分布式发电对电力系统的影响研究

英文翻译2010 届电气工程及其自动化专业班级姓名学号指导教师职称二О一二年二月八日The impact of distributed generation on power systemSubject requirements:1 Citing a variety of current distributed generation technology, pointed out its advantages and disadvantages2 Domestic and international situation, distributed generation3 Described the impact of distributed generation on power system4 Write a research reportForewordDevelopment of power generation has gone through by the distribution to concentrate, to the concentration and distribution of the combination of the three stages, is now a combination of centralized and distributed phase of the development period. Early in the power system due to technical constraints, distributed generation, in the outskirts of the city to establish many services to local small-capacity power plants, power supply to the nearby load. Office of the 20th century, with the increase of the load and advances in technology, the establishment of large-scale power plant to become a mainstream power generation, the natural monopoly nature of the power system also contributed to the development of large-capacity units. Centralized power generation is characterized by large, giant, including the scale of the effective point of view dominates in the 1970s. Load growth more rapidly, to the late 20th century, the progressive introduction of several serious blackouts and electricity market, to create awareness of the importance of a flexible, reliable power generation, small-capacity, low cost, can provide reliable distributed generation of clean energy has been widely appreciated. Now distributed generation and power generation equipment directly connected to the load near, that is, forms of electricity generation with the grid or user meter installation at the general scale of power generation is relatively small, the use of new generation technologies. According to the size of the generating capacity, distributed generation can be divided into the following four levels: micro: 5kW following; small: 5kW to 5MW; Medium: 5MW to 50MW; large: 50MW to 300MW. Used in different power generation technologies, distributed generation can be divided into wind power, small gas turbine power generation, fuel cell power generation and solar cell power generation. Focus on a combination of power generation and distribution can give full play to the advantage of two power generation. Currently used mainly in the form the joint running of the province will invest in power generation flexible, compatible with the environment, distributed generation and grid, thereby improving the flexibility, reliability and security of the entire power system operation.1、The Distributed Generation Overview1.1 The definition of distributed generationAt present, the definition of distributed generation is not yet unified, and is generally believed that distributed generation DG (Distributed Generation) is to meet user specific needs, to support the existing distribution network of economic operations or meet the requirements of these two aspects, the user site or close to the user site configuration power of the number of kW to 50 MW of small generating units, compatible with the environment; from a broader definition of distributed generation is installed near the user, power generation facilities, including cogeneration CCHP and a variety of energy storage technology, regardless of the size of this generation form and type of primary energy use. Some other definitions of distributed generation as follows:• any generating facilities connected to the distribution network.• commercial backup diesel generators, for example, hospitals and hotels to install diesel engines.• Home standby generators.• The power company installed in the substation, power generation facilities used to provide voltage support or improve system reliability.• User-site or near the site users to configure power the number of kilowatts to 5O MW small power generation facilities.Installed in the load center or power generation facilities close to load centers.1.2 The use of distributed generation conditionsDistributed generation re-used because of the following points: (1) the continued rapid growth of the power load. With the economic development and people's living standards improve, the power load in a period of rapid growth, in some places even a relatively large power gap. However, the centralized power generation investment, long construction period, unable to meet the requirements of the electricity load growth. Distributed generation less investment and quick, and of great significance to alleviate the pressure of the electric load growth in the short term. (2) the gradual implementation of the electricity market as well as to improve power supply reliability and power quality requirements and tariff concerns. Industrial users to residential users, want to use the establishment and development of high quality and cheap electricity, the electricity market, provides a broad retail electricity markets, distributed generation, with its in-place service, flexible regulation, clean environment and many other advantages, will be will be more power-user's choice. (3) development of new technologies. With the development of new power generation technologies and new energy storage technologies, distributed generation of an increasingly wide range of applications. The development of science and technology makes the cost of electricity for distributed power generation equipment gradually reduced, and some distributed generation close to the traditional centralized power generation costs.