JPS6022592B2 - Control method and control circuit for power converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates generally to static power converters and methods of operation thereof, and more specifically to methods for improving the response of converters having controlled rectifiers (thyristors) in the neutral branch. , and an improved firing control circuit for generating a sequence of firing pulses to initiate conduction of a controlled rectifier (thyristor) used in a bridge-type converter.

BACKGROUND OF THE INVENTION Power conversion devices that supply power from an AC power source to a DC load and methods of operating the same are well known.

This type of device is designed to control the magnitude of the output DC voltage and can operate in two or more quadrants. A six-pulse bridge transducer is a typical example.

However, such circuits are characterized by a relatively high ripple content in the load voltage when the output power is low and, moreover, require perfect control of all rectifiers of the bridge device at all times over the entire operating range. be done. It is known that the power factor of this device is relatively poor at low output power. When the negative side is conductive and the load current tends to be continuous, as in the case of motor loads, adding a freewheeling diode reduces the ripple in the load voltage. It is also known that the power factor is improved when the output power is low. However, such converters are not capable of fourth quadrant operation and have a limited range of control. This principle and the change from alternating current to direct current (AC
/DC) Details regarding power converters were published in 1971.
B., published by John Wiley & Sons, Incorporated in 2013. R. Perry's book ``Thyristor Phase Controlled Control
and Cycloconverters”.
Please refer to this book for more details. The input power factor of a six-pulse phase-controlled thyristor bridge converter feeding an inductive load is determined by two thyristors connected to the neutral point of the AC system from the positive and negative busbars followed across the load. It is also known that adding redundancies can improve low voltage operation. This type and its basic circuit are described in Japanese Patent Application No. 52-14618. As will be explained with reference to the drawings later in this application, when a bridge type converter such as that described in this application is operated in the first quadrant with a continuous current at a low DC output voltage, the cycle There is a period during which the respective thyristors in both neutral point circuits conduct.

In this mode of operation, the AC power system is bypassed, resulting in a flat spot in the DC output voltage waveform representing zero output power, which causes the device to transition from first quadrant operation to fourth quadrant operation. Upon voltage reversal when switching, a transport delay or lag time occurs. The present invention is directed to an improved method of operating a bridge type converter using a controlled rectifier. The invention is also directed to an improved ignition control circuit for operating a thyristor bridge transducer. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for controlling the transfer of power between a multiphase AC power source and a load.

Another object of the invention is to improve the control of thyristors in power converters that transfer power between a multiphase power source and a load. Another object is to provide a method for improving the operation of power converters in continuous current devices operating at relatively low power levels.

Another object is to provide a means for improving the operation of a power converter across a plurality of separate modes of operation and allowing automatic and smooth switching between each mode.

Another object is to use an improved ignition control circuit to improve the response of the device during voltage reversals when operating in a continuous current fashion at relatively low power levels.
The present invention provides a method for operating a DC power converter.

In one aspect of the invention, in order to achieve the foregoing objects, a method for controlling power supplied to a load from a multi-purpose (three-phase) AC power supply includes a controlled rectifier in the neutral branch. , selectively controls the conduction period of a controlled rectifier (thyristor) constituting a bridge-type converter.

The method of operation of the invention comprises sequentially conducting each controlled rectifier in each phase branch for at least half the period of electrical phase displacement between the phase voltages to neutral, and then immediately The control rectifier of the point branch is conductive for the remainder of the period. In a three-phase system, each controlled rectifier in each phase branch conducts at least 60 degrees electrical angle, and immediately thereafter the associated neutral branch controlled rectifier conducts for the remainder of the 1200 period.

This action prevents the control rectifiers in the positive and negative neutral branches from conducting at the same time. Furthermore, in order to achieve the above-mentioned object, this invention uses analog An improved ignition control circuit responsive to command signals is provided.

The control circuit is coupled to the alternating current power supply and responsive to the alternating current power supply, the control circuit includes a set of time-related logic whose relative time relationships are constant with respect to the phase voltages of the multiphase alternating current power supply. means for generating a signal, the number of which is equal to the number of thyristors in each phase branch of the converter, selectively coupled to a predetermined number of said logic signals having a constant time relationship and which is longer than one half cycle of each phase voltage; Each ignition reference waveform having a time-varying slope characteristic that repeats periodically over a period is generated, and a portion of the period of successive waveforms has a slope characteristic that overlaps with each other, so that arbitrary thyristors are a plurality of waveform generators for firing in response to two firing reference waveforms; and a plurality of waveform generators coupled to the plurality of waveform generators and an analog command signal to determine the amplitude change characteristics of the firing reference waveforms. circuit means for generating a set of time-variable logic signals in response to a comparison of the signal and the analog command signal; and a digital logic circuit for combining said logic signals according to a predetermined logic control algorithm, generating a firing signal and applying said firing signal to said thyristor.3.
The phase bridge converter uses six waveform generators to
These generate 2400 negative slope ramp voltages 600 apart from each other.

A comparator circuit detects the intersection of each forehead slope voltage and the analog DC command voltage and generates a series of square wave logic signals whose front lines vary according to the magnitude of the command voltage. Another comparator circuit detects the intersection of the phase voltages to the neutral point and the intersection between the phase voltages and generates a set of square waves with constant leading edges. selectively responds to the wave and generates a firing signal according to a combinatorial logic function, which is defined as "a constant pre-off and a variable pre-off when a given command voltage is applied to the converter." In response to the time relationship between the green logic signals, control is provided over five different modes of operation. At this time, even in a three-phase system where the firing angle of the phase branch's thyristor is in the range of 900 to 200, the phase branch's thyristor should be set at least 60 degrees.
The response of the device is improved by allowing the thyristor in the neutral branch to conduct for the remainder of the 1200 period between this phase voltages after conduction. This action prevents the thyristors in the neutral branch from conducting at the same time and eliminates the transport delay or lag time during thick flow when a reverse voltage command is applied. The content of this invention will be described in detail below.

FIG. 1 shows an alternating current to direct current power converter such as that described by Hakama Isoaki.

