A simplified model of Type‐4 wind turbine for short‐circuit currents simulation analysis

Abstract

The electromagnetic transient (EMT) model of Type 4 wind turbine generator (WTG) requires a small simulation step, and cannot be simplified based on Thevenin-Norton theorem, which results in the low simulation efficiency of large-scale Type 4 WTG-based wind power plants (WPPs) widely connected to the power grid, bringing challenges to the short-circuit currents analysis in the research of protection. Therefore, in order to solve the problem of low simulation efficiency, a simplified model of Type 4 WTG is proposed based on the principle of internal active power balance of Type 4 WTG. The simplified model is represented by controlled voltage source, which eliminates the power electronic switch and DC-link, greatly simplifies the typical EMT model of Type 4 WTG, and does not require small simulation step. The simplified model has simple modelling process and high universality of modelling method. The simulation results show that the proposed model can accurately reflect the EMT characteristics of Type 4 WTG under fault. Compared with the typical EMT model, the simulation time of this simplified model is significantly reduced, and the EMT simulation efficiency of the power grid connecting with large-scale Type 4 WTG-based WPPs has been effectively improved.

A state‐space average model of a three‐level PV inverter for transient short‐circuit currents analysis

“…According to Equation (3), i np = 0 and the two capacitors are in series. Thus the current equation of this case is the same as Equation (2).…”

“…Since the voltages of the two capacitors u DC1 and u DC2 are in balance, we can get Equation (5). Substituting Equation ( 5) into Equation ( 4) we can get the same current equation as Equation (2). Another equivalent circuit of vector III is shown as Figure 5b.…”

“…Short-circuit faults are most common faults in power systems. In some serious circumstances, a short-circuit fault may cause power stations to be disconnected from a grid [1][2][3], DC systems to be locked [4,5], even leads to serious large area power outage, bringing significant economic losses. This is because, on one hand, the quasi-steady state short-circuit current of a power system may be larger than the endurance capabilities of electrical equipment like transformer, circuit breaker etc., and as a result, the electrical devices are damaged and the power system fails to operate safely.…”

Operational resilience metrics for power systems with penetration of renewable resources

“…A full-converter wind turbine generator (WTG) is modelled to represent the wind power generation, whose modular structure connected to grid system is shown in Figure 5. The WTGs are connected to the system via back-to-back converters at generation buses [30,31]. And the scaling component is used to increase power level of WTG to model equivalent wind farm.…”