DC input. The proposed module uses power switches with PIV equal to that of the input DC source. Use of switched capacitors in each of the proposed module enables a voltage gain of two. Such bi-polar voltage-doubler modules can be easily connected in a cascaded fashion to increase the number of levels, without involving H-bridge switches. Working modes of the module ensure that the capacitors are self-balanced. A complete analysis of the proposed module is presented. Also, experimental results are presented for validation. In addition, a comparison with other topologies has been presented.

Improved Switched-Capacitor Integrated Multilevel Inverter With a DC Source String

The integration of switched-capacitor techniques into multilevel inverters (MLIs) with a dc source string contributes to the boosting of voltage gain, renders it particularly attractive in reducing the number of input dc sources in the series string. However, the recent two-stage MLI topologies suffer from high voltage stress across the backend H-bridge. Addressing this concern, an improved topology, namely the one-switched-capacitor integrated MLI (1SCI-MLI) is proposed in this paper. An extended topology of 1SC-MLI is also established by appropriate incorporation of another switched-capacitor circuit. The two proposed topologies are endowed with voltage boosting capability. They also feature low switch count and low number of dc sources. More importantly, they resolve the high voltage stress problem in the existing counterparts. Their corresponding operational analysis and comparisons with recent MLI topologies are discussed. Simulation and experimental results from a laboratory prototype are presented to validate the effectiveness of the proposed topologies.

Hardware Implementation of an Enhanced Seven Level H Bridge Inverter with Reduced Switch Configuration

There are various boundaries in extracting power through Renewable energy sources. To reduce the insufficiency and high power demand we need to look up power extracting Techniques. To take out power through divergent sustainable power source assets for example solar energy, Photo Voltaic cell, Wind energy, Multilevel inverter is used .It orchestrates the preferred ac production from a number of dc input sources. The primary focal point of the paper is develop the productivity of level inverter and get better the nature of yield voltage by way of diminish number of power electronic switches. Here MOSFETs are used as switches. In this Paper, Simulation along with hardware design of 7-level cascaded Multi-level inverter and reduced switch multilevel inverter are presented.

Design and Implementation of Multi Input Hybrid Solar Three Levels Converter Using IOT

Multi input converters are highly reliable and can be effectively used for hybrid systems. Here the performance of a dual input system is experimentally verified by powering it with a solar and a battery and the whole system is monitored using IOT. A DC to DC converter which can operate with two sources is designed to operate with two input DC sources and the output DC supply is converted to AC by an inverter module. Power IOT based monitoring system is the main scope of this project which is achieved using an ESP8266 Arduino core and GSM technique. High conversion efficiency, soft switching realization and simple architecture are achieved in this system. The simulation results is presented under various values of operating conditions. A scale down model was developed which is powered by a 3Wp solar panel and a 12 V battery. The performance of the system was verified with various input conditions and the system parameters were monitored using IOT and the data samples were obtained.

Three-Phase Symmetric Cascading Z-Source Seven Levels Multilevel Inverter Excited by Multi Carrier Sinusoidal Pulse Width Modulation Scheme

The Multilevel Z sources Inverter have been documented as attractive topologies used for elevated voltage adaptation. As the digit of levels improved, the synthesized set of steps output waveform have many ladder, imminent the preferred sine waveform but the major weakness of MLI be its amplitude of ac output voltage is imperfect to DC input sources voltage summing up. To conquer this drawback seven level cascading symmetric multilevel inverter based Z source inverter have been projected. This work focuses on different multi-carrier sinusoidal PWM scheme for the seven level three phase Z source symmetric cascading inverter. Performance parameters of seven level three phase Z source symmetric cascading inverter has been analyzed. A simulation circuit model of seven level three phase Z source symmetric cascading inverter urbanized using MATLAB/SIMULINK and its presentation have been urbanized.

A New Coupled Inductor Nonisolated High Step-Up Quasi Z-Source DC–DC Converter

In this article, a new nonisolated high step-up quasi Z-source (QZS) dc–dc converter with coupled inductor techniques is presented, which is suitable for renewable applications. The main advantages of the proposed topology are continuous input current, common ground between load and input dc source, low normalized voltage stress on the semiconductors (switch/diodes), and low total voltage stress on devices compared to the conventional QZS converter. However, increasing the turns ratio value of the coupled inductor windings not only limit the duty cycle but also leads to decrease the voltage stress on switch/diodes and increase the output voltage level. The operating performance of the proposed converter, theoretical analysis and comparison between the proposed converter and other published works (i.e., QZS converters) are provided. Finally, one prototype at 500 W is built and tested, which shows experimental results and theoretical analysis verify each other well.