Before explaining the invention, it may be helpful to briefly explain this type of converter in order to fully understand the invention. In Figure 1, AC power is supplied to the converter from a polyphase (three-phase) power supply represented by three terminals L, L, and L connected to the primary column of a triangularly connected transformer. The secondary winding blade 2 of the transformer has a star-shaped connection, and has three windings A-N, B-N, and C-N. It is well known in power circuits that alternating current power is converted into direct current power and is applied to a load 4 by means of a positive and negative group 16,1 connected in series, each consisting of four controlled rectifiers. The controlled rectifier is shown as consisting of a silicon controlled rectifier, which is a semiconductor device known by the name of a thyristor. In the following description, the term thyristor is used for convenience, but is not limited to this. No. Four sires 28, 22, 24
, 26 constitute a positive group 16 of A0 to N0 ~ thyristor 2, 38? 32 and 34 constitute the negative convergence of A- to N-.

The cathodes of the thyristors of the positive cluster 6 are commonly connected to a positive voltage bus 36, which is coupled to one side of the load chain. Negative Gunryu 8's anode is negative voltage bus 381
This common connection also connects this bus bar to the opposite side of the load chain. The gate electrodes of the two groups of syringes 2Q to 3 are connected to each of the ignition control circuits 48. The voltage applied to the load is controlled in response to the command voltage applied to conduction at a desired point of the phase voltage.

The object of this invention is "this ignition control method and device. It is capable of first and fourth quadrant operation, and at the same time improves the power factor of the device and operates with low output power. At present, devices are known to reduce the voltage ripple of the load when the load is running.
No. 18! Suffice it to say that the addition of a syris converter 84 to the neutral branch as described here results in a significant advance in the control action of the converter. The operations in the four quadrants are shown in Figures 2A to 3.
As shown in the figure. In these figures eight firing angles and eight have to be considered. Q represents the firing angle of the sirens on a particular phase branch, and firing angle 3 represents the firing angle of the sires on the neutral branch. The same can be said for other similar sires. All firing angles are measured from the intersection of adjacent phase voltages to neutral. In Figure 2A,
A typical conventional operation is shown for the conditions Q=1350 and 8=1500.

A set of time-related voltage and current waveforms for eight thyristors 20-34 are shown under phase-to-neutral voltages AN, BN, CN. The voltage +V, for the positive group thyristor, is the positive voltage bus 36 with respect to the neutral point NN of the power supply.
(FIG. 1), 1 V, represents the voltage on the negative voltage bus 38 of the thyristors of the negative group. The respective currents are represented by A0, B+, C0, etc. From the current waveform N0 for the thyristor (hereinafter also referred to as a neutral point thyristor) 26 in the neutral point branch, it can be determined that the thyristor (hereinafter also referred to as a phase thyristor) 20, 22, 24 in an arbitrary phase branch is guided. It can be seen that when the thyristor 26 subsequently conducts, a current is commutated to the conductive neutral point thyristor 26, driving the voltage +V, to zero or NN'. If the conduction period of each phase thyristor is less than 600, the current waveforms N+ and N
-, both neutral point thyristors 26, 34 simultaneously during the inter-pulse period of the phase thyristor, represented by a flat spot or zero voltage level of the waveforms +V, and -V and the composite load voltage V2. It turns out that it is conductive. Second
Figure B is a set of waveform diagrams similar to Figure 2A, except that the firing angle Q has been changed to 1200 and the conduction period of each phase thyristor is longer.

However, the firing angle 6 of the neutral point thyristor is the same. From the voltage waveforms +V and -V, when the firing angle of the neutral point thyristor is constant and the conduction period of the phase branch thyristor becomes long,
It is clear that the voltage V2 across the load and thus the power applied to the load increases, and the period during which the neutral thyristor conducts at the same time correspondingly decreases. This characteristic is
As you can see from the explanation below, this has an important meaning. FIG. 3 shows the normal mode of operation in the fourth quadrant.

At this time, the current in the thyristor of the neutral branch must be commutated to the thyristor of the phase branch, which is positive, so that the conduction then enters the negative voltage region. This situation occurs, for example, when Q is 1200 and P is 2100. Based on this, we will next consider Figure 4. When a reverse voltage command is applied during the period from tl to t2, there is no response since both neutral point thyristors are conducting as described above. The device is activated at time t2 when the syringe of the positive phase branch is fired.
have to wait until A voltage reversal occurs at time t3, at which time the device switches to normal fourth quadrant operation. Fourth
A solution to this problem is shown in Figures 5A and 5B, since eliminating the delay time that exists between tl and t2 as shown in the figure would improve the response of the device during voltage reversal. Similarly, in a three-phase system, for example, immediately after the phase thyristor and the neutral thyristor have been electrically conductive for at least 60 degrees electrical angle, the respective neutral thyristor will It may be controlled so that electricity is conducted between the parts.

Generally speaking, the thyristors in the phase branches should be conductive for at least n/2 degrees in successive cycles of the multiphase supply voltage, where n is the corner of the electrical angle between the phase voltages and the neutral point. , it follows that the thyristor in the neutral branch is conductive for the remainder of the period corresponding to the separation between the neutral-to-neutral phase voltages.

That is, for example, in the case of a three-phase device with reference to FIG.
Setting equal to 1800 gives 600 conduction periods. As a result, the conduction period of the neutral point thyristor also becomes 600. As shown by the DC load voltage V2, no flat spot appears in the voltage characteristics. This is because, as can be seen from the current waveforms N0 and N-, the thyristors in the neutral branch do not conduct at the same time. In other words, the neutral branch transistors are mutually conducting and non-conducting within each cycle of the multiphase power supply. In the voltage waveform V2 of FIG. 5A, the average load voltage is equal to zero because the operating periods of the positive and negative voltages are equal, but if the difference between the firing angle Q and 8 is equal to or greater than 60°, then These firing angles can be changed. As shown in FIG. 5B, at a positive low DC voltage, the firing angle Q can be varied from 90° to 120°, while the angle 8 can vary from 1500° to 1500°, keeping a difference of 600° between the firing angles. It can be changed to 180o. This mode of operation is shown in FIG. 14 as mode m. This will be explained later. FIG. 6 shows that maintaining a minimum conduction period of 60° for each phase thyristor provides better response to voltage reversal commands. In other words, “4th
The traditional transport delay or delay time represented by the period between tl and t2 shown in the figure is eliminated. If the reverse command voltage is applied at approximately the same time as the thyristor of one positive phase branch is conducting, the time between tl and t2 disappears, as shown in Figure 6. If there is a reverse command before time tl or after time t, the time for voltage reversal will be even shorter.Therefore, following the method outlined with respect to FIGS. Controlling the firing of several thyristors improves the dynamic response of the converter when operating in the low voltage range, especially during voltage reversals and switching from first to fourth quadrant operation. In addition to implementing the methods described up to this point, FIGS. 7 to 12 show that, in addition to implementing the methods described up to this point, "for example, five different operating modes including the methods described above are performed depending on the value of the applied DC command voltage. Means are shown adapted to generate thyristor firing pulses according to a digital logic sequence, as will now be described, over a wide operating range.

