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To address the challenge of solving the zero-pole of transcendental equation for distributed power station with simultaneous consideration of two factors， i.e.， dq-axis coupling and line distribution parameter， an impedance model for distributed power station considering the two factors is established. This paper proposes a matrix-determinant zero-pole solution method for transcendental equation using Padé approximation and provides detailed steps for calculating the zero-pole distribution of the transfer function. Furthermore，it analyzes the impact of the two factors on harmonic instability analysis in the system under different scenarios. The research demonstrates that the proposed method can accurately analyze harmonic instability issues when these two factors are considered simultaneously. And ignoring one of the two factors may result in the misjudgment of stability， and considering the line distribution parameter is a necessary prerequisite for solving the amplification point of high-frequency harmonics. The effectiveness of the proposed method is verified by simulation.

To calculate the harmonic impedance on the system side is crucial for the safe and stable operation of the new power system. Existing algorithms for harmonic impedance estimation usually assume that the harmonic impedance on the system side is constant during the measurement period. However, the voltage on the system side always changes according to the working mode of the power grid or access of large power load demand, resulting in fluctuations of the harmonic impedance on the system side. Luckly, the harmonic impedance on the system side does not change much in the adjacent sampling time interval. On this basis, the paper proposes a new non-intervention solution for the variable harmonic impedance on the system side. In this method, the second-order change of the harmonic impedance and the second-order change of voltage in the adjacent sampling time interval are taken as the objective function. The harmonic impedance on the system side is solved by minimizing the target function. The proposed method is proved to be accurate and reliable by simulation and practical analysis, especially in the condition that the strong background harmonic or user-side harmonic impedance is not much stronger than the harmonic impedance on the system side.

The distributed parameter model of the transmission line is a necessary premise for accurately analysing the harmonic instability of the wind farm. However, when the model is used for harmonic instability analysis, it causes difficulties in solving the zero and pole distributions of the transcendental equation of the system. Given this, the impedance model of the wind farm considering the line distribution parameters is established and verified. Next, a method based on Pade approximation to solve the zero and pole distributions of the transcendental equation is proposed. The exponential function is approximated to the rational fraction only by selecting the order of the rational fraction, without fitting coefficients. Further, the influence of different transmission line models on the harmonic instability under different line lengths and grid strengths is analyzed. Finally, the effectiveness of the proposed method is verified by the simulation case. The results show that the effect of distribution parameters cannot be ignored, otherwise, it may lead to the inaccurate analysis of stability and deviation or even omission of harmonic amplification points in the high-frequency band. The proposed method can not only accurately evaluate the stability of the system, but also analyze the harmonic amplification points.

Soft robots have drawn a lot of attention due to their soft materials that make them highly flexible and adaptable to complex environments. However, these also make soft robots not suited to high-load tasks, and achieving controllable material stiffness variation is still a challenge. Herein, we designed a soft structure with variable stiffness based on electrorheological fluids, which presented the advantages of continuously variable stiffness and fast response. The structure exhibited a stiffness of up to 1065 mN mm−1 when the electric field strength was 4.5 kV mm−1 (displacement of 1 mm). When varying the electric field strength (0 to 4.5 kV mm−1), the rate of stiffness variation was over 1500%. According to the load cycle experiments, it was shown that the structure's response time to a change in load was less than 65 ms, and that the structure changes could be made repeatedly. In addition, we demonstrated the functions of stiffness adjustment, shape memory, and motion locking of the structure. This work has potential applications in the fields of soft robotics and artificial muscles. [ABSTRACT FROM AUTHOR]

Estimation of harmonic impedances and harmonic contributions is beneficial to harmonic control, and harmonic phasors data is necessary for the existing estimation methods. However, the phase angles of harmonic phasors are not recorded in some of current power quality measuring instruments (such as Fluke 1760 etc.), which makes the existing methods unavailable. To solve this problem, the Norton equivalent circuit model under harmonic frequency is improved and a new model composed of harmonic complex power sources and harmonic impedances is proposed. Based on the model, the harmonic impedance and harmonic contribution can be estimated by using independent component analysis algorithm, and the harmonic phasor data is no longer required. The superiority of the proposed model is verified through simulation and field cases. [ABSTRACT FROM AUTHOR]

