JPH0768938B2 - Variable speed power generation system - Google Patents

Description

The present invention relates to a variable speed power generation system using an AC excitation type variable speed power generator, and particularly to a variable speed power generation suitable for a power generation system using a water turbine as a prime mover. Regarding the control method of the system.

[Conventional technology]

In turbine systems, especially pumped-storage power generation systems that use pump turbines, it may be desirable to operate the turbine at variable speeds independently of the frequency of the power system to which they are connected. With the development of electronics and control technology, it has come to be embodied in the form of realizing various variable speed power generation systems, particularly power generation systems using turbines as prime movers, or variable speed pumped storage power generation systems using pump turbines. .

By the way, as this type of conventional technology, for example, there is a variable speed power generation system disclosed in Vol.68 (1986) p.653 to 658 of "Hitachi Commentary". As shown in FIG. 4, the conventional technique includes an AC excitation type variable speed generator 1 connected to an AC power system, and the variable speed generator 1 is directly connected to the turbine 3.
It is driven as a prime mover and supplies power to the AC power system.

The variable speed generator 1 is adapted to be excited by a three-phase alternating current I ₂ having a frequency independent of the power system, which is supplied from the power system via the transformer 5 and the sanacro converter 7. This allows it to function as a variable speed generator. The exciting current I ₂ is supplied to the rotor of the variable speed generator 1 via the collector ring 6.

Further, a phase detector 2 is directly connected to the variable speed generator 1, so that the difference between the rotor phase of the variable speed generator 1 and the voltage phase of the power system can be detected. The voltage phase of the power system at this time is detected by the voltage detector 4 and input to the phase detector 2.

The cycloconverter 7 is controlled by the current command generator 9, so that a predetermined AC exciting current I ₂ is generated in the variable speed generator 1.
Therefore, the current command generator 9 outputs the phase difference data input from the phase detector 2,
d-axis current command value ID ^* from the d-axis component current command generator 13,
The q-axis current command value Iq ^* given from the q-axis current command generator 15 is used to calculate the current command value I ₂ ^* , which is input to the cycloconverter 7.

On the other hand, in parallel with this, the water turbine 3 on the motor side controls the guide vanes 17 via the speed governor 19 and the servo system 18 based on the signal from the water turbine rotation speed adjustment signal generator 22,
The speed is controlled to a predetermined rotation speed N.

[Problems to be solved by the invention]

By the way, in such a variable speed power generation system, the rotation speed of the variable speed generator 1 is controlled by the guide vanes 17 of the water turbine 3.
Therefore, the effect of suppressing fluctuations in rotation speed cannot be expected so much.

The reason is that this system is intended for variable speed operation in the first place. Therefore, even if the phase of the rotor of the variable speed generator 1 changes due to fluctuations in the rotation speed, This is because it is represented as a change in the exciting current I ₂ by the output and automatically follows the rotation speed fluctuation, and as a result, a braking force with respect to the rotation speed fluctuation is hardly generated.

On the other hand, in such a turbine power generation system, vibration, that is, so-called central whirl vibration, is likely to occur in the turbine during partial load. At this time, however, in the variable speed power generation system, as described above, the braking force with respect to the rotation speed fluctuation is abnormal. When this whirl vibration occurs, it causes water pressure pulsation, which results in pulsation of the water turbine torque. As a result, as shown in FIG. There is a risk of destruction of the. In addition,
In FIG. 7, ΔH represents water pressure fluctuation and N represents rotational speed.

However, in the above-mentioned conventional technology, such a central
No consideration was given to whirl vibration, and there was a problem with drivability.

On the other hand, this vibration problem may be dealt with by controlling the active power of the variable speed generator, but in this case,
Due to the gain limitation in the control system, a sufficient response cannot be obtained,
There is a problem in that it is difficult to suppress such short-cycle vibrations, which may cause adverse effects such as pulsation of electric power.

It is an object of the invention as set forth in claim 1 to provide a variable speed power generation system capable of always maintaining a stable rotation speed regardless of the load condition and making full use of the advantages of variable speed operation. That is.

