Multilevel multiphase space vector PWM algorithm

In the last few years, interest in multiphase converter technology has increased due to the benefits of using more than three phases in drive applications. Besides, multilevel converter technology permits the achievement of high power ratings with voltage limited devices. Multilevel multiphase technology combines the benefits of both technologies, but new modulation techniques must be developed in order to take advantage of multilevel multiphase converters. In this paper, a novel space vector pulsewidth modulation (SVPWM) algorithm for multilevel multiphase voltage source converters is presented. This algorithm is the result of the two main contributions of this paper: the demonstration that a multilevel multiphase modulator can be realized from a two-level multiphase modulator, and the development of a new two-level multiphase SVPWM algorithm. The multiphase SVPWM algorithm presented in this paper can be applied to most multilevel topologies; it has low computational complexity and it is suitable for hardware implementations. Finally, the algorithm was implemented in a low-cost field-programmable gate array and it was tested in a laboratory with a real prototype using a five-level five-phase inverter.Ministerio de Educación y Ciencia | Ref. ENE2006-0293

Asenkron motorlar için ayarlanabilir gerilim uygulamalı V/f tabanlı hız denetiminde farklı PWM tekniklerinin performans analizi

This paper presents a comparative study and a method to improve Volt-Hertz (V/f) based speed control of Induction Motors (IMs). For this purpose, Sinusoidal Pulse Width Modulation (SPWM) and space vector pulse width modulation (SVPWM) techniques are investigated and evaluated, especially from the point of their control performance on the V/f-based control for three-phase IMs working at different load and speed conditions. From this aspect, it is a different study from the literature. Steady and transient effects of both techniques on the above mentioned control methods are analyzed for several case studies. Afterwards, adjustable boost voltage application with modified reference commands technique is proposed for both PWM methods in order to improve start-up performance. All investigations for both PWM models are carried out under the same conditions. Although SVPWM technique gives more effective results in many cases, the proposed method provides noticeable improvements on SPWM-based applications from point of performance on the control method. As a novelty of this study, it is shown that, the bad performance of the control method at low frequency in SPWM application, which has lower computational burden for low cost microcontroller, can be improved by applying adjustable boost voltage along with modified references that are proportional to the DC bus current

Multilevel multiphase space vector PWM algorithm with switching state redundancy

Multilevel multiphase technology combines the benefits of multilevel converters and multiphase machines. Nevertheless, new modulation techniques must be developed to take advantage of multilevel multiphase converters. In this paper, a new space vector pulsewidth modulation algorithm for multilevel multiphase voltage source converters with switching state redundancy is introduced. As in three-phase converters, the switching state redundancy permits to achieve different goals like extending the modulation index and reducing the number of switchings. This new algorithm can be applied to the most usual multilevel topologies; it has low computational complexity, and it is suitable for hardware implementations. Finally, the algorithm was implemented in a field-programmable gate array, and it was tested by using a five-level five-phase inverter feeding a motor.Ministerio de Educación y Ciencia | Ref. ENE2006-0293

Comparison of Three Space Vector PWM Methods for a Three-Level Inverter with a Permanent Magnet Machine Load

Much work exists on multilevel space vector pulse width modulation (PWM) to drive induction machines, in which the rotor currents are induced by stator rotating field effects. However, there are few investigations that analyze these modulation methods applied to permanent magnet (PM) and wound-field synchronous machines, in which the rotor induces a back emf in the stator. In this thesis, three different three-level space vector PWM switching sequences are applied to a three-level neutral-point-clamped (NP) inverter driving an internal permanent magnet (IPM) machine load. The inherent qualities of each of the switching sequences when under the influence of a forcing function (the back emf) created by the permanent magnets of the machine are investigated. In particular, output voltage quality, output current quality, and dc bus neutral point balance are analyzed and compared. Two machine operating conditions are considered: rated speed, rated load and half speed, rated load. By considering these two different operating speeds, the three switching sequences may be analyzed under both two-level operation and three-level operation of the inverter. A circuit model based on the machine state space model in the abc current frame of reference is used to model the IPM machine load. First, a short introduction to two-level inverters and a theoretical development of two-level space vector PWM are presented to introduce these basic principles. Then, an overview of the three main multilevel inverter topologies including their associated advantages and disadvantages is presented. A theoretical development of three-level space vector PWM is built upon the concepts introduced in the two-level case, and the three switching sequences under investigation are explained. The system model, including the IPM machine load, the three-level NPC inverter, and the space vector PWM algorithms, is implemented using MATLAB Simulink. All simulation results are analyzed based on output voltage and current distortion and neutral point imbalance, and a comparison between the three switching sequences is presented

