Integration of power decoupling buffer and grid-tied photovoltaic inverter with single-inductor dual-buck topology and single-loop direct input current ripple control method

https://doi.org/10.1016/j.ijepes.2020.106423Get rights and content

Highlights

  • A new configuration of single-phase single-stage dual-buck PV inverter with active power decoupling buffer is proposed.

  • Single-inductor dual-buck topology with series connected diodes has been adopted.

  • A novel single-loop direct input current ripple confinement control method is proposed.

Abstract

Dual-buck inverters feature some attractive merits, such as no reverse recovery issues of the body diodes, free of shoot-through, high efficiency and low leakage current. However, volume and weight of the system, power density must be reconsidered in the dual-buck based single-phase grid-tied photovoltaic (PV) inverter, because its twice inductor capacity and bulky electrolytic capacitor for the inherent double-frequency ripple power decoupling. Thus, a new integration of active power decoupling buffer and grid-tied photovoltaic inverter with single-inductor dual buck topology is proposed in this letter. The working principle is explained, and a new single-loop direct input current ripple control method for active power ripple decoupling buffer is proposed. Finally, the effectiveness is verified by experimental results.

Introduction

The new trend for grid-tied PV inverter is toward low cost, high conversion efficiency, high maximum power point tracing (MPPT) efficiency, high reliability, long lifetime, low ground leakage current and low grid current distraction [1]. Among the various topologies, PV inverter with dual-buck topology exhibits distinct merits of high reliability, high efficiency, and low leakage current, becomes a research hotspot in recent years [2], [3], [4]. However, the use of more inductors than in a traditional full-bridge inverter is preventing from achieving high-power density of this system. Besides, for single-phase PV system, the inherent double-line-frequency power ripple introduced into, it hinders the performance and efficiency, reduces the MPPT accuracy, and deteriorates the power quality on both sides of the PV inverters [5].

To solve these problems, several studies have been conducted from various aspects. In Ref [6], a single-inductor dual-buck topology is proposed, the inductance can be full used, at the price of the large increasing of conducting loss, thus, the conversion efficiency is affected. Adopting coupled inductors in full bridge inverter, Ref [7], [8] obtained a result of volume and weight reduction. However, design and fabrication of coupled inductors are not easy tasks. For the power ripple decouple problem, it is commonly addressed by the use of a large capacitor, typically electrolytic [9], which has a limited lifetime [10], and contradicts the high power density. Hence, active power decoupling buffer (APDB) with its ripple cancellation

control strategy has been suggested to handle the low frequency power ripple, in Ref [10], [11], [12], typical APDB topologies (symmetrical half-bridge or double-inductor dual-buck) are shown in Fig. 1(a). For the aspect of system optimization, APDB can increase the power density, while reduced size of passive components, becomes the most prominent technology.

In this letter, a new configuration of single-phase single-stage dual-buck PV inverter with APDB, based on single-inductor dual-buck topology with series connected diodes is proposed, as shown in Fig. 1(b). Comparing with the the traditional single-stage single-phase converter with APDB, as shown in Fig. 1(a), advantages of the single-inductor dual -buck inverters, a lower conducting loss, make full use of the inductance can be retained. Farther more, to save a voltage sensor, simplifying ripple confinement control structure, a novel single-loop direct input current ripple control method is then proposed. It entirely different from the dual-loop control presented in [13], [14], and no frame transformation or polarity determine logic operation is needed, as presented in [15]. Finally, the proposed scheme is verified through experimental results for a 1 kVA inverter prototype.

Section snippets

Proposed Single-phase PV inverter with new topology of Single-Inductor Dual-Buck

The new configuration of single-phase PV transformer-less grid-tied inverter, with its own power decoupling buffer, is shown in Fig. 1. In this PV system, single-inductor dual-buck topology is adopted, to decrease the volume and weight of the system, whilst retaining these all advantages. The main inverter circuit consists of a full bridge with one bidirectional leg, two unidirectional switching legs, and APDB which is composed of a unidirectional switching leg and split-capacitors. Because of

Working principle of ripple compensation

Defining ug and ig denote the grid voltage and grid current, ω is the AC grid frequency, φ denotes the angel of grid current laying behind grid voltage, then:ug=Ugcosωtig=Igcosωt+φ

Supposing single-phase inverter works at the non-unitary power factor (PF), the instantaneous power on the AC grid side pac can be written as:pac=ugig=UgcosωtIgcosωt+φ=12UgIgcosφ+12UgIgcos2ωt+φ=pd+prWhere, pd and pr represent the DC power and AC pulsating power in the grid side of single-phase inverter, respectively.

Simulation results

Verification and comparison of traditional APDB topology (double-inductors dual-buck) and the proposed topology (single-inductor dual-buck), have been performed, by means of simulation model in the MATLAB/Simulink software. The parameters used for the simulation are shown in Table 1.

Fig. 8(a) shows the waveforms of grid voltage and grid current with the proposed topology and single-loop direct input current ripple control method. The grid current can be well regulated by the PR controller, and it

Conclusion

In this letter, a new configuration of single-phase single-stage dual-buck PV inverter combined with APDB is proposed and verified. Based on single-inductor dual-buck topology, this integration system reduces cost, increases power density, and may lead to improved MPPT accuracy for PV application. Additionally, a novel single-loop direct input current ripple mitigation control method is proposed. Unlike those used in conventional half-bridge active power decoupling buffer, only the input PV

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This work was supported by the National Natural Science Foundation of China under Grants 61863003, the Natural Science Foundation of Hunan Province of China under Grant no. 2018JJ3690.

References (15)

  • Joydip Jana et al.

    Elsevier’s Renewable and Sustainable Energy Reviews

    (May 2017)
  • M.N.H. Khan et al.

    Transformerless Inverter Topologies for Single-Phase Photovoltaic Systems: A Comparative Review

    IEEE J. Emerg. Sel. Top. Power Electron.

    (Mar. 2020)
  • Li Zhang et al.

    Two-stage Dual-buck Grid-tied Inverters with Efficiency Enhancement

  • Y. Zhilei et al.

    Two-switch dual-buck grid-connected inverter with hysteresis current control

    IEEE Trans. Power Electron.

    (Jul. 2012)
  • Wentao Wang et al.

    A modified reference of an intermediate bus capacitor voltage-based second-harmonic current reduction method for a standalone photovoltaic power system

    IEEE Trans. Power Electron.

    (Aug. 2016)
  • Hong Feng et al.

    Single Inductor Dual Buck Full-Bridge Inverter

    IEEE Trans. Ind. Electron.

    (Aug 2015)
  • J. Xie, F. Zhang, R. Ren, A novel high power density dual-buck inverter with coupled filter inductors. In: Proc. 40th...
There are more references available in the full text version of this article.

Cited by (0)

View full text