Coordinated Rotor-Side Control Strategy for Doubly-FedWind Turbine under Symmetrical and Asymmetrical Grid Faults

In order to solve the problems of rotor overvoltage,overcurrent and DC side voltage rise caused by grid voltage drops,a coordinated control strategy based on symmetrical and asymmetrical low voltage ride through of rotor side converter of the doubly-fed generator is proposed.When the power grid voltage drops symmetrically,the generator approximate equation under steady-state conditions is no longer applicable.Considering the dynamic process of stator current excitation,according to the change of stator flux and the depth of voltage drop,the system can dynamically provide reactive power support for parallel nodes and suppress the rise of DC side voltage and rotor over-current.When the grid voltage drops asymmetrically,the positive and negative sequence components are separated in the rotating coordinate system.The doubly fed generator model is established to suppress the rotor positive sequence current and negative sequence current respectively.At the same time,the output voltage limit of the converter is discussed,and the reference value is adjusted within the allowable output voltage range.In order to adapt to the occurrence of different types of power grid faults and complex operating conditions,a fast switching module of fault type detection and rotor control mode is designed to detect the type of power grid faults and voltage drop depth in real time and switch the rotor side control mode dynamically.Finally,the simulation model of the doubly fed wind turbine is constructed in Matlab/Simulink.The simulation results verify that the proposed control strategy can improve the low-voltage ride through performance of the system when dealing with the symmetrical and asymmetric voltage drop of the power grid and identify the power grid fault type and provide the correct control strategy.

Surrounding rock control of gob-side entry driving with narrow coal pillar and roadway side sealing technology in Yangliu Coal Mine

Gob-side entry driving can increase coal recovery ratio, and it is implied in many coal mines. Based on geological condition of 10416 working face tailentry in Yangliu Coal Mine, the surrounding rock deformation characteristics of gob-side entry driving with narrow coal pillar is analysed, reasonable size of coal pillar and reasonable roadway excavation time after mining are achieved. Surrounding rock control technology and effective roadway side sealing technology are proposed and are taken into field practice. The results showed that a safer and more efficient mining of working face can be achieved. In addition, results of this paper also have important theoretical significance and valuable reference for surrounding rock control technology of gob-side entry driving with narrow coal pillar under special geological condition.

Controlling floor heave of extraction opening by reinforcing sides and roof

The effect of reinforcing roof, sides and floor corners to control floor heave of extraction opening was analyzed, It was proved by engineering practice and numerical simulation that reinforcing any part of surrounding rock have certainly control effect for floor heave, in the basis of this, the new way that roof, sides and floor corners were rein-forced to control floor heave was put forward. Contrasting control result of reinforcing floor with this, it is determined that reinforcing is more suitable to control floor heave of extrac-tion opening than reinforcing floor when advancing abutment pressure is in some range.

Side force control on slender body by self-excited oscillation flag

Strong asymmetrical vortices appear on the leeward of slender body at high angles of attack, which has very unfavorable effect on the stability and control of the aircraft. A method is developed to control the side force of slender body at high angles of attack, and is verified in wind tunnel. A thin-film triangular self-excited oscillation flag is fixed at the tip of the slender body model whose semi-apex angle is 10°. Side force is approximately linearly proportional to roll-setting angle of self-excited oscillation flag at high angles of attack, and the slop of fitting straight line obtained by the least square method is -0.158. The linear relationship between side force and roU-setting angle provides convenience for developing side force control law of slender body at high angles of attack. Experimental data shows that the side force coefficients vary linearly with roll-setting angles when a specific plastic self-excited oscillation flag is used as the control flag. The range of side force coefficient and roll-setting angle are, respectively, -3.2 to 3.0 and -20° to 20°. The device is simple, effective, and is of great potential in engineering application.

