Transformerless Inverter Research Articles

High Efficiency Single Phase Photovoltaic Based Pulse Width Modulated Transformerless Inverter Tied to Grid

High Efficiency Single Phase Photovoltaic Based Pulse Width Modulated Transformerless Inverter Tied to Grid

Self-Balanced Switched-Capacitor Common-Grounding Boost Multilevel Inverter

Transformerless inverters have been extensively deployed in photovoltaic (PV) applications, owing to features such as high efficiency, high power quality, and low cost. However, the leakage current in such inverters due to the absence of galvanic isolation has resulted in several topological modifications. This paper introduces a single-input switched-capacitor (SC)-based multilevel inverter (MLI) that is capable of eliminating the leakage current due to its common-ground structure. Also, the proposed inverter has the capability of single-stage voltage boosting, which is essential in PV systems. The series–parallel switching facilitates the self-balancing of SCs, which, in turn, assists in voltage boosting. Moreover, the proposed MLI synthesizes a seven-level output using only eight switches. Following an in-depth analysis of the circuit operation, modulation scheme, and power losses, a detailed comparison among recently developed seven-level MLIs is carried out, which verifies the design's superiority. Extensive simulation and experimental results are presented to validate the prominent features of the seven-level MLI under dynamic operating conditions.

Comprehensive analysis on topologies for limiting leakage current in transformerless inverter

With the evolution of science and technology, human beings' demand for electric energy has increased rapidly. Traditional power generation methods such as using fossil fuel will result in serious greenhouse gases emitting, which leads to an intensification of the global greenhouse effect. Using clean energy to replace traditional power generation methods becomes urgent. As a reliable energy source, sunlight could continuously provide energy for human beings and Solar energy has accounted for a large proportion of new energy. Solar energy is converted into Direct Current (DC) by solar panels and the power transmitted from the power grid to factories and houses requires Alternating Current (AC), in this condition, inverters that could convert DC to AC are important components in photovoltaic (PV) systems. As the development of inverter technology gradually matures, inverters begin to develop with the characteristics of small, low-cost, and transformerless. This article introduces a common technical problem encountered in developing transformerless inverters-the generation of leakage current. Several different transformerless inverter topologies are compared to find reliable methods to limit leakage current, and some suggestions are raised for the future development of transformerless inverters.

Review on Close Loop Control of Novel Transformer Less Inverter Topology for Single Phase Grid Converter

The continuous urge for improvement in our standard of living has increased the consumption of electrical energy by leaps and bounds. This hike in energy consumption, draining of fossil fuels and degrading global environment has led to invention of green power generation systems. Thus, the global demand for renewable resources has led to flourishing of photovoltaic (PV) market. The enabling technology in the PV systems is the inverter, which could be either: 1) with transformer isolated or 2) without transformer non-isolated (transformer-less inverter). Recently, single phase transformerless voltage source inverters (VSI) have been extensively used for distributed photovoltaic grid tied systems. The objective of this paper is to review a few notable topologies and propose a new topology for transformer-less photovoltaic inverter. The analysis and design of the proposed topology is verified by simulating it on PSIM. Furthermore, the simulation results are validated by testing a proof-of-concept laboratory hardware prototype rated at 250 W. Keywords— Photovoltaic (PV) systems, transformer-less, single phase inverter

A seven‐level switched‐capacitor based transformerless inverter with modified PWM strategy to enhance the performance of grid‐connected PV systems

AbstractAmong different types of transformerless photovoltaic inverters, multi‐level inverters based on switched‐capacitors (SC) are the burning topic of recent decades due to their potential advantages, such as, single source requirement, voltage boosting capability, and high power density. However, for a seven level output voltage, a conventional SC based inverter architecture uses more than two units of SC, a large amount of power switches, which then lead to capacitor voltage balancing problems. This paper presents a seven‐level switched‐capacitor transformerless inverter (SCTI), which is structured with only two SC units, ten power switches, and a single DC source. The proposed SCTI ensures voltage boosting capability, self‐voltage balancing, and low power semiconductor losses. Apart from these, a modified sinusoidal pulse width modulation (MSPWM) is also proposed in this work, which guarantees better thermal performance and low inverter output voltage THD for the proposed SCTI. The proposed SCTI along with the MSPWM is simulated in MATLAB/Simulink and PLECS computer simulation environments. A reduced scale laboratory prototype is also built and tested to ensure the feasibility of the proposed SCTI.

