Efficient transient simulation of large power grid is of great importance for system operation and dispatching, fault repetition, operator training etc. Online stability estimation and testing on system control and protection require hard real-time performance of transient simulation. The conventional real-time simulation, which splits an entire grid into sub-grids and solves them in parallel, lacks generality for various case systems. This study proposes a new efficiency enhancement method without grid partitioning. Three key techniques are involved. First, parallel solving format is proposed to distribute two-layer computational burdens into central processing unit cores in balance. Second, to calculate the fault changing the grid structure, the inverse current compensation is employed instead of re-forming impedance matrix and repeating lower-upper (LU) decomposition. Third, dual-loop forward and backward substitutions to solve grid equations are modified to a single-loop iteration, which further improves the computational efficiency. At last, the validity and effectiveness of the proposed method are verified by tests.

Based on the SMRT (simulation mixed real-time) including parallel computer and RTDS electromagnetic transient/electromechanical transient hybrid real-time simulation platform, this paper presents a three sequence current injection method in the hybrid real-time simulation interface for dealing with the asymmetric faults. Furthermore, the automatic calibration method for the three sequence initial power at the electromagnetic transient side is also presented. Thus, all the three sequence currents and voltages could be exchanged between electromagnetic transient simulation and electromechanical transient simulation. As a result, the asymmetric fault simulation function is realized in the SMRT hybrid real-time simulation platform. It is shown that the simulation results of SMRT hybrid real-time simulation platform are similar to those of RTDS.

Aiming at the difficulties in hybrid real-time simulation with AC/AC partitioning and utilization needs, an AC/AC partitio-ning scheme with mapping sub-grid is proposed to maintain the complete three-sequence girds of the AC power system and the synchro-nization of the whole AC system. Key techniques, such as mapping sub-grid based interface equivalent modelling and mapping relation based estimation and correction, are given to ensure a stable interactive computation and smooth interface between electromagnetic and electromechanical transient sides. Cases tests prove the validity and practicality of the proposed scheme. Comparing the simulation re-sults with the AC/DC partitioning scheme, the high-frequency transient phenomenon in the AC and DC ( or power electronic equip-ment) systems can be simulated more accurately with the mapping based AC/AC partitioning scheme.

Based on super mixed real-time simulation ( SMRT) , which interfaces real-time digital simulation ( RTDS) and digital com-puter, this paper presents the architecture design and basic implementation, and the difficulties and key techniques for utilization of hy-brid simulation in AC and DC power system. Key techniques on how to smoothly interface the electromagnetic and electromechanical tran-sient simulation modes are studied and described in detail, including stability analysis and stabilizing method for the computational sys-tem. practical equivalent interface impedance in low frequency band, leading estimation of interface states based interface and interaction protocol, asymmetric interface method by three-sequence current injection, and three-sequence fundamental power calculation with close-loop auto calibration correction. Finally, the overall scheme and key techniques are verified by case analysis. More tests and practices have proven that SMRT basically meets the requirement of synthesis transient processes simulation of large AC and DC power system.

In order to correctly assess the practicability of the super mixed real-time simulation ( SMRT) platform, the key perform-ance of SMRT is tested in this paper. Firstly, the calculation model of 2013 flood-season heavy-load operation schedule in CSG is es-tablished on the SMRT platform, and SMRT simulation results, BPA simulation results and PMU/TFR records are quantitatively com-pared by simulation error evaluation criteria to evaluate the correctness of the SMRT simulation. Secondly, a time-consuming test is carried out on SMRT during steady state and transient process to verify the real-time performance of the SMRT simulation. Finally, the convenience of SMRT platform is objectively evaluated. The comprehensive evaluation results show that SMRT platform has higher simulation credibility and feasibility.

Series-connected insulated-gate bipolar transistor(IGBT) valves provide the unified power quality conditioner(UPQC) converters with compact structure and easy control. Its key technologies include dynamic voltage balancing of series-connected IGBTs and on-load testing method for the converter. This paper takes use of active voltage clamping method to achieve the dynamic balance of series-connected devices. And, to implement the on-load testing of the UPQC converters, one side converter acts as a power supply and the other side as a load. By this way, the effectiveness of the UPQC converters based on series-connected IGBT valves is verified.

