Abstract
The Finite control set model predictive control (FCS-MPC) is recently introduced to control inverters without the modulation stage. The absence of the modulation stage gives an unpredictable performance of the control system. In this paper, the performance of FCS-MPC is assessed by comparing with PID control which is based on Scalar Pulse Width Modulation (PWM). The two control techniques are applied for load voltage regulation of the autonomous four-leg voltage source inverter (FLVSI). Practically, the predictive control requires a large number of calculations, resulting in high computation time and delay. In this paper, a new finite control set model predictive voltage control (MPVC) algorithm is proposed to predict the load voltages for 15 switching states instead of 16 switching states for reducing the computation time required for the control algorithm. Moreover, the algorithm is optimized by removing the repeated computations and the delay is compensated using the two-step prediction horizon principle. An accurate discrete-time state-space model of the autonomous FLVSI with output LC-filter is used for predicting the load voltages considering the neutral inductance and damping resistance of the LC filter. A simple PID control scheme with decoupled feedforward voltage and current loops is used in the DQ0 reference frame, while MPVC operates in the ABC reference frame. The simulation and experimental results are used to show the full assessment of the MPVC. The prominent outcomes show the ability of the proposed MPVC algorithm to provide high power quality under unbalanced and non-linear load conditions with high stability and robustness.
Highlights
Power converters are considered as the main electric power components in providing good power quality in various electric power systems [1]
VOLTAGE CONTROL LOOP In the voltage control loop, the PID-controller can be applied to provide the references for the current in the shunt element of the LC-filter according to the load voltage feedback: d C
The results show that the model predictive voltage control (MPVC) provides a faster dynamic response, compared to PID control
Summary
Power converters are considered as the main electric power components in providing good power quality in various electric power systems [1]. To assess the FCS-MPC performance, comparative analyses of MPVC and MPCC with the classical control techniques were carried out in the literature. A number of FCS-MPC algorithms are proposed in literature to reduce the switching frequency variation [22]. It is well known that the FCS-MPC algorithm should be implemented in short sampling time to achieve the required control performance [24]. As MPVC depends on the system model, an accurate system model is needed This algorithm uses a novel discrete-time model with considering the neutral inductance Ln and the damper resistance Rd of the LC-filter connected to the inverter. A full assessment of the FCS-MPC as a voltage control in comparison with the conventional control technique (PID-control) with considering robustness analyses.
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