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Despite having a high strength-to-weight ratio and being chemically inert, fiber-reinforced polymer (FRP) reinforcing bars are not currently used in reinforced concrete protective design du...

An inelastic single-degree-of-freedom (SDOF) dynamic analysis model is developed to predict the entire displacement time-history of concrete beams reinforced with hybrid mixtures of fiber reinforced polymer (FRP) and steel reinforcing bars subjected to blast loads. Hybrid FRP-steel reinforced concrete members exhibit strong self-centering tendencies which promote blast resilience through reductions in residual damage, repair cost, and facility downtime after a terrorist bomb attack or accidental explosion. FRP bars provide an internal restoring force that activates self-centering behavior after the inertial loads are removed, while the conventional steel reinforcement and concrete dissipate energy by their inelastic response. The SDOF model is equally applicable to all-steel, all-FRP, and hybrid FRP-steel reinforced concrete flexural members, incorporating all the relevant parameters of flexural response, nonlinearity, and self-centering that have been observed to play an important role in blast tests. These parameters include the type, size, spacing, arrangement, and material properties of longitudinal and transverse reinforcement, as well as concrete properties and section geometry. The effect of these parameters is described in terms of nonlinear resistance functions capturing the inbound and rebound flexural response, plastic hinge formulations to account for crack bridging provided by FRP bars, and a hysteretic model for the combined effects of self-centering behavior and stiffness degradation due to accumulated damage from progressively increasing repeated blast tests. A new response parameter, known as the Blast Self-Centering Index (BSI), is proposed to evaluate and assess the residual displacements of all-steel, all-FRP, and hybrid FRP-steel reinforced concrete beams predicted by SDOF analysis. The model has been verified extensively against data obtained from explosively driven shock tube blast experiments.

A new Switched Tank Converter (STC) with Partial Power Voltage Regulation (PPVR) is introduced for electric vehicle applications. It offers a flexibly adjustable conversion ratio for a wide-range battery voltage. The unregulated stage is modularized with resonant switched capacitor converters. All device voltage stresses are equal to the input voltage. The efficient unregulated stage processes the bulk of system power and the less efficient regulated stage processes a small amount of power. Thus, high overall efficiency can be achieved. A new index called Semiconductor Loss Index (SLI) is defined as a function of semiconductor die area to evaluate different power topologies. It is helpful to analyze the impact of each switch die area, different operated output power, switching frequency, and conversion ratio on the total device power loss. With the same total semiconductor die area, the proposed converter can achieve less than 1/3 device total power loss compared with boost converter. A 4-kW 1200V output converter prototype with 200V~400V input voltage range is developed, which combines a 6 times conversion ratio STC with a PPVR buck converter. The overall full-load efficiency of designed 4-kW converter can reach to 97.71%. Simulation, prototype and experiment results are presented to verify the validity of the proposed converter.

In this paper, an new converter that includes isolated composite resonant multilevel converter (ICRMC) that uses composite converter concept and partial power voltage regulator (PPVR) has been proposed for telecommunication application. The proposed converter can achieve high efficiency at nominal operating point since it takes minimum effort to regulate the output voltage at this point. A comparative study shows that with the proposed two operation modes of ICRMC, the proposed converter has the best capability to maintain lowest total semiconductor power stress among the existing state of the art solutions when the input voltage varies from 36V to 60V. Furthermore, zero current switching (ZCS) can be always achieved on the switching devices in ICRMC under different operating points. A 600W converter has been simulated to validate the theoretical analysis. The estimated peak efficiency can be as high as 97.65%. Fully debugged prototype and experimental results are provided in this paper.

