In the virtual synchronous generator (VSG) field, the traditional methods, such as the constant parameters control method and the self-adaptive inertia control method, always neglect the effect of the damping factor. This letter proposes a self-adaptive inertia and damping combination control method to improve the frequency stability with an interleaving control technique. Tests on the MATLAB/Simulink VSG model demonstrate the effectiveness of the proposed method.

Uncertainty introduces both significant complexity and the high risk of suboptimal investment decisions into power system planning. Considering the multiple uncertainties of wind and solar power output, load demands, and energy prices as well as pollutant emission factors during the planning period, a multi-scenario stochastic programming model of an integrated energy system (IES) is constructed in this paper. Scenarios of wind and solar power output are generated based on non-parametric kernel density estimation and the Frank-Copula function; scenarios of load demands are generated through DeST software, and energy prices and pollutant emission factors are generated corresponding to a uniform distribution. Then the generated scenario results of wind and solar power output and load demands are reduced by ${k}$ -means clustering; the generated scenarios of energy prices and pollutant emission factors are reduced by discrete approximation of continuous distribution based on Gaussian quadrature. An illustrative example with 8 cases is performed to analyze the influences of each uncertain parameter on the optimal configuration and economy of the IES.

The universal use of open communication networks in interconnected power systems has changed the constant delay in the formerly dedicated channels into time-varying delay. The delay will deteriorate the dynamic performance of the load frequency control and lead to system frequency instability. This paper presents a fractional-order sliding mode controller for interconnected power systems with time-varying delay and performs stability analysis based on the Lyapunov direct method. Firstly, fractional-order integral sliding mode control is used to improve the stability of interconnected power systems containing time-varying delay. This expands the delay margin by taking advantage of the scalability of the fractional-order to the sliding mode surface. Then, the Riemann-Liouville fractional-order Lyapunov functional is introduced to stability analysis. This reduced the conservatism of the stability analysis by adjusting the upper limit of the functional integral. Lastly, combining Lyapunov's theory and integral inequality to obtain the stability conditions of the time-varying delay power system described by linear matrix inequality, and bring the stability margin of the system. The simulation results show that the designed controller can guarantee that the maximum delay time of the system is less than a predefined upper limit. The proposed control strategy obtains a larger stability margin than the other four scenarios. Additional simulation study was also conducted to verify its robustness to load variations and wind fluctuations.

With more renewable resources are integrated into the receiving-end AC grid through the LCC-HVDC link, a single-infeed LCC-HVDC (SIDC) system is facing a critical subsequent commutation failure (SCF), which stems from the poor dynamic reactive power support capability of the existing LCC-HVDC link's control strategies. This letter proposes a general self-adaptive DC current control (GSDC ² ) of LCC-HVDC to eliminate the SCF, based on the dynamic reactive power interaction mechanism. Then, multiple comparative studies with the existing control strategies are implemented to verify the validation of the proposed control strategy by PSCAD/EMTDC ^TM . A fast evaluation index, called general commutation failure immunity index (GCFII), is also defined to show the performance of the proposed control strategy in eliminating the SCF.

As large-scale offshore wind farms are integrated into the power grid, a hybrid multi-infeed HVDC (HMIDC) system including both LCC-HVDC and VSC-HVDC links is facing a critical steady-state voltage stability problem which mainly stems from a weak AC system under high-level DC power injections. To overcome this challenge, this paper proposes a general steady-state voltage stability analysis to accurately measure the critical voltage stability point of HMIDC systems. In this paper, a typical HMIDC system is firstly modeled as a general dual-infeed system composed of an LCC-HVDC, a VSC-HVDC, and a virtual equivalent voltage source behind a virtual equivalent impedance at the AC side. Then a hybrid power sensitive factor (HPSF) is established to indicate the critical voltage stability point with the consideration of dynamic power-voltage characteristics of HVDC links, as well as operational changes in AC system (e.g. dynamics of excitation voltage control in generator and network topology change). Finally, a general voltage stability index, called hybrid generalized short circuit ratio (HGSCR), is further derived to effectively explain the critical voltage stability point of HMIDC systems. Moreover, multiple comparative studies with existing voltage stability indices are conducted in this paper to verify the effectiveness of the proposed general steady-state voltage stability analysis by using both PSCAD/EMTDC™ power flow and time-domain simulations.

The wound field doubly salient generator (WFDSG) are receiving consideration for the field of industrial and aerospace/aviation, since it has the advantages of high robustness with simple structure and adjustable output voltage. In this paper, upon the analysis of generator structures, the features of three rectifiers which are suitable for WFDSG are analyzed in detail. The comparative research of WFDSG with hybrid half-bridge rectifier (HHBR), full-bridge rectifier (FBR) and half-bridge rectifier (HBR) is presented by the finite-element method (FEM). Then, the load and no-load characteristics of WFDSG under the three rectifiers mentioned above are researched comparatively. The commutation overlap angles and total commutation output voltage losses of three rectifiers are deduced. The experiments of a 12/8-pole single armature-winding WFDSG (SAW-WFDSG) with FBR and a 12/8-pole dual armature-winding WFDSG (DAW-WFDSG) with HHBR prototypes have been performed. The FEM and experiment results shows that the SAW-WFDSG with FBR and the DAW-WFDSG with HHBR both have a good application prospect.