Since the reform and opening up, China's economy has developed rapidly, but the mode of economic growth is mainly supported by the massive consumption of energy and resources. Energy supply is increasingly tight, energy costs account for a large proportion of product costs, and market competition is becoming increasingly fierce.
Electric energy is one of the main energy sources consumed by ferroalloy products, and electricity accounts for 70% of the cost of ferroalloy. It can be seen that the consumption of electric energy is the lifeblood of high-energy industries such as ferroalloy. How to adopt new technologies, new processes and new equipment to transform traditional industries, reduce product power consumption and reduce electricity expenditure are the main factors for ferroalloy production enterprises to reduce production costs and improve market competitiveness, and are the key to their survival and development. In order to reduce the production cost, enterprises have reduced their electricity expenses through self-built power plants (commonly known as self-owned power plants). However, due to the restriction of national policies and the sudden change of load in ferroalloy production, many self-provided power plants are unable to generate electricity, and some can barely generate electricity. However, due to the poor ability to withstand load fluctuations, the operation of generator sets is unstable. Therefore, it is imperative to solve the problem that enterprises' self-owned power plants are not connected to the grid (that is, isolated network) and directly supply power for ferroalloy production, give full play to the efficiency of power generation equipment in self-owned power plants and reduce the electricity cost of ferroalloy enterprises.
Patent technology of load regulation system invented by Shanxi Bosek Electric Power Technology Co., Ltd. (invention patent number: ZL200610065761.0; +0.0; Patent number of utility model: ZL200620008044. x)。 Specially aimed at the problem that the enterprise-owned power plant can't generate electricity when it is not connected to the grid, or although it can barely generate electricity, the generator set can't operate stably due to the fluctuation of power load. Successfully realized the non-grid-connected (i.e. isolated network) operation of enterprise-owned power plants, reduced production costs, and directly supplied power for high energy consumption products. This patented technology comprehensively applies many new technologies, such as automatic control, electric energy and heat energy conversion, energy storage and recovery, which not only solves the automatic control of load fluctuation adjustment of enterprise-owned power plants, but also completely solves the problem of load fluctuation adjustment caused by frequent switching of high-power loads in the production process of high-energy-consuming projects, so that the generator set can run safely and stably. At the same time, it can directly provide high-energy-consuming projects with the same quality as large power grids to meet the demand of production and domestic electricity.
Second, the working principle and control strategy of Shanxi Bosek Company to solve the isolated network operation.
2. 1, composition of integrated control system for load regulation
The comprehensive control system for load regulation consists of a steam turbine generator set, a steam generator, a water supply pipeline connected with the steam generator set, a computer processing unit, a signal detection unit, an electric heating unit, an aqueous medium energy storage unit, a transformer unit and an electric power control unit. As shown in the figure
2.2. Replace the power grid with a load regulation system to adjust the frequency of the power grid in real time.
Because the power frequency changes with the load when the single machine is running or the isolated network is running, the network frequency fluctuates greatly when the load changes, so the unit can not work normally and stably. When the load fluctuation is △W, if there is a device that can store and release △W electric power, and connect it in parallel to the isolated power grid, and adjust △W in real time to make it equal to the load fluctuation △W, the steam turbine generator set can operate at the same amount as originally set, and the power grid frequency remains unchanged. This fundamentally solves the problem that the network frequency changes with the load.
Because the fluctuation of load is the problem of electric energy fluctuation, or it is a kind of energy that is very large and continuously transported for a long time, it is impossible for the fixed load device to accommodate such a large amount of energy for a long time. Even if it can carry the rated capacity, it will "explode" after long-term operation. Shanxi Bosek Electric Power Technology Co., Ltd. adopts the design idea of "follow-up and follow-out", and converts the energy flowing into the load regulation system into other forms of energy at any time, and accepts new electric energy at the same time. In this way, a load regulating device capable of long-term stable operation is produced.
2.3, the use of energy storage technology, realize energy recovery, save energy, improve efficiency.
As we all know, high-power alternating current cannot be stored. Now there is a new technology abroad that can convert low-power electric energy into magnetic energy for storage, but it can't do anything about large-capacity electric energy. The patented technology invented by our company adopts the method of comprehensive utilization of energy circulation to adjust the load, that is, the power load of thermal power plants fluctuates and the electric energy of thermal storage power plants is stored. It does not waste energy and can solve the problem of stable operation of generator set when the load fluctuates frequently and in a large range. It can be said that there are many aspects, no network support, worry-free operation, energy cycle, economy and safety.
2.4, real-time control and detection of power parameters, automatic adjustment of power load.
The system receives the power generation information of the steam turbine generator set and the power consumption information of the power users, and generates control signals according to a unique control algorithm to control the switching of the electric heating unit, thus enhancing the real-time performance of the system. The traditional manual operation, long delay and low efficiency have been completely improved.
2.5, modular structure, tailor-made.
The setting of the system can be tailored according to the generator assembly machine capacity and user load of the self-owned power plant, which has strong market adaptability and can meet the needs of users.
2.6, reliable system, quality assurance.
On April 17, 2007, China Electric Power Research Institute conducted a 24-hour on-line inspection of the power supply system of Qin Xin Coal Coke Co., Ltd. operating in an isolated network, sampling 8559 times, and made a power quality assessment report. (adopting our patented technology: power load regulation system and method (invention patent number: 20064006571.0); Power load regulating device (utility model patent number: 200620008044. X) It has been running in the isolated network for 15 months. Test conclusion: The power supply system of Shanxi Qinxin Coking Coal Co., Ltd. operates in an isolated network, and the system voltage, voltage deviation, short-term flicker (Pst), long-term flicker (Plt), frequency deviation, three-phase imbalance, harmonic voltage, harmonic current and power factor all meet the national standards.
