Maintaining the frequency within an allowable range is the necessity to ensure the stable operation of the grid. When a large-scale frequency disturbance occurs in the grid, the synchronous generators (SGs) will temporarily release the kinetic energy to make the generation and demand balanced. This is well known as the inertial response of the SG. However, the traditional variable-speed wind turbines (VSWTs) only generate a negligible inertial response when a frequency disturbance happens. The traditional VSWT is designed to maximise the wind energy injected into the grid. Thus, when a frequency disturbance is detected in the grid, the traditional VSWT cannot change the active power output to support the grid. To solve this problem, the concepts of the inertial control and inertial support capability for VSWT were proposed. The inertial control measures the frequency of the grid and adjusts the active power output of VSWT. Thus, during the frequency disturbance, the VSWT has the inertial support capability. The purpose of this study is to provide a comprehensive review of the inertial control for the wind power plant (WPP) consisting of VSWTs. With the inertial control, the integration of the WPPs can enhance the frequency stability of the grid.

This article presents a review of physical, analytical, and compact models for oxide-based RRAM devices. An analysis of how the electrical, physical, and thermal parameters affect resistive switching and the different current conduction mechanisms that exist in the models is performed. Two different physical mechanisms that drive resistive switching; drift diffusion and redox which are widely adopted in models are studied. As for the current conduction mechanisms adopted in the models, Schottky and generalised hopping mechanisms are investigated. It is shown that resistive switching is strongly influenced by the electric field and temperature, while the current conduction is weakly dependent on the temperature. The resistive switching and current conduction mechanisms in RRAMs are highly dependent on the geometry of the conductive filament (CF). 2D and 3D models which incorporate the rupture/formation of the CF together with the variation of the filament radius present accurate resistive switching behaviour.

The authors study the sum rate of a two-unicast wireless energy harvesting system. The system consists of two source nodes, two destination nodes and one energy constrained relay node, which only harvests energy from the signals transmitted by the source nodes for its operation. Each source node transmits the signal to its corresponding destination node via the help of the relay node. The transmission process is divided into two time slots each with the same time duration. In the first time slot, two source nodes transmit the signals to the relay node and the destination nodes, and the relay node uses the power splitting (PS) protocol for harvesting energy. In the second time slot, adopting analogue network coding, the relay node retransmits the mixed signal to the destination nodes using the harvested energy. Considering network coding noise, the analytical expressions of a near optimal adaptive PS factor that leads to a maximal sum rate is derived. Numerical results corroborate the analytical results and show the superior performance of the proposed scheme in comparison with the conventional one.

The accuracy of the grinding robot's vision measurement system directly affects the machining accuracy. This study proposes a calibration method of the visual measurement system installed on the fourth joint of the ceramic billet grinding robot. This calibration method includes two steps: preliminary calibration and precise calibration. Preliminary calibration is to fit the transformation matrix between robot frame and vision measurement system frame by describing the same workpiece in different frames. In the precise calibration, the visual measurement error compensation model includes the kinematics error of the robot and the preliminary calibration error. The experimental results show that the calibration method proposed in this study can calibrate the three-dimensional (3D) vision measurement system of the robot with high precision. Besides, the repeated measurements of the same spatial point by the vision measurement system in different poses indicate that the calibrated visual system has good detection stability. The calibration method only needs to use the laser tracker and 3D scanner to collect the coordinates of the space point to complete the calibration process, which is suitable for the industrial site.

This study presents a fixed-frequency hysteretic buck converter designed and fabricated using 0.18-µm complementary metal–oxide–semiconductor process. With a phase-locked loop (PLL)-based adaptive window control, the proposed buck converter can achieve a fixed switching frequency, and this frequency can be tuned within a certain range through a reference clock frequency. Concurrently, a novel auxiliary circuit is proposed to monitor the converter's output loading dynamics to reduce the converter's transient recovery time. It will also help to regulate the output voltage at the steady-state operation as well. With the supply voltage ranging from 3 to 4.2 V and an output voltage of 1.8 V, the simulated switching frequency is maintained at 10 MHz because of the PLL control. The transient response time is only 0.3 and 0.4 µs for a 400 mA step-up load and step-down load, respectively.

Gallium nitride (GaN) high-electron-mobility transistor (HEMT) with the merits of the fast switch speed, low on resistance and low switch loss is applicable to high-frequency LLC converters. However, voltage stress and ringing problems during the fast switching transient have retarded the promotion of switch speed and prolonged the design cycles. This study proposed an economic and time-saving virtual prototype based LLC converter design method, based on which the voltage stress and ringing problem can be analysed and suppressed by iteration design. The virtual prototype comprises of compact GaN HEMT device model and accurate circuit model. The correctness and effectiveness of the virtual-prototype-based design method is verified with well matching simulation and experiment waveforms.

This article presents an extended backstepping control method to reduce the grid-side current harmonics caused by grid voltage distortion. A dynamic model considering the grid voltage as an external disturbance is derived in the stationary reference frame. The extended back-stepping design procedure based on pole displacement guarantees that the system is stable without damping. The proposed method has a general low-order harmonics suppression instead of selective harmonics elimination. Zero steady-state error can be obtained tracking the grid currents. Stability, as well as good transient and steady-state performance are verified through numerical simulation. A comparison with the state-of-the-art proportional resonant control with active damping is also conducted. The results show that a good low-order harmonics reduction in the grid current is achieved by the proposed control method.

This study investigates a novel method of undertaking online electrochemical impedance spectroscopy measurements to estimate battery impedance across the frequency range using a battery balancing circuit. A switched capacitor balancing system is used to generate an excitation signal of low-frequency of variable values from which battery voltage and current can be measured to estimate the impedance.