This operating range is shown in the diagram of FIG. 14 and will be referenced from time to time in the following description. FIG. 7 shows a preferred embodiment thyristor firing control circuit for a bridge type transducer such as that shown in FIG.

This circuit consists of the positive and negative groups of 4-pulse thyristors 6 and 8 thyristor evening firing pulses A+9 B+y . . . N- for the thyristors 28 to 34 forming the blade 8
occurs in the desired order. At this time, the DC output voltage is controlled according to the change in the siren firing angle obtained by applying this firing pulse. Conventional three-phase firing pulse generators typically determine the firing angle of the thyristor by the intersection of a single firing reference waveform, such as a cosine or 1800 linear ramp voltage, and a DC command voltage. However, the present invention uses a plurality of firing reference waveforms equal to the number of thyristors in the phase branch.

These waveforms have a certain time relationship to each other and have an electrical separation between the phase voltages to the neutral point, i.e., an electrical separation equal to half of i80o, producing a time-variable logic signal. used for These logic signals are logically combined with time-constant logic signals for the time relationships of the phase voltages of the AC power supply to automatically perform the proper mode of operation and to ensure smooth transition between modes. Perform continuous switching. The embodiment shown in FIG. 7 includes six oblique signal generators 42a,
42b, 42c . . . 42f are used, and these are coupled to respective AND gates 43a to 43f.

In addition to the head tilt signal generator, a phase-to-neutral point crossing detection circuit 44 and a phase-to-phase crossing detection circuit 46 are provided. The phase-to-neutral crossing detection circuit 44 is adapted to generate a first set of rectangular wave logic signals A, B, C and their complements A, B, C. These signals are connected to the phase voltages AN, BNCN of the power supplies coupled to them.
are constant in time with respect to each other, according to periodic changes in .
The front green and back green or antinodes of these waveforms occur when the sinusoidal phase voltage waveform of the power supply intersects the grid neutral point NN (zero voltage level). The phase-to-phase crossing detection circuit 6 combines the sinusoidal phase voltages AN, BN, CN' of the power supplies to generate a second set of rectangular wave logic signals A, , B, C and their complements A, , B,
,C, is generated. These are paired and selectively applied to the AND gates 43a to 43f. The antinodes of these signals are determined by the respective crossings between the phase voltages and are therefore 30 degrees out of phase in electrical degrees from the first set of reference square waves A, B, etc. The zero firing angle reference for Q and B is defined by waveforms A, B, etc., which are the limits or ends of modal changes and reversals, as will be explained later.

This is a convenient way to set up stop control. Both detection circuits 44? 48 are shown in detail in FIG.
Consists of. These comparators are adapted to generate square waves according to the inputs applied. Comparator 48? 5
0 and 52 have one input connected to the voltage reference NN' which is the neutral point of the secondary winding 12 of the power supply shown in the official map. The other inputs to these comparators are also coupled to the power supply phase voltages AN, BN9CN, respectively. Therefore, comparator 4 generates rectangular wave A, and comparator 5 generates rectangular wave B and C, respectively.Three inverting circuits SQ; 62?
The comparators 64 and 59 are combined to generate rectangular waves A, B, and C, respectively.

The detection circuit turtle 6' is different in how the inputs are applied to its comparators 54, 56, and 58. As shown, the two inputs of comparator 54 are coupled to power supply voltages AN and CN', thus producing a square wave A. Similarly, comparator 56,
58 is square wave B,? C, respectively. Each inbar evening 66, 68, 70! From this, the complement square wave A,?
B, C, are generated. Since the phases of the phase voltages AN, BN, and CN' are separated by 1200 degrees, the waveforms A, , B, and C are also separated by 1200 degrees. However, by using the Tachibana numbers A,,B,,C,, six square waves successively separated by 60o are obtained, and these are sloped in the order of A,,C,,B,A,,C,,B, The signal generators 42a to 42f are integrated individually.
The head tilt signal generators are of the same shape, and a typical example is shown in FIG. The forehead slope signal generator shown in FIG. 9 is the generator 42a shown in FIG. 7, and includes a pair of operational amplifiers 72,
74, which are connected together by an analog switch 76. Analog switch 76 is adapted to be activated by a signal voltage applied to conductor 78 of the circuit. In this embodiment, conductor 78 carries 1200 logic waveforms A,,C, from AND gate 43a. If desired, amplifiers 72 and 74 may be constructed from dual 747 type integrated circuits available on the market. In addition to associated circuitry for applying the DC bias voltages -V and -V, amplifier 74 includes a Miller integrating capacitor 88 and a feedback resistor 82 to the -1 input of operational amplifier 2. It also includes a capacitor 84. This circuit is such that when signals A,.C, are applied, an analog switch 76 controls the output F, of operational amplifier 74;
It is held high for a period of o and then opened so that the integrating capacitor 80 generates a slope signal with a negative slope of 2400. The other five slope signal generators 42b to 42f' are the same as those shown in FIG. 9, and generate the standard slope waveforms F2, F3, F4, F5, and F6, respectively.

These firing waveforms are sequentially separated by 600 from the previous one. This relationship is shown in Army Figure 3. For example, the firing waveform F, slopes downward from 00 to 2400 and
It then becomes high and reaches a height of 1200 mt), and then slopes downward again for 2400 mt.
Repeat this process. FIG. 3 shows that the ignition waveform F2 generated in response to the rectangular wave reference waveform C, OB, applied to the slope signal generator 42b of FIG. 7 is delayed by 600 phase. It shows. Two firing waveforms F,,F
Note that 2 has overlapping sections of 1800.

