JPS5944646B2 - Reactive power regulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage-controlled reactive power adjusting device that connects a self-excited inverter device to a power source and adjusts generated reactive power by adjusting the output voltage of the inverter device. .

FIG. 1 shows a configuration diagram and a vector diagram for explaining the operation of this type of device.

FIG. 2 shows a configuration diagram of a conventional device. 15, a power source 1 is connected to a self-excited inverter 3 (hereinafter simply referred to as an inverter device) via an AC reactor 2.

When the power supply voltage is Vs and the inverter voltage is VINV, the voltage VL applied to the AC reactor 2 is VS-VINV, and when the current flowing through the AC 20 reactor 2 is IL, the operation vector diagrams b and c are obtained. Figure b is a vector diagram in which the inverter 3 consumes leading reactive power.
The system voltage Vs and the inverter output voltage VINV are in phase, and when VINV is made 25 times larger than Vs, a voltage of VL is applied to the AC reactor 2, and the current flowing through the AC reactor 2 is delayed by 900 phases with respect to VL. IL
Therefore, it is as if the inverter 3 has the same function as a capacitor. In figure c, the inverter output voltage 30
This is a case where VINV is in the same phase but smaller than the power supply voltage Vs. Voltage VL is applied to AC reactor 2, and current IL with a 900 phase delay flows, as if inverter 3 had the same function as the reactor. I know what you're doing. The self-excited inverter device 3 that realizes such a zero-effect power adjustment device uses an inverter that converts DC input into three-phase AC output, and can be applied to uninterruptible power supplies that are widely used in the world. Needless to say. These inverter devices have a configuration as shown in FIG. An inverter device 3 is connected to a power source 1 via an AC reactor 2. The inverter device 3 is connected to a transformer 36 for applying DC input, a rectifier 32, a DC reactor 33, and a capacitor 34, and is composed of an inverter main body 31 and a control device 35. The inverter body is a self-excited inverter that employs various commutation methods and is constructed using thyristors.

Since the reactive power adjustment device generates reactive power and does not generate active power, the DC input only supplies the loss within the inverter device. It can be seen that in the conventional reactive power adjusting device of this type, due to the presence of such a DC input circuit, the device is not only large in size but also expensive. The present invention provides a reactive power device that can eliminate the conventionally necessary DC input circuit by obtaining power for losses in an inverter device directly from a power source via an AC reactor.

The principle is as shown in Figure 3, by delaying the phase of the inverter output voltage VIN with respect to the power supply voltage s, the active power corresponding to the phase difference between the power supply voltage and the inverter output voltage is transferred from the power supply via the AC reactor. Supplied to the inverter device.

In Figure 3a, by making the inverter voltage higher than the power supply voltage, the inverter device can act as a capacitor, and in Figure 3b, by making the inverter voltage lower than the power supply voltage, the inverter device can work as a reactor. , reactive power regulator b without DC input circuit
≦Becomes realizable. FIG. 4 shows an embodiment of the present invention.
An inverter device 4 is connected to a power source 1 via an AC reactor 2.
is connected. The inverter device 4 includes an inverter main body 41 and a gate circuit 42. The input signal to the gate circuit 42 is the output signal of the phase adjustment circuit 40 with reference to the power supply voltage. The phase adjustment circuit 40 uses a comparator 44 to compare the sine wave voltage of the power supply 1 and the control voltage Ec, and when the sine wave voltage t) becomes larger than the control voltage, an output is generated, and the differential circuit 43 It is differentiated and its output is applied to the gate circuit 42. The sinusoidal voltage of the power supply is obtained by a transformer 11 which produces 3 to 6 phases. When controlling the leading reactive power, the changeover switches 25 and 26 are connected as shown, and the positive reactive power reference signal Qr(1) enters the polarity converter 24 and becomes a negative signal. The reactive power is output from the reactive power detector 23 by signal calculation of the voltage transformer 21 and the current transformer 22, as a positive signal Qf.
(g) is detected. This detection signal is
7, and the added output is added to the control amplifier 2 whose polarity is inverted.
8 and the output of 28 forms a control voltage Ec which is one of the inputs of the phase adjustment circuit 40. In order to simplify the explanation of the operation of the present invention, the inverter main body 41 of the inverter device 4 shown in FIG. 5 is used.

