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

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## Abstract

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## 1. Introduction

- An improved LC output filter is included in order to improve the LGC mitigation capability of the HERIC converter.
- It is demonstrated through the mathematical models of common mode and differential mode that the modified LC filter improves the LGC mitigation capability.
- The improvement of the LGC behavior by eliminating the dependency on power, size and weather conditions without the use of additional power semiconductors, special control design or specific modulation strategies.

## 2. Inverter Description and PWM Strategy

## 3. Proposed Passive Method

#### 3.1. Common and Differential Mode Models

#### 3.2. LC Filter Analysis

## 4. Simulation Results

## 5. Laboratory Implementation and Comparative Analysis

## 6. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Abbreviations

3P-CMI | Three-phase cascade multilevel inverter |

3P-FB | Six-switch three-phase inverter |

3P-FBSC | Six-switch three-phase inverter with split capacitor |

3P-NPC | Three-phase neutral point clamped inverter |

CASVM | Conventional asymmetric space vector modulation |

CMC | Common-mode current |

CMM | Common-mode model |

CMV | Common-mode voltage |

CPLD | Complex Programmable Logic Device |

CSSVM | Conventional symmetric space vector modulation |

DC | Direct Current |

DC-AC | Direct Current–Alternating Current |

DSP | Digital Signal Processor |

DSVMMAX | Discontinuous space vector modulation maximum |

HERIC | Highly efficient and reliable inverter concept |

IGBT | Isolated Gate Bipolar Transistor |

LKC | Leakage currents |

MOSFET | Metal-oxide-semiconductor field-effect transistor |

NPC | Neutral Point Clamped |

NSPWM | Near-state pulse width modulation |

PWM | Pulse Width Modulation |

PV | Photovoltaic |

RMS | Root Mean Square |

SVM | Space Vector Modulation |

SVPWM | Space vector pulse width modulation |

THD | Total Harmonic Distortion |

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**Figure 16.**Experimental output voltage ${v}_{dm}$ (

**top**) and current ${i}_{out1}$ (

**bottom**) without the proposed filter.

**Figure 17.**Experimental output voltage ${v}_{dm}$ (

**top**) and current ${i}_{out1}$ (

**bottom**) with the proposed filter.

**Figure 26.**From top to bottom, current through ${C}_{f1}$, ${C}_{f2}$ and common mode current ${i}_{LGC}$.

State | ${\mathit{S}}_{1}$ | ${\mathit{S}}_{2}$ | ${\mathit{S}}_{3}$ | ${\mathit{S}}_{4}$ | ${\mathit{S}}_{5}$ | ${\mathit{S}}_{6}$ | ${\mathit{V}}_{\mathit{Az}}$ | ${\mathit{V}}_{\mathit{Bz}}$ | ${\mathit{V}}_{\mathit{AB}}$ | ${\mathit{V}}_{\mathit{cm}}$ |
---|---|---|---|---|---|---|---|---|---|---|

$\mathbf{1}$ | 1 | 0 | 0 | 1 | 1 | 0 | ${V}_{pv}$ | 0 | ${V}_{pv}$ | ${V}_{pv}/2$ |

$\mathbf{2}$ | 1 | 0 | 1 | 0 | 1 | 0 | ${V}_{pv}$ | ${V}_{pv}$ | 0 | ${V}_{pv}$ |

$\mathbf{3}$ | 0 | 0 | 0 | 0 | 1 | 0 | - | - | 0 | 0 |

$\mathbf{4}$ | 0 | 0 | 0 | 0 | 0 | 1 | - | - | 0 | 0 |

$\mathbf{5}$ | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | 0 |

$\mathbf{6}$ | 0 | 1 | 1 | 0 | 0 | 1 | 0 | ${V}_{pv}$ | $-{V}_{pv}$ | $-{V}_{pv}/2$ |

