By the end of 2017, the proportion of European offshore wind power installed capacity in the world reached 81.7%. Offshore wind power technology has changed from demonstration stage to more extensive commercialization, which is closely related to the gradual improvement of offshore wind power standardization. This paper briefly reviews the development process of offshore wind power standardization in Europe, and introduces in detail the experiences of the developed countries such as Denmark, Germany, Britain and so on. By comparing the emphases of the above mentioned countries, combining with the implementation degree of standardization in this field in China, the paper analyzes the significance of European offshore wind power development experience to the standardization of offshore wind power in China, and combines the actual situation of our country the relevant enlightenment and suggestion are put forward. In the development of offshore wind power standardization, it should be paid attention to establish local characteristic standards and cooperate with innovation, further improve the inspection certification system and cross-departmental cooperation mechanism, and actively participate in the formulation of international standards.

With the increasing proportion of renewable energy represented by wind power and photovoltaic power, the inter-mittence and strong volatility of renewable energy bring many challenges to the safe and stable operation of the power system. In present stage, configuration principle and method of the energy storage battery capacity is one of the problems in practical energy storage engineering constructions. In this paper, smooth new energy grid power fluctuations is taked as the goal, combined with the local wind and light resources, renewable energy power is decomposed and frequency domain information is obtained by discrete Fourier transformation. Battery energy is used to transfer the high-frequency volatility components, a battery energy storage capacity configuration method considering daily power is proposed. Analysis of historical monitoring data of a wind farm in Hami, Xinjiang province verifies the applicability of the proposed method. The results show the proposed method can scientifically configure energy storage capacity according to the grid-connected volatility of renewable energy output and ensure the continuous operation of energy storage, thus provides a guiding significance and practical value for the construction of battery energy storage engineering.

In the power generation system, the increase of wind power penetration rate will bring double economic influence, so it is a key step to determine the reasonable proportion of wind power integration in power planning. Based on the fact that coal-fired power is the main power supply structure in China, the estimation method of economic interval of wind power penetration rate is put forward. Under the premise of guaranteeing the supply of electric quantity, this method calculates the reasonable capacity interval of wind power at the economic level, considering the overall benefit level at the generation side after wind power being connected to the grid. Firstly, the main positive and negative factors that wind power integration brings are analyzed. Secondly, the calculation methods of energy saving, emission reduction benefit, investment cost, reserve capacity cost and peak cost are studied under different wind power penetration rate, and then the calculation method of comprehensive economic benefit is obtained. So, the calculation model of the economic zone of wind power penetration rate can be formed. Finally, through a specific example, the economic change of power generation system under different wind power penetration rate can be calculated. At the same time, the influence of different parameters of the power generation system on the economic zone of the wind power penetration rate is analyzed. The results show that improving the system flexibility and improving the economy of wind power are the keys to achieve the high proportion of wind power integration.

This paper proposes a joint expansion planning method for transmission network and energy storage considering the optimization of transmission network structure with wind farms. The set of uncertainties is used to characterize the random features related to load demand and the wind power output based on robust optimization. Considering the extreme conditions caused by wind farm output and load uncertainty, a self-adaptive min-max-min robust planning model is proposed to optimize the robust expansion planning scheme and structure scheme of transmission lines and energy storage. This paper proposes a decomposition algorithm based on the original section plane for the proposed model. The robust planning model is devided into master model and slave model, then the non-convex problem can be transformed to a mix integer liner programming problem, which can be solved by CPLEX directly. The proposed method is verified by simulation on an IEEE 24-node system, and the optimization results demonstrate the effectiveness of the proposed method.

In order to study the interaction between modular multilevel converter (MMC) and the complex power grid, an universal fast simulation model of MMC is proposed, which is generally applicable to various topologies. Firstly, by using controllable voltage source, ideal switch and diode to simulate the circuit structure of different topologies in various operating states, the universal simplified circuit for the arm is obtained, which can accurately simulate the dynamics characteristics and control bevavior of MMC. Secondly, by analytically calculating the dynamics averages of the arm after averaging the switching and modulation process of sub-modules, the dynamic solution of large-scale node admittance matrix can be avoided and the simulation efficiency can be significantly increased. Based on PSCAD/EMTDC, the accuracy and speed of the fast simulation model are verified. In the end, the key control strategies and DC protection of multi-terminal system are studied by using the MMC fast simulation model.