This inverter body is conventionally known as an AC side commutation inverter, and includes a plurality of main thyristor elements 416, an auxiliary thyristor 420, a diode 417, a commutation reactor 4
18, commutation capacitor 419, filter capacitor 4
11. It consists of an auxiliary power supply 412, and the 3-phase output is connected to terminal 4.
It can be extracted from 13,414,415. The inverter output phase voltage waveform in FIG. 5 has a waveform as shown in FIG. 6e, which is closer to a rectangular wave than a sine wave. It goes without saying that the self-excited inverter used in the actual reactive power adjustment device is manufactured by multiplexing the inverter used in conventional uninterruptible power supply equipment so that the output voltage waveform approaches a sine waveform. Here, an output voltage waveform as shown in FIG. 6e is used to explain the operation. The operation of the present invention will be explained using the operation waveforms shown in FIG. Only a capacitor 411 is connected as a DC circuit to the inverter main body in FIG. This inverter body. Since commutation is performed six times in one cycle, the gate circuit 42 outputs a firing pulse to each of the six main thyristors 416 in one cycle. In order to extinguish the conducting main thyristor 416, it is necessary to fire the auxiliary thyristor 420 connected to the main thyristor. For example, when the auxiliary thyristor is turned on to extinguish the main thyristor connected to one AC output terminal, and the main thyristor connected to the same AC output terminal is turned on next, the commutation time is The ignition will take place at the same time. Now, considering the state in which the leading reactive power is being adjusted, the reactive power reference signal is slightly larger than the reactive power detection signal, so the adder 27
The output signal of is a negative value, and the output Ec of the polarity inversion control amplifier 28 is a positive value. The control voltage Ec is compared with the U phase and phase voltage Vu of the three-phase power supply as shown in Fig. 6b, and Vu is
At the time T, when the value becomes larger than c, the comparator 44b≦operates, and the result becomes as shown in C in the figure. Furthermore, the differentiating circuit 43f)≦operates, and an output as shown in d in the same figure is applied to the gate circuit 42, and from the gate circuit it is connected to the upper side of the U-phase terminal 413 of the inverter main body in FIG. Main thyristor 4
16 is ignited, and the U-phase inverter output phase voltage rises from negative to positive as shown in FIG. 6e. The main thyristors t) are sequentially fired during one cycle, and a waveform as shown in FIG. 6e is output.

Considering the fundamental component of the waveform of e, θ with respect to the power supply voltage u. It has a phase delay of θ. This means that the active power corresponding to the phase difference is supplied from the power source 1 to the inverter device 4, and this active power is equal to the loss within the inverter device. At this time, the DC voltage of the capacitor 411 in the inverter device has a value that generates the regulated reactive power. When the reactive power reference signal Qr is increased in order to increase the leading reactive power, the difference l) from the reactive power detection signal becomes larger, and the output f) of the addition calculator 27 becomes larger with a negative value, and the polarity is reversed. The output Ec of the control amplifier 28 increases, the delay phase difference of the output voltage of the inverter device with respect to the power supply voltage phase increases, and the active power that enters the inverter device from the power source increases, and this power is caused by losses within the inverter device. It becomes equal to the sum of the charging power of the capacitor 411, and increases the voltage of the capacitor 411. Due to the increase in DC voltage, the inverter output voltage, which is close to a square wave, increases, the voltage applied to AC reactor 2 increases, the current flowing through reactor 2 increases, and the reactive power increases as a result, matching the reactive power reference signal. Reactive power will be generated by the inverter device t)s. When the reactive power reference signal is lowered, the control system works in the same way,
The control voltage Ec decreases, the active power b that enters the inverter device from the power supply becomes smaller, the DC voltage decreases, the inverter output voltage decreases, and the generated reactive power decreases b
≦I understand. If the control voltage Ec increases for any reason, the phase difference θ with the power supply voltage will increase. increases, the active power b≦ applied to the inverter device from the power supply increases, the DC voltage within the inverter device increases, the inverter voltage increases, and a large advance of reactive power is detected,
It can be seen that the reactive power reference signal is exceeded, the output of the adder 27 becomes a positive value, the output of the polarity inversion control amplifier 28, that is, the control voltage Ec is lowered, and the control system operates so as to return to the original state. .

