Abstract
The parallel connection of multiple distributed energy resources with a common DC-link structure is typically used in grid-connected applications which enables flexible operation maximizing power production of the inverter system under various operation conditions. However, it has brought drawbacks for DC-link power decoupling with the requirement of a larger capacitor bank, faster voltage regulation, etc., to maintain a constant DC-link voltage which increases the overall size and cost. In this paper, a DC-link decoupling technique using a nonlinear control algorithm is proposed to perform rapid DC-link voltage regulation for multi-input grid-connected inverters. With the implementation of a nonlinear observer, the power fed into the DC-link from multiple inputs is estimated by the proposed control algorithm and can be rapidly compensated by the inverter minimizing the DC-link voltage fluctuation. The effectiveness of the proposed nonlinear power decoupling control algorithm is verified by comparing the DC-link performance with a conventional control algorithm through both simulation results on a MATLAB platform and experimental verification on a grid-connected inverter prototype.
Highlights
With the increasing environmental concerns, electricity demand and advancement of power electronics technologies, distributed energy resources (DERs) have been experiencing significant growth during last decades [1]–[3] and are playing more important roles in modern smart grid systems
Among all DERs, renewable sources such as wind [4] and photovoltaics [5] have already been as key parts in distributed power generation systems
Compared with conventional systems where each energy resource is equipped with a gridconnected inverter, the multi-input inverter has its advantages, such as: minimizing the use of switching components so that energy losses during power conversion is reduced; and flexible operation with internal power sharing capability which enables steady power generation to the utility grid even under the extreme input conditions
Summary
With the increasing environmental concerns, electricity demand and advancement of power electronics technologies, distributed energy resources (DERs) have been experiencing significant growth during last decades [1]–[3] and are playing more important roles in modern smart grid systems. In order to adapt the operation of these power estimation methods in the multi-input inverters, an improved power decoupling algorithm based on nonlinear power estimation is proposed and analyzed in this paper to reduce estimation errors and to minimize DC-link voltage fluctuations during rapid power variations. MULTI-INPUT INVERTER SYSTEM In order to design proposed power decoupling control algorithm on a practical inverter system with multiple input, the characteristics of the inverter system as well as the mathematical DC-link model are first discussed . In order to compensate the drawback in the multi-input inverter system with the advanced power decoupling control algorithm, the DC-link model which reflect the characteristics of this inverter system is required to design such controller. For the propose nonlinear observer design for a practical power conversion system, reasonable large gains h! and h" can be selected to achieve a desire observer performance and to minimize the unstable region and estimation oscillations
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