Further, the object of the invention described in claim 2 is to provide a variable speed power generation system in which the cycloconverter is applied to the invention described in claim 1 to further improve the cost and control stability. Is to provide.

[Means for solving problems]

The object of the invention described in claim 1 is to control in the variable speed power generation system so that the frequency of the alternating current of the variable speed generator is kept constant in a partial load region where unstable vibration may occur. It is achieved by

The object of the invention as set forth in claim 2 is to energize the variable speed power generation system so as to keep the frequency of the alternating-current excitation current of the variable speed generator constant in a partial load region where unstable vibration may occur. In what you did,
This is achieved by using a cycle converter to generate the alternating excitation current.

[Action]

According to the invention of claim 1, there is a region in which the frequency of the alternating-current exciting current of the variable-speed generator is kept constant.
The variable speed generator will operate as a synchronous machine, and will be operated at a constant speed at a rotation speed determined by the difference between the frequency of the power system and the frequency of the alternating excitation current at this time.
As a result, the same synchronization torque as that of a normal synchronous machine is generated with respect to the rotational phase change of the rotor, that is, the variation of the rotational speed, a large braking force appears, and unstable vibration due to central whirl vibration etc. is sufficiently generated. The effect of suppressing to

Further, according to the invention of claim 2, since the alternating excitation current is supplied by the cycloconverter, it is more advantageous in terms of cost and control stability.

〔Example〕

Hereinafter, the compound transmission power generation system according to the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 shows an embodiment of the present invention. In the figure, 23 is an AC system, 1 is a variable speed generator connected to the AC system 23, 2 is a phase detector, and the current pressure phase of the AC system 23 can be changed. Variable speed generator 1
The slip phase equal to the difference from the rotation angle expressed by the electrical angle of is detected. The rotor of the phase detector 2 is connected to the rotary shaft of the variable speed generator 1, and a three-phase winding connected in parallel with the primary winding of the variable speed generator 1 is provided on the rotor side. Has been. On the other hand, on the stator side of the phase detector, one Hall converter is provided at a position where the phase is different by π / 2 in terms of electrical angle, and the Hall converter of the AC system 23 seen from the secondary side of the variable speed generator 1 is provided. A signal cosθ whose phase matches the voltage and π /
A signal sin θ having a phase difference of 2 is detected by the Hall converter.

11 frequency generator, and 12 is a switching unit, the signal cosθ from the phase detector 2, sin [theta and a constant frequency signal cos .omega _o t that is generated by the frequency generator 11, sin .omega _o t and the switching equipment 1
It is input to the current command generator 9 via 2. Accordance connexion, the current command generator 9, the signal cosθ and sin [theta, and signal cosω _o t, sinω _o t both one signal selected from the are summer as supplied.

A d-axis component current command generator 13 is a d-axis component command command based on the deviation between the detected value V of the voltage effective value in the AC system 23 and the reactive voltage setting value V _o externally set by the operator. Generates the value Id ^* . This d-axis component current command value Id
^* Is a component of the secondary current of the variable speed generator 1 that differs in phase by π / 2 in electrical angle from the voltage phase of the AC system 23 when viewed from the primary side (hereinafter abbreviated as d-axis component) Is a command value for, and is a DC value in a steady state. By the way, as the two-axis component current command generator 13, for example,
The command value Id ^* may be generated according to the deviation between the reactive power output of the variable speed generator 1 and the set value for the reactive power output.

Reference numeral 15 is a q-axis component current command generator, which generates a q-axis component current command value I _q ^* from a deviation between the output detection value P of the AC system 23 and an effective travel set value P _o set by an operator from outside. .
The q-axis component current command value is Iq ^*, which is a component of the secondary current of the variable speed generator 1 that is equal to the voltage phase of the AC system 23 when viewed from the primary side (hereinafter abbreviated as q-axis component). ), The direct current value is shown in a steady state. As the q-axis component current command generator 15, for example, the command value of the previous period is set according to the deviation between the output value P and the torque of the variable speed generator 1, the rotation speed, or the frequency of the AC system 23. It may also generate I _q ^* .

