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China's renewable energy is expiring the transformation from the alternative power sources to main power sources. The installed capacity of renewable energy has ranked first in the world for six years, accounting for about 35% of the world's total installed capacity of renewable energy. This article systemically describes the development history of renewable energy in China, analyzes the current main factors affecting the accommodation of renewable energy, proposes measures to promote the development of renewable energy in China, and also lists major market mechanism for renewable energy accommodation in china, and main policies to promote renewable energy accommodation in china.

Large-scale renewable energy integration urgently requires flexible sources in China. For a long time, thermal power has always occupied a dominant position in the China's power supply structure. The peak regulation depth of large-capacity thermal power units is usually less than 50%, and the peak regulation depth of thermal power units in the north area is only about 20%. Exploring the technical path and economic operation of improving the flexibility of thermal power units, as well as achieving the optimization of technological transformation and sustainable development of capacity thermal power units, is of great practical significance for the accommodation and promoting the development of renewable energy in China. This paper describes current status of the transformation of thermal power plants in China, analyzes the objectives and costs of flexible transformation of thermal power plants, as well as the effectiveness of such kind of transformation for the accommodation of renewable energy.

At present, most stochastic production simulation algorithms can not consider large-scale new energy, and there are many deficiencies in the stochastic production simulation algorithm including wind farm and photovoltaic power station. Based on the actual operation data of wind farm and photovoltaic power station, this paper analyzes the power generation characteristics of wind/photovoltaic power station from the Perspective of statistics. The extraction method of wind/photovoltaic power generation output scenario characteristic index, the principle and method of scenario screening and the evaluation index of confidence output capacity are proposed. On this basis, taking the lowest total generation cost or the best energy saving and emission reduction effect of power system as the optimization objective, a practical power system operation simulation model considering three different scenarios of power balance, electricity balance and peak shaving balance is established. The objective of the model is to minimize the total generation cost of the power system or to achieve the best effect of energy conservation and emission reduction. The simulation results show that the proposed system operation simulation model considering large-scale new energy can be effectively used for the research of wind power and photovoltaic power consumption capacity.

This paper intends to investigate the operation of proton exchange membrane fuel cell (PEMFC) under steady state operation mode and transient operation mode when it is subjected to dynamic disturbance at the point of common coupling. The mathematical modelling of PEMFC is analyzed and a PEMFC model is simulated. The PEMFC is further connected to a boost converter and a full bridge inverter to create a grid interfaced power generation system. The proposed system has also been simulated under different operation mode and certain characteristics are obtained.

In order to reduce the cost of the electromagnetic hybrid unified power flow controller (HUPFC), the thyristor H-bridge ST topology is analyzed. This topology enables the “Sen” Transformer (ST) primary-side winding to achieve a two-stage voltage output. A simple two-stage ST switching strategy is proposed. In order to make the corresponding thyristor reliably turn off when ST is switched, the on-off characteristics and triggering conditions of the thyristor during ST switching are analyzed, and a reliable trigger signal generation circuit for thyristor is designed. The injection voltage estimation and ST switching delay are adopted, which reduces influence of control overshoot on ST switching control, optimizes the control structure of HUPFC, and analyzes the adjustment characteristics of HUPFC. Finally, the HUPFC is capacitated by the actual power flow calculation of distribution ring network, and the simulation model of HUPFC is built under PSCAD/EMTDC software. The steady-state simulation and transient simulation are carried out to verify the power flow control capability of HUPFC and the effectiveness of the control system.

According to the demand of photovoltaic(PV) connection with medium voltage DC grid, a PV DC step-up transformer based on power electronics is proposed, with H bridges connected in parallel at low voltage (LV) level, connected in series at medium voltage (MV) level, and is isolated by high frequency transformer. LVDC is directly boosted to MVDC with no DC-AC-DC converts. As the power flows from PV to grid is unidirectional, the H bridges at MV level are designed to be consisted of diodes to reduce the amount of IGBTs and cost of the device. Characteristics of the topology are analyzed, and formula of the equivalent duty ratio is derived. The duty ratio control is applied for PV DC step-up transformer with carrier phase shift technique. For each module, a unipolar& frequency multiplication modulation algorithm with IGBT's equal ON and OFF time is proposed to ensure the uniformity of IGBT's electrical stress and the reliability of the device. Finally, the proposed topology and control strategy is verified by the simulation on PSCAD/EMTDC platform. Results show that the voltage and current are shared equally among each sub-module, and the current fluctuation injected to network is very small. The experimental verification of the proposed modulation strategy is also carried out.

Synchronous Series Compensator (SSSC), a Flexible Alternating Current Transmission Systems device, is used for the flexible regulation of power system flow, which is of great significance to improve the transmission capacity and stability of the power grid. In engineering applications, system fluctuations, controller accuracy and dynamic adjusting etc. may bring about a slight DC component in the output voltage of SSSC. Since the loop resistance for the DC component is very small, the DC bias of the valve-side current would be significant, which will influence the stability and performance of the control system. Meanwhile, the series transformer and other devices would suffer DC magnetic bias, magnetic saturation of the core, higher loss and even harmonics, threatening the operation of the system.This paper proposes the mechanism that the DC component in the output voltage modulation wave will lead to a DC bias of the current on the SSSC valve-side. The open loop characteristics are simulated. And based on this, a DC component detection and feedback unit is introduced in the original controller to suppress the current DC bias. Finally, according to a SSSC demonstration project, a real-time digital hardware-in-loop simulation model is established and the effectiveness of the suppression strategy is verified.

Benchmarks are popular in many fields, but rare or absent in the CSCW research. Performance based evaluation would be a good choice if given a certain set of specific tasks. As the first step to promote a benchmark, we conduct this brief review about groupware evaluation by performance of specific tasks. Particularly, we collect commonly used specific tasks and classify them into four categories: hidden profile tasks, cognitive conflict tasks, trading tasks, and repair tasks. We also identify some challenges to achieve a benchmark.

Recently, both academia and industry have initiated research projects directed on integration of P2PSIP paradigm into communication systems. In this paradigm, P2P network stores most of the network information among participating peers without help of the central servers. The concept of self-configuration, self-establishment greatly improves the robustness of the network system compared with the traditional Client/Server based systems. In this paper, we propose a system architecture for constructing secure P2PSIP session initiation. The proposed approaches include: three-layer hierarchical overlay division, proxy based security, subjective logic based trust enhancement, NAT traversal, message routing, etc. After that, a prototype with 512 P2PSIP peers is implemented. We evaluate the system architecture in several aspects: implementation testing, Number of hops and the protection against malicious or compromised intermediate peers. We take Chord as the P2PSIP overlay as example. However, this system architecture is independent of Chord overlay and could be extended to the other DHT (Distributed Hash Table) technologies.

We obtain an existence and uniqueness result for an initial coupled forward-backward stochastic differential equation under some monotone conditions. Then this result was applied to backward linear-quadratic nonzero-sum stochastic differential game problem and get the explicit form of a Nash equilibrium point.

In this paper, we deal with one kind of stochastic nonzero-sum differential game problem for N players. Using the solutions of the backward stochastic differential equations and Malliavin calculus technique, we give the explicit form of a Nash equilibrium point.