JPS6022364B2 - DC circuit control method - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a power supply control device for a DC circuit with a long time constant.
In particular, the present invention relates to a DC circuit control method suitable for controlling DC circuit current to a constant value within a short period of time.

Conventionally, in order to supply a constant current to a DC circuit via a thyristor connected to the secondary side of a transformer, a constant current control method using thyristor gate firing phase control as shown in FIG. 1 has been used. In the figure, 1 is the power receiving system, 2 is the transformer, and 3 is the power receiving system.
is the thyristor bridge, 4 is the DC circuit load coil, 5 is the DC current transformer, 7 is the resistance of the load coil 4, 10 is the DC circuit, and 100 is the gate firing phase control device of the thyristor bridge 3. , automatic pulse phase shifter (hereinafter referred to as "AP") 101, intensifier 102, current deviation detector 10
It consists of 3.

The follower system shown in FIG. 1 forms a closed loop control system using DC current feedback, and controls the gate firing phase of the thyristor bridge 3 according to the DC current deviation signal. When the time constant is large, a relatively large pulsation phenomenon with a long oscillation cycle tends to occur in the DC current, which has the disadvantage that it takes a long time for the DC current to settle down to a constant value.

Furthermore, the resistance value of the resistance 7 of the load coil 4 in FIG. 1 changes depending on weather conditions and usage conditions.

Therefore, if the temperature changes associated with these conditions are large, it is difficult to control the direct current of the direct current circuit 10 at a constant level with high precision. SUMMARY OF THE INVENTION An object of the present invention is to provide a DC circuit control system suitable for controlling the current of a DC circuit to a constant value in a short period of time and with high precision, by eliminating the drawbacks of the conventional system described above.

The operating principle of the present invention will be explained with reference to FIG.

At time L', after applying a constant DC voltage of E to the DC circuit, the time ratio when the DC circuit voltage reaches the target value lo,
, the DC voltage -E2 required to flow a current 12 having a slope -K with the opposite sign of the slope K of 1 is expressed as the DC voltage E2.
, and the voltage applied to the DC circuit after time is E3=E
, -E2. That is, DC circuit 1
When the DC voltage E is applied to the DC current 1, the DC current 1 is...
It is expressed as = thing (・-e-no.t), and the slope K of the DC current 1 at the time ratio,
becomes as follows.

K=thing e-no.t ‐‐‐‐‐...(1} Therefore,
The DC voltage E2 required to flow a current 12 having a slope 1K having the opposite sign to the slope K of the DC current 1 at the time ratio can be determined as follows.

12=Drop {・-e "Base (t-t・)} Crocodile t=t.=≧=-K --21 If we calculate the DC voltage E2 from the above formula '1' and {2}, E2
=-E, e-unit t.

That is, by superimposing this DC voltage E2 on the previous DC voltage at a given time, the DC current can be controlled to a constant target value. In addition, if the temperature change of the resistance component 7 is large due to weather conditions or usage conditions, in order to compensate for the fluctuation of the DC circuit current 1 due to this temperature change, the DC current target value lo and the DC circuit current 1, A correction signal is applied to the DC voltage setting value according to the deviation from the DC voltage setting value. FIG. 3 shows one embodiment of the present invention, which has a configuration that also takes into account temperature changes in the resistance component 7.

In the same figure, the same symbols are attached to the same functions as those in FIG.
109 indicates an intensifier, and 11 indicates a voltage deviation detector. Next, the operation shown in FIG. 3 will be explained.

