Photovoltaic‐based grid‐connected transformer‐less three‐phase cascaded diode‐clamped multilevel inverter with reduced leakage current

Transformerless inverters (TLI) are widely accepted in photovoltaic (PV) systems. With the application of TLI, the bulky transformer from the conventional system can be removed, enhancing the PV system's compactness, cost, and efficiency. The direct connection of PV to the grid through the TLI causes common mode voltage (CMV). The variation of CMV causes the leakage current (LC) in the TLI topology. This paper suggests a new topology of five-level TLI for the PV system. The problem of LC is mitigated by providing common ground (CG) for both PV and the grid neutral. This topology uses only five switches, a diode, two DC link capacitors, and a switched capacitor (SC) to produce the five-level output voltage. Only two switches are conducted for positive and negative voltage level generation. The charging current of the SC is limited by using the front-end inductor. A level-shifted pulse width modulation (LS-PWM) is adopted for generating the gate pulses. A detailed mathematical approach has been suggested for the component selection and the losses associated with it through theoretical calculation and simulation. Further, an explicit comparative study is performed with existing similar kinds of topologies to claim the merits of the proposed topology. This topology is validated using both MATLAB/Simulink and the laboratory prototype model for a 1 kW system. It is observed that the voltage stress and current stress across the component are very less. Overall, the component count is reduced and helps to get an enhanced efficiency of 96.7%.

“…The maximum current ripple across the inductor during the steady-state operation can be expressed as in (11).…”

Section: Selection Of Filter Inductormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A common ground switched capacitor‐based single‐phase five‐level transformerless inverter for photovoltaic application

Neti

Singh

2023

“…PV systems may also be used without a transformer, which improves their efficiency and makes the whole system lighter, smaller, and easier to install. However, a transformerless grid‐connected PV system creates a common‐mode resonant circuit including the filter, the inverter, the grid impedance, and the PV parasitic capacitance 4,5 …”

Section: Introductionmentioning

confidence: 99%

“…However, a transformerless grid-connected PV system creates a common-mode resonant circuit including the filter, the inverter, the grid impedance, and the PV parasitic capacitance. 4,5 This common mode generates a leakage current that circulates through parasitic. Leakage current may have consequences on security issues; for instance, it is responsible for higher current harmonics, higher losses, and electromagnetic interference (EMI) issues.…”

mentioning

confidence: 99%

A simplified implementation of NLSPWM control strategy for SqZS inverter via model‐driven processor programming method

Noroozi

Haghjoo

Javadi

et al. 2022

The transformerless single‐phase semi‐quasi‐Z‐source inverter (SqZSI) has a nonlinear gain curve and requires nonlinear sinusoidal pulse width modulation (NLSPWM) to achieve sinusoidal voltage at the output AC terminal. Although the SqZSI provides some advantages, for example, leakage current elimination, doubly grounded, low volume, and low cost, it needs nonlinear modulation control. The NLSPWM is relatively complex among single‐phase modulation methods and it is considered a disadvantage for this topology, so this paper presents a model‐driven processor programming method that facilitates the implementation of NLSPWM. The developed programming method utilizes a Blockset environment in MATLAB/Simulink to implement NLSPWM, and then the obtained model is compiled and directly uploaded to the ARM Cortex‐M4‐based STM32F4 processor. In this approach, there is no need for coding in C programming language, and only the Simulink mathematical blocks are used so it simplifies the implementation process. The same Simulink model used to model the inverter control is slightly edited for implementation, which accelerates the debugging cycle. Experimental results of 100 W SqZSI confirm the desired and accurate performance of this low‐cost method. The qualitative comparison of the processor programming methods and the performance comparison of the developed SqZSI based on this approach verify the simplicity of implementation.

A single switch hybrid quadratic converter for grid‐integrated renewable energy system

Thirukkuralkani¹,

Srinivasan²,

Karthikeyan

2023

SummaryTo interface the electricity grid with renewable energy system applications, the system voltage is to be stepped up to a higher level. Here, the interfacing converter along with the transformer unit becomes an essential stage. Due to this traditional approach and the presence of a transformer, the size and cost of the entire unit are higher and reduce the efficiency of the system drastically with large space requirements, especially under light load conditions. To overcome this limitation, various dc‐dc converters have been proposed by researchers; however, the components' utilization and operation range of duty cycles are higher to obtain a higher voltage level. This particular paper proposes a novel single‐switch hybrid quadratic converter (HQC) for a grid‐integrated renewable energy system. The main objective of this proposed approach is to minimize the components count utilized in the converter with lower device stress to achieve higher gain; hence, it improvises the efficiency. The operational waveforms and mathematical relations based on the corresponding equivalent circuit are discussed in detail. To understand and analyze the merits of various performance parameters, the detailed comparative performance of the proposed HQC with existing converters is summarized in this paper. Finally, to validate and verify the novelty, the 500‐W experimental prototype was built and experimental results were captured and presented in this paper. It is observed that the proposed HQC can yield an efficiency of more than 95% under a lower range of duty cycles.