JPH0667209B2 - Control device for thyristor converter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control device for a thyristor converter, and more particularly,
Measure the commutation overlap angle to determine the maximum allowable firing angle,
The present invention relates to a control device for a thyristor converter suitable for operating the thyristor converter based on this and maximizing its capability.

[Conventional technology]

It is well known that commutation overlap angles occur in the operation of thyristor converters. This commutation overlap angle is a factor that causes commutation failure during inverter operation of the thyristor converter, and in a general control device, in order to secure a commutation margin angle that is reduced by this commutation overlap angle, The control for limiting the firing angle of the thyristor (generally called α (or β) limiter control) is performed.

The control for limiting the firing angle of such a thyristor converter is described in, for example, Japanese Patent Publication No. Sho 58-49116 "Control device for non-commutator motor".
As disclosed in Japanese Patent Laid-Open No. 2004-242242, there is one in which the size of the commutation margin angle, which changes depending on the size of the load current, is controlled to the necessary minimum.

[Problems to be Solved by the Invention]

However, the control for limiting the ignition angle by the control device is control of the commutation allowance angle itself and is different from the control method of the normal inverter operation represented by the thyristor Leonard device. However, there is a problem such as the existence of waveform distortion due to other thyristor converters, and there is a demand for a control device that limits the firing angle upper limit value that satisfies these.

By the way, the information necessary for controlling the firing angle of the thyristor converter is the power supply voltage, power supply waveform, impedance,
Circuit current etc. can be mentioned. The control device that performs such control generally always recognizes only the circuit current among the above information. For this reason, the other information has to be designed such that a margin (considering the worst value) is added to the design value at the time of device design. It is the actual situation that I am using.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a control device for a thyristor converter that can maximize the capabilities of the thyristor converter.

[Means for Solving the Problems]

The present invention controls a firing angle of a thyristor based on a current command and controls a power supplied to a load in a control device of a thyristor converter, in which the AC part voltage of the thyristor converter is lowered to a set voltage or less. As a starting point, when the AND condition of the drop detection signal and the gate pulse of the thyristor is satisfied,
The period when the drop detection signal is output is measured to measure the commutation overlap angle, and when the ignition angle of the next gate pulse is controlled, the actual value of the commutation overlap angle and the circuit current corresponding to the current command are measured. And estimating the commutation overlap angle at the next commutation based on the firing angle at the time of actual measurement of the commutation overlap angle and the preset correction coefficient related to the waveform distortion of the AC part voltage, The allowable maximum value of the ignition angle is obtained from the estimated value of the commutation overlap angle and the necessary commutation margin angle, and the ignition angle related to the next ignition control is limited to the allowable maximum value or less. .

Here, as the estimated value of the commutation overlap angle, a coefficient K defined by the following equation is obtained from the measured value u of the commutation overlap angle, the circuit current I at that time, and the ignition angle α of the ignition pulse. , K = 1 / I {cos α-cos (α + u)} The coefficient K is corrected based on a predetermined correction coefficient in consideration of the waveform distortion of the AC voltage, and the corrected coefficient K and the current command are obtained. Substituting the corresponding circuit current I into the above equation, it can be obtained as a relational expression with the following firing angle α.

[Action]

Here, regarding the theory used in the present invention, FIGS.
It will be described with reference to FIG.

As shown in Fig. 10, the AC power supply eu _- v is connected to the AC end of the thyristor converter composed of the thyristors U _P , V _P , U _N , and V _N via the AC side inductance L _A, and the thyristor converter is connected. A load M is connected to the DC end of the.

In the circuit of FIG. 10, a waveform diagram of the DC end voltage when a gate pulse is applied to the thyristor converter to commutate is shown in FIG.
Shown in the figure. Assuming that the firing angle is α, the commutation overlap angle is u, and the commutation allowance angle is γ, the allowance angle γ is γ = 180 ° -α-u, as can be understood from FIG. 1) This margin angle γ is a value for allowing normal commutation of the thyristor converter, and is generally determined based on the turn-off time of the thyristor. In order to secure this value, the maximum allowable value αmax of the firing angle α must be αmax ≦ 180 °-(γ + u) (2).

