Optimization-Based Capacitor Balancing Method with Selective DC Current Ripple Reduction for CHB Converters

From its introduction to the present day, Cascaded H-Bridge multilevel converters were employed on numerous applications. However, their floating capacitor, while advantageous for some applications (such as photovoltaic) requires the usage of balancing methods by design. Over the years, several such methods were proposed and polished. Some of these methods use optimization techniques or inject a zero-sequence voltage to take advantage of the converter redundancies. This paper describes an optimization-based capacitor balancing method with additional features. It can drive each module DC-Link to a different voltage for independent maximum power point tracking in photovoltaic applications. Moreover, the user can specify the independent active power set points to modules connected to batteries or any other energy storage systems. Finally, DC current ripple can be reduced on some modules, which can extend the lifespan of any connected ultra-capacitors. The method as a whole is tested on real hardware and compared with the state-of-the-art. In its simplest configuration, the presented method shows greater speed, robustness, and current wave quality than the state-of-the-art alternative in spite of producing about 1/3 fewer commutations. Its other characteristics provide additional functionalities and improve the adaptability of the converter to other applications.

Comparison of Interleaving Methods of Parallel Connected Three-Level Bi-Directional Converters

The voltage and current ripples in the three-level bi-directional converter (TLBC) can be reduced by an interleaving technique that controls a phase difference between the modules of power converter. On the other hand, the inductor current ripple in TLBC is increased due to the circulating current between the modules. In this paper, the effects of two interleaving methods on a two-phase TLBC, Z-type and N-type, are investigated and compared. In particular, capacitor current ripple, and voltage ripple are compared by two interleaving methods verified through Powersim (PSIM) simulation.

DC traction power substation using eighteen-pulse rectifier transformer system

<span lang="EN-US">Twelve-pulse rectification system had been widely integrated in today’s DC traction power sub-station (DC-TPSS). This configuration had successfully mitigated low order harmonic distortion. As some research findings had confirmed that the dc voltage and current ripple factors may further minimize by increasing the number of rectification pulses to 18, 24, or 36. This paper had presented a simulation study to investigate the prospect of implementing an eighteen-pulse rectification system in a DC-TPSS. The theory of phase-shifting transformer used to produce an 18-pulse rectifier is presented with simulation verification. Simulation result shows that 3.69% of grid current distortion index is recorded without installing any filters. In addition, the dc voltage and current ripple may also be further reduced for about 30% compared to a conventional twelve-pulse rectification system.</span>

Simulation of Shield Current in Automotive High Voltage Systems

In automotive high voltage (HV) systems, the switching operation of a power electronic converter causes current and voltage ripple in the frequency range of [10 Hz–150 kHz]. Automotive system engineering provides requirements that define the behaviour of HV components in that frequency range. Shielded HV cables must stand induced current in the frequency range of the ripple. One of the relevant requirements is the maximal current stress of the shielding. Several individually shielded cables are used in automotive HV systems, and these shields influence differential mode disturbance currents, such as the ripple current from the traction inverter. In this work, we provide a model and an analysis of shielded cables integrated into an automotive HV system in relation to system-level design parameters. To fill the gaps of existing research, we focused on two questions: How do design parameters influence the shield current value in the frequency range of the current ripple in a vehicle, and how should a shield and connector system be designed with respect to shield currents over the life-time? We applied analytical and simulative solutions to these problems through a co-simulation approach on the architecture of a real vehicle. The presented approach extends existing research by integrating simulations and vehicle measurements to life-time prediction. Moreover, the proposed methods enable the replacement of the state-of-the-art constant 10 A requirement to a driver profile based predicted shield current requirement on individually shielded HV cables in battery electric vehicles (BEV).

Design a H-bridge low ripple and high bandwidth air core magnet corrector power supply in NSRRC

This paper is the study of a low-current-ripple and high-bandwidth corrector power supply. The main circuit of this power supply is using a full bridge (H-bridge) structure, and the output current through the high-precision direct current current transducers (DCCT) to transfer the reference voltage to the controller. Previous TPS corrector power supply had a 4.7 kHz current bandwidth, and its output current ripple was 100 μA. Such current ripple and bandwidth do not satisfy the requirements of a rapidly orbiting feedback system of air core loading. Therefore, our research team designed a novel prototype power supply with a high bandwidth (more than 10 kHz) and low output current ripple (less than 10 μA) which was developed via a novel topology circuit. The operation frequency of the main power switch's n-type metal-oxide-semiconductor logic of this novel circuit is increased to 245 kHz. Moreover, the output results of the filter inductor and filter capacitor are modified to 80 μH and 2.46 μF, respectively. The prototype power supply bandwidth reached 10.546 kHz and increase of 124% and its output current ripple was lowered below than 5 μA. The properties of this corrector power supply are very important for the beam correction in storage rings. Finally, A circuit with an input voltage of 48 V, a maximum output current of 10 A, and an output power of 400 W is tested in a laboratory to verify the performance of the developed corrector for the National Synchrotron Radiation Research Center.

Differential Evolution Based Algorithm for Optimal Current Ripple Cancelation in an Unequal Interleaved Power Converter

This paper proposes an optimal methodology based on the Differential Evolution algorithm for obtaining the set of duty cycles of a recently proposed power electronics converter with input current ripple cancelation capability. The converter understudy was recently introduced to the state-of-the-art as the interleaved connection of two unequal converters to achieve low input current ripple. A latter contribution proposed a so-called proportional strategy. The strategy can be described as the equations to relate the duty cycles of the unequal power stages. This article proposes a third switching strategy that provides a lower input current ripple than the proportional strategy. This is made by considering duty cycles independently of each other instead of proportionally. The proposed method uses the Differential Evolution algorithm to determine the optimal switching pattern that allows high quality at the input current side, given the reactive components, the switching frequency, and power levels. The mathematical model of the converter is analyzed, and thus, the decision variables and the optimization problem are well set. The proposed methodology is validated through numerical experimentation, which shows that the proposed method achieves lower input current ripples than the proportional strategy.