Simple Carrier-based Pulse Width Modulation Research Articles

Simple Carrier-Based PWM for Prolonged High DC-Link Utilization for Symmetrical and Asymmetrical $n$-Phase AC Drives

Square voltage waveforms enable high dc-link utilization (DLU) in multiphase ac drives. Circulating-current filters were devised to attenuate the harmonics in no-torque low-impedance subspaces. Nonetheless, the square-wave harmonics that generate torque ripple are not reduced. Recently, it was proposed to combine circulating-current filters with a carrier-based pulsewidth modulation (PWM) method, which injects harmonics in no-torque subspaces (attenuated by the filter) of five-phase motors to achieve high DLU, without harmonics associated with torque ripple. The filter allows prolonged high-DLU operation without overheating. Compared with other PWM techniques capable of high-DLU operation (overmodulation), the one proposed for said filters is especially convenient because of its simplicity. However, it is unclear if this PWM method can be extended to machines of any phase number n and winding arrangement (symmetrical or asymmetrical); and if so, the resulting performance is also unknown. This article extends this simple carrier-based PWM strategy to n-phase drives, and evaluates its behavior in terms of DLU, distortion, and computational burden. Symmetrical and asymmetrical winding arrangements are considered. The improvement in DLU, compared with conventional PWM with zero-sequence injection, is considerable. Current distortion is negligible with a suitable filter. The simplicity over other high-DLU PWM techniques is remarkable. Experimental results are provided.

Uniform carrier‐based PWM method for three‐phase three‐level three‐wire and four‐wire converter system with neutral‐point balancing

In this study, a simple carrier-based pulse-width modulation (CBPWM) method is proposed for a three-phase three-level neutral-point-clamped converter with neutral-point (NP) balancing, which can be applied to three-phase three-wire (TPTW) and three-phase four-wire (TPFW) converter systems simultaneously. First, the effect of each switching state for the NP potential in TPTW and TPFW systems is analysed in detail, and a newly NP control strategy by reconstructing the switching state and adjusting the corresponding duration time is deduced for all operation conditions, it only needs to add the offset voltage to the modulation reference voltage to guarantee the NP balance and is easy to implement. Then, under all operating conditions, the mathematical model of NP current is derived and analysed to evaluate the low-frequency voltage oscillation in the NP. Finally, the effectiveness and feasibility of the proposed CBPWM strategy are verified by the experimental results based on a 12 kVA laboratory prototype.

Improvement in DC-Link Utilization With Reduced Current and Torque Deterioration for Five-Phase Drives by Combination of Circulating-Current Filters and Simple Carrier-Based PWM Based on Closed-Form Expressions

Multiphase drives offer important advantages over three-phase ones. With pulsewidth modulation (PWM), zero-sequence and x-y signals can be injected to enhance dc-link utilization (DLU). For example, in five-phase drives, for given dc-link voltage, the fundamental is raised by 23.1%. For sinusoidally distributed windings, although x-y currents increase losses, torque is unaffected. However, no simple carrier-based PWM methods based on closed-form expressions have been presented for this purpose so far. Most importantly, x-y currents may be unacceptably large, due to the small x-y impedance. This is particularly troublesome when high fundamental voltage is needed continuously. Applying square waveform instead of PWM raises the fundamental from 23.1 to 27.3%. Given the square-voltage distortion, filters with large x-y impedance were devised for this approach. However, some square-waveform harmonics map into the torque-producing plane without attenuation, generating torque ripple. This article proposes to use a simple carrier-based PWM method in five-phase drives combined with a circulating-current filter. The x-y voltages, which see large filter impedance, are exploited to achieve a high DLU similar to previous solutions, but without torque ripple or excessive x-y currents. Guidelines are given for designing the filter when used with the presented PWM strategy. Experimental results verify the proposal.

An Instantaneous Power Balancing Technique for an Open-End IM Drive Using Carrier-Based Modulation for Vehicular Application

A multilevel drive can be realized by using an open-ended machine, fed from dual two-level inverters. The topology supplied from isolated dc sources is suitable for transportation electrification. In vehicular systems, it is essential that the isolated dc sources, comprising of battery packs, should discharge uniformly and maintain balanced dc voltage at the dc-link terminal. A simple carrier-based pulsewidth modulation (PWM) technique is presented in this paper, which can effectively regulate the power drawn between the two two-level inverters while maintaining the multilevel operation of the drive. The modulation technique can balance the instantaneous state of charge of independent battery packs and dynamically equalize the power flow from the two inverters, based on drive requirement. This will enhance the reliability of the propulsion system in electric vehicles. The operation of the proposed PWM technique has been validated through detailed simulation and experimental tests.

Bidirectional Three-Phase DC–AC Converter With Embedded DC–DC Converter and Carrier-Based PWM Strategy for Wide Voltage Range Applications

A bidirectional three-phase dc–ac converter with embedded dc–dc converter for bidirectional storage interface is proposed in this paper. With the help of the embedded dc–dc converter, the voltage of the storage battery can vary in a wide range. To minimize the power rating and power losses of the embedded dc–dc converter, a simple carrier-based pulsewidth modulation (PWM) strategy with zero-sequence injection is proposed. By adopting the proposed PWM strategy, only a small ratio of total power needs to be processed by the embedded dc–dc converter, while most of the power is only processed by the three-phase dc–ac stage within a single conversion stage. As a result, quasi single-stage power conversion is achieved to improve the conversion efficiency of the overall dc–ac power system. Principles, characteristics, and implementations of the proposed three-phase dc–ac converter and its PWM strategy are analyzed in detail. The feasibility and effectiveness of the proposed solutions are verified with experimental results.

Simple carrier-based pulse-width modulation technique for a three-to-quasi-six-phase matrix converter

Simple carrier-based pulse-width modulation technique for a three-to-quasi-six-phase matrix converter

Carrier-based pulse width modulation technique for a three-to-five phase matrix converter for supplying five-phase two-motor drives

Multi-phase (more than three-phase) converters are required mainly for feeding variable speed multi-phase drive systems. This paper discusses one such solution by using direct ac-ac converter that can be used to supply a five-phase two-motor drive system. Matrix converter based two-motor drive system is presented for the first time in this paper. Two stator windings of two five-phase machines when connected in seires/parallel while the rotors may be connected to different laods, are called series/parallelconnected two-motor drive. Appropriate phase transposition is introuduced while connecting the series/parallel stator winding to obtain decoupled control of the two machines. This paper proposes simple carrier-based Pulse width modulation (PWM) technique of three-phase to five-phase matrix converter supplying series-connected five-phase AC machine drive system. The developed modulation technique is based on the comparison of high frequency carrier signal with the input voltages, similar to the one used in voltage source inverter. Although carrier-based scheme is widely employed for control of voltage source inverter, it is very recently being used for a matrix converter. The similar concept is extended in this paper for controlling a three-phase to five-phase matrix converter. The major aim of the PWM is to generate two independent fundamental frequency components that will subsequently control two series/parallel connecetd five-phase motor. The viability of the proposed control techniques is proved using analytically and simulation approach. Keywords: Carrier-based PWM, Matrix converter, modulation, five-phase, AC machine, drive International Journal of Engineering, Science and Technology, Vol. 2, No. 10, 2010, pp. 67-78