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In this paper, the PWM plus phase-shift control with certain voltage balanced condition is applied to a hybrid dual bridge series resonant converter (HDBSRC). The control strategy is unified for the whole variation range of load, input/output voltage and with simple calculation. By using this voltage balanced strategy, the effective unity-gain operation condition can be obtained. A decoupled control can be derived then, in which the converter gain can be controlled by the PWM in the hybrid primary bridge and and load level is regulated by the phase-shift modulation. The equivalent unity-gain operation naturally extend the ZVS range and reduce the resonant current. A design example based on the analysis results is presented and then verified through experiment.

To enhance the efficiency of a semi dual-bridge resonant converter(SDBRC), a control strategy to minimize the root mean square(RMS) current and eliminate the backflow power is proposed. An optimal operating point is precisely selected to reduce the conduction loss due to backflow power and high rms current. The converter is enabled to work with the optimal operating point in the whole load range by adjusting the switch-controlled capacitor (SCC) based tunable resonant tank continuously. Soft-switching of all switches can be maintained along the control route as well. A lab prototype converter designed at 300 W is tested to validate the SCC-based topology and proposed modulation scheme. The experimental result has demonstrated that the proposed topology and modulation scheme can improve the converter efficiency over the whole load range, especially in the light load condition.

Digital-analog hybrid simulation combines digital simulation and physical simulation, and is an important simulation method for studying modern power systems. Aiming at the slow impedance matching speed and low accuracy of the damped impedance method in the current digital-analog hybrid simulation methods, a damped impedance type digital-analog hybrid simulation interface algorithm based on the R-L method. The physical side impedance is tracked by the R-L method and matched to the digital side impedance, which solves the problem of slow speed and low accuracy of the existing matching tracking method. Research the proposed damped impedance interface based on the R-L method through simulation, and compare it with the ideal transformer method in terms of algorithm stability and simulation accuracy, and the correctness of the damping impedance interface algorithm based on the R-L method in different scenarios is verified. It provides a new method for impedance matching tracking.

The fault detection is unreliable when small fault angle faults and high-resistance ground faults occur in ungrounded-system microgrid. In the traditional microgrid grid, large diversity in fault components results in the current quick-action protection refusal in different operation modes, i.e. island operation and grid-connected one. In his paper, the largest energy sum of the zero-mode current transient components of each line is utilized to form a characteristic frequency band. Then a fusion criterion of characteristic frequency band and cross-overlap differential transformation (SOD) is proposed to realize AC microgrid fault detection. PSCAD/EMTDC simulation shows that the characteristic frequency band can effectively filter out signal interference and highlight fault features, also, the SOD can detect the initial traveling wave quickly that only extracts the first few sampling points of the fault current and voltage signals, which can avoid the defect of the initial traveling wave extraction perishability.

Harmonics propagation in power systems may result in increased power losses and equipment damages. In this paper, an elliptic formula is derived to analyze the harmonic spatial propagation not only at the substations, but also along the power lines or cables and to give a system-wide overview of harmonic levels. It is observed that harmonic distortion along power lines can be higher than that at the busbars. All cases are modelled in detail by analytical geometry and analyzed using MATLAB. In this regard, a method to identify the weak positions in terms of maximum harmonic levels in a power system is presented, and its corresponding harmonic orders are determined. The accuracy of the model is tested using time-domain simulations in PSCAD/EMTDC.

The purpose of this study was to investigate the possibility for utilization of coal fly ash treated with initiator C as a low cost adsorbent material for the advanced treatment of landfill leachate. Batch experiments were conducted to determine the effect of fly ash dosage and initial pH on adsorption of COD. Experimental adsorption equilibriums were measured and the adsorption kinetic measurements were carried out. For all the reaction temperature, the isothermal data could be described by the Freundlich adsorption model. The Kinetic measurements confirmed that the adsorption of COD from landfill leachate could be described by a model involving pseudo-second-order reactions. The change of entropy (ΔS°) and enthalpy (ΔH°) of the process were estimated as -112.7J/mol and -43.11kJ/mol, respectively. The negative value of the change in Gibbs standard free energy (ΔG°) confirmed the feasibility of the process and the spontaneous adsorption of COD on the adsorbent. The negative value of activation energy (Ea) showed that the adsorption rate decreased when the temperature increased.

Lignocellulosic biomass is the world's most abundant renewable resource. Conversion of lignocellulosic biomass to bioenergy, such as the second generation bioethanol or biobutanol is viable because of its broad availability. Switch grass was developed as a pioneer energy crop in USA with great industrial prospect. It contains about 60% sugars and 18% lignin. An intergrated pretreatment process was developed to fractionate cellulose, hemicellulose and lignin from switch grass, consisting of dilute acid pretreatment (DAP) coupled with organic solvent (organosolv) pretreatment of water/ethanol (OWEP). In the coupled dilute acid -organosolv process, hemicellulose sugars were recovered in the first residual liquid while a varied amount of cellulose was retained in the residual solid and the lignin fraction was obtained by simply adjusting the pH from the second liquid. The optimal two-stage process consisted of the first stage DAP at 428K for 7min with 0.8% sulfuric acid, resulting in 79.82% glucose recovery yield and 98.74% xylose removal and the second stage OWEP at 468K for 20min in 45%(v/v) ethanol with 0.4% NaOH, resulting in 62% total glucose yield 99% xylose and 80% lignin removal. After enzymatic hydrolysis, the glucose yield was up to 92.6%, compared with 16% yield from untreated switch grass. The intergrated process has great promising.

MIMO (Multiple-Input Multiple-Output) wireless communication system has a better performance on achieving higher channel capacity and transmission reliability than traditional single-antenna system. It will definitely become one of the mainstream technologies for next generation wireless communications. However, since the multi-user interferences inevitably exist in MIMO systems, the quality of system communication will be weakened to some extent. Accordingly, how to minimize these disturbances and gain a higher quality of communication has become a major difficulty in research. As a matter of fact, precoding techniques can effectively reduce the multi-user interference and greatly simplify the complexity of receiver, which is one of the current research focuses. By making comparison among the current mainstream precoding algorithm of singular value decomposition (SVD), geometric mean decomposition (GMD) and uniform channel decomposition (UCD) under the MIMO system, this paper gives analysis of the performance differences of these three algorithms. Furthermore, the respective applications are also specified according to the distinct requirement of channel capacity and BER (bit error rate).

Two sufficient conditions for robust stability of discrete-time uncertain singular systems with polytope type uncertainties are proposed. The conditions are expressed in terms of a set of linear matrix inequalities (LMIs) involving only the vertices of the polytope domain. It enables us to determine robust stability of discrete-time uncertain singular systems easily by solving some LMIs. The new approaches can yield much sharper and less conservative results than the simultaneous stability approaches. Numerical examples are included to illustrate the the efficiency of the proposed approaches.

Perceived privacy is an important variable to influence customerpsilas trust and loyalty in e-commerce. It is crucial to fully understand consumerspsila perceived privacy in online shopping for understanding consumerspsila online behavior and encouraging them and potential consumers to adopt e-commerce. Through literature analysis, this paper explores consumer perceived privacy in online shopping and consumer behavior.