Optimal Synergetic Control of Three-Phase/Level Boost–Buck Voltage DC-Link AC/DC Converter for Very-Wide Output Voltage Range High-Efficiency EV Charger
Daifei Zhang, Christos Leontaris, Jonas Huber, Johann W. Kolar
Abstract
Universal high-power three-phase (3- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Phi $ </tex-math></inline-formula> ) mains interfaces for electric vehicle (EV) charging must provide a wide output voltage range (e.g., 200–800 V) and, thus, provide buck and boost capability. An advantageous realization combining a three-level (3-L) T-type (Vienna) boost-type power-factor-correcting (PFC) voltage source rectifier (VSR) with a 3-L buck-type DC/DC converter stage is presented in this article. For high output voltages (boost mode), the VSR-stage operates with 3/3-pulsewidth modulation (PWM), i.e., continuous PWM of all three phases to regulate the output voltage, while the DC/DC-stage remains clamped to avoid switching losses. For low output voltages (buck mode), the DC/DC-stage advantageously controls the DC-link voltage according to a time-varying reference value, which allows to sinusoidally shape the currents of two mains phases, such that the VSR-stage can operate with 1/3-PWM (only one of the three bridge legs operates with PWM at any given time) with reduced switching losses. This article proposes a novel 2/3-PWM scheme for the output voltage transition region, where output voltages are between the buck mode and the boost mode. This enables loss-optimum operation (i.e., the minimum number of the VSR-stage bridge legs operating with PWM, and with the minimum possible DC-link voltage) for any output voltage. Furthermore, this article introduces a new synergetic control concept that ensures seamless transitions between the loss-optimum operating modes. A comprehensive experimental verification, including precompliance EMI measurements, using a 10-kW hardware demonstrator with a power density of 5.4 kW/dm 3 (91 W/in 3), a peak efficiency of 98.8% at rated power and 560-V output voltage, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${>}98$ </tex-math></inline-formula> % efficiency for all operating points with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${>}400$ </tex-math></inline-formula> -V output voltage and more than about 50% of rated power confirms the theoretical analyses.