14 is a switching device and 16 is a constant q-axis component generator.
Has a function of selecting one of the output signal of the q-axis component current command generator 15 and the output signal of the constant q-axis component generator 16 and extracting it as the q-axis component current command value I _q ^* .

The above-mentioned current command generator 9 uses the signals cos θ, sin θ from the phase detector 2 selected by the switch 12 or the frequency generator 11
Signal from the cosω _o t, using any one of the signal of sinω _o t,
The signal output I _q ^* and d by either the q-axis component current command generator 15 or the constant q-axis component generator 16 selected by the switcher 14
Variable speed generator 1 based on the output I _d ^{* of the} axis component current command generator 13
The secondary side current command values I _a ^* , I _b ^* , I _c ^* of the calculation formula (1)
Calculate with. However, K is a constant.

FIG. 2 shows a detailed circuit configuration example of the current command generator 9 K = 1.
I will show the case of. In this configuration example, multipliers 8a~8d and secondary current command value using the amplifier _{^{25a~25j I a *, I b *}} , I c *
Is calculated.

The cycloconverter 7 receives AC power from the AC system 23 via the power receiving transformer 5, and the AC exciting current I ₂ of each phase on the secondary side 2 of the variable speed generator 1 is a current supplied from the current command generator 9. command value I _a ^*, I _b ^*, are controlled to be those following the I _c ^*.

The cycloconverter 7 constitutes an AC excitation means, and therefore, if power of a certain frequency from the power system can be converted into power of an arbitrary frequency, for example, an inverter device or the like can be used. Alternating current excitation means may be used.

By using the cycloconverter, it is possible to further improve the cost and control stability.

FIG. 3 shows the details of the cycloconverter 7 for one phase thereof. In FIG. 3, 26 is the secondary current detector of the variable speed generator 1, 27 is the command value I _a ^* Value I
A current controller for instructing the transfer device 28 to generate a thyristor firing pulse at the required phase of three-phase _splitting by comparing _Ma , 29 and
Reference numeral 32 is a gate for passing a gate pulse for energizing the thyristor gates of the positive connection side thyristor converter 30 and the reverse connection side thyristor converter 31, respectively, and 33 is a secondary current polarity switching command generator, which is a current command value. A polarity switching command signal PN (the signal level is 1 when the power supply command is supplied to the positive connection side and 0 when the power supply is negative connection side) is generated in accordance with the positive or negative of.

Reference numeral 35 is a zero current detector. The output level when the detected current is regarded as zero is "0", and the output level when it is considered that current is flowing is "1". Generate ZD.

Therefore, the current command value is
I _a ^*, I _b ^*, so that the AC excitation current corresponding to I _c ^* is supplied to the variable-speed generator 1.

On the other hand, the electric motor side including the water turbine 3 will be described. 20 is a switching device, 21 is a speed control based on the deviation between the electric power P supplied to the AC system 23 and the electric power command P _o given from the outside. hydraulic turbine output adjustment signal generator for generating a signal to be provided to vessel 19, 22 and the actual rotation speed N of the water wheel 3, the rotational speed command N _o on the basis of the deviation between the governor which is supplied externally 19
It is a water turbine speed adjustment signal generator for generating a signal to be given to.

Therefore, the turbine 3 is guided by the guide vane 17 via the servo system 18 by the signal from either the turbine output adjustment signal generator 21 or the turbine speed adjustment signal generator 22 depending on the state of the switch 20.
The operation is controlled by operating the opening degree of.

Next, the operation of the entire embodiment will be described.

The present invention is characterized in that the switches 12, 14, 20 in this embodiment are switched according to the state of the load.

That is, in the embodiment of FIG. 1, these switching devices 1
Although the specific configuration of the switching operation between 2, 14 and 20 is omitted, it is possible to automatically switch according to the load including a control device as shown in the figure. First, the switching timing of these switching devices will be described below.