Furthermore, even if the control voltage Ec decreases, the control system works to increase the control system f)≦control voltage Ec. When adjusting the delayed reactive power, the changeover switches 25 and 26 in FIG. 4 are connected in the opposite direction as shown, so that the reactive power reference signal becomes a positive value signal and the reactive power detection signal becomes a negative value signal. The signal is input to the addition calculator 27, and the polarity inversion control amplifier 28 is operated. The reactive power adjustment operation has been explained in terms of progressive reactive power adjustment, so it will be omitted here. If the control voltage Ec decreases from the steady state, the phase difference θ between the power supply voltage and the inverter output voltage. becomes smaller, the active power entering the inverter device from the power supply becomes less, the DC voltage inside the inverter device decreases, and the detected delayed reactive power increases,
The reactive power reference signal will be exceeded, the output of the adder 27 will become a negative value, the output of the polarity inversion control amplifier 28 will increase, the control voltage Ec will increase, and the control system will return to the original state. It turns out that it works. Further, even when the control voltage Ec increases, the control system operates to decrease Ec. Although the inverter device of the present invention includes many harmonic components in the output voltage, the output waveform is improved by multiplexing the inverter devices.

In this case, the phase adjustment circuit based on the power supply voltage can be constructed using a polyphase winding transformer. In the present invention, the sine wave voltage of the power supply is used as one of the inputs of the phase adjustment circuit, but an oscillator is used to operate a multiple inverter device at the oscillator output frequency, and the phase adjustment is performed by controlling the frequency of the oscillator. Needless to say, an Azelock loop control system can also be adopted. As explained above, the reactive power adjustment device of the present invention eliminates the need for a DC input circuit.
The device can be made compact and inexpensive by simply adding a control circuit.

[Brief explanation of the drawing]

Figure 1 is a block diagram and vector diagram for explaining the principle of a reactive power adjustment device that adjusts the output of an inverter, and Figure 2
The figure is a block diagram of a conventional device, Figure 3 is a vector diagram for explaining the principle of the present invention, Figure 4 is a block diagram showing an embodiment of the present invention, and Figure 5 is a diagram showing an embodiment of the present invention. FIG. 6, which is a diagram showing an example of the inverter device used, is an operation explanatory diagram for explaining the operation of an embodiment of the present invention. In the figure, 1 is a power supply, 2 is an AC reactor, 4 is an inverter device, 40 is a phase adjustment circuit, 23 is a reactive power detector, Qr
is a reference reactive energy signal, 24 is a polarity converter, 25, 26
27 is a changeover switch, 27 is an addition calculator, and 28 is a polarity inversion control amplifier.

Claims (1)

[Claims] 1. A self-excited inverter device is connected to the grid power supply via an AC reactor, and the inverter output voltage is controlled to be higher than the power supply voltage to operate the self-excited inverter device as a capacitor, and conversely, the inverter output voltage is controlled. In a device that adjusts reactive power by operating the self-excited inverter device as a reactor with the power supply voltage being lower than the power supply voltage, a differential calculation is performed between a signal that detects the reactive power of the grid and a reference signal of the reactive power to be adjusted. means for deriving a control voltage using the power supply voltage, and generating an ignition pulse for the self-excited inverter device by comparing the power supply voltage and the control voltage;
A phase adjustment circuit is provided to delay the phase of the inverter output voltage with respect to the power supply voltage, and active power corresponding to the phase difference between the power supply voltage and the inverter output voltage is supplied from the power supply through the AC reactor to the self-excited type. A reactive power adjustment device characterized by supplying power to an inverter device.