JP2535210B2 - Synchronous generator automatic voltage regulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention is particularly designed to maintain a high speed response of terminal voltage control even when the rotational speed and terminal voltage of a synchronous generator are largely changed. The present invention relates to an automatic voltage regulator for a synchronous generator.

(Prior Art) Synchronous generators are widely used because the terminal voltage can be easily controlled by adjusting the exciting current flowing in the field circuit. Even if the exciting current is constant, the terminal voltage is constant when the load and the rotation speed are constant, but the terminal voltage changes when the load and the rotation speed change. Therefore, an automatic voltage regulator (hereinafter referred to as AVR) is usually used to adjust the exciting current so that the terminal voltage of the generator is a desired constant value.

FIG. 6 shows a control system of such a commonly used synchronous generator, especially a brushless synchronous generator. In the figure, 1 is a synchronous generator, 2 is a rotary rectifier, 3 is an exciter, 4 is an AVR, 41 is a power converter, 42 is a voltage detector, 43 is a voltage setter, 44 is an error amplifier, and 45 is a phase control. Vessel, 46 is a transformer.

The terminal voltage control method of the conventional brushless synchronous generator will be described below with reference to FIG. The voltage setter 43 is a setter that sets the terminal voltage command signal of the synchronous generator 1.
This terminal voltage command signal, together with the terminal voltage feedback signal of the synchronous generator 1 detected by the voltage detector 42, together with the error amplifier
Entered in 44. The error amplifier 44 amplifies the error between both signals and outputs it as an excitation voltage command to the phase controller 45. The phase controller 45 gives a gate pulse to the SCR of the power converter 41 at a control angle such that the output voltage of the power converter 41 becomes a commanded value.

That is, if the terminal voltage feedback signal of the synchronous generator 1 is smaller than the value of the terminal voltage command signal, reduce the SCR control angle,
The field voltage is increased to increase the field current and increase the synchronous generator terminal voltage. On the contrary, if the terminal voltage feedback signal of the synchronous generator 1 is larger than the value of the terminal voltage command signal, the SCR control angle is increased and the field voltage is decreased to reduce the field current to reduce the terminal voltage of the synchronous generator 1. To reduce. This keeps the terminal voltage of the synchronous generator 1 constant.

One of the major points for evaluating the characteristics of the AVR is the problem of responsiveness to how quickly the generator terminal voltage returns to the command value against disturbances such as load changes.
Therefore, the error amplifier 44 has conventionally been provided with a transfer function that compensates for the delay of the synchronous generator 1 and the exciter 3.

FIG. 7 is a control block diagram of the conventional generator shown in FIG. In the figure, ▲ V ^* _g ▼ is the terminal voltage command of the synchronous generator 1, V _g is the terminal voltage of the synchronous generator 1, ΔV _g is the terminal voltage error, V _a is the excitation voltage command of the output of the error amplifier 44, and V
_fe is the field voltage of the exciter 3, V _e is the terminal voltage of the exciter 3, and V _f
Is the field voltage of the synchronous generator 1. Further, f _{1 to} f ₅ in each block represent the transfer function of each element.

Here, the transfer functions of elements other than the error amplifier 44 are shown in FIGS. 6 and 7. The conventional synchronous generator has been used to generate an AC voltage having a constant frequency and a constant voltage, so that the transfer function is as follows.
(K ₁ , K ₂ , K ₃ , and K ₄ are constants.) In the power converter 41, the voltage obtained by stepping down the terminal voltage of the synchronous generator 1 by the transformer 46 is rectified by the control angle according to the output signal of the error amplifier 44. Then, it is applied to the field of the exciter 3. Since the generator terminal voltage is almost constant, the transfer function f ₂ is as follows.

f ₂ = V _fe / V _a = K ₁ (1) In the exciter 3, the field voltage V _fe causes a field current to flow to generate a magnetic flux, and the rotation causes a terminal voltage V _{e at the} armature terminal. To do. Since the rotation speed is almost constant, the transfer function f ₃ is as follows. T _e ′ is an exciting machine field time constant, and s is a differential operator.

f ₃ = V _e / V _fe = K ₂ / (1 + T _e ′ s) (2) In the rotary rectifier 2, the AC exciter terminal voltage is rectified and converted into DC, which is applied to the field of the synchronous generator 1. Therefore, the transfer function f ₄ is as follows.

_{f 4 = V f / V e} = K 3 ... (3) In the synchronous generator 1, a magnetic flux is generated by the field current flowing through the field voltage V _f, the terminal voltage to the armature terminals by rotation
V _g is generated. Since the rotation speed is almost constant, the transfer function
f ₅ is as follows. T _do ′ is the generator field time constant.

