Page 54 - Renewable Energy Devices and System with Simulations in MATLAB and ANSYS

3 Overview of Single-

Phase Grid-Connected

Photovoltaic Systems

Yongheng Yang and Frede Blaabjerg

CONTENTS
Abstract ............................................................................................................................................41
3.1 Introduction .............................................................................................................................41
3.2 Demands for Grid-Connected PV Systems ............................................................................43
3.3 Power Converter Technology for Single-Phase PV Systems ..................................................44
3.3.1 Transformerless AC-Module Inverters (Module-Integrated PV Converters)..............44
3.3.2 Transformerless Single-Stage String Inverters ...........................................................47
3.3.3 DC-Module Converters in Transformerless Double-Stage PV Systems ....................50
3.4 Control of Single-Phase Grid-Connected PV Systems ...........................................................52
3.4.1 General Control Objectives and Structures.................................................................52
3.4.2 Grid Synchronization ..................................................................................................53
3.4.3 Operational Example ..................................................................................................58
3.5 Summary .................................................................................................................................60
References ........................................................................................................................................62

ABSTRACT
A continuous booming installation of solar photovoltaic (PV) systems has been witnessed world-
wide. It is mainly driven by the imperative demand of “clean” power generation from renewables.
Grid-connected PV systems will thus become an even more active player in the future mixed power
systems, which are linked together by a vast of power electronics converters and the power grid. In
order to achieve a reliable and efficient power generation from PV systems, more stringent demands
have been imposed on the entire PV system. It, in return, advances the development of the power
converter technology in PV systems. This chapter thus gives an overview of the advancement of
power electronics converters in single-phase grid-connected PV systems, being commonly used in
residential applications. Demands to single-phase grid-connected PV systems and the general con-
trol strategies are also addressed in this chapter.

3.1 INTRODUCTION
Traditional power generations based on fossil fuel resources are considered to be unsustainable in
long-term national strategies. This has been one of the main driving forces for an extensive instal-
lation of renewable energies like wind power, solar photovoltaic (PV) power, hydropower, biomass
power, geothermal power, and ocean power into public grids in the last decade [1, 2]. Among the
major renewables, solar PV power generation has continued to be expanded at a rapid rate over the
past several years, and it already plays a substantial role in electricity generation in some countries
[3]. As an example, approximately 7.9% of the annual electricity demand was covered by solar PV
systems throughout 2014 in Italy [3]. In Germany, the total installed capacity had reached 38.2 GW

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