Failure laws of narrow pillar and asymmetric control technique of gob-side entry driving in island coal face

In allusion to the problems of complex stress distribution in the surrounding rock and deformation failure laws, as well as the difficulty in roadway supporting of the gob-side entry driving in the island coal face, 2107 face in Chengjiao Colliery is researched as an engineering case. Through physical mechanical test of rock, theoretical and numerical simulation analyses of rock, the analysis model of the roadway overlying strata structure was established, and its parameters quantified. To reveal the deformation law of the surrounding rock, the stability of the overlying strata structure was studied before, during and after the roadway driving. According to the field conditions, the stress distribution in coal pillar was quantified, and the surrounding rock deformation feature studied with different widths of the pillars in gob-side entry driving. Finally, the pillar width of 4 m was considered as the most reasonable. The research results show that there is great difference in support conditions among roadway roof, entity coal side and narrow pillar side. Besides, the asymmetric control technique for support of the surrounding rock was proposed. The asymmetric control technique was proved to be reasonable by field monitoring, support by bolt-net, steel ladder and steel wire truss used in narrow pillar side.

Research on Direct Power Control of DC Side for the Active Power Filter

This paper addresses the principle and control topology of active pow er filter( APF). The control strategy of direct pow er control based on DC side is introduced,and the control output is implemented by using the principle of hysteresis control.The active pow er filter can effectively control the pow er system harmonics,improve the quality of electricity and purify pow er grid. The experimental results are provided to illustrate that the direct pow er control based on DC side has the advantages of simple structure,stable DC output voltage and fast dynamic response.

Distributed demand side management via smart appliances contributing to frequency control

Nowadays renewable energy has become a trend for energy production but its variable nature has made balancing of demand and supply of the power grid difficult. Dynamic demand management using smart appliances is proposed to serve as a way that part of the regulation burden of balancing demand and supply is shifted to the demand side. However, if all appliances respond to the same frequency deviation, they may start to synchronize, causing large power overshoots and instability of the power grid. Therefore, the idea of implementing randomness into the frequency control of the appliances is proposed and this is what we call a stochastic approach. Simulators are built from scratch to model both scenarios. The effect of synchronization is analyzed and the parameters that can affect the synchronization are investigated. It has been found that the larger the contribution from the smart appliances to the power grid, the easier and faster the synchronization takes place. The stochastic approach solves the problem of synchronization and averages out the large power overshoot. However, the overall performance of stochastic operations is unacceptable due to the randomness in the operation though the mean and variance are as expected. More advanced feedback policies and schemes may be designed to achieve a better performance.

Stability of coal pillar in gob-side entry driving under unstable overlying strata and its coupling support control technique

Considering the situation that it is difficult to control the stability of narrow coal pillar in gob-side entry driving under unstable overlying strata, the finite difference numerical simulation method was adopted to analyze the inner stress distribution and its evolution regularity, as well as the deformation characteristics of narrow coal pillar in gob-side entry driving, in the whole process from entry driving of last working face to the present working face mining. A new method of narrow coal pillar control based on the triune coupling support technique (TCST), which includes that high-strength prestressed thread steel bolt is used to strain the coal on the goaf side, and that short bolt to control the integrity of global displacement zone in coal pillar on the entry side, and that long grouting cable to fix anchor point to constrain the bed separation between global displacement zone and fixed zone, is thereby generated and applied to the field production. The result indicates that after entry excavating along the gob under unstable overlying strata, the supporting structure left on the gob side of narrow coal pillar is basically invalid to maintain the coal-pillar stability, and the large deformation of the pillar on the gob side is evident. Except for the significant dynamic pressure appearing in the coal mining of last working face and overlying strata stabilizing process, the stress variation inside the coal pillar in other stages are rather steady, however, the stress expansion is obvious and the coal pillar continues to deform. Once the gob-side entry driving is completed, a global displacement zone on the entry side appears in the shallow part of the pillar, whereas, a relatively steady fixed zone staying almost still in gob-side entry driving and present working face mining is found in the deep part of the pillar. The application of TCST can not only avoid the failure of pillar supporting structure, but exert the supporting capacity of the bolting structure left in the pillar of last sublevel entry, thus to jointly maintain the stability of coal pillar.

