2 research outputs found
Indirect minimization of common-mode voltage with finite control-set model predictive control in a five-level inverter
Get PDFMultilevel inverters (MLIs) are counted as the crucial part of the electric drive systems
(EDSs) primarily due to their ability to handle higher operating powers and voltages, to
provide high-quality output waveform, and to reduce dv/dt. Nevertheless, MLIs require a
complex control system to handle multiple control objectives such as load currents, floating
capacitors (FCs) voltage, current tracking errors, and common-mode voltage (CMV) minimization. Among them, the load current and FC voltage objectives are associated with the
basic operation of the MLI, whereas the CMV minimization is associated with the safety
and reliability of the MLI-fed EDSs. Hence, the CMV minimization becomes obligatory to
ensure the safety of the system.
To achieve multiple objectives of MLIs, finite control-set model predictive control (FCSMPC) methods became promising solutions due to the following features: (i) ease of implementation, (ii) intuitive philosophy, (iii) fast transient response, (iv) ability to handle
multiple objectives with a single cost function, (v) easy to compensate control delay, and
(vi) flexible to include system constraints and nonlinearities. However, FCS-MPC methods
use a cost function with weighting factor to directly minimize the CMV of MLIs. The improper selection of weighting factors directly affects the current harmonic distortion of MLIs.
They also need higher execution time to implement in real-time control platforms.
To address the challenges associated with the conventional FCS-MPC methods, a new
per-phase FCS-MPC philosophy is proposed in this thesis. The proposed philosophy minimizes the CMV without using a cost function, thereby eliminating the need of weighting
factors and their impact on current harmonic distortion. Also, the proposed FCS-MPC
is designed to achieve the control objectives of each phase by using an independent cost
function, resulting in a shorter execution time. The proposed philosophy is applied to a
five-level inverter (FLI). The continuous-time and discrete-time models of FLI are developed
to implement the proposed FCS-MPC. Finally, the steady-state and transient performances
are verified on dSPACE-DS1103 controlled FLI laboratory prototype. Also, a comparative
analysis of the proposed and conventional FCS-MPC is presented
Low-Complexity Heun's Method-based FCS-MPC with Reduced Common-Mode Voltage for a Five-Level Inverter
No full textPublisher Copyright: IEEEThe conventional finite control-set model predictive control (FCS-MPC) methods need a cost function with weighting factors to minimize the common-mode voltage (CMV) in the multilevel inverter (MLI) fed electric drive systems. Moreover, these methods require a higher sampling time for real-time implementation, resulting in a rich harmonic content in the inverter ac currents. This article addresses these concerns by proposing a low-complexity FCS-MPC with CMV minimization for a five-level inverter (FLI). The per-phase philosophy is adopted in the design and implementation of the proposed FCS-MPC for an FLI, resulting in a maximum number of predictions of 6 per phase only (a total of 18 predictions in a three-phase FLI system). Moreover, the proposed FCS-MPC minimizes the CMV without using a cost function, leading to superior current harmonic performance. Additionally, Heun's integration method is introduced in the formulation of discrete-time models of the FLI, and they are used in real-time implementation of the proposed FCS-MPC. The superiority of the proposed method is demonstrated through a dSPACE-controlled FLI laboratory prototype. Furthermore, a comparative analysis of the proposed and the conventional FCS-MPC methods is presented in terms of total demand distortion (TDD) of the current, inverter CMV, and the computational burden.The conventional finite control-set model predictive control (FCS-MPC) methods need a cost function with weighting factors to minimize the common-mode voltage (CMV) in the multilevel inverter (MLI) fed electric drive systems. Moreover, these methods require a higher sampling time for real-time implementation, resulting in a rich harmonic content in the inverter ac currents. This article addresses these concerns by proposing a low-complexity FCS-MPC with CMV minimization for a five-level inverter (FLI). The per-phase philosophy is adopted in the design and implementation of the proposed FCS-MPC for an FLI, resulting in a maximum number of predictions of 6 per phase only (a total of 18 predictions in a three-phase FLI system). Moreover, the proposed FCS-MPC minimizes the CMV without using a cost function, leading to superior current harmonic performance. Additionally, Heun's integration method is introduced in the formulation of discrete-time models of the FLI, and they are used in real-time implementation of the proposed FCS-MPC. The superiority of the proposed method is demonstrated through a dSPACE-controlled FLI laboratory prototype. Furthermore, a comparative analysis of the proposed and the conventional FCS-MPC methods is presented in terms of total demand distortion (TDD) of the current, inverter CMV, and the computational burden