Generally, when the water level H and the turbine output P are determined, the efficiency η of the turbine is most efficient with respect to the rotation speed N as shown in FIG. For example, in the FIG. 5, the water level H _1, the rotational speed N ₁ for water turbine output P _1, the water level H _2, so that the rotational speed N ₂ for water turbine output P _2. In addition, one of the advantages of the variable speed power generation system is that it can be operated by selecting the highest efficiency point.

By the way, in this case, the output P and the maximum efficiency rotation speed N
Is shown in FIG. However, in such a system, the slip frequency is limited due to the capacity of the cycloconverter, while the rotation speed has the maximum rotation speed N _x and the minimum rotation speed N _m , so that as shown in FIG. In addition, at the time of partial load operation, constant speed operation at the minimum rotation speed N _m is desirable.

Therefore, in the embodiment shown in FIG. 1, in the vicinity of the rated load at the operating point A shown in FIG. 6, the respective switching devices 12, 14, 20 are kept in the illustrated state so that the original variable speed operation is performed. ing. That is, at this time, as in the conventional example of FIG. 4, the operation is performed by the detection signal of the phase detector 2.

When a partial load command is sent in this state, B
After confirming that the point has reached the minimum speed, the switching devices 12, 14, 20 are switched. The operation at the time of this switching will be described below. In addition,
Here, only the cos θ component will be described as an example.

First, the signal of the phase detector 2 has a waveform shown as [cos θ] in FIG. 11, and the frequency generator 11 restarts in synchronization with the signal of the phase detector 2 at time t _1. And [Cos (ω _o t)] in FIG. 11 shows the signal. Note that [sin ω _o t] also restarts with a phase difference of 90 ° in time t ₁ .

Therefore, the switches 12, 14, 20 are simultaneously switched in synchronization with this time t ₁ .

At this time, the current command generator 9 and the signal I
d ^* , Iq ^* , cos θ, sin θ do not change at time t ₁ , and therefore,
The output of the variable speed generator 1 does not change and does not disturb the AC system.

This state will be further described with reference to FIG. 9. At this time, the magnetic pole arrangement of the variable speed generator 1 has not changed. Therefore,
The current on the system side (stator side) causes a virtual magnetic pole 93 by the stator side coil 90, and the virtual magnetic pole 93 rotates at a rotation speed that matches the system frequency. Further, on the rotor side, a virtual magnetic pole 94 is generated by the current flowing through the rotor coil 91, and the virtual magnetic pole 94 rotates at a rotation speed corresponding to the excitation frequency (ω _o ) as viewed from the rotor. Seen from the stopped state, it means that it is rotating at a rotation speed that matches the system frequency, which causes the magnetic field lines 92 to always rotate in a fixed arrangement and to send energy from the rotor to the stator. There is.

At this time, in the case of the conventional variable speed power generation system, since the phase of the phase detector 2 automatically follows when the disturbance of the rotational speed occurs, the virtual magnetic pole 94 is automatically adjusted according to the system. Therefore, it is difficult to suppress the fluctuation of the rotation speed.

However, in this embodiment, at this time, the frequency generator
Since the frequency of 11 is constant, the virtual magnetic pole 94 behaves as if it were fixed to the rotor, suppressing the disturbance of the rotation speed.

Explaining this in more detail, since the virtual magnetic pole 94 may be considered to be equivalent to a normal synchronous machine, the electric output P, that is, the torque of the generator is as shown in FIG. 10 with respect to the internal phase difference angle θ _p . Become. Therefore, if the vehicle that was being driven at point C now moves to point D, the force to return it will automatically work and the vehicle will be driven at a constant speed. The return force in this case is very large.

Therefore, according to this embodiment, as shown in FIG. 8, the fluctuation of the rotation speed N is eliminated under the partial load, and the vibration due to the central whirl can be suppressed to a negligible level.

In addition, in this embodiment, at the time of partial load, since the characteristics are exactly the same as those of the synchronous machine, at this time, the speed governor 19 is the turbine output adjustment signal generator 2 like the conventional turbine generator.
Controlled by signal.

