Research on Self-adaptive Network Partitioning Algorithm for Electromagnetic Transient Parallel Simulation of Power System

three kinds of digital programs used in power system simulation are summarized in this paper. The electromagnetic and electromechanical transient simulation software ADPSS is introduced. Electromagnetic transient simulation, electromechanical transient simulation and electromagnetic-electromechanical transient hybrid simulation are performed respectively on Deyang-Baoji ±500KV HVDC system. The simulation result shows that the electromagnetic-electromechanical transient hybrid simulation has the advantage of electromagnetic transient simulation and electromechanical transient simulation. It can effectively analyze the process of the local electromagnetic transient in large-scale grid. The simulation speed is fast and the result is accurate and reliable.

Most transient stability programs can solve very large systems but the representation of individual components of the system, in particular power electronic devices and control systems associated with FACTS and HVDC transmission systems cannot be represented in detail. Electromagnetic transients simulators, on the other hand, can represent system components and control systems in great detail, but are impracticable for the simulation of very large systems, and dynamic equivalents are required. It is apparent that the future of simulation lies in the development of hybrid simulators, which would allow practicable simulation of large-scale power systems with embedded modeling on power electronic devices in devices level. In this paper, an attempt has been made to incorporate an electromagnetic transient model of a static VAr compensator (SVC) into the traditional transient stability simulation program.

Power system simulations are roughly classified into the two categories, effective-value-based simulations and electromagnetic transient simulations. The former are usually long-term simulations of a large power system considering the electro-mechanical dynamics and include for instance transient stability simulations. On the other hand, the latter are basically short-term simulations of a small portion of a power system, and surge simulations and power-quality simulations are included. However, for simulations which contain power-electronics controllers, electromagnetic transient simulation methods are often used even for long-term simulations.This paper first reviews various programs for electromagnetic transient simulations, and then the recent trend of related simulation techniques is summarized.

With the interconnection of regional grids and the increasing penetration of renewable energy, the order of the power system model is getting higher and higher, which brings great challenges to the accuracy and real‐time performance of electromagnetic transient (EMT) simulation. The simulation of power systems with a high proportion of renewable energy requires a sharp increase in the performance of the hardware platform and the parallelism of the simulation algorithm. To solve this problem, the paper proposes a fine‐grained parallel modelling method for power systems with a high proportion of renewable energy, which is inspired by the latency insertion method used in the design of large‐scale integrated circuits. And this method is implemented on GPU to achieve the component‐level and device‐level parallelized simulation of power systems with a high proportion of renewable energy. Finally, the correctness of the proposed algorithm and the CPU‐GPU cooperative architecture is verified based on an improved 118‐bus case. The cascade system of the improved 9‐bus case is used as an example to verify the superiority of the proposed algorithm in terms of simulation efficiency.

When conducting system-level research, it is unacceptable to adopt a detailed MMC electromagnetic transient model to bring about the amount of calculation. Although the use of electromechanical transient simulation and electromagnetic transient hybrid simulation technology or electromagnetic transient and dynamic phasor hybrid simulation technology can retain high simulation accuracy, it is not conducive to the model mechanism analysis and the control operation. In addition, the MMC average model is also used for AC and DC transient simulation. The average modeling uses controlled power sources to describe the average response of the converter, which can also be employed to the transient simulation. Due to the modeling properties of the ABC coordinate system, the average model is only suitable for time-domain simulation. The dynamic phasor modeling method employs the d−q axis coordinate system to analyze the MMC steady-state and research the small-signal stability. The order of each component in the d−q axis coordinate system model can be selected according to the required accuracy. Thus, the MMC dynamic phasor modeling scheme has widespread application in MMC-HVDC stability research, electromechanical transient simulation and controller design, etc. This article will establish an MMC dynamic phasor model to analyze the dynamic characteristics of system circulation.

This study presents a method to interface an electromagnetic transient (EMT) simulator with a dynamic phasor (DP) simulation program. The hybrid DP–EMT simulator offers flexibility in deciding the harmonic contents to be preserved in the DP domain; additionally, it offers significant reduction in computing time of large networks compared with EMT simulation. The proposed interfacing method is based on a generic transmission line, which uses specialised numerical techniques to transfer discretised waveform samples between the two simulators. These numerical methods produce the required mapping between EMT simulation samples and their counterpart DPs. This study describes the mathematical foundations of the DP–EMT interface and demonstrates them using an illustrative example. Several large networks are then studied to assess the interface's accuracy and performance in reducing computing time.

Shifted-frequency based electromagnetic transient simulation for power system dynamics using two-stage singly diagonally implicit Runge–Kutta method

As more generators and loads are integrated by power electronic converters with complicated controls, electromagnetic transients (EMTs) simulation becomes an important tool for studying dynamic characteristics of large‐scale power systems. To accelerate system‐level EMT simulations, a fine‐grained parallel algorithm on graphics processing units (GPU) is proposed. By decomposing the computational models of the EMT simulation into heterogeneous, homogeneous and network solution computations, the simulations are mapped into three unified GPU kernels. To incorporate control signals and non‐linear features of electrical components, heterogeneous computations are formulated as layered direct acyclic graphs (LDAG) of primitive operations. An LDAG kernel is designed to carry out theses primitive operations efficiently by grouped threads. Then, homogeneous computations for state updates of electrical components are modelled as sets of fused multiply‐add (FMA) operations, which are concurrently processed by an FMA kernel. Moreover, a hybrid network solution kernel is designed to solve the network equations, which can adaptively select dense or sparse solvers. Large‐scale test systems are created and simulated on an NVIDIA K20x GPU. The results show that the proposed GPU‐based EMT simulations are accurate and achieve 10x speedups over the CPU‐based ones.

