Observer-Based State-Space Current Controller for a Grid Converter Equipped With an LCL Filter: Analytical Method for Direct Discrete-Time Design

The paper presents a controller design for grid-connected inverters (GCI) with very small dc-link capacitance that are coupled to the grid via an LCL filter. The usual controller designs would fail and result in instability. The proposed controller has a cascaded structure with a current controller as inner control loop and an outer dc-link voltage controller. The controller design is performed in discrete time and it is based on a detailed stability analysis of the dc-link voltage controller to determine the controller parameters which guarantee stability for all operating points. The inner loop is a state-feedback current controller that is designed based on the discrete linear-quadratic regulator (DLQR) theory. An additional integral error feedback assures steady-state accuracy of the current control loop. The simulation and experimental results validate performance and stability of proposed controller design.

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Positive- and Negative-Sequence Current Controller With Direct Discrete-Time Pole Placement for Grid-Tied Converters With LCL Filter

IEEE Transactions on Power Electronics ◽

10.1109/tpel.2016.2621754 ◽

2017 ◽

Vol 32 (9) ◽

pp. 7207-7221 ◽

Cited By ~ 30

Author(s):

Diego Perez-Estevez ◽

Jesus Doval-Gandoy ◽

Alejandro G. Yepes ◽

Oscar Lopez

Keyword(s):

Discrete Time ◽

Pole Placement ◽

Lcl Filter ◽

Negative Sequence ◽

Current Controller ◽

Negative Sequence Current

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A novel current controller design for grid-integrated PV inverter system

SN Applied Sciences ◽

10.1007/s42452-021-04290-4 ◽

2021 ◽

Vol 3 (3) ◽

Author(s):

Ayaz Ahmad ◽

L. Rajaji ◽

A. Iqbal

Keyword(s):

Controller Design ◽

Vital Role ◽

Current Feedback ◽

Lcl Filter ◽

Design Algorithm ◽

Grid Voltage ◽

Pv Inverter ◽

Current Controller ◽

Experimental Implementation ◽

Grid Connected Inverter

AbstractDistributed generators are playing a vital role in supporting the grid in ever-increasing energy demands. Grid code regulation must be followed when integrating the photovoltaic inverter system to the grid. The paper investigates and analyzes a controller model for grid-connected PV inverters to inject sinusoidal current to the grid with minimum distortion. To achieve better tracking and disturbance rejection, a DSP-based current controller is designed with LCL filter. The controller gets the current feedback from the grid, compares it with reference current, and calculates duty cycle to generate PWM pulses to trigger H-bridge converters. The grid voltage is loaded to the initial value in proposed PR controller to ensure the initial inverter voltage to match the grid voltage. The paper presents a novel current controller algorithm for grid-connected inverter system, and simulation is done. A detailed analysis has been carried out to validate the proposed design algorithm. Experimental implementation of the current controller in the DC/AC converter circuits with an LCL filter is done for 5.4 kW to validate and match the simulation model.

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