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Synchronous condensers (SCs) are generally used at the receiving-end stations of ultra-high-voltage direct current (UHVDC) transmission systems due to their strong reactive power support and flexible regulation of reactive power according to the interconnected grids operating conditions. In this paper, different starting control schemes of a SC integrated power grid are investigated providing four main contributions: 1) The principle of reactive power support of the SC on the interconnected power grid is analytically studied, providing the establishment of mathematical models. 2) Four different starting control schemes are developed for the initialization and SC integration, i.e. in Scheme 1, a preset initial falling speed is directly utilized without initialization; in Scheme 2, a black start sequential control approach with a static frequency converter (SFC) is proposed; in Scheme 3, PI/PD/PID controllers are respectively applied for the excitation device at the speed-falling stage; in Scheme 4, a pre-insertion approach of an energy absorption component with R/L/RL is utilized to suppress the surges at the SC integration instant. 3) The dynamic behaviors of four different starting schemes at specific operating stages are evaluated. 4) The success rate of SC integration is analyzed to evaluate starting control performance. Performance of the SC interconnected system with four different starting control schemes is evaluated in the time-domain simulation environment PSCAD/EMTDC™. The results prove the superiority of the proposed starting control approach in Scheme 4.

This paper was concerned with the problem of filter design for the continuous-discrete system in the Takagi-Sugeno (T-S) fuzzy model. In a known finite frequency (FF) domain, an FF $ H_\infty $ performance was defined for the nonlinear continuous-discrete system. With the designed filter, sufficient conditions were then established for the filtering error system to be asymptotically stable and having a prescribed FF $ H_\infty $ performance. After that, a systematic method for the filter design was proposed. Finally, an example was provided to check effectiveness of the derived results.

Autonomous berthing is the last step to achieving the autonomous operation of unmanned surface vehicles (USVs). Due to the significant disturbance of wind, waves, and currents and the uncertainties of the model, it is difficult to realize autonomous berthing. For the case of obstacles and dynamics of USVs, it is transformed into three steps including path planning, path tracking, and motion control of USVs in the paper. A new advanced Dubins-RRT algorithm is proposed for path planning, which improves the capacity of obstacle avoidance and path smoothness level. A virtual target guidance method is used to guide and track the planned path. In addition, a finite-time disturbance observer and a non-singular terminal sliding mode controller are designed to control the autonomous USVs. Observing and estimating the uncertainty terms in the model can ensure the convergence of the tracking error in a finite time. Finally, the feasibility of the designed method is verified through simulation and experimentation.

In this paper, the control methodology of the common capacitor voltage and the DC current flow controller (DC CFC) under self-fault conditions are investigated with the following two contributions. (1) A selection method of the common capacitor voltage based on various specific control requirements with explicit control margins of the DC line currents is proposed with analytic derivations of two-line/three-line DC CFCs in the meshed three-terminal/four-terminal high-voltage direct current grids (HVDC), respectively. (2) The impact of different self-faults of the DC CFC on the control performance of the DC line currents is analyzed with a simplified topology with unidirectional current flow presented. Case studies are conducted in the time-domain simulation environment PSCAD/EMTDC and the results justify the effectiveness of the theoretical analysis. The proposed common capacitor voltage control method and self-fault analysis would be useful for practical applications of the DC CFC under both steady and transient states.

To improve the detection of dim and small targets in low signal-to-noise ratio (SNR < 3dB) scenarios, energy accumulation along the estimated direction by estimating the direction of the target’s motion at different moments is a proven approach, and considering that the Gaussian Markov random field can well describe the correlation of image element points in their air and time domains, Gaussian Markov random field is introduced into the paper to process the image. Firstly, by combining the proximity of image element spatial coordinates and the correlation of image element values to construct a new adaptive Gaussian weighted Markov random field filtering model, which fully incorporates the spatio-temporal information of image element coordinates and the correlation degree information of image element values for weighting to describe the image element neighborhood system. Second, to further enhance the energy of weak targets, the energy accumulation of targets is achieved by establishing a Gaussian Markov random field motion direction estimation model on the basis of obtaining filtered images. Through experiments, it is shown that the algorithm proposed in this paper can effectively accumulate the weak signal of the target between frames, and the target signal-to-noise ratio can reach more than 6dB compared with that before enhancement, effectively improving the detection ability of weak targets.

This paper is concerned with the problem of finite-time l1-gain control for positive switched systems with time-varying delay via delta operator approach. Firstly, sufficient conditions which can guarantee the l1-gain finite-time boundedness of the underlying system are given by using the average dwell time approach and constructing an appropriate copositive type Lyapunov-Krasovskii functional in delta domain. Moreover, the obtained conditions can unify some previously suggested relevant results seen in literature of both continuous and discrete systems into the delta operator framework. Then, based on the results obtained, a state feedback controller is designed to ensure that the resulting closed-loop system is finite-time bounded with an l1-gain performance. Finally, a numerical example is presented to demonstrate the effectiveness and feasibility of the proposed method.

This paper is concerned with the design problem of robust switching rule for Boost converters with uncertain parameters and disturbances. Firstly, the Boost converter is modeled as a switched affine linear system with uncertain parameters and disturbances. Then, using common Lyapunov function approach and linear matrix inequality (LMI) technique, a novel switching rule is proposed such that the model reference tracking performance is satisfied. Finally, a simulation result is provided to show the validity of the proposed method.

This paper is concerned with the problem of robust stabilization for a class of uncertain two-dimensional (2D) discrete switched systems with state delays under asynchronous switching. The asynchronous switching here means that the switching instants of the controller experience delays with respect to those of the system. The parameter uncertainties are assumed to be norm-bounded. A state feedback controller is proposed to guarantee the exponential stability. The dwell time approach is utilized for the stability analysis and controller design. A numerical example is given to illustrate the effectiveness of the proposed method.

This paper investigates the problem of observer-based robust control for a class of switched stochastic systems with time-varying delay. Based on the average dwell time method, an exponential stability criterion for switched stochastic delay systems is proposed. Then, performance analysis and observer-based robust controller design for the underlying systems are developed. Finally, a numerical example is presented to illustrate the effectiveness of the proposed approach.

This paper is concerned with the problem of designing a robust observer-based controller for discrete-time networked systems with limited information. An improved networked control system model is proposed and the effects of random packet dropout, time-varying delay, and quantization are considered simultaneously. Based on the obtained model, a stability criterion is developed by constructing an appropriate Lyapunov-Krasovskii functional and sufficient conditions for the existence of a dynamic quantized output feedback controller which are given in terms of linear matrix inequalities (LMIs) such that the augmented error system is stochastically stable with an performance level. An example is presented to illustrate the effectiveness of the proposed method.

The problems of mean-square exponential stability and robust H∞ control of switched stochastic systems with time-varying delay are investigated in this paper. Based on the average dwell time method and Gronwall-Bellman inequality, a new mean-square exponential stability criterion of such system is derived in terms of linear matrix inequalities (LMIs). Then, H∞ performance is studied and robust H∞ controller is designed. Finally, a numerical example is given to illustrate the effectiveness of the proposed approach.