Flexible and precise current control of high temperature superconducting (HTS) loads based on flux pump is critical in many applications, which stabilizes both the generated magnetic field and operating current. For HTS loads with small inductances, such as small coils and single cables, it is difficult to stabilize the load current at a specific value without a current controller. Existing works have rarely studied methods to control such currents in HTS loads, prohibiting flux pumps from being used in high precision applications. This paper proposes a fuzzy proportional-integral-derivative (PID) control strategy to regulate the closed-loop load current of a small HTS coil and an HTS single cable, by controlling the DC bias field of a linear-motor type flux pump. The proposed control method enables stabilization of the load current at a preset level in HTS load with small inductance. The experimental results validate the effectiveness and robustness of the proposed control method, which enables the HTS flux pump to be potentially used for highly stable HTS magnets, or as a testbed current source for HTS cables, such as CORC ® , etc.

High temperature superconducting (HTS) flux pumps inject superconducting current directly into the HTS closed-loop, eliminating the need for thermally inefficient current leads. To achieve highly accurate closed-loop current, the current control based on flux pump is a topic requires in-depth study. This paper investigates a fuzzy logic control to achieve fast and precise current control with linear-motor type flux pump. The control strategy is originated from the discovered macroscopic magnetic coupling effect (MMCE) . With this method, we optimize and control the DC bias magnetic field to achieve fast and accurate closed-loop current control. In this experiment, we define five degrees of magnetic DC bias field, by which we stabilize the pumping current within 0.6 %o accuracy. The precise control of superconducting currents has been achieved, and the influence of the DC background magnetic field on magnetic coupling effects has been verified. This control algorithm is important for HTS applications requiring high current precision, such as magnetic resonance imaging (MRI), etc.

In comparison to traditional DC power supplies, linear-motor type flux pumps present a number of advantages, including a reduction in dimensions, a lower cost, and decrease in energy consumption. Therefore, it is useful to use a flux pump to power superconducting magnets in a non-contact manner. In order to facilitate the rapid excitation and current modulation of superconducting magnets updated flux pump was designed to deliver a higher DC voltage output. The distribution of magnetic flux density was analyzed using COMSOL Multiphysics, which helped in determining the optimal design parameters. We extended the coupling interval of the updated flux pump to 447 mm. The updated flux pump was tested at 77 K in liquid nitrogen, with a maximum output voltage of 118.24 mV, the updated flux pump can charge an insulated (INS) double pancake coil (DPC) with 75 turns per layer to a maximum current of 88.90 A in 9 s, exceeding the critical current (IC) for the DPC. This updated flux pump can power superconducting rotors in superconducting motors, magnetic resonance imaging (MRI) and other devices. This study verifies that extending the coupling length can effectively increase the output voltage of flux pumps, which has far-reaching effects on the application of linear-motor type flux pumps.

As a travelling-wave flux pump, the HTS dynamo generates a DC-biased AC travelling wave on the HTS stator tape placed in air-gap, which can output large DC current into an HTS coil without the need for current leads, thus effectively reducing heat leakage and operational cost comparing with conventional contact power supplies. In this paper, we introduce a method to enable symmetric bipolar output of the HTS dynamo, based on the “four-quadrant” control originates from the theory of macroscopic magnetic coupling. This method uses N-S arrangement of permanent magnets embedded on the magnetic disk and in addition to a DC bias coil. In this work, we demonstrate the use of the DC bias coil to freely adjust the DC output current of the HTS dynamo from -40.3 A to +40.5 A, without disturbing its rotating state. We also demonstrated that the DC output current can be symmetrically reversed by reversing the direction of the DC bias field, thus enabling the HTS dynamo with bipolar output. In addition, we developed a feedback control algorithm to control the output current with an accuracy of 0.15 A, by controlling the on and off states of the DC coil. This work enables the HTS dynamo as an accurate bipolar wireless power supply, which opens its routes for various applications of HTS magnets that require accurate current control, especially for high-demanding areas such as magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR).

