A neutral carbolong complex boosts the efficiency of p–i–n perovskite solar cells to 22.7%, and greatly enhances device thermal stability.

Wide gain capability and full range efficiency are critical issues to LLC converters for wide-range applications. To address these issues, this article proposes a variable-mode controlled three-level LLC converter with two parallel diode-clamped legs. The proposed converter has four operation modes with different voltage gains, including the traditional frequency control mode and three new operation modes. With a deep analysis into the voltage gain and soft-switching characteristics of each operation mode, the designed flexible variable-mode control strategy can achieve soft switching and high efficiency over the wide gain range. Furthermore, it ensures smooth transitions among different modes and no surge current in the entire operating range. The effectiveness of the proposed method is investigated by a 400 V input, 8–65 V/1.5 kW output prototype. Experimental results show that the preliminary prototype achieves full zero-voltage-switching capability and maintains high efficiency over the whole output range.

维也纳拓扑的可用空间矢量受电流影响的特性,使得断续空间矢量调制开关序列切换时的衔接问题变得严重.为了探明衔接问题的机理并降低其影响,首先分析在电流不变向时开关序列切换的可能情况,推导计算了在电流变向时因为理想扇区和实际扇区间的滞后超前偏差导致的矢量合成误差,进而给出在切换前后选择特定开关序列的优化策略;然后对目前常见的断续矢量调制方案的衔接情况进行分析,并结合优化策略给出优化方案;最后,通过仿真和实验验证了优化方案可以实现平滑的开关序列衔接,且实现算法简单,具有一定的实用性.

The double-section phenomenon is inherent to the sequential switching shunt regulator (S3R), which increases the bus ripple, affects the poststage filter design, generates electromagnetic interference, and reduces the system reliability. In this article, an in-depth study of the S3R reveals that the double-section phenomenon is caused by a combination of hysteresis loop overlap, sampling integration delay, and parasitic capacitance of the solar panel. To suppress the influence of the double-section phenomenon, according to the working characteristics of S3R, an improved controller is proposed: first, replace the ladder-shaped comparators with the ladder-shaped subtracters and then use fixed frequency control to fix the sampling ripple frequency; subsequently, the specific frequency of the sampling ripple is compensated to reduce the phase shift, thus reducing the delay of the sampling signal, and finally, the S3R’s double-section phenomenon is suppressed. The controller’s specific structure and parameter design procedure are also given in this article. Finally, the correctness and feasibility of the proposed method are proved by building an experimental prototype.

对全桥LLC变换器提出一种柔性多模态的宽增益范围控制策略.文中首先讨论全桥LLC的状态分析模型和现有子模态控制原理,并建立数字辅助设计平台,这些理论、工具为后续工作奠定基础.针对现有全桥LLC变换器各子模态逻辑独立、整体增益范围有限的不足,提出一种全桥变频–移相不对称–DPWM控制的平滑柔性变模态控制策略,并分析各子模态的工作特性,对模态工作机匹配和状态过渡过程等技术问题与设计要点进行详细说明.样机实验证明,所提方法能使全桥LLC变换器实现极宽的增益范围,并能在全工作范围内保证变换器零电压开通,实现高工作效率.

对箝位桥并联型LLC变换器提出了多模态的宽增益范围控制策略.首先讨论了箝位桥并联型LLC变换器的子模态控制原理及工作特性.针对现有控制方案各子模态逻辑独立、整体增益范围有限等不足,对箝位桥并联型LLC变换器提出一种平滑柔性多模态控制策略,并说明了各子模态的工作特性及整体控制方法.样机实验证明所提方法能使箝位桥并联型LLC变换器实现极宽的增益范围,且在全工作范围内保证变换器零电压开通,拓宽副边零电流关断范围,实现宽范围下的高工作效率.

分析了双移相控制下CLLC谐振变换器的工作原理,建立时域模型确定了电路状态变量以及增益曲线的解析解,并进一步对其软开关范围进行分析.时域分析表明,变换器在保证软开关的条件下,能够实现宽电压范围输出,同时其具有恒流源输出特性.搭建了样机对时域分析结果进行实验验证,实验结果表明变换器输出为恒流,且在软开关的条件下最高增益达到了 0.54,最低增益几乎为零.

The structural design and tuning of properties of metallaaromatics are crucial in materials and energy science. Herein, we describe the rapid synthesis of tetracyclic metallaaromatics containing quinoline and pentalene motifs fused by a metal-bridged fragment. These unique compounds display remarkably broad absorption, enabling for the first time the absorption of metallaaromatics to reach the second near-infrared (NIR-II) bio-window. The formation of osmaquinoline unit involves an unconventional C(sp2 )-C(sp3 ) coupling promoted by AgBF4 to achieve [3+3] cycloaddition. The introduction of cyclic dπ -pπ conjugation and extension of the aromatic π-framework can effectively shrink the HOMO-LUMO gap, thus broadening the absorption window. The considerable photothermal conversion efficiency (PCE) in both the NIR-I and NIR-II windows, the high photothermal stability and the excellent electrochemical behavior suggest many potential applications of these condensed metallaquinolines.

