Abstract
The stable operating region of a photovoltaic (PV) cascaded H-bridge (CHB) grid-tied module level inverter is extended by adopting the hybrid modulation strategy. However, the traditional single hybrid modulation method is unable to regulate the DC-side voltage of each module precisely, which may aggravate the fluctuation of modules’ DC-side voltages or even cause the deviation of modules’ DC-side voltages under some fault conditions and, thus, degrade the energy harvesting of PV panels. To tackle this problem, a switching modulation strategy for PV CHB inverter is proposed in this paper. When the CHB inverter is operating in normal mode, the hybrid modulation strategy containing the zero state is adopted to suppress DC-side voltage fluctuation, thereby, improving the output power of PV modules. When the CHB inverter is operating in fault mode owing to failing solar panels, the hybrid modulation strategy without the zero state is utilized to make the DC-side voltages reach the references and, thus, maintain a higher energy yield under fault conditions. Experimental results achieved by a laboratory prototype of a single-phase eleven-level CHB inverter demonstrate both the feasibility and effectiveness of the proposed method.
Highlights
With the increasing demand for conversion efficiency during recent years, multilevel converter topologies have become more and more applied to the grid-connected PV generation system [1,2,3,4].Among all kinds of multilevel inverters, the cascaded H-bridge (CHB) has many advantages, such as modularization, simplicity, and high reliability, which makes it become the most attractive topology [5,6,7,8,9]
Under normal mode, the switching hybrid modulation strategy (SHMS) is able to effectively suppress the efficiency the CHB inverter compared with the under normal the SHMS DC-side is able voltage toofeffectively suppress the DC-side voltage fluctuation compared withmode, the Hybrid Modulation Strategy without the Zero State (HMSWZS), fluctuation compared with the HMSWZS, thereby improving the energy acquisition is able to effectively suppress the DC-side voltage fluctuation compared with the HMSWZS, thereby the energy acquisition of the PV module
CHB inverter operating in the fault mode, improving owing to failing solar the zero state is adopted to suppress DC-side voltage fluctuation, thereby improving the output
Summary
With the increasing demand for conversion efficiency during recent years, multilevel converter topologies have become more and more applied to the grid-connected PV generation system [1,2,3,4]. A new, improved MPPT method is presented in [18], which changes the working point of the over-modulated H-bridge unit to ensure that all H-bridge units work in the stable operation region to improve the stability margins of the system This will result in lower output power and make the system less-efficient. Once the CHB inverter is operating in fault mode, owing to failing solar panels, the HMSWZS is utilized to control the DC-side voltages to track the references, maintaining a higher energy yield under fault condition. With this method, the average output power of the PV modules will be improved both in the normal and fault modes.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