Single Phase Transformer Less Inverter for Grid Connected Photo Voltaic System

Sustainable power generation systems have been developed as a result of increased consumption of energy, the rapid depletion of fossil fuels, and environmental degradation worldwide. Thus, the demand for photovoltaic systems is increasing, owing to the increased need for renewable resources worldwide. Transformers are often used in photovoltaic systems to offer voltage ratio conversions between input and output along with galvanic isolation. The inverter, that may be a transformer-less or with a transformer, is the enabling technology in PV systems. But, the efficiency and power density of these traditional iron and copper-based transformers are decreased while the inverter's weight, size, and cost are increased. Thus, it is recommended to refrain from utilizing transformers within the inverter. For this reason, transformer-less inverters for grid-tied, low-voltage, single-phase photovoltaic (PV) systems have gained more attention thesedays. To comply with the safety requirements imposed by grid regulations, there are a few distinctive challenges, particularly with respect to leakage current problems, which need to be sufficiently handled. Owing to this In recent years, distributed solar grid-tied systems have made widespread use of single phase transformerless Voltage Source Inverters.
 This paper explores a novel transformer-less solar inverter for grid connected PV system and Results are investigated in MATLAB Simulink provided a significant reduction in distortion in voltage and current at load side.

Comparative study of single-phase multilevel cascaded transformerless inverters with different modulation methods

This paper presents an in-depth exploration of a single-phase multilevel cascaded H5 (CH5) transformerless inverter employing both phase-shifted PWM (PS-PWM) and level-shifted PWM (LS-PWM) methodologies. A comparative analysis is conducted with the conventional multilevel inverter (MLI) topologies, specifically the cascaded H-bridge (CHB) and H5 inverter configurations. The investigation delves into the impact of modulation index variations, load fluctuations, and modulation methods on the inverter's operational performance.While switches in the CHB-MLI operate continuously at the carrier frequency state using PS-PWM and LS-PWM methods, the CH5-MLI exhibits a unique behavior with some switches toggling at high frequency, while others synchronize with the grid frequency. The CH5-MLI topology demonstrates efficiency improvements and a reduction in total harmonic distortion (THD). Notably, employing the LS-PWM method yields more significant efficiency enhancements and THD reduction compared to the PS-PWM method. To analyze power loss characteristics under diverse operating conditions, the PLECS simulation environment is leveraged for calculating conduction and switching losses.The application of phase-shifted and level-shifted carrier-based pulse width modulation strategies to high and low-frequency switching switches results in minimized output harmonics, elevated operator safety, and enhanced overall reliability and efficiency. This work contributes significantly to the field by offering a detailed exploration of the CH5-MLI topology's dynamic behavior, modulation strategies, and their collective impact on performance metrics such as efficiency, THD, and power losses.

Efficiency Analysis of Single-Phase Photovoltaic Transformer-less Inverters

This paper presents an efficiency analysis of five single-phase transformer-less inverters for photovoltaic applications (Full H-Bridge, Half H-Bridge, H5, HERIC and NPC inverters) implemented with different topologies of switches. Silicon (Si) and Silicon Carbide (SiC) diodes have been considered combined with two kinds of IGBTs. Simulation results have been obtained for each of the systems in different operating conditions by using PLECS software. Power losses and European Efficiency (EE) have been calculated for all the topologies by including the real characteristics of the switches in the thermal models provided by the software

Transformerless Inverter with Charge Pump Circuit Concept for PV Application

This paper introduces a new single phase transformerless photovoltaic (PV) inverter for grid connected PV systems using the concept of a charge pump. It consists of four power switches, two diodes, two capacitors and an LC filter at the output stage. The neutral of the grid is directly connected to the negative terminal of PV panel. This common ground creates a constant Common Mode (CM) voltage and zero leakage current. Meanwhile, the charge pump circuit generates the negative bus voltage for the inverter during the negative power cycle. A unipolar Sinusoidal Pulse Width Modulation (SPWM) technique is applied to the proposed inverter with three level output voltage to reduce the output current ripple and the filter requirements. The main advantages of the proposed inverter are (1) the negative polarity of the PV is directly connected to the grid, so the leakage current eliminated, (2) it has a compact size, (3) peak of output voltage is equal to input dc voltage (unlike Neutral Point Clamped (NPC) inverter, Active NPC (ANPC) and some topologies, which requires two times of the peak ac-voltage magnitude), flexible grounding configuration and high efficiency. The operating principle and analysis of the proposed topology are presented in details. Experimental results of a 500 W prototype are demonstrated to validate the proposed topology and the overall concept. The obtained results clearly verify the performance of the proposed inverter and its practical application for grid connected PV systems.