This paper presents two novel single-phase resonant multilevel modular boost inverters based on resonant switched capacitor cells and a partial power processed voltage regulator. Compared with other multilevel boost inverters applied in PV systems, one remarkable advantage of the proposed topologies is that the bulky AC filtering inductor is replaced by a smaller-size one in the partial power processed buck converter. Constant duty cycle PWM method is attractive for the multilevel inverter controller design. GaN Enhancement Mode Power Transistors help both the modular resonant switched capacitor cells and the full-bridge unfolder be realized in a small size with high power density. The clamp capacitors in the resonant switched capacitor cells effectively alleviate the switch voltage spikes. These two inverter topologies are analyzed and simulated in PLECS. Simulation results verify the validity of boost inverter function. Stress analysis shows that the inverter has relatively small total normalized switch conduction power stress and total normalized switch stress ratio. Relative total semiconductor chip area comparison results reflect that the proposed topology achieves more efficient semiconductor utilization compared with typical non-resonant multilevel modular switched capacitor boost inverters. Test results indicate that the proposed topology can be used for single-phase non-isolated PV boost inverter applications with small ground leakage current, high voltage conversion ratio, small volume and potential high efficiency.

This paper presents a smart Composite Modular Power Delivery Architecture (COMPDA). One example for this architecture is applied in DC-DC 48V to 12V data center circuit shown here. COMPDA has many good features, such as voltage clamping for all devices, low total device stress under wide range ratio. It also has good modular characteristics. Each device has the same voltage and current stress. The principle operation is that all modular cells are connected in-series to share input high voltage and in-parallel to pump output high current, which can easily achieve ultra-high power density and high efficiency. Zero current switching (ZCS) can be applied in the proposed converter. A 4X unregulated DC-DC COMPDA with ZCS is studied for data center application. Finally, a GaN based prototype is built and tested to verify the theoretical analysis. The proposed converter can achieve the peak efficiency at 98.55% under ultra-high switching frequency 253 kHz. Furthermore, another GaN based high-density 6X boost COMPDA based prototype is also presented here. The peak efficiency can achieve 98.9% at 4kW power rating.

This paper presents an ultra-efficient composite modular power delivery architecture (COMPDA) that is able to be used for DC-DC, DC-AC, AC-DC, and AC-AC applications. The proposed architecture has very good module structure, the devices in each module have the same voltage and current stress. When it is used for high conversion ratio dc-dc applications, the device voltage stress is the same with the low voltage side, and the device current stress is the same with the low current side. Compared with the buck, flying capacitor multilevel or modular multilevel dc-dc converters, the proposed architecture has much lower total device power or current stress, which means a significant semiconductor chip area reduction. During the operation, the modules are connected in-series to sustain the high voltage and connected in-parallel to pump the high current. By properly design the resonant tank in the COMPDA, all the switching devices could achieve zero current switching or zero voltage switching. A partial power regulator could be integrated in the proposed architecture, where only a minimum amount of power needs to be processed in order to achieve the output voltage fine regulation. By properly control the operation of modules, the COMPDA can also be used as a high boost ratio DC-AC inverter or high step-down ratio AC-DC rectifier while keeping the soft-switching features, which are specially suitable for solar farm and data-center application. When apply the COMPDA to single-phase DC-AC or AC-DC applications, only a minimum amount dc-link capacitor is needed since the needs of energy storage is minimized, and there is no high voltage dc-link requirement anymore. In order to show the benefits of the COMPDA, one special unregulated case derived from the proposed architecture has been used for 48 V–8 V DC-DC data center application, which is also named switched-tank converter. Finally, a GaN based prototype is built and tested to verify the theoretical analysis. The proposed converter can achieve the peak efficiency at 98.55% under switching frequency 253 kHz and power density is ∼750W/inch3.

This paper discusses a GaN based motor drive topology with a high conversion ratio and sinusoidal output voltage. This inverter topology is based on the z-source inverter and provides many benefits over the traditional three-phase inverter or traditional inverter with a DC-DC boost converter input. The semi-quasi-z-source inverter allows the input voltage source and the load to share a ground so the problem of handling leakage current is eliminated. Thanks to the high conversion ratio with the semi-quasi-z-source topology, a lower input voltage can be used to generate a desired output. The proposed topology can also take advantage of many popular modulation strategies of traditional inverters. The output of this inverter is sinusoidal so it is perfect for motor drive applications. This paper also compares the voltage and current stress of the semi-quasi-z-source inverter against a traditional inverter with a DC-DC boost converter. Simulations for a 10 kW semi-quasi-z-source inverter are also discussed at the end of this paper.