To reduce the amount of discarded hydropower of Yunnan Power Grid during flood season, a feasibility study on interconnection between Yunnan Power Grid and Guizhou Power Grid is conducted by China Southern Power Grid. For the above research requirements, interaction analysis and suppression technology of sub-synchronous resonance/oscillation (SSR/SSO) in the AC-DC power grid with thermal power units, fixed series compensations and HVDC transmission system are carried out. Firstly, the frequencies of the SSR/SSO in AC system, which may be caused by the three types of above-mentioned equipment respectively, are theoretically calculated and analyzed, then the possible three types of SSR/SSO modes and their dominant sources are obtained comprehensively, which are verified through the EMTDC fault time domain simulation and comparative analysis. Further, from the perspective of HVDC additional control, an improved design method of DC sub-synchronous damping controller (SSDC) is proposed according to the characteristics and distribution of the SSR/SSO modes in the power grid. The results of the fault time domain simulation in EMTDC with a new SSDC designed using the above method prove the correctness and effectiveness of the method.

The power transmission ability of a same converter can be expanded by improving the current utilization ratio of switching devices of modular multilevel converter based HVDC (MMC-HVDC), and hence the cost of converter of MMC-HVDC can be reduced. Based on the characteristics of MMC, this paper presents a new type of circulating current control strategy considering double frequency harmonic current injected, and gives mathematical deduction of amplitude and phase of the double frequency sinusoidal harmonic current injected. This new strategy can reduce the peak value of the arm current up to 20%, improve the current utilization rate of the converter, and enhance the power delivery capacity of the converter up to 25%. At last, the simulation model of MMC is established in RTLAB, and the new circulating current suppression strategy is carried out. The simulation results verify the accuracy and effectiveness of the proposed control strategy.

A method to simulate the transient process of interturn short-circuit fault of converter transformer based on field-circuit coupling mthod is presented, which can effectively solve the complex electromagnetic problems in the process of short-circuit fault, and obtain the short-circuit current waveforms of line ends and windings in the process of fault. An interturn short circuit case in a converter transformer is used for simulation calculation, the occurrence of short circuit fault is simulated by setting the switch closing time in the external circuit, and the fault current waveform at the line end is obtained by combining the system parameters and the initial phase angle of the fault time. The calculated waveform is basically in agreement with the actual fault recording waveform, which verifies the hypothesis of fault development process and shows that the proposed method is applicable to the transient simulation of transformer interturn short-circuit fault.

By analyzing the power module level failure and protection logic of modular multilevel converter (MMC) systematically, the dynamic simulation scheme is proposed,the core of the scheme is to use the powerful operation ability of the RTDS processor to send the fault setting information and firing control words to FPGA dynamically in every small step (<2.5 μs) through high-speed optical fiber communication. This scheme is suitable for real-time Hardware in Loop (HIL) simulation system consisting of the control and protection devices. It can not only realize dynamic simulation of power module fault and protection in microseconds but also realize dynamic simulation of multiple faults. Finally, aiming at MMC-HVDC unit tripping accident of China Southern Power Grid by single power module fault, the simulation model is established based on the proposed scheme and accident reappearance test is conducted, the simulation results show that the proposed scheme is effective.

Aiming at the initial energy storage capacity optimization of SMES-FCL for suppressing the fluctuation of wind power output and improving low voltage ride through(LVRT) performance, integrated configuration of SMES-FCL used in doubly fed induction generator(DFIG) integrated system is studied from the perspective of stable operation and economical efficiency. The evaluation index of DFIG’s LVRT capability is presented, economic costs is taken into account and the multi-objective optimization model of magnetic energy storage capacity is established. NSGA-II algorithm is used to solve the optimal magnet capacity that meets the research target. Comparing the performance with SMES,the simulation results show that SMES-FCL can improve the economy of superconducting magnet compared with SMES.

In order to ensure the reliable operation of the main protection of the high-voltage power grid, the protection channel, router configuration and channel alarm data source distribution of high-voltage power grid are analyzed, and a corelation analysis method based on multi-source data for protection channel anomaly positioning is proposed, which comprehensively utilizes relay protection fault information system and communication network management system. Dynamic information such as communication resource management and control system, maintenance system and EMS system are deeply explored. The time synchronization technology among multiple systems based on information fuzzy matching and the dynamic information association technology based on multi-source information fusion are studied, and the automatic alarm and fault location of the protection channel abnormal fault are realized. The ground fault disconnection assistance decision based on the channel anomaly is also provided. The analysis results of the example demonstrate the effectiveness and accuracy of the method.

In order to study the capability of power interchange among microgrids and the distribution network, firstly, an optimal model in microgrid control layer is proposed considering comprehensive cost and capability of power interchange, to predict power interchange feasible region of microgrids. The power interchange feasible region correction model in distribution network control layer is built based on the index of system stability margin, to evaluate the power interchange capability between multi-microgrids and distribution network. Then, the point estimation method (PEM) is introduced to construct the estimating points of random variables, and the microgrid optimal model is used which ensuring solution speed and covering plenty of uncertainties. Finally, the typical microgrid and distribution network test models are used to verify the correctness and feasibility of the proposed method. The evaluation results of the power interchange capability may provide reference for multi-microgrids participate demand response markets, coordinate power exchange capacity and fast reserve responsiveness to upper network.

The current domestic provincial power market transactions are still dominated by medium-term and long-term power trading, mainly including annual negotiation trading and monthly centralized trading. Monthly centralized trading is the last transaction window followed by power dispatch operations. The transaction and clearing mechanism design must fully consider power grid security and unit operation constraints in order to guarantee the feasibility of transaction results. Based on the design and practice of Guangdong monthly centralized trading, this paper concludes a method for determining and adjusting the maximum amount of electricity for various type of units, while considering the characteriscs of units such as combined heat and power units and gas power generation, the power plant load rate limit, and the minimum/maximum transaction limit of power plants. This paper also implements a series of mechanisms to deal with power plant group transaction limits and the impact of must-run units on centralized trading, including improved market clearing algorithm and must-run unit bidding price processing. The reasonable compatibility between the design of competitive transaction mechanism and the operational constraints of the grid has been achieved. Finally, the real case analysis of the operation of Guangdong power market proves the practicability of the proposed mechanism.

Big data technology is an efficient path to improve distribution network operation by mining hidden value of distribution and consumption integrated data. This paper presents a method for establishing a distribution network operating analysis platform. Based on analysis of data sources and data types which consist of big data in smart power distribution and consumption systems, functional requirements for the platform are proposed, such as evaluation of distribution network scale, power distribution reliability, equipment running state and so on. The platform’s architecture is proposed and developed including four layers: business, application, data center and data base. By means of analyzing, identifying and mining of multi-source data and visualization technology, the integration of data of power network, equipment and environment is realized and big data analytics results can be shown by whole picture. On the platform, some typical applications have been developed such as distribution network fault analysis.