The optimization of banking regulation intensity from the perspective of financial stability in banking sector: an empirical analysis

This paper investigates a multifactorial model, which allows defining an optimum level of banking regulation intensity based on the provision of a financial stability (at the macrolevel) and financial stability of banks (at the microlevel). An aggregated index of banking regulation intensity as well as an integrated index of financial stability of banks, which were the main factorial and resultative characteristic features during investigations, was formed for carrying-out of an empirical analysis. The optimum level of intensity of banking regulation has been suggested to define as the extremum of function of integrated index of financial stability of banks (determined by the method of the uniform optimality) on the relevant influencing factors (method of principal components)

Analysis and Comparison of Peak-to-Peak Current Ripple in Two-Level and Multilevel PWM Inverters

Three-phase multilevel inverters are used in many medium- and high-power applications such as motor drives and grid-connected systems. Despite numerous PWM techniques for multilevel inverters have been developed, the impact of these modulation schemes on the peak-to-peak output current ripple amplitude has not been addressed yet. In this paper the analysis and the comparison of current ripple for two- and three-level voltage source inverters are given. Reference is made to optimal and popular modulation, so-called centered PWM, easily obtained by both carrier-based modulation (phase disposition, with proper common-mode voltage injection) and space vector modulation (nearest three vectors). It is shown that the peak-to-peak current ripple amplitude in three-level inverters can be determined on the basis of the ripple in two-level inverters, obtaining the same re-sults as by directly analyzing the output voltage waveforms of the three-level inverters. This procedure can be readily extended to higher level numbers. The proposed analytical developments are verified by both numerical simulations and experimental tests

General Approach for Modeling and Control of Multiphase PMSM Drives

This article presents a modeling approach and a control strategy for multiphase surface-mounted permanent magnet synchronous machine drives. The mathematical model is completely general with respect to the machine parameters and to the winding configuration. It also intrinsically considers the effects of eventual constraints for the phase currents, generated from the electrical connections among the phase windings or resulting from faults. The current controller is entirely formalized in the phase variables domain. It is based on a pseudoinverse decoupling algorithm and on a linear decoupled controller. The current references are computed by means of a maximum-torque-per-ampere strategy, which can be also easily adapted for torque sharing purposes. The proposed controller requires minimum changes with respect to system reconfigurations or parameters variations and, therefore, it is suited both for healthy and for faulty operations. An extensive set of experimental results has been conducted to validate the proposed approach in several testing scenarios

Hybrid Modulation Technique with DC-Bus Voltage Control for Multiphase NPC Converters

The article presents a novel carrier-based pulsewidth modulation technique for multiphase neutral point clamped converters. The technique is aimed to actively control the neutral point (NP) potential while supplying the desired set of line-to-line voltages to the load. Standard techniques are either based on the sole common mode voltage injection or on the sole multistep switching mode; contrarily, the proposed algorithm combines these two approaches to take advantage of their main benefits. The technique performs well for each number of phases, for each modulation index, and for each type of load. It can control in closed-loop the NP voltage to any desirable value with a reduced number of switching transitions. The proposed approach has been experimentally validated and compared with other carrier-based algorithms

Multidirectional Power Flow Control among Double Winding Six-Phase Induction Machine Winding Sets

This paper presents an indirect rotor-field oriented control (IRFOC) algorithm for symmetrical six-phase double-winding induction machines with four three-phase sub-winding sets. The presented algorithm introduces the ability to control the power flow between different sub-winding sets. Multiple three-phase induction machines are utilised for critical applications such as more-electric aircrafts, due to their high reliability and fault tolerant capabilities. In this paper, the proposed control scheme is utilising the auxiliary currents of each six-phase sub-motor to achieve full control of the sub-winding sets current amplitudes and consequently the power flow direction for each sub-winding set. A six-phase induction machine with double winding is utilised to validate the proposed control scheme. Four isolated voltage source inverters (VSIs) are used to supply each winding set of the machine. The double-winding six-phase induction machine controlled by the proposed IRFOC algorithm is simulated using Matlab/Simulink. Presented simulation results validate the ability of the algorithm to appropriately control the power flow of each sub-winding set