Effects from ion thruster plume have long raised concerns. However, little work has systematically analyzed the influencing parameters in the ion thruster plume simulation. This paper analyzes LIPS 200 ion thruster plume simulations about the influencing parameters. The numerical simulations are carried out by a hybrid particle-in-cell (PIC) method and the direct simulation Monte Carlo (DSMC) method. The PIC method is employed for the plasma dynamics, and the DSMC method is used for collisions. Simulation results were compared in detail to obtain the variation of the results with the parameters. Besides, experimental data were compared to simulation results to optimize the parameters. Finally, with these researches, the optimal parameters are obtained. [ABSTRACT FROM AUTHOR]

A thermostatic E × B probe is designed to protect the probe body from the thermal effect of the plasma plume that has a significant influence on the resolution of the probe for high-power electric thrusters. An active cooling system, which consists of a cooling panel and carbon fiber felts combined with a recycling system of liquid coolants or an open-type system of gas coolants, is employed to realize the protection of the probe. The threshold for the design parameters for the active cooling system is estimated by deriving the energy transfer of the plasma plume–probe body interaction and the energy taken away by the coolants, and the design details are explained. The diagnostics of the LIPS-300 ion thruster with a power of 3 kW and a screen-grid voltage of 1450 V was implemented by the designed thermostatic E × B probe. The measured spectra illustrate that the thermostatic E × B probe can distinguish the fractions of Xe+ ions and Xe2+ ions without areas of overlap. In addition, the temperature of the probe body was less than 306 K in the beam region of the plasma plume during the 200-min-long continuous test. A thermostatic E × B probe is useful for enhancing the viability and versatility of equipment and for reducing uneconomical and complex test procedures. [ABSTRACT FROM AUTHOR]

A thermostatic E × B probe is designed to protect the probe body from the thermal effect of the plasma plume that has a significant influence on the resolution of the probe for high-power electric thrusters. An active cooling system, which consists of a cooling panel and carbon fiber felts combined with a recycling system of liquid coolants or an open-type system of gas coolants, is employed to realize the protection of the probe. The threshold for the design parameters for the active cooling system is estimated by deriving the energy transfer of the plasma plume–probe body interaction and the energy taken away by the coolants, and the design details are explained. The diagnostics of the LIPS-300 ion thruster with a power of 3 kW and a screen-grid voltage of 1450 V was implemented by the designed thermostatic E × B probe. The measured spectra illustrate that the thermostatic E × B probe can distinguish the fractions of Xe+ ions and Xe2+ ions without areas of overlap. In addition, the temperature of the probe body was less than 306 K in the beam region of the plasma plume during the 200-min-long continuous test. A thermostatic E × B probe is useful for enhancing the viability and versatility of equipment and for reducing uneconomical and complex test procedures. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is one of the promising two-dimensional nanomaterials for the development of fluorescent aptasensors. Its limitations are related to the inevitable negative effect of GO on the fluorescence. Here this challenge was explored and solved by ssDNA adsorption on GO and centrifugal separation of GO from the ensembled solution. On this basis, a fluorescent aptasensor was constructed for the detection of staphylococcal enterotoxin A (SEA), in which GO assisted the separation of free aptamers to achieve cDNA-induced structure-switching from SEA/aptamer complex to dsDNA, and GO was added again to separate free cDNA and reduce the background signal. SYBR Green I was inserted into dsDNA as the fluorescent signal to achieve the quantitative analysis. It displayed a wide linear range (1–8000 ng/mL), low detection limit (0.899 ng/mL), and satisfactory application in milk and milk powder. Notably, the method was low-cost, general, and instructive for other two-dimensional nanomaterials. [Display omitted] • A label-free, low-background fluorescent aptasensor for staphylococcal enterotoxin A. • Graphene oxide-assisted ssDNA separation to reduce the background and interference. • The cDNA-induced structure-switching formed dsDNA and amplified the signal. • The method was low-cost, general, and instructive for two-dimensional nanomaterials. [ABSTRACT FROM AUTHOR]