A thyristor bridge 3 connected to the secondary side of a transformer 2 connected to a power receiving system 1 supplies a constant current to a DC circuit load coil with a long time constant, such as an excitation coil of an electromagnet, by controlling the firing phase of its gate. supply In the starting state of the firing phase control of the thyristor pritz 3, the gate circuit 1
06 is turned off, and the DC voltage set value Eref of the constant current control device 100 is set to E, which provides the rated voltage of the DC circuit 10. This Eref and the DC circuit voltage E detected via the resistor 6 are applied to a voltage deviation detector 1101 to form a voltage deviation output between the Er seal and E. The output voltage of the voltage deviation detector 110 is multiplied by the multiplier 102 and then applied to the APPSIOI. APPSIOI
controls the phase of the gate pulse that fires the thyristor bridge 3 according to the magnitude of the output voltage of the multiplier 102, and forms a DC voltage to be applied to the DC circuit load coil 4. As a result, the DC voltage E, which is the output of the thyristor bridge 3, is always connected to the DC circuit 10, regardless of fluctuations in the received power voltage of the power receiving system 1, since an open loop control system using voltage feedback is configured. The voltage value of can be controlled to a constant value of E. With the start of the firing phase control of the thyristor bridge 3, the DC circuit 10 has E=E=E
, a constant high DC voltage is applied. Therefore, the load coil 4 has the time constant of the DC circuit and the applied DC voltage E,
A direct current flows with a current gradient K determined by . DC current 1 is detected by DC current transformer 5 and applied to comparator 104 . The comparator 104 determines whether the magnitude of the DC current has reached the target constant current value L', and determines whether 1=L
The memory circuit 105 is set by detecting that .
The gate circuit 106 shifts from the off state to the on state in response to the output of the memory circuit 105. Therefore, since E, and the output of the adder 107 -E2 + ΔE are added to the adder 108 from this point on, the output of the adder 108, Eref, changes from E, to E.
ref=E. It changes to 1E20△B. Here, ΔE is a correction voltage for compensating for the temperature change due to the resistance 7 of the load coil 4, and is detected as follows. That is, the current deviation detector 103 forms a deviation output between the DC circuit current 1 and the target current value L. The output of this current deviation detector 103 is multiplied by a multiplier 109 and then applied to an adder 107 as a correction value Δ8 for -E2. As a result, the DC voltage set value Brd after the point when the DC current reaches the target value lo is corrected by ΔE from the initial target voltage value E3=E, -E2 according to the deviation from the target current. Therefore, even if a temperature change occurs in the resistance 7 of the load coil in the DC circuit, it can be sufficiently compensated for, and a highly accurate constant current characteristic can be obtained for a short time and after time t. FIG. 4 is a diagram for explaining the effects of the present invention, where E^ and EB indicate applied DC voltages in the conventional system and the present invention, respectively, and 1^ and IB indicate DC circuit currents in the conventional system and the present invention, respectively.

As shown in the figure, in the conventional method, as the DC current approaches the target value L', the current deviation signal, which is the output voltage for controlling the firing of the thyristor, decreases, so the DC output voltage after firing control decreases from an early point. It's coming.

For this reason, it takes a long response time to reach the target current, and a pulsation phenomenon occurs in the DC current, which requires a long time to settle down to a constant value. On the other hand, when the method of the present invention is implemented (EB, 1^), the highest voltage is always applied to the DC circuit until the target current is reached, so the target current value is reached in the shortest time, and Even after that, the DC current remains constant due to the superposition characteristics described above, and since a sufficient compensation voltage is applied even against fluctuations in resistance value, good constant current characteristics can be obtained. In addition, in this example, since voltage fluctuations in the power receiving system were taken into account, the firing phase control signal of the thyristor was taken as a voltage deviation signal.
When AC voltage fluctuations in the power receiving system are small and can be ignored, there is no need to form a voltage deviation signal, and a so-called open-loop bias voltage application method is used in which the firing phase of the thyristor is directly applied to the automatic pulse phase shifter. Even if the control circuit configuration is simplified, exactly the same effect can be obtained.

Furthermore, in this embodiment, the case where there is a large temperature change in the resistance component 7 of the load coil has been described, but when the variation in the resistance value of the resistance component 7 due to temperature change is small, it is necessary to consider the above-mentioned correction voltage △E. There isn't.

Another embodiment of the invention is shown in FIG.

In this embodiment, the voltage applied to the DC circuit is taken in from the AC system via a tapped transformer and a transformer, and the voltage of the DC circuit is roughly controlled by changing the tap value of the tapped transformer, and fine control is performed by changing the tap value of the tapped transformer. This is done by controlling the firing of a thyristor. In the figure, parts with the same functions as those in Figure 3 are given the same symbols, and 111 is an inverter circuit, 112 and 113 are gate circuits, 2' is a tapped transformer, and 114 is a tapped transformer. 2' is a tap control device, and 3' is a rectifier bridge connected to the secondary side of the tapped transformer 2'. Next, the operation shown in FIG. 5 will be described.

