Ruiyang Yu
North Carolina State University
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Publication
Featured researches published by Ruiyang Yu.
conference of the industrial electronics society | 2014
Kai Tan; Ruiyang Yu; Suxuan Guo; Alex Q. Huang
The isolated DC/DC stage in solid state transformer (SST) is a very critical stage in the whole system. It converts the high DC voltage to low DC voltage with the galvanic isolation after the high voltage AC/DC rectifier and before the low voltage DC/AC inverter. In previously developed solid state transformers, dual active bridge (DAB) and dual half bridge (DHB) are the most common topology for this part. In this paper, a bidirectional LLC resonant converter is presented to replace the traditional DAB or DHB in SST application. Compared with DAB, the bidirectional LLC converter can achieve higher efficiency with wider range of zero voltage switching (ZVS), zero current switching (ZCS) and simpler control strategy, which makes it highly attractive for solid state transformer applications. The converter operation modes are presented and analyzed in this paper. For achieving higher efficiency, a methodology of hardware design optimization is introduced to minimize the power losses. Analysis, simulation and experimental results based on a scaled down prototype are shown and discussed.
applied power electronics conference | 2015
Fei Xue; Ruiyang Yu; Wensong Yu; Alex Q. Huang; Yu Du
This paper presents a high efficiency, low-cost bidirectional isolated dc-dc converter for distributed energy storage device (DESD). Derived from dual active bridge (DAB), the proposed converter consists of a half-bridge circuit at high voltage side and a push-pull circuit with active clamp at low voltage side. The proposed topology is attractive in low voltage and high current applications and it also reduces the number of switching transistors such that the cost and complexity are considerably reduced. With single phase-shift control strategy, all the switches operate in zero-voltage switching (ZVS) condition without increasing circuit complexity. Besides, planar transformer is implemented where the low voltage windings consist of PCB trace and external copper foils. A 380V to 12V DC, 500W DESD hardware prototype has been designed, fabricated, and tested. Experimental results verify the validity of the proposed bi-directional converter, which has 97.3% peak efficiency and maintains greater than 92% efficiency over a load range between 100W and 600W.
international symposium on power electronics for distributed generation systems | 2015
Fei Xue; Ruiyang Yu; Wensong Yu; Alex Q. Huang
This paper presents a distributed energy storage device (DESD) based on a novel isolated bidirectional DC-DC converter with 650V GaN transistors. The device integrates a low-voltage (13.2V) Li-ion battery pack, an embedded bidirectional DC-DC converter and wireless communication system. The three parts are packaged together, thus it can be directly connected to high-voltage (380V) DC grid, enabling a modular approach for battery energy storage systems. Two 650V enhancement mode GaN transistors are used at the high voltage side. Compared with Si device, three improvements can be achieved in the application: expanding the operation range to light load, reducing switching loss and EMI, increasing the total efficiency of charging and discharging operation. The power stage design as well as a loss analysis of GaN is based on a steady state analysis and PSpice simulation. A 400V to 12V DC, 1kW converter for 1kWh DESD prototype is designed, fabricated, and tested. Experimental results verify the validity of the proposed DESD and the performance improved by using GaN transistors.
european conference on cognitive ergonomics | 2015
Sarah Hambridge; Alex Q. Huang; Ruiyang Yu
The Solid State Transformer (SST) is a revolutionary technology being developed by the authors. It has a tremendous number of features, which include power management, fault management and energy management. Its autonomous and distributed power management capability enables large-scale integration of distributed energy resources (DER) into the power grid. Specifically, it supports AC or DC connected Energy Cells: a combination of DERs, energy storage devices and loads. The SST can achieve real-time power flow regulation via the Energy Cell, therefore forming the foundation of its capability to become a real-time Energy Router. This paper introduces an economic based energy routing strategy that utilizes energy storage to reduce consumption of grid power. Predictive photovoltaic and load forecasting are used to optimize charging and discharging of energy storage. This rule-based algorithm is implemented and demonstrated in a SST enabled 380 V DC Energy Cell.
applied power electronics conference | 2016
Fei Xue; Ruiyang Yu; Alex Q. Huang
High conversion efficiency is always desired in energy storage device (ESD). In this work a high efficiency GaN and Si device mixed isolated bidirectional dc-dc converter is proposed in the distributed ESD application. To optimize the efficiency of the bidirectional half-bridge push-pull active clamp converter over a wide input/output voltage and load range, it is necessary to accurately predict the dissipated power for each power component so as to identify and properly design the heavily loaded components. This paper describes a universal method to predict the power losses of the converter. Loss models are provided to calculate total component losses using the current and voltage information derived from the steady state inductor current calculator. Details of loss breakdown are given. With the presented converter prototype, a top efficiency of 98.3% and an output power of 1 kW in a wide input/output voltage range is achieved. The loss analysis provides valuable information for designing an efficiency optimized converters in the application.
