JPH0265699A - Automatic voltage regulating method for synchronous generator - Google Patents

Abstract

PURPOSE:To cope with variations in an output voltage and a frequency by detecting the rotating speed of a synchronous generator and a terminal voltage and correcting a gain by a corrector having a function of 1/(N<2>.AVg) [where N, AVg are normalized rotating speed, terminal voltage]. CONSTITUTION:The output voltage of a synchronous generator 1 is detected by a detector 42, compared with the voltage of a voltage setter 42, input to a gain corrector 48, its rotating speed is detected by a detector 47, and input to the corrector 48. The corrector 48 is of a corrector having characteristics including a function of 1/(N<2>.AVg), error-amplifies its output by an error amplifier 44, controls its phase by a controller 45 to control the gate pulse of a power converter 41. The converter 41 supplies a DC obtained by converting the AC output of a transformer 46 to an exciter 3. The output of the exciter 3 is rotatably rectified by a rectifier 2, and supplied to the exciting coil of the generator 1. Thus, the cut-off frequency of a terminal voltage control system is maintained constantly, and even if a terminal voltage and a frequency are largely varied, a correction having a high response is conducted. This is adapted for a generator for a small hydraulic generator, an automobile or a ship.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Field of Industrial Application) The present invention is designed to maintain a fast response of terminal voltage control even if the rotational speed or terminal voltage of a synchronous generator changes significantly. Departing at the same time? ! ! Regarding automatic voltage WR* method of machine.

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

FIG. 6 shows a control system for such a commonly used synchronous generator, particularly a brushless synchronous generator. In the figure, 1 is a synchronous generator, 2 is a rotating 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, 45 is a phase controller, and 46 is a transformer.

Below, according to Fig. 6, the conventional brushless synchronous generator 1! The machine control method will be explained. The voltage setting device 43 is a setting device that sets a terminal voltage command signal on the synchronous generator.

This terminal voltage command signal is input to the error amplifier 44 together with the terminal voltage feedback signal of the synchronous generator 1 detected by the voltage detector 42 .

The error amplifier 44 amplifies the error between both signals and outputs it as an excitation voltage command to the phase controller 45.
gives a gate pulse to the SCH of the power converter 41 at a control angle such that the output voltage of the power converter 41 becomes the commanded value.

In other words, if the terminal voltage feedback signal of the synchronous generator 1 is smaller than the value of the terminal voltage command signal, the SCR control angle is reduced,
The field voltage is increased, the field 8i current is increased, and the synchronous generator terminal voltage is increased. Conversely, if the terminal voltage feedback signal of the synchronous generator 1 is larger than the value of the terminal voltage command signal, the SC
The terminal voltage of the synchronous generator 1 is reduced by increasing the R control angle and decreasing the field voltage to reduce the field current. This keeps the terminal voltage of the synchronous generator 1 constant.

A major point in evaluating the characteristics of the AVR is the issue of responsiveness, which is how quickly the generator terminal voltage can be returned to the command value in response to 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. 6, where vg is the terminal voltage command of the synchronous generator 1, ■ is the terminal voltage on the synchronous generator, is the terminal voltage error, va is the excitation voltage command of the output of the error amplifier 44,
Vfe is the field voltage of the exciter 3, v8 is the terminal voltage of the exciter 3, and Vf is the field voltage of the synchronous generator 1. Furthermore, f, ~f in each block indicates 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. Conventional synchronous generators have been used to generate alternating current voltage with constant frequency and constant voltage, so the transfer function is as follows. (
K□, K2. K□, 4 is a constant. ) 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 at an angle controlled by the output signal of the error amplifier 44, and is applied to the field of the exciter 3. Since the generator terminal voltage is approximately constant, the transfer function f2 is as follows.

fz ” Vfe/Va = Kt
.=■ In the exciter 3, magnetic flux is generated by the field current flowing due to the field voltage Vfe, and a terminal voltage v8 is generated at the armature terminal by one rotation. Since the rotation speed is approximately constant, the transfer function f3 is as follows. Toi:l: exciter field time constant, S is a differential operator.

L=Ve/Vfe=K,/(1+choes)
``'■ The rotary rectifier 2 rectifies the alternating current exciter terminal voltage to convert it into direct current, which is applied to the field of the synchronous generator 1.

