JPS6035890B2 - circuit constant generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power compensation device, and more particularly to a circuit constant generating device that generates arbitrary circuit constants through switching operations.

Conventionally, the circuits illustrated in Figures 1, 2, and 3 have been used to improve the quality of power in power systems (suppressing voltage fluctuations, improving power factor, and improving voltage and current waveforms). ing.

Fig. 1 shows a power conversion switching circuit, in which a circuit in which thyristors 1 to 4 are assembled in a bridge is connected to the receiving end of the system, a reactor 5 is connected to the DC output side, and a DC current ld , is flowing.

Note that Vo is a voltage source, the voltage source impedance is next, the receiving end voltage is Va, and an alternating current ia flows into this circuit. The thyristor shown in FIG. 1 is switched at the timing shown in FIG. 2.

However, in FIG. 2A, the axis represents time t, and the vertical axis represents AC voltage.
It is a characteristic diagram of t of n, and a sine curve is drawn as shown. This is the angular frequency of the power source. In FIG. 2B, the axis represents time t, and the vertical axis represents alternating current la, indicating the direction in which the direct current ld flows toward the alternating current side. After all, from FIG. 2A and FIG. 2B, the sirens are commutated once every half cycle in synchronization with the power supply voltage. Note that Δt is the ignition time. The active power P and reactive power Q, which flow into this circuit from the AC side, are given by the firing phase angle Q (positive and negative), P, = palm va, ld, COSQ
...mQ,=2Hayabusa va,,d,sinQ
...(It will be 21.

Note that Va is the effective value of the AC side voltage. Therefore, P.
When setting Q to a predetermined value and attempting to compensate for the power described above, two adjustment factors are the DC current ld and the ignition phase angle Q (Δt of Q=).

Here, the ignition phase angle Q is changed with a delay of less than half a cycle, but since ld, is determined by the integral of the active power flowing into this circuit, the change in ld is slow. In particular, when there is only one circuit as shown in the figure, P, must be 0 according to the law of conservation of energy, so according to the {1} formula, = ±T/2, and by substituting it into the formula ■, we get Q, = ± quasi-va
．． ld, so the adjustment element is only ld.

In the end, this circuit converts the reactive power Q, ld. This is a circuit that performs invalidity adjustment by controlling.

The third circuit is a circuit in which the DC side of the circuit in Figure 1 is connected twice in series.
It is a diagram. On the A side, an alternating current of voltage Va and current ja is input to a bridge circuit composed of four thyristors, and an alternating current of voltage vb and current ib is similarly input to a bridge circuit composed of four thyristors. B side pointed actor 6
The DC output sides of the respective thyristor circuits are connected in series through a common connection. In this circuit, since the DC current ld3 is common, they must be equal, and the A side,
The active power and reactive power on the B side are P^3 and QA3, respectively.
, PB3・QB3 then PA32 + Q^32=PB3
There are 20 QBs and 32 relationships.

Therefore, PA3/QA3 and PB3/QB3 interfere with each other through ld3. The harmonic components of the current flowing into this circuit are determined by the firing phase angle and must be selected based on the fundamental wave of the AC input voltage. Depending on the value, a large harmonic current will flow.

Since the conventional power conversion switching circuit operates as described above, it has the following drawbacks.

Because harmonic current flows, voltage and current waveforms deteriorate.

DC current is the control element, and the DC power source is determined by the integral of active power flowing into this circuit, resulting in a time delay and poor control responsiveness.

When two or more circuits are connected, the sum of the squares of the active power and reactive power of each circuit must be equal, so the active power and reactive power cannot be changed independently in each circuit.

From the above formula {1}, '21, P.・Since Q is determined by the ignition phase angle Q with the power supply voltage as a reference, it cannot be applied in places where the power supply voltage is unstable or where the voltage waveform is distorted.

Furthermore, it has the disadvantage that this compensation circuit cannot be inserted in series with an AC circuit.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a circuit constant generator that does not disturb the voltage waveform, has good responsiveness, and can be used in combination with a plurality of circuit constant generators.