(4) the issue of environmental protection is a growing concern. The coordination of development and environmental protection, environmental issues has been widely appreciated. China's centralized power generation of thermal power units with coal as the main energy sources, energy usage is relatively low, the sulfur dioxide emission pollution is more serious. Now distributed generation and more efficient, clean, renewable resources,effective solution to environmental problems.1.3 The main advantage of distributed generationCompared with the traditional centralized power generation, distributed generation has the advantage of very obvious, the following main points: (1) investment and, quick, low operating costs, capital risk. Traditional centralized power generation capital investment is usually in the billions of dollars in the construction period ranging from 5 to 15 years, due to large-scale, far from the center, so running costs are relatively high, the risk of investment capital. While small-scale distributed generation, so a small investment, and soon put into operation, requires less human resources to carry out maintenance, investment and financial risk is very small. (2) power generation is flexible, offering high reliability and power quality. Complex structure of the traditional centralized power generation, and system interconnection, in the event of a major accident will affect the customs user. Distributed generation system failure automatically disconnected from the system, improve the reliability of supply of the user; when the user side of the fault, the initiative is disconnected with the system, reducing the impact on other users. And distributed generation devices are usually in place to adjust the voltage and current waveforms to ensure high power quality. (3), less environmental pollution. Traditional coal-fueled power stations in the combustion process will generate a lot of serious air pollution, nitrogen dioxide, sulfur dioxide and carbon monoxide gas, and produce large amounts of waste and waste pollution. Distributed generation use of clean, renewable resources, with very low pollution emissions. And relatively low, the voltage level of distributed generation is relatively low, the electromagnetic fields generated by electromagnetic pollution is much smaller than the traditional centralized power generation. Due to the above advantages of distributed generation, distributed generation has a great advantage for users of electricity, power companies, national and social, is a win-win-win pattern. (1) For the power user benefits: distributed generation is conducive to lower user tariffs, improving power quality and supply reliability, while meeting the user a wide range of requirements to provide users with more electricity options to ensure that quality services ultimately improve the quality of life and standard of living of the user. (2) the benefits of the power companies: the distributed generation power companies to reduce investment, to avoid funding risks, while expansion of the electricity market, to provide more value-added services, the formation of new power relations, and promote the development of the entire power industry. (3) distributed generation benefits for the state and society: in favor to break the monopoly and introducing competition, open the door for other industries to enter the electricity market, in order to improve energy efficiency, promote the development of the cause of environmental protection, to ensure national security and social stability.2、The distributed power generation technologies2.1 The fuel cellWilliam. The Grove (w Grove), since the fuel cell was invented in 1839, its development is still in use for over 150 years. The fuel cell (Fuel cel1) is an aftercombustion by electrochemical reaction of hydrogen-rich fuel chemical can be converted into electrical energy generating device. Its working principle is similar to the general battery, as shown in Figure l.1, basically by the electronic conductivity of the cathode and the anode and the ionic conductivity of the electrolyte composition. Charge carriers in the electrode and electrolyte interface changes from electronic to ions at the anode (the negative terminal of the fuel cell, also known as the fuel pole), the oxidation reaction, fuel diffusion through the anode to lose electrons and generate electricity. The cathode (the cathode of the fuel cell, also known as air pole), the reduction reaction. When the external continuous supply of fuel and oxidizer, the energy released by the fuel oxidation is also a steady stream of converted into electricity and thermal energy J. Points, according to the type of electrolyte used in fuel cells can be divided into six kinds: proton exchange membrane fuel cell (PEMFC), direct methanol fuel cell (DMFC), alkaline fuel cell (AFC), phosphoric acid fuel cell (PAFC) The molten carbonate fuel cell (MCFC) and solid oxide fuel cell (SOFC).Compared with conventional power generation fuel cell has the following advantages: ①not subject to the Carnot cycle limit, the energy conversion efficiency; ②The power generation efficiency of up to 50% ~ 60%, the combined cycle power generation system consisting of 10 to 50 MW scale can more than 70% power generation efficiency; ③compared with conventional thermal power units of CO2 emissions can be reduced by 40% to 60% of emissions of NOx and SO; ④ small and efficient, improve the reliability of power supply: ⑤ low noise, high power quality; ⑥ The ability to adapt to load changes; the ⑦fuel cells can use fuels such as hydrogen, methanol, coal gas, biogas, natural gas, gasoline, diesel; easy the ⑧modular structure, the expansion and capacity increase, building plant a short time; the ⑨covers an area of less than lm / kW; ⑩degree of automation is high, can realize unmanned operation.Figure 1.1 fuel cell schematic2.2 Wind PowerWind power technology is to convert wind energy into electrical energy generationtechnologies, renewable wind power generation and environmental protection, global feasible, low cost and significant economies of scale, has been widely welcomed, the fastest-growing new energy. The form of wind power can be divided into off-grid and grid-type. Grid-connected wind power generation is the main form of large-scale development of wind power, the main trends of recent years wind power development. The larger grid-connected wind power generation is usually more than one capacity wind turbines constitute a wind turbine group, called the wind farm (also known as wind fields, wind fields). Wind farm unit (50 kw to 2 MW), large-scale, centralized installation and control features. The main equipment of the wind farm for the wind turbine generator connected to the transformer step-up and power system. Grid-connected wind turbines constitute a wind turbine and generator.