Analytical formula for leg voltage THD of a PWM multilevel inverter

In this paper derivation of an analytical formula for the leg voltage THD is presented. The considered system is a leg of a multilevel pulse width modulated (PWM) voltage source inverter (VSI). The solution is based on the Parseval's theorem. The assumption throughout the derivations is that the ratio of the switching to the fundamental frequency is high. Derivations are based on the integration of the power of the PWM signal in a single switching period over the fundamental period of the signal. Only an ideal sinusoidal reference leg voltage is analysed. Analytical expression for the leg voltage THD is given for any number of levels. Validity of the derived analytical equations is confirmed by simulations and experiments

Analytical Formulas for Phase Voltage RMS Squared and THD in PWM Multiphase Systems

The analysis and assessment of the pulsewidth modulation (PWM) techniques is commonly based on the comparison of the total harmonic distortion (THD) results. THD is usually calculated by application of the Fourier transformation and by taking a limited number of harmonics into the consideration. In this paper, derivation of analytical formulas for the phase voltage THD is presented. The considered system is a symmetrical multiphase starconnected load, supplied from a multilevel pulsewidth-modulated voltage-source inverter (VSI, three-phase case is also covered). The solution is based on the Parseval’s theorem, which links frequency spectrum and time domain through the average power (i.e., rootmean- square (rms) squared value) of the signal. The assumption throughout the derivations is that the ratio of the switching to fundamental frequency is high. Derivations are based on the integration of the power of the PWM signal in a single switching period over the fundamental period of the signal. Only ideal sinusoidal reference voltages are analyzed, and no injection of any type is considered. Formulas for phase voltage THD for any number of phases are derived for two- and three-level cases, for themost commonly used carrier-based methods. Comparison of the analytically obtained curves with simulation and experimental results shows a high level of agreement and validates the analysis and derivations

A hybrid modulation technique for the DC-bus voltage balancing in a three-phase NPC converter

In this paper a new pulse width modulation technique for three-phase neutral point clamped (NPC) converter is presented, with the aim to actively control the dc-bus capacitors’ voltages. To meet this requirement, usually NPC modulation techniques are either based on the sole common mode voltage injection (CMI) or on the sole multi-step (MS) switching mode of operation. Contrarily, the presented approach combines these two strategies, taking advantages of all their main benefits while keeping the switching transitions to the minimum required number. The approach has been numerically tested and compared with some of the other strategies, showing an overall better behaviour, especially for high modulation indices

Hybrid modulation technique with dc-bus voltage control for multiphase NPC converters

The paper presents a novel Carrier-Based Pulse Width Modulation (CBPWM) technique for multiphase Neutral Point Clamped (NPC) converters. The technique is aimed to actively control the Neutral Point (NP) potential while supplying the desired set of line-to-line voltages to the load. Standard techniques are either based on the sole Common Mode Voltage Injection (CMI) or on the sole Multi-Step (MS) switching mode; contrarily, the proposed algorithm combines these two approaches to take advantage of their main benefits. The technique performs well for each number of phases, for each modulation index and for each type of load. It can control in closed-loop the NP voltage to any desirable value with a reduced number of switching transitions. The proposed approach has been experimentally validated and compared with other carrier-based algorithms

Vector Control of Multiple Three-Phase Permanent Magnet Motor Drives

With the rapid development of power electronics, multiphase electrical solutions are becoming a competitive alternative to the conventional three-phase drives. Nowadays, the multiphase drives represent a robust and consolidated technology in both safety-critical and high-power applications. In addition, soon they will most likely be employed in the transportation electrification process. In this context, the multiple three-phase structures are undergoing an impressive development since they use the well consolidated three-phase technology reducing cost and design time. In this paper, a highperformance vector control for multiple three-phase permanent magnet motor drives is proposed. The developed solution employees a modular approach for the independent control of each three-phase unit. To show the feasibility of the developed control scheme, experimental results are provided for a ninephase permanent magnet machine employing a triple threephase configuration