In recent years, along with the wide applications of the high voltage direct current (HVDC) technology based on modular multilevel converter (MMC), the broad-band oscillations related to the MMC have also been frequently observed and drawn a lot of attentions. Therefore, focusing on the existing Luxi VSC-HVDC transmission system which has been experiencing this kind of oscillations, which have been taken into account the actual configuration of the Luxi VSC-HVDC transmission system, and the wind-band coupling impedance model of the named system is derived. This model demonstrates the dynamic charateristics of each control loops and their impacts on the impedance characteristics. It also reflects the coupling effects of the harmonic components. The electro-magnetic model of the Luxi VSC-HVDC transmission system has also been implemented to obtain the impedance-against-frequency curve by disturbance-identification method. The comparison between the impedance-against-frequency curve and impedance model has also proven the consistence of both model from a few Hertz to 2 000 Hz.

Utilizing voltage source converter based high voltage direct current transmission is the future trend for large-scale long-distance wind farm integration. With the continuous operation of related projects, the control and protection technology for VSC-HVDC systems with wind farms has become the current research focus. Based on actual projects, this paper reviews the research achievements and development status of the VSC-HVDC system with wind farm integration from several aspects, such as system topology, steady state control, small disturbance stability, active frequency response, AC and DC coordinated operation and transient control. The technology difficulties of current projects are introduced, and the future direction of research is prospected.

Several serious accidents caused by subsynchronous oscillation (SSO) have occurred. In order to study the problem of subsynchronous oscillation, the impedance matrix and the characteristic equation are analyzed. By means of equivalent circuit, the physical meaning of the characteristic equation and impedance are analyzed from the view of impedance. Then, the eigenvalues of the oscillation mode of the system are estimated according to the frequency impedance curve. A quantitative analysis method based on the impedance model is proposed, and the deficiency of existing stability analysis methods based on impedance model is resolved. Finally, the practicability and effectiveness of the impedance stability analysis method are verified through simulation cases.

The influence of wind-photovoltaic hybrid farm’s intergration on the sub-synchronous oscillation of power system is studied in this paper. Firstly, the mathematical model of power system connected with wind-photovoltaic hybrid farm is established. And the trajectory of main oscillation mode change when the parameters change in wind-photovoltaic hybrid farm combined with the benchmark, these parameters are wind speed, intensity of illumination, output active power, wind/photovoltaic power ratio, DC/DC inverter MPPT control parameter, inner ring control parameter of d and q axis currents of converter at grid side, inductance of filter lines, phase-locked loop control parameter and etc. It is found that wind-photovoltaic hybrid farm’s intergration almost does not affect the sub-synchronous oscillation modes associated with synchronous generators’ shafting. However, the variation of wind-photovoltaic hybrid farm’s parameters may lead to the instability of the sub-synchronous oscillation mode associated with the wind-photovoltaic hybrid farm. Sub-synchronous damping controller attached to the grid-side converter of wind-photovoltaic hybrid farm can improve the damping of power system and suppress the sub-synchronous oscillation. And the results of modal analysis and nonlinear simulation verify the effectiveness of the sub-synchronous damping controller.

Modular multilevel converter (MMC) consists of a large number of sub-modules (SMs), the operation of which, has direct influence on the total converter substation. So research on the fault characteristic, fast detection and location of the sub-modules are of great significance. In this paper, firstly, the characteristics of MMC SMs short-circuit fault are analyzed and the calculating formula of fault component is deduced, then a method is proposed. Moreover, a novel differential under-voltage detection method is proposed based on SM detection capacitor voltage. Finally, the specific faulty IGBT location is carried out by wavelet transform. Simulations in PSCAD/EMTDC reveal that the proposed method in this paper can calculate accurately the IGBT capacitor voltage after the short-circuit fault of MMC, detect the faulty SM and locate the faulty IGBT precisely and rapidly, which verify the effectiveness and feasibility of the proposed method.

This paper introduces the basic situation, the power grid connection mode, and the DC control and protection function of Zhoushan VSC-MTDC transmission demonstration project, and analyzes the application of fast restart and start/stop of a single converter station, together with the operation effect of the project. Combined with the practical operation and maintenance experience, the main equipment problems such as DC control and protection, converter valve submodule, DC circuit breaker and DC measuring device are analyzed, and the direction of technical perfection is given.

In recent years, wind power has been rapidly developed in Guizhou,and many wind farms are far from load centers and locate in the ends of regional grids which weaken the stability of the regional grids. The paper focuses on a large-scale wind turbines tripping accident which previously occurred in a regional power grid of Guizhou province. Wind farms models and power grid models are built with actual parameters on DIgSILENT/PowerFactory platform, and the accident inversion simulations are carried out. Based on the inversion simulation results, the process of large-scale wind turbines tripping accidents are studied. The effects of wind turbine tripping on voltage and frequency stability of power grid are also analyzed. At last, the strategies which can improve the ability of low/high voltage ride through of wind turbine and avoid large-scale wind turbines tripping, are analyzed based on the regional power grid. Simulation results show the effectiveness and limitation of the strategies, which can provide a reference for similar cases in other regional power grid.