JPH0258879B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an excitation adjustment device for an alternator.

The output voltage of a generator fluctuates due to load changes such as load on/off. In particular, generators with high impedance, such as emergency generators, have large output voltage fluctuations due to load fluctuations, which adversely affects other loads supplied by the generator. Therefore, it is desired that a control device that controls the output voltage of the generator be able to control the generator output with good responsiveness even to rapid load changes. Furthermore, in a generator having a load such as a rectifier, the output voltage waveform is often distorted, and even in this case, it is desired that the control device be able to stably control the generator output voltage.
Furthermore, in the case of a marine generator, the generator is required to have the ability to continue flowing a specified current for a specified period of time even if the generator output is short-circuited, that is, to have compound winding characteristics.

FIG. 1 shows a conventional excitation adjustment device having the above-mentioned compound winding characteristic function. According to this, a winding transformer 3 having a current winding 31 , a voltage winding 32 and an output winding 33 is provided to supply power to the field winding 2 of the alternating current generator 1 . current winding 3
1 is inserted in series with the generator output line, and the voltage winding 3
2 is connected to a generator terminal via an AC reactor 4. A capacitor 5 is connected to a connection point between the voltage winding 32 and the AC reactor 4. A rectifier 6 is connected to the output winding 33, and the field winding 2 is connected between the DC output terminals of the rectifier 6. Furthermore, a thyristor 7 and a resistor 8 are connected between one phase terminal on the AC side and one terminal on the DC side of the rectifier 6.
A series circuit is connected to the overvoltage suppressing circuit 9, and an overvoltage suppression circuit 9 is connected in parallel to this series circuit. The ignition phase of the thyristor 7 is controlled by the control device 10 so that the generator terminal voltage matches the voltage setting value set by the voltage setting device 11.

The winding 32 of the voltage component circuit that provides the excitation necessary to generate the rated voltage at no-load and the winding 31 of the current component circuit that supplies the excitation that compensates for the voltage drop due to the load current during the load are magnetically coupled. I'm doing it,
A combined output of both appears at the output winding 33. A generator current or a current proportional to it flows through the winding 31 . The output voltage of the generator 1 is applied to the winding 32 via the reactor 4. The output of the winding 33 is rectified by the diode rectifier 6 and applied to the field winding 2 to cause a field current to flow. Voltage component is 4→3 from generator output
2 → 33 → 6 → 2, and the current component is 31 → 3
3 → 6 → 2 are added.

The voltage regulating shunt thyristor 7 is connected between one phase of the input circuit of the rectifier 6 and the negative electrode of the output of the rectifier 6 via a resistor 8. The excess current of the three-winding transformer required to obtain the desired output voltage of the generator is diverted to the alternating current side by firing this thyristor, so that it does not flow to the field circuit. Generally, the output current of a three-winding transformer is designed to be slightly larger than the required field current, so it is necessary to fire the thyristor every cycle to shunt the current. The divided flow to the thyristor, that is, the firing phase of the thyristor is determined by the generator voltage control device 10 and the generator voltage setting circuit 11.
The generator voltage is controlled to be at the set value.
The capacitor 5 is connected to resonate with the reactor 4 to reduce the influence of the generator field resistance and to easily establish the voltage at the time of starting.

As mentioned above, the basics of the conventional method are three
Since the method uses a wire-wound transformer to magnetically couple the voltage element and the current element, it has the following drawbacks.

(1) A three-winding transformer is larger than a transformer of the same capacity.

(2) Output changes depending on the degree of coupling, so adjust the output (for example, adjust the gap of the AC reactor, the size of the thyristor series resistance, or the size of the capacitor)
It is necessary to do this.

Furthermore, since the conventional method uses a thyristor to shunt the current every cycle, when the thyristor is turned off, all the output current of the three-winding transformer must flow to the field circuit. The output of the three-winding transformer can be regarded as a constant current source, and the inductance of the field circuit is much larger than that of the generator circuit, so when the thyristor is turned off, a high voltage is generated in the field circuit. For this reason, an overvoltage suppression circuit 9 is connected, but since the loss generated by this circuit is large (9 absorbs the current until the field circuit absorbs the current), the efficiency of the device decreases and the size and weight increase. There is also the drawback of being mellow.