This relationship applies to each pair of subsequent firing waveforms F3, F4, etc. (F6
,F,) is the same. Generating a forehead slope signal with a negative slope over 2400 would result in an overlap of 1800, but in order to enable multi-modal operation, the present invention uses two firing waveforms in succession, as described below. This overlap is necessary because any phase thyristor must fire in response.

Returning to FIG. 7, the six firing waveforms F, to F
6 is applied to two cross detection circuits 86,88.

The neutral point voltage NN of the device and a variable DC command reference signal are respectively applied to these crossover detection circuits. The cross detection circuit 86 is composed of six comparators 90, 92...100,
In response to firing waveforms F, through F6 intersecting the neutral or zero voltage level of the device, a third set of constant square wave logic waveforms 1, 12, 3...16 are activated, respectively. Occur.
As can be seen in Figure 3 and firing waveform F, this waveform F intersects the zero volt G level at 1200. Therefore, any rectangular waveforms 1 to 16 are i200
generates a logic signal that goes high at a firing angle of . The cross detection circuit 88 has six comparators 102, IQ4; turtles 06, 108;
110, composed of Kii2.

This compares the applied DC command reference with the ramp voltages of the ignition reference waveforms F, to F6, and generates six rectangular wave logic signals X, , X2...X6, respectively. varies according to the intersection point of each ramp voltage with respect to the command reference, as shown for signal X in FIG.
The respective logic inverters 14, 1, 118, . Thyristor firing signal A+9 80...N+ and N- are "two sets of logic signals A, A, 8...C and 1, whose time relationship is constant with each other,
, 12...16 and a set of square wave logic signals X, , X2...& and their respective complements X...
. . . Generated in the firing control logic circuit 126 in response to X6.

The ignition control logic circuit turtle 26 is shown in detail in FIG. 10, the wing diagram, and FIG.
n+Xn-, 10N*) and Xn+,'Zn'Xn120
A digital logical formula of the form Yn is realized (* represents and, 10 represents or). These equations logically gate, ie conduct, the thyristors of the neutral branch of the thyristors of the phase branch. Here, X is the logic signal X,...×
6, and Y is one of the signals 1.・…One of the upstream areas
and Z is one of the signals A, B...C. However, Z, :A, Z=C, Z3i8, Z4=A, Z53
C, Z6=8. When n out is 1, Xn-, is suddenly interpreted. The term N* is interpreted as N0 for a thyristor with a positive phase branch, and N- for a thyristor with a negative phase branch. Next, it will be explained how these formulas control the firing angles of the thyristors 20, 22, 24 and 28, 389 32 of the phase branch and the thyristors 6, 34 of the neutral branch.

FIG. 18 shows "6
Two phase branch logic circuits 128a, 128b, turtle 2 mitsu c...
128f and two neutral point branch logic circuit turtles 30a, 13
0b is the positive and negative thyris evening group angle 6,1 shown in FIG.
8 ignition signals A0 for 8...・It shows that N mountains are generated respectively. A typical phase branch thyristor logic circuit wing 28a is shown in FIG.

It includes a reset type flip-flop 132. This set terminal S is coupled to a set signal SA+. This set signal is defined as ~logic signal X,,1,, so that the following formula can be obtained.
A, X6 and N10 (Figure 12) are a pair of ors. gate 1
34 wo is generated by coarsely combining the blade 36 and the AND8 gate q38. SA+;X, 11,.

(A0 & 1N0) The flip-flop group 32 is reset by the signal RA0.

This signal is a third input with two inputs ±SB and SNA+.
generated by the or gate. These are defined as follows. SB+=X3 130 (B 10 x 20 N 10) S
NA+=X28A. It is reset by the firing of the B+ thyristor 22 of the phase branch that occurs first in time.

A neutral branch logic circuit 130a for the positive pulse group thyristor 26 is shown in FIG.

It has a set G reset type flip-flop 142 whose set terminal S is coupled to the set signal SN+. This set signal is generated by three 4-input AND gates 146, 148, a 3-input OR gate 144 coupled to the output of Tortoise 5Q. The signal SN+ is A0, B0, C+ according to the general logic formula listed above.
Generated whenever any one of three sets of neutral point signals for thyristors 20, 22 and 24 are generated. As a typical example, the signal SNA
This is an AND combination of 2.A.X3 and 1. Flip-flop 142 is reset by applying signal RN0 to reset terminal R. This signal is or. Generated by gate 152. This OR gate is turned on by the signals SA0, SB0, and SC0.
- the corresponding input of any one of the positive group of inputs is applied. Table 1 below shows the 10th
The phase branch logic circuit 12 shown in FIG.
The various combinations of logic signals applied to the 8 and neutral branch logic circuits 1301 are all shown.

Table 1 SA+=X, 11,.

(A ten x 60 N ten) SB ten: X3 ten 13' (B+X2 ten N ten) SC+=X5+ et al.

(C ten x 40 N ten) SA-=X4 ten 141 (A ten x 30 N-) SB-=ne+16.

(B ten x 50 N-) SC- = X2 ten 12.

(C0×.10N−)N+=SN+=(SNA+)10(S
NB ten) ten (SNC ten) N-=SN-=(SNA-) ten (SNB-) ten (SNC-) SNA+=X2・A・X3
1L SNB 10=X418・×5'13 SNC+=X60CGX,.

15 SNA−=×51A.

×6 014SNB-=X.・B.

×2 ・16SNC- = (SNA-) 10 (SB-) RB- = (SNB-) + (SC-) RC- = (SNC-) 10 (SA-) RN+ = (SA+) + (SB+) + (SC-1) RN- =
(SA-)+(SB-)+(SC-) The combinations of the circuits and logic signals described above result in five different operating modes.

These five regimes are determined by the manner in which the thyristors in the phase and neutral branches are fired or not fired, thus producing an output voltage of positive polarity during rectifier operation, but with no reverse polarity. During operation, it produces an output voltage of both polarities. Normalized output voltage V. If ut (normalized) is the ratio of the actual DC output voltage to the maximum possible voltage, then the following expression:
The various modes of operation achieved by different arc angles of the thyristors in the phase and neutral branches resulting from the application of a full range of commanded voltages are shown. Table □ These five operating modes are graphically illustrated in Figure 14.

