Hamid Mahmoudi

A New Multiobjective Modulated Model Predictive Control Method With Adaptive Objective Prioritization

This work proposes a new multiobjective modulated model predictive control (MPC) method for control of power electronic converters. The proposed method retains the advantages of conventional MPC methods in programing the nonlinear effects of the converter into the design calculations to improve the overall dynamic performance of the system and builds upon that by offering a new modulation technique for MPC to minimize the voltage and current ripples through by using a fixed switching frequency. To demonstrate the effectiveness of the proposed method, it has been used to overcome the stability problems caused by a constant power load in a multi converter system as a case study. Experimental results from a prototype cascaded converter system are provided to validate the theoretical outcomes.

A New High-Switching-Frequency Modulation Technique to Improve the DC-Link Voltage Utilization in Multilevel Converters

This paper presents a new high-frequency modulation method for multilevel converters. The proposed method provides a broad linear operating range and can be digitally implemented with minimal computational effort. This modulation method creates a phase voltage composed of a rectangular component superimposed on the top of a quasi-square-shaped reference function. The reference functions are defined such that the utilization of the dc-link voltage is maximized in any modulation index, while the dv/dt of the switches is always the minimum possible value. In order to implement the proposed method, an update time that is much shorter than the fundamental period is defined in the algorithm for updating the rectangular components of the reference voltage. The high-frequency rectangular component can then be imposed on the reference function to generate the final switching function by switching between two voltage levels during the time between two update instances. Several experimental results are provided to evaluate the performance of the proposed method and to compare its operation to conventional methods.

A new modulated model predictive control for permanent magnet synchronous motor

Variable switching frequency and regulating the dq-axes current of the motor with noticeable ripples are of the problems pertaining to finite control set model predictive control (FCS-MPC) of a motor drive. In this paper a novel method has been developed to modulate the selected voltage vector of the FCS-MPC method. This method first choses the voltage vectors that should be applied to the motor in the next sampling time and then solves a set of equations to find the duration of application of each voltage vector. The equations have been obtained through an analytical method which drives the dq-axes currents exactly to their references at the end of each sampling time. Simulation results are provided to prove the effectiveness of the proposed method.

Multifault Tolerance Strategy for Three-Phase Multilevel Converters Based on a Half-Wave Symmetrical Selective Harmonic Elimination Technique

This paper presents a generalized fault-tolerant strategy to improve the performance of the three-phase cascaded H-bridge converters with faulty cells. The proposed fault-tolerant strategy combines the fundamental phase-shift compensation (FPSC) method with half-wave symmetrical selective harmonic elimination (SHE) to rebalance the inverter voltages and limit the total harmonic distortion (THD) of the waveforms. In this paper, first, the FPSC method is explained and the formulation for a new half-wave symmetric SHE technique is provided. Then, the main idea of the paper is presented as to adjust the phase angles of the fundamental harmonic of the line-ground voltages while equalizing the amplitudes and phase shifts of the third-order harmonics and eliminating some higher order harmonics. The proposed fault-tolerant strategy uses the increased degree of freedom provided by half-wave symmetrical SHE to adjust phase angles and eliminate a wide range of lower order harmonics for limiting the THD of the converter voltages under the faulty conditions. Finally, several experimental results are provided to validate the operation of the proposed strategy.

A new maximum power point tracking method for photovoltaic applications based on finite control set model predictive control

This paper proposes a new Maximum Power Point Tracking (MPPT) method based on the concept of Finite Control Set Model Predictive Control (FCS-MPC) for Photovoltaic (PV) applications. The proposed method uses the measured PV current and power data from previous steps to predict the power in the next step correspondent to various possible switching configurations of the power converter. Then it applies the switching configuration which results in increase in the produced power by the PV array. Simulation results are provided to verify operation of the proposed method and compare it with the traditional Perturb and Observe (P&O) method.

Modulated Model Predictive Control of Modular Multilevel Converters in VSC-HVDC Systems

This paper proposes a new modulated model predictive control method for the control of modular multilevel converters (MMCs) in voltage source converter-high voltage dc systems. The proposed method retains the advantages of the conventional finite control set-model predictive control methods by programing the nonlinear properties of the MMC into the design calculations while minimizing the ac line and circulating current ripples and steady-state error by generating modulated switching signals with a fixed switching frequency. In this paper, first, the predictive modeling of the MMC is provided. Next, the proposed control method is described. Then, the application of the proposed method to an MMC system is detailed. Finally, experimental results from an MMC system connected to a three-phase grid are provided to validate the theoretical outcomes.

Fault-Tolerant Space Vector Modulation for Modular Multilevel Converters with Bypassed Faulty Submodules

This paper develops a modulation based fault-tolerant (FT) strategy for restoring the operation of three-phase modular multilevel converters (MMCs) with faulty switches. This FT strategy is based on a proposed modified space vector modulation (SVM) technique that generates balanced line-to-line (line) voltages even in the case of a fault occurrence. In the postfault operation, the proposed strategy is able to restore the fundamental amplitude of the line to the neutral (load) voltages to that of the normal operation condition with a slightly increased voltage stress over the switches in the faulty phase. In this paper, first a brief background about MMCs and SVM technique is provided. Then, the proposed FT strategy and the modified SVM technique are presented. Finally, several simulation and experimental results are provided to validate operation of the proposed strategy.

Selective harmonic mitigation for cascaded multilevel inverters in the event of unbalanced phase condition

This paper provides the switching angles that mitigate the dominant low-order line-to-line voltage harmonics in a cascaded H-bridge power converter with a single faulty switch. In this paper, first the firing angles for 5-level and 7-level converters are calculated by solving a set of nonlinear equations. Then, in the faulty condition, a set of switching angles for each phase that results in balanced line-to-line voltages is derived. Finally, the provided solutions are used to simulate the faulty operation of a multilevel inverter.

A fault tolerance switching strategy based on modified space vector modulation method for cascaded multilevel converter

This paper presents a new fault-tolerant strategy to guarantee the performance of three-phase multilevel (ML) converters with faulty switches. The proposed fault-tolerant strategy is based on the modified Space Vector Modulation (SVM) technique in conjunction with the Fundamental Phase-Shift Compensation (FPSC) method. In this paper, first a brief background about SVM and FPSC methods is provided. Then the proposed fault-tolerant strategy and the modified SVM technique are presented. Finally, experimental results are provided to validate operation of the proposed strategy.