Furthermore, the shunt thyristor 7 must be fired in synchronization with the generator voltage. However, when a load such as a rectifier is connected to a generator, the output voltage of the generator becomes a distorted waveform due to the commutation of the rectifier. Since the synchronization signal for firing the thyristor 7 is derived from the generator output voltage, the synchronization signal fluctuates due to this distortion. For this reason, there is a drawback that control becomes unstable depending on the state of the load, or in some cases, control becomes impossible.

The present invention provides a generator excitation adjustment device that has a simple circuit configuration, can obtain compound winding characteristics, does not require complicated adjustment, and can stably control the generator voltage even if the voltage waveform of the generator is distorted. The purpose is to provide

The present invention will be described below with reference to the drawings.

FIG. 1 shows one embodiment of the present invention. According to this, the AC side terminal of the rectifier 101 for feeding power to the field winding 2 of the AC generator 1 is connected on the one hand to the secondary side of the power transformer 102 inserted into the output bus of the generator. , on the other hand, is connected to a generator terminal via an AC reactor 103. AC reactor 1
03 serves as a voltage component circuit for extracting a component dependent on the generator voltage, and a power current transformer 10
2 serves as a current component circuit for extracting components dependent on the generator current. Both components are rectified by 10
Vector synthesis is performed on the AC input side of 1. The DC output current of the rectifier corresponds to the rectified composite current of both components. A controllable semiconductor switch 100 is connected between the DC output terminals of the rectifier 101, which makes it possible to shunt a portion of the DC output current of the rectifier. Rectifier 10
1 can be configured as a three-phase diode bridge, and the semiconductor switch 100 can be a transistor, a gate turn-off thyristor, or a thyristor chopper. A current absorption circuit 104 is connected in reverse series to the field winding 2 to which current is supplied from the rectifier 1 . As the current absorption circuit 104, a capacitor, a resistor, or a voltage limiting element such as a constant voltage diode, a varistor, etc. can be used. This current absorption circuit 104 serves to absorb the difference current between the DC output current of the rectifier 101 and the field current when the semiconductor switch 100 is off. The conduction rate of the semiconductor switch is controlled by a control device (not shown), thereby adjusting the field current. In this case, conductivity control is preferably performed by closed-loop control using a voltage regulator that derives the deviation between the detected value of the generator terminal voltage and its target value. Due to the voltage-dependent component and current-dependent component included in the DC output current of the rectifier 101, when the load fluctuates, it is possible to compensate for the load fluctuation with good responsiveness by changing the DC output current.

An embodiment in which a capacitor is used as the current absorption circuit 104 is shown in FIG. According to FIG. 3, a capacitor 105 as a current absorption circuit
In addition, a backflow prevention diode 106 is inserted between this capacitor and the semiconductor switch 100. The other configurations are the same as in FIG. 2. Diode 106 prevents discharge current from capacitor 105 from flowing through semiconductor switch 100 when semiconductor switch 100 is on. This eliminates the risk of destruction of elements such as transistors used as the semiconductor switch 100.

Additionally, as shown in FIG. 4, a transformer 107 may be installed between the AC reactor 103 and the generator, if necessary.
It is also possible to change the voltage applied to the AC reactor 103 by inserting the AC reactor 103.

