A novel zero-voltage and zero-current switching PWM DC-DC converterwith reduced conduction losses

A novel zero-voltage and zero-current switching PWM DC-DC converter with low conduction losses is presented in this paper. A new interleaved two-switch forward soft-switching converter topology is developed to minimize circulating current with no additional auxiliary circuits. This converter has many advantages such as less components, better efficiency, high power density and cost efficiency for high power applications. The principle of operation is illustrated together with steady-state analysis. Moreover, the effectiveness of the proposed converter topology is verified by implementing a 500 W-100 kHz breadboard using IGBTs     

基于低共熔溶剂法超声辅助蒸馏提取胡椒叶精油的工艺优化及其GC-MS分析

以胡椒叶为提取原料,探究低共熔溶剂对胡椒叶精油提取效果的影响。在单因素实验结果的基础上,以液料比、超声功率与蒸馏时间为影响因素,以精油得率为响应值,应用Box-Behnken试验设计建立数学模型,进行响应面分析。结果表明,氯化胆碱-尿素组成的低共熔溶剂提取效果最好,响应面优化的最佳提取工艺条件为液料比为14:1 mL/g、超声功率300 W、蒸馏时间53 min。在此条件下,胡椒叶精油得率为1.380%±0.018%,优于水蒸气蒸馏法和超声辅助水蒸气蒸馏法,胡椒叶精油得率分别提升了14.33%、5.18%。通过GC-MS对胡椒叶精油进行分析,共鉴定出34种化合物,其主要成分为δ-榄香烯(19.75%)、α-荜澄茄油烯(9.17%)、石竹烯(8.97%)、α-古芸烯(6.12%)、β-榄香烯(5.13%)。结果表明,以氯化胆碱-尿素作为低共熔溶剂提取胡椒叶精油的方法是可行的。     

胡椒叶精油的提取工艺优化及其GC-MS分析

以不同类型的低共熔溶剂为提取剂,采用微波辅助蒸馏法从胡椒叶中提取精油。比较了不同类型的低共熔溶剂,并对影响精油得率的主要因素(液料比、微波功率、提取时间)进行了单因素试验和响应面的工艺优化。结果表明:氯化胆碱-尿素低共熔溶剂为最佳提取剂,当其液料比为16:1 mL/g,微波功率480 W,提取时间53 min时。在此条件下,精油最大得率为1.42%。对比试验发现:此方法对精油得率明显优于水蒸气蒸馏法和微波辅助蒸馏法,分别提高了17.48%、5.66%。通过用气相色谱-质谱(GC-MS)对精油的化学成分进行了鉴定,共34种物质,主要成分为异桉油烯醇(25.47%)、δ-榄香烯(17.52%)、石竹烯(8.27%)、α-荜澄茄油烯(7.07%)、α-古芸烯(5.59%)、(+)-喇叭烯(5.02%)。以氯化胆碱-尿素作为低共熔溶剂提取胡椒叶精油的方法是可行的。     

Analysis and design of a saturable reactor assisted soft-switchingfull-bridge DC-DC converter

Analysis and design considerations for a saturable reactor assisted soft-switching full-bridge DC-DC converter are presented. The converter has advantages such as low switching losses with no substantial increase in conduction losses, wide load range, and constant frequency operation. To show how to utilize the analysis results, a 350 W, 500 kHz converter is chosen as a design example. The results are verified experimentally on a prototype converter     

计及波浪能并网的弱区域配电网继电保护方案研究

考虑到波浪能发电接入配网给配电网带来弱环运行和继电保护问题,首先建立波浪能发电模型,在此基础上分析波浪能并网后配网故障后给其继电保护方案带来的一系列影响,接着分析含波浪能发电的配电网故障计算方式,然后提出基于分区纵差配合自适应过流保护的方案实现含波浪能并网的配电网的继电保护,并通过仿真验证该方案的有效性。     

Simulations of ultra-high sensitivity RI sensor in triple-core fiber with modified Vernier effect:Application in marine RI measurement

We proposed an ultra-high sensitivity triple-core fiber refractive index (RI) sensor with a modified Vernier effect for marine RI measurement and demonstrated it by numerical simulation. This sensor composes a pair of parallelized spatial mode Mach-Zehnder interferometers (MZIs), both of which are involved in sensing, but possess different interfering modes. By designing an MZI RI fiber optic sensor based on Vernier effect in air, it is demonstrated that in the low RI such as air environment, only the modes involved in sensing interference are affected by the environment to generate Vernier effect. In the high RI marine environment, both sensing interferometer and reference interferometer need to be affected by the ambient RI to generate Vernier effect. The simulation results indicate that the proposed novel sensing structure can amplify its sensitivity from −15 428 nm/RIU to −24 857 nm/RIU in the marine environment.     

Two-switch forward soft-switching PWM DC-DC power converter

A novel prototype is presented of a two-switch forward soft-switching PWM DC-DC power converter with reduced switching and conduction power losses, which can operate under two soft commutations of zero voltage and zero current of full bridge circuit topology