Three. Brief introduction of related technical indicators
1), and the design load regulation capacity is 0.25mw ~ 600mw.
2) The load adjustment resolution is 250KW；;
3) The execution time of the control instruction is less than 350ms; ;
4), load fluctuation, switching time is less than1s; ;
5), the console has manual/automatic function, the console has the function of fault indication and status display;
6) User-friendly design of operation interface, convenient operation and arbitrary setting of load power;
7) It has the functions of real-time data storage and time load curve drawing.
8) Power quality meets national standards.
3. 1, when the inductive load or resistive load suddenly drops, can the load regulation integrated control system instantly and accurately put the load into operation within the time range of 1s, so as to maintain the generator frequency at 50Hz 1Hz? When the inductive load or resistive load suddenly increases, can the system accurately cut off the load within the allowable range of the steam pressure of the boiler and turbine system and the inlet pressure of the gas turbine to ensure that the frequency of the generator system is within the range of 50Hz 1Hz? The above two cases have been proved in the practical application of the patented technology of load regulation integrated control system: when the load changes, the periodic frequency change is generally less than 1Hz, and normally less than 0.5Hz.
3.2. The capacity of the load regulation integrated control system is an important link of the scheme facilities, and its capacity directly determines the success or failure of isolated network operation and the investment of users.
An important index of load regulation integrated control system is how much load can be regulated, and its scale is directly related to investment and regulation ability. Therefore, it is particularly important to determine the regulation ability of the load regulation integrated control system. The comprehensive control and regulation ability of load regulation system is mainly determined by the total capacity of electrical equipment and the sudden change ability of electrical equipment. For the generator set operating in disconnection mode, ∑ generator set = ∑ stable electrical equipment+∑ abrupt electrical equipment. The key to ensure the stable operation of generator set is to adjust the power consumption of abrupt electrical equipment, that is, the adjustment capacity of load regulation integrated system should be slightly greater than the power consumption of abrupt electrical equipment.
3.3, from the power generation system, when the load fluctuation is less than 8%, the steam turbine generator set is affordable, which will not cause the action of the steam turbine emergency security system, nor will it cause the special voltage change of the generator set; The result of non-grid-connected (isolated) operation in the test and practical application of self-contained power plants is that the load fluctuation should not exceed 5%. For single-machine generator set with factory service, the smaller the adjustment rate, the better, and the larger the control strategy and investment, the better, considering the stability of load adjustment. According to the technical demonstration of our company, the load resolution of 250KW is the most reasonable.
3.4. The execution time of the control system directly determines whether the comprehensive control system for load regulation is effective or not, and it is the decisive factor to solve the timely adjustment of load change and load fluctuation, that is, the real-time performance of the control system. From the design experience and technology of our company, the execution time of instructions is less than 350Ms, while the control action time of actuators is generally less than 0.5s s. Through previous successful cases, it is proved that this cycle time is reasonable and the actual execution time is much faster than this time.
Four. Successful application case and economic benefit analysis of patented technology of load regulation system
In 2005, the patented technology of load regulation integrated control system won the national invention and utility model patent, and it was successfully applied to the brown corundum and calcium carbide smelting project and coking project of 2×6MW coal gangue self-contained power plant and 2× 12MW waste heat self-contained power plant of Changzhi Qin Xin Coal Coking Co., Ltd., and it has been running smoothly for three and a half years, with an average annual income of more than 30 million yuan. In 2008, it was successfully applied to the isolated network direct supply ferrosilicon smelting project of 2×50MW self-provided power plant in Taixi Coal Industry, Inner Mongolia and the isolated network direct supply ferrosilicon smelting project of 2×6MW self-provided power plant in Yuan Gang Coking Company, Qingxu, Taiyuan, and the operation has been trouble-free. The comprehensive control system for load regulation of waste heat self-contained power plant of Shanxi Jinlv Xingye Metallurgical Materials Co., Ltd. is under intense construction.
Off-grid operation of self-owned power plants (isolated network) not only gives full play to the equipment efficiency of enterprise-owned power plants, but also effectively reduces the smelting cost of products, and the effect of energy saving and consumption reduction is obvious. 70% of the cost of ferrosilicon is electricity, and the electricity price per kilowatt hour is reduced by 1 cent, and the cost of ferrosilicon is correspondingly reduced by 100 yuan/ton. The above-mentioned enterprise-owned power plants adopt our comprehensive load regulation control system to implement isolated network operation, and the electricity price will be reduced by about 20 cents, that is, the cost per ton of ferrosilicon will be reduced by about 2000 yuan.
Enterprise-owned power plants can be operated without grid connection (i.e. isolated network), and their load is located locally, so there is no need to pay the power grid transmission fee, which can ensure the reliable power supply for enterprise production and realize the comprehensive utilization of resources according to the production characteristics of enterprises. At the same time, the self-contained power plant has strong autonomy for its own use and is completely free from the limitation of peak shaving of power grid. Therefore, the production cost of ferroalloy enterprises can be effectively reduced.
In a word, it is an inevitable choice to realize the off-grid (isolated) operation of enterprise-owned power plants based on China's national conditions. The integrated load regulation control system developed by Bosek provides a solid guarantee for the isolated operation.