Low Frequency Ripple Reduction in Input DC Current and AC Line Currents With 240<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> Clamped Space Vector PWM in Grid-Connected Photovoltaic Converters

Abstract

240$^\circ$-Clamped Space Vector PWM (240CPWM) is a lowest switching loss PWM method in cascaded architecture of DC-DC stage followed by DC-AC stage that reduces the switching loss by 85% in the DC-AC stage at unity power factor as compared to conventional space vector PWM (CSVPWM). 240CPWM requires unique six-pulse dynamically varying DC link voltage instead of constant DC link voltage which introduces low frequency harmonics predominantly around six times the fundamental frequency ($6f_{1}$). These low frequency harmonics distort the input DC current and AC line currents. Moreover, they change the operating point of maximum power point tracking (MPPT), reducing the efficiency of grid-connected Photovoltaic (PV) converter. In this article, three topologies are proposed to reduce the low frequency ripple in input DC current and AC line currents in three-phase grid-connected PV systems with 240CPWM. A three-phase 1.5 kW Silicon Carbide based hardware prototype in grid-connected mode is developed to validate the performance of the proposed topologies. Experimental results show that the maximum reduction of 68.8% in ($6f_{1}$) harmonic component in DC input current is achieved in active filter based Topology II without any significant detrimental effect on THD in AC line currents and inverter efficiency as compared to standard topology.

Keywords

• Photovoltaic (PV)
• grid-connected converter
• low frequency harmonics
• DC input current
• $^\circ$ -Clamped Space Vector PWM (240CPWM)%22%2C%22default_operator%22%3A%22AND%22%7D%7D%7D"> 240<named-content xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" content-type="math" xlink:type="simple"> <inline-formula> <tex-math notation="LaTeX">$^\circ$</tex-math> </inline-formula> </named-content>-Clamped Space Vector PWM (240CPWM)
• dynamic DC link