Model-Based Control for a Three-Phase Shunt Active Power Filter

Abstract

Abstract-This paper presents a robust model-based control in natural frame for a three-phase shunt active power filter. For the proposed control method a linear converter model is deduced. Then, this model is used in a Kalman filter in order to estimate the system state-space variables. Even though the states estimation do not match the variables of the real system, it has allowed to design three sliding mode controllers providing the following features to the closed loop system: a) robustness due to the fact that control specifications are met independently of any variation in the system parameters; b) noise immunity, since a Kalman filter is applied; c) a lower THD of the current delivered by the grid compared with the standard solution using measured variables; d) the fundamental component of the voltage at point of common coupling is estimated even in the case of a distorted grid; and e) a reduction in the number of sensors. Thanks to this solution the sliding surfaces for each controller are independent. This decoupling property of the three controllers allows using a fixed switching frequency algorithm that ensures a perfect current control. Finally, experimental results validate the proposed control strategy and illustrate all its interesting features.

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

“…This algorithm is presented in [14], [15] and leads to obtain a quasi-fixed switching frequency. Finally, the generated control signal, is applied to control the phase-leg a of the VSI, generating a current without oscillations.…”

“…This fact allows to reduce the current distortion even in the case of a highly distorted grid [15], [16]. On the other hand, the existence condition of a sliding mode controller is given by the following inequality:…”

“…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.…”

Finite Control Set Model Predictive Control for a Three-Phase Shunt Active Power Filter with a Kalman Filter-Based Estimation

“…The main task of a shunt active power filter is to compensate such harmonics, and as a consequence to reduce, as much as possible, the total harmonic distortion (THD) of the currents injected to the grid [1]. Different methods have been presented in the past in order to improve the grid power quality, such as passive filters or active power filters [2][3][4]. Usually, the use of passive power filters to suppress the current harmonics has been considered in the past due to their low cost.…”

“…Several techniques addressed to control these kind of power converters have been presented in the literature, such as sliding mode control (SMC) [3], optimal control [5] and model predictive control (MPC) [6][7][8]. Currently, and thanks to the potential of digital signal processors (DSPs), the MPC is a promising control method and has several benefits such as fast tracking response, a high control bandwidth and a very easiest way to include system nonlinearities and constraints [9].…”