Parameters | Variable | Value |
---|---|---|

DC input voltage | ${v}_{pv}$ | 220 V |

Rated power | S | 1 kW |

Modulation frequency | ${f}_{m}$ | 60 Hz |

Modulation index | ${m}_{a}$ | 0.9 |

Switching frequency | ${f}_{c}$ | 12 kHz |

Dead-time | ${t}_{d}$ | 4 $\mathsf{\mu}$s |

Active power | P | 1 kW |

Input capacitor value | ${C}_{pv}$ | 660 $\mathsf{\mu}$F |

Filter capacitor value | ${C}_{f1,2}$ | 5 $\mathsf{\mu}$F |

Filter inductor value | ${L}_{1,2}$ | 2 mH |

Ground parasitic resistance value | ${R}_{g}$ | 10 $\Omega $ |

Parasitic capacitance value | ${c}_{p1,2}$ | 20–840 nF |

**Table 3.**THD${}_{i}$ values obtained with the numerical simulations with and without the output LC filter.

THD${}_{\mathit{i}}$ | Value |
---|---|

Without the output filter | 2.91% |

With the output filter | 3.04% |

$\mathbf{Parasitic}\mathbf{Capacitance}\mathbf{Values}$ | ${\mathbf{i}}_{\mathbf{LGC}}$ Value |
---|---|

20 nF capacitance | 1.04 mA${}_{RMS}$ |

840 nF capacitance | 35.41 mA${}_{RMS}$ |

Part Number | Description | Characteristics | Amount |
---|---|---|---|

G4PC40FD | IGBT (with ultra fast soft recovery diode) | 600 V, 27 A. | 6 |

IDH16S60C | SiC Schottky Diode | 600 V, 16 A. | 2 |

HFBR-2531 | Fiber optic opto receiver | 7 V, 25 mA. | 6 |

HCPL-3120 | Opto-coupler for IGBT gate drive | 5 V, 16 mA, 1200 V. | 6 |

Power | ${\mathbf{i}}_{\mathbf{LGC}}$ without Filter | ${\mathbf{i}}_{\mathbf{LGC}}$ with Filter |
---|---|---|

Peak Value–RMS Value | Peak Value–RMS Value | |

347 W | 910 mA–127 mA | 150 mA–20 mA |

1000 W | 710 mA–72.1 mA | 130 mA–20.8 mA |

${\mathit{C}}_{\mathit{p}\mathbf{T}}$ | ${\mathbf{i}}_{\mathbf{LGC}}$ without Filter | ${\mathbf{i}}_{\mathbf{LGC}}$ with Filter |
---|---|---|

Peak Value–RMS Value | Peak Value–RMS Value | |

20 nf | 850 mA–30.3 mA | 230 mA–16 mA |

840 nf | 1.01 A–105 mA | 170 mA–36.7 mA |

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© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Martinez-Rodriguez, P.R.; Vazquez-Guzman, G.; Perez-Bustos, G.O.; Sosa-Zuñiga, J.M.; Aztatzi-Pluma, D.; Lopez-Nuñez, A.R.; Rodriguez-Cortes, C.J.
Analysis and Improved Behavior of a Single-Phase Transformerless PV Inverter. *Machines* **2023**, *11*, 1091.
https://doi.org/10.3390/machines11121091

**AMA Style**

Martinez-Rodriguez PR, Vazquez-Guzman G, Perez-Bustos GO, Sosa-Zuñiga JM, Aztatzi-Pluma D, Lopez-Nuñez AR, Rodriguez-Cortes CJ.
Analysis and Improved Behavior of a Single-Phase Transformerless PV Inverter. *Machines*. 2023; 11(12):1091.
https://doi.org/10.3390/machines11121091

**Chicago/Turabian Style**

Martinez-Rodriguez, Panfilo R., Gerardo Vazquez-Guzman, Gerardo O. Perez-Bustos, Jose M. Sosa-Zuñiga, Dalyndha Aztatzi-Pluma, Adolfo R. Lopez-Nuñez, and Christopher J. Rodriguez-Cortes.
2023. "Analysis and Improved Behavior of a Single-Phase Transformerless PV Inverter" *Machines* 11, no. 12: 1091.
https://doi.org/10.3390/machines11121091