Big capacity (>4000 Ah) lead acid battery is necessary to important emergency power system. Electrochemical impedance spectroscopy (EIS) of the battery is weak. Low frequency Digital Lock-in Amplifier (DLA) needs long-term sampling. Fast Fourier Transformation (FFT) needs whole number periods sampling. This paper suggests a Fast Lock-in Amplifier (FLA). It takes place of low pass filter with linear average definite digital Integrator. The FLA can output at short-term and partial period sampling. Its result is a fast linear interpolation of FFT. Results of FLA and FFT are identical at whole number periods sampling. The proposed method is verified by Valve-Regulated Lead-Acid (VRLA) battery (4200 Ah) aging tests. Microcontroller runs the proposed algorithm.

Flooded lead-acid battery dominates the emergency power supply system of nuclear power plants. However, Valve-Regulated Lead-Acid (VRLA) battery occupies important parts in emergency power supply systems. Structure design for internal consistency of big capacity is a challenge. Electrical variables of battery fluctuate as hysteresis while aging. This paper decouples terminal voltage in deep discharge by concentration polarization of electrolyte. Voltages of both bulk electrolyte capacitance and internal resistance are constants. This principle presents a novel model of dynamic threshold of contacting resistance. The model is sensitive to the battery nonlinear hysteresis. The model alarms remaining useful capacity at the end of service life. Parallel experiments at 4200 (Ah) VRLA batteries verifies the model. A Microchip embedded management board runs the algorithm.

The important emergency power supply needs a large capacity battery. The batteries are long-term float charging. Electrochemical impedance spectroscopy (EIS) is important for remaining useful capacity warnings. This paper establishes the EIS inverse calculation technique that is centered in the vector objective function and linear interpolation search algorithm. This technique simplifies the initial value preparation and the gradient descent direction search for the inverse calculation of EIS. The root-mean-square errors of online embedded programming are smaller than the offline results of numerical software for EIS. The vector objective function targets the rotation angle of the initial polarization impedance vector to be zero during the EIS inverse calculation. This equivalently replaces the regular minimization of root-mean-square error. The linear interpolation algorithm simplifies the gradient descent direction search to a one-dimensional search for the double-layer capacitance of the initial polarization impedance. This algorithm replaces the conventional graphic method and evolutionary algorithm. The proposed algorithm is verified by the microcontroller at Valve-regulated lead-acid (VRLA) batteries (4200 Ah). The result of the algorithm is close to special numerical software for EIS. This algorithm improves the performance of an embedded management board.

Grid-connected power electronic devices, such as voltage-source inverters (VSIs), are increasingly installed in the grid for the utilization of renewable energy sources. Under high penetration, the weak grid contains plentiful harmonics and complex grid impedance values, which have deep impacts on system stability as well as its control performance. Online impedance measurement is needed for impedance based adaptive control and analysis. This paper proposes a variable carrier frequency PWM (VCFPWM) based online grid impedance measurement technology. This method broadens the available working range in the high frequency band without increasing the low band perturbations. Through good analysis and design of the carrier frequency, the VCFPWM method injects sufficient harmonic energy at specified high frequency points and guarantees low THDs at the same time. The detailed design considerations of the carrier frequency are clarified and the characteristics of the VCFPWM based excitations are analyzed in this paper. Finally, the simulation and experimental results based on a three-phase grid-connected VSI are presented to verify the effectiveness of the proposed method.

As front-end rectifier, Vienna topology is widely used in many applications. However, the available space vector of the Vienna topology is affected by the current, which leads to transition problem when the state sequence of the three-phase switch changes, especially under the discontinuous space vector modulation. To find out the mechanism of transition problems and reduce its impact, firstly, the possible situation of sequence transition when the current does not change is analyzed. And then the vector synthesis error caused by the lag or lead deviation between the ideal sector and the actual sector when the current change is deduced. On this basis, an optimization strategy for selecting a specific switching sequence before and after transition is given. In addition, the sequence transition problems of several common discontinuous vector modulation schemes are analyzed, and the optimization scheme is given in combination with the proposed optimization strategy. Finally, simulations and experiments verify that the optimized scheme can achieve smooth sequence transition, and the corresponding optimization strategy is simple to implement and has certain practicability.

多脉波整流技术是大功率整流系统抑制谐波电流的主要手段之一,传统的24脉波整流器串联工作时存在网侧谐波电流过高的缺陷.为此,对传统24脉波整流器进行改造,通过增加若干切换开关,得到一种具有混合工作模式的变拓扑双12脉波整流器.研究了开关状态的不同组合与串联、并联和冗余工作模式的对应关系,详细分析了混合工作模式的等效电路和电流预测控制的实现机理,进一步研究了电流预测控制策略实现不同工作模式间的快速切换和输出电流的快速响应问题.最后,通过仿真分析和实验验证了电流预测控制策略的有效性,结果表明在相同负载电压下,混合模式的网侧谐波电流低于串联模式.

