Passivation of Grid-Following VSCs: A Comparison Between Active Damping and Multi-Sampled PWM

This article compares different strategies used to enhance the stability properties of grid-following voltage-source converters (VSCs). Because of digital delays, VSC admittance exhibits a nonpassive zone, which introduces negative damping and may destabilize the grid-connected operation. It is shown that typically used active damping (AD) strategies only bring positive impact up to a certain frequency, while deteriorating admittance properties around and above the Nyquist frequency. Multi-sampled pulsewidth modulation (MS-PWM) greatly extends the passive admittance region, using only a single-loop current controller. Experimental admittance measurements are performed on a single-phase VSC, up to twice the switching frequency. Subsequently, different grid-connected scenarios are tested to show that MS-PWM retains stable operation, where AD methods cause instability. This article also offers analytic modeling and experimental measurements of noise propagation for compared strategies. It is shown that derivative-based AD is not highly sensitive; however, MS-PWM offers additional noise suppression

Bidirectional DC-DC Converter Topologies for Low-Voltage Battery Interface: Comparative Assessment

The growing interest towards efficient and reliable bidirectional DC-DC converter topologies for interfacing low-voltage (LV) batteries, eg. 48 V, with a high-voltage (HV) DC-link, eg. 400 V, has driven the research toward the investigation of many different topologies. In this paper, three isolated and bidirectional topologies have been selected and compared to each other, where these topologies are seen as the state-of-the-art topologies for battery-fed systems. The introduced comparison includes the number of used semiconductor devices and passive elements, the rated voltage and current of the different semiconductor devices, the forecasted switching and conduction losses using PLECS, and the estimated volume and power losses of the employed magnetic elements. Furthermore, the comparison includes simulation results using PLECS considering a 1.5 kW power level

Analysis and Performance Evaluation of a Two-Stage Resonant Converter for Wide Voltage Range Operation

This paper proposes a two-stage isolated dc-dc converter for electric vehicle charging applications, where high efficiency over a wide range of battery voltages is required. It employs a first pre-regulation stage and a second half-bridge LLC stage, integrated with the first. The second stage is always operated at resonance, ensuring very high efficiency. The first pre-regulation stage is responsible for the desired input-to-output voltage conversion ratio and the zero-voltage switching operation of all the switches. This allows low conversion losses even with voltages that may vary over a wide range. The conversion structure is shown considering a first experimental prototype that interfaces a 750-V dc-link with an output bus with nominal voltage range 250V-500V. The implemented module is rated 5 kW and achieves a peak efficiency of 98.0% at 3 kW output power