Distributed power on report

Distributed power supply device refers to a small modular independent power supply with power from several kilowatts to 50 megawatts, which is compatible with the environment. It can be used to meet the specific requirements of power system and users. The following is my carefully organized report on the opening of distributed power supply, hoping to help you!

1 Significance of topic research

1. 1 the concept of distributed power generation

Distributed power supply refers to the small power supply distributed near the load, which is relative to the traditional centralized power supply. At present, distributed power generation technology is developing rapidly all over the world. On the basis of power supply from large power grid, introducing small-capacity (generally less than 50Mw) distributed power supply (DG) into the distribution system near users can comprehensively utilize existing resources and equipment and provide users with reliable and high-quality electric energy. When distributed power is introduced into the distribution system, the quantity and direction of active power and reactive power transmitted in the distribution line change, and the distribution system becomes a multi-power system, called distributed generation system, which is actually a distribution system in which distributed power runs in the power grid. At present, the power supply systems in the world are all centralized single power supply systems characterized by large units, large power grids and high voltage. Although 90% of the global power load is provided by this centralized and single large power grid, the quality, safety and reliability of energy and power supply are increasingly demanding in today's society, and the large power grid can no longer meet this requirement due to its own defects. Because the failure of any point in the large power grid may have a great impact on the whole power grid, and in serious cases, it will cause a large-scale power outage or even the whole network paralysis, resulting in disastrous consequences, and such accidents also occur from time to time abroad; Moreover, this large power grid is easily destroyed by war or terrorist forces. One of the main objectives of the total military strike is to destroy large power plants or power stations. Once the large power grid is destroyed, it will seriously endanger national security; In addition, centralized large power grid can not solve the problem of tracking the change of power load, and the cost of building a power plant for short peak load is huge and the economic benefit is very low. According to the experience of western countries, the combination of large power grid system and distributed power generation system is the main method to save investment, reduce energy consumption and improve system security and flexibility.

1.2 Influence of Distributed Generation on Power Grid

The main task of traditional distribution network planning is to determine the optimal system construction scheme according to the results of spatial load prediction in the network during the planning period and the basic situation of the existing network, so as to minimize the construction and operation cost of the distribution system on the premise of satisfying the load growth and safe and reliable power supply.

However, the access of distributed generation makes the distribution network planning break through the traditional way and has a far-reaching impact on the distribution network planning. Mainly as follows:

(1) The access of distributed generation will affect the load growth mode of the system, making the load forecasting and planning of the original distribution system face greater uncertainty.

(2) There are many nodes in the distribution network itself, and a large number of distributed generator nodes join the system, which makes it more difficult to find the optimal network layout scheme in all possible network structures.

(3) For the hybrid networked power supply system with various types of distributed power generation, it is a problem to be solved to establish a model according to the distribution characteristics of various energy sources, determine a reasonable power supply structure in the distribution network, and coordinate and effectively use various power sources.

The function of 1.3 power flow calculation and the requirements for power flow algorithm after introducing DG mainly include:

(1) In the power grid planning stage, through power flow calculation, the power supply capacity and access points are reasonably planned, the power grid structure is rationally planned, and the reactive power compensation scheme is selected to meet the requirements of power flow exchange control, peak shaving, phase modulation and voltage regulation in large and small modes at the planning level.

(2) When compiling the annual operation mode, based on the expected load growth and the commissioning of new equipment, the typical mode is selected to calculate the power flow, find out the weak links in the power grid, and provide reference for the dispatcher's daily dispatching control, and put forward suggestions to the planning and infrastructure departments to improve the power grid structure and speed up the infrastructure progress.

(3) Power flow calculation under normal maintenance and special operation mode is used to compile daily operation mode, guide power plant startup mode, active and reactive power adjustment scheme and load adjustment scheme, and meet the thermal stability and voltage quality requirements of lines and transformers.

(4) Analyze the influence of expected accidents and equipment outage on static safety, and formulate the adjustment scheme of expected operation mode.

However, after the introduction of distributed generation into distribution network system, new requirements are put forward for power flow calculation. Distributed generation is different from general load nodes and is much more complicated, so it is bound to introduce new node types into power flow calculation. Therefore, it is necessary to form a power flow calculation method that can effectively deal with various distributed power sources. Ring network may appear in the original radial structure system, so the power flow calculation method must have the ability to deal with ring network. The difficulties affecting the application of traditional power flow algorithm mainly focus on the modeling of distributed generation and its processing methods in power flow algorithm. The distributed generation is simplified as a node type and substituted into the traditional power flow calculation. The general simplification includes: the synchronous generator is regarded as PQ node, that is, the three-phase impedance of the synchronous generator is connected by a three-phase balanced voltage source to form a model of constant power output, and it can also be directly regarded as a PV node with constant active output and voltage amplitude in the algorithm that can handle PV nodes; For asynchronous generators, although the absorbed reactive power varies with the voltage amplitude at this point, in the distribution network, the voltage unit value of each point is basically around 1.0, so it can be approximately considered that the reactive power absorbed by asynchronous generators is constant and treated as PQ nodes.

