Finite state model predictive control (MPC) has been recently applied to several converter topologies, as it can provide many advantages over other MPC techniques. The advantages of MPC include fast dynamics, multitarget control capability, and relatively easy implementation on digital control platforms. However, its inherent variable switching frequency and lower steady-state waveform quality with respect to standard control, which includes an appropriate modulation technique, represent a limitation to its applicability. Modulated model predictive control (M² PC) combines all the advantages of MPC with the fixed switching frequency characteristic of pulse-width modulation algorithms. The work presented in this paper focuses on the indirect matrix converter (IMC), where the tight coupling between rectifier stage and inverter stage has to be taken into account in the M²PC design. This paper proposes an M²PC solution, suitable for IMC, with a switching pattern that emulates the desired waveform quality features of space vector modulation for matrix converters. The switching sequences of the rectifier stage and inverter stage are rearranged in order to always achieve zero-current switching on the rectifier stage, thus simplifying the current commutation strategy.

The matrix converter (MC) with an LC filter at source side suffers from system instability, thereby requiring damping control. To improve system stability, this paper proposes a novel active damping control strategy. First, the method of generating space vector modulation signals is improved, in order to make the amplitude and phase angle of input currents directly controllable without affecting the priority of output voltage control. Then, the proposed strategy, which is realized by injecting damping signals into input reference currents, is presented. In this way, the proposed strategy can suppress the oscillations in source currents directly. Besides, it is effective with source voltages or capacitor voltages sampled for modulation, regardless of the operation mode of MC. Furthermore, it is applicable to most of existing modulation algorithms. Finally, experimental results of four-quadrant operation on a 2.4-kW prototype illustrate that, under the condition of the same parameters, the proposed active damping control strategy performs better than passive damping control in filtering and the same in damping at source side, without sacrificing the driving performance at output side.

A matrix converter (MC) with model predictive control (MPC) based on the source reactive power control usually fails to show sinusoidal source currents. The analysis presented in this paper shows that this common combination of converter and control has the inherent inability to eliminate some harmonics in the source currents, even with additional passive or active damping control. Direct source current control can be implemented to give sinusoidal source currents and intrinsic active damping. However, the issue of steady-state error in output currents then arises, as the MC topology does not allow of the independent control of source and output currents. Therefore, feedback control of load active power is proposed to address this issue without degrading the fast dynamic performance. Benefiting from the direct source current control, a simplified implementation is also proposed to decrease the number of candidate switching states from 27 to 5, which significantly reduces the computational burden. Experimental results have verified the theoretical analysis and the effectiveness of the proposed control scheme.

It is generally considered that feedback control of input currents in the matrix converter (MC) is hard to be realized due to the coupling of input control and output control, which reduces the degree of freedom and robustness. Moreover, under unbalanced input voltages, the coupling also results in severe distortion of input currents when the commonly used feedforward compensation control method with fixed input power factor is adopted. To address these two issues, this paper proposes a feedback control strategy on the input side of MC. This strategy is based on a control method which can modify input reference currents. The input control strategy is embedded into the output control strategy and thus is the inner loop of the system control. The input-side controllers can be designed to achieve expected input control objectives and maintain the output performance at the same time. On this basis, resonant controllers are applied to regulate input currents and instantaneous active power, so as to directly eliminate the input current harmonics and meanwhile ensure the load absorbing constant active power under unbalanced input voltages. The validity and feasibility of the proposed strategy are verified by the simulation and experimental results.

This paper investigates and compares the electromagnetic performance of two novel hybrid-magnetic-circuit variable flux memory machines (HMC-VFMMs) with different hybrid permanent magnet (PM) configurations. The investigated HMC-VFMMs are both geometrically characterized by a combination of series and parallel magnetic circuit topologies, but with different positions of series and parallel PM branches. The developed HMC design can combine the merits of wide flux adjustment range in parallel structure and excellent unintentional demagnetization (UD) withstand capability in series structure. The topologies, features and working principles of the studied HMC-VFMMs with different hybrid magnet configurations are described, respectively. The magnetic circuit model is utilized to analytically reveal the performance metrics of the two machines. The electromagnetic characteristics of the radially-magnetized (RM-) and circumferentially-magnetized (CM-) LCF types of HMC-VFMMs are evaluated and compared by the finite-element (FE) method. Furthermore, the performance comparison of the proposed RM-type HMC-VFMM with a benchmark IPM machine is conducted. The experiments on RM-type HMC-VFMM prototype with RM-structure are carried out to validate the FE analyses.

For the direct matrix converter (DMC) applied to PMSM drives, a novel modulation scheme is proposed in this paper, which could reduce the control complexity and improve the efficiency while achieving zero common-mode voltage. Only three counter-clockwise or clockwise rotating vectors are adopted to operate the DMC. The proposed scheme has the inherent ability to generate sinusoidal input currents without explicit control in the modulation. The duty cycle expressions for the three vectors are quite simple without any trigonometric operations. The switching pattern is fixed, saving the need of sector and sequence determination. Therefore, compared with the conventional modulation scheme which also uses only rotating vectors, the proposed scheme could reduce the execution time by over 80%. In addition, it achieves higher efficiency benefiting from the reduced switching actions. Its validity is verified by experimental results on a 2.4-kW DMC-fed PMSM drive prototype.