Therefore, the transfer function f4 is as follows.

f4=Vf/Vo=Kz
.=■Synchronous generator], a magnetic flux is generated by the field current flowing due to the field voltage V[, and a terminal voltage vg is generated at the armature terminal due to rotation. Since the rotational speed is approximately constant, the transfer function f is as follows. Td.

is the generator field time constant.

fs=vg/vr=to*/(1+Tdos) -Q
) Among the control systems shown in FIG. 7, the system that is generally considered desirable is the system shown by equation 0.

ω. is the cutoff frequency that determines the control response. When the fluctuation frequency of the terminal voltage command value is below the frequency ωC, the terminal voltage follows the frequency ω with a gain of 1. Above is 20d
It is a first-order lag system in which the gain decreases by B/decade.

Vg/V = 1/(1000s/ω.)...
If the transfer function f□ of the error amplifier 44 is 0, then the entire transfer function is 0.
If the equation is determined, 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 transmission function f1 may be set as follows.

f, = Va/ΔV&= c, +c/s/ (f z・f
x・f 4・f s)...■ If the transfer function f is determined as in equation 0, the frequency ω.

For the following changes in the terminal voltage command value Vg, the terminal voltage ■
is followed with a gain of 1. If the terminal voltage command value Vζ is kept constant, even if the terminal voltage V changes due to load changes, etc.
The terminal voltage vg can be recovered with a quick response.

(Problem layer to be solved by the invention) The conventional synchronous generator controlled as described above has a constant frequency,
Most of them were used to generate constant terminal voltage. Therefore, the rotational speed of the synchronous generator 1 was constant, and the electric g voltage of the power converter 41 was also almost constant. however.

Recently, in order to save energy, labor, and cost,
The ways in which synchronous generators are used are diversifying, and as a result, there are cases in which conventional control methods cannot provide satisfactory performance. Namely.

When the rotational speed of the synchronous generator changes greatly, or when the terminal voltage changes greatly, the transfer function of the terminal voltage control system changes greatly, making it impossible to obtain the desired response.

If the rotation speed of synchronous generator 1 changes significantly, use 2 of type 0.
．． 4 in the equation cannot be considered as a constant. Since the terminal voltage of the synchronous generator] is proportional to the field magnetic flux, that is, the field current and the rotation speed, K2. K4 becomes a variable,
It will look like the formula ■,■.

K, = K, ・N K4= K4・N ・■ ...(8) Here, 2. , is a constant, and N is the normalized number of rotations. Therefore, Vg/Va becomes as shown in equation 0).

If the transfer function of the error amplifier 44 is set to the equation 0 as in the conventional case, then V/Vg becomes as shown in equation (10). However, 2. Since K is a constant, ', K4
'bReplace this.

From this equation (10), the cutoff frequency of the control system is:

Design value frequency ω. Not ω. - It can be seen that it is N2. It is desirable that the cutoff frequency be a constant value regardless of conditions such as the number of rotations.

However, in the control system of the formula (1O), when the rotational speed of the synchronous generator becomes lower than the rated rotational speed of N=I P,U.

When the cutoff frequency decreases, the response of terminal voltage control deteriorates, and conversely, when it increases, the cutoff frequency becomes high, causing problems such as unstable terminal voltage control and malfunction due to noise.

Also, if the terminal voltage of synchronous power generation 4!11 changes greatly, 1! Since the power supply voltage of the force transducer 41 also changes greatly, 1 in equation 1,0) cannot be regarded as a constant. Since the power source of the power converter 41 is obtained by stepping down the terminal voltage of the synchronous generator 1 with the transformer 46, K1 becomes a variable and is expressed as the following equation (11).

K, = KL-AVg (11) Here, is a constant, and AVg is a normalized terminal voltage.

Therefore, VE/Va becomes as shown in equation (12).

If the transfer function of the error amplifier 44 is set as the conventional equation (0), then Vg/V is as shown in equation (13).However, 0
Since Ki in the formula is a constant, replace it with □.

From equation (13), the cutoff frequency of the control system is the design value ω. Not ω.・You can see that it is AVg. The cutoff frequency depends not only on the rotation speed of the synchronous generator, but also on the
It is desirable that it be a constant value that does not depend on the terminal voltage.

However, in the control system of equation 13), the terminal voltage rotation speed AVg of the synchronous generator is IP, U.

When the cutoff frequency ω becomes lower than the rated value.

If the voltage decreases, the response of terminal voltage control becomes poor, and if the voltage increases, the cutoff frequency increases, making terminal voltage control unstable or causing malfunctions due to noise.

