Joel Prieto

Predictive Current Control of Dual Three-Phase Drives Using Restrained Search Techniques

The interest in predictive control techniques and multiphase drives has re-emerged in the last decade, and predictive control techniques have been recently presented as a viable alternative to conventional PI and carrier-based or Space Vector PWM techniques in the current regulation of power converters and drives. Proposed schemes have demonstrated good performance at the expenses of a high computational cost and an unknown switching frequency. However, little attention has been paid to the multi-level VSI application. A number of predictive techniques have been developed in recent times for six-phase 2-level voltage source inverters (VSI), like the restrained search predictive control technique or RSPC, which has been used to favor on-line implementation at the expense of achieving suboptimal solutions. This paper investigates the application of multi-level VSI converters in conjunction with the RSPC method in multiphase drive applications. Simulation results are provided to test the viability of a 3-level VSI power converter and the RSPC predictive control method for the current control of an asymmetrical six-phase drive.

An Enhanced Predictive Current Control Method for Asymmetrical Six-Phase Motor Drives

The interest in predictive control approach and multiphase drives has been steadily growing during the last decade. Predictive control techniques have been recently introduced as a viable alternative to conventional PI controllers with carrier-based or space vector PWM techniques in the current regulation of multiphase power converters and drives. The developed schemes have demonstrated a good performance at the expense of a high computational cost, an unknown switching frequency, and the appearance of large undesirable stator current harmonic components. In this paper, an enhanced predictive current control technique with fixed switching frequency is introduced for an asymmetrical dual three-phase ac drive. Fast torque and current responses are achieved while favoring stator current harmonic suppression. The experimental results are provided to verify the benefits of the proposed control method when compared to the other existing predictive control methods.

Switching Ripple Characteristics of Space Vector PWM Schemes for Five-Phase Two-Level Voltage Source Inverters—Part 1: Flux Harmonic Distortion Factors

Multiphase variable-speed drives supplied from two-level voltage source inverters (VSIs) are, at present, contenders for numerous industrial applications. Various pulsewidth modulation (PWM) methods for multiphase VSIs, aimed at sinusoidal output voltage generation, have been developed using both carrier-based and space-vector approaches. An increased number of voltage space vectors, available for the synthesis of the output voltage, offer greater flexibility for the PWM scheme development, compared to the three-phase case. This paper presents comprehensive analytical analysis and comparison of switching ripple characteristics of two continuous space vector PWM (SVPWM) methods for a five-phase two-level VSI. Considered SVPWM schemes select a different set of four active space vectors per switching period in order to generate sinusoidal output voltages. This paper also presents the evaluation of the flux harmonic distortion factors of the SVPWM techniques. Correlation with corresponding current ripple and total harmonic distortion is established in Part 2 of this paper, where theoretical considerations are verified by simulations and through experimental investigation on a five-phase VSI-fed induction motor drive.

Comparative Analysis of Discontinuous and Continuous PWM Techniques in VSI-Fed Five-Phase Induction Motor

This paper reports on flux harmonic distortion factor and current ripple analysis for various discontinuous pulse-width-modulation (PWM) techniques, which are applicable in conjunction with five-phase two-level inverter-fed induction motors. The analysis is based on the application of the complex space vector approach. The results are compared throughout with the corresponding continuous PWM techniques. Different space vector PWM and carrier-based PWM methods are encompassed by the analysis. This paper is supported by extensive simulation results. Verification of theoretical findings is provided through experimental measurements on a five-phase induction motor.

Space-Vector PWM With Reduced Common-Mode Voltage for Five-Phase Induction Motor Drives

The growing interest in multiphase electrical drives has required the extension of control schemes and modulation techniques already well known for three-phase drives. Specifically, different and more complex space-vector pulse width modulation (SVPWM) methods have been developed for multiphase machines taking into account the increased number of switching possibilities and the new components resulting from generalized Clarkes transformation. In spite of the intensive work undertaken in the last decade, no SVPWM techniques with common-mode voltage (CMV) reduction have been developed for five-phase drives. This work proposes two SVPWM methods that are capable of reducing the peak-to-peak CMV by 40% and 80% compared to standard five-phase modulation strategies. Reduction of the CMV is done at the expense of higher phase voltage and current distortion. Simulation and experimental results confirm the CMV reduction and quantify the performance penalties of the proposed methods.