基于多绕组变压器取能的直串型柔性互联装置控制策略研究

柔性互联装置由于其控制的灵活性和功能的多样性,用于解决配电网新能源倒送、供区间负荷不均等问题。现有的柔性交流互联方案在工程应用中难以兼顾可靠性和经济性。为此,首先提出一种多绕组变压器取能的直串型柔性互联装置拓扑方案,并分析了该方案实现潮流调控的基本原理;然后分别建立了直串型柔性互联装置并联侧子模块及串联侧换流链的控制理论模型,并提出了相应的并联侧子模块直流电压独立控制与串联侧换流链有功功率控制策略;最后通过某地柔性交流互联示范工程中装置满载运行的实际结果,验证了所提控制策略的有效性。

A demand side controller of electrolytic aluminum industrial microgrids considering wind power fluctuations

Direct wind power purchase for large industrial users is a meaningful way to improve wind power consumption and decrease industrial production costs.Short-term wind power fluctuations may lead to large-scale wind power curtailment problems.To promote use of wind energy,a demand side control method is proposed based on output regulator theory for a grid-connected industrial microgrid with electrolytic aluminum loads to continuously track and respond to wind power fluctuations.The control model of the EALs and the dominant frequencies of the wind power fluctuation signals are analyzed and incorporated into the demand side control plant.The feedback control signals with active power deviations on the tie-line are used to design the demand side controller.Simulations are conducted for an actual industrial microgrid to validate the feasibility and effectiveness of the proposed method.The results demonstrate that the proposed controller based on output regulator theory is able to effectively track wind power fluctuations.

有氧运动改善化疗期间乳腺癌患者体质及生活质量研究:一项随机对照试验

背景蒽环类药物是乳腺癌基础化疗药物之一,但化疗常伴随着体质改变如体脂增加和心肺功能下降,胃肠道反应和骨髓抑制等毒副作用,影响患者的生活质量。目前关于运动改善以上毒副作用的研究结果不一致,有待进一步研究。临床上,应用运动处方改善乳腺癌患者以上化疗毒副作用的效果和安全性需要进一步探究。目的探究有氧运动改善蒽环类药物化疗期间乳腺癌患者体质和生活质量的效果及有氧运动的安全性。方法本研究是一项随机对照试验,纳入2022年3月—2023年1月在北京市朝阳区三环肿瘤医院接受蒽环类药物化疗方案的44例成年女性乳腺癌患者为研究对象,随机分为运动组(23例)与对照组(21例),对照组患者在化疗结束后提供个性化运动指导。运动组患者在化疗住院期间在康复师监督下进行锻炼,在家时通过患者自我监督和试验人员远程监督进行个性化运动干预。在化疗前后收集主要结局指标,包括体质和生活质量,记录胃肠道反应、骨髓抑制的发生次数、严重程度及运动相关不良事件。以化疗前数据为协变量,采用协方差分析比较两组体质情况和生活质量情况。结果本研究干预、随访过程中共流失4例,最终纳入40例患者(运动组21例,对照组19例)。运动干预期间未观察到严重不良事件。运动干预期间,患者平均依从性为81.8%;每次运动时长的平均依从性为91.9%;运动强度平均依从性为92.5%。化疗后,运动组体脂重、体脂百分比、内脏脂肪面积、腰围、腰臀比低于对照组,惯用手握力、相对峰值摄氧量(VO_(2)peak)高于对照组(P<0.05)。化疗后运动组患者功能性障碍发生率(7/20)低于对照组(12/16)(χ^(2)=5.707,P=0.017)。化疗后运动组生理状况、情感状况、附加得分低于对照组,功能状况得分高于对照组(P<0.05)。化疗后对照组生理状况分数(P<0.001)、运动组功能状况分数(P=0.017)高于化疗前。对照组和运动组患者分别共接受了84例次和94例次蒽环类药物化疗,对照组分别发生了84例次胃肠道反应和71次骨髓抑制,运动组分别发生了54例次胃肠道反应和45例次骨髓抑制,两组患者胃肠道反应和骨髓抑制发生情况比较,差异有统计学意义(P<0.05)。结论在蒽环类药物化疗期间进行有氧运动可以改善乳腺癌患者的体质和生活质量,且有监督的有氧运动是安全的。