In this embodiment, DC current 1 is detected by DC current transformer 5 and applied to comparator 104 . The magnitude of the direct current in the comparator 104 is a target constant current value 1. The memory circuit 105 is set by detecting that 1=lo has been reached. Therefore, immediately after the thyristor bridge 3 starts firing, the DC current 1 is sufficiently smaller than the target value, and no output is generated in the comparator 104 and the memory circuit 105. Therefore, the gate circuits 106, 11
3 is in the off state, and on the other hand, since the output of the memory circuit 105 is given to the gate circuit 112 via the inverter circuit 111, the gate circuit 112 is controlled to be in the on state in the state of 1<L. Therefore, the tap control device 1 of the tapped transformer 2'
14, tap values n, which are the outputs of the gate circuit 112;
is applied, and a rated AC voltage is applied to the rectifier bridge 3' connected to the secondary side of the tapped transformer 2'.
This state continues until an output is generated at comparator 104 and 112 is controlled to the off state. On the other hand, the gate circuit 10
Since 6 is controlled to be off in the state of 1<L,
The adder 108 is supplied with only the first DC voltage setting value E, which provides the rated DC voltage. Therefore, the voltage setting value Erer of the voltage deviation detector 110 takes E=E until the gate circuit 106 is controlled to be in the on state. The voltage deviation detector 11 is applied with the DC voltage detected through the resistor 6, and the voltage deviation detector 110 is connected to the voltage deviation detector 110.
and E, form a voltage deviation output. The output voltage of this 110 is increased by the intensifier 102, and then the output voltage of the APPSIO
APPSIOI controls the gate firing phase of the thyristor bridge 3 according to the magnitude of the output voltage of the memory circuit 102, and forms a DC voltage E to be applied to the DC circuit load. As a result, the DC voltage B, which is determined by the sum of the outputs of both bridges 3 and 3', constitutes a closed-loop control system based on voltage feedback. The voltage value of 10 is E
, can be controlled to a constant value. By starting the gate firing phase control of the thyristor bridge 3, the DC circuit 1
0, a constant high direct current fin pressure of E=Erd=E is applied. Therefore, a DC current flows through the load coil 4 with a current gradient determined by the time constant of the DC circuit and the magnitude of the applied DC voltage. The comparator 104 operates when 1 reaches the predetermined target current value L', and the memory circuit 10
Set 5. Therefore, an output is generated in the memory circuit 105 from the time when 1;lo is reached, and the output of this memory circuit 105 operates the inverter circuit 111, and the gate circuit 1
12 from the on state to the off state. At the same time, the output of the trust circuit 105 controls the gate circuits 106 and 113 from the off state to the on state. Gate circuit 11
2 is turned off and the gate circuit 113 is turned on,
New tap setting values are applied to the tap control device 114, and the AC output voltage of the tapped transformer 2' changes from the rated AC voltage to the AC voltage value determined by the tap value, for example, by the tap control operation of the tap control device 114. is controlled in steps. On the other hand, since the gate circuit 106 is turned on, E and the output of the adder 107 -E2 + ΔE are applied to the adder 108 from this point on.
Erer, the output of 08, is E, to E, one E2 ten △E
controlled to. Therefore, if the peak is determined so that the magnitude of the AC voltage applied to the rectifier bridge 3' after the transformer tap value of the tapped transformer 2' is controlled carefully, the magnitude of the AC voltage applied to the rectifier bridge 3' is an appropriate value, then the Erer can be reduced to , to E, 1E2 + △E The magnitude of the gate firing phase control angle of the thyristor bridge 3, which is the output of APPSIOI after switching control, can be kept within a certain value, and the DC current after effective switching control can be kept within a certain value. The current is Erer=E
, -E20△B, which is a constant value. On the other hand, the current deviation detection circuit 103 has a DC current of 1 and a target current value of 1. form the deviation output. This one
After the output of 03 is multiplied by the multiplier 109, it becomes 1E.
It is applied to the adder 107 as a correction value ΔE for 2. As a result, at the time t when the DC current reaches lo, the resistance of the load coil, which determines the magnitude of the DC current required to maintain the DC current at a constant value, has a large temperature coefficient, and the load current generates Joule heat. Even if a resistance value change occurs due to such factors, it can be sufficiently compensated for, and good constant current control characteristics can be obtained. Furthermore, in this embodiment, the thyristor bridge 3 only needs to be in charge of minute control of the DC circuit voltage;
The capacity of the thyristor can be extremely small.