The positive phase voltage in various formats is also shown in FIG. Next, to explain Fig. 14 and Fig. 15,
In mode 1, Q is variable from 00 to 30o, and is the operating range when the thyristor of the neutral point branch does not fire. Therefore, there is no firing angle of 8 and the normalized output voltages are 1.0 and 0.8
Varies between 66 and 66. Furthermore, Mode 1 shows the conventional method of the three-pulse method without using a thyristor in the neutral branch. The output voltage of the positive group phase branch is illustrated by waveform V, in FIG. This is the case when the firing angle Q of the style branch varies between 30 and 900, and the firing angle 8 of the neutral branch remains constant at 1500.

As a result of this operation, a phase voltage of the form shown by the waveform VO in FIG.
This is typical of the operation of the device described in No. 18 p. Mode m is of primary interest, as it varies Q between the limits of 90° and 12° and fires the thyristor in the neutral branch 60° after Q over the range 150° to 1800°. This is the case.

In this manner, the phase thyristor is made conductive for a period of 600°, followed by the neutral branch thyristor being turned on for 60°.
To guide. This method of operation has been explained previously. It should be noted that mode m occurs at relatively low output levels, ie, in the range of output from 100.5 to 0. This state is shown by the waveform Vm in FIG.
Zero average power is delivered to the load 14 shown. In the operation of mode W, the firing angle Q of the phase IJ star of the phase branch road is 1
20°, the firing angle 8 of the thyristor of the neutral branch is varied in the range from 180° to 240°.

In this movement mode, the rhombus switches to the second quadrant movement,
Power is sent from the load back to the power source. This format corresponds to a range of normalized output voltages from 0 to -0.5. The output voltage waveform of a typical positive thyristor group is shown by waveform VW. The second normalized output voltage is from -0.5 to -1.0.
The quadrant operation is similar to V, and at this time the thyristor of the neutral point branch does not fire, but the firing angle of the thyristor of the phase branch is simply set to 120.
Change the angle between o and 150o.

The angle of 1500 is 3 below the theoretical upper limit of 1800.
This is the limit or end stop of the reversal before 00.

This operation is illustrated by the waveform Vv' shown in FIG. Logic signal X.・・・・・・X and ×.・・・・・・
- Since the front line of The output voltage of is determined, and its operating mode (mode 1-V) is determined. Next, an example of a logic configuration in which smooth switching from one mode to another is automatically performed in response to the amplitude of the DC command voltage with respect to the device's neutral point (zero volts) is shown in FIG. FIG. 17 will be explained.

For example, FIG. 16 shows a combination of logic signals to generate a firing pulse for thyristor 281 of the A ten-phase branch of FIG. From Table 1, the firing logic for this thyristor is SA+iX, 11.・It turns out that (A+KojuN+). That is, ignition is caused by the signal X, or [,. A or 1・Turtle X6 or 1. - Controlled by N0. 16th
The time relationship of the waveforms shown in the figure is as follows: If the DC command voltage is greater than zero, the first green waveform is fixed at 120°.
, shows that waveform X, rises from a logic low value to a logic high value. In this state, the ignition signal for the A0 series 281 is controlled by the leading edge of the square wave X. This is ``0, which is also shown in the graph of the first ship diagram.
It ranges from 1200 to 1200, thus covering formats 1, 0 and m. When the DC command voltage drops slightly below zero, the signal
．． The leading edge of waveform 1 occurs later in time than the leading edge of the fixed square wave 1, whose leading edge is at 1200.Thus, the firing of the thyristor is now determined by waveform 1.
When the DC command voltage further decreases, the ignition is controlled by waveform 1 until the leading edge of the composite signal A+& lags behind 120o, and when the leading edge of the composite signal A0×6 lags behind 120o, the thyristor control is controlled by waveform 1. Therefore, the range of the voltage command where the firing angle o is fixed by 1 is from 0 to -0.5, which is form W in Table 1, and also in the first turtle diagram. When the DC command voltage becomes more negative than the maximum -0.5, the A tenth phase thyristor 20
The ignition of is controlled by winter.

Therefore, the firing angle can be varied from i200 to 150o, where it is fixed by the positive leading edge of waveform A, thus resulting in a mode V. The choice of signal A is due to the limit of inversion for the firing angle This is because it is particularly suitable for determining.

Ideally, the firing angle Q of mode V should extend up to Q = 180G, but in order to achieve commutation of current from one thyristor to another, the maximum angle, commonly referred to as the end Q-stop, must be , must be limited to a value smaller than 1800. The neutral point phase crossing detection circuit 44 is
Generate fixed reference waveforms A and A that change at o ~
In addition, since positive logic is used throughout, reference waveform A can be conveniently used. So choose this. =150
Generates a zero inversion limit. This state is shown as "normal" in Figure 4. In addition to the "normal" reversal limits shown in FIG. In order to ensure that the current is switched to the thyristor of the phase branch at 戊=1200 when the thyristor of the neutral branch is conductive, means are also provided to limit the reversal in "special cases". use

This is done by the logic signal ln·N*. A typical example is signal 1. shown in FIG.・N+. If this signal occurs before the temporally variable front green of A Tomatsu,
This gates the thyristor 20 of the A ten phase branch. This does not occur under normal operation. However, signal 1,
When Q becomes high, that is, Q; 120o, if the thyristor of the neutral branch is conducting, the thyristor of the phase branch is fired; If the thyristor in the phase branch fires at Q = 120o while the phase voltage is This is a well-known prerequisite for correct commutation.The device of the present invention is designed to be able to rapidly enter the deep inversion regime (mode V), so that
* performs the required control action. Over the entire operating range, A
It is noted that the thyristor 20 of the + phase circuit is controlled initially by the ignition reference head slope signal F, and then by the adjacent or immediately previous head slope signal F6, and that an overlap is necessary for switching. I have to point this out.