Above, in the conventional control system, we have described the characteristics when the rotation speed and terminal voltage of the synchronous generator 1 change greatly, but the control system when both change simultaneously is more complicated and the cutoff frequency changes. As a result, the response characteristics of the terminal voltage control system are not constant.

Applications in which the rotational speed and terminal voltage of the synchronous generator 1 vary greatly include small hydroelectric generators and various shaft drive generators for ships and automobiles. In these applications, the terminal voltage control system of the synchronous generator 1 has a major loop of constant power factor control with a minor loop, and a device and its Many have control systems.

The performance of response and stability required for such control systems is also
Recently, it has become more advanced. For this reason, it is desirable that the terminal voltage control system of the synchronous generator has as fast a response as possible and stable characteristics. However, in the conventional control method, the cutoff frequency of the control system changes due to changes in the rotational speed of the generator and the terminal voltage, and this requirement cannot be satisfied.

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

[Structure of the invention]

(Means for solving the zero-time problem) The automatic voltage adjustment method for a synchronous generator of the present invention includes an automatic voltage adjustment device that controls the terminal voltage of the synchronous generator to a value corresponding to a terminal voltage command value. The number of revolutions and terminal voltage of the synchronous generator are detected, and according to the detected signals, if the synchronous generator is a brushless synchronous generator, 1/(N2・AVg). 1/(N
-AVg) (N is the normalized rotation speed, AVg is the normalized terminal voltage). The present invention is characterized in that the cutoff frequency of the terminal voltage control system is kept constant even if the rotational speed and the terminal voltage change greatly, and the response of the terminal voltage control system is always kept at a fast constant value.

(Function) In the present invention, since the control gain of the terminal voltage control system is kept at a constant value, the cutoff frequency can also be kept at a constant value. This not only allows the characteristics of the terminal voltage control system to be kept stable, but also allows the response to always be kept at a fast value, expanding the range of applications for synchronous generators.

(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 numbers as in FIGS. 6 and 7 indicate the same components. Also, 47 is a rotation speed detector.

48 is a gain corrector. Further, vo 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 a shaft generator of a shaft drive generator for a ship, as an example in which the rotational speed and terminal voltage of the synchronous generator vary greatly. The number of rotations changes arbitrarily from N to N.

The terminal voltage has a fixed pattern with respect to the rotation speed, and N□
From to N2.

From N2 to N, a constant voltage is given as the terminal voltage command vg, which is proportional to the rotational speed.

The automatic voltage s1 adjustment method for a synchronous generator (brushless synchronous generator) according to the present invention will be explained below with reference to FIGS. 1, 2, and 3. When the rotational speed N of the synchronous generator 1 changes significantly, V g /V a is expressed as in equation (9). Further, when the terminal voltage vg of the synchronous generator 1 changes greatly, Vg/Va becomes as shown in equation (12). (2) From equation (12), when the transfer function V of the controlled system is determined to be /va when both the rotational speed and the terminal voltage change greatly as shown in FIG. 3, equations (14) and (15) are obtained.

G Uni (K1・N2・K,・N4)・N2・Av...
- (15) As can be seen from equation (15), the gain G is proportional to N2 and AVg. The gain G is highest at the 6 points in Figure 3 where the rotational speed and terminal voltage are the highest.

The gain G is the smallest at point A, where the rotational speed and the terminal voltage are the smallest. In the example of FIG. 3, at points 6 and A, the gain is reduced to 1/9 due to the change in rotational speed, and to 1/2 due to the change in terminal voltage, resulting in a total of 1/18.

(+4), the transfer function of error amplification to transform the system expressed by equation (15) into the desired system expressed by equation 0 is expressed as (16)
.

It is shown in equation (17).

v, /ΔVg=G, , (1+Ts') °(1
+ Tdo s )...(16) Gz = ωc/ ((Kt ' Kz ” Kl ・
N4) ・N2・AVg) G2 according to formula (17) is
By correcting G, (7) N2 term, and AVg term in Equation (15), the overall gain is kept constant at ωC even if N and vg change. (Comparing Equation 0 and Equation (16), Since the 5th term is the same, if the gain is corrected to satisfy equation (17), it is possible to obtain the desired error amplification expressed by equations (1, 6) and (17). , in series with the error amplifier 44, as shown in FIG.
Just add a gain corrector with this to the control system.
From the comparison of equations 0, (16), and (17), fG is calculated as (1
8) It becomes the function shown in Eq.

f5= Vo/ΔVg = 1/(N2・AVg)
-(18) A circuit that realizes this is shown in FIG. The gain corrector 48 performs a gain correction using equation (18) on the difference between the terminal voltage command signal V and the terminal voltage feedback signal vg, which is 67 g.
Get C. The error amplifier 44 amplifies VC according to the conventional formula to obtain Va. Thereafter, as in the conventional system, the exciter field current is adjusted by the one-phase controller 45 and the power converter 4 to keep the generator voltage constant.

