Single‐phase common mode transformer‐less soft‐switching grid‐connected inverter with eliminated leakage current

Self Cite

This paper proposes a new modified buck–boost converter entitled the basic Z‐H8 topology. The modified configuration is composed by adding two dc decoupling and non‐ideal compensation blocks across the dc‐input side of the conventional Z‐H buck converter. These blocks create some benefits such as buck–boost ability and lower stresses and ripples for passive and active elements by up to 50% compared to the traditional Z‐H structure. Moreover, the proposed topology can be used as a dc/dc, dc/ac, or ac/dc converter. Hence, various control techniques based on unipolar PWM and SPWM are proposed for the basic Z‐H8 configuration to act as an inverter. Other valuable advantages are providing galvanic isolation and reducing leakage current by two blocks, which can be extremely useful for photovoltaic (PV) applications. Thus, a grid‐connected single‐stage PV system with a proper model predictive control algorithm is proposed. Despite a continuous voltage on the Z‐H8 inverter output, other benefits of the proposed PV system are tracking the maximum power point, adjusting the injected powers to the grid, and increasing security and reliability. The operating principle of the proposed topologies and control methods are explained in detail with the relevant equations and are confirmed by the simulation and experimental results.

Section: Introductionmentioning

confidence: 99%

“…To overcome the problems mentioned above, various structures have been introduced in the literature. The main purpose of them is to lock the common‐mode voltage (

v_{cm}

) at a constant value to reduce the leakage current 8–14 . The first class of these topologies includes H5, 9 oH5, 10 H6, 11 and FB‐DCBP 12 (full bridge with dc bypass) inverters.…”

Section: Introductionmentioning

confidence: 99%

“…The main purpose of them is to lock the common‐mode voltage (

v_{cm}

Section: Introductionmentioning

confidence: 99%

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Design and control of an improved Z‐H8 inverter for photovoltaic applications

Ahmadzadeh

Babaei

Sabahi

et al. 2022

Self Cite

“…Renewable resources are used as the input sources in microgrids and renewable power generation systems. [1][2][3] The gridconnected inverter is often used as an interface between the grid and renewable energy resources. 4,5 It can be classified into voltage-source and current-source grid-connected inverters.…”

Section: Introductionmentioning

confidence: 99%

Grid‐connected buck–boost inverter without shoot‐through issue and with reduced voltage stress

Yao

2021

Grid-connected buck-boost inverters are used in wide input-voltage range application. However, there is a shoot-through problem in traditional gridconnected inverters. Moreover, voltage stress of semiconductors is high in conventional buck-boost inverters. Therefore, a grid-connected buck-boost inverter without shoot-through issue and with reduced voltage stress is presented. The proposed inverter is a single-stage system. When input voltage is higher than the grid voltage, the proposed inverter works in buck mode; when input voltage is lower than the grid voltage, it operates in boost mode. Thus, voltage stress of semiconductors is reduced. Only one switch is operated in high frequency in each period, so efficiency of the inverter can be improved.Operating principle of the proposed inverter is illustrated. Voltage stress analysis, loss calculation, and filter design guidelines and example are given.Finally, simulation and experimental results of a 300-W proposed inverter confirm the theoretical analysis.

“…For the transformerless inverter topologies, if the input dc source and the grid do not share the same ground, the input dc source may have a large leakage current; to solve this problem, either extra switches have to be added to the existing topology which will inevitably increase the cost and system complexity or doubly grounded topologies have to be used. [11][12][13] In Tofigh Azary et al, 14 a transformer-less single-phase common mode single-stage soft-switching grid-connected inverter with maximum power point tracking (MPPT) and eliminated leakage current is proposed.…”

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.