A MPPT control strategy with variable weather parameter and no DC/DC converter for photovoltaic systems

• A MPPT strategy with variable weather parameter and no DC/DC converter for PV systems is proposed.
• A unified model of three basic DC/DC converters is proposed under certain conditions.
• The relationship between weather parameters and control signal has been found out.
• A structure of PV system to implement this new MPPT strategy is proposed.

In this paper, a unified model of three basic DC/DC converters is firstly proposed under certain conditions. This model is named as inductance–capacitor–diode (LCD) circuit and consisted of an inductance, a capacitor and a diode. Based on LCD circuit, a maximum power point tracking (MPPT) control strategy with variable weather parameter is proposed for photovoltaic (PV) generation systems with DC bus. In this strategy, through using LCD circuit instead of DC/DC converter, the MPPT performance of PV system is not influenced by the choice of different DC/DC converter topologies and the configuration of PV system is simplified, which makes the overall cost lower and the system integration, modularization and miniaturization more convenient. Finally, the accuracy of LCD model, and the feasibility and availability of proposed MPPT control strategy are verified by some simulated experiments conducted under random weather conditions; the effect of non-uniform weather on proposed MPPT strategy is tested by some experiments under non-uniform weather conditions; the output transient-state performance of proposed MPPT strategy is analyzed by one experiment under a varying irradiance condition and the performance comparison with conventional P&O method is made by another experiment under a given weather condition.