High temperature superconductivity (HTS) flux pump can be used as the exciter to inject direct current into the superconducting excitation coil of a synchronous motor, without current lead and with low thermal efficiency, which will reduce the cryogenic volume and improve the efficiency of HTS synchronous motor. However, the flux pump has non-negligible thermal impact when it is running continuously for a long time within the cryogenic Dewar, which will cause a heavy heat burden to the cryogenic system. Therefore, based on the linear-motor type flux pump previously invented in our laboratory, this paper improved its magnetic circuit, so that it can introduce the travelling magnetic wave into the Dewar from outside. Firstly, we have used COMSOL Multiphysics to simulate and optimize the waveform of this flux pump. Secondly, we have manufactured the flux pump and magnetic conduction structure, and have tested its performance in liquid nitrogen at 77 K, a pumped DC current of 216 A was measured with a single 12 mm wide YBCO stator. These work have further optimized the linear-motor type flux pump, which provide a contactless static excitation device (CSED) for the 16.9 kW HTS synchronous motor built in our laboratory.

为了顺应新工科学习趋势、增强师生的互动性和培养学生的自主学习创新能力,四川大学电工电子学课程组试行了基于互联网+的雨课堂x"雷实验"方式,选取少数几组学生,用雨课堂和A+D Lab实验装置相结合进行"电工电子学"多模态实验.实验方式较为灵活多变,能更好地调动学生的积极性、培养学生的创新性.

本研究基于银河麒麟系统和国产飞腾CPU平台,设计开发了一种多通道光功率计测试软件,以解决传统软件依赖于Windows和国外CPU的问题.利用Python编程语言和QT Designer软件,实现了软硬件国产化的多通道光功率计测试系统.该系统通过光波导微生物实验测试,实现了多通道实时数据采集与处理、保存等功能.实验结果表明,与标准设备相比,该软件的测量数据误差在[-0.5％,+0.5％]范围内.实验结果表明该软件具有良好的稳定性,提升了我国光电技术研究的自主可控能力.

为提高风电功率预测精度,提出一种基于变分模态分解(variational mode decomposition,VMD)和改进多元宇宙算法(improved multiverse optimization,IMVO)优化极限学习机(extreme learning machine,ELM)的组合预测方法.首先借助VMD算法将原始风电数据分解为模态分量,并根据互信息熵划分为高、低频分量以简化数据.然后在传统多元宇宙算法基础上通过引入Tent混沌映射、指数型旅行距离率以及精英反向学习机制进行改进,并与ELM相结合得到IMVO-ELM预测模型.最后将高频、低频分量预测结果叠加,得到最终预测结果.仿真结果表明,IMVO-ELM模型预测精度、收敛速度对比 ELM、MVO-ELM、PSO-ELM方法具有一定的优越性.且在借助VMD算法的数据预处理下,预测精度得到进一步提高,验证了所提组合预测方法的有效性.

The flux pumps can realize non-contact excitation of high-temperature superconducting (HTS) magnet and eliminate heat leakage caused by current leads. However, earlier proposed flux pump needs to be installed inside the cryostat, which leads to additional heat load to the cryogenic system. Here, we report the successful demonstration of a through-wall linear-motor type flux pump, with its heating parts such as the copper windings completely outside the cryostat, while its generated heat is dissipated in the air and insulated from the cryostat. With an insulation HTS double pancake coil installed in the cryostat and cooled by a G-M cryogenic cooler at 32.6 K, we have demonstrated the injection of direct currents of 42 A into the closed-loop, without the current leads. Thus, the feasibility and reliability of using the linear-motor type flux pump as the power source to excite the HTS magnet through the cryostat is verified, making it possible for future applications such as in MRI and superconducting motors, etc.

为平抑风电功率波动,弥补单一储能的不足,引入氢和超级电容构成的混合储能装置平滑风电功率波动.针对传统功率分配方法难以建模,容易出现模态混叠现象等问题,以及为了提高储能系统可靠性,提出了一种经验小波变换EWT(empirical wavelet transform)-模糊控制FC(fuzzy control)策略方法.首先,为了验证EWT算法能实现储能设备间功率精确分配,将EWT算法与经验模态分解EMD(empirical mode decomposition)和小波变换WT(wavelet transform)算法进行对比;其次,采用EWT算法分解重构风电原始功率得到并网功率和混合储能平抑功率;最后,考虑超级电容荷电状态SOC(state-of-charge)和储氢罐压力对系统安全稳定运行的影响,采用模糊控制修正储能元件的充放电功率.仿真结果表明,EWT算法避免了模态混叠,实现了储能设备间功率精确分配.该控制策略能有效平抑风电波动,保证了SOC和储氢罐压力在合理范围内,延长了设备寿命,实现系统稳定运行.