For this reason, ``In order to control over the entire range, it is necessary to
It is necessary that the slope of the negative slope of 6 spans 240 degrees electrical angle. Since the firing of the thyristor 20 in the A ten-phase branch is controlled by the flip-flop 132 (FIG. 11), when the thyristor 26 in the N+ neutral branch is fired, or after the firing of the thyristor 26 in the B+ phase branch. When 22 is dew-conducted, the gate action ends. From the above explanation, it is determined that
The firing order in m and W is such that thyristor 26 of the N+ neutral branch is gated after the conduction period of each of the thyristors 20, 22, 24 of the positive A+, B+, C+ phase branches. It has become. This gate operation is SN0=(SNA+)
It can be expressed as +(SNB+)+(SNC+).
Similarly, the negative or N-neutral branch thyristor 34 is
A-, B-, C-phase branch thyristors 28, 30, 32
is fired after each conduction period of SN−=
It can be expressed as (SNA-) ten (SNB-) ten (SNC-). In Table 1, the entry SNA+ represents the firing of the N0 thyristor 26 following the conduction of the A+ phase thyristor 20. The logical formula for the ignition period is SNA+=X2・A・X3・1・
It is. Table 1 also shows the formulas for the firing periods of other neutral point thyristors. The timing signal generated by the logic equation for SNA+ is such that, referring to FIG.
It can be said that the phase branch thyristor is gated 600 times later than the normal firing time. This logic is the 17th
This is better illustrated in the time-related waveforms of the figure, which will now be described.

The firing of the thyristor 20 of the A ten-phase branch is initially timed by the negative slope portion of the firing reference waveform F.
The gating of the N+ thyristor 26 over the conduction period of A+ results in the subsequent waveform F2, thus F, and ×, from 60
It is timed by a logic signal X2 that is 0 off. For this reason, S
The NA+trigger signal consists of four signals X2, ×3, A and 1
, occurs when the front green towards the last height of , occurs. Since a window is formed by the AND function of the signals X2 and x3, this gate operation does not exceed 60°. Furthermore, the forward green of the composite waveform A.1 is fixed at 1500,
Then the green is at 240o. This condition results in a mask that limits the firing operation of the neutral point thyristor within the limits of 8=1500 to 2400, as defined in Table B and as shown in FIG. The conditions of Forms B, M and W are met while prohibiting the firing of the neutral point thyristor. While the foregoing has illustrated and described what are presently considered to be preferred methods and embodiments of the invention, modifications thereof will readily occur to those skilled in the art.

For example, all fixed reference waveforms A, 8, C, etc., A,,B,
C, etc. and 1, to 16 can, if desired, be taken from a radix-6 ring counter driven by a pulse oscillator at six times the frequency of the AC power supply. At this time, a phase-locked loop is used to control the oscillator and lock the reference waveform to the AC power source. Furthermore, if desired, it may be constructed entirely digitally by replacing the cervical diagonal voltage and analog command signal with digital diagonal voltages and digital words, respectively. For example, this digital forehead voltage can be derived from a digital counter driven by a voltage controlled oscillator synchronized with an AC power supply at a high multiple of the power supply frequency. At this time, the comparator is a digital comparator. It is therefore understood that the invention is not intended to be limited to the specific details shown and described herein, but rather that the appended claims are intended to cover all possible modifications within the scope of the invention. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a three-phase bridge type power converter using a neutral point thyristor, including the ignition control circuit of the present invention, and FIGS. 2A and 2B are operating in the first quadrant at low power output. A waveform diagram illustrating the operation of a conventional bridge-type converter with a neutral point thyristor, FIG. 3 is a waveform diagram illustrating the conventional operation in the fourth quadrant, and FIG. 4 is a waveform diagram illustrating the conventional operation in the fourth quadrant. Waveform diagrams showing the response characteristics of switching from the first quadrant to the fourth quadrant, Figures 5A and 5B are waveform diagrams illustrating the operating method of the present invention, and Figure 6 is illustrated in Figures 5A and 5B. FIG. 7 is a circuit diagram of the ignition control circuit shown in FIG. 1.
FIG. 8 is a circuit diagram of the cross detection circuit shown in FIG. 7, FIG. 9 is a circuit diagram of a typical crossing signal generator shown in FIG. 7, and FIG. 11 is a circuit diagram of one of the six phase branch logic circuits shown in FIG. 10, and FIG. 12 is a circuit diagram of the neutral branch shown in FIG. 10. A circuit diagram of one of the logic circuits, FIG. 13, is a waveform diagram showing the signal generated by the circuit shown in FIG. 7 as well as a set of firing reference waveforms for controlling the converter of the present invention, FIG. An example of this is the format m shown by the waveforms in FIGS. 5A and 5B. Graphs showing the five modes of operation carried out by the converter of the present invention; FIG. 15 is a waveform diagram showing the voltage waveforms generated in the five modes of operation shown in FIG. 14; FIG. FIG. 17 is a waveform diagram showing how the firing signal for the neutral branch is logically generated according to the invention; FIG. 17 shows how the firing signal for the thyristor of the neutral branch is logically generated according to the invention. FIG. Explanation of main symbols 10...Primary side of transformer, 12......Secondary side of transformer, 14...Load, 16...Positive group, 18... Negative group, 20, 22, 24, 28, 30,
32... Phase branch path thyristor (controlled rectifier),
26, 34...Thyristor (control rectifier) of neutral point branch, 40...Ignition control circuit, 42a to 42
f...Fusion signal generator, 433 to 43f...
AND gate, 44... Neutral point phase crossing detection circuit, 46... Phase crossing detection circuit, 86, 88
...Cross detection circuit, 90, 92, 94, 96, 98
, 100... Comparator, 102, 104, 106
, 108, 110, 112... comparator, 126
...Ignition control logic circuit, 128a to 128f
... Phase branch logic circuit, 130a, 130b...
...Neutral point branch logic circuit. FIGI FIG. 3 FIG3 FIG2A FIGS8 FIG. S to FIGSB FIG. Fuyuuchi G et al. FIG. ? FIG8 FIGIO F■G・“ Inner G is FIG.14 FIG!S 〇≧ Gate & climbing gate GI?

