統頻率的變化是由于發電機的負荷功率與原動機輸入功率之間失去均衡所致．因而調頻與有功功率調理是不可分開的。電力系統負荷是不時變化的，而原動機輸人功率的改動則較遲緩，因而系統中頻率的動搖是難免的。負荷的變動狀況能夠分紅幾種不同的重量：第一種是頻率較高的隨機重量，其變化周期普通小于10s，是靠單元機組調速系統來自動調速完成的，即一次調頻，一次調頻的特性是由汽輪發電機組自身的調理系統直接調理，因此其響應速度快；第二種為脈動重量，變化幅度較大，變化周期在10 s～3 min之間；第三種為變化很遲緩的持續重量。后兩種要經過改動汽輪發電機組的同步器來完成，即經過平移高速系統的調理靜態特性，從而改動汽輪發電機的出力來到達調頻的目的，稱為二次調頻。當二次調頻由電廠運轉人員就地設定時，稱為就地手動控制。
D88尊龙The change of the system frequency is caused by the unbalance between the load power of the generator and the input power of the motor. Therefore, frequency modulation and active power regulation are inseparable. The load of power system varies from time to time, while the change of the power of the prime mover is slow, so the frequency fluctuation in the system is inevitable. Load changes can be divided into several different weights: the first is the random weight with higher frequency, whose change period is usually less than 10 seconds, which is accomplished by automatic speed regulation of the unit unit speed control system, namely primary frequency regulation, whose characteristics are directly regulated by the regulation system of the turbogenerator unit itself, so its response speed is fast; the second is the fluctuating weight. The change period is between 10 s and 3 min, and the third is the continuous weight which changes slowly. The latter two are accomplished by altering the synchronizer of the turbogenerator unit, that is, by adjusting the static characteristics of the translation high-speed system, the output of the turbogenerator is changed to achieve the purpose of frequency modulation, which is called secondary frequency modulation. When secondary frequency modulation is set locally by power plant operators, it is called in-situ manual control.
The change of power system frequency has a direct impact on consumption rate and load distribution among power plants. For example, when the frequency changes, the generator set and auxiliary equipment deviate from the rated operating conditions, so their efficiency decreases. Power plants operate under uneconomic conditions, but also affect the economic operation of the entire power grid. When the frequency is too low, it will endanger the safe operation of the whole system.
D88尊龙Therefore, one of the main tasks of power system operation is to stop monitoring and controlling the frequency. When the input power and load power of the system unit lose balance and the frequency deviates from the rated value, the control system must adjust the output of the unit to ensure that the frequency deviation of the power system is within the allowable range (the normal allowable deviation should not exceed (+0.2Hz).
D88尊龙The adjustment of active power and frequency as well as the magnitude and speed of adjustment are accomplished by adjusting the intake of steam turbine.
D88尊龙When one or more units are used to adjust the frequency, the load distribution among the units will be changed, which will affect the economic operation of the power system. Therefore, frequency regulation is closely related to the economic distribution of power system load. When adjusting the system frequency, it is requested that the system frequency be maintained within the regular range. In addition, the system load should be allocated economically among generators.
D88尊龙完成電力系統頻率和有功功率自動控制的的系統稱為自動發電控制( Automatic Gen-eration Control，AGC)。自動發電控制系統主要由電網調度中心的能量管理系統(EMS)、電廠端的遠方終端(RTU)和分散控制系統的諧和控制系統通道三局部組成。完成自動發電控制系統閉環自動控制必需滿足以下根本請求：
D88尊龙Automatic Gen-eration Control (AGC) is a system that accomplishes automatic control of power system frequency and active power. The automatic generation control system is mainly composed of three parts: energy management system (EMS) of power grid dispatching center, remote terminal (RTU) of power plant and harmonic control system channel of decentralized control system. To complete the closed-loop automatic control of the automatic generation control system, the following basic requirements must be met:
(1) The thermodynamic automatic control system of power plant units must operate in an automatic mode, and the harmonic control system must operate in a "harmonic control" mode.
D88尊龙(2) The energy management system, microwave channel and RTU of power dispatching center must be in normal working state, and the dispatching load instructions of motor, Furnace Harmonic and control system can be changed directly from the terminal CRT of power dispatching center's energy management system. Machine and furnace harmonic control system can directly receive the "request" and "release" signals of automatic generation control and the analog signals of "dispatch load instructions" (the standard interface is 4-20 mA DC) from the energy management system. Energy management system can accept the response signals, harmonic control mode signals and AGC input signals of the unit harmonic control system.
(3) The absolute bias between the "dispatching load instruction" signal issued by the energy management system and the practical output of the power plant units must be controlled within the allowable range.
(4) Units operate in a harmonic control mode, and the load is set by the operator as in-situ control, while the load is directly controlled by the power grid dispatching center as remote control under dispatching instructions. The switching between local control and remote control is bidirectional and undisturbed. In the local control, the dispatching load instruction automatically tracks the real power of the unit; in the remote control, the output load instruction of the manual load setter of the harmonic control system automatically tracks the dispatching load instruction.
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