Improved Feedback Quantizer with Discrete Space Vector.

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.

For the power management of a wireless power transfer system for implantable mechanical heart pumps, an additional boost DC-DC converter stage is needed in order to control the power delivered to the implant. Particularly, battery powered and implantable medical devices pose special demands on the efficiency and/or power density of the employed converters. Accordingly, soft-switching and/or high switching frequencies must be targeted. Modulation schemes that allow for Zero-Voltage-Switching (ZVS) such as Triangular Current Mode (TCM) offer a highly efficient operation, but suffer from a large operating frequency variation, which is mainly limited by the digital control. Therefore the Clamp-Switch TCM (CL-TCM) converter can be employed which allows also for the control of the switching frequency variation. In this paper, the CL-TCM and the TCM converter are compared regarding the power conversion efficiency and the power density of the converter. Since the CL-TCM converter is not well known in the literature, the converter is analysed in detail and a modulation scheme is explained that allows for ZVS for all switches in the entire range of operation. In addition, the requirements for ZVS and a control scheme (i.e. timing calculations) are provided for the converter in order to limit the maximum switching frequency. The modulation and control scheme are verified with a hardware prototype. Finally, the performance of the CL-TCM converter is measured and compared to the performance of the converter operated in TCM mode. The measurements show that the CL-TCM converter offers similar performance compared to the TCM operation at lower inductor power density, but has the advantage of a significantly reduced switching frequency variation. In applications, where a very high power density is needed, the TCM converter outperforms the CL-TCM converter in terms of efficiency.

Classic finite-set model predictive control techniques are distinguished by a variable switching frequency which causes noise, large voltage and current ripple. This paper presents an enhanced predictive current control technique with fixed switching frequency applied to the six-phase drives and a Kalman Filter estimator. Simulation results are provided to show the efficiency of the current control algorithm using the mean square error and total harmonic distortion as a figures of merit, thus concluding that the system can work properly with this enhanced technique.

Traditional finite-set model predictive control (FS-MPC) techniques are characterized by a variable switching frequency which causes noise as well as large voltage and current ripple. In this paper a novel predictive control strategy with a fixed switching frequency for a voltage source inverter called as modulated model predictive control (M2PC) is proposed, with the aim of obtaining a modulated waveform at the output of the converter. The feasibility of this strategy is evaluated using simulation results to demonstrate the advantages of predictive control, such as fast dynamic response and the easy inclusion of nonlinearities. Finally, a modified strategy is proposed in order to naturally reduce the common mode voltage. The constraints of the system are maintained but the performance of the system in terms of power quality is improved when compared to FS-MPC.

This paper proposes a photovoltaic (PV) string-level isolated DC–DC power optimizer with wide voltage range. A hybrid control scheme in which pulse frequency modulation (PFM) control and pulse width modulation (PWM) control are combined with a variable switching frequency is employed to regulate the wide PV voltage range. By adjusting the switching frequency in the above region during the PWM control process, the circulating current period can be eliminated and the turn-on period of the bidirectional switch of the dual-bridge LLC (DBLLC) resonant converter is reduced compared to that with a conventional PWM control scheme with a fixed switching frequency, resulting in better switching and conduction loss. Soft start-up control under a no-load condition is proposed to charge the DC-link electrolytic capacitor from 0 V. A laboratory prototype of a 6.25 kW DBLLC resonant converter with a transformer, including integrated resonant inductance, is built and tested in order to verify the performance and theoretical claims.

Apart from variable switching frequency, a major issue in direct torque controlled (DTC) induction motor drives is the high torque ripple, which can be minimized by incorporating suitable pulsewidth modulation schemes such as space vector pulsewidth modulation (DTC-SVPWM) and duty ratio control DTC. However, the simplicity and robustness of the DTC scheme are compromised due to the high computational complexity and requirement of a number of motor parameters for the control. In this article, a simple and elegant control algorithm for the realisation of the DTC-SVPWM that is less dependent on motor parameters is proposed. The stator flux-linkage space vector angle needed to generate the reference torque for the DTC operation is computed based on the basic torque equation and the reference stator phase voltage needed for the SVPWM is determined in turn in every sampling period. For the modulation, a carrier-based space vector pulsewidth modulation (CSVPWM) scheme is adopted to get low torque ripple at constant switching frequency. The proposed speed control scheme avoids the use of rotor parameters and rotating reference frame transformations. It requires no sector identification and only one PI controller is needed for the speed control. Though the scheme has comparable torque ripple as that of the conventional DTC-SVPWM scheme, it significantly reduces the computational burden. Hardware results on a three-phase, 2 HP, 415 V induction motor are presented to validate the performance of the proposed control scheme.

The inverters and control methods are applied in more and more fields with power electronics development. The technology of current hysteretic band PWM is a kind of easy and reliable control method. But the harmonic distortion of load current is big amplitude around switching frequency side band. The paper introduce a Varied Hysteretic-band Current control technique(VHBCC), this method can spreads the spectrum contents of load current around switching frequency side band, reduces the harmonic distortion of load current . At last, The results of simulation prove the method feasible and effective.

In medium-voltage (MV) drives, the switching frequency is limited to a few hundred Hz, for which high-performance control and modulation schemes are necessary to maintain acceptable current and torque distortion. Forced machine current control (FMCC) is a predictive control strategy for MV drives which was proposed in the early 1980s, which can be formulated for either torque or current control. Recently, model predictive direct torque control (MPDTC) and model predictive direct current control (MPDCC) have been developed, sharing with FMCC the use of hysteresis bounds, switching and prediction horizons. However, the relative performances of these schemes are yet to be compared. Through simulation, this paper compares the schemes across a range of operating points. It is shown that the steady-state performance of MPDxC and FMCC is similar when the switching horizon of MPDxC is limited. However, when the switching horizon is extended, the performance of MPDxC is shown to be superior to FMCC, the horizon of which is inherently restricted.

