Two-stage Conversion System Research Articles

The influence of temperature on geothermal power plant performance based on geology in Huangshadong geothermal field, China

The geological structure is rather complicated in Guangdong province, in China. The 10 deep fault belts are mainly oriented in North-East. The North-East fault belts are good channels for deep thermal energy upwelling, which can form a geothermal water reservoir zone. The heating of atmospheric precipitation and surface water by deep rocks is the primary formation mechanism for the hydrothermal resources in the Huangshadong geothermal field. The results show that the two-stage conversion system of flash-binary is more reasonable when the geofluid temperature is higher than 130?C. With every 10?C increment of geofluid temperature for flash-binary system, the power output and exergy efficiency in-crease by 21.6-38.7% and 6.0-13.1%, respectively. The power output and exergy efficiency will decrease by about 20-40% when cooling temperature arising from 15?C to 25?C. The research will provide the basic data for the demonstration of geothermal resource exploitation.

A Comprehensive Review on Common-Mode Voltage of Three-Phase Quasi-Z Source Inverters for Photovoltaic Applications

Inverters with Quasi-Z-Source Networks (QZSN) provide DC-DC boosting and DC-AC conversion in a single stage. It offers reduced cost, complexity, and volume compared with the classical two-stage conversion system, which is composed of a boost converter followed by a Voltage-Source-Inverter (VSI). Further, QZSI provides superior conversion characteristics for single-stage grid-connected photovoltaic transformerless systems. However, the absence of galvanic isolation in these systems makes it possible to allow leakage current through these systems’ parasitic capacitances due to the high-frequency Common-Mode Voltage (CMV) generated by the Pulse Width Modulation (PWM) nature of the inverter output voltages. As a result of this current, critical safety issues may arise with PV systems. Many PWM techniques have been presented in recent years for QZSIs. This paper is intended to provide a comprehensive analysis and review study of the characteristics of most of these PWM techniques in terms of CMV and leakage currents. In this study, closed-form equations have been derived to determine the effective CMV and leakage current analyses for all modulation techniques. Analytical and simulation approaches are used to identify schemes with the lowest CMV and current leakage effects. Moreover, the experimental setup is presented by applying the Simple-Boost Modified Space Vector Modulation (SB-MSVM) technique.

Efficient production of isoquercitin, icariin and icariside II by a novel thermostable α-l-rhamnosidase PodoRha from Paenibacillus odorifer with high α-1, 6-/α-1, 2- glycoside specificity

Minor flavonoids, such as isoquercitin, icariin and icariside II, have desired bioactivity and bioavailability. To enhance the production efficiency on converting rutin and epimedin C into minor flavonoids, a novel GH family 78 α-l-rhamnosidase PodoRha from the Paenibacillus odorifer was cloned and heterologous over-expressed in E. coli BL21(DE3). PodoRha exhibited a high catalytic ability in cleaving outer α-1, 2-rhamnopyranosyl moieties of epimedin C and α-1, 6- rhamnopyranosyl of rutin. It displayed the highest activity at 45 °C and pH 6.5, and has great thermostability at 40 °C. Under the optimal transformation condition (40 °C, pH 6.5, 1 h incubation), 10 g/L of Rutin was 99.86% transformed into 6.95 g/L of isoquercitin by PodoRha with a crude productivity of 6.95 g·L-1·h-1; 1.964 g/L icariin was detected after the epimedin C of the total Epimedium flavonoids (10 g/L) were 99.98% converted by PodoRha. Moreover, by using a two-stage conversion system with a crude icariside II productivity of 2.081 g·L-1·h-1, 5 g/L epimedin C was 99.85% converted into 3.122 g/L of icariside II with 1 h incubation under pH 6.5 at 40 °C after addition of 5.5 U/mL PodoRha; then with 30 min incubation under pH 6.5 at 90 °C after addition of 0.8 U/mL IagBgl1.

A New Family of Step-Up Hybrid Switched-Capacitor Integrated Multilevel Inverter Topologies With Dual Input Voltage Sources

In the low voltage based renewable systems like PV and Fuel cell applications, the step-up of the output voltage to drive the loads is essential. For this, the integration of switched-capacitor (SC) units with the dc-ac converters will have the potential advantages like improved efficiency, optimal switching devices, small size of passive elements (L and C) as compared with traditional two-stage conversion system (dc/dc converter and dc/ac converter). This paper focuses on a new family of step-up multilevel inverter topologies with switched capacitor integration with dual input voltage sources. With the flexibility of 2 dc sources and switching capacitor circuits, four different topologies have been suggested in this paper with features of high voltage gain, reduced component count, reduced voltage stress and self-voltage balancing of the capacitor while achieving a higher number of levels. A detailed analysis of proposed multilevel inverters has been analyzed with the symmetrical and asymmetrical mode of operations and the associated gain, the number of levels, and other performance indices are presented. An in-depth study of all the topologies has been accomplished in this paper with several comparative studies in terms of components count, voltage gain and cost. The effectiveness and practicability of the suggested topology with 13 level output voltage has been explained by the experimental results obtained from a scale down prototype.

