This paper presents an improved strategy in the field of predictive direct power control (PDPC) of the doubly fed induction generator (DFIG). The proposed strategy applies four voltage vectors in every period in order to have constant switching frequency and low current THD. The appropriate voltage vectors in each period are recognized when estimated duration times of selected active vectors are positive. The suggested technique shows excellent performance during transient and steady state conditions. The proposed PDPC can easily follow the power references under normal and abnormal voltage conditions even if the power references contain AC terms. Without any additional controller, the proposed technique could obtain smooth stator active and reactive powers or smooth electromagnetic torque, or could inject sinusoidal and balanced currents into the grid when the unbalanced voltage appears in DFIG stator windings. Simulation studies for this technique are carried out for 2 MW DFIG in Matlab Simulink environment under balanced and unbalanced grid voltage. The results of this technique under unbalanced grid voltage are compared to two other previous PDPC strategies. Comparisons show that the performance of the proposed strategy under unbalanced grid voltage is superior to the two other strategies.

Model-based predictive power control (MPPC) is a well-known and useful technique for control of electric drives and renewable energy generation systems. However, this strategy relies on the knowledge of accurate system models and parameter values and would otherwise lead to tracking errors in applications because of inevitable parameter uncertainties. Also, step delays in MPPC implementations have to be compensated to eliminate errors. This paper proposes a predictive control application to control active and reactive powers exchanged between the grid and the grid side converter (GSC) interfacing renewable energy sources such as wind farms or photovoltaic. The proposed MPPC minimizes the power tracking error based on a proposed cost function and the control system output is the voltage reference for the electronic converter that is converted into switching pulses by the modulation stage. The proposed control strategy is designed to eliminate tracking errors and has fixed switching frequency while featuring a fast-dynamic response, low current THD, and low computational burden. The method has been evaluated by using Matlab/Simulink environment and an experimental 5 kW grid-connected voltage source converter. Finally, the proposed MPPC method has been critically compared to the previous MPPC approaches.

This article presents an improved model-based predictive current control for a surface permanent magnet synchronous generator (SPMSG), where the dynamic response time can be adjusted according to the characteristics of the application and that can operate in the overmodulation region. Moreover, the steady-state errors typically observed in other model predictive controls (MPCs) due to the uncertainties of the system and errors in the parameter values are removed in the proposed MPC. The proposed MPC was tested for the nED100 wind turbine of Norvento in MATLAB/Simulink environment. Besides, it was assessed in an 8.7 kW SPMSG laboratory prototype. The simulation and experimental results indicate that the proposed MPC works properly in an overmodulation region and the desired dynamic response time is achieved whereas the switching frequency is constant.

A predictive power control for a four- switch three phase (FSTP) grid side converter (GSC) of doubly fed induction generators (DFIG) is presented. In this new method, three voltage vectors are employed to ensure that the proposed strategy maintains the switching frequency constant while the ripple of the active and reactive powers of the GSC is minimized. Moreover, a compensation power to eliminate the DC voltage deviation in the capacitors is presented, and it can be estimated without using any low pass filter. The proposed method can be implemented in a microcontroller very easily. Firstly, the proposed strategy has been evaluated in Matlab/Simulink environment and afterwards it was implemented in a laboratory prototype. The simulation and experimental results of the proposed predictive strategy show that it is capable to suppress the DC link voltage offset, featuring balanced currents and a fast dynamic response while the GSC current THD is low. Furthermore, the performance of the proposed method is compared to two other predictive controls. The results prove that the proposed method is well suitable for the FSTP GSC of a DFIG.

This paper presents a model predictive current control (MPCC) for three-phase four-switch converters (TPFSC) connected to surface permanent magnet synchronous generators (SPMSGs) in oscillating water column (OWC) wave energy plants, that brings some benefits over the existing control methods used in this type of plants. The proposed MPCC for TPFSC follows the current references with great accuracy whereas the switching frequency of the IGBTs is fixed and low. This method minimizes the current reference tracking error, and its fast response makes it suitable for the power take-off (PTO) systems present in wave energy converters (WECs). Furthermore, the system features a fast capacitor voltage offset suppression control. The dynamic performance and the voltage offset control of the proposed strategy for TPFSC feeding a SPMSG is evaluated in Simulink environment. Later, experimental studies are carried out on an 8.7 kW laboratory SPMSG prototype. Finally, the capability of the proposed method to harvest the maximum energy from irregular waves is assessed using an OWC power plant emulator.