According to the present invention, the purpose of the upper cover is achieved by switching the thyristor at a high frequency in a circuit in which the input side of a bridge circuit consisting of a thyristor is connected to an AC power supply and the output side is connected to a reactor.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram of a circuit constant generator according to an embodiment of the present invention.

It is comprised of a power conversion switching block 11 to which alternating current is input, and an ignition control block 12 that controls the switching timing of this power conversion switching block 11. In addition, power conversion switching block 1
1 is shown in detail in FIG. 5, and the ignition control block 12 is shown in detail in FIG.

Fig. 5 shows a power conversion switching circuit, but the difference from the conventional example shown in Fig. 1 is that an L/C circuit is inserted between the AC power supply and the thyristor bridge circuit, and high frequency ripples due to switching operation are generated. The point is that the amount is removed.

The other configurations are the same as the conventional example shown in FIG. Therefore, the difference between this embodiment and the conventional example is that the ignition control block 12 is
By switching the thyristors 13 to 16 in FIG. 5 at a high frequency, the power switching block circuit in FIG. 5 is equivalently made into the circuit in FIG. 6. FIG. 6 shows a circuit in which a voltage source Vg is connected in series with Yg, and a current source ig is connected in parallel with it, to which AC power is input.

In other words, the circuit of FIG. 5 is switched at high frequency by the ignition control circuit of FIG. 8 to create an equivalent circuit of FIG. 6 having arbitrary circuit constants.

FIG. 7 shows the time relationship of high frequency switching in this embodiment, where the vertical axis represents the current flowing to the alternating current side, and the horizontal axis represents the time t. The values of the elements of each equivalent circuit shown in FIG. 6 are determined by the switching interval t shown in FIG.

The basic principle of this embodiment will be explained in detail below.

Now, let the AC current input to the power conversion switching block 11 in FIG. 4 be ia5, and let the function f(t) be a weighting function,
Assuming that the DC current ld5 is constant, the AC current ja5 is la
5=f(t)・ld5...[3
} can be expressed as

It is also assumed that ia5 is commutated in the direction of the arrow in FIG. 7 at time n·ΔT and in the opposite direction at time (n10) ΔT.
The average value of the AC side current from n△T to (n+1)△T is ia5 (n△T) = (2 input - 1) ld5...
(4}.

Since it can be expressed as t=n△T, we end up with '3', [4- From equation f
(n△T) ld5 = {2 inputs (n△T) - 1} ld5, and transforms into f (n△T) = 2 inputs (n△T) - 1
...'5} relationship exists.

Returning to equation '3', consider infinite switching (△T
→0) and ia(t)=f(t)ld5 are Laplace transformed and la(S)=F(s)ld5...(6
} becomes.

Capital letters such as la(s) and F(s) represent currents and weighting functions in the frequency domain. Therefore, for simplicity, the power conversion switching circuit is constructed using the admittance Y shown in Figure 9.
We will explain how to know the timing (input (t)) to create an equivalent circuit of

If the set admittance is Ya(s), then la(s
)=Ya(s)・Va(s)...So, by substituting it into equation (6), the switching frequency is F(S)
=Ya(S)-Va(S)'If you choose, Ya(S)=
It becomes No. F Moromine and the predetermined Ya(S) is realized.

Since Vo(t) is given by a time function, Ya(s)/l
Using the calculation elements of d, f(t) can be calculated as described below. (f(t) is a time domain representation of F(s)) In other words, the ignition control circuit performs the above calculation, and f(t)
The equivalent circuit shown in FIG. 9 can be created by determining the input (t), calculating the input (t) from the above equation (5), and switching the thyristor of the power conversion circuit at this input (t). Further, the switching frequency for creating the equivalent circuit shown in FIG. 6, in which there is a voltage source vg in series with the admittance Yg and a current source jg is connected in parallel with it, is la(s):Ya(s
)(Va(s)+Vg(s))11g(s) (However, Vg(s) and 1g(s) are expressed in the frequency domain of the voltage source and current source.

) From the formula, F(S) = Budget (Va(S) + Vg(S)
) + 轡... side.