Adaptive SMC for the Second-Order Harmonic Ripple Mitigation: A Solution for the Micro-Inverter Applications

There have been several advanced topologies proposed by the community for micro-inverter applications. However, many such applications suffer from unwanted second-order harmonic current ripple at dc input. Moreover, in the absence of suitable passive filter or ripple compensator, the second-order harmonics ripple may propagate into the dc source. This results in several problems to the system, related to system efficiency, life, cost, size, reliability, and stability. This paper proposes an adaptive sliding-mode controller to shape the output impedance of the boost-circuit of quasi-switched boost inverter such that the propagation of the ripple from dc link to the dc-input source is resisted. The quasi-switched boost inverter is one of the advanced and suitable topologies for the micro-inverter applications. The adaptive nature of the proposed controller improves the transient performance of the system at the line–load transients unlike some existing solutions, which affects dynamics adversely to achieve ripple mitigation objective. The controller ensures voltage regulation within ${5\%}$ at dc link. The proposed control technique is verified using a lab-prototype of 500 W quasi-switched boost inverter.

A Flexible Load-Independent Multi-Output Wireless Power Transfer System Based on Cascaded Double T-Resonant Circuits: Analysis, Design and Experimental Verification

There are practical applications requiring the wireless power transfer (WPT) system to supply multiple output voltages to a variety of loads. In this paper, in order to achieve this goal, multiple double T resonant circuits are connected to the common port of the receiver side. Based on the modeling and analysis of the double T resonant circuit, it is found that the load-independent output and input zero phase angle (ZPA) can be derived. The proposed WPT system presents the following merits: 1) output voltages are load independent and can be controlled synchronously against the disturbance from input DC source and mutual coupling by using only one closed loop; 2) the output voltages can be adjusted individually to different levels by configuring circuit parameters; 3) only passive components are used to achieve multiple outputs. The power loss can be reduced due to the parasitic resistance of the passive component is very small and can be negligible; and 4) the reactive power losses are minimized due to the input ZPA of the system. An experimental prototype with two output channels is built, based on which the load independent and the controllable characteristics of the output voltages are verified.

Switched capacitors 9‐level module (SC9LM) with reduced device count for multilevel DC to AC power conversion

Switched capacitors (SCs)-based modules are being increasingly used for multilevel DC to AC power conversion, especially for low input voltage applications. Many of these topologies operate in two stages involving H-bridge switches, which endure high-voltage stress. The SC 9-level module (SC9LM) presented here operates in a single stage with one DC source and two capacitors. In addition, the peak inverse voltage of all power switches is confined to the voltage of the input DC source. The proposed 9-level module ensures a reduced number of power switches. In addition, with appropriate utilisation of states, two of the eleven switches in the module operate at fundamental switching frequency, thereby minimising the switching losses. A single SC9LM achieves a voltage gain of two. The proposed module is validated through circuit analysis followed by simulation and experimental results.

A Modified Aalborg Inverter Extracting Maximum Power From One PV Array Source

Distributed Photovoltaic Generation (DPVG) systems have become more important in recent years because of energy pinch and air pollution. Grid-tied inverters, as the indispensable parts of the DPVG systems, have drawn a lot of research attentions. Among various constructors, the Aalborg inverter was proposed as a candidate for the interface between the PV arrays and the power grid for some potential advantages, such as the wide range of input DC voltages, high efficiency, low cost and no leakage current. For a conventional Aalborg inverter, however, in order to gain a symmetrical gird-injected current, when the input DC voltages generated by the PV arrays are not equal, part of the input DC energy has to be discarded, which will reduce the conversion efficiency of the whole system. In this paper, a modified Aalborg inverter with a single input DC source is proposed to extract the maximum DC energy of PV arrays. The operating principle is illustrated via equivalent circuits. The control strategy is designed to balance the capacitor voltages and smooth the grid-injected current. A 110 V/50 Hz/800 W prototype has been built to verify the validity of the proposed inverter together with the effectiveness of the control strategy.

Analysis, Design, and Control of Switching Capacitor Based Buck–Boost Converter

A switching-capacitor-based buck–boost converter (with common ground) for point of load applications is proposed in this paper. It is capable of operating in stand-alone buck or boost mode in addition to its primary operation of performing the buck–boost conversion. The striking feature of the proposed converter is low source current ripple content irrespective of its mode of operation (buck–boost, buck, or boost). First, feasible pulsewidth modulation schemes for the proposed converter are identified and thereafter the corresponding circuit performance analysis, steady-state analysis, and state-space modelling is established. Through steady-state analysis, voltage gain expressions are formulated and equations defining L - C components are derived in terms of their ripple quantities. The state-space models are used to formulate small-signal analysis and to obtain the relevant transfer functions required in the controller design. A voltage-mode/current-mode controller is designed, with a tradeoff in bandwidth, to control the proposed converter and transit it from buck to boost mode or vice versa seamlessly. A 30–55 W , 100 kHz, prototype point of load converter with 36-V input dc source is built to supply power at constant load voltage of either 48 or 28 V. The proposed converters’ effectiveness is demonstrated experimentally in terms of reduced source current ripple along with seamless transition from buck to boost mode and vice versa.