With the rapid development of China's power industry, users have higher and higher requirements for power supply quality, and the peaking and frequency modulation of power grids are more frequent. This requires more units not only to invest in high quality CCS, but also to invest in reliable automatic power generation control. (AGC) to meet the needs of power grid frequency modulation and peak shaving. At present, there are fewer units that actually invest in AGC in China, and fewer units that invest in AGC. Sunshine Power Company's 300MW coal-fired unit was inspected and accepted on April 17, 2001. The indicators met or exceeded the requirements, and the AGC was put into operation with high quality. Therefore, combined with the successful experience of Sunshine Company, the AGC operation of thermal power unit is analyzed and discussed, and the strategy of improving the reliability of AGC operation and improving its operation quality is studied to guide the actual test and improve the quality of AGC operation of large-scale power grid thermal power units. It has important meaning.

1AGC control function overview 1.1 Function principle Automatic power generation control is a necessary means to ensure high-quality economic operation of the power grid. It is of great significance to the safe and stable operation of the power grid. Its functional principle is: the actual value of the exchange power according to the measured system frequency or tie line. The difference between the planned values ​​is used to calculate the adjustment amount required by the system, that is, the regional error or regional demand, and is distributed to the units under the control of each AGC according to the principle of economic distribution. The unit under the control of AGC feeds back its regulation to the AGC main station. The main station compares and calculates the power generation adjustment of the feedback unit and the actual operation of the system, calculates the current required adjustment amount, and then distributes it to form an AGC closed-loop control system. The closed loop control principle of the thermal power plant AGC is as shown.

In the case of the AGC command, the condition indicates the actual power of the unit, indicating the load deviation.

It can be seen that the premise of AGC investment is the reliable investment of CCS. CCS is the basis of AGC operation. Therefore, before the AGC is put into operation, it should first respond to the unit's basic automatic and CCS into the main station control output dispatch center AGCå±®Channel ~ ~ furnace coordination AGC closed-loop control principle map optimization and adjustment to ensure its good investment. At the same time, according to the different characteristics and requirements of CCS and AGC (the characteristics of CCS are concentrated on the overall coordination and cooperation between the unit and the furnace, pay attention to the stability of the unit, that is, to ensure the dynamic and static deviation of each main parameter; and AGC The characteristic is to pay attention to the adaptability of the unit to the power grid, paying attention to the rapidity and accuracy of the unit load response, that is, to ensure the load response rate and delay time), and to improve the CCS to ensure that it meets the requirements of the AGC.

1.2 AGC control main technical indicators requirements (see Table 1) Table 1 AGC main technical indicators requirements and Sunshine 4 unit AGC test results domestic indicators provincial indicators Sunshine 4 unit AGC commissioned indicators AGC delay time adjustable load range load regulation Rate 2AGC commissioning and improvement Before the official AGC joint test of Sunshine Unit 4, the coordinated control and related foundations were automatically improved and optimized, and some important influencing factors that restricted the stable operation of the original coordinated control were solved, and the unit was improved. Coordinated control of dynamic adjustment quality. On the basis of the improvement of CCS control quality, combined with the characteristics of AGC operation, CCS has been further improved: dynamic differential feedforward is enhanced, boiler load is quickly adjusted to improve unit load response rate, and load and main steam pressure are reduced. Dynamic deviation; make full use of the heat storage of the boiler, further adjust the differential link on the machine side, increase the dynamic over-opening of the turbine door, and reduce the load delay time of the unit. The furnaces cooperate with each other to ensure the unit's requirements for grid load, which greatly improves the various indicators of AGC operation (see Table 1).

2.1 Tracking function to ensure uninterrupted switching Conventional AGC design often does not design tracking function due to telephone scheduling and equipment, etc. AGC retreat can only be done by manual dispatcher and power plant operator. This method is subject to human influence, and the signal deviation is large. It is easy to cause large disturbance when the AGC is switched back and forth, which is not conducive to the stability of the unit and the power grid. Therefore, the manual tracking function of the AGC command must be set in the main station of the tuning center.

2.2 Increasing AGC error processing protection and improving operational reliability At present, there is no uniform standard for AGC design in the whole province and even the whole country. The functional design is very imperfect, especially the AGC signal protection function is almost not considered, and this is precisely affecting the reliable operation of AGC. An important factor. When the AGC of the Sunshine Unit 4 was put into operation, the signal protection logic was added on the basis of the original design by analyzing and researching the AGC signal disconnection, short-line, over-limit, error, etc.: When the AGC signal is short-circuited, disconnected and When the signal channel is faulty, the system automatically cuts the AGC to CCS mode; when the AGC command has an error within the range of the range, the unit load command should be kept for 3 minutes and wait for the correct AGC command. Otherwise, the system will automatically switch to CCS mode after 3 minutes.