小煤柱沿空掘进瓦斯综合防治技术研究

以某矿31018回风顺槽小煤柱沿空掘进为工程背景,对采空区侧煤体卸压范围考察,确定采空区侧煤体卸压范围,并在卸压范围进行残余瓦斯含量测试,划定无突出危险性范围;采用对小煤柱进行注浆加固和巷道全断面喷浆措施防止采空区瓦斯溢出;使用钻屑指标法对掘进工作面进行预测和验证。统计表明:31018回风顺槽小煤柱沿空掘巷过程中,预测指标K_(1max)=0.24,S_(max)=3.4,平均进尺5.8 m/d,回风流平均瓦斯浓度为0.15%,单日绝对瓦斯涌出量平均为1.04 m^(3)/min,实现了巷道安全掘进。

浙江省山区输电线路塔位边坡变形破坏主要类型与防治建议

山区输电线路铁塔基础施工改变了塔位附近原始微地形、覆盖植被等环境地质条件,岩土体内部原有应力状态发生了变化,在各种自然营力作用下,每年在浙江省山区会发生一定数量塔位边坡的变形与破坏。根据影响因素、变形破坏机理分析,结合现场勘查及实际情况,划分为坍塌、滑坡、流坍等边坡变形破坏类型,经研究总结得出其主要发育特征,并提出了防治建议。

建筑空调系统基于用能柔性参与电力市场研究综述

近年来,为解决能源问题并实现碳中和目标,全球范围内的可再生能源发电量迅速增长。然而,可再生能源发电的间歇性也对电网平衡提出了更大的挑战。建筑空调系统可通过柔性用能有效缓解智能电网平衡的压力。本文分析了建筑空调系统正在及有望参与的电力市场类型,以及参与不同类型市场对建筑空调柔性控制的要求,而后总结了空调系统实施柔性用能的控制策略及控制中遇到的问题和解决方法,最后分析了柔性用能容量的约束及提升方法,并对建筑节能与柔性用能进行了比较和思考,以期为空调系统通过柔性用能参与各类型电力市场的深入研究、探索提供参考。

厚煤层综放工作面小煤柱沿空掘巷围岩控制技术研究与应用

针对厚煤层综放工作面区段煤柱留设宽度大和煤炭回采率低的问题,以鲍店煤矿83上03胶带顺槽为研究对象,采用理论分析、数值模拟和现场实测的研究方法,确定了护巷小煤柱最佳宽度为5m,提出了“顶板锚索槽钢梁+锚杆+W钢带+金属网+塑料网”联合支护方案。现场试验结果表明:胶带顺槽采用联合支护方案沿空掘巷技术和留设5m宽护巷小煤柱时,巷道掘进和工作面回采期间巷道围岩变形均得到有效控制,确保了工作面安全高效生产。

Robust H-infinity integral sliding mode control for a class of uncertain switched nonlinear systems

This paper develops a new method to deal with the robust H-infinity control problem for a class of uncertain switched nonlinear systems by using integral sliding mode control.A robust H-infinity integral sliding surface is constructed such that the sliding mode is robust stable with a prescribed disturbance attenuation level γ for a class of switching signals with average dwell time.Furthermore,variable structure controllers are designed to maintain the state of switched system on the sliding surface from the initial time.A numerical example is given to illustrate the effectiveness of the proposed method.

