Multiple load-source integration in a multilevel modular capacitor clamped DC-DC converter featuring fault tolerant capability

Journal ArticleAbstract-A multilevel modular capacitor clamped dc-dc converter (MMCCC) will be presented in this paper with some of its advantageous features. By virtue of the modular nature of the converter, it is possible to integrate multiple loads and sources to the converter at the same time. The modular construction of the MMCCC topology provides transformer like taps in the circuit, and depending on the conversion ratio of the converter, it becomes possible to connect several dc sources and loads at these taps. The modularity of the new converter is not limited to this transformer like operation, but also provides redundancy and fault bypass capability in the circuit. Using the modularity feature, some redundant modules can be operated in bypass state, and during any fault, these redundant modules can be used to replace a faulty module to maintain an uninterrupted operation. Thus, this MMCCC topology could be a solution to establish a power management system among multiple sources and loads having different operating voltages

Hybrid electric vehicle power management solutions based on isolated and nonisolated configurations of multilevel modular capacitor-clamped converter

Journal ArticleAbstract-This paper presents the various configurations of a multilevel modular capacitor-clamped converter (MMCCC), and it reveals many useful and new formations of the original MMCCC for transferring power in either an isolated or nonisolated manner. The various features of the original MMCCC circuit are best suited for a multibus system in future plug-in hybrid or fuel-cell-powered vehicles' drive train. The original MMCCC is capable of bidirectional power transfer using multilevel modular structure with capacitor-clamped topology. It has a nonisolated structure, and it offers very high efficiency even at partial loads. This circuit was modified to integrate single or multiple high-frequency transformers by using the intermediate voltage nodes of the converter. On the other hand, a special formation of the MMCCC can exhibit dc outputs offering limited isolation without using any isolation transformer. This modified version can produce a high conversion ratio from a limited number of components and has several useful applications in providing power to multiple low-voltage loads in a hybrid or electric automobile. This paper will investigate the origin of generating ac outputs from the MMCCC and shows how the transformer-free version can be modified to create limited isolation from the circuit. In addition, this paper will compare various modified forms of the MMCCC topology with existing dc-dc converter circuits from compactness and component utilization perspectives

Universal multilevel DC-DC converter with variable conversion ratio, high compactness factor and limited isolation feature

Journal ArticleA multilevel dc-dc converter with programmable conversion ratio (CR) is presented in this paper. This converter is a modified version of the MMCCC converter. A universal version of the MMCCC is developed in this paper, and the CR can be easily changed within a wide range. The MMCCC converter is based on capacitor-clamped topology, and the conversion ratio of the circuit depends on the number of active modules. However, like any other capacitor-clamped circuit, the MMCCC circuit requires a large number of transistors and capacitors to attain a high conversion ratio (CR). In this paper, a new circuit module will be introduced that can be connected in a cascade pattern to form the new converter. By using the new modular cell, it is possible to attain very high conversion ratio using a limited number of components, and thus more compactness compared to the predecessor MMCCC circuit can be achieved

A 5 kW Bi-directional multilevel modular DC-DC converter (MMCCC) featuring built in power management for fuel cell and hybrid electric automobiles

Journal ArticleAbstract- A new capacitor clamped modular dc-dc converter with bi-directional power handling capability will be presented in this paper. This inductor-free design is modular, and it is possible to integrate multiple loads and sources simultaneously in the converter. Moreover, this 5 kW dc-dc converter can produce multiple ac outputs to feed power to ac loads get further control over the conversion ratio of the circuit. This high efficiency modular converter has flexible conversion ratio, and it could be successfully used in a multi-bus power system by virtue of its inherent power management properties

Generating isolated outputs in a multilevel modular capacitor clamped DC-DC converter (MMCCC) for hybrid electric and fuel cell vehicles

Journal ArticleThis paper presents a new technique to obtain isolated dc voltage outputs from a capacitor clamped dc-dc converter. The multilevel modular capacitor clamped converter (MMCCC) has several key features that make it possible to generate ac outputs (10 kHz) from a dc-dc converter circuit. Using those high frequency ac outputs, the MMCCC circuit can incorporate single or multiple high frequency transformers to generate isolated ac outputs. These isolated outputs can be rectified and filtered to obtain unidirectional or bi-directional dc outputs. Using another MMCCC converter stage or an active full bridge block, the ac port can be made bi-directional to transfer power in both directions. By adopting the MMCCC topology to achieve isolated outputs, it is possible to simultaneously integrate multiple dc sources in an isolated and non-isolated manner. This paper will investigate the origin of the ac outputs in the MMCCC circuit, and present an analytical approach to estimating the isolated dc output voltage. Finally, experimental results will be presented for further verification of the concept

Examination of a PHEV bidirectional charger system for V2G reactive power compensation