In order to satisfy the quality testing needs of nuclear instrumentation system(RPN)intermediate range high pressure plate components,replace manual measurement and improve testing efficiency,the RPN intermediate range high pressure plate detec-tion system based on LabVIEW is designed to complete the integrated automatic test of full-function verification and state assessment of circuit boards.The use of LabVIEW also makes the system has a strong secondary development,users can modify and add func-tions according to the actual situation.In this paper,firstly,the system requirements are analyzed.Secondly,the system design and implementation are carried out according to the system requirements,and finally the system testing and data analysis are carried out to verify the feasibility and accuracy of the system design.

在直流微电网中分布式储能系统起着稳定母线电压、维持系统功率平衡的关键作用.针对多个储能单元中荷电状态(SOC)不同会造成过充或者过放,从而影响系统稳定性的问题,提出一种改进SOC均衡下垂控制策略.首先,将储能装置的下垂系数与SOC嵌套反正切函数联系,充分利用反正切函数和幂函数的优点.其次引入变加速因子,在SOC差异较小时进一步加快均衡速度.同时,为了解决均衡过程中引起的母线电压偏差问题,在上述改进控制策略基础上增加二次电压补偿环节,使用一致性电压均衡器减少母线电压的波动.最后搭建了直流微网储能系统的仿真模型.仿真结果验证了所提控制策略可以动态实现SOC快速均衡,并有效维持了微网内功率平衡和母线电压稳定.

微电源逆变器的传统控制方法具有设计复杂、鲁棒性低等缺点,为了提高微电源逆变器的快速准确响应,提出将模型预测控制(model predictive control,MPC)引入逆变器.根据逆变器并网孤岛状态运行需求,设计了模型预测PQ控制方案和基于下垂特性的U/f模型预测控制方案,通过LC滤波器中电感和电容建立微分方程,推导出相应的数学预测模型,在并网运行时,控制逆变器输出电流跟踪由功率指令生成的参考电流;在孤岛运行时,控制逆变器跟踪功率控制器生成参考电压和频率.仿真表明,2种控制方案都实现了有效跟踪,并且相比于传统PI控制,系统响应速度快、超调小控制精度高.仿真证明了控制策略的可行性,使逆变系统达到了良好的控制效果.

为了平抑风电并网引起的功率波动,以超导磁储能(SMES)和全钒液流电池(VRB)组成的混合储能系统(HESS)为研究对象,针对变流器控制设计了基于径向基函数(RBF)神经网络的比例积分控制器,可根据HESS的动态辨识结果实时改变控制参数,有利于HESS功率指令跟踪和直流侧电压稳定.针对风电的功率分配,采用小波包分解,首先秉持"能者多劳"的原则,设置根据储能荷电状态变化的分频点,灵活分配高、低频功率,从而最大限度地利用储能空间;然后基于VRB能量密度大和使用寿命长的特点,在SMES充放电不足时给予援助性功率支撑,协助SMES迅速恢复最佳状态,有利于更加充分地平滑风电功率波动.在MATLAB/Simulink平台上建模仿真,结果验证了所提方法的优越性.

针对传统最大功率跟踪技术容易陷入局部最大功率点的问题,提出多态蚁群-细菌觅食算法(polymorphic ant colony - bacterial foraging algorithm, PACO-BFOA)来实现部分遮蔽条件下光伏系统的最大功率输出.该算法在传统蚁群算法的基础上引入信息素扩散机制、多态蚁群的概念和细菌的趋化行为,使算法的全局开发和局部探索能力得到了增强.并在太阳辐照恒定、突变和缓慢变化3种环境下进行算法仿真对比验证,结果证明所提出的算法在部分遮蔽及变化光照下均能快速、稳定地在线寻得全局最大功率点.