Design and Implementation of Transformer-less Common-Ground Inverter With Reduced Components

Nowadays, common-ground-type (CGT) based transformer-less inverters (TIs) are gaining more popularity in photovoltaic (PV) applications owing to their low cost, weight of the systems, losses and zero ground leakage current. For PV applications, a separate boost converter is often used to boost the low PV array voltage, resulting in increased component count, cost and lower efficiency. To resolve this issue, switched-capacitor (SC) based CGT inverter with reduced component count is proposed in this paper. The proposed amalgamation of CGT and SC technique, results in inherent boosting and zero ground leakage current. In the proposed inverter, SCs are connected in series/parallel with the dc voltage source for several instances in a fundamental cycle preserving the self-voltage balancing ability. Therefore, the proposed topology is devoid of voltage sensors to balance the voltage across SCs. Further, A simplified logic gatebased pulse-width-modulation strategy is developed. In addition, the benefits of proposed inverter are highlighted and compared with the other recent SC inverter topologies with regard to boosted voltage, elimination of leakage current and reduced component count. A laboratory prototype is developed by using DS1202/1302 dSPACE controller and experimental results are presented for both steady state and dynamic conditions and verifying the feasibility of the proposed TI.

A Switched-Capacitor Based Single-Phase Transformerless Inverter for Grid Integration

A Switched-Capacitor Based Single-Phase Transformerless Inverter for Grid Integration

A cutting-edge single-stage buck-boost transformer-less inverter for 1- φ grid-tied solar PV schemes

A state-of-the-art single-stage Buck-Boost transformer-less inverter intended especially for one-phase (1-ϕ) grid-tied solar photovoltaic (PV) schemes is presented in this abstract. This cutting-edge inverter, which represents a major development in solar energy technology, is notable for its effectiveness, small size, and smooth interaction with grid-tied systems. By doing away with the necessity for a transformer, the single-stage architecture simplifies the energy conversion procedure and lowers the overall complexity of the system. The inverter's buck-boost feature allows it to adjust to changing solar conditions, resulting in the best possible energy harvesting from photovoltaic panels. Customized for 1-ϕ grid-connected applications, the inverter improves system performance and makes it simple to integrate into the current power infrastructure. By reducing possible points of failure, the transformer-less design enhances the inverter's compactness and dependability even more. This innovative invention has the potential to enable the deployment of solar PV systems that are both economical and effective, providing a sustainable energy solution appropriate for a variety of environmental conditions. This abstract highlights the importance of the inverter in promoting innovation within the renewable energy field, hence urging additional investigation and implementation.

A Hybrid PWM Technique for SMES Integrated Solar PV Based Grid-Tied Transformerless Inverters

A Hybrid PWM Technique for SMES Integrated Solar PV Based Grid-Tied Transformerless Inverters

Feedback Linearization Control for a Class of Transformerless Common-Ground VSI

As is well known in practice, conventional transformerless inverters may suffer the risk of high-frequency leakage currents between the photovoltaic (PV) array or battery energy storage systems (BESS) and the ground due to the stray capacitances. This operational condition can generate several electrical problems. Recently, we proposed in [1] a new method for designing transformerless topologies of single-phase voltage source inverters (VSI) with common ground derived from four classical DC-DC converters. As a sequence of that previous work, a novel control technique based on a feedback linearization approach is proposed to control that class of transformerless VSI with common ground in this paper. Unlike the classical local linearization techniques commonly used in the technical literature, this approach allows to obtain large-signal linear equations, by means of the feedback linearization of the non-linear terms. Real-time simulation results using Hardware-in-the-Loop allow validation of the proposed discrete control technique applied to this class of VSI topologies.

Analysis and Improved Behavior of a Single-Phase Transformerless PV Inverter

Transformerless inverters have an important role in the electrical energy market. The high-efficiency and reliable inverter concept is one of the most widely used inverters in single-phase photovoltaic systems because of its high efficiency, low cost, and reduced leakage ground current. However, the leakage ground current behavior depends on the power and weather conditions, which can increase the parasitic capacitance value, thus producing an increase in the leakage ground current magnitude. In this paper, it is proposed to add a passive inductive–capacitive output filter to the inverter structure in order to reduce the dependency of the leakage ground current on the system power and weather conditions. The inductive–capacitive output filter is designed in such a way that it can provide a low impedance path for the leakage ground current, different from the ground path. The proposed system was evaluated both through simulations and experimentally in a 1 kW laboratory prototype.