Moreover, the values of all the values on the right side of equation [8} are known, and the switching frequency f(t) can be determined by performing Laplace inverse transformation. Note that Va(s) is the time function Va(
t), and the transfer function Ya(s) is composed of an operational amplifier or the like. When Va(t) is input to the input of the arithmetic circuit formed as above, the output is Ya(s)・Va(s
) is known to appear as a time function. Therefore, Vg(s), 1g(s), etc. are also given as time functions, and V
If we put a(t)+Vg(t) into the input of the arithmetic circuit of Ya(s), add ig(t) to its output, and divide by ld, we get f
(t) is obtained. This calculation method can be used not only as a continuous system but also as a sample value system using a pulse transfer function. Therefore, by conversely switching the power conversion block 11 in the ignition control block 12 of FIG. 4 at the input (t) = 2 switch, the equivalent circuit shown in FIG. 6 can be obtained.

After all, in this example, the equivalent circuit necessary for improving the quality of power can be created by selecting an appropriate value for input (t), so changes in voltage and reactive power can be detected and responded to. By continuously selecting input (t), an equivalent circuit that compensates for voltage fluctuations and reactive power can be created, thereby achieving the function of compensating for voltage fluctuations and reactive power.

For example, variable capacitance or variable inductance can be used to adjust reactive power and improve power factor.
Further, the variable capacitance and inductance can be connected in parallel to a current source, and in conjunction with this, reactive power can also be adjusted. FIG. 8 is a detailed block diagram of the ignition control circuit that selects ON (t), which will be explained below. This block diagram determines the input (t) for creating the equivalent circuit of FIG.

A voltage detection circuit 21 detects an AC input voltage.

From the sum of this and Vg described as the voltage source in FIG. 6, the frequency domain calculation block 22 calculates the first term on the right side of the above equation (8) and converts it into the time domain.

The weight function f(t) is obtained by adding the setting value ig(t)/ld of the current source to this value, and the time domain calculation block 2
In step 3, the input (t)={10f(t)}/2 is calculated to determine the switching input (t). This determined input (t) is inputted to the ignition circuit 25 via the comparator 24 to control the gate of the reverse direction thyristor.

A sawtooth wave generator 26 is connected to the input side of the comparator 24. An oscillator 27 is connected to this sawtooth wave generator 26, and the gate of the positive direction thyristor is directly driven by an ignition circuit 28 from the oscillator 27.

The ignition control block 12 of FIG. 4 configured as described above
When the power conversion switching block 11 is switched according to the time relation input (t) as shown in FIG. 7, the equivalent circuit shown in FIG. 6 is formed, which is used to improve the quality of AC power supply.

Note that the switching method is not only the two-level switching method shown in FIG. 7, but also a three-level switching method as shown in FIG. 10. Also, switching interval (t)
By appropriately selecting , it is possible to create an equivalent circuit in which one or a combination of admittance, voltage source, and current source is possible.

For example, if the admittance is made equivalent to the parallel connection of circuits that resonate in series at the 3rd, 5th, and 7th harmonics, then
The third, fifth, and seventh harmonic removal filters are removed.

Note that the present invention is applicable not only to the third, fifth, and seventh harmonics but also to n-th harmonics. Furthermore, if the variable inductance for reactive power compensation is connected in parallel to the harmonic removal filter, harmonics can be removed and the power factor can be improved at the same time.

Figure 12 shows the impedance Z between the power supply V and the load LD.
12, the load voltage can be adjusted by changing the impedance and the voltage source Vg.

FIG. 13 is a specific circuit diagram of FIG. 12. In FIG. 13, SE is an arbitrary circuit constant element, and PA is a constant current power source of the DC circuit.

Figure 14 shows the case of three-phase balance.The part surrounded by the dotted line in the figure is a circuit in which a current source is connected in parallel to the parallel circuit of variable capacitance and inductance shown in Figure 15. By accommodating power and adjusting reactive power using variable inductance and capacitance, three-phase currents, power, etc. can be balanced.

