Finite control set model predictive control (FCS-MPC) has been widely used in the control of grid-connected converters with the advantages of fast dynamics, multi-objective control, and easy implement. However, the conventional FCS-MPC bears with variable switching frequency, high current ripple and computational burden. An improved current model predictive with the cost function-based modulation scheme (CFM-MPC) is proposed for a three-phase three-level VIENNA rectifier to improve the power quality. First, the mathematical model and voltage vector are given according to the principle of deadbeat control. Then, the voltage vector of different voltage vectors are selected according to the location of the voltage vector reference, and the switching action time of the selected are directly calculated by the inversely proportional with cost function value of the selected vectors. It remains the merits of both the conventional MPC and space vector pulse width modulation schemes to track the optimum voltage vector without increasing the computational burden. Finally, a comparative study with the proposed CFM-MPC and conventional FCS-MPC has been conducted to verify the superiority of the proposed scheme. The results show the proposed CFM-MPC has the advantages of lower power ripple, fixed switching frequency, lower total harmonic distortion and neutral point potential balance.

We present a flow cytometer on a microfluidic chip that integrates an inline lens-free holographic microscope. High-speed cell analysis necessitates that cells flow through the microfluidic channel at a high velocity, but the image sensor of the in-line holographic microscope needs a long exposure time. Therefore, to solve this problem, this paper proposes an S-type micro-channel and a pulse injection method. To increase the speed and accuracy of the hologram reconstruction, we improve the iterative initial constraint method and propose a background removal method. The focus images and cell concentrations can be accurately calculated by the developed method. Using whole blood cells to test the cell counting precision, we find that the cell counting error of the proposed method is less than 2%. This result shows that the on-chip flow cytometer has high precision. Due to its low price and small size, this flow cytometer is suitable for environments far away from laboratories, such as underdeveloped areas and outdoors, and it is especially suitable for point-of-care testing (POCT).

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A three‐phase three‐level VIENNA rectifier has been widely used in the data center DC power supply and AC/DC hybrid power supply system with the advantages of without dead‐time, low switch voltage stress and small grid‐current harmonic. However, the performance of grid current strongly depends on the controller parameter, and the unreasonable controller parameter may deteriorate the grid current. To effectively improve the static and dynamic performance of grid current, a new kind of carrier‐based pulse width modulation scheme based on the double closed‐loop discrete sliding mode strategy is put forward. Further, a modified exponential reaching law is presented to effectively improve the shaking shock effect caused by the traditional sliding mode surface and the neutral voltage dc wave suppression strategy is then presented. To verify the correctness and effectiveness of the proposed sliding mode control strategy, a complete simulation model and experimental prototype platform under the digital control is established, the detailed theoretical analysis and design method of the proposed control strategy are presented. The simulation and experimental results show that the steady and the transient performance of the grid current with the proposed control strategy are effectively improved, and the neutral voltage in dc side is kept balanced at the same time. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.