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With the continuous expansion of the scale of power generated by grid-connected renewable energy, the form and operation characteristics of power grids have undergone significant changes, and the power electronic characteristics of power systems are prominent, resulting in the frequent occurrence of wide-band oscillation problems when renewable energy power generation equipment is connected to a power grid. Oscillation has the characteristics of nonlinearity and has an oscillation frequency ranging from a few hertz to several thousand hertz or more, which seriously threatens the stable operation of power grids. This paper summarizes the wide-band oscillation events that occur worldwide under the background of renewable energy access to power grids, classifies the wide-band oscillation events according to the distribution of oscillation frequency bands, and sorts out the characteristics of various oscillations. From the perspectives of the source side and network side, the existing oscillation suppression measures are classified and prospected. [ABSTRACT FROM AUTHOR]

The deep integration of power grids and communication networks is the basis for realizing the complete observability and controllability of power grids. The communication node or link is always built according to the physical nodes. This step is alternatively known as "designing with the same power tower". However, the communication networks do not form a "one-to-one correspondence" relationship with the power physical network. The existing theory cannot be applied to guide the practical power grid planning. In this paper, a local evolution model of a communication network based on the physical power grid topology is proposed in terms of reconnection probabilities. Firstly, the construction and upgrading of information nodes and links are modeled by the reconnection probabilities. Then, the power flow entropy is employed to identify whether the power cyber-physical system (CPS) is at the self-organized state, indicating the high probability of cascading failures. In addition, on the basis of the cascading failure propagation model of the partially dependent power CPS, operation reliabilities of the power CPS are compared with different reconnection probabilities using the cumulative probability of load loss as the reliable index. In the end, a practical provincial power grid is analyzed as an example. It is shown that the ability of the power CPS to resist cascading failures can be improved by the local growth evolution model of the communication networks. The ability is greater when the probability of reconnection is p = 0.06. By updating or constructing new links, the change in power flow entropy can be effectively reduced. [ABSTRACT FROM AUTHOR]

With the increase in capacitor voltage transformer (CVT) operation life, CVT impedance changes, and the short-time switching of overhead lines, it is very easy to cause a transient oscillation accident in which a CVT participates, reduce the insulation level of a CVT, and even induce regional power grid oscillation and easily cause capacitor breakdown, after long-term operation with defects. In this paper, the whole power network, including the generator, power grid, and consumer, is modeled, and the theoretical model of the CVT ferro-resonance connected grid is built. The frequency spectrum analysis, and the measurements of resonance bus voltage and line voltage, were carried out to find the design method of a fast saturation damper (FSD) and its voltage–current characteristics that affect the vibration, based on theory and practice; this paper puts forward effective measures to reduce the resonance effect of a CVT in operation, and avoid the oscillation of the line and even the regional power grid system. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive droop control (ADC) strategy for the voltage source converter (VSC) based multiterminal high voltage direct current (VSC-MTDC) system, which enables the VSC-station to provide frequency regulation for onshore ac grids. A V-I-f characteristic is derived to establish the relationship between the frequency deviation and dc voltage. A VSC-station working with the V-I-f characteristic is able to adjust its dc voltage reference autonomously according to the grid frequency deviation. Thus, the power flow of the VSC-MTDC system will be redistributed and more power is going to be injected into the adjacent grid of which the frequency deviation exceeds the threshold value. The ADC strategy inherits the advantage of the traditional droop control (TDC) that there is no need for communication system. An ac/dc hybrid system that includes VSC-MTDC system, onshore grids, and offshore wind farms is built in DIgSILENT/Powerfactory. Modal analysis and nonlinear simulations are performed to obtain the optimal control parameters and demonstrate the performance of the ADC strategy. [ABSTRACT FROM AUTHOR]