特瑞普利单抗辅助FOLFOX治疗对进展期胃癌患者血管新生和PD-1/PD-L1信号通路的影响

目的探讨特瑞普利单抗联合FOLFOX方案治疗进展期胃癌的效果及其免疫调节机制。方法选取2021年6月至2023年6月驻马店市中心医院收治的97例进展期胃癌患者纳入研究,按随机数表法分为观察组49例和对照组48例,其中对照组采用FOLFOX方案治疗者,观察组采用FOLFOX方案+特瑞普利单抗治疗,21 d为一个疗程,持续治疗6个疗程。比较两组患者治疗6个疗程后的治疗效果,以及治疗前、治疗3个疗程和6个疗程后的程序性细胞死亡受体-1(PD-1)/程序性细胞死亡配体-1(PD-L1)信号通路(PD-1蛋白、PD-1 m RNA、PD-L1蛋白、PD-L1 m RNA)、血管新生指标[低氧诱导因子1α(HIF-1α)、血管内皮生长因子(VEGF)、促血管生成素-2(Ang-2)、环氧合酶-2(COX-2)],同时比较两组患者治疗期间的毒副反应以及随访6个月的生存率。结果治疗6个疗程后,观察组患者的疾病控制率为63.27%,明显高于对照组的41.67%,差异有统计学意义(P<0.05)。治疗3个疗程、6个疗程后,观察组患者的PD-1蛋白分别为5.83±1.12、5.77±1.26,明显低于对照组的6.84±1.25、7.11±1.36,PD-1m RNA分别为6.12±1.33、6.01±1.34,明显低于对照组的6.91±1.34、7.20±1.30,PD-L1蛋白分别为6.30±1.05、6.19±1.11,明显低于对照组的7.02±1.33、6.88±1.40,PD-1 mRNA分别为6.41±1.24、6.33±1.25,明显低于对照组的7.19±1.36、7.10±1.38,差异有统计学意义(P<0.05)。治疗3个疗程、6个疗程后,观察组患者的VEGF分别为(224.46±25.25)ng/mL、(150.10±14.14)ng/mL,明显低于对照组的(279.79±30.44)ng/mL、(191.65±16.63)ng/mL,HIF-1α分别为(135.51±16.67)μg/L、(100.10±12.28)μg/L,明显低于对照组的(175.53±18.48)μg/L、(153.53±14.88)μg/L,Ang-2分别为(68.98±7.36)ng/mL、(46.68±5.13)ng/mL,明显低于对照组的(75.51±7.95)ng/mL、(56.64±6.11)ng/mL,COX-2分别为(31.48±4.12)ng/mL、(20.24±3.38)ng/mL,明显低于对照组的(36.64±4.20)ng/mL、(25.74±3.59)ng/mL;差异均有统计学意义(P<0.05)。两组患者治疗6个疗程后的毒副反应发生率与随访期间生存率比较差异均无统计学意义(P>0.05)。结论特瑞普利单抗联合FOLFOX方案治疗进展期胃癌,可阻断PD-1/PD-L1信号通路,增强肿瘤控制效果,且具有较好的安全性。

A NEURAL NETWORK FOR WELD PENETRATION CONTROL IN GAS TUNGSTEN ARC WELDING

Realizing of weld penetration control in gas tungsten arc welding requires establishment of a model describing the relationship between the front-side geometrical parameters of weld pool and the back-side weld width with sufficient accuracy. A neural network model is developed to attain this aim. Welding experiments are conducted to obtain the training data set （including 973 groups of geometrical parameters of the weld pool and back-side weld width） and the verifying data set （108 groups）. Two data sets are used for training and verifying the neural network, respectively. The testing results show that the model has sufficient accuracy and can meet the requirements of weld penetration control.

Spatiotemporal evolution rule of rocks fracture surrounding gob-side roadway with model experiments

A series of plane-strain physical model experiments are carried out to study the spatiotemporal evolution rule of rocks fracture surrounding gob-side roadway, which is subjected to the pressure induced by the mining process. The digital photogrammetry technology and large deformation analysis method are applied to measure the deformation and fracture of surrounding rocks. The experimental results indicate that the deformation and fracture of coal pillars are the cause to the instability and failure of the surrounding rocks. The spatiotemporal evolution rule of the rock deformation and fracture surrounding gob-side roadway is obtained. The coal pillar and the roof near coal pillar should be strengthened in support design. The engineering application results also can provide a useful guide that the combined support with wire meshes, beam, anchor bolt and cable is an effective method.

SLIDING MODE CONTROL FOR ACTIVE AUTOMOBILE SUSPENSIONS

Nonlinear control methods are presented based on theory of sliding mode control (SMC) or variable structure control (VSC) for application to active automobile suspensions. Requirements of reducing manufacturing cost and energy consumption of the active suspension system may be satisfied by reasonable design of the sliding surface and hydraulic servo system. Emphasis is placed on the study of the discrete sliding mode control method (DSMC) applicable for a new sort of speed on off solenoid valves of anti dust capability and low price. Robustness and effectiveness of the feedback linearized controller in typical road conditions are demonstrated by numerical results for a quarter car suspension model.