FIG. 5 shows operating waveforms of each part in the embodiment of FIG. 3. The DC output current of the rectifier 101 is i ₁₀₁
actually includes a ripple component, but for the sake of clarity, it is shown as a direct current Io without ripple component. The voltage of the semiconductor switch 100 is V ₁₀₀
is shown. According to this figure, the semiconductor switch is turned on for a time Ton out of a period T. Therefore, the conduction rate α of the semiconductor switch 100 is α=Ton/T (1). i ₁₀₀ indicates the current of the semiconductor switch 100. i ₁₀₅ is capacitor 10 as a current absorption circuit
5 and i ₂ is the current flowing in the field winding. The field current i ₂ is also the magnitude I _F , ignoring the ripple component.
is shown as a current with . Rectifier 101
The magnitude of the DC output current i ₁₀₁ takes a value I ₀ determined by the voltage and current of the generator in a steady state, and the magnitude of the field current I _F is equal to this value I as is clear from FIG. Less than ₀ . When the semiconductor switch 100 is in the OFF state, the DC current I ₀ flowing from the rectifier 101 through the diode 106 is divided into the field winding 2 and the capacitor 105 . That is, the field current I _F flows through the field winding 2, and the difference current _I0 - _IF flows through the capacitor 105. At this time, the voltage across the capacitor 105 appears as the voltage across the field winding 2 and the voltage V ₁₀₀ across the semiconductor switch 100 . This voltage increases due to charging by the difference current, and at the same time, the field current I _F also increases.

When the semiconductor switch 100 is turned on from this state, the direct current I ₀ that has been divided into the field winding 2 and the capacitor 105 is bypassed to the semiconductor switch 100. On the other hand, the field current I _F tends to continue flowing due to the large inductance of the field winding. Therefore, field current I _F continues to flow through capacitor 105. At this time, the capacitor 105 is discharged by the current I _F in the opposite direction, its voltage value decreases, and the field current I _F also decreases. In this case, diode 106 prevents capacitor 105 from discharging through semiconductor switch 100. This reduces the load on the semiconductor switch 100, prevents a sudden voltage drop across the capacitor 105, and prevents ripples in the field voltage and field current from increasing.

Furthermore, since the on/off operation is performed at a high frequency and the inductance of the field winding circuit is large, the above-mentioned increase/decrease in current and voltage per cycle (ripple component) due to the on/off operation is Since it is so small, it is ignored in FIG.

In a steady state, if α is the conductivity that provides the desired field current I _F , then I _F = (1-α) I ₀ ... (2), so from equations (1) and (2), the semiconductor The conduction rate of the switch is determined. As can be seen from equation (2), the field current I _F includes the conduction rate α of the semiconductor switch 100 and the rectifier 10
The DC output current of 1 is affected. Since the influence of the conduction rate α is an average value effect, it is not sufficient to compensate for rapid fluctuations in load. On the other hand, since the DC output current Io is almost directly affected by load fluctuations, it compensates for rapid load fluctuations with good responsiveness.

As described above, according to the present invention, compound winding characteristics can be obtained by vector-synthesizing the voltage-dependent component and the current-dependent component on the AC side of the rectifier without using a three-winding transformer. On the DC side of the rectifier, a semiconductor switch performs shunt control to adjust the excitation, and a current absorption circuit is installed in parallel to the field winding to absorb the difference current between the rectifier's DC output current and the field current. As a result, the configuration is very simple, and not only can it be made smaller, lighter, and less expensive than conventional devices, but it also has the effect that it does not require adjustment of the main circuit configuration. Moreover, since the excitation adjustment is performed through shunt control using a semiconductor switch particularly on the DC side, there is no fear of malfunction due to waveform distortion of the generator voltage, and stable and highly accurate voltage control performance can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of a conventional device, and FIGS. 2 to 4 show mutually different embodiments of the present invention,
FIG. 5 shows operating waveforms of various parts in the embodiment shown in FIG. 1...AC generator, 2...Field winding, 100...
...Semiconductor switch, 101... Rectifier, 102...
...Power current transformer, 103...AC reactor, 1
04... Current absorption circuit, 105... Current absorption circuit capacitor, 106... Backflow prevention diode.

Claims (1)

[Claims] 1. An AC reactor 103 for extracting a component dependent on the terminal voltage of the alternator 1, a power current transformer 102 for extracting a component dependent on the output current of the alternator 1, and both components. and a rectifier 101 that rectifies a vector-combined current and supplies the rectifier to the field winding 2. a semiconductor switch 100 that is capable of switching, a current absorption capacitor 105 connected in parallel to the field winding 2, and a reverse current prevention diode 106 inserted between the current absorption capacitor 105 and the semiconductor switch 100. 1. An excitation adjustment device for an alternator, characterized in that the excitation adjustment is performed by controlling the conduction rate of the semiconductor switch 100.