Constrained decoupled power predictive controller for a single‐phase grid‐tied inverter

Abstract

This study presents a decoupled active and reactive power control technique, for a single-phase grid-tied inverter, using model predictive control (MPC). The proposed technique does not use conventional phase-locked loop, pulse-width modulation nor a synchronisation transform, which makes the control algorithm well suited for an all-digital implementation. The proposed controller minimises the number of switching state transitions required to control the grid-side current while simultaneously constraining the harmonics distortions and protecting the inverter from overcurrent condition. In this study, the switching frequency is reduced by using a look-up table to minimise the number of switching state transitions, which helps lowering down the switching losses. The proposed technique uses an adaptive weight factor which gives more priority to commanded power tracking during transient, and minimises the tracking error and switching frequency in steady state while constraining the harmonics distortion. This method improves the tracking performance as well as reduces the switching losses by minimising the switching frequency compared to the MPC with fixed weight factor and conventional decoupled power control. Thus, the outcome of proposed controller is a constraint multi-objective optimisation between the switching frequency reduction and grid-side current harmonics in terms of cost function with weighting factor. Note: Method 1-traditional multi-loop PI-based power control method. Method 2, case 1-proposed controller with weight factor as 0. Method 2, case 2-proposed controller with weight factor as 0.02. Method 2, case 3-proposed controller with weight factor as 0.04.

Performance of model predictive control approach for single‐phase distributed energy grid integration with PQ control

“…The PQ theory was extended to 1-Φ systems [6,7,17,27,33] to control the operation of 1-Φ grid connected inverters. The instantaneous active and the reactive power injected to the grid are computed using (6) and (7) in the (α−β) reference frame…”

“…In the MPC approach, the future behaviour of the system is predicted over a finite time frame such that optimum future control action is applied to the system to achieve specific goal function [3,4]. The algorithm is repeated at every sampling period [5][6][7][8]. Finite control set-MPC (FCS-MPC) approach is more convenient to apply with power electronics converters such that future system behaviour is computed only for the discrete switching states of the converter.…”

“…In this study, the concept of FCS-MPC is applied for 1-Φ grid connected inverter working under instantaneous active and reactive power control. In direct PQ control strategy, the instantaneous active and reactive power are computed from the ac quantities (grid voltage and currents) resolved into equivalent two-phase system either in the stationary reference frame α−β coordinates [6,7,[27][28][29][30][31] or in d-q coordinates [29,30,32]. However, in the case of 1-Φ systems, such quadrature components do not exist.…”

State of the Ability in Research on Microgrid Hybrid Energy Systems

“…In [158], a novel model predictive control algorithm is proposed to lessen the number of calculations for multi-level cascaded H-bridge inverters and there are only three voltage vectors are used for calculation irrespective of the level of cascaded H-bridge inverters. In [159], a decoupled reactive and active power control method are presented for a grid-connected singlephase inverter by using model predictive control scheme. The controller reduces the switching state changes number essential to control the current whereas at the same time obliging the harmonics distortions and caring the inverter from overcurrent situation.…”

Model Predictive Voltage Control with Optimal Duty Cycle for Three-Phase Grid-Connected Inverter

“…For this reasons, inverter control plays a significant role in the performance of the grid-tied inverters system. Therefore selecting a better power converter and better control method can lead to efficient system operation and better performance with less total harmonic distortions to achieve better grid current quality [3,4]. Three-phase inverter with output LCL filter connected to the grid is one of the most popular applications in the power systems to transfer DC voltage source to a symmetrical three-phase AC sinusoidal voltage.…”