S. Mohamadian, H. Azizi Moghaddam,
Volume 16, Issue 1 (March 2020)
Abstract
Linear AC power supplies can be replaced by their nonlinear switching counterparts due to the lower voltage drops and higher efficiency and power density of switching-mode inverters. Multilevel cascaded H-bridge (CHB) converters are the preferred inverter structure because of modular configuration, control, and protection. The output voltage quality in CHB converters depends on the number of output levels. Asymmetric CHBs (ACHBs) produce an output voltage with higher number of levels with respect to CHBs for the same number of cascaded modules. This results in the reduction of power supply size, voltage drops, and losses. Considering the relative high switch counts, analysis of the effect of conduction and dead-time voltage drops on the inverter output characteristics is an important challenge in designing multilevel converters. In this paper, a generic algorithm is presented to calculate the conduction and dead-time voltage drops of ACHBs utilizing level-shifted modulation. These voltage drops give the necessary information for the design of heatsinks, switch selection, output impedance estimation, and the compensation schemes. It is shown through theoretical and simulation studies that the aforementioned voltage drops of ACHBs are to be calculated in a different manner with respect to the CHBs which mostly use the phase-shifted modulation.
H. Azizi Moghaddam, A. Farhadi, S. Mohamadian,
Volume 18, Issue 2 (June 2022)
Abstract
In the new advanced drive schemes, identification and modeling of the load complex characteristics can play an important role to predict the dynamic performance of the proposed control strategy. The novelty of this paper consists in the classification of the different types of the nonlinear loads which the electrical drive systems may encounter. In this study, nonlinear components of mechanical loads are divided into two groups. The first type includes nonlinear phenomenon caused by the nature of load which is predictable and identifiable. Another type of loads nonlinear characteristic happens due to the occurrence of a mechanical fault in motor, coupling or load parts. Generally, this type of non-intended nonlinear effect is not predictable and often occurs in the installation and operation stage of the drive system utilization. In this paper, the performance of an induction servo drive system has been simulated under the influence of different types of non-linear industrial loads.
Hossein Azizi Moghaddam, Arman Farhadi,
Volume 20, Issue 1 (March 2024)
Abstract
Dynamometers are equipment that has been widely used in the field of electric machines test benches. A dynamometer system has the ability to create intricate and unpredictable behaviours of mechanical loads according to a programmed manner. Extensive research into the characteristics of loads found in industrial settings has shown that non-linear and complex phenomena, including misalignment, mechanical friction, and others, are unavoidable in industrial drive systems. To assess the performance of motor and drive systems in industrial drives when subjected to these non-linear and complex loads, a fast and precise dynamic drive system must track high-frequency torque signals with precision. The suggested dynamometer, serving as an instrumental device, has the ability to emulate a wide torque response across various frequencies during both transient and steady-state conditions for the machine under test. Simulations and experimental results confirm the dynamometer's wide-ranging dynamic response, enabling the emulation of different linear and non-linear loads.