① wind turbine. Wind turbine blades capture wind energy, wind energy conversion for the role of the mechanical torque at the wheels. An actual wind turbine, its capture of wind energy into mechanical output power P expression as:Pm = 0.5pACpV3w (1) Of which: p is the air density (kg / m), A is the swept area of the fan blades (m), acting on the face velocity of the wind turbine (m / s), wind energy conversion efficiency coefficient. The overall design of the wind turbine and the corresponding run control strategy should be to pursue, thereby increasing the output power.②generator. Currently used in wind power generators are mainly two types: synchronous generators and asynchronous generators, using an asynchronous generator. Induction generator because of its low power consumption, high reliability, without the excitation device and brush, simple structure, small size, rugged, basically no maintenance, etc., has become the ideal equipment for wind power generation system. Has obvious environmental benefits of wind power can reduce pollution gas emissions; at the same time, wind power can be used for non-grid areas of life and production of electricity required for remote rural and pastoral areas and island residents.2.3 Solar photovoltaic cellsSolar photovoltaic cells PV (Photovoltaic Cel1) power generation technology uses semiconductor material of the photoelectric effect directly convert solar energy into electrical energy. Transmission grid, power generation surplus during the day and night to take power from the grid. Photovoltaic cell power generation does not consume fuel, not subject to geographical restrictions, scalable, non-polluting, safe, reliable, and easy maintenance advantages. By sunshine intensity power output of photovoltaic cells, battery junction temperature and other factors, not scheduling, and system frequency and voltage to its essentially no effect.2.4 MicroturbineMicroturbine power of 25 to 75 kW natural gas, propane, gasoline, diesel fuel, ultra-small gas turbines. Compared with the existing power generation technologies, micro-gas turbine power generation efficiency is low, the full load efficiency of 30 percent, half load runtime efficiency of 10% to 15%, however, if a cogeneration efficiency can be increased to 75%. The microturbine is characterized by small size, light weight, highpower generation efficiency, less pollution, simple operation and maintenance, it is the most mature, most one of the commercial competitiveness of distributed power.2.5 Geothermal power generation technologyGeothermal energy is renewable heat from deep within the earth, which originated in the Earth's molten magma and the decay of radioactive material. Geothermal power generation is the use of underground hot water and steam power source for a new power generation technologies, and the thermal basic principle is the same, are the heat of steam after the turbine into mechanical energy, and then drive a generator. The difference is that, geothermal power unlike thermal power that huge boiler does not need fuel consumption.2.6 Other distributed generation technologies(1) biomass power generation technologies: biomass energy derived from biomass. Biomass power generation is the first biomass into forms of energy that can drive generators (such as gas, oil, alcohol, etc.), and then follow the universal power generation technology for power generation. (2) small hydropower technologies: small hydro usually refers to small hydropower stations and its matching grid collectively. Small hydropower development can be divided into the diversion type, dam type, hybrid, and four kinds of pumped storage. (3) ocean energy power generation technologies: ocean energy, tidal energy, wave energy, ocean currents, tidal current energy, water temperature difference and sea salt can be different forms of energy. At present, the ocean energy power generation mostly in the experimental stage, more mature is the technology of tidal power. Tidal energy and hydropower plants is the use of sea water fluctuation and the resulting water level difference to drive the turbine, driven by the turbine generator to generate electricity.Schedule 1-- the common distributed generation technology3、The impact of distributed generation on power system3.1 Tistributed generation on power system voltagePrimary access of distributed power distribution network, access to DG after multiple power distribution system from the radial structure to structure, size and direction of the trend may be a dramatic change in the steady-state voltage distribution network has also changed, the original some regulator program may not be able to meet the distribution network access to distributed power supply voltage requirements. Must assess the impact of distributed power system voltage of electricity to ensure that in the case of a growing number of distributed power applications, they do not have adverse consequences to the user. The flow calculation is the impact of this quantitative analysis of the primary means, but the traditional method of flow calculation does not consider the impact of distributed generation, and therefore invalid. Induction generator, the excitation ability to regulate several typical synchronous generator and fuel cell DG modeling, and distribution power flow calculation method based on the sensitivity of compensation, suitable for power distribution contains a variety of different forms of DG systems.Distributed generation on distribution network voltage as follows:① distributed generation access would be for distribution feeder voltage distribution of a significant impact on the size of the specific impact of distributed power, access location has a great relationship.