The effects of this embodiment are similar to those of the embodiment shown in FIG. 3, and are as shown in FIG. 4.

Also, FIG. 6 shows the characteristics of the AC voltage V^ applied to the thyristor and the gate firing control angle Q^ of the thyristor in the conventional method, and the characteristics of the AC voltage applied to the rectifier when implementing the present invention, in the same state as FIG. 4. It shows an example of the characteristics of the AC voltage VB, the gate firing control angle QB of the thyristor, and the DC voltages EsR and EscR, which are the outputs of the rectifier and the thyristor, respectively. As shown in Figure 6, in the conventional method,
Since the AC voltage applied to the thyristor is always constant, the ignition phase control angle Q^ is shown in the figure because the ignition phase control angle Q^ increases as the current state becomes constant and the DC voltage decreases. It shows similar response characteristics.

As a result, in the constant current state, the reactive power consumption in the IJ star increases due to the increased QA, and the power factor also deteriorates significantly. The increase in reactive power at this time can have negative effects such as lowering the grid voltage depending on the size of the receiving system, so countermeasures such as installing new phase adjustment equipment to compensate for the reactive power consumed by the thyristor are required. Become. On the other hand, in the case of the method of the present invention, as shown in the same figure, the firing phase control angle QB of the thyristor is kept within a substantially constant value regardless of the value of the constant current region. In order to control the AC voltage V8 applied to the rectifier and share only the correction of the small DC voltage in the constant current region with the firing phase control of the thyristor, the thyristor in the constant current region as seen in the slave method is used. Good constant current control characteristics can be obtained without a large or medium increase in reactive power consumed. Further, one embodiment of the present invention shown in FIG.
By detecting that the DC current has reached the target value, the tapped transformer 2 controls the AC voltage applied to the rectifier bridge 3'.
′ tap control is used to reduce the DC voltage shared by the rectifier in the constant current region. The same effect can be obtained by using a method in which the applied AC voltage is interrupted by the detection signal and the DC voltage value borne by the rectifier in the constant current region is zero. Furthermore, the transformer does not need to be separate transformers for the rectifier and thyristor sides; for example, the same effect can be obtained by using a three-winding transformer and connecting one side to the rectifier side and the other to the thyristor side. can.

FIG. 7 shows another embodiment of the invention.

In this embodiment, the rectifier bridge 3' in the embodiment shown in FIG. 5 is removed, and the transformer 2 on the input side of the thyristor bridge 3 is replaced with a tapped transformer 2'. In other words, in this embodiment, when the voltage applied to the DC circuit is greatly changed, the rough control is performed by changing the tap value of the tapped transformer 2', and the fine control is performed by controlling the gate firing phase of the thyristor. It is. The operation and effects of this embodiment are similar to those of the embodiment shown in FIG. 5 and the effect explanatory diagram shown in FIG. 6, and the explanation thereof will be omitted here. FIG. 8 shows another embodiment of the present invention.

In this embodiment, a rectifier is provided in the DC circuit, a tapped transformer is provided on the AC side of the rectifier, and the current in the DC circuit is controlled at a constant level only by controlling the tapped transformer. 0 FIG. 8 shows another embodiment of the present invention,
Components with the same functions as those in FIG. 5 are given the same symbols.

Furthermore, 206, 209 and 210 are comparators, 207 is a current deviation detector, 208 is a storage circuit, 211 is an inverter circuit, 212 to 214 are gate circuits, 215 is a tap value correction device, and 216 is a tapped transformer 2'. A tap control device is shown. Next, the operation of the embodiment shown in FIG. 8 will be explained.

