Off-grid inverter changes output voltage

A common control method for off-grid inverters is multiple-loop control with a PI compensator. The output of the voltage loop is the reference value for the current loop. In this model, the common control method is utilized except that the voltage reference and sampling signal is the RMS value of output voltage.

We propose, in this paper, an advanced control strategies to enhance the efficiency and stability of grid-connected and off-grid photovoltaic (PV) systems. Utilizing a multilevel inverter and a DC/DC boost converter, we integrate a novel multi-objective control strategy that combines sliding mode control and LS-PWM techniques.

This study focuses on the optimization and control of a grid-connected photovoltaic system using a single-phase multilevel inverter. Single-phase inverters are increasingly favored for low and medium voltage applications due to their efficiency, cost-effectiveness, and compact size.

This achieves the goals of reducing harmonic distortion and adequately controlling active and reactive power . The sliding mode control strategy ensures the seven-level PWM inverter outputs voltage with a reduced harmonic ratio and injects sinusoidal current in phase with the grid voltage, maintaining unity power factor.

The multilevel inverter is also regulated to inject this maximum power into the grid, regardless of atmospheric conditions, and to control both active and reactive power, thus ensuring a unity power factor on the network side. This approach aligns with the methodologies discussed in, .

Flowchart of a conventional P&O MPPT method and the proposed technique of controlling intermediate circuit voltage and grid current for a photovoltaic system based on a symmetrical PWM inverter.