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Abstract Nowadays, transformer‐less Photovoltaic‐based grid‐connected inverters are more popular in renewable energy application due to their reduced size, cost, and high efficiency. However, the absence of galvanic isolation leads to the flow of leakage current in such system hindering personal safety, and deteriorating power quality. Therefore, this paper presents a five‐level transformer‐less inverter topology for PV applications with less component count and reduced complexity. The proposed inverter topology completely eliminates the common mode leakage current. Besides, the proposed topology has an inherent capability to boost the voltage without using any magnetic component or boosting circuit, and is based on the principle of switched/auxiliary capacitor. The proposed topology do not have any limitation of modulation index since the auxiliary capacitors are naturally balanced, hence less complex or no dedicated control scheme is required for balancing/regulating the auxiliary capacitor voltages. In order to verify the performance of the proposed inverter topology, a laboratory prototype is developed which confirms the operation, and feasibility of the proposed inverter. Results depicting the output voltage, load current, and voltage across the auxiliary capacitor are presented for various operating conditions. Further, simulation results depicting the leakage current in the proposed, H5, and H6 topologies are included. Finally, a quantitative comparison study is done, highlighting the benefits of the proposed inverter topology regarding boosted voltage, elimination of leakage current, and reduced component count.

Abstract This paper examines a multilevel transformer‐less grid‐tied inverter topology is proposed for PV applications. Nowadays, transformer‐less inverters are more desirous due to their small filter size, cheaper and higher efficiency. However, the removal of transformer results in the existence of leakage current due to absence of galvanic isolation. The flow of leakage current is the cause of personal safety and deteriorating power quality. A transformer‐less inverter topology is proposed which is able to solve the leakage current issue. Besides, it has the ability to generate the boosted voltage without the need of magnetic component or boosting circuit. It works on the principle of flying/switched capacitor which are able to naturally balance the voltage. Hence, it does not have the limitation of modulation index and no need of complex control scheme to balance or regulate the voltage across an auxiliary capacitor. The performance of the proposed topology is verified by implementing a laboratory prototype which validates the operation and performance of the proposed topology. Results depicting the output voltage, load current and voltage across the auxiliary capacitor are presented for various operating conditions. Moreover, a comprehensive comparison is done, in terms of component count, level and boosting ability of output voltage with leakage current condition.

This article presents a new topology for a single-stage nine-level (9L) switched-capacitor inverter. The structure of the proposed topology is not only simple but also compact. The proposed topology is developed with self-voltage balancing and a low number of power components. The output voltage (vo) gain is four times higher than the input voltage (vin). Each mode of operation is discussed with a detailed current path. The conventional sinusoidal pulsewidth modulation technique is used to generate the gate pulses. Next, the experimental results are obtained from a 1 kW prototype setup. The proposed topology is tested under different scenarios such as load change, input voltage changes, and modulation variations. Both simulation and experimental results have good agreement in terms of efficiency. Finally, a detailed comparative study is performed with other recent 9L inverters to prove the merits of the proposed topology. [ABSTRACT FROM AUTHOR]

Transformer-less inverters (TIs) are widely used in photovoltaic (PV) applications owing to their low cost and high efficiency. However, the combined effect of high-frequency common mode voltage and PV parasitic capacitance burdens the TIs with undesired ground leakage current. In this article, a switched capacitor (SC)-based five-level TI is proposed. The negative dc rail of the proposed TI is directly connected to the grid neutral, thereby completely eliminating the leakage current. Besides, it has the inherent capability of boosting the output voltage without using any magnetic component or additional circuitry. For several instances in every fundamental cycle, the SCs are paralleled with the input voltage source and hence are self-balanced. The proposed topology does not have any limitation on modulation index since the SC voltages are self-balanced and hence less complex or no dedicated control scheme is required. Further, a quantitative comparative study is presented, highlighting the benefits of the proposed TI regarding boosted voltage, elimination of leakage current, and reduced component count. Finally, in order to verify the performance of the proposed TI, detailed simulations followed by experiments on a laboratory prototype developed by using DS1202/1302 dSPACE controller are carried out and the results presented for both steady-state and dynamic conditions verify the feasibility of the proposed TI. [ABSTRACT FROM AUTHOR]