FIG. 4 shows the gain G of the transfer function of the controlled system and the gain G2 of the control system transfer function of a synchronous generator with the characteristics as shown in FIG. and the gain G of the entire system combining both
2 is a diagram showing the characteristics of No. 2. In the entire region, the gains G1 and G2 of the entire system are constant. Thereby, even if the rotational speed of the synchronous generator 1 and the terminal voltage change, the cutoff frequency of the terminal voltage control can always be kept constant.

(Other Embodiments) Next, another embodiment of the present invention is shown in FIG. This example is a brush synchronous generator system in which the field of the synchronous generator 1 is directly excited by the output of the power converter 41 without using the exciter 31 rotating rectifier 2 of the example shown in FIG. In this case, the transfer function of the controlled system is as shown in equations (19) and (20).

G, = (K1・K,)・N−AVg・
(20) Therefore, the transfer function of the gain corrector 48 is (
As shown in equation (21), the transfer function of the error amplifier 44 may be set as shown in equation (22).

V, /△Vg = 1 / (N-AVg)
-(21) As a result, the cutoff frequency of the terminal voltage control system is constant, unaffected by the delay of the synchronous generator 1, the rotation speed, and changes in the terminal voltage, as in the example shown in Figure 1. frequency ω. It can be controlled by

Further, in the above explanation, the correction gain is described as being obtained by calculation, but a function generator that generates a signal according to a given formula may be used. Approximate expressions may be used for the contents of the function depending on the required performance and accuracy.

In both the examples of FIG. 1 and FIG. 5, control is performed using analog circuit hardware, but the means for realizing the present invention is not limited to this, and a software program using a microcomputer etc. is shown. Depending on the situation, you may go.

〔Effect of the invention〕

According to the present invention, in the excitation device 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 or terminal voltage of the synchronous generator changes greatly. Thereby, the response of the terminal voltage control system can always be maintained at a fast constant value.

Therefore, the control characteristics can be greatly improved in applications where the rotation speed and terminal voltage of the synchronous generator vary greatly, such as small hydroelectric generators and various shaft drive generators for ships and automobiles.
Applications can be expanded.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an automatic voltage regulator to which the automatic voltage adjustment method for a synchronous generator of the present invention is applied; FIG. 2 is a control block diagram to which the automatic voltage adjustment method of the present invention is applied;
FIG. 3 is a characteristic diagram of a synchronous generator for explaining the present invention in detail, FIG. 4 is a characteristic diagram of a control system for explaining the present invention in detail, and FIG. 5 is another embodiment of the present invention. FIG. 6 is a block diagram showing a control system of a conventional synchronous generator, and FIG. 7 is a control block diagram showing a white ljJ voltage regulator. 1...Synchronous generator 2...Rotating rectifier 3...
Exciter 4...AVR41...Power converter 42...Voltage detector 43...Voltage setting device
44...Error amplifier 45...Phase controller 4
6...Transformer 47...Rotation speed detector 48...
・Gain corrector representative Patent attorney Yoshiaki Inomata (and 1 other person)
Figure Figure Figure

Claims (1)

[Scope of Claims] An automatic voltage regulator that controls the terminal voltage of a synchronous generator to a value corresponding to a terminal voltage command value, detects the rotation speed and terminal voltage of the synchronous generator, and detects the rotation speed and terminal voltage of the synchronous generator. If the synchronous generator is a brushless synchronous generator, 1/(N^2・AV_g) If the synchronous generator is a brushless synchronous generator, 1/(N
・AV_g) (N is the normalized rotation speed, AV_g is the normalized terminal voltage) by correcting the error between the terminal voltage command value and the terminal voltage. An automatic voltage adjustment method for a synchronous generator characterized by keeping the cutoff frequency of the terminal voltage control system constant even if the number and terminal voltage change greatly, and making the response of the terminal voltage control system always fast and constant. .