In _{f 5 = V g / V f} = K 4 / (1 + T do 's) ... (4) control system shown in FIG. 7, is generally desirable and has been that the system system shown in equation (5) Is. ω _c is a cutoff frequency that determines the control response. Fluctuation frequency of the terminal voltage command value, the following frequency omega _c is followed by a gain 1 is the terminal voltage, in the above frequency omega _c is first-order lag system gain is reduced by 20 dB / decade.

The transfer function f ₁ of the error amplifier 44 is (5)
If determined so as to satisfy the formula, the response of the generator voltage control system can be made independent of the delay of the synchronous generator 1 and the exciter 3. That is, the transfer function f ₁ may be set as follows.

If the transfer function f ₁ is determined as in the equation (6), the terminal voltage V _g follows the change of the terminal voltage command value ▲ V ^* _g ▼ below the frequency ω _c with the gain of 1. Terminal voltage command value ▲ V ^* _g ▼
If V is kept constant, the terminal voltage V _g can be recovered with a quick response even if the terminal voltage V _g changes due to a load change or the like.

(Problems to be Solved by the Invention) Most of the conventional synchronous generators controlled as described above are used to generate a terminal voltage of constant frequency and constant voltage. Therefore, the rotation speed of the synchronous generator 1 was constant, and the power supply voltage of the power converter 41 was also substantially constant. However, recently, in order to save energy, labor, and cost, the usage of synchronous generators has been diversified, and along with this, there are cases where satisfactory performance cannot be obtained with conventional control methods. Came. That is,
When the number of revolutions of the synchronous generator greatly changes and the terminal voltage greatly changes, the transfer function of the terminal voltage control system largely changes, and the desired response cannot be obtained.

When the rotation speed of the synchronous generator 1 changes greatly, K _{2 in} the equation (2) and K ₄ in the equation (4) cannot be regarded as constants.
Since the terminal voltage of the synchronous generator 1 is proportional to the field magnetic flux, that is, the field current and the rotation speed, K ₂ and K ₄ are variables,
Expressions (7) and (8) are obtained.

K ₂ = K ₂ ′ · N (7) K ₄ = K ₄ ′ · N (8) Here, K ₂ ′ and K ₄ ′ are constants, and N is a normalized rotation speed. Therefore, V _g / V _a is given by the equation (9).

Assuming that the transfer function of the error amplifier 44 is the equation (6) as in the conventional case, V _g / ▲ V ^* _g ▼ is given by the equation (10). However, since K ₂ and K _{4 in the} equation (6) are constants, they are replaced with K ₂ ′ and K ₄ ′, respectively.

From this equation (10), it is understood that the cutoff frequency of the control system is ω _c · N ² instead of the designed frequency ω _c . It is desirable that the cutoff frequency has a constant value regardless of the conditions such as the rotation speed. However, in the control system of formula (10), when the number of revolutions of the synchronous generator becomes lower than the rated number of revolutions of N = 1 PU, the cutoff frequency lowers and the response of the terminal voltage control deteriorates. The cutoff frequency becomes high and the terminal voltage control becomes unstable,
There is a problem that it may malfunction due to noise.

Further, when the terminal voltage of the synchronous generator 1 changes greatly, the power supply voltage of the power converter 41 also changes greatly,
K _{1 in} equation (1) cannot be regarded as a constant. Since the power supply of the power converter 41 is obtained by stepping down the terminal voltage of the synchronous generator 1 by the transformer 46, K ₁ becomes a variable and is expressed by the following equation (11).

K ₁ = K ₁ ′ · AV _g (11) where K ₁ ′ is a constant and AV _g is the normalized excitation power supply voltage.

Therefore, V _g / V _a is given by equation (12).

Assuming that the transfer function of the error amplifier 44 is the equation (6) as in the conventional case, V _g / ▲ V ^* _g ▼ is given by the equation (13). However, since K _{1 in the} equation (6) is a constant, it is replaced with K ₁ ′.

From equation (13), it can be seen that the cutoff frequency of the control system is ω _c · AV _g instead of the designed value ω _c . It is desirable that the cutoff frequency be a constant value that does not depend on the number of revolutions of the synchronous generator or the excitation power supply voltage.
However, in the control system of formula (13), when the excitation power supply voltage AV _g of the synchronous generator becomes lower than the rated value of 1 PU, the cutoff frequency ω _c decreases and the response of the terminal voltage control deteriorates.
On the other hand, when it becomes higher, the cut-off frequency becomes higher and the terminal voltage control becomes unstable, or noise causes malfunction.

In the above, in the conventional control method, the characteristics when the rotation speed and the exciting power supply voltage of the synchronous generator 1 are largely changed have been described, but the control system when both are changed at the same time has a more complicated cutoff. The frequency changes and the response characteristics of the terminal voltage control system are not constant.

