Model-Based Active Damping Control for Three-Phase Voltage Source Inverters With LCL Filter

Abstract

Abstract-This paper presents a robust model-based active damping control in natural frame for a three-phase voltage source inverter with LCL filter. The presence of the LCL filter complicates the design of the control scheme, particularly when system parameters deviations are considered. The proposed control method is addressed to overcome such difficulties and uses a modified converter model in an state observer. In this proposal, the converter model is modified by introducing a virtual damping resistor. Then, a Kalman filter makes use of this model to estimate the system state-space variables. Although the state estimates do not obviously match the real world system variables, they permit designing three current sliding-mode controllers that provide the following features to the closed loop system: a) robust ande active damping capability like in the case of using a physical damping resistor, b) robustness because the control specifications are met independently of variation in the system parameters, c) noise immunity due to the application of the Kalman filter, and d) power loss minimization because the system losses caused by the physical damping resistor are avoided. An interesting side effect of the proposed control scheme is that the sliding surfaces for each controller are independent. This decoupling property for the three controllers allows using a fixed switching frequency algorithm that ensures perfect current control. To complete the control scheme, a theoretical stability analysis is developed. Finally, selected experimental results validate the proposed control strategy and permit illustrating all its appealing features.

Variable Structure Control for Three-Phase LCL-Filtered Inverters Using a Reduced Converter Model

“…(4)). For this reason, and in order to eliminate these interferences between controllers, the neutral point voltage expression is not considered in the reduced model [12]. 2) In order to achieve active damping dynamics, the model only consideres the inverter-side current state variable.…”

“…[12]. Due to the fact that the grid current tracks only the positive sequence of the PCC voltage, the current amplitude is balanced during the voltage sag.…”

“…These controllers are usually based on a state observer where an accurate power converter model is used to estimate the state variables. An interesting solution with a high robustness against grid inductance variations is presented in [12]. Here, a virtual resistor is introduced in the converter model in order to emulate a damping resistor.The main advantage of this work is the use of sliding mode control (SMC), which provides a high robustness against system parameters deviations and external disturbances.…”

“…As a comparison with other previous SMC methods [12], [14], [15], the use of a reduced model allows to stabilize the system. The main advantage is that the computational time used by the algorithm is clearly reduced and as a consequence the maximum switching frequency can be increased.…”

LCL-resonance damping strategies for grid-connected inverters with LCL filters: a comprehensive review

“…To minimize the number of sensors for multi-state feedback control, estimation algorithms should be used. Recently, studies in [76,77] and [78][79][80][81][82][83] separately gave some good examples for slide model control and full-state feedback control. Usually, sampling and control are implemented in digital signal processing (DSP).…”