Grid disturbance in photovoltaic inverter

This work investigates the specific response of a utility-scale PV inverter to grid voltage phase shift-type disturbances which sometimes occur during grid fault events. The role of the PV inverter's phase-locked-loop (PLL) is identified as important to modeling the response.

The mathematical model of a grid-connected photovoltaic inverter based on the VSG is built. The proposed control strategy provides the inverter with more disturbance attenuation and provides rotational inertia. The control strategy estimates and compensates the total disturbance and generates the reference active power and reactive power by ADRC.

In addition to fundamental differences in fault current capability compared to traditional synchronous generators, PV inverters characteristic response to abnormal conditions is a strong function of the inverter controls implemented to protect the PV inverter itself but also to safely integrate to the interconnected grid.

Grid-tied PV inverters also have the characteristics of tripping under grid events due to its settings. Disconnection or a dramatic reduction of real power delivered to the grid can occur during grid overvoltages and undervoltages, also during over/under frequencies .

In summary, the exponential expansion of grid-connected photovoltaic systems (GIPVS) presents a number of technological and economic challenges.

This paper presents a control strategy for grid-forming inverters, utilizing a cascaded dual-control scheme that integrates current and voltage controllers, along with an outer loop for regulating the injected active and reactive power. The proposed approach enhances system performance by addressing key challenges faced by grid-forming inverters.