Adaptive DC-Link Voltage-Controlled PV Grid-Connected DTL-VSI With Reduced Switching Losses and Switching Frequency

This article discusses a photovoltaic (PV) grid-connected dual two-level voltage source inverter (GCDTL-VSI) to improve the power quality, reliability, and efficiency of the grid. In PVGCDTL-VSI, VSI-1 is employed to compensate the current-related power quality concern, while VSI-2 is employed to transfer real power to the load and grid. In the literature, the dc-link voltage maintains constant at the input terminal of VSI-1 under low-power injection. As a result, there will be significant switching losses and stress on the inverter switches. In the proposed method, VSI-1 with LC-filter, and an adaptive dc-link voltage control technique is used to alleviate the switching losses and stress on the inverter switches. In addition, the two-leg VSI that employs for supply real power to the load and grid instead of the conventional approach uses three-leg VSI. In PVGCDTL-VSI, a model predictive control (MPC) with a multiconstraint technique is used to generate the switching pulses, dc-link capacitor voltage balancing, and reduce switching frequency. To reduce the weighting factor control complexity, a technique for order preference by similarity to ideal solution (TOPSIS) approach is employed in PVGCDTL-VSI. To evaluate the effectiveness and performance of the PVGCDTL-VSI, simulation and experimental tests are carried out.

I. Introduction

Nonconventional energy resources, such as wind, tidal, geothermal, and photovoltaic (PV), are utilized in many applications as viable due to the increased need for traditional energy sources [1], [2]. One of the most common and promising energy source for supplying demand to a system is solar energy, which provides reliability and resilience [3], [4]. In the literature [5], a number of approaches are suggested to achieve the maximum power from PV panels. Among them, incremental conductance-based maximum power point tracking (MPPT) will be employed, since it is quick, precise, and simple to apply. To maximize power from the PV panels and maintain the required reference dc-link voltage at the inverter terminals, an incremental conductance approach is used to regulate the duty ratio of the boost converter. The proposed approach employs two-stage grid-connected PV system. The PV system operates MPPT at the first stage due to a change in the dc–dc converter’s duty ratio. In the second stage, a grid-connected voltage source inverter (GC-VSI) distributes power into the grid and load [6].