Balancing converters play a pivotal role in bipolar dc grids, and while numerous topologies have been explored, many suffer from drawbacks, such as reliance on bulky passive components, limited soft-switching capabilities, or complex control mechanisms. This article introduces an LC series-resonant balancing converter topology that addresses these issues, featuring smaller passive components, the ability to achieve soft switching across its entire operational range, and simplified control with proper design. By operating in the capacitive region, the converter ensures soft switching for the complete load range, enabling all switches to achieve zero voltage switching (ZVS) turn on. The study reveals that the converter's power flow depends on both the switching frequency (fsw) and the phase shift angle (φ), but notably, when the resonant inductor value is kept sufficiently low, fsw and φ become decoupled, simplifying power flow control. In addition, this article provides detailed design guidelines for the converter's resonant tank and validates the operation and control of the converter through an experimental setup.

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This paper presents a control strategy for active power decoupling in a Solid State Transformer (SST) using a cascaded H-bridge (CHB) converter, dual active bridge (DAB) converters, and a high-frequency link (HFL). The strategy balances capacitor voltage and decouples power flow, significantly reducing second harmonic voltage ripple in DC link capacitors and potentially reducing their size.

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This article discusses the various operating modes of a series resonant balancing converter for bipolar dc grids. It is shown that the converter can be operated in both the capacitive and inductive regions with respect to the resonant frequency of the LC tank. Furthermore, concerning the pulse width modulation signals to the switches, the converter can either be operated by controlling the phase shift between the converter half bridge legs or the duty cycle of the half bridges. A qualitative comparison of the different modes proves that a) the phase shift modes have better soft switching capabilities, b) the capacitive phase shift mode can show zero voltage switching at switch turn-on in the whole operating range, c) the losses in case of capacitive phase shift mode shows best performance at low load power, d) the inductive region power modes show lower rms current for the same power flow compared with capacitive region modes which lead to lower losses at higher output power. The simulation and experimental results depict the operation of all the modes. Finally, a prototype is designed to validate all operating modes, demonstrating $>$99% system efficiency at 1.75 kW.@en

This article provides the design procedure of a ±350 V series resonant balancing converter for bipolar DC grids. The process creates a η-ρ Pareto front to design a 3 kW converter with natural convection cooling.

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Triangular current mode (TCM) zero-voltage switching (ZVS) modulation method is widely adopted in power electronic converters to achieve acceptable efficiency in high switching frequency operations. For bidirectional dc-dc converters, in order to realize ZVS turn-on, a reverse inductor current can be utilized for this purpose through variable frequency control. In this article, this reverse switched current is revisited considering the parasitic resistances presented in the mosfet switches and the inductor for three common types of dc-dc converters, i.e., buck, boost, and buck-boost converters, which study was normally neglected in the previous research. Universal closed-form equations of the modified duty cycle and switched current are derived, which can be utilized to calculate the reverse current under different operating conditions. It is found that the parasitic resistances can have a negative impact on the switched current value, and this may lead to an unexpected loss of ZVS turn-on. A laboratory prototype of a four-switch buck+boost converter featuring TCM-ZVS buck, boost, and buck-boost operation capability was built to investigate and verify the proposed concepts. The operating voltage and power range are from 100 V to 400 V, and 300 W to 1 kW, respectively.

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Series-connected MOSFETs with lower voltage ratings can be an alternative for single high-voltage switches. This paper compares two switch configurations for the soft-switched power converter topology targeted for a 1400V DC grid. The first configuration is a single switch rated at 1700V whereas the other is a series connected two MOSFETs rated at 900V. A buck converter with 1400V and 700V as input and output voltages respectively is taken as a case study. Triangular current modulation (TCM) ensures zero voltage switching (ZVS) at turn-on for all the switches. The analysis shows that the series-switch configuration can have much lower overall losses than the single-switch configuration.@en

Balancing converters are an integral part of a bipolar dc grid. In this paper, we propose a balancing converter based on a series resonant converter topology. The converter operates in the capacitive region with phase shift between the upper and lower H-bridges. The converter operation is analyzed and verified with LTSpice simulation. A prototype is developed to verify the operation.@en

Balancing converters are an integral part of a bipolar dc grid. Resonant converter topologies are interesting for power electronics engineers due to their soft switching capabilities. A series resonant converter topology is promising as a balancing converter in a bipolar dc grid. The series resonant converter is usually a non-inverting topology. However, in the balancing converter application, the converter is used as an inverting type, like a buck-boost converter topology. In this paper, the soft switching capabilities of this converter are shown and analyzed for four distinct converter modulation schemes.

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Electrification of ships is one of the hot topics in the marine industry. This is due to the stringent guidelines by the International Maritime Organisation (IMO) for curbing the green house gas emissions from the marine sector. In this paper, the state-space modeling approach is used to model bipolar dc grids on ships. A ferry is used as a test case. The modeling is done for the radial and zonal architecture with similar components. The dynamic simulation and stability analysis of the two architectures reveal that zonal architecture is potentially more stable than the radial architecture.

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