Analysis and Design of Grid-Connected Photovoltaic Systems With Multiple-Integrated Converters and a Pseudo-DC-Link Inverter

Abstract

An architecture of multiple-integrated converter modules sharing an unfolding full-bridge inverter with a pseudo DC-link (MIP) is proposed for grid-connected photovoltaic (PV) systems in this paper. The proposed configuration can improve the power conversion, the control circuit complexity and the cost competitiveness. The proposed MIP is composed of distributed flyback dc-dc converters (DFC) and an unfolding full bridge inverter with an ac filter. The DFCs can eliminate the shading effect by using the individual maximum power point tracking (MPPT). In conventional flyback-type single-phase utility interactive inverter, discontinuous conduction mode (DCM) and boundary conduction mode (BCM) are popular because of the inherent constant current-source characteristics more desirable for grid-connection and of the simple procedures for the controller design. However, the operating mode suffers from a large current stress of the circuit components, which leads to the low power efficiency. To avoid this, the DFCs operates under Continuous Conduction Mode (CCM) that allows reduced current stresses and increased power efficiency, as well as the low material cost. The current control loop of the converters employ primary-side regulation contributing to improvement of dynamics as well as the cost reduction significantly due to the elimination of high linearity photo-coupler device. Development of a new DC current loop that maintains the level of DC current injection into the grid within the levels stipulated by IEEE 1547 will be dealt as well. The performance validation of the proposed design is confirmed by experimental results of a 200W hardware prototype.

Influence of A/D Quantization in an Interpolated DFT Based System of Power Control with A Small Delay

“…Photovoltaic systems used for the solar energy conversion into electricity are constantly improved in the hardware and software [2][3]. One of the basic elements of the photovoltaic system is an inverter that is used to convert DC current and voltage obtained from photovoltaic cells to AC current and voltage with specified parameters.…”

A comprehensive review of photovoltaic systems

“…An FC topology is used by Ye Zhao et al [68], to analyse the PV system fault. A distributed FC with tracking control is presented in [77] to reduce the losses due to shading.…”

Interleaved Flyback Micro-inverter with Primary Side Current Control for PV Application

“…Due to the existence of a non-minimum phase (NMP) zero [8] and system dynamic issue [9] in CCM, the topology has instead been designed to operate in DCM. In exchange for simple dynamic, there exist several drawbacks to complicate the topology in order to make DCM practical.…”

“…The control problem for CCM, however, has recently been overcome by using a simple analogue controller [8,12] for the current controller. Another method is sampling the output from grid side filter instead [9], making it possible to control the system using digital controller.…”

“…Even though the system is designed under CCM operation, it also works very well in DCM during grid voltage polarity shifting period [12]. These designs knowingly improve the topology efficiency, but distortions in the output current are also there [8,9,12]. This paper offers a topology for interleaved flyback microinverter sharing two common switches and grid-side filter with other converters from different panels.…”