The necessity of generator phase operation

The ultra long distance transmission network is expanding, which leads to the increase of reactive power, such as 220kV, 330kV and 500kV overhead lines, and the capacity and reactive power per kilometer to the ground are 130kvar, 400kvar and 1000 ~ 1300kvar respectively. In addition, in order to make up for the lack of reactive power during the peak load, a certain number of capacitors are installed in the power grid. These capacitors are sometimes hard to adjust to the voltage of the system and switch in time. Therefore, in the holidays or midnight system load is low, the excess reactive power will cause the voltage rise, even exceed the specified operating voltage allowable value, not only affects the voltage quality of power supply, but also increase the power loss, economic decline. Motor generator underexcitation '>' > '> motor generator underexcitation can absorb reactive power network surplus, reducing system voltage. Motor generator underexcitation '>' > '> motor generator underexcitation is combined with the power production needs the feasible operation technology, it can make the motor by changing the operating conditions of generator' > and achieve the aim of reducing blood pressure. Only by means of a voltage regulating method added to the existing equipment of the system, the regulating range of the system voltage can be enlarged, and the operation condition of the voltage of the network can be improved. This method is simple, the motor generator underexcitation '>' > '> motor generator underexcitation within the limit of its reliable operation, stepless voltage regulation, voltage regulation showed its flexibility, the motor generator underexcitation' > '>' > motor generator leading phase operation is the most effective necessary for improving the power quality and one of the economic measures.

The basic principle of motor generator underexcitation '>' > '> to operate in a motor generator:

Motor generator '> normal operation, but also provide reactive power to the system for active at the same time, a stator current lag angle in such a state that the terminal voltage of late phase operation. When the excitation current of the motor is gradually reduced from the generator to provide' > reactive and into the system from absorbing reactive power, stator current from behind for a point ahead of the motor terminal voltage of generator is' > this state, running in phase. The motor generator underexcitation '> underexcitation' > '> when the electrical parameters of generator motor is symmetrical, and the motor generator' > remains synchronous speed, but because the operation belongs to a normal operation mode of motor generator power in '> the only factor changes, broaden the operating range of the motor generator is' >. Similarly, within the allowable limits of the incoming phase, as long as the power grid needs can be long-term operation.

Synchronous motor generator in low power '> case excitation operation, the motor generator can' > run synchronously, and absorb reactive power, but the stator voltage drop. Low power motor generator '> excitation operation depends on the reaction torque maintain synchronous operation, the electromagnetic power consists of two parts, namely basic electromagnetic power and additional electromagnetic power, the electromagnetic power is decided by the excitation current, additional electromagnetic power is determined by the rotor salient pole effect. When the excitation is lost in operation, the electromagnetic power has only additional electromagnetic power, and the maximum value is

The salient pole motor generator '> Xd > Xq, P2m > 0 so; when the active power is very small, the electromagnetic power is sufficient to overcome the brake torque and the driving motor generator and grid sync' >. Practice has proved that the electromagnetic response about power in the excitation operation when the salient pole motor generator can reach the rated capacity of '> 20%, i.e. motor generator with power 20%Pn' > excitation operation not out of step. At this point, the rotor winding has no direct current and keeps synchronous state. Therefore, the rotor winding and its components do not induce current, so there is no rotor heating problem. In

Limiting factors of motor generator underexcitation '>' > the underexcitation '> 3 motor generator

Motor generator underexcitation '>' > '> motor generator underexcitation will be influenced by the following factors: the motor generator' > the static stability and dynamic stability limit; the motor '> generator transient and dynamic stability limit; the low excitation limit instability. In

Experimental work of 4 phase operation test

Motor generator underexcitation '>' > '> motor generator underexcitation main research work are as follows.

4.1, the reactive power meter of each test power plant has been reformed

Motor generator underexcitation '> underexcitation' > '> motor generator, motor generator' > absorption system of inductive reactive power, reactive power and negative power factor angle changed from positive to negative, the power factor is bidirectional. In the past, the reactive power meters in the power plants were one-way, and the power factor meter was not installed, so the one-way reactive power factor meter was modified.

Voltage stability and leading phase operation of motor generator reactive '>' > results underexcitation '> 4.2 motor generator

'> motor generator leading phase test should be conducted in the system load is low and high voltage, using a small way of normal operation of Sichuan power grid under the calculation, in order to improve the motor power generators is' >' > depth, to reduce the influence of motor generator terminal voltage of the phase depth, the power plant transformer joint is scheduled for 4 stalls.

In the motor generator underexcitation '>' > '> motor generator test on the stability limit and reactive voltage calculated phase operation. By calculation, each motor generator '> static stability limit is relatively deep, the transient stability limit slightly shallower than the static stability limit, motor generator' > phase in the transient stability limit range will be reduced to system voltage range, the antihypertensive effect is very significant.

Asynchronous operation of 4.3 motor generators' > mechanism and phenomena and treatment measures