Further, the command value Iq ^* is up to this time, since it becomes disturbing high too is set at a level high-voltage control, as shown in FIG. 12, the switching time of the value I _ql ^*, palliative time value It is designed to be lowered to I _qo ^* . Then, this lowering speed is set to be sufficiently slower than the response speed of the d-axis component current command generator 13, and finally, As a Trip command value Id ^* is varied from Id ₁ ^* to Id ^*.

Next, in FIG. 6, when a command corresponding to the load at the point A comes from the operating point at the point C, switching is performed at the point where the point B is passed. When switching is performed, as shown in FIG. 13, the command value Iq ^* is gradually increased from Iqo ^* , and at time t ₂ when the signal of the phase detector 2 matches the signal of the frequency generator 11, Switch the switches 12, 14, 20 again. Even at this time, the excitation state is exactly the same as before, and the system is not disturbed.

As described above, according to the present embodiment, in a partial load region such as a central whirl where unstable excitation is likely to occur, it is possible to provide a braking effect similar to that of a synchronous machine, so that the unstable vibration phenomenon is reduced to a level at which there is no problem. Can be suppressed.

〔The invention's effect〕

According to the present invention, in the motion of the prime mover in the unstable vibration region, a braking force as strong as a synchronous torque can be exerted, so that the unstable vibration can be suppressed to a small level, and the drivability of the variable speed power generation system can be improved. Thus, the scope of application can be expanded.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a variable speed power generation system according to the present invention, FIG. 2 is a block diagram showing details of a current command generator in the above embodiment, and FIG. 3 is a cycloconverter in the same embodiment. Block diagram showing details of one phase, FIG. 4 is a block diagram showing a conventional example of a variable speed power generation system, FIG. 5 is an explanatory diagram of turbine efficiency, and FIG. 6 is an explanatory diagram showing operating points of the system. FIG. 7 is an explanatory view of vibration of a conventional system, FIG. 8 is an explanatory view of vibration of an embodiment of the present invention, FIG. 9 is an explanatory view of magnetic poles of a variable speed generator, and FIG. Explanatory drawing, FIG. 11 is explanatory drawing at the time of switching, 12th
FIG. 13 is an explanatory diagram of the command value after switching, and FIG. 13 is an explanatory diagram at the time of switching again. 1 ... Variable speed generator, 2 ... Phase detector, 3 ... Water turbine,
7: Cycloconverter, 9: Current command generator, 11
…… Frequency generator, 12,14,20 …… Switcher, 13 …… D axis component current command generator, 15 …… Q axis component current command generator, 16
...... Constant q-axis component generator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Nagura 3-1-1 Sachimachi, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Factory (72) Inventor Shinsaku Shirata 3-chome, Saiwaicho, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd. Hitachi factory (72) Inventor Eizo Kita 3-3-22 Nakanoshima, Kita-ku, Osaka-shi, Osaka Prefecture Kansai Electric Power Co., Inc. (72) Inventor Hiroto Nakagawa Kita, Osaka-shi, Osaka 3-3-22 Nakanoshima-ku, Kansai Electric Power Co., Inc. (72) Inventor Taisho Ohno 3-3-22 Nakanoshima, Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Kansai Electric Power Co., Inc.

Claims (2)

[Claims] 1. An AC excitation type variable speed generator connected to an AC power system, and a phase detector for detecting a phase difference between a rotor rotation position of the variable speed generator and a voltage of the AC power system. In the variable speed power generation system of the method of performing AC excitation for the AC excitation type variable speed generator by the output signal of the phase difference detector, frequency command signal generating means for generating a signal of a predetermined constant frequency, and the frequency Switching means for arbitrarily selecting and outputting one of the output of the command signal generating means and the output signal of the phase detector, and AC exciting means for generating AC exciting power for the variable speed generator by the output of the switching means. The variable speed power generation system is characterized in that the variable speed power generation system is configured to switch and control the switching means according to a load region of the variable speed generator. 2. The variable speed generator according to claim 1, wherein the alternating current excitation means includes a cycloconverter fed from the alternating current power system, and the variable speed generator is determined by an upper limit value of the converted power capacity of the cycloconverter. A variable speed power generation system, characterized in that the switching control of the switching means is performed in accordance with the operable rotation speed.