Space vector pulse-width modulation for multilevel inverters and solution to modulation dependent problems

Ph.DDOCTOR OF PHILOSOPH

High efficiency solar power generation with improved discontinuous pulse width modulation (DPWM) overmodulation algorithms

The efficiency of a photovoltaic (PV) system strongly depends on the transformation process from solar energy to electricity, where maximum power point tracking (MPPT) is widely regarded as a promising technology to harvest solar energy in the first step. Furthermore, inverters are an essential part of solar power generation systems. Their performance dictates the power yield, system costs and reliable operation. This paper proposes a novel control technology combining discontinuous pulse width modulation (DPWM) and overmodulation technology to better utilize direct current (DC) electrical power and to reduce the switching losses in the electronic power devices in conversion. In order to optimize the performance of the PV inverter, the overmodulation region is refined from conventional two-level space vector pulse width modulation (SVPWM) control technology. Then, the turn-on and turn-off times of the switching devices in different modulation areas are deduced analytically. A new DPWM algorithm is proposed to achieve the full region control. An experimental platform based on a digital signal processing (DSP) controller is developed for validation purposes, after maximum power is achieved via a DC/DC converter under MPPT operation. Experimental results on a PV system show that the DPWM control algorithm lowers the harmonic distortion of the output voltage and current, as well as the switching losses. Moreover, better utilization of the DC-link voltage also improves the PV inverter performance. The developed algorithm may also be applied to other applications utilizing grid-tie power inverters

POWER QUALITY CONTROL AND COMMON-MODE NOISE MITIGATION FOR INVERTERS IN ELECTRIC VEHICLES

Inverters are widely utilized in electric vehicle (EV) applications as a major voltage/current source for onboard battery chargers (OBC) and motor drive systems. The inverter performance is critical to the efficiency of EV system energy conversion and electronics system electro-magnetic interference (EMI) design. However, for AC systems, the bandwidth requirement is usually low compared with DC systems, and the control impact on the inverter differential-mode (DM) and common-mode (CM) performance are not well investigated. With the wide-band gap (WBG) device era, the switching capability of power electronics devices drastically improved. The DM/CM impact that was brought by the WBG device-based inverter becomes more serious and has not been completely understood. This thesis provides an in-depth analysis of on-board inverter control strategies and the corresponding DM/CM impact on the EV system. The OBC inverter control under vehicle-to-load (V2L) mode will be documented first. A virtual resistance damping method minimizes the nonlinear load harmonics, and a neutral balancing method regulates the unbalanced load impact through the fourth leg. In the motor drive system, a generalized CM voltage analytical model and a current ripple prediction model are built for understanding the system CM and DM stress with respect to different modulation methods, covering both 2-level and 3-level topologies. A novel CM EMI damping modulation scheme is proposed for 6-phase inverter applications. The performance comparison between the proposed methods and the conventional solution is carried out. Each topic is supported by the corresponding hardware platform and experimental validation

PWM strategies fo multilevel multiphase AC drives

Pulse width modulation (PWM) strategies for multilevel multiphase ac drives have been analysed in this thesis. The large amount of published work in the area of multiphase drives recognises their advantages compared to the standard three-phase solutions. Some of them arc improved power sharing capabilities, increased reliability and fault tolerance. However, in the most of these works two-level inverters were used for supply of multiphase machine. Also, huge amount of research has been done in the area of multi level inverters. Nowadays, three-phase multilevel inverters are in use in high-power applications. However. the ideal scenario for high-power applications is supply of a multi phase machine from the multilevel inverters. So far no negative consequences of combination of these two topologies, apart from increased complexity of the system, have been identified, and this topology is the subject of this thesis