ieee international conference on dc microgrids | 2015
Fei Xue; Ruiyang Yu; Wensong Yu; Alex Q. Huang
This paper presents a novel GaN transistor based bidirectional isolated DC-DC converter for stationary energy storage device (SESD) for 400V DC microgrid. The improvements achieved in the application includes: first, benefitting from the internal ultra-fast free-wheeling diode, the converters operation range can be expended to light load conditions (switches operate in hard switching). The light load efficiency can be greatly increased. Second, because of its low switching loss and on state resistance, the heavy load efficiency is increased. Third, the snubber inductor which is indispensable in Si device based converter can now be omitted in the GaN version. The power stage design as well as a loss analysis of GaN is based on a steady state analysis and PSpice simulation. Experimental results are presented for a 500 W bidirectional dc-dc converter prototype.
ieee international conference on dc microgrids | 2015
Fei Xue; Yuling Zhao; Ruiyang Yu; Wensong Yu; Alex Q. Huang
This paper focuses on the design and control of a stationary energy storage system based on multiple modular high voltage battery modules. The system achieves bi-directional power flow directly from 400V dc grid to the 12V battery modules via a bi-directional dc-dc converter with high conversion ratio as an interface. One merit of such a system is its extensibility and scalability for higher power rating for future use by dispatching more battery modules together. A 2kWh energy storage system prototype which is made up by one grid-connected solid state transformer (SST) emulator and two bi-directional dc-dc converters are designed, fabricated and tested. Based on the modified droop control, a double-loop digital control system for the SST emulator and a single-loop digital control system for the dc-dc converter are implemented respectively. At last, experimental results are presented to verify the proposed distributed control strategy.
european conference on cognitive ergonomics | 2014
Mengqi Wang; Qingyun Huang; Alex Q. Huang; Wensong Yu; Ruiyang Yu
In this paper, three existing distributed PV system configurations are reviewed and compared in depth. A novel ultra-high-frequency-AC (UHFAC) PV system for residential application is proposed. Compared with traditional DC parallel PV systems, this new approach eliminates the high voltage DC bus by replacing it with UHFAC bus, which avoids the DC arcing fault and enables ultra-fast short circuit protection as well. Resonance is utilized in this system to help UHFAC power transfer and realize soft-switching. Cable modeling is conducted to extract AC parameters, which helps validate the UHFAC power transmission (i.e., 100 kHz) in 30 to 40-feet-distance. Cable parameters also participate in the resonant intervals which demonstrates full utilization of system components. Simulation and experimental results are provided to verify the proposed approach.
european conference on cognitive ergonomics | 2017
Fei Xue; Ruiyang Yu; Alex Q. Huang
A family of bidirectional fractional DC-DC converter for high voltage, high power battery energy storage system is proposed in this paper. The proposed converter has the benefits of low cost, high efficiency since it only processes part of the total converted power. One extra low voltage battery pack is needed; however, it can be from a different voltage rail or seamlessly integrated with the high voltage battery pack. System efficiency and battery capacity calculation methodologies are given in details. A proof-of-concept fractional converter based on GaN transistor was fabricated. Experimental results of a 1.2kW prototype are presented to validate the analysis. With the proposed converter, a peak equivalent efficiency of 99.63% in a wide input/output voltage range are achieved. It is shown that the fractional converter can greatly reduce the cost of energy storage system while achieve high efficiency and high power-density in potential applications.
applied power electronics conference | 2017
Qingyun Huang; Ruiyang Yu; Alex Q. Huang; Wensong Yu
This paper presents an adaptive Zero-Voltage-Switching control (ZVS) method and a hybrid current control strategy for the GaN-based MHz Totem-pole PFC rectifier. This novel ZVS control achieves the minimum ZVS time margin and maximum switching frequency clamping by adaptively controlling the synchronous rectifier (SR) turn off current. This adaptive SR turn off current control is a unified control strategy based on a proposed unified analytical converter model. The analytical model and the control strategy are applicable for full-range of input voltage and full-range of load for ZVS Totem-pole PFC. In addition, a dual-loop current control strategy is also proposed in this paper. This dual-loop current controller uses the outer average current control loop to directly regulates the inductor average current. The inner current control loop combines the peak current controller and the time based SR turn off current controller. The proposed SR turn off current control for ZVS is adaptively controlled by this time based controller. To verify the proposed ZVS control method and the hybrid current controller, a 1.5kW GaN-based MHz Totem-pole PFC prototype is demonstrated with full-range ZVS, 99% peak efficiency and high quality AC current.