Note that the circuit constants can be not only the usual R, L, C, etc., but also negative resistance, negative inductance, and negative capacitance.

Further, as shown in FIG. 11, two circuits on the DC side may be connected in series, or three or more circuits may be connected.

However, the filters for removing high frequency ripples shown in FIGS. 5 and 11 are not limited to L and C in the figures.

Since the present embodiment has the above-described configuration, it has the following features. a Since it is possible to generate current and voltage of arbitrary waveform, arbitrary size, and arbitrary range, it is possible to not only accommodate active power and adjust reactive power without disturbing the voltage (current) waveform, but also to adjust the power Waveform improvement can be performed at the same time as compensation.

b Equivalently arbitrary admittance (impedance)
can be generated, so it can be used as an admittance that removes a specific frequency in the current, and in this case there is no need to know the magnitude of the specific frequency component contained in the current.

c It can also have negative impedance, so it can cancel out specific impedance in the circuit.

d.The response is fast because the DC current is kept constant and only the conduction period is controlled.

e Since the magnitude of the DC current is constant, when two or more circuits are used in combination, power can be compensated for each circuit separately without mutual interference.

f Since it is not synchronized with the fundamental wave of the power supply voltage and switches based on the instantaneous value, it can be applied even in places where the power supply voltage is not stable, so it can be connected in series with the circuit to be adjusted to adjust the voltage. It is. As is clear from the above explanation, in a circuit in which the input side of a bridge circuit consisting of a thyristor is connected to an alternating current and a reactor is connected in parallel to the output side, the voltage waveform is disturbed by switching the thyristor at high frequency. First, it is possible to provide a circuit constant generator that has good responsiveness and can be used in combination with a plurality of circuit constant generators.

[Brief explanation of drawings]

Figure 1 shows a conventional power conversion switching circuit, Figure 2A
, B is an operation diagram showing the conventional ignition timing, FIG. 3 is a circuit diagram in which two conventional power conversion switching circuits are connected in series, and FIG. 4 is a circuit constant that is an embodiment of the present invention. A block diagram of the generator, FIG. 5 is a specific circuit diagram of the power conversion switching block in FIG. 4, and FIG.
7 is a diagram showing the switching time relationship in this embodiment, and FIG. 8 is a diagram showing the switching time relationship in this embodiment.
Detailed block diagram of the ignition control block shown in Fig. 9.
Figure 10 is a three-level switching system diagram, Figure 11 is a circuit diagram in which the circuit in Figure 5 is connected in series, Figure 12 is an equivalent circuit diagram for load voltage adjustment, Figure 13 is an equivalent circuit diagram of the load voltage adjustment. FIG. 12 is a specific circuit diagram, FIG. 14 is a three-phase balanced circuit diagram, and FIG. 15 is an equivalent circuit diagram of the main part of FIG. 14. 1, 2, 3, 4, 13, 14, 15, 16...
Thyristor, 5, 6, 17...Reactor, 11...
...Power conversion switching block, 12...
・Arcing control block, 21... Voltage detection block, 22... Frequency domain calculation block, 24...
・Comparator, 25, 28...Ignition circuit. Figure 1 Figure 3 Figure 2 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15

Claims (1)

[Claims] 1. In a power compensation device consisting of a power conversion switching circuit whose AC input side is connected to an AC power supply via a high frequency removal filter by switching, and a reactor connected to the DC output side of this switching circuit, the AC input of the filter is a voltage detection circuit that detects side voltage;
The detection voltage Va(t) of this detection circuit and the set voltage source Vg(
an admittance arithmetic circuit which receives the output of the sum of t) and sends an admittance arithmetic output to its output, and adds a specified current ig(t) to the output of this arithmetic circuit and divides it by the DC current Id flowing through the reactor, a first means for obtaining a switching frequency at an output; a second means for receiving the switching frequency obtained by the first means and obtaining a switching interval (t) at an output; 1. A circuit constant generator comprising: an ignition control circuit that compares the output of the generator with the output of the generator, and sends out an output that switches the power conversion switching circuit at a high frequency based on the comparison output.