In this embodiment, DC current 1 is detected via DC current transformer 5 and applied to comparator 206 . Comparator 206 is 1
is the predetermined target value 1. An output is generated by detecting that the memory circuit 208 has been reached, and the memory circuit 208 is set. Therefore, no output is generated in the comparator 206 and the storage circuit 208 in the state of 1 L. Therefore, the gate circuit 2 to which the gate signal is applied via the inverter circuit 211
12 is controlled to be in an on state when 1< , and gate circuits 213 and 214 to which the output of the memory circuit 208 is directly applied are controlled to be in an off state. On the other hand, in the state where 1<, the tap value n is given to the tap control device 216 of the tapped transformer 2' via the gate circuit 212, so that the output AC voltage of the tapped transformer 2' is controlled by the rectifier bridge. 3' is set so that the output DC voltage takes the maximum value. As the DC current increases and reaches 1=lo, the comparator 206 produces an output and operates the storage circuit 208. Therefore, since 1=W has been reached, the output of the inverter circuit 211 is inverted, the gate circuit 212 is controlled from the on state to the off state, and the memory circuit 208 is controlled from the on state to the off state.
The outputs shift the gate circuits 213 and 214 from the off state to the on state, respectively. As a result, the tap control device 216 receives the gate circuit 213 from the time when 1=L' is reached.
and 214, the tap of the tapped transformer 2' is controlled by the operation of the tap control device 216 to change the tap value from n to An2. The current deviation detection circuit 207 detects the deviation between 1 and lo, and applies the current to the comparators 209 and 21. Comparator 2
09 generates an output when the current deviation detected by the current deviation detector 207 is positive and exceeds a predetermined value Vo, while the comparator 210 generates an output when the current deviation detected by the current deviation is negative and exceeds a predetermined constant value -Vo. Outputs are generated in the following cases and the respective outputs are applied to the tap value correction device 215. The tap value correction device 215 is a comparator 209 or 21
forming a tap correction value for the − by the output of 0;
is applied to the gate circuit 214. Therefore, when the current deviation reaches 1 L', the current deviation is zero, so the comparators 209 and 2101 produce no output, and Δw becomes zero. Therefore, since 1=lo has been reached, the tap value of the tapped transformer 2' is changed from n by the tap control device 216 to the peak △n2.
From this point on, the output AC voltage of the tapped transformer 2' is controlled in a stepwise manner so that the DC voltage of the DC circuit reaches the target current value. The DC current gradient after this point becomes zero if there is no change in the resistance component 7 of the load coil 4, and the current state shifts to a constant current state. Further, when Joule heat or the like generated by direct current flowing through this resistor 7 is large, the resistance value of this resistor 7 changes, and this change in resistance value causes a decrease in current. If the deviation between the DC current 1 and the target value at this time exceeds a certain value, an output is generated from the comparator 209 or 2101. The tap value correction device 215 is a comparator 209 or 21
Since an output of 0 is generated, a correction value Δ~ for the tap value is output to the gate circuit 214. Gate circuit 214
is always controlled to be on after reaching 1=lo, so the output of the tap value correction device 215 is applied to the tap control device 216 via the gate circuit 214. As a result, if a deviation of a certain value or more occurs in the DC current flowing through the load coil 4, the tap value of the tapped transformer 2' is corrected. Therefore, the DC voltage that is the output voltage of the rectifier bridge 3' is corrected, and the DC current after reaching 1=L can be controlled within a predetermined constant value. FIG. 9 is a diagram illustrating the effects of the present invention. The characteristics shown in the figure show the results when the resistance component 7 of the load coil of the DC circuit has a large temperature coefficient, and the solid line shows the DC voltage-current characteristics when the method of the present invention is implemented, and the dotted line shows the DC voltage-current characteristics when implementing the conventional method. be. As shown in the figure, in the case of the conventional method, as the DC current approaches the target value, the current deviation signal that determines the phase angle at the gate point of the syringe becomes smaller, so the applied DC voltage decreases from an early point in time. As a result, the rise of the DC current slows down, relatively large fluctuations occur in the DC current, and it takes a long time to reach a constant current.

In contrast, when the present invention is implemented, as shown in the figure, the DC current after tap value switching control is within a certain range, exhibiting good constant current characteristics, and the DC current is maintained within a constant range until the target current is reached. Since a high DC voltage is always applied during this period, a constant current state can be established in the shortest possible time. In addition, in the case of this embodiment, the AC voltage to DC voltage converter can be replaced with a rectifier, which is cheaper than the SIRIS type, as in the slave type, and the control device can be a simple tap control device. Even when the capacity is increased, there is no need for phase adjusting equipment to compensate for the reactive power consumed by the AC/DC converter, so a constant current control device with good cost performance can be obtained.