In order to further optimize the size of the linear-motor type flux pump, an updated linear-motor type motor flux pump device with single side DC winding was designed and fabricated. Compared with the previous generation of linear-motor type flux pump with traveling wave length of 21 mm, the volume of this generation of linear-motor type flux pump with traveling wave length of 15 mm is reduced by nearly 30% and the pumping current capacity is increased by more than 30%, which generated the same DC biased AC travelling magnetic wave in the airgap, and pumped DC current into the high temperature superconducting (HTS) closed-loop in a non-contacting manner, based on the macroscopic magnetic coupling effect. In this work, we tested the performances of this updated flux pump device. We pumped current into two parallel superconducting stators and a YBCO double pancake coils. The pumping current of two parallel superconducting stators reached 219 A, while pumped current in YBCO double cake coil (DPC) reached 73 A, mainly due to the limit of the small critical current of the HTS DPC. The experimental results show that using one-sided DC coil can achieve effective bias effect, which further verified the rationality of explanation based on the macroscopic magnetic coupling effect. These results are helpful to optimize the HTS flux pump device and further understand the working mechanism of the flux pump.

At the unfavorable moments such as island startup, island load switching, and unplanned off-grid, the excessive fluctuation of microgrid bus voltage frequency may seriously damage the electrical equipment of the entire microgrid. The control performance of the energy storage converter selected as the main inverter is vital for maintaining the voltage and frequency stability of the microgrid. Therefore, on the basis of rigorously proving the passivity of the energy storage converter, a dual-passivity-based control strategy suitable for microgrid is proposed to improve the safe and stable operation of the microgrid. A passivity-based control strategy based on the island voltage loop passivity-based controller and the current inner loop passivity-based controller is designed through establishing a port-controlled Hamiltonian model, setting equilibrium points, solving energy matching equations, and correcting damping parameters. The simulation results have verified that the dual-passivity-based control can effectively improve the voltage and frequency stability of the microgrid under islanding/grid-connected operation mode switching, and better ensure the safe and stable operation of the microgrid.

This paper investigated the method of using multiple linear-motor flux pumps to increase the central magnetic field of an HTS magnet composed of six stacking insulated YBCO double pancake coils. In this work, we compared two different excitation methods based on linear-motor flux pumps, i.e., in series excitation and in segmented excitations, to investigate their exciting performances on this HTS magnet. Experiments showed that in the series excitation, the maximum operation current of the HTS magnet was limited by the YBCO coil of the smallest critical current. On the other hand, in the segmented excitations, both the maximum operation current of each YBCO coil and the central magnetic field of the HTS magnet were increased effectively. Moreover, in the segmented excitation, we revealed the interaction between excitation current of one YBCO coil, to the induced currents of other YBCO coils, due to their mutual inductances and different charging sequences. In addition, we found that the charging sequences had an influence on the maximum central magnetic field of the HTS magnet, due to the different vertical field on different YBCO coils, which was consistent with the simulation results. The results of this work showed that using multiple linear-motor flux pumps for excitation can effectively increase the magnetic field of an HTS magnet.

偏远地区5G通讯基站的运行功耗较大,风光新能源构成的基站供电系统可以很好地解决偏远地区电网难以接入的问题.新能源基站供电系统元件容量的选取对系统的稳定性和经济性均有重大影响.为实现稳定性和经济性的综合规划,以等价年金总成本和负荷缺电率最小化为目标函数,以蓄电池荷电状态、年污染物排放量等为约束条件建立容量配置优化模型,提出一种混合NSGA-Ⅱ算法引入帕累托前沿的求解.针对传统NSGA-Ⅱ算法初始群体选取较随意和拥挤度计算方法进行了相应改进,使得改进后的算法收敛性和帕累托前沿多样性有了较大提升.最后,利用改进后的混合NSGA-Ⅱ算法对四川某实际通讯基站供电系统项目进行配置优化求解,验证了混合NSGA-Ⅱ算法的有效性.

The linear-motor type flux pump is a wireless DC power source for high-temperature superconducting coils, which is compact in size, efficient in energy use, fast in output control, etc. It consists of three major parts: DC windings, phase windings and iron circuit, which generates a DC-bias AC travelling wave in its airgap. In theory, there are three controllable parameters such as DC-bias field, amplitude of the AC travelling wave, and the field frequency (travelling speed). By changing those parameters, we change the applied fields and its DC output current into superconducting coils. For studying the impact of those parameters on its DC output, this paper uses a fixed step algorithm to collect the current charging data, by automatically controlling the flux pump device, and then establishes an output database. By using this algorithm, we have searched out the maximum pumped current and analyzed the impact of the three parameters. We have also found out that, in order to get maximum current output, the value of the DC-bias field should be close to the amplitude of AC magnetic field.