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Three-level T-type converter switching states
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... deduce this high number of switching states, a single T-type switching states and vector digram will be presented firstly. The number of switching states for a single three-level T-type converter is 27 ( listed in Table 2 and Table 3). In this paper, the switching state of the five-level proposed converter will be two numbers i.e. ...Similar publications
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... Điện áp này được sinh ra giữa điểm trung tính của tải (nối sao) và điểm nối đất. CMV này ảnh hưởng đến ổ trục của động cơ cảm ứng và làm giảm tuổi thọ của nó [6,7]. Hai cách tiếp cận phổ biến sử dụng kỹ thuật điều chế PWM đã được trình bày để khắc phục vấn đề này, đó là giảm CMV [8,10] và loại bỏ CMV [11]. ...
Trong bài báo này, kỹ thuật điều khiển dự báo nhanh không sử dụng hàm chi phí cho bộ nghịch lưu 3-pha 3-bậc dạng T nhằm giảm điện áp common-mode và cân bằng điện áp trên các tụ được trình bày. Dựa trên mô hình toán của nghịch lưu, nguyên lý điều khiển dự báo thông thường thông qua hàm chi phí của các mục tiêu được trình bày. Tiếp đến, chiến lược lựa chọn trước các vector ứng cử viên được đề xuất nhằm dự báo nhanh vector tối ưu mà không cần đến các hàm chi phí giảm common-mode và hàm chi phí cân bằng điện áp trên các tụ. Các mô phỏng thực hiện bởi phần mềm Matlab cho cả hai kỹ thuật điều khiển thông thường và cải tiến để chứng minh tính đúng đắn của các lý thuyết đã trình bày. Hiệu quả của phương pháp cải tiến được chỉ ra thông qua các so sánh kết quả điều khiển giữa các phương pháp.
... Five-level (5L), dual T-type MLC (5LDT-MLC) is one of the most recent T-type topologies, which produces a high number of SS that extensively achieve the capacitor balancing using switching state redundancy [9], [10]. However, this converter has been tested using open-loop space-vector control [11]. ...
... A better solution for capacitor balancing is to use the converter pulse width modulation (PWM) techniques to balance the DC link as presented in [16]- [19]. The capacitor balancing of T-type MLC has been executed using space vector PWM (SVPWM) in [20]- [22]. However, the extension of SVPWM to converters with higher number of levels requires bulky computation burden. ...
This paper presents and evaluate a prototype of an advanced topology of five-level T-type MLC, namely “T5MLC”, implemented within a complete AC induction drive. The evaluation is based on the ability of balancing the converter DC link capacitor voltages, the torque and flux ripples reduction of the induction motor under control, the harmonic analysis and the efficiency of the inverter and the overall drive system. The converter implementation and design considerations using Silicon Carbide (SiC) discrete MOSFETs are discussed. The operation and the analytical model of T5MLC using switching-functions are presented. The model predictive control (MPC), as a preferred AC drive control approach, is selected to adapt the machine torque and flux, and to balance the DC link capacitor voltages. The T5MLC drive system is tested at different scenarios; i.e. suddenly load changing and speed reversal, to ensure the converter capability and excellent performance in AC drive applications. The experimental results show that the MPC could achieve an excellent performance in terms of low harmonic distortions, reduced flux and torque ripples and the ability of balanced DC link capacitors. In addition, the loss analysis showed that the T5MLC is 5.5 % to 24.8 % efficient compared to dual T-type MLC at different loading conditions.
... The capacitor balancing of T-type topologies has been achieved using MPC [18], [19] and switching states redundancy [23]. Basically, including capacitor balancing in MPC cost function imposes some computation difficulties due to weighting factor tuning [19], [24], [25]. ...
... Unlike [18], [19], and [25], this paper proposes a new approach that reduces the number of evaluations used to predict the optimal solution for MLCs. Since the torque and flux are VV dependent and the capacitor balancing is switching-statedependent [23], splitting the evaluation of the cost function into two cascaded optimization stages becomes achievable. In the first stage, the torque and flux cost function are considered, whereas the capacitor balancing is achieved in the second stage. ...
... These three terms are the torque ripple, flux ripple, and capacitor voltage deviation. Generally, the torque and flux depend on the voltage vector, whereas the capacitor balancing depends on the switching state [23]. Unlike [18], [19], and [25], this paper proposes splitting the evaluation of the cost function into two cascaded optimization stages. ...