Boost type switched-capacitor inverter topologies are highly suitable for photovoltaic based distributed power generation and electric vehicle applications. This brief proposes a new single-stage boost type inverter topology with features of self-voltage balancing capability of floating capacitors (FCs), seven-level (7L) stepped output voltage generation with peak output voltage three times higher than the input voltage. The modes of operation are discussed in detail emphasizing the self-voltage balancing. Further, the proposed topology uses less number of semiconductor devices. A detailed comparison with other recent 7L inverter topologies is presented to attest to the merits of the proposed topology concerning a reduced number of components. Finally, a laboratory prototype is employed to validate the proposed topology’s operability, and the obtained experimental results are presented. [ABSTRACT FROM AUTHOR]

Multilevel inverters play an important role in extracting the power from renewable energy resources and delivering the output voltage with high quality to the load. This paper proposes a new single-stage switched capacitor nine-level inverter, which comprises an improved T-type inverter, auxiliary switch, and switched cell unit. The proposed topology effectively reduces the DC-link capacitor voltage and exhibits superior performance over recently switched-capacitor inverter topologies in terms of the number of power components and blocking voltage of the switches. A level-shifted multilevel pulse width modulation scheme with a modified triangular carrier wave is implemented to produce a high-quality stepped output voltage waveform with low switching frequency. The proposed nine-level inverter's effectiveness, driven by the recommended modulation technique, is experimentally verified under varying load conditions. The power loss and efficiency for the proposed nine-level inverter are thoroughly discussed with different loads. [ABSTRACT FROM AUTHOR]

A new boosting multilevel inverter with switched-capacitors is presented in this brief. By employing 13 switches, two diodes, and three capacitors, a 13-level voltage waveform is synthesized. The capacitor voltages are self-balanced as they are connected in parallel with the input voltage source for several instances in every fundamental cycle. A simple logic gate based pulse-width modulation scheme ensuring power balance among the capacitors is presented. Experimental results obtained from a laboratory prototype are presented for validating the operation and ability of the proposed inverter to boost the input by a factor of six. Finally, a detailed comparison with existing topologies proves the cost-effectiveness, a simpler structure requiring lesser space and footprint area of the proposed topology. [ABSTRACT FROM AUTHOR]

The new inverter topologies based on switched capacitor concept with voltage boosting ability are attractive for the low voltage applications. Such low voltage requirements allow a single-stage dc-ac power conversion, improving overall system performance, reliability and power density. This brief proposes a new multilevel inverter topology based on the switched-capacitor (SC) with a single source of dc voltage. The proposed topology is ideal for low voltage renewable energy applications. Seven-level (7L) output voltage is accomplished with triple voltage gain using two switched capacitors and 10 switches. Other major features of the proposed topology are self-voltage balancing of capacitor voltages, reduced number of switches with lower voltage stress and generation of negative voltage levels without using backend H-bridge. To show the advantages of the proposed topology, a detailed comparison with other similar topologies with seven-level single-source configuration has been accomplished in this brief. The proposed topology has been tested using the traditional level-shifted sinusoidal pulse width modulation (LS-PWM) technique. This brief includes various experimental results with different operating conditions to prove the performance of the proposed topology. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This brief presents a novel seven-level (7L) inverter topology for grid-connected renewable applications. It consists of ten active switches and one inner flying-capacitor unit forming a structure similar to conventional active neutral point clamped inverter. The proposed unique arrangement reduces the number of active, passive components and it does not require any sensor to balance the floating capacitor voltage, thereby reduces cost and complexity in the control system design. In addition, compared to major conventional 7L inverter topologies, the proposed topology is capable of boosting the input voltage by a factor of 1.5, thereby, eliminating the need for an intermediate boosting stage. In other words, it reduces the dc-link voltage requirement by 50%. To prove the advantage of the proposed topology over other recent topologies, a comparative study in terms of power components and cost is presented. The operation and performance of the proposed topology for various loading conditions are validated through experimental tests and measurements. [ABSTRACT FROM AUTHOR]

Summary: This paper proposes an improved "K" type seven‐level switched capacitor inverter topology. The proposed topology consists of eight active switches, one floating capacitor, and two dc‐link capacitors. The floating capacitors are charged and discharged in each half‐cycle to maintain the capacitor voltage with the same value of the input voltage. The floating capacitor voltage is self‐balanced, and the output voltage is 1.5 times higher than the input voltage. To prove the superiority of the proposed topology, it is compared with the existing seven‐level inverters in terms of maximum voltage stress on the switch and required the number of power components. The simulation and experimental validation are carried out for 1.6 kW, 50 Hz using a laboratory‐based setup with a switching frequency of 5 kHz. The results are discussed highlighting the performance of the proposed topology for the dynamic load variations at different modulation indices. Both simulation results and experimental results have good agreement in terms of voltage balancing of flying capacitor. [ABSTRACT FROM AUTHOR]