For large power grid with plentiful serial branches of large resistance-reactance ratio,a fast power flow calculation method is proposed and realized,which builds the iterative modification equation based on the linear power-voltage equation and the initial iterative value is calculated using the PQ method based on the continuation of branch resistance-reactance ratio.An accelerating convergence factor is added to the iterative process to ensure the convergence and solving accuracy.Its voltage modification direction is simple and clear,suitable for programming.The power flow calculations for a small system case and the practical Southern Grid show that,the proposed method is of high accuracy and good adaptability.

Recently, the electromagnetic and electromechanical hybrid simulation is gradually practiced to engineering in analysis of large AC/HVDC power systems. Interface models are one of the most important interface techniques determining accuracy and applicability. Nevertheless, the limitations of traditional interface models emerge and become concrete. This paper develops interface computational equivalent power source models of EMT subsystem and interface fundamental equivalent current related ideal voltage source model of TS subsystem. Also, case studies are carried out to quantitatively present the improvements and visually prove the necessity and efficiency.

Series connection of IGBTs is applied to increase the voltage rating of converters. The critical issue is to balance the dynamic voltage of each device in the series string. This paper investigates an auxiliary circuit as a solution involving slope regulating and voltage clamping. It adjusts the Miller capacitance and gate current with additional capacitors and feedback current from collector to gate, by which the gate voltage and then the collector-emitter voltage are controlled. Consequently, the differences between block voltages of IGBTs are restrained. A 15 kV test rig is established and experiments are carried out successfully based on up to sixteen 1.7 kV/800 A IGBTs in series connection. It is proved that the proposed circuit has no limitation to the number of series connected devices and is simple, reliable and low-cost.

This paper presents a novel hybrid simulator,in which the digital computer and RTDS carry out the electromechanical and electromagnetic transient simulation,respectively. The overall design is proposed and the key techniques are studied in detail,including the interaction process between the two sides and the flow of synchronous simulation,the interface scheme for hybrid simulation,and the method for interface data exchange. A case study of the actual AC and DC hybrid power system containing the Gui-Guang HVDC system of China Southern Power Grid testifies to the practicability and validity of the overall design and the implementation of the hybrid simulator.

For power system simulation, the contradiction between the computational efficiency and the system scale as well as the detailed modeling comes into being. The electromagnetic/electromechanical hybrid simulation technology has been thereupon proposed. In this paper, a novel real-time hybrid simulator, which is based on two personal computers (PCs) and an analog communication device for data exchange between two PCs, is designed and built, and the key techniques are studied. For the unsolved essential difficulties in hybrid simulation technology, this paper initially studies the forecasting and correction method. The case studies not only indicate that the hybrid simulator is a success, but also testify to the practicability and necessity of the forecasting and correction method. All the achievements have paved the way for the forthcoming studies on the original hybrid simulator based on digital computers and real-time digital simulator (RTDS).

Impact loads require STATCOM to have fast and robust performances. Based on the analysis of mathematic model, a decoupling control method of STATCOM is investigated in this paper. This method is implemented in two industrial STATCOMs and presents satisfied control capabilities. The compensated PCCs of impact loads obtain significant improvements of power quality.

The authors conduct the real-time interface of electromechanical transient simulation with electromagnetic transient simulation, so in a once-through simulation the electromechanical transient simulation of large-scale power grid and the electromagnetic transient simulation of partial power network can by simultaneously implemented. Besides, a hybrid real-time simulation platform composed by digital computer and real-time digital simulator (RTDS) is designed; the key techniques of this platform are researched, mainly including how to build equivalent circuit of the opposite system and how to interchange data between the two simulation subsystems. New thinking to solve relevant problems are put forward the equivalent module should rightly reflect the status of the opposite system and simplify the lesser important factor.

The tremendous developments of power systems bring new challenge to the simulation technology and conventional transient simulation cannot meet the analytical needs of practical large-scale power systems.Combining the advantages of electromagnetic and electromechanical transient simulations, experts and scholars have proposed the hybrid simulation technology.This paper gives an overview on the research and development of the hybrid simulation at home and abroad.Then two fundamental requirements for engineering applications are specified and several essential difficulties are described,including the system segmentation scheme,the boundary condition for the calculation of one side and equivalence of the other side,and the interactive order of two sides during the system fault.Based on the analysis of these difficulties,a forecast and correction method is proposed,with its feasibility expounded.Finally,the paper makes a simple comment on the development trends of the hybrid simulation.