This paper proposes a new approach for the capacitor balancing of a dual three-level (3L) T-type converter based on Silicon Carbide (SiC) discrete semiconductors. The study is performed while the converter feeds an open-ends induction motor (OEIM). The model predictive control (MPC) scheme is developed to balance the DC link capacitors and to control the machine torque simultaneously. The proposed technique for MPC reduces the number of redundant switching states used in computations without affecting the operating voltage vectors. This reduces the computational time substantially. In addition, the proposed control strategy mitigates the weighting factors tuning problem of capacitor balancing in addition to the conventional MPC cost function. Matlab simulation results for the proposed drive system under different case studies are presented. Hardware experimental setup for the proposed converter is built, tested, and verified. A comparison between experimental and simulation results is presented. It is observed that the theoretical as well as the experimental results are in full agreement.
... A 5L Nested DCC capacitor balancing has been studied using MPC in [15], [16]. As far as the authors know, only one study in [17] has investigated the capacitor balancing of the dual T-type topology using switching state redundancy based on off-line study. ...
... Another related important problem in AC drives is the CMV. This CMV affects the bearing of the induction motor (IM) and reduces its lifetime [17], [18]. Two well-known approaches were presented to solve this problem, namely CMV reduction (CMVR) and CMV elimination (CMVE). ...
The dual T-type multilevel converter (MLC) is an advanced topology with a reduced switching device count compared to conventional diode clamped converter. This paper proposes a reduced switching state model predictive control (MPC) of a dual T-type drive system considering the DC link capacitor balancing, the common-mode voltage (CMV) along with torque control of an open-ends induction motor. The proposed study addresses the CMV in two different scenarios; i.e. CMV reduction (CMVR) and CMV elimination (CMVE). A Matlab simulation for the proposed drive system is presented. A dual T-type converter prototype based on Silicon-Carbide discrete MOSFET switch is designed, implemented and tested in laboratory. The proposed MPC scheme achieves the torque command as well as balances the dual DC links in an efficient manner. It is observed that the CMVE has some limitation compared to CMVR particularly at rated speed operation. It is worth mentioning that the proposed reduced switching states technique could reduce the computation time from 5.5 ms to 140 μs for CMVR and 70 μs for CMVE. In addition, the results demonstrate the effectiveness of CMVR scheme in reducing the harmonic contents, the torque and flux ripples, and converter switching loss compared to CMVE scheme.
... Generally, MLC capacitor balancing can be performed either by using auxiliary circuit [93], or by modulation and control technique [92][93][94][95][96][97][98][99]. The dual 3L T-type MLC capacitor balancing has been studied once in [100] where the problem of the capacitor unbalance was attributed to the fluctuation of the DC link midpoints, O and O , as shown in Fig. 10, due to non-uniform switching across the series-connected capacitors. The charging and discharging of the series-connected capacitors for similar intervals and currents can keep these capacitors balanced. ...
Renewable energy systems integration prefers DC–AC converters of high efficiency, low harmonic injection and small size. Multilevel converter (MLC) is preferred compared to two-level converter thanks to its low harmonic injection, even at low switching frequency values, and accepting high power as well as voltage levels. Among reduced switching devices count MLCs is the T-type topology. This article introduces a review of the different advanced topologies of T-type MLC in comparison with the conventional neutral point clamped converters. The operation of each topology, the design consideration and the performance in low-voltage applications such as AC drive systems, grid-tie integration of renewable energy and power train drive applications are discussed. In addition, the design considerations using enhanced semiconductor switches are elaborated. Different studies regarding MLCs—like common-mode voltage elimination or reduction, open-switch fault diagnosis, open- as well as short-circuit fault tolerance, and DC link capacitor voltage balancing for T-type topologies—are illustrated. Finally, recommendations for future work research directions are highlighted.
This paper proposes an intensive study for common-mode voltage (CMV) elimination/reduction in a five-level dual T-type multilevel converter (5LDT-MLC) drive. An advanced and fast model predictive control (MPC) approach is developed for CMV reduction (CMVR) and CMV elimination (CMVE) based on preselection of the switching states (SS). In addition, the proposed approach considers the torque control and the capacitor balancing of the proposed drive as essential aspects of MLC drives. A detailed study for the impact of the converter SS on the CMV is presented. The main features of the proposed MPC approach are reducing the complexity of the cost-function, the tuning burden of the weighting factors, and the computation time by more than 80% compared to conventional MPC techniques. A hardware implementation based on Silicon Carbide (SiC) T-type MLC is built. The experimental results demonstrate the effectiveness of the proposed MPC approach to mitigate/eliminate the CMV along with achieving the torque command and balancing the DC link capacitors. Unlike conventional CMVR techniques, the proposed approach reduces the CMV by 75% of its normal values without jeopardizing the harmonic contents, drive efficiency, and flux as well as torque ripples.