2

2 design tasks

As mentioned above, power flow calculation of distribution network is an important basis for economic operation and system analysis of distribution network. On the basis of large power grid, introducing small-capacity distributed power supply into the distribution system near users can comprehensively utilize existing resources and equipment and provide users with reliable and high-quality electric energy. However, the introduction of distributed generation has brought great influence on power flow, voltage quality and power loss. The traditional distribution network power flow algorithm is difficult to meet the requirements of distributed power generation system power flow calculation, so the existing distribution network power flow algorithm must be reformed and adjusted to make it suitable for systems with distributed power sources. It is of great theoretical and practical significance to carry out this research.

According to the requirements of the task book, the design tasks that need to be completed are:

1. Several commonly used traditional power flow algorithms-Newton Raphson method, which are suitable for three-phase unbalanced distribution network systems, are studied, and the forward-backward method is improved. And choose a key research;

2. Analyze the characteristics of common distributed power sources and establish their models;

3. Research the power flow algorithm which can deal with distributed generation;

4.MATLAB programming, IEEE standards and improved examples verify the proposed algorithm.

3 design scheme

3. 1 Types and characteristics of distributed power generation

Common distributed power generation technologies include wind power generation, solar photovoltaic power generation, micro gas turbines and fuel cells.

(1) Wind power generation: Wind power generation technology is a kind of clean energy, which converts wind energy into electric energy, and its output power is determined by wind energy. Wind power generation is the most mature and promising power generation method in new energy development technology at present.

(2) Solar photovoltaic power generation: Photovoltaic power generation uses solar cells to directly convert solar energy into electric energy according to the principle of photovoltaic effect. Grid-connected photovoltaic power generation system is the mainstream trend of photovoltaic power generation system.

(3) Micro gas turbine power generation: Micro gas turbine is a new type of gas turbine with a power range of less than 30~300KW. The development of micro gas turbine technology and its commercial launch greatly increase the possibility of distributed power generation for small users. The compactness, reliability, remote operation and environmental friendliness of micro-turbine power generation devices mean that they are particularly suitable for regional applications of distributed power generation.

(4) Fuel cell power generation: Fuel cell power generation is different from traditional thermal power generation, and its fuel is directly combined with oxidant such as air or oxygen under the action of catalyst to produce chemical reaction.

Opening Report on Undergraduate Graduation Design of Southwest Petroleum University

Therefore, power generation should be carried out at the same time as water production, so its essence is chemical energy power generation.

3.2 traditional power flow calculation method of distribution network

Distribution network power flow algorithm is the basis of distribution network analysis, and network reconfiguration, fault handling, reactive power optimization and state estimation all need distribution network power flow data. Therefore, a set of power flow programs with excellent performance is the key to develop DMS system. Compared with transmission network, the network structure of distribution network is obvious.

3.2. 1 Newton raphson method

Newton-Raphson method is a method to calculate nonlinear equations. As long as the state quantity reaches a certain domain of its solution, it converges at a square speed, regardless of the scale of the solution, that is, it can converge for 2 ~ 5 generations regardless of the size of the network, which is suitable for the practical algorithm of theoretical calculation of line loss of various complex distribution networks (radial, ring or mesh) at present.

Basic steps of Newton-Raphson power flow calculation;

(1) forms the node admittance matrix;

(2) setting an initial value u for each node voltage;

(3) Substituting the initial value of the node into the relevant formula to find the constant term vector of the modified equation;

(4) Substituting the initial value of the node voltage into the solution to find the Jacobian matrix elements;

(5) solving a correction equation to obtain a correction vector;

(6) calculating a new value of the node voltage;

(7) Check whether it converges, if not, start the narrow iteration from step 3 with the new value of each node voltage as the initial value, otherwise, enter the next step;

(8) Calculate branch power distribution, reactive power of photovoltaic nodes and injection power of balanced nodes.

The above is Newton Raphson method, with accurate calculation and simple principle. Easy to program; The calculation speed is fast.

3.2.2 Improved forward push-back method

The algorithm uses a unique and novel hierarchical method to search network nodes from the last node to the root node in turn, forming a hierarchical node array with a chain hierarchical structure, eliminating complex node and branch numbers in the calculation process; At the same time, considering the prominent problems of three-phase parameter asymmetry and three-phase load imbalance in distribution network, the phase domain model is directly used for calculation; For the ring network problem, the power compensation method is used to deal with it effectively. It has the advantages of fast convergence, few iterations and saving memory.

At present, the forward-backward method mainly adopts the hierarchical method of breadth-first search number, but this method needs to renumber the nodes and branches of the network and record the hierarchy of each node, which is complicated to handle. This paper improves the hierarchical method of nodes, directly records the relationship between nodes and branches, and directly forms a one-dimensional hierarchical array with chain structure, which is simple and easy to operate without renumbering.

;