Based on electromechanical transient calculation, a real-time electromechanical simulation system for power grid is developed. The constitution of each part of this simulation system, its working principle and the interface concerned in the implementation of simulation are researched. By means of two simulators for power system excitation and protective relaying, the functions of the proposed simulation system are tested, and the correctness of real-time simulation results by the proposed system is validated. The proposed simulation system can satisfy the requirement of real-time performance.

The simulation system based on field data of the electric arc fumace(EAF)system with its compensation scheme is presented.The EAF model is built with recorded field data with the supply system,which can really reflect the characteristic of the EAF system.When the EAF is operating without any compensation device,it causes power quality problems,such as harmonics,unbalance,voltage fluctuation and flicker.In order to solve these problems,the compensation scheme is proposed for the load compensation using distribution static synchronous compensator(DSTATCOM)and passive power filter.The power filter is adapted to mitigate the total harmonic distortion(THD)of the connection bus voltage and supply part of reactive power,while the multilevel H-bridges DSTATCOM with instantaneous current control is designed to compensate the load unbalance,bus voltage fluctuation and flicker.Finally,the EAF simulation system is built in PSCAD/EMTDC and the simulation results are presented to illustrate the effectiveness of the proposed scheme.

作为工程类传统专业课,电力系统本科专业课中大部分是成熟知识点。如何提高传统工程专业课的研究性是富有挑战性的共性课题。通过对电力系统本科专业课的教学改革,形成了一套较完整的研究型教学模式,包括:课内的研究型授课方法、课外的自选研究专题、数字化实验平台和研究型实验等系列内容,涉及理论课、实验课和实验基地三大方面,有效加强了课程的研究性。本项改革成果已实践了3年,所研制的数字化实验平台已在多所大学推广应用,人才培养效益显著,在全国同行中产生了重要的影响力。

To know the dynamics and modes of interest about a power system is prerequisite for designing effective damping controllers,and model identification is a usual way to achieve it,since a complete description of a large power system is often unfeasible and unnecessary.A practical solution of reduced-order model identification was proposed in this paper,which applied ERA(eigensystem realization algorithm) and model reduction methods to power system research.Improvements were brought to original ERA to meet the specific demands for designing damping control while retaining its advantage in computational efficiency and easy handling of MIMO systems.Validity of the solution was checked in models of various scales and characteristics,and the test results show that the proposed solution can yield state space models that are appropriate in both accuracy and order.Problems encountered in non-linear MIMO systems were also discussed.

The objective of this paper is to present the compensation scheme for electric arc furnace (EAF) in three-phase three-wire distribution supply system of China. The use of recorded field data to build the EAF model in supply system can really reflect the power quality problems in the EAF system. Firstly, the typical supply system for the EAF of China is introduced. When the EAF is operating in the system without compensation device, it causes power quality problems, such as harmonics, unbalance, voltage fluctuation and flicker. The recorded field data of a steel works at the 35kV bus is used to explain the power quality problems. In order to solve the problems, the compensation scheme is designed for the EAF compensation using static synchronous compensator (DSTATCOM) and passive power filter. The passive power filter is used to mitigate the total harmonic distortion (THD) of the connection bus voltage and supply part of reactive power. Using the transformer-isolated multilevel H-bridges inverter with the instantaneous current control scheme, the DSTATCOM is capable to mitigate the unbalance and voltage fluctuation of the EAF system. Accordingly, the EAF model is built as a current source using the recorded field data with the supply system in EMTDC/PSCAD. With the compensation devices, simulation is done to test the compensation scheme and the results are presented to illustrate the effectiveness of the proposed scheme.

一、背景 多年来,清华大学电力系统本科专业课是面向电气工程一级学科的专业必修课,由四门理论课(电力系统稳态分析、暂态分析、稳定性和继电保护)和一门实验课(电力系统实验)组成,是本科生进入电力系统专业科学殿堂的主要向导和桥梁.