Transformerless inverters (TIs) are widespread in photovoltaic (PV) applications due to their low cost and high efficiency. However, TIs suffer due to leakage current as a consequence of PV parasitic capacitance, and high-frequency common-mode voltage, which has resulted in the emergence of several topological and control scheme modifications. In this article, a switched-capacitor (SC) based inverter capable of synthesizing a five-level voltage is proposed. In the devised structure, the negative pole of the dc bus is directly connected to the grid neutral, thereby resulting in zero leakage current. In addition, industrial standard half-bridge modules can be employed directly for implementing the proposed inverter without modifications, making it more practically feasible. The proposed topology has the capability of self-voltage balancing of SC, reactive power processing, and full dc-bus utilization as opposed to half-bridge topologies. The principle of operation and a simple logic-gate-based pulse generation scheme is presented in detail. Simulation and experimental results confirming the practical viability of the proposed topology are presented. Finally, the superior features and the merits of the proposed topology are shown through a detailed comparison against state-of-the-art topologies. [ABSTRACT FROM AUTHOR]

Switched capacitor multilevel inverter (SCMLI) with reduced components is attractive for higher number of voltage levels due to less implementation complexity and low cost. In this study, a new family of hybrid SCMLI for high frequency power distribution system is presented to eliminate the intermediate power conversion. Firstly, a five-level SCMLI employing a single voltage source is proposed, which is further extended to nine-level (9L) with its operation. Further extension/enhancement of the proposed 9L-SCMLI for generating a higher number of voltage levels with reduced number of components is achieved on the basis of structural modification. The mathematical analysis for determination of capacitance, power loss analysis and comparative analysis has been provided in detail. A comprehensive comparison with other similar topologies is also provided to highlight the merits of the proposed topology. Simulation and experimental results are discussed for various dynamic load conditions with different output frequencies to validate the suitability of the proposed SCMLI for various high-frequency AC applications, such as renewable energy systems, microgrids, electric vehicles and so on. [ABSTRACT FROM AUTHOR]

In this brief, a seven-level (7L) improved packed U-cell (IPUC) inverter with reduced power electronic components is proposed. The presented IPUC inverter has low voltage stress on switches and is capable of voltage boosting. A new voltage balancing method based on logic form equations is developed for regulating the inherent floating capacitor voltage to half the input dc voltage. The proposed 7L IPUC is compared with other state-of-the-art 7L inverters in terms of number of IGBTs, blocking voltage, and driver circuits for attesting its superior merits. The performance of the proposed voltage balancing is verified through a laboratory prototyped 7L IPUC inverter considering varying load conditions and the corresponding results are elucidated. [ABSTRACT FROM AUTHOR]

This letter describes a novel nine-level inverter based on switched capacitors (SCs) with quadruple-boost ability requiring reduced components. The structure of the proposed topology relies on the series/parallel connection of SCs. It consists of 12 switches and two SCs. As opposed to similar SC-based inverters, the proposed topology does not employ a back-end H-bridge and the voltage stress of all the switches does not exceed twice the input dc voltage. A simple logic-gate-based pulsewidth-modulation scheme is developed for gating the switches of the proposed topology. A comprehensive comparison against the state-of-the-art topologies in terms of the required number of components is performed to attest the outperforming merits of the proposed topology. Finally, various experimental results are presented to validate the feasibility and operability of the proposed topology. [ABSTRACT FROM AUTHOR]

Two-Stage boosting multilevel inverters (MLIs), which are highly suitable for photovoltaic power plants, are known to suffer because of the high voltage stress on the switches of second stage. One of the ways to confront this issue is through eliminating the front-end booster. However, this leads to increased structural and control complexity of the resulting integrated boosting MLI. This letter presents a single-stage boosting MLI requiring lesser number of switches, diodes, and capacitors for renewable power generation applications. It requires nine switches and only one capacitor for five-level voltage generation. The topology has inherent self-balancing capability, thereby does not need additional balancing circuitry. The proposed topology has a uniform peak inverse voltage stress on the switches of value equal to the input dc voltage. A less complicated logic-form-equations-based gating pulse generation scheme is designed for enabling the proposed MLI to maintain its capacitor voltage. Further, a comparative study with state-of-the-art topologies is carried out to demonstrate the superior performance of the proposed topology. Finally, the feasibility of the proposed topology is validated through experimental tests and the corresponding results are elucidated. [ABSTRACT FROM AUTHOR]

