article · Processes
Photovoltaic grid-connected systems increasingly rely on transformerless inverters to cut costs, reduce physical size and weight, and boost efficiency. However, the lack of galvanic isolation in these devices can cause earth leakage currents that introduce electrical and safety hazards. Although the H8 transformerless inverter topology was developed to address this leakage, controlling it effectively under challenging conditions remains necessary. This research applies model predictive control to an H8 transformerless inverter connected to an electrical network through an LCL filter, taking grid weakness into account. A full discrete model incorporating the solar panel, boost converter, inverter, and control mechanisms was evaluated in simulations subjected to changes in solar irradiance. The model predictive control approach improved system performance and delivered high-quality injected power across both strong and weak grid conditions. The findings and system robustness were further confirmed using hardware-in-the-loop testing.
Expanding solar power requires inverters that are light, affordable, and safe to connect to electricity grids. Transformerless designs achieve these physical benefits but risk dangerous current leaks. Demonstrating that advanced predictive controls can safely regulate these systems, even in weak grids, supports more reliable and flexible integration of renewable power into existing electrical networks.
This work is relevant to manufacturers of solar inverters and grid-integration equipment seeking to deploy cost-effective transformerless designs. It directly enables safer power injection in areas with weak or unstable grid infrastructure. Having reached hardware-in-the-loop testing on an off-the-shelf digital signal processing kit, the technology represents applied and tested laboratory research, sitting a step away from full prototype field trials.
AI-generated from the published abstract. Always read the original work before citing.
There is increasing utilization of photovoltaic (PV) grid-connected systems in modern power networks. Currently, PV grid-connected systems utilize transformerless inverters that have the advantages of being low cost, low weight, a small size, and highly efficient. Unfortunately, these inverters have an earth leakage current problem due to the absence of galvanic isolation. This phenomenon represents safety and electrical problems for those systems. Recently, the H8 transformerless inverter was introduced to eliminate the earth leakage current. The present study proposes improving the performance of an H8 transformerless inverter using model predictive control (MPC). The inverter was supplied by PV energy and attached to the grid through an LCL filter. During system modeling, the grid weakness was identified. The discrete model of the overall system, including the PV panel, the boost converter, the H8 transformerless inverter, and the controllers, was derived. Then, the introduced H8 transformerless inverter system was simulated and analyzed by the Matlab/Simulink program. The proposed system response using MPC was tested under step disturbances in the PV insolation level. Moreover, the effect of the weak and strong grid operations was considered. The simulation results indicate that the MPC controller has better performance and high-quality injected power. Despite the excellent performance of the strong grid, the nearly weak grid performance is acceptable. Moreover, the Hardware-in-the-Loop (HIL) of the proposed system was implemented using the DSP target LaunchPadXLTMS320F28379D kit to validate the simulation results. Finally, the system performance under the parameter variations showed good robustness.
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DOI: 10.3390/pr10071243
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