The applications in which the rotation speed and the terminal voltage of the synchronous generator 1 greatly change are a small hydroelectric generator and various shaft drive generators for ships and automobiles. In these applications, there is a major loop for constant power factor control that uses the terminal voltage control system of the synchronous generator 1 as a minor loop, or a device that converts the electric power of the synchronous generator 1 into constant voltage constant frequency power and its Many of them have a control system, and the response and stability performance required for such a control system have recently become sophisticated. For this reason, it is desirable that the terminal voltage control system of the synchronous generator has a response as fast as possible and stable characteristics. However, in the conventional control method, the cutoff frequency of the control system changes due to changes in the number of revolutions of the generator and the excitation power supply voltage, and this requirement cannot be satisfied.

An object of the present invention is to provide an automatic voltage regulator for a synchronous generator that can not only keep the characteristics of the terminal voltage control system stable but also keep the response at a fast value.

[Structure of Invention]

(Means for Solving Problems) The present invention relates to an automatic voltage regulator that controls a terminal voltage of a synchronous generator so as to have a value according to a terminal voltage command,
When the number of revolutions and the terminal voltage of the synchronous generator is detected and the synchronous generator is a brushless synchronous generator according to the detected signal 1 / (N ² · AV _g ) The synchronous generator with brush is synchronous generator In the case of a machine, a gain corrector with a function of 1 / (N · AV _g ) (N is the normalized rotation speed, AV _g is the normalized excitation power supply voltage) is the terminal voltage command value and the terminal voltage. By correcting the gain of amplification of the error between and, the cutoff frequency of the terminal voltage control system is kept constant and the response of the terminal voltage control system is always set to a fast constant value even if the rotation speed and the terminal voltage change significantly. It is characterized by doing.

(Operation) In the present invention, since the control gain of the terminal voltage control system is set to a constant value, the cutoff frequency can also be maintained at a constant value. As a result, not only can the characteristics of the terminal voltage control system be maintained stable, but also the response can be maintained at a fast value at all times, and the applications of the synchronous generator can be expanded.

(Example) The present invention will be described below with reference to an example shown in FIGS. 1 and 2. In FIGS. 1 and 2, the same reference numerals as those in FIGS. 6 and 7 indicate the same components. Further, 47 is a rotation speed detector, and 48 is a gain corrector. Further, V _c is the output signal of the gain corrector 48, and N is the rotation speed of the synchronous generator 1. FIG. 3 shows the characteristics of the shaft generator of the ship shaft drive generator as an example in which the rotational speed of the synchronous generator and the excitation power supply voltage greatly change. The rotation speed changes arbitrarily from N ₁ to N ₃ . The terminal voltage has a fixed pattern with respect to the number of revolutions.From N ₁ to N ₂ , a voltage proportional to the number of revolutions is given, and from N ₂ to N ₃ , a constant voltage is given as the terminal voltage command ▲ V ^* _g ▼. To be

Hereinafter, the automatic voltage adjustment method for the synchronous generator (brushless synchronous generator) of the present invention will be described with reference to FIGS. 1, 2, and 3. V _g / V _a in the case where the rotation speed N of the synchronous generator 1 largely changes is expressed by the equation (9). In addition, when the terminal voltage V _g of the synchronous generator 1 changes greatly
V _g / V _a is given by equation (12). From equations (9) and (12), the transfer function V _g / V _a of the controlled system when both the rotation speed and the terminal voltage change greatly as shown in Fig. 3 is obtained (14),
It becomes like the formula (15).

G ₁ = (K ₁ ′ .K ₂ ′ · K ₃ · K ₄ ′) · N ² · AV _g (15) As can be seen from the equation (15), the gain G ₁ is proportional to N ² and AV _g . . The highest gain G ₁ can be found in Fig. 3 where
Point C where the terminal voltage is the highest. The gain G ₁ is the smallest at the point A where the rotation speed and the terminal voltage are the smallest. In the example of FIG. 3, at points C and A, the gain becomes 1/9 due to the change in the number of revolutions and 1/2 due to the change in the terminal voltage, resulting in 1/18 in total.

The error amplification transfer function for making the system shown in equations (14) and (15) the desired system shown in equation (5) is (16),
It is shown in (17).

G ₂ = ω _c / ((K ₁ ′ ・ K ₂ ′ ・ K ₃・ K ₄ ′) ・ N ²・ AV _g ) ...
(17) G ₂ according to Eq. (17) is corrected by correcting the N ² term and AV _g term of G ₁ in Eq. (15) to keep the overall gain constant at ω _c even if N or V _g changes. To do.

