Performance Improvement for Two-Stage Single-Phase Grid-Connected Converters Using a Fast DC Bus Control Scheme and a Novel Synchronous Frame Current Controller

Bingzhang Li,Xi Chen,Shenghua Huang

doi:10.3390/en10030389

Bingzhang Li, Xi Chen + Show 1 more

Open Access

https://doi.org/10.3390/en10030389

Copy DOI

Journal: Energies	Publication Date: Mar 18, 2017
Citations: 14	License type: CC BY 4.0

Affiliation: Huazhong University of Science and Technology

Abstract

Two-stage single-phase grid-connected converters are widely used in renewable energy applications. Due to the presence of a second harmonic ripple across the DC bus voltage, it is very challenging to design the DC bus voltage control scheme in single-phase grid-connected inverters. The DC bus voltage controller must filter the ripple and balance a tradeoff between low harmonic distortion and high bandwidth. This paper presents a fast DC bus voltage controller, which uses a second order digital finite impulse response (FIR) notch filter in conjunction with input power feedforward scheme to ensure the steady-state and dynamic performance. To gain the input power without extra hardware, a Kalman filter is incorporated to estimate the DC bus input current. At the same time, a modulation compensation strategy is implemented to eliminate the nonlinearity of the grid current control loop, which is caused by the DC bus voltage ripple. Moreover, a novel synchronous frame current controller for single-phase systems is also introduced, and its equivalent model in stationary frame has been derived. Simulation and experimental results are provided to verify the effective of the proposed control scheme.

Highlights

Renewable energy is the key to future global sustainability
The main task of the second stage is to ensure that all of the power extracted by the first stage is transferred to the grid stably and smoothly [2,3]
To eliminate the nonlinear section of grid current control system, which is caused by the DC bus voltage ripple, a modulation compensation strategy is introduced

Summary

Introduction

Renewable energy is the key to future global sustainability. Two-stage converters are widely used for interfacing renewable energy resources with the utility grid. The first stage is typically a DC-DC converter for photovoltaics (PVs) or an AC-DC rectifier for wind turbines (WTs) [1]. The first stage performs maximum power point tracking (MPPT) and boosts the input voltage into an appropriate level for the second stage. The main task of the second stage (a DC-AC inverter for most systems) is to ensure that all of the power extracted by the first stage is transferred to the grid stably and smoothly [2,3].

Methods

Results

Conclusion