Switching Ripple Characteristics of Space Vector PWM Schemes for Five-Phase Two-Level Voltage Source Inverters—Part 2: Current Ripple

Flux harmonic distortion factors (HDFs) of two space vector pulse width modulation (SVPWM) schemes, aimed at sinusoidal output voltage generation with five-phase voltage source inverters, have been evaluated in Part 1 of this paper. Analytical considerations and numerical integration have been applied in order to determine the switching properties of the considered SVPWM methods. It has been shown that the SVPWM based on four large vectors leads to a considerably higher overall per-phase flux HDF than the method based on two large and two medium space vectors. The purpose of the second part of the paper is to relate flux HDFs to the current ripple and current total harmonic distortion and thus explore further switching characteristics of the two SVPWM techniques. The applied approach is based on simulation and experimentation, in conjunction with the subsequent fast Fourier transform of the waveforms, so that all the results for the ripple are obtained using a methodology completely different from the one in Part 1. Relationships that correlate the current ripple and the flux HDFs are established, and it is further shown that the current ripple can be easily calculated from the flux HDF values of Part 1 if the relevant leakage inductances of the two planes are known. Hence, the complete theory of Part 1 is fully verified by both simulation and experimentation. It is also shown that, in certain cases, the SVPWM based on four large vectors may lead to a smaller current ripple despite a considerably higher flux HDF.

Space Vector PWM With Reduced Common-Mode Voltage for Five-Phase Induction Motor Drives Operating in Overmodulation Zone

This study presents a space vector pulsewidth modulation algorithm for five-phase converters operating in the overmodulation region that forbids the use of zero vectors, covering the whole overmodulation range and providing minimum x-y voltages. Avoiding zero vectors reduces the content of low-order current harmonics and, at the same time, reduces the common-mode voltage (CMV) by 40%. The method is first implemented using medium and large voltage space vectors, showing good performance in terms of current harmonic content. Then, the algorithm is applied to the case when four large vectors are used, further reducing the peak-to-peak CMV by 80% and still demonstrating a satisfactory performance. Both methods are experimentally compared to existing overmodulation algorithms obtaining better current quality and lower peak-to-peak CMV.

Multiphase machines in propulsion drives of electric vehicles

Multiphase electric drives have been recently proposed for applications where the highest overall system reliability and power distribution per phase are required. The propulsion drive of an Electric Vehicle (EV) is one of these applications. This paper deals with the use of a five-phase induction machine in the propulsion module of EVs, where the viability of a Predictive Torque Control method (PTC) is analyzed. Simulation results are provided to illustrate the potential of the method, showing fast speed response and low torque ripple.

SVM Procedure for

Space vector modulation (SVM) technique has become a standard method for the impression of voltage references in conventional three-phase voltage source inverters. The method is nowadays used in multiphase (more than three) drives, where linear and overmodulation regions are covered only for the five-phase case. This work proposes a general SVM procedure for linear and overmodulation regions in n -phase drives (being n any odd number, ) and simplifies the extension of SVM to the multiphase case. The proposed method achieves the reference voltage at the fundamental frequency while reducing introduced harmonic components in the overmodulation region compared to previous proposals.

n

Predictive control is becoming an alternative to standard vector control or direct torque control in electrical drives due to its fast torque response and design flexibility. In multiphase drives, where the complexity of the modulation techniques and control schemes is higher, the predictive control has proved to be a promising alternative. The main shortcoming of the standard predictive control (SPC) in multiphase drives is the high computational cost caused by the increased number of switching state possibilities. This work proposes a restrained search predictive control (RSPC) where some switching states are discarded by imposing several restrictions. The steady and transient states are explored, also examining the unbalance in the switching frequency of the voltage source inverter (VSI) legs and the effect of allowing submodulation. The advantages of the proposed control are discussed and the viability is confirmed by simulation.