Maximum power extraction and DC-Bus voltage regulation in grid-connected PV/BES system using modified incremental inductance with a novel inverter control

Abstract

Low ripples and variations in the DC-Bus voltage in single-phase Photovoltaic/Battery Energy Storage (PV/BES) grid-connected systems may cause significant harmonics distortion, instability, and reduction in power factor. The use of short-life electrolytic capacitor on the DC-Bus is considered a standard way for reducing these ripples and variations because of its large capacitance but results in short lifetime of the inverter. Replacing large electrolytic capacitors with small film capacitors can extend the lifetime of a PV/BES grid-connected system because small film capacitors have longer lifetime than large electrolytic capacitors. These film capacitors have low capacitance, which causes severe oscillations in the output current, and voltage drop due to huge ripples on the DC-Bus voltage. In this research, the main goal is to eliminate the output current ripples and voltage fluctuations associated with employing film capacitors. First, a modified incremental conductance (MIC) technique is proposed for tracking the maximum power by controlling the duty ratio of the DC-DC boost converter. Second, for the first time, a simple and novel d-q current regulation technique, which employs flowchart decision logic, is used in the DC-Bus control system for both the PV power system and the state of charge (SOC) of the BES. In this case, the DC-Bus controller is characterized by a cost-effective implementation because of its low sampling frequency. Although the presented approaches are successful in eliminating voltage distortion and fluctuations, they have unacceptable dynamic performance. Therefore, to improve the dynamic performance, BES was used to maintain a reliable and stable harvest from PV modules for varying loads while also increasing the dynamic performance of the overall system. The proposed PV/BES grid-connected systems, which employs a small 10-µF bus capacitor, is simulated and connected to the grid (230 V, 50 Hz). The DC-Bus voltage overshoot, undershoot and the total harmonics distortion (THD) of the output current for the proposed MIC are (1 V), (2.5 V) and (less than 5%), respectively. The average time response under rising radiation to track the global peak for MIC, traditional incremental conductance and variable step size incremental conductance are 1.403 s, 1.501 s and 1.113 s respectively. The obtained findings demonstrated the efficacy and superiority of the proposed d-q current control and MIC technique.

Stability analysis and improvement based on virtual impedance for electrolytic capacitor‐less DC multi‐port converter

“…This is because the gain of the out-loop controller is significantly larger than that of the inner-loop controller. So, there is G v G i G ud ≫ G id G i ≫ 1 and the Equation ( 10) can be simplified to Equation (11). In Equation (11), Z oo and G ud are the transfer functions of the ES converter; therefore, we only need to design the Z vir to change G zvir .…”

“…Consequently, the large electrolytic capacitors are replaced by the small film capacitors owing to the advantages in operating time and stability of the small film capacitors. However, the capacity per unit volume of small film capacitors is lower than that of large electrolytic capacitors, leading to enhanced coupling of each converter which affects the system stability [10,11]. Therefore, analyzing and improving the stability of electrolytic capacitorless DC multi-port converters are of vital significance.…”

A High Speed MPPT Control Utilizing a Hybrid PSO-PID Controller under Partially Shaded Photovoltaic Battery Chargers

“…These methods can be roughly divided into the following three categories: (1) conventional, (2) soft computing, and (3) hybrid MPPT methods. The traditional methods include incremental conductance (INC) [3], hill climbing (HC) [4], and perturbation and observation (P&O) [5]. These conventional methods are ineffective during PSCs because of the multiple-peak power phenomena present in the power-voltage or current-voltage (P-V or I-V) characteristic curves.…”

Dead-time compensation in three-phase grid-tied inverters using LQG multivariable control

“…Moreover, according to the IEEE 1547 standard, a Power Factor (PF) equals to or more than 0.8 is required for the grid-tied inverter at the Point of Common Couplings (PCC). A lagging PF supports the utility grid in terms of the reactive power 1 , 2 .…”