An aggregation method is proposed that transforms the multiple DFIGs into an equivalent DFIG model that retains the major collective dynamic characteristics of a group of DFIGs. It is intended for Electromagnetic Transients Simulation (EMT). The aggregated machine can take into account different speeds and parameters of each of the individual DFIGs and the connecting impedance of individual DFIGs. Starting with a State Variable (SV) model of an individual DFIG, aggregation is carried out recursively, by combining two DFIGs at a time and then reducing the order of the aggregate to match the state variable equations of a single DFIG so that the steady state performances are identical. Validation is carried out by comparing the detailed electromagnetic transient (EMT) simulation of the unreduced system with the reduced aggregate system. It is shown that the proposed aggregation method accurately matches the steady state response and also accurately reproduces the dominant transient response of the unreduced system. As the aggregate DFIG has the same number of state variables as a single DFIG, the overall wind farms order is reduced significantly to increase the modelling and simulation efficiency.

At present, in the simulation of large-scale AC/DC systems, electromechanical transient simulation cannot accurately describe the dynamic characteristics of the system due to the limitations of its models and parameters. And the traditional electromagnetic transient simulation lacks accuracy and real-time in the simulation analysis due to the limitation of simulation speed. Therefore, it is necessary to propose an accurate electromagnetic transient real-time simulation method. Based on the BPA dynamic equivalent data of the East China AC/DC power grid, this paper establishes a real-time simulation model of the multi-feed DC power system in HYPERSIM. First, the accurate converter valve module of the DC system is modeled to reflect the characteristics of the converter valve more accurately while ensuring the simulation speed. After that, the modeling method of the generator, load and other modules is given. Simulative results show that the steady-state and transient characteristics of the system are consistent before and after the conversion, which verifies the validity of the proposed modeling method. The research results give reference for the accurate simulation of large-scale multi-feed DC projects in the future.

An automatic grid partitioning technique of large grids based on CloudPSS

Summary form only given. Real time electromagnetic transients simulation of power systems has primarily three applications: closed loop testing of control systems for HVDC and FACTS apparatus; closed loop testing of AC protection and control systems; and electromagnetic transients simulation for larger systems. The presentation includes details on the fully digital simulation of a transmission system including a TCSC. Some details are also provided for the case of simulating a transmission system interfaced to an analog SVC model. Advances in digital real time electromagnetic transients simulation are also described including high resolution firing accuracy and on-line matrix decomposition.

In this paper electromagnetic transient (EMT) simulation of large scale power systems using graphics processing unit (GPU) based computing is demonstrated. As the size of power system networks increases, the simulation time using conventional central processing units (CPUs) based simulation increases drastically. This paper proposes a hybrid CPU-GPU environment for fast large scale power systems simulation. In this scheme the GPU is mainly deployed to perform the computationally intensive part of the simulation in parallel on its built-in multiple processing cores, and the CPU is assigned for other sequential jobs like flow control of the simulation and storing output data, etc. The GPU-based approach is used to simulate a network with 900 Buses, and it is shown that the CPU-GPU based implementation is 70 times faster than the conventional CPU-based implementations.

For the power system with a large number of power electronic equipment, the traditional electromagnetic transient real-time simulator is difficult to achieve small step simulation. To solve this problem, a power system transient real-time simulator is built by adopting a power system multi-rate real-time simulation method based on field programmable gate array (FPGA) and CPU. Taking the photovoltaic power generation system as an example, the system is divided into a large step part and a small step part by adopting a model partition method, and the asynchronous communication between FPGA and CPU is realized through Ethernet to form a large step-small step multi-rate co-simulation platform. For the error problem caused by the system data interaction after model partition, a PWM equivalent averaging method is proposed to equalize the output voltage at the AC side of the inverter, so as to reduce the error and compare the consumption of the equalized hardware resource. Finally, by comparing with the simulation results of the Simulink offline model, the experimental results have verified the effectiveness and accuracy of the method in real-time simulation of the power system.

This paper introduces a new method of modeling microcontroller-based systems in a non-real-time electromagnetic transient (EMT) simulation. Presently, power electronic control system simulation relies chiefly on either simplified control block models in a non-real-time simulator or real-time hardware-in-loop simulation. Migrating control block models from the simulated design to actual microcontroller hardware requires significant additional effort. Real-time hardware-in-loop simulation requires complex interfacing using costly real-time hardware. The method described in this paper replaces control system blocks in non-real-time simulation with actual microcontroller code. The method enables both software-in-loop simulation and processor-in-loop co-simulation, eliminates the drawbacks of the simulation methods described above, and allows direct optimization of the actual controller hardware. The method is demonstrated by simulations of a three-phase ac motor controller in both software-and processor-in-loop configurations. The simulations are verified by laboratory results obtained using the tuned microcontroller hardware to implement a control system for a 3-phase ac motor.