This paper presents a nine-level transformer-based inverter requiring only eight switches. The envisaged structure consists of two standard H-bridges fed from a single dc source. Besides, a single-phase transformer is employed to aid the process of intermediate voltage level generation. An ad-hoc pulsewidth modulation scheme based on boolean logic form equations is developed to derive the gating pulses. An effortless extension of the proposed inverter to a higher number of voltage levels is also achieved by generalizing the switching functions. Furthermore, the superior performance of the proposed topology is demonstrated through a comprehensive cost-based analysis. Finally, the validation of the proposed topology is accomplished through experiments on a down-scale prototype, and the measurement results are included. [ABSTRACT FROM AUTHOR]

This letter presents an improved sensorless nine-level inverter topology with reduced number of components. It is formed by cascading a three-level T-type neutral clamped point inverter with a floating capacitor (FC) fed two-level converter unit. Additionally, two line-frequency switches are appended across the dc-link. A simple logic-form equations-based pulse width modulator is designed which is in-charge of maintaining the FC voltage at its reference value without any aid of voltage and current sensor. Thus, the complexity in control of the proposed topology is very minimal. The working principle of the proposed inverter and formulation of logic-form equations is deliberated in detail. Furthermore, experimental results obtained from the developed prototype are presented to validate feasibility and operability of the proposed topology. Finally, a comprehensive comparison with some of the recently reported inverter topologies proving the merits of the proposed topology is included. [ABSTRACT FROM PUBLISHER]

This paper presents a nine-level active-neutral-point-clamped (ANPC) based multilevel inverter (MLI) topology for grid-connected applications requiring only ten switches. The envisaged structure comprises two parts, namely five-level ANPC unit, and a two-level converter leg whose midpoint is used as another ac terminal. An ad hoc switching state redundancy based modulation strategy is used to ensure that the voltage across the flying capacitor is tightly balanced and is implemented using a look-up table further simplifies the control complexity. The performance and effectiveness of the proposed topology with its control scheme are validated through simulations and experimental tests. Comparison with other MLIs is included to highlight the merits of the proposed topology. From the results, it will be shown that the proposed inverter requires the least part count as compared to other topologies with the same performance and output quality. [ABSTRACT FROM PUBLISHER]

This paper proposes a new nine-level inverter for medium- and high-power applications. The proposed topology comprises of a three-level (3L) active neutral-point-clamped (ANPC) inverter connected in series with a floating capacitor (FC) fed H-bridge. Besides, two additional switches operating at line frequency are appended across the dc link of the 3L ANPC structure. Compared with conventional hybrid cascaded inverters, the primary advantage of this addition is doubling of the resulting root mean square output voltage. This amelioration is achieved while preserving the standard 3L ANPC and H-bridge structures with minimum topological modification. A simple logic-gate-based voltage balancing scheme is developed to regulate the FC voltage. The proposed voltage balancing method is independent of load power factor, inverter modulation index, and can balance the voltage across FC instantaneously. The step-by-step formulation of logical expressions for the generation of gating pulses is deliberated in detail and can be generalized for any $n$-level inverter. Further, simulation results as well as the experimental measurements obtained from the laboratory prototype are presented to validate the effectiveness and practicability of the proposed configuration. Finally, the notable merits of the proposed inverter over the prior art topologies is established through a comprehensive comparative study. [ABSTRACT FROM PUBLISHER]

This letter proposes a single-phase nine-level (9L) inverter topology suitable for grid-connected renewable energy systems. The proposed inverter is realized using a T-type neutral-point-clamped inverter connected in cascade to a floating capacitor (FC) H-bridge. Additionally, two low-frequency switches are added across the dc-link enabling the inverter to generate a 9L waveform. A sensorless voltage control based on redundant switching state is developed and embedded with PWM controller, which is responsible for regulating the FC voltage at one-quarter of the dc source voltage. The proposed PWM technique employs the generation of 9L waveform without using any voltage sensor, thereby reducing the complexity of the overall control scheme. This, in turn, will make the overall system appealing for various industrial applications. In comparison to conventional and recent topologies, generation of the 9L waveform using a lower number of components is the notable contribution. Another important feature of the proposed inverter is that if FC H-bridge fails, it can be bypassed, and the inverter can still operate as a 5L inverter at its nominal power rating. Furthermore, a comprehensive comparison study is included which confirms the merits of the proposed inverter against those of other state-of-the-art topologies. Finally, simulation and experimental results are included for validating the feasibility of the proposed system. [ABSTRACT FROM PUBLISHER]