② same penetration (Penetration Leve1) distributed power concentrated in the same node, the support effect is weaker than the voltage distribution across multiple nodes.③steady-state case, the feeder transmission power is reduced and the DG output reactive power support, load node voltage along the feeder is elevated.Discussed above are distributed power distribution network. When the wind farm connected to the grid, due to the wind farm to enter the randomness of the wind changes, and wind power are mostly asynchronous generator required to absorb large amounts of reactive power from the grid, it can easily cause the entire grid voltage stability problem, and even will result in the entire power system voltage collapse, but are not limited to where the power distribution system. Bakersfield, California, USA, for example, Seawest wind farm is often the voltage stability problem in the grid can not accept wind power, forced the shutdown of the wind farm.3.2 Distributed generation on power qualityDistributed power generation is a lot of non-linear load to establish the basis of power electronics technology, a lot of power electronic converters will cause the grid current and voltage waveform distortion caused by harmonic pollution, distributed generation there are two aspects of power quality:①voltage flicker. Distributed generation cause voltage flicker factors include: the start of a large-scale distributed unit, the voltage feedback control equipment, the interaction of the adverse effects of the distributed unit of output short-term drastic changes as well as distributed unit system.② the introduction of a large number of harmonics. Since a large number of power electronic devices used in distributed generation, so the system will inevitably bring a large number of harmonics, harmonic amplitude, and order by the power generation as well as the operating mode of the converter. Distributed power supply for power quality, and to discuss the introduction of DG bus harmonic voltage levels for large-scale distributionnetwork, and suggested that we can install a special filter to suppress harmonics in a higher level of harmonic voltage on the bus. Although the introduction of distributed generation will cause voltage flicker, and the introduction of a large number of harmonics, but the distributed generation also exists the potential to improve power quality when the grid associated with heavy load, distributed generation can be quickly put into use, the system as much as possible reduce failures, improve grid stability, thus ensuring power quality.3.3 Distributed Generation the shadow noon on Relay ProtectionMost of the power distribution system, especially in rural areas, its structure is radial, the main purpose of using this structure is to run simple and overcurrent protection for economic, when the access to the distributed power distribution network, the radial network will become the network around the power and user connectivity, the trend is also no longer one-way flow to each load from the substation bus, distributed generation will be equipped with the original grid of the relay to have a greater impact:1) when the DG is running may cause failure of the relay. DG fault current may reduce the flow of the feeder relay current, so that the relay failure.2) DG access distribution network may cause relay malfunction. Adjacent feeder fault may make the original faulty feeder tripping.3) a change in the level of distribution network fault. The fault level increase or decrease depends on the run the distributed power of the number and types of failure raise the level of requirements of the switchgear upgrade failure lower level may give over-current protection pose a problem. Therefore, a distribution area of distributed power capacity, leaving the fault current to produce a substantial change, you must improve the capacity of its circuit breakers and upgrade protection device.3.4 Distributed generation on electricity marketMarket, the rise of the electric power industry to lift the control and power, making a variety of distributed generation in a unified and open market for fair competition for the opportunity to: (1) electricity users to provide a wide selection of different electricity suppliers; ② different times electricity consumption; ③ different quality of power supply;④different measurement methods; ⑤different rate structures; (6) different methods of payment; the ⑦ different user side management plan; to ⑧ own power generation or power storage.With the opening of the grid, the introduction of electricity retail market, the retail electricity market competition in the electricity supply to the enterprise-owned power plants and the user's own installation of distributed power to bring business opportunities, with distributed power supply in the retail electricity market faces three options: (1) by the power from the grid; ② generating their own power, self-sufficiency; ③ own electricity and selling electricity to the grid. Electricity generation competition market information and retail electricity market demand information, the user can use to live their own distributed power, let it play a greater role, resulting in greater benefits for himself or near the user to provide heating and for electric service. The establishment of the retail electricity market will be established retail electricity mechanism, any form of power generation, can be used as electricity suppliers to provide electricity products to the retail electricity market, faircompetition in the retail market.3. 5 The impact of distributed generation in China 's key problems3. 5. 