Claims (1)

[Claims] 1. A first controlled rectifier circuit that connects each phase of the power source to the load in order to continuously transfer current between the load and a multiphase AC power source having a neutral point, and the load. A power converter having a second controlled rectifier circuit connected to a neutral point of the power supply, in a method of controlling the rectifier circuit at a relatively low power level to improve response of the power converter. , n being the electrically separating angle between the phase voltages to neutral, the first controlled rectifier circuit at least conducting for n/2 degrees, immediately following conduction of each phase of n/2 degrees, for the remainder of said n degree separation period within each multiphase cycle;
The method comprises causing the second controlled rectifier to conduct, such that the combined conducting and non-conducting operation of the first and second controlled rectifier circuits eliminates non-conducting periods. 2. The method of claim 1, wherein the first and second controlled rectifier circuits comprise a converter circuit consisting of a positive set and a negative set of controlled rectifiers coupled across a load. at least one rectifier of each set is connected to each phase of the power source, and a positive neutral point controlled rectifier and a negative neutral point controlled rectifier are connected to each side of the load and to the neutral point of the source. and the step of conducting the second controlled rectifier circuit follows the conduction period of each n/2 degree of each controlled rectifier of the positive set for the remainder of the n degree period. , conducting the positive neutral point controlled rectifier and following a conduction period of n/2 degrees of each of the set of negative controlled rectifiers;
The method comprises conducting the negative neutral point controlled rectifier during the remainder of the n degree period, thus preventing the positive and negative neutral point controlled rectifiers from conducting simultaneously. 3. The method according to claim 2, wherein the multiphase AC power source is a three-phase AC power source, and n is equal to 120 degrees. 4. In the method set forth in claim 2, n representing the electrically separating angle between the phase voltages to the neutral point is 120 degrees, and each controlled rectifier of the positive and negative sets , and the conduction period of said positive and negative neutral point controlled rectifiers conducting immediately thereafter is also 60 degrees. 5. In the method set forth in claim 2, n representing the electrically separating angle between the phase voltages to the neutral point is 120 degrees, and each control of the positive and negative sets is A method in which the conduction angle of the rectifier is 60 degrees and the conduction period of the immediately following positive and negative neutral point controlled rectifiers is also 60 degrees. 6. In the method set forth in claim 2, the power source is a three-phase AC power source, n is equal to 120 degrees, and the firing angle for conducting the controlled rectifier is equal to the neutral point phase of the AC power source. Measured from the positive intersection of the voltages, the firing angle of the positive set of controlled rectifiers is selectively variable from 90 degrees to 120 degrees, followed by a 60 degree conduction period and correspondingly positive A method in which the firing angle of the neutral point controlled rectifier varies from 150 degrees to 180 degrees, followed by a conduction period of 60 degrees. 7. In the method set forth in claim 2, the power source is a three-phase AC power source, and n degrees is equal to 120 degrees,
The firing angle for conducting the controlled rectifier is measured from the positive intersection of the phase voltage to the neutral point of the AC power source, and the firing angle of the positive set of controlled rectifiers is selectively variable from 90 degrees to 120 degrees; The firing angle of the positive neutral point controlled rectifier is delayed by 60 degrees, and both rectifiers have a conduction period of 60 degrees from each other to improve the response of the device to voltage reversals. 8. In the method as claimed in claim 2, all controlled rectifiers each have a conduction period of 60 degrees, and the commutation from the neutral point controlled rectifier to one controlled rectifier of the positive and negative set comprises: The method occurs when one controlled rectifier of the positive set conducts, upon reversal of power to the controlled rectifier. 9 at least one controlled rectifier coupled between each phase branch of a multiphase AC power supply having a neutral point and a load, and at least one other controlled rectifier coupled between said neutral point and the load; In a power conversion device that transmits power over the entire operating range of rectification and inversion between the AC power source and a load using a converter having a converter, the phase voltage of the AC power source is adjusted in response to a command signal. individually energizing each control rectifier at a predetermined firing angle relative to the intersection between the control rectifiers, respectively corresponding to a plurality of different successive ranges of firing angle α for the control rectifiers of the phase branches according to the command signal; an ignition control circuit for providing a selected one of a plurality of modes of operation, the ignition control circuit being (a) coupled to and responsive to an alternating current power source; (b) a controlled rectifier of said phase branch; and (b) a controlled rectifier of said phase branch. an equal number of circuit means coupled to said first circuit means in response to a predetermined number of said fixed time relationship logic signals for a period longer than one half cycle of each phase voltage;
a plurality of waveform generators for generating respective firing reference waveforms having periodic repetitive amplitude change characteristics that vary in one manner; periods of a portion of the portion overlap each other, any two adjacent ignition reference waveforms are used for ignition of one controlled rectifier, and the ignition control circuit further comprises: (c) a plurality of separate time periods coupled to the plurality of waveform generators and the AC power source and having a constant relative time relationship with respect to the comparison of the ignition reference waveform and zero voltage; second circuit means for generating a related logic signal; and (d) coupled to the plurality of waveform generators and the command signal, the relative time relationship being coupled to the comparison of the firing reference waveform and the command signal. (e) third circuit means for generating a plurality of time-related logic signals that are variable accordingly; and (e) third circuit means that are coupled to said circuit means and that are coupled to said logic signals that have a constant time relationship as well as time-variable logic. in response to the signals, combining the logic signals according to a predetermined logic control algorithm;
and digital logic circuit means for generating an ignition signal responsive to the magnitude of the command signal to obtain a selected mode of operation, and applying the ignition signal to a control rectifier. 10 In the power conversion device according to claim 9, the converter is a bridge type converter, and each of the converters includes a plurality of phase branch controlled rectifiers and a plurality of neutral branch controlled rectifiers. and a negative group controlled rectifier. 11. The power conversion device according to claim 10, wherein the digital logic circuit means includes a first logic circuit means for generating a firing signal for a controlled rectifier in a phase branch, and a first logic circuit means for generating an ignition signal for a controlled rectifier in a phase branch; second logic circuit means for generating a firing signal for a controlled rectifier. 12. In the power conversion device according to claim 11, in the first mode of operation, the first logic circuit means controls the control rectifier of the phase branch in response to a first level command signal. , a variable firing angle α between 0 degrees and 30 degrees, said second logic circuit means for controlling the power for inhibiting operation of the control rectifier of the neutral branch in response to said first level command signal. conversion device. 13. In the power conversion device according to claim 11, the first logic circuit means operates in a second operation mode,