2.3 Feedback unit status information, improve coordination ability In the original design, only AGC command, AGC feedback and AGC request are designed. The status of the unit (auxiliary output, adjustable range and setting rate, etc.) is not fed back to AGC. The primary station, causing the AGC command given by the primary station may be disconnected from the actual possible output achieved by the crew. Therefore, the maximum output, minimum output and load change rate of the unit are fed back to the AGC main station to output commands on the basis of the unit information, which makes the operation more reliable and the AGC command more effective and reasonable.

2.4 The impact of the start and stop of the powder machine (pulver mill) on the AGC The Sun No. 4 unit adopts an intermediate storage type powder system, which is designed with 4 coal mills and 16 powder feeders. According to the design, each powder feeder can carry a load of 25MW, 12 sets can be filled with 3UUMW, but due to the different coal types and coal quality changes, the actual maximum output of each powder feeder is less than 20MW, and according to the actual operation It is often necessary to continuously adjust the maximum output of each powder feeder. When the unit is running in the AGC mode, as the load rises and falls, the frequent start and stop of the powder feeder will inevitably occur, and the start and stop of the powder feeder directly affects the combustion and affects the dynamic deviation of the various indicators of the unit; especially the manual When controlling the start and stop of the powder feeder (pulver mill), the time, sequence and mode of start-stop will cause large fluctuations in fuel, which will have a greater impact on the load, thus affecting the commissioning quality of the AGC. Therefore, it is recommended to improve the start-stop logic of the powder feeder, realize self-start and stop, reduce the impact on the load, and further improve the quality of AGC operation.

It is the 24h load tracking curve of Sunshine No. 4 from April 9th ​​to April 10th. It can be seen from the figure that the set value and the actual value basically coincide, indicating that the AGC operates well.

3AGC operation mode discussion AGC can have two kinds of control methods: First, in the case that the unit AGC allows the input (or the unit AGC request), the command is dispatched by the middle, and the operation personnel manually input; the second is the AGC mid-adjustment request, the unit allows In case of automatic or manual input by the operator.

The original design adopts the second scheme, but because the scheme requires the middle to send out the request signal, the operating personnel should put the AGC control within 30 minutes if the unit conditions are met, otherwise the AGC request is invalid, that is, the control party cannot understand The condition of the crew is only blindly issued with the order of commissioning, and it is not practical, and it is not practical.

According to the current situation of the provincial power grid, in order to make the control more transparent and the safe and stable operation of the power grid and the unit, after analysis and discussion, the AGC allowed input, AGC input feedback, AGC signal valid, and the maximum allowable capacity of the unit are added in the commissioning of Unit 4. Signals such as load, minimum allowable load on the unit, and allowable rate of change of the unit load. The first mode of operation is adopted, that is, in the case that the AGC is allowed to input (the AGCENABLE of the OM screen turns red), the operator sends an application to the AGC according to the actual operation of the unit. After the mid-range notification allows the input, the operator manually puts in the AGC and sends a feedback signal to the middle adjustment AGC (the AGCMODE of the screen turns red). After receiving the AGC input signal from the unit, the unit information is modified on the AGC main unit to modify the unit's target load setting value. At this time, the sound and light alarm display will be issued on the running centralized control word line to remind the operating personnel to follow the AGC. Set the target load and the actual speed of the powder feeder to determine the number of machines to start and stop.

The AGC control mode will be automatically removed when any of the following conditions occurs: the unit exits the coordinated control mode; 4 The subject and direction to be studied The current scheduling has been transitioned from empirical scheduling to economic analysis scheduling, and AGC is a basic in the EMS system. Functions have been widely adopted in developed countries. China has also done some practice and research in recent years, but due to current management and technical reasons, AGC is still in its infancy. According to the requirements of AGC for grid-connected units of 200MW and above, the key need is to grasp the input rate and adjustment quality of the coordinated control system of the power plant, improve the number of AGC units and the application level of AGC control, and make the control of the power grid safer. Stable and economical. Through the commissioning process and experience of the AGC input of Unit 4 of the Sunshine Power Generation Company, it is believed that the following two aspects of research should be carried out.

Through further on-site engineering experiments, the self-starting and stopping of the powder feeder is realized, and the AGC automatic control plays a greater role in improving the operation level of the unit.

At present, only one unit is put into the AGC automatic power generation control, and the load distribution under the control mode of the multiple units AGC and the realization of economic operation are all issues that need to be studied in the future.

5 Conclusion With the 300MW coal-fired unit of Sunshine Power Generation Co., Ltd., the functional characteristics and control ideas of the automatic power generation control system are analyzed. Some problems affecting the quality of AGC operation are pointed out. The improvement of AGC technical indicators and the improvement of AGC operation are proposed. The strategy of reliability and the issues that need to be addressed in the future. The investment experience of AGC of Unit 4 of Sunshine Power Generation Company can be used for reference by similar units.

(Editor: Wang Lixin)

Car Exterior Accessories

Auto Exterior Accessories,Car Front And Back Bumper Guard,Universal Car Exterior Accessories,Car Interior And Exterior Parts

Ningbo Longyang Auto Products Co., Ltd. , https://www.zjlongyang-manufacturer.com