考虑负载均衡度的供电网负荷自动均衡调度系统

供电网中接入可再生能源的增加,提高了供电网负荷。为此,研究在考虑负载均衡度的基础上,设计一种供电网负荷自动均衡调度系统。在远程调度主站中分别配置后台中心网络和前置采集网,通过设计环网的通信网络结构实现通信功能,然后使用数据处理芯片处理供电网负荷调度数据。在设计负荷均衡调度模块后,结合SVR和小波分解设计供电网负荷预测算法。性能测试结果表明:在应用该系统后,供电和总负荷值之间的方差和均值较低,热功率平衡误差和风功率平衡误差较低,该系统的负荷均衡调度能力较强。

宣和猪FGF14基因多态性及其对生长性状的影响

为了探讨宣和猪FGF14基因外显子4的多态性及其对猪群生长性状的影响,通过PCR产物直接测序对366头宣和猪FGF14基因外显子4区域的SNP位点进行检测,结合宣和猪的生长性状记录,分析了单个位点基因型及两个位点单倍型组合对7个生长性状的影响。结果表明:在宣和猪外显子4上检测到T493A和A589G这两个紧密连锁的位点,以等位基因(T和A)以及纯合子(TT和AA)、TA单倍型和TA/TA单倍型组合的频率最高;两个SNP位点的遗传多样性较为丰富(0.3338≤H≤0.3750)。此外,T493A位点的AA基因型、A589G位点的GG基因型及AG/AG单倍型组合对6月龄体重、70日龄~4月龄日增重表现出显著提高作用(P<0.01或P<0.05),T493A位点的AA基因型、A589G位点的GG基因型及TG/TG单倍型组合具有提高6月龄背膘厚的效应(P<0.01或P<0.05)。研究结果进一步证实了宣和猪FGF14基因与6月龄体重、70日龄~4月龄日增重和6月龄背膘厚存在显著关联,T493A位点的AA基因型和A589G位点的GG基因型具有协同提高宣和猪生长性能的效应。

A new three-phase 5-level current-source inverter

The new three-phase 5-level current-source inverter (CSI) proposed in this paper was developed by connecting three separate single-phase 5-level CSIs in series, and its operational principle was analyzed. There are two major problems existing in current-source multilevel inverters, one is the complex PWM control method (2-logic to 3-logic conversion), and the other is the problem of current-unbalance between different levels. A simple current-balance control method via DC current feedback is applied in each single-phase 5-level CSI cell to implement the current-balance control between different levels. And to reduce the output current harmonics, POD PWM control technique was used. Simulation and experimental results showed that this new three-phase 5-level CSI topology operates correctly.

A 6-switch single-phase 5-level current-source inverter

The new 6-switch single-phase 5-level current-source inverter proposed in this paper was developed by properly simplifying the traditional 8-switch single-phase 5-level current-source inverter, and its operational principle was analyzed. Just like the problem of voltage-unbalance between different levels existing in voltage-source multilevel inverters, a similar problem of current-unbalance between different levels whether for the 8-switch single-phase 5-level current-source inverter, or for the new 6-switch 5-level current-source inverter also exists. A simple current-balance control method via DC current feedback is presented here to implement the current-balance control between different levels. And to reduce the output current harmonics, PWM control technique was used. Simulation and experimental results showed that this new 6-switch topology operates correctly and that the balance-inductor can almost equally distribute the total DC current.

基于CiteSpace竹子功能性状研究的可视化分析

植物功能性状体现植物与环境的密切关系,能够对不同环境作出相应的影响或响应。以中国知网作为数据来源,利用CiteSpace对竹子功能性状的研究进展、热点和趋势以及主要力量进行可视化分析。结果显示,研究力量以中国林业科学研究院、国际竹藤中心和南方各大林业高校为主,团队内部交流较为密切,但团队之间合作较少,跨地域、机构合作有待加强。关键词中观赏竹、生物量、毛竹林、竹纤维、土壤养分、干旱胁迫等中心性较高,应该重点关注;研究热点主要集中于光合作用、根际土壤养分以及抗逆性。竹子功能性状领域的研究方法已经趋于完善,随着全球气候变化日益严峻,通过竹子功能性状反应所处气候的变化以及群落生态系统功能可能是未来该领域的热点。

鲁中采煤沉陷区不同竹种根系功能性状及与土壤理化特性的相关性

为揭示不同竹种对采煤沉陷区土壤环境的适应能力,研究了山东省肥城市石横镇采煤沉陷区百竹园4个竹种的根系功能性状及其与土壤理化特性的关系。结果表明:(1)土壤含水率和速效钾含量均与根长密度、根表面密度存在显著正相关,与根组织密度呈显著负相关(P<0.05);pH值、有机质含量与比根长、比表面积存在显著正相关,与根组织密度、平均根直径呈显著负相关(P<0.05)。(2)淡竹竹根系总根长密度(737.784 m·m^(-3))、根表面积密度(1.121 m^(2)·m^(-3))均为最大,表明淡竹吸收养分与水分的能力最强;金镶玉竹根系的比根长(5.213 m·g^(-1))与比表面积(66.214 cm^(2)·g^(-1))最大,表明其资源获取速率最强;其中淡竹通过高根组织密度和低比根长获取资源的策略适应土壤环境。(3)根系生物量与根长密度、根表面密度呈显著正相关(P<0.05),淡竹根系总生物量显著大于其他竹种,可见淡竹通过增加根系生物量和密集鞭根网络系统可抑制采煤沉陷区土壤侵蚀。