In response to a second level command signal, the second logic circuit means determines a variable firing angle α between 30 degrees and 90 degrees for the controlled rectifier of the phase branch; Depending on the signal, a constant firing angle β for the control rectifier of the neutral branch
A power conversion device that determines the 14. The power converter according to claim 13, wherein the constant firing angle β is approximately 150 degrees. 15. In the power conversion device according to claim 11, in the third mode of operation, the first logic circuit means controls the control rectifier of the phase branch in response to a third level command signal. , a variable firing angle α between 90 degrees and 120 degrees, and the second logic circuit means determines a firing angle α of 60 degrees from the firing angle of the controlled rectifier of the phase branch in response to said third level command signal. A power conversion device that determines a delayed firing angle α (=β+60 degrees) for a controlled rectifier of a neutral branch. 16. In the power converter according to claim 15, the firing angle defines a minimum conduction period of 60 degrees for the controlled rectifier of each phase branch, and then a minimum conduction period of 60 degrees for the controlled rectifier of the neutral branch.
A power conversion device designed to last for a maximum conduction period of 300°C. 17. In the power conversion device according to claim 11, in the fourth mode of operation, the first logic circuit means operates the control rectifier of the phase branch in response to a fourth level command signal. , a constant firing angle α is determined, and said second logic circuit means is configured to set a firing angle α variable between 180 degrees and 240 degrees for the control rectifier of the neutral branch in response to said fourth level command signal. A power conversion device that determines the firing angle β. 15. The power converter according to claim 17, wherein the constant firing angle α is approximately 120 degrees. 19. In the power conversion device according to claim 11, in the fifth operation mode, the first logic circuit means sets a predetermined inversion limit angle of 120 degrees in response to a command signal at a fifth level. A power conversion device in which the second logic circuit means inhibits operation of the control rectifier of the neutral branch in response to the fifth level command signal. 20. The power converter according to claim 19, wherein the inversion limit angle is approximately 150 degrees. 21 In the power conversion device according to claim 9, the ignition reference waveforms are electrically separated from each other by an electrical angle of n/2 degrees, where n is the electrically separating angle between the phase voltages. Power conversion equipment separated by 22. The power converter according to claim 9, wherein the amplitude change characteristic changes substantially linearly over a period of 240 degrees electrical angle. 23. In the power conversion device according to claim 9, the amplitude change characteristic of the ignition reference waveform is composed of a similar waveform whose amplitude gradually decreases over a period in which the amplitude changes. power conversion equipment. 24. In the power conversion device according to claim 9, the converter is a bridge type converter and has six phase branch controlled rectifiers and two neutral branch controlled rectifiers. , wherein the plurality of waveform generators are comprised of six generators that generate six ignition reference waveforms separated by 60 electrical degrees from each other. 25. In the power conversion device according to claim 9, the first circuit means is coupled to the power supply and defines a point of intersection of a phase-to-neutral point voltage with each neutral point. 1
means for generating a second set of digital logic signals coupled to said power supply and defining respective intersections between said plurality of phase voltages; waveform generators are respectively connected to a second set of digital logic signals, and the second circuit means further includes a third set of digital logic signals for determining respective intersection points of the firing reference waveform and zero voltage. the third circuit means comprising means for generating a fourth set of digital logic signals defining the intersection of the amplitude variation characteristic of the firing reference waveform and the command signal; conversion device. 26. In the power conversion device according to claim 9, the converter is a bridge type converter coupled to a three-phase AC power supply, and the first circuit means is configured to convert the three-phase line voltage of the electric wire into phase-to-neutral crossing detection means for generating a first set of square wave signals A, B, C and their complements ■, ■, ■ in response to; , second
Set of square wave signals A_1, B_1, C_1 and its complement ■
, ■, ■, and the second set of rectangular wave signals are separated by 30 degrees from the first set of rectangular wave signals, and the plurality of waveform generation is coupled to said second set of signals A_1, B_1...■ to generate six firing reference waveforms F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, F_1, .
_2,...F_6, the second circuit means generates the six ignition reference waveforms F_6.
It is coupled to _1...F_6, and the waveform F_1...F_
ignition reference waveform zero crossing detection means for generating a third set of six rectangular wave signals I_1, I_2...I_6 when the voltage of the fourth set of rectangular wave signals I_1, I_2...I_6 passes through zero voltage; Wave signals X_1, X_2...X_6 and their complement ■
, ■...■, and the digital logic circuit means is configured by the following logical formula X_n+Y_n・(Z_n+X_n_-_1)
first logic circuit means for generating an ignition signal for the control rectifier of the phase branch according to the following logic formula X_n_+_1
・Z_n・■・Y_n (However, in the above logical formula, + is an OR logic function, ・ is an AND logic function, and X is a signal X_
1...■, and Y is the signal I_1...I_6
Z is one of the signals A, B...■, Z_1=■, Z_2=C, Z_3=■, Z_4
=A, Z_5=■, Z_6=B). 27 In the power conversion device according to claim 26, the first logic circuit means converts N* into a logical formula X_n_+_1·Z generated by the second logic circuit means.
As _n・■・Y_n, the logical formula X_n+Y_n・(Z
A power conversion device that generates _n+X_n_-_1+N*). 28. In the power conversion device according to claim 26, each of the waveform generators generates an ignition reference waveform, and the amplitude change characteristic of the waveform is comprised of a slope signal with a negative slope greater than 180 degrees. power conversion equipment. 29. The power converter according to claim 28, wherein the slope signal having the negative slope spans 240 degrees in electrical angle. 30. The power converter according to claim 28, wherein the ignition reference waveform initially has an amplitude characteristic that does not change over 120 degrees, and then has a slope with a negative slope over 240 degrees. 31. The power conversion device according to claim 9, wherein the controlled rectifier is a thyristor. 32. The power converter according to claim 9, wherein the digital logic circuit means has circuit means according to the control algorithm, and limits the firing angle of the phase branch to the controlled rectifier to a maximum of 150 degrees. A power conversion device that generates an inversion limit control signal. 33. The power converter of claim 32, wherein the digital logic circuit means further comprises a circuit such that the firing angle is at least 120 degrees when the controlled rectifier of the neutral branch is currently conducting. A power converter comprising circuit means for conducting a controlled rectifier of any phase.