Optimal Design of Modern Transformerless PV Inverter Topologies

Abstract

The design optimization of H5, H6, Neutral Point Clamped, Active-Neutral Point Clamped and Conergy-NPC transformerless Photovoltaic inverters is presented in this paper. The components reliability in terms of the corresponding malfunctions, affecting the Photovoltaic inverter maintenance cost during the operational lifetime period of the Photovoltaic installation, is also considered in the optimization process. According to the results of the proposed design method, different optimal values of the Photovoltaic inverter design variables are derived for each Photovoltaic inverter topology and installation site. The H5, H6, Neutral Point Clamped, Active-Neutral Point Clamped and Conergy-NPC Photovoltaic inverters designed using the proposed optimization process feature lower Levelized Cost Of generated Electricity and lifetime cost, longer Mean Time Between Failures and inject more Photovoltaic-generated energy into the electric grid than their non-optimized counterparts, thus maximizing the total economic benefit obtained during the operational time of the Photovoltaic system.

Reliability Assessment of Transformerless PV Inverters considering Mission Profiles

“…For example, the Conergy neutral point clamped (NPC) transformerless PV inverter is based on the multilevel power converter technology [12,20]. However, only the FB inverter with a bipolar modulation scheme (FB-Bipolar), the H6 inverter, and the HERIC inverter are assessed in terms of reliability.…”

“…Till now, a vast of transformerless PV inverters have been developed [13][14][15][16][17][18][19][20], and many of those topologies have been successfully commercialized in residential PV applications, where size and efficiency are the main concerns. However, "transformerless" are also required to minimize the leakage current injections for safety due to the removal of the galvanic isolation.…”

“…This is typically achieved by either developing a special suitable modulation scheme or adding extra power switching devices [18]. For instance, in [19,20], optimization approaches have been proposed to improve the performance of transformerless PV inverters, while, in [12][13][14], additional power switching devices have been introduced to the traditional full-bridge PV inverter. However, such software or hardware modifications will alter the power loss distributions on the power switching devices, thus contributing to uneven thermal loading in the PV inverters.…”

A Modified Single-Phase Transformerless Z-Source Photovoltaic Grid-Connected Inverter

“…H5 and H6 belong to the dc-decoupling topology family. The H5 topology, which is used in SMA (SMA Solar Technology AG) commercial converters, adds only one switch when compared to full-bridge (FB) inverters [14]. The H6 topology, which is proposed in [15], symmetrically adds two additional switches to the FB inverter.…”

A New PWM Strategy for Grid-Connected Half-Bridge Active NPC Converters With Losses Distribution Balancing Mechanism

“…Hence, they have specific needs such as maximum profitability through high efficiency, long lifetime, low prices, small volume, and safety [1], [2]. In order to improve the efficiency of household PV inverters and lower the system prices, isolation transformers used in the past to interface the PV system with the electric grid in order to provide higher safety and lower leakage current is typically not present in the new generation of PV systems.…”