Design of H5 Transformerless Inverter for Photovoltaic System

There are two distinct categories of sources for generating electrical power: conventional and non-conventional. At now, traditional sources such as coal, gas, and nuclear power are widely employed for the purpose of electricity generation; nevertheless, they are associated with detrimental environmental consequences. Therefore, it is crucial to utilize renewable energy sources like sun and wind to provide some of the necessary electrical power. The driving force behind this transition is the imperative for clean energy, the mitigation of greenhouse gas emissions, and the capacity to create electricity in geographically isolated regions. A proposed solution for using solar energy in single-phase AC applications involves the implementation of an H5 converter topology. The proposed architecture employs twin input DC-DC boost converters, which incorporate solar panels and batteries, to manage the desired output DC voltage. The H5 topology has notable suitability for single-phase transformerless inverters in AC applications encompassing low and high-power demands, owing to its capacity to effectively mitigate leakage current. In order to evaluate the viability of the suggested methodology, a MATLAB simulation is performed to simulate the complete procedure. Furthermore, the development of a prototype is underway in order to assess and verify the performance and outcomes of the converter. The simulation will be conducted with either the MATLAB.

An Efficient Grid Connected Photovoltaic System Based on H6 Transformer-less Inverter

Grid-connected photovoltaic (PV) systems based on transformer-less inverters have been widely used. Various topologies of transformer-less inverters are presented. The requirements of minimizing leakage current through transformer-less inverters and maximizing the power generated from PV arrays are of great importance. This paper presents a complete system that can effectively minimize the leakage current to safe values. In addition, operation at maximum PV array power point is realized. The system is based on modified H6 transformer-less inverter to minimize the leakage current. Perturbation and Observation P&O maximum power point tracker in addition to a dc-dc boost converter are utilized to achieve the second target. Analysis of each part and system controllers in the proposed system are presented in detail. Losses and system efficiency are introduced. Effects of sun irradiance variations are included. Simulation results prove the effectiveness of the proposed system.

Comparative Study on Analysis of Losses and Leakage Current for Transformer-less Inverters for PV Applications: A Review

Abstract: The reduction in the Common Mode Voltage (CMV) and thermal losses in semiconductors play a crucial role in designing of a new transformer-less inverter topologies for solar powered applications. The galvanic isolation and the leakage current problem due to non-availability of transformer can be addressed either by providing additional switches on the dc side or on the ac side, but this results in more number of semiconductor devices being added into the conduction paths which are switched according to the desired output requirements which further results in high conduction and switching losses indirectly effecting the efficiency of the transformer-less inverters. Hence it is important to study the existing topologies in view of the total losses, CMV and leakage current parameters together. In this review paper H5, H6 and HERIC transformer-less inverter configurations in terms of CMV, Leakage current, Conduction and Switching losses as total losses have been analyzed using PSIM2022.2 simulation software package with the availability of the thermal module. The study of total losses with CMV and leakage current will help in noting the drawbacks of the topologies discussed in this paper.

Topologies and modulation methods in leakage current suppression for PV grid-tied inverters

Photovoltaic (PV) inverters are widely discussed as solar energy became commonly used as a renewable energy source. Transformerless grid-tied inverters are often chose for their low cost and low energy loss. Since the existence of stray capacitance between PV cells and conducting surface causes a changing common-mode voltage (CMV) which would arise leakage current and thus pollute the output current quality to the grid and endanger human safety, novel topologies and modulation strategies are proposed to save the problem for transformerless inverters. In this paper, different methods to suppress the leakage current will be analysed. The theoretical analysis of CMV and leakage current generation by single-phase inverter is presented. Based on the basic principle of leakage current suppression topologies proposed to eliminate the leakage current are introduced. The effects of some well-known modulation methods on CMV controlling have been compared, and novel methods dealing with three-phase harmonic management are presented.

A single‐phase seven‐level buck‐boost common ground transformerless inverter for grid‐connected photovoltaic system

AbstractTransformerless inverters have recently gained attention in view of their economic benefits and compactness for photovoltaic (PV) systems. However, the limited voltage regulation and common‐mode (CM) leakage current are major concerns in conventional transformerless PV inverters. This paper presents a single‐phase seven‐level buck‐boost common ground transformerless inverter (SLB2CGTLI) to achieve a wide range of output voltages and zero leakage current without any additional stages, respectively. The proposed converter utilizes switched capacitor (SC) cell to buck‐boost the input DC voltage and generates seven‐level voltage at the output terminals. A simple reconfiguration strategy is adopted in the switched capacitor cell to maintain the charge‐second balance across the capacitors. Moreover, the common ground between the AC grid neutral and the PV panel's negative terminal mitigates the leakage current completely. The theoretical steady state analysis for both buck and boost mode is presented and verified with simulation using MATLAB Simulink. The performance of the proposed inverter is analyzed and validated with experimental results by developing a laboratory prototype. Further, the dynamic response of the proposed converter is carried out using OP4510 real‐time simulator for the grid‐connected PV application.