Electromagnetic transient (EMT) and transient stability hybrid simulations are predominantly used to analyze the interactions between HVDC systems and the AC grids accurately and efficiently. However, the dynamics of the converters will be affected by the waveforms of adjacent AC systems greatly. Waveform distortion as well as time delay caused by interfacing would significantly increase interface errors, resulting in the decrease of the overall accuracy of the simulations. To resolve such problems, a dynamic phasor based interface model (DPIM) is proposed in this paper to improve the accuracy of interfaces, especially when the fault occurs near the converters. In doing so, the whole system is partitioned into three parts: the transient stability (TS) subsystem, the EMT subsystem, and the DPIM. During each iteration, the interfaces between the TS subsystem and DPIM are represented by their Norton equivalents at fundamental frequency and Thevenin equivalents in the dynamic phasor form. Similarly, the interfaces between DPIM and EMT subsystems are represented by their three phase Norton equivalents and Thevenin equivalents in dynamic phasors, respectively. The effectiveness of the proposed method in terms of accuracy and efficiency is validated by simulating a practical HVDC Project.

VSC-HVDC (Voltage Source Converter High Voltage Direct Current) transmission system is a recent HVDC technology. The paper presents a new way of VSC-HVDC electromechanical transient modeling and simulation, which is based on the theory of equivalent sources. This method uses equivalent sources to substitute for voltage source converter, in addition, there are no simulation of IGBTs or PWM trigger modular, so it is more appropriate for electromechanical transient modeling and simulation. By this way, the detailed dynamic model for VSC-HVCD is developed. This model includes four parts, i.e. the normal ac system, the VSC-HVDC inner dc system, the interface between ac and dc system and the VSC-HVDC control system. Then a case of VSC-HVDC transmission system is established in PSCAD, the results show that by using this method for VSC-HVDC electromechanical transient modeling and simulation, not only the steady-state power flow can be controlled, but the system can achieve ideal dynamic response.

As the large-scale integration of photovoltaic (PV) power station, a higher requirement is put forward by power grid analysis on the accuracy of PV station model. For the model of photovoltaic system is complex, and it requires solving large-scale model equation, which is not conductive for simulation and big data analysis when a large-scale PV power station connected to grid. This paper focuses on the same type of photovoltaic power generation, assuming that the photovoltaic power plant is composed of multiple photovoltaic power generation units connected by the collector line, the photovoltaic power plant can be modeled to consider the operation of similar power generation unit grouped together, so that reduce the simulation scale. This paper points out that the dynamic clustering equivalence strategy can be classified into two cases. During the fault and fault-over, the transient condition is required to be grouped when the active power ramp recovery control module is operating, and the another single-unit equivalent model can be performed when the module is ignoring or not running into a non-fault condition, which is the second condition. Simulation results show that the proposed method has good adaptability for irradiance disturbance, different fault time.

Energy storage batteries can smooth the volatility of renewable energy sources. The operating conditions during power grid integration of renewable energy can affect the performance and failure risk of battery energy storage system (BESS). However, the current modeling of grid-connected BESS is overly simplistic, typically only considering state of charge (SOC) and power constraints. Detailed lithium (Li)-ion battery cell models are computationally intensive and impractical for real-time applications and may not be suitable for power grid operating conditions. Additionally, there is a lack of real-time batteries risk assessment frameworks. To address these issues, in this study, we establish a thermal-electric-performance (TEP) coupling model based on a multi-time scale BESS model, incorporating the electrical and thermal characteristics of Li-ion batteries along with their performance degradation to achieve detailed simulation of grid-connected BESS. Additionally, considering the operating characteristics of energy storage batteries and electrical and thermal abuse factors, we developed a battery pack operational risk model, which takes into account SOC and charge-discharge rate (Cr), using a modified failure rate to represent the BESS risk. By integrating detailed simulation of energy storage with predictive failure risk analysis, we obtained a detailed model for BESS risk analysis. This model offers a multi-time scale integrated simulation that spans month-level energy storage simulation times, day-level performance degradation, minute-scale failure rate, and second-level BESS characteristics. It offers a critical tool for the study of BESS. Finally, the performance and risk of energy storage batteries under three scenarios—microgrid energy storage, wind power smoothing, and power grid failure response—are simulated, achieving a real-time state-dependent operational risk analysis of the BESS.

The traditional reliability evaluation assesses the long-term performance of power system but its constant failure rate cannot reflect the time-varying performances in an operational time frame. This paper studies the operational reliability of power system in the real-time operating conditions based on online operation information obtained from the Energy Management System (EMS). A framework of operational reliability evaluation is proposed systematically. The effects of components' inherence conditions, environment conditions and operating electrical conditions on failure rates are considered in their operational reliability models. To meet the restrictive requirement of real-time evaluation, a special algorithm is presented. The indices for operational reliability are defined as well. The software, Operational Reliability Evaluation Tools (ORET), is developed to implement the above described functions. The work reported in this paper can be used to assess the system risk in an operational timeframe and give warnings when the system reliability is low.

A large number of blackouts have happened in power system recently, and most of them are cascading outages. Because of their severe consequences, a variety of methods are proposed to study the mechanism of cascading outages. These methods can be divided into four categories: self-organized critical theory, complex network theory, operational reliability theory, and power system simulation theory. This article reviewed the researches on cascading outages, and pointed out some important research achievements and their drawbacks.