The control delay weakens the active damping (AD) performance of digitally controlled LCL/LLCL-type grid-connected inverters (GCIs). The equivalent virtual impedance paralleled with the filter branch explains the effect of the capacitor-current-feedback AD. However, the virtual impedance appears capacitive or even negative due to the delay, which significantly weakens the effectiveness of AD. This paper proposes a single-cycle-lag compensator (SCLC) to eliminate the adverse effects caused by the control delay. The method retains effectiveness in applications with high resonant frequency or large control delay. It keeps system a positive equivalent resistance with a high equivalent inductance. The positive equivalent resistance leads to positive damping effect, while the high equivalent inductance causing little resonant frequency deviation can be neglected. Moreover, the effect of the impedance variation that causes the resonant frequency deviation is analyzed and the restrictions of the proposed method are discussed. By optimizing theLCL/LLCL filter parameters, the adaptability of the SCLC to the grid impedance variation can be further improved. With the SCLC, the LCL/LLCL-type GCIs achieve better steady-state and dynamic performances. Finally, experimental results are presented to verify the proposed method.

Both the frequency domain Nyquist curve of electrochemical impedance spectroscopy (EIS) and time domain simulation of DC equivalent first principle linear circuit (FPLCDCequ) are some of the fundamentals of lead-acid batteries management system design. The Nyquist curve is used to evaluate batteries’ state of health (SoH), but the curve does not distinguish charging/discharging impedances on electrode–electrolyte interfaces in the frequency domain. FPLCDCequ is used to simulate batteries’ terminal electrical variables, and the circuit distinguishes charging/discharging impedances on electrode–electrolyte interfaces in the time domain. Therefore, there is no direct physical relationship between Nyquist and FPLCDCequ This paper proposes an AC equivalent first principle linear circuit (FPLCACequ) by average switch modeling, and the novel circuit distinguishes charging/discharging impedances on electrode–electrolyte interfaces in Nyquist. The novel circuit establishes a physical bridge between Nyquist and FPLCDCequ for lead-acid batteries management system design.

Lead-acid batteries are widely used as backup in power systems. Recently, charge-transfer resistances on electrode-electrolyte interface have been studied to estimate state of health (SOH) in backup batteries, and some conclusions have been obtained. Charge-transfer resistances do nonlinearly characterize full-scale SOH in specific degradation experiment on 10 Ah batteries. This paper proposes characteristic charge-transfer resistances, combining with charge-transfer resistances to linearly characterize multi-scale SOH on four 500 Ah batteries in parallel experiments. The results provide viable solution for linear estimation of targeting-scale SOH (500 Ah similar to 250 Ah) on lead-acid batteries. (c) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

中压变换器的测试面临着供电电压高、能耗大、测试平台建设成本高等问题,实验室常使用共直流母线的对拖测试平台以降低对供电和负载的要求,并通过虚拟负载的手段降低测试平台的建设成本.但由于这种测试平台共模通路阻抗较小,容易形成很大的共模电流,因而无法测试变换器采用空间矢量调制(SVM)或注入零序分量脉宽调制(PWM)的运行工况.为此,这里提出了一种提升共模回路阻抗的陪测变换器控制方法.该方法利用谐振控制抑制共模电流的低频分量,通过注入稳态分量抑制共模电流的高频分量,从而有效提高了零序分量通路的阻抗,使被测变换器可注入零序分量,测试工况更接近实际工况,并拓宽了测试范围.

在有位置精度要求的伺服电机控制应用场合,为了降低电机控制系统的成本,设计了一种永磁同步电机(PMSM)的无电流传感器控制方法.基于矢量控制策略,通过电机定子电压方程对定子电流进行迭代估算,根据系统响应速度要求,对控制器参数进行了设计,利用Bode图分析了系统的带宽,在不使用电流传感器的情况下实现了PMSM位置环、速度环和电流环控制,通过仿真验证了该控制器参数的有效性.在表贴式永磁同步电机(SPMSM)上进行了位置控制实验,动态响应效果满足设计要求,验证了该方案的有效性和可行性.

The modular multilevel matrix converter (M3C) is introduced and applied to a single-stage ac/dc solid-state transformer (SST), which uses only one concentrated medium-frequency transformer (MFT) for isolation. As a result, the transformer insulation design is simplified significantly and higher power density could be achieved. Meanwhile, a novel decoupling transformation based on two internal three-phase circulating systems is proposed to improve the previous method. Through this transformation, the unbalanced capacitor voltage components can be divided into four independent dimensions, which correspond to four kinds of capacitor voltage ripple frequency. And a dc-side vector model is then established to calculate the required circulating current reference for capacitor balancing. Besides, under the application of SST, the capacitor voltage ripple suppression strategy via injection of extra circulating current is proposed. The amplitude and frequency index is optimized to obtain the best effect. Therefore, the submodule capacitor volume can be reduced to achieve higher power density. Simulation and experimental results are also provided to verify the theoretical analysis.