An Isolated Quasi-Resonant Multiphase Single-Stage Topology for 48-V VRM Applications

In order to increase the efficiency of modern microprocessors power supplies used in data centers, the 48-V dc distribution bus is gaining growing attention. For such applications, voltage regulation modules (VRMs) are currently obtained using two-stage conversion systems with an intermediate 12-V dc bus. This paper presents an innovative single-stage approach for the 48-V VRM based on a quasi-resonant constant on-time (COT) operation. The proposed topology inherently integrates the multiphase approach, providing fast phase shedding and flat high-efficiency curves even at light load conditions. This is a unique advantage, usually not available in the two-stage approach, that is very important in server architectures, where high efficiency is required even at light load conditions. The paper analyses the circuit topology, and proposes a control architecture for fast transient response, including the current sharing capabilities, and a solution for implementing the integrated magnetics. The digital controller has been implemented in 0.16- $\mu$ m lithography together with a digital pulse-width-modulation with a 195 ps resolution, and a 40 MS/s, 7-bit ADC. Experimental results show an efficiency of 93.1% for a 250 A, 1.8 V VRM, and of 93.2% for a 102 A, 1.2-V double data rate (DDR) power supply.

Coupled inductor‐based single‐stage high gain DC–AC buck–boost inverter

Two stage conversion systems (TSCSs) normally use either boost converter or high gain dc-dc converter along with dc-ac inverter in order to transfer power from low input voltage dc source to high voltage ac load. When these TSCSs operate at extremely low input voltages, the boost converter has to operate at extremely high duty ratios. This in turn results in more losses and reverse recovery problems. Usage of high gain dc-dc converter results in more number of components, increase in control complexity and decrease in reliability. Single-stage conversion systems (SSCSs) are formed by merging both dc-dc and dc-ac conversion processes. These SSCSs have advantages like low loss, more compactness and less reverse recovery problems. In this study, a high gain coupled inductor-based single-phase SSCS is presented. This SSCS topology has many desirable features such as high gain, less switching losses, free from leakage inductance adverse effects and compact. Principle of operation, steady-state analysis and design of the proposed topology are described in detail. MATLAB simulation results of the proposed topology and experimental results using DSP28335-based experimental setup are presented to validate the proposed scheme.

Cryogenic converter for superconducting coil control

A two-stage conversion system is described for regulating the DC current in a superconducting coil, for example, the field winding of a superconducting synchronous machine. An ambient temperature converter provides a low, controlled current to a cryogenic converter, co-located with the superconductor, which steps up the current by over a hundred times to supply the superconducting coil. An array of parallel-connected metal oxide field effect transistors (MOSFETs) minimise losses in the cryogenic converter and a low-frequency, self-oscillating control technique is used for the DC link which minimises the capacitor requirements and ensures orderly switching conditions. Closed-loop control of the superconductor current is achieved through the ambient temperature converter, with current sensing power MOSFETs used at low temperature for current measurement. Practical results including measurements made on a superconducting machine are used to illustrate the system performance.

순간전압강하 보상을 위한 저가의 승압형 단상 인버터 시스템의 설계 및 구현

In this paper, a 300[W] class boost type single-phase inverter system which can compensate voltage sag on source side is designed and implemented. This system is a two-stage conversion system composed of a boost converter and a PWM inverter. If the voltage sag has appeared at the point of common coupling, the boost converter would be operated to compensate it. The boost converter and the inverter were constructed on single smart power module(SPM) to implement low cost system. The system is designed for that the THD of output voltage is below 5[%]. Finally, the validity of the design for the inverter system is verified by both simulations and experiments.

Modelling and simulation of wind turbine driven axial type permanent magnet generator with Z-source inverter

AbstractThis paper presents the modelling of direct driven permanent magnet generator (DDPMG) with Z-source inverter (ZSI) for wind turbine application. Direct drive wind energy conversion systems (WECS) based on permanent magnet generator (PMG) have some advantages such as no gearbox, high power density, high precision and ease of control. To show its effectiveness, a mathematical model of a PMG is developed and the PMG model variables are expressed in the dq-rotor reference frame. The output voltage and frequency from DDPMG is varied according to the speed of wind velocity. In order to obtain a desired voltage and frequency irrespective of wind velocity, the PMG is coupled with ZSI. The power conversion efficiency of ZSI is appreciably improved because of the traditional three-stage conversion system consisting of rectifier, boost chopper and inverter. The proposed two-stage conversion system comprises of rectifier and ZSI. The overall WECS of both proposed and conventional system are modelled in MATLAB...

Modelling and Simulation of Wind Turbine Driven Axial Type Permanent Magnet Generator with Z-source Inverter

This paper presents the modelling of direct driven permanent magnet generator (DDPMG) with Z-source inverter (ZSI) for wind turbine application. Direct drive wind energy conversion systems (WECS) based on permanent magnet generator (PMG) have some advantages such as no gearbox, high power density, high precision and ease of control. To show its effectiveness, a mathematical model of a PMG is developed and the PMG model variables are expressed in the dq-rotor reference frame. The output voltage and frequency from DDPMG is varied according to the speed of wind velocity. In order to obtain a desired voltage and frequency irrespective of wind velocity, the PMG is coupled with ZSI. The power conversion efficiency of ZSI is appreciably improved because of the traditional three-stage conversion system consisting of rectifier, boost chopper and inverter. The proposed two-stage conversion system comprises of rectifier and ZSI. The overall WECS of both proposed and conventional system are modelled in MATLAB/SIMULINK software. Their performance are analysed for various values of wind velocity and different loading conditions. Finally the input total harmonics distortion (THD), output THD and efficiency of the proposed system are compared with conventional WECS.