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Large-scale integration of renewable energy resources in the Alternating Current (AC) grids will have a serious impact on power system operation. The development of the Direct Current (DC) is presented as a solution to overcome some of the negative impacts on massive micro-generation deployment. Over 100 years later, from the time when AC was proving superior over DC, the existing AC electric power grids, equipment, and transmission method facing a big challenge from DC. In this paper, what has changed since Edison and Westinghouse public battle are firstly discussed? Then the high voltage DC (HVDC) transmission system is depicted the developmental history and the system׳s structure, and the HVDC applications based on voltage-source converters (VSCs) combined with the renewable generation are introduced, such as onshore, offshore wind, and City Power Supply. Then, those key technologies are represented. Finally, how to build future electricity grid network and VSCs-HVDC may improve the world is explored, and some recommendations are proposed.

The maximum power point tracking (MPPT) methods for the photovoltaic (PV) power system have been considered by the experts in the whole world. A review of different MPPT methods is discussed in this paper. Firstly, the main methods at uniform radiation that will be deliberated are Hill-Climbing (HC), Incremental Conductance (IncCond), Perturbation and Observation (P&O), Fuzzy-Logic (FL), and Neural Network (NN). However, these existing methods have several drawbacks such as slow tracking speed, low tracking efficiency, which fail to extract maximum power at complex partial shading. Then, the more recent MPPT methods at partial shading are discussed to find the best MPPT control strategy, such as the particle swarm optimization (PSO) algorithm, Cuckoo Search (CS) method, and Fibonacci line search scheme, etc. The advantages and shortcomings of abovementioned MPPT methods are compared to find the optimal MPPT during partial shading conditions. It is imagined that this article will be a source of valuable information for PV professionals to keep abreast with the latest progress in the PV power area, as well as for new researchers to get started on MPPT.

In order to realize the sustainable development of country and society, many countries have established their renewable energy law and development strategy no matter developed countries or developing countries. It is well known that China is the largest developing country in the world, and the per capita GDP ranks more than 100, however, the total GDP ranks the second due to the huge population amount, and just behind USA. Certainly, the total energy consumption amount is huge, and the big energy demand has brought a serious of environmental problems such as acid rain, water and soil pollution, and resource exhaustion, etc. Fortunately, China central government has regarded the serious question to realize the sustainable development in future. The renewable energy law has been established in 2005. Firstly, China's energy situation and existing environmental questions in past years is introduced in this paper. Secondly, the distribution and the application practice of different renewable energy were introduced. Then, China's renewable energy policy is detailed introduced in the following section. The next section discusses the existing questions. Based on these discussions, the development barriers and recommendations are introduced, respectively.

The steady and maintainable energy supply for human development provides the strong motivation, which is necessary to every country in the whole world. The high strength carbon emissions has brought great harm to the earth since industrialization before hundreds of years, and the global warming and extreme weather cause humans to develop low-carbon economy. Low-carbon economy has become a consensus of the entire human race no matter developed countries or developing countries, which is the combination of the lifestyle changing and production structure basic changing and technical innovation. It is well known that China is the largest developing country in the world. With the rapid industrialization of country, energy demand of Chinese society is increasing in an incredible speed, China has become the second largest energy consumer and the first carbon emissions country at present. Furthermore, Chinese energy structure and production methods are very inappropriate, which cannot guarantee the sustainable development of China in future, and therefore actively developing low-carbon economy is the only road to realize China's economic development mode change and sustainable development, which is supported by central government and local governments. Low carbon economy for China is not only an opportunity but also a great challenge. Firstly, this paper discusses the current situation of energy supply and energy structure in China. Secondly, current situation of units’ energy consumption in China is discussed. Thirdly, some application practices of low carbon are described, such as low carbon traffic, low carbon city, and low carbon village. Then, the policies and law of China central government and local governments are described in the following paragraphs. At the end, the developmental prospect of low carbon economy in future China and the development barriers and recommendations are introduced, respectively.

Along the eastcoasts of China are large bodies of water, China has abundant ocean energy resource, such as the theory reserves of tidal resource is about 0.2 billion kW, as early as 1958, Jizhou tidal power station is the first tidal power station in China, which built in Shunde, Guangdong province, and more than 40 small tidal power stations are built in east coastal region in 1960s, and the total installed capacity is about 0.5 MW. But it is a pity, the application and development of tidal energy has not been regarded by the government and ordinary people due to the investment of power plant is big and the technology is not mature, so there are only several small tidal power stations in China, and Jiangxia tidal power station with an installed capacity of 3.2 MW is the most famous. Fortunately, with the rapid development of Chinese economic and society, the renewable and sustainable energy have been regarded by Chinese government, and the application and development of wind energy and solar energy is increasing in an incredible speed, and more and more specialists began to regard the application of tidal energy, and they thought that tidal energy can relieve the energy stress of east coastal region, and many layout of tidal energy exploitation is unfold in recently. This paper discusses the distribution zone and current developmental situation of tidal energy in China. Then, some application practice is described, such as tidal power station and tidal stream turbine. The policies and law of China central government and local governments are described in the following paragraph. At the end, the developmental prospect of tidal energy in future China and the development barriers and recommendations are introduced, respectively.

The steady and maintainable electric power provides the development momentum of a country's industrialization, which is indispensable to every country at present. It is well known that China is the largest developing country in the world. With the rapid development of economy and society, energy demand of Chinese society is increasing in an incredible speed, i.e., the annual accumulative total capacity of electric energy is about 0.1 billion kW, and the most of them is provided by the fossil fuel resource, and the share is about 90% in China. Certainly, it is a very inappropriate energy structure, so the sustainable development of country is impossible in future, the status must be improved in order to achieve sustainable development. Fortunately, China has large country area, and there are abundant solar resources. Development and application of solar energy have been regarded by the government and ordinary people, and they thought that solar energy can provide more and more electric energy in future, and more and more actual examples have been applied in the last decades, which are supported by central government and local governments. This paper discusses the distribution zone and current developmental situation of solar energy in China. Then, some application practice is described, such as solar energy greenhouse, solar energy hearth, solar water heater, solar lighting system, solar water pump, distributed generation (DG), grid-connect photovoltaic generation (GPG) and wind–solar hybrid system. The policies and law of China central government and local governments are described in the following paragraph. At the end, the developmental prospect of photovoltaic (PV) in future China and the development barriers and recommendations are introduced.

China is the largest developing country in the world. At present, more and more energy demand gives immense pressure to Chinese government. The inappropriate energy structure must be improved by Chinese government in order to achieve the sustainable development of economy and society. Development and application of renewable energy, such as wind energy, solar energy, biomass energy, etc., have been regarded by the government and the local people in the past 10 years, and more and more actual examples have been established, which are supported by government and plants in China. It is well known that there are abundant wind and solar resources in China. This paper presents the distribution zone and development and application practice status in China. However, a common drawback is existing in the stand-alone wind energy and solar energy generating power system, which is the unpredictable output electric power, and the output power depends on the unpredictable weather and climatic changes. Fortunately, the wind–solar hybrid generation system can partially overcome the problems. The conventional structure and key technology of stand-alone wind–solar hybrid generating system, the current status and outlook of wind–solar hybrid energy system are presented in the paper, for example, the city road lighting system, distributed generation, photovoltaic (PV) water pumping for irrigation, etc. At the end, the policies and laws of China central government and local governments are described, and the development barriers and recommendations are introduced.