Abstract—Plug-in hybrid electric vehicles (PHEVs) potentially have the capability to fulfill the energy storage needs of the electric grid by supplying ancillary services such as reactive power compensation, voltage regulation, and peak shaving. However, in order to allow bidirectional power transfer, the PHEV battery charger should be designed to manage such capability. While many different battery chargers have been available since the inception of the first electric vehicles (EVs), on-board, conductive chargers with bidirectional power transfer capability have recently drawn attention due to their inherent advantages in charging accessibility, ease of use, and efficiency. In this paper, a reactive power compensation case study using just the inverter dc-link capacitor is evaluated when a PHEV battery is under charging operation. Finally, the impact of providing these services on the batteries is also explained

High Dynamic Performance Programmed PWM Control of a Multilevel Inverter with Capacitor DC Sources

A cascade multilevel inverter consisting of a standard 3-leg inverter supplied by a DC source and three full H-bridges each supplied by a capacitor is considered for use as a motor drive. The capacitor H-bridges can only supply reactive voltage to the motor while the standard three leg inverter can supply both reactive and active voltage. A switching control algorithm is presented that shows this inverter topology can be used as an AC drive achieving considerable performance advantages (e.g., higher motor speed) compared to using a standard 3-leg inverter while at the same time regulating the capacitor voltages. The converter controller is a fundamental frequency switching controller based on programmed PWM to achieve higher efficiency (less power losses in the switches) compared to high-frequency PWM approaches. As is well known, the programmed PWM switching times are computed assuming the drive is in sinusoidal steady-state, that is, the derived switching angles achieve the fundamental while rejecting specified harmonics if the voltage waveforms are in sinusoidal steady-state. Here it shown that the switching commands to the converter can be implemented in a smooth fashion for voltage waveform commands whose frequency and amplitudes are continuously varying

Conditions for Capacitor Voltage Regulation in a Five-Level Cascade Multilevel Inverter: Application to Voltage-Boost in a PM Drive

A cascade multilevel inverter is a power electronic device built to synthesize a desired AC voltage from several levels of DC voltages. Such inverters have been the subject of research in the last several years, where the DC levels were considered to be identical in that all of them were either batteries, solar cells, etc. Similar to previous results in the literature, the work here shows how a cascade multilevel inverter can be used to obtain a voltage boost at higher speeds for a three-phase PM drive using only a single DC voltage source. The input of a standard three-leg inverter is connected to the DC source and the output of each leg is fed through an H-bridge (which is supplied by a capacitor) to form a cascade multilevel inverter. A fundamental switching scheme is used, which achieves the fundamental in the output voltage while eliminating the fifth harmonic. A new contribution in this paper is the development of explicit conditions in terms of the power factor and modulation index for which the capacitor voltage of the H-bridges can be regulated while simultaneously maintaining the aforementioned output voltage. This is then used for a PM motor drive showing the machine can attain higher speeds due to the higher output voltage of the multilevel inverter compared to using just a three-leg inverter

Reduced Switching-Frequency Active Harmonic Elimination for Multilevel Converters

This paper presents a reduced switching-frequency active-harmonic-elimination method (RAHEM) to eliminate any number of specific order harmonics of multilevel converters. First, resultant theory is applied to transcendental equations to eliminate low-order harmonics and to determine switching angles for a fundamental frequency-switching scheme. Next, based on the number of harmonics to be eliminated, Newton climbing method is applied to transcendental equations to eliminate high-order harmonics and to determine switching angles for the fundamental frequency-switching scheme. Third, the magnitudes and phases of the residual lower order harmonics are computed, generated, and subtracted from the original voltage waveform to eliminate these low-order harmonics. Compared to the active-harmonic-elimination method (AHEM), which generates square waves to cancel high-order harmonics, RAHEM has lower switching frequency. The simulation results show that the method can effectively eliminate all the specific harmonics, and a low total harmonic distortion (THD) near sine wave is produced. An experimental 11-level H-bridge multilevel converter with a field-programmable gate-array controller is employed to experimentally validate the method. The experimental results show that RAHEM does effectively eliminate any number of specific harmonics, and the output voltage waveform has low switching frequency and low THD

DC-AC Cascaded H-Bridge Multilevel Boost Inverter with No Inductors for Electric/Hybrid Electric Vehicle Applications

This paper presents a cascaded H-bridge multilevel boost inverter for electric vehicle (EV) and hybrid EV (HEV) applications implemented without the use of inductors. Currently available power inverter systems for HEVs use a dc–dc boost converter to boost the battery voltage for a traditional three-phase inverter. The present HEV traction drive inverters have low power density, are expensive, and have low efficiency because they need a bulky inductor. A cascaded H-bridge multilevel boost inverter design for EV and HEV applications implemented without the use of inductors is proposed in this paper. Traditionally, each H-bridge needs a dc power supply. The proposed design uses a standard three-leg inverter (one leg for each phase) and an H-bridge in series with each inverter leg which uses a capacitor as the dc power source. A fundamental switching scheme is used to do modulation control and to produce a five-level phase voltage. Experiments show that the proposed dc–ac cascaded H-bridge multilevel boost inverter can output a boosted ac voltage without the use of inductors