鲁西8种观赏竹细根功能性状与根际土壤养分的关系

为揭示北方城市观赏竹细根功能性状与根际土壤的互作机制,对不同竹种地下生态适应策略进行研究。以山东省聊城市百竹园8种观赏竹为研究对象,从土壤表层开始每10 cm分层获取根系和根际土壤样品,测定土壤理化性质和细根形态参数。结果表明:(1)不同竹种根际土壤养分含量存在较大差异,且随土壤深度的增加而递减,0~10 cm土层,斑竹、淡竹土壤有机质、全氮、有效磷、速效钾含量较高,金镶玉竹、蓉城竹、四季竹土壤养分较低。(2)不同竹种细根形态参数之间相关性显著,具有明显的垂直分布规律,细根生物量与细根总根长、表面积、体积、根长密度为极显著正相关,根组织密度与比根长、比根面积、根长密度为极显著负相关,斑竹、淡竹细根生物量和根组织密度较高,蓉城竹和四季竹有较高的比根长、比根面积。(3)细根总根长、表面积、体积、根长密度、细根生物量与土壤有机质和全氮呈显著正相关,土壤速效钾对细根形态的变异贡献率最高(34.2%)。斑竹、淡竹有良好的环境适应性,可以有效应用于北方城市绿化,合理增加表层土壤的肥力有利于促进细根的生长。

不同配方对京薯6号组培苗黄化及生长发育的影响

以大量元素、有机元素、铁盐、糖类、激素6-BA为因素,采用L16(45)五因素四水平的正交试验设计,观测不同组合基质配方对京薯6号组培苗的黄化率、成苗率和生长发育的影响。结果表明,基质配方组合为大量元素4 mL+有机元素2.0 mL+铁盐1.0 mL+糖类8 g/L+6-BA 0.1 mg/L,京薯6号黄化率最低(11.79%)、成苗率较高(95.00%),综合评价最优;综合评价最差的组合为大量元素1 mL+有机元素2 mL+铁盐2 mL+糖类6 g/L+6-BA 1.0 mg/L,京薯6号黄化率为70.94%。由极差和方差分析结果可知,激素6-BA对京薯6号黄化的影响显著高于其他因素。在一定的激素6-BA浓度范围内,理论最优和最差基本组合下黄化率均呈"S"型曲线变化,两者曲线有相交点,最优基本组合下的黄化率比最差基本组合下的黄化率要高。

极寒条件下脱硫装置防腐施工质量控制技术

介绍了内蒙古霍煤鸿骏铝电烟气污染物趋零排放示范工程脱硫装置在极寒气候条件下乙烯基树脂衬里施工质量控制方法。通过对施工环境条件控制方法的阐述、使用效果评价,证明该技术成熟、有效,能在极寒条件下保证乙烯基树脂衬里施工质量,为极寒气候条件下乙烯基树脂衬里施工质量控制难题提供了一种解决途径。

A novel PWM scheme to eliminate the diode freewheeling in the inactive phase in BLDC motor

The brushless DC motor(BLDCM)with trapezoidal electromotive force(back-EMF)waveform is used widely.In principle,when the motor runs in the 120°conduction mode,two of the three phases are active while the other phase is inactive at all times.However,a ripple current occurs in the inactive phase due to the diode freewheeling during the non-commutation period in the traditional pulse width modulation(PWM)methods,which aggravates the torque ripples.A new PWM method is proposed in this paper to eliminate the diode freewheeling during the non-commutation period in the inactive phase.As a result,the torque ripple is suppressed using the proposed method.The simulation and experimental results are demonstrated to verify the validity of the proposed PWM method.

A zero-voltage zero-current soft switching DC/DC converter

A novel three-level zero-voltage zero-current switching(ZVZCS)DC/DC converter is proposed in this paper.A tapped-inductor is used to replace the normal out-put filter inductor,so that the circulating current in the zero-state can be reset to zero.The reset voltage and the re-set time can be set conveniently just by simply changing the winding ratio of the tapped inductor.The converter achieves a zero-current tuning off for inner switching,and a zero-voltage tuning on for outer switching.No circulating current exists in the zero state,so that the loss in the on-state is reduced,and the efficiency can be improved.The experimental results verify that the ZVZCS has low voltage stress,zero-voltage and zero-current switching.