Comparing equations (6) and (16), the s term is the same, so if the gain is corrected so as to satisfy equation (17), the desired error expressed by equations (16) and (17) It can be amplified. For this purpose, as shown in FIG.
A gain corrector having a predetermined transfer function f ₆ may be added to the control system in series with the error amplifier 44. f ₆ becomes the function shown in the expression (18) by comparing the expression (6) with the expressions (16) and (17).

f ₆ = V _c / ΔV _g = 1 / (N ² · AV _g ) ... (18) FIG. 1 shows a circuit that realizes this. Gain corrector 48
Calculates the difference ΔV _g between the terminal voltage command signal ▲ V ^* _g ▼ and the terminal voltage feedback signal V _g by the gain correction of the equation (18) to obtain V _c . The error amplifier 44 obtains V _a by amplifying V _c according to the equation (6) as in the conventional case. In the following, as in the conventional method, the exciter field current is adjusted by the phase controller 45 and the power converter 41 to keep the generator voltage constant.

FIG. 4 shows the gain G ₁ of the transfer function of the controlled system, the gain G ₂ of the transfer function of the control system, and the gain G of the entire system, which is a combination of the _two , of the synchronous generator having the characteristics shown in FIG. is a diagram showing characteristics of ₁ · G _2. Gain of the entire system in all areas
G ₁ and G ₂ are constant. As a result, the cutoff frequency of the terminal voltage control can be kept constant even if the rotation speed of the synchronous generator 1 and the terminal voltage change.

(Other Embodiment) Next, another embodiment of the present invention is shown in FIG. This example
This is a system with a brushless synchronous generator in which the field of the synchronous generator 1 is directly excited by the output of the power converter 41 without using the exciter 3 and the rotary rectifier 2 in the example of FIG. in this case,
The transfer function of the controlled system is as shown in Eqs. (19) and (20).

G ₁ = (K ₁ ′ · K ₄ ′) · N · AV _g (20) Therefore, the transfer function of the gain compensator 48 is expressed by the equation (21), and the transfer function of the error amplifier 44 is expressed by the equation (22). You can do it like this.

V _c / ΔV _g = 1 / (N · AV _g )… (21) As a result, as in the example of FIG. 1, the cutoff frequency of the terminal voltage control system is a constant frequency ω that is not affected by the delay of the synchronous generator 1, the rotation speed, or the change of the excitation power supply voltage. It can be controlled with _c .

Further, in the above description, the correction gain is described as being calculated, but a function generator that generates a signal of a given formula may be used. An approximate expression may be used as the content of the function according to the required performance and accuracy.

In both the examples of FIGS. 1 and 5, the control is performed by the hardware of the analog circuit. However, the realizing means of the present invention is not limited to this, and a software program may be used by using a microcomputer or the like. You may go by

〔The invention's effect〕

According to the present invention, in the exciter for a synchronous generator, the gain of the terminal voltage control system is kept constant and the cutoff frequency is not changed even if the rotational speed of the synchronous generator or the excitation power supply voltage changes significantly. As a result, the response of the terminal voltage control system can be always set to a fast constant value. Therefore, control characteristics can be greatly improved and applications can be expanded in applications in which the rotational speed of the synchronous generator and the excitation power supply voltage change greatly, for example, small hydroelectric generators and various shaft drive generators for ships and automobiles. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an automatic voltage regulator for a synchronous generator of the present invention, FIG. 2 is a control block diagram of the automatic voltage regulator of the present invention, and FIG. 3 is a synchronization for explaining the operation of the present invention. FIG. 4 is a characteristic diagram of a generator, FIG. 4 is a characteristic diagram of a control system for explaining the operation of the present invention, FIG. 5 is a block diagram showing another embodiment of the present invention, and FIG. 6 is a conventional synchronous power generation. FIG. 7 is a configuration diagram showing a control system of the machine, and FIG. 7 is a control block diagram showing an automatic voltage regulator. 1 …… Synchronous generator, 2 …… Rotary rectifier 3 …… Exciter, 4 …… AVR 41 …… Power converter, 42 …… Voltage detector 43 …… Voltage setter, 44 …… Error amplifier 45 …… Phase controller, 46 ... Transformer 47 ... Rotation speed detector, 48 ... Gain corrector

Claims (1)

(57) [Claims] 1. An automatic voltage regulator for controlling the terminal voltage of a synchronous generator to a value according to a terminal voltage command value, detecting the rotational speed and the terminal voltage of the synchronous generator,
According to the detected signal, when the synchronous generator is a brushless synchronous generator 1 / (N ² · AV _g ) When the synchronous generator is a brushed synchronous generator 1 / (N · AV _g ) (N is Normalized rotation speed, AV _g is the normalized excitation power supply voltage) With a gain corrector having a function, rotation is performed by correcting the gain of amplification of the error between the terminal voltage command value and the terminal voltage. The automatic voltage regulator for a synchronous generator characterized in that the cutoff frequency of the terminal voltage control system is kept constant and the response of the terminal voltage control system is always a fast constant value even if the number and the terminal voltage change significantly. .