1 Distributed generation power position and capacity determinationDistributed power position and capacity determination is to design a distributed system is an indispensable prerequisite. Distributed generation is to make full use of new renewable energy for power generation, is now the generation mode: micro gas turbine, wind turbine, photovoltaic power generation systems, such as fuel cell, according to the customer terminal desired size and location environment, a comprehensive consideration of various indicators, thereby determining the power generation mode. Power generation capacity not only to satisfy the load during the normal operation of the energy required to emergencies, and to have a certain capacity, can use gray correlation, neural network, wavelet analysis technology to establish the precise load forecasting model. Power generation equipment position should not only consider the peripheral energy, transportation, geographical environment and other factors, but also consider how to layout the line loss as small as possible, so as to improve the system of economy, reliability and flexibility.3. 5. 2 Power electronic conversion interface researchIt is the rapid development of power electronics technology enables distributed power generation to be possible, any kind of distributed generation to solve distributed power supply and power grid, energy storage system, a user interface between the energy transformation. In recent years, power electronic equipment in power and pressure has been greatly improved, but still did not meet the requirements of distributed generation, the need for further development of new power electronic equipment with low cost, high power, high voltage, high current level of energy conversion system. For distributed generation in power electronic interface is divided into the following four categories: DC-DC converter, inverter, the output filter, processor. The four standard interface to a reasonable design, which has low cost, high reliability, final implementation interface modular. Modular interface according to different connection modes to adapt to different voltage levels of power, the distributed power generation system, in practice and exploration in the formation of inverter topology and control strategy. In addition, still need exploration research on power electronic interface circuit for distributed generation to provide supporting services, such as the compensation of reactive power, voltage frequency limit, control flow. Finally, neglected: Power Electronics Technology in the energy storage system will enter a more in-depth exploration and research.3. 5. 3 With traditional grid based distributed generationDistributed generation is the future developing direction of power system, but does not mean that it will be the traditional centralized power out, over a period of time of the two power generation mode coexistence, mutual complement. Combined with the traditional grid and distributed generation advantages, its reasonable together, this is the most sensible choice. Now the plan has the following several kinds : the first kind is distributed power from DC output is converted to AC, at the same time requirements andAC grid to maintain the absolute synchronization; second is the distributed power from DC output is converted to AC, direct supply certain load without the need for and large power grids interactions; third is the distributed power and AC grid isolation, has become an independent system. We need to various network scope, operating conditions and key techniques.3. 5. 4 Distributed generation to the system power grid stability introduce new problemsDistributed generation on power system stability is mainly depending on the power level and the generation of these two aspects. As a result of distributed generation and traditional large power grid parallel operation modes have different choices, and a large number of power electronic devices and capacitance, inductance is introduced, which will change the original system network topology, which influences the trend of the distribution, to the stability of the grid brings uncertainty. External disturbance may lead to the frequency and voltage are not synchronized, so as to bring down the whole system. How to do the fault can not mutually affected, meet the external disturbance can cooperate with each other will be arduous and complex task. Joint operation system in various condition of stability is one nots allow evasive topic, brook no delay.3. 5. 5 Energy storage systems researchElectric power storage problems of power system is long-term since did not completely solve the problem, distributed power generation will be introduced to further accelerate its technical development urgency. Now a promising energy storage technology has storage battery, super capacitor energy storage, as well as the superconducting energy storage flywheel energy storage. These energy storage technology in the industrial field have been used, and have achieved good results, but if they are applied to distributed generation, also in the storage capacity, reliability and economy for further improvement. How will the system energy storage capacity and ensure energy storage system can timely security to absorb and release electric energy, the joint running of power system security stability and economy plays an important effect.3.6 Other effectsCurrently, distributed generation is generally not for the dispatch center scheduling, operation and control of distributed generation in a way blind and disorderly, leaving a certain security risk to the operation of the entire power system. For example, distributed generation will give the power system reactive power compensation, voltage control has brought adverse effects; the changing requirements of distribution automation and demand side management system; also required to develop and improve relevant laws, regulations and industry standards.4、The status and prospects of distributed generation4.1 Distributed Generation Status(1) become a useful unit of Distributed Energy Supply System in the United States, the capacity of 1 kW to 10 MW of distributed generation and energy storage unit. According to the prediction of the distributed power of the U.S. alliance, 2020, distributed。