Note that in the above embodiment, it is detected that the DC current 1 has reached the target value lo, but at this point t. Of course, may be set in advance using a timer or the like.

[Brief explanation of the drawing]

Fig. 1 is an example of a conventional constant current control method using thyristor gate firing control, Fig. 2 is a diagram explaining the operating principle of the present invention, Fig. 3 is an embodiment of the present invention, and Fig. 4 is a diagram of the present invention. Figures 5, 7 and 8 are diagrams explaining the effects of one embodiment of the invention, Figures 5, 7 and 8 are diagrams explaining the effects of other embodiments of the invention, respectively. It is. Explanation of symbols, 100... Constant current control device, 10
1...Automatic pulse phase shifter (AP), 102,
109... Multiplier, 103... Current deviation detector, 104, 206, 209, 210... Comparator, 105, 208... Memory circuit, 106 ，
112, 113, 212-214... Gate circuit, 107, 108... Addition circuit, 110...
... Voltage deviation detector, 111, 211 ... Inverter circuit, 114, 216 ... Tap control device, 20
7...Current deviation detector, 215...Tap value correction device. Many illustrations, 2 mice, 3 illustrations, 4 illustrations, many S illustrations, 8 illustrations, and eagle? Hakokyu 58

Claims (1)

[Claims] 1. In a DC circuit control method in which the current in a DC circuit is changed by controlling a thyristor bridge connected to an AC system, and then a constant current is supplied, the voltage of the DC circuit and its set voltage are It is equipped with a voltage control device that controls the gate of the thyristor bridge according to the deviation of A DC circuit control method characterized in that a second set voltage sufficient to set a DC current to a predetermined value is applied to a voltage control device. 2. In a DC circuit control method that changes the current in a DC circuit by controlling a thyristor bridge connected to an AC system and then supplies a constant current, the output is adjusted according to the deviation between the current in the DC circuit and its set current. a current control device that controls the gate of the thyristor bridge according to the deviation between the voltage of the DC circuit and its set voltage;
After the voltage of the DC circuit reaches a predetermined value corresponding to the set current, a second set voltage sufficient to set the DC current to the predetermined value is applied to the voltage control device, and the current control device A DC circuit control method characterized in that the second set voltage is corrected by the output of the DC circuit. 3 In a DC circuit control method that changes the current in a DC circuit by controlling the gate of a thyristor bridge connected to an AC system via a transformer with taps and the tap of the transformer with taps, and then supplies a constant current. , equipped with a current control device that provides an output according to the deviation between the current of the DC circuit and its set current, and a voltage control device that controls the gate of the thyristor bridge according to the deviation between the voltage of the DC circuit and its set voltage. When changing the current of the DC circuit, a first set voltage is applied to the voltage control device, and after the current of the DC circuit reaches a predetermined value, a second set voltage is applied to the voltage control device, which is sufficient to set the DC current to the predetermined value. A DC circuit control method characterized by providing a current to the current and adjusting the tap of a transformer with a tap based on the output of a current control device. 4 In claim 3, instead of connecting the thyristor bridge connected via the tapped transformer to the DC circuit, the thyristor bridge is connected via the rectifier and transformer connected via the tapped transformer. In addition to connecting the thyristor bridge in series with the DC circuit, tap switching of the tapped transformer is performed to change the DC current to the specified value when the current in the DC circuit reaches a specified value. A DC circuit control method that determines the tap position so that the 5. The DC circuit control method according to claim 3, wherein the second set voltage is corrected by the output of the current control device after the current in the DC circuit reaches a predetermined value. 6. Connect a rectifier connected to the AC system via a tapped transformer to a DC circuit, change the current in the DC circuit by controlling the tap value of the tapped transformer, and then supply a constant current. The DC circuit control system includes a tap control device that controls the tap value of the tapped transformer, and sets the tap value to a value commensurate with the first voltage to be applied to the DC circuit when changing the current, and controls the current of the DC circuit. A direct current circuit control method, characterized in that the tap value is switched to a second voltage for setting the target current at the time when the tap value reaches the target current. 7 In claim 6, the invention is provided with a current control device that provides an output according to the deviation between the current of the DC circuit and its set current, and after the current of the DC circuit reaches the target current, the current control device is A DC circuit control method characterized by slightly modifying the second tap value based on the output.