This paper presents a novel hybrid model predictive multilayer control (HMPMC) strategy for modular multilevel converters (M2LCs). The proposed hybrid strategy uses a modified model predictive direct slope control (MPDSC) concept to regulate the load current while concurrently minimizing the switching frequency, circulating current, and capacitor voltage variations through a new MPMC concept. The multilayer philosophy uses dedicated control layers to independently evaluate its control variables. As the main advantage, the hybrid strategy enables operation of M2LC at low switching frequencies. Moreover, this paper proposes a hierarchical screening algorithm, which estimates the minimum number of switching states required to be evaluated for each control variable, reducing the computational burden. An execution order for each control layer, in which the variables are assigned to control layers as appropriate, is also incorporated to further reduce the computational burden. Instead of using conventional weighting factors, this paper uses tuning factors for each layer, which is based on the number of switching states of the lowest cost to make the tuning process efficient and adaptable to any operating conditions. To demonstrate the validity, a prototype single-phase, five-level, 380-VA M2LC is designed, built, and controlled through the proposed strategies. The performance of prototype is investigated under both the steady-state and transient conditions, and the experimental results are presented in comparison with simulations and benchmarked against both the conventional finite control set model predictive control (FCS-MPC) and an improved MPC strategy. The results clearly indicate that the proposed strategy enables efficient operation of the converter at both significantly lower switching frequency and reduced computational burden, which is preferred for high-power applications.

Conventional finite-set model-based predictive control (FS-MBPC) methods inherently present a variable switching frequency which causes harmonic distortion as well as excessive voltage and current ripple. An indirect power control strategy with fixed frequency capability is presented in this paper for a DFIG driven by an indirect matrix converter. The system initial conditions are maintained for the proposed method, showing improvement in terms of power quality when compared to the conventional FS-MBPC even when a lower sampling frequency is imposed. This strategy is verified to be feasible by successful simulation results, furtherly proving the predictive control capabilities of fast dynamic response and intuitive inclusion of nonlinear constraints into the control algorithm.

Conventional Reduced Matrix Converters (RMC) based on Finite control-set model predictive control (FCS-MPC) are widely used in energy-storage systems. However, applying only a single vector per sampling interval increased dynamic and steady-state tracking errors, whereas exhaustive vector search and variable switching frequency further constrain practical deployment. To address these issues, this paper proposes a Quadrant-polarity sector identification (QPSI)-based Multi virtual current-vector fixed-switching-frequency (MVCVFSF) control method. First, multiple virtual current vectors is generated using discrete space vector techniques, and a minimum switching transition constraint is introduced into the cost function to reduce active and reactive power steady-state errors. Second, the QPSI logic replaces trigonometric sector detection and exhaustive vector evaluation by using polarity logic and a predefined switching-state table. To achieve adaptive duty-cycle allocation for synthesizing virtual vectors from basic vectors, Chaotic particle-swarm optimization (CPSO) is employed for online optimization, while a modulated MPC framework maintains a Fixed switching frequency (FSF). Additionally, active-power error terms at the kth and k+2th sampling instants are incorporated into the cost function as constraints to suppress power ripple and improve steady-state accuracy. Finally, Lyapunov-based stability analysis is provided to ensure closed-loop stability of the CPSO-assisted predictive power-control framework. Experimental results demonstrate that the proposed method achieves lower steady-state error while maintaining a FSF, outperforming existing approaches.

Two new pulse width modulation (PWM) schemes: chaos-based sinusoidal PWM (SPWM) and chaos-based space vector PWM (SVPWM) are brought forward. There are cluster harmonics around the multiples of switching frequency in conventional SPWM and SVPWM output waves owing to their fixed switching frequencies. Chaos-based PWM strategies utilize a chaotic changing switching frequency to spread the harmonics continuously to a wideband area so that the peak harmonics can be reduced greatly. This can be an effective way to suppress harmonic and reduce ripple current and torque in induction motor drives. The good agreement between theory and simulation has approved the validity of this study

Model predictive control (MPC) presents important advantages in the control of the power converter and drives such as, fast dynamic response and capability to include nonlinear constrains. These have positioned MPC as a powerful and realistic control strategy, however, it also has disadvantages such as variable switching frequency and parameter sensitivity. This paper applied a modulated model predictive speed control that guarantees a fix switching frequency and, thanks to disturbance compensation, robustness to parameters variation. The strategy is validated and compared to finite set model predictive speed control through simulation results.

In this paper, a hybrid pulsewidth modulation (PWM) scheme is proposed to suppress the LC resonance for the high-power current-source inverter (CSI) fed drives with low switching frequency. In CSI drive systems, the selective harmonic elimination (SHE) is selected due to the better performance of harmonics, but the LC resonance cannot be effectively damped due to the lack of control flexibility of SHE. In this paper, SHE is only used for the steady-state operation. The modulation scheme is then switched to space vector modulation with dynamic capacitor voltage control when the transient event occurs. The smoothed transitions between different modulation schemes are proposed. The proposed hybrid method effectively solves the resonant issues in CSI drives, while maintaining the power quality. Both simulation and experiments verify the performance of the proposed hybrid PWM scheme.

Classical model based predictive control for single-phase cascade H-bridge multilevel STATCOM generates a variable switching frequency that produces high frequency harmonics and high stress on the power semiconductor devices. To solve these issues, in this paper is proposed a predictive control strategy operating at fixed switching frequency. The method includes a modulation stage in the predictive controller. Simulation results show increased performance of the proposed control method in terms of current ripple and total harmonic distortion.