In general, the resistance component on the AC side is sufficiently smaller than the reactance component on the AC side. Therefore, if the AC resistance component is omitted, the commutation overlap angle u is f [Hz] for the power supply frequency and L _A [H] for the AC side inductance. , The circuit current is I [A], and the effective value of the power supply voltage is E [V], From this equation (3), the overlapping angle u is It is represented by. Here, if correct values can be substituted for the power supply frequency f, the inductance L _A , the power supply voltage effective value E, and the circuit current I, u can be obtained accurately, and as a result, αmax shown in the equation (2) becomes an appropriate value. , The ability of the thyristor converter can be maximized.

However, in the prior art, as described above, although the accurate value of the current I is always recognized because of the control variable, other frequencies f, the inductance L _A , and the voltage E have to use the designed values because of the supply information. However, the design error and the power supply voltage error (including the corrugated distortion) have to be taken into consideration to allow a margin. Therefore, the calculated value of the commutation overlap angle u which is considered to occur is inevitably larger than the actual value, and αmax in the equation (2) becomes a small value with a margin, and as a result, the capability of the thyristor converter is increased. There was no choice but to use it with restrictions. In addition, this tendency is particularly strong because the actual supply current is almost always a waveform including distortion.

FIG. 12 shows the commutation overlap angle u when the supplied power supply voltage waveform is distorted by another thyristor converter.
FIG. 6 is a diagram used for explaining that the value is dyed by the formula (4) and is different from the calculated value.

In FIG. 12, (a) is the waveform of the power supply voltage eu _- v shown in FIG. 10, (b) is the AC input voltage e ₁ group of FIG. 10, (e)
Is the enlarged waveform of (a), (d) is the thyristor Up of Fig. 10,
The gate pulse applied to the thyristor V _N , (e) is the current waveform flowing in the thyristor Up in FIG. 10, and (f) is the current waveform flowing in the thyristor Vp in FIG. Note that e _{1 in} (b)
The dotted I _UP dotted and the waveform (e) eu of (a) _- v
Shows the case where there is no waveform distortion.

Here, the commutation overlap angle u in the case of the voltage waveform including the distortion shown in FIG. For the sake of convenience, a case where the distortion is reduced to 1 / n with respect to a sine wave having no distortion in the section of θ _{1 to} θ ₂ will be obtained.

As is well known, the commutation overlap angle u is an angle representing the time during which the current during commutation becomes equal to the current before commutation.

Now, assuming that commutation is started at α (point (e)) and time is t, the current i is (i) α / ω ≦ t ≦ θ ₁ / ω And therefore Becomes

(Ii) In θ ₁ / ω ≦ t ≦ θ ₂ / ω, And therefore Becomes

(Iii) In θ ₂ / ω ≦ t ≦ π / ω, If t ≧ θ ₂ / ω and i = I, then ωt = α + u Becomes Substituting ω = 2πf into the form of equation (3), Becomes If you transform this, Becomes If there is no waveform distortion, then n = 1, so that under this condition, equation (12) becomes equal to equation (4). Since cos θ ₁ > cos θ ₂ and n> 1 are satisfied, the right side of the equation (12) is larger than the right side of the equation (4) in the distorted waveform. Therefore, “u of the equation (12)> ( Equation (4) u) ”.

From the above, estimating the commutation margin angle u using the conventionally known equation (3) or equation (4) causes a large error due to the influence of the power source waveform distortion, and is large in practical use. It's a problem.

To solve this problem, use the second term on the right side of equation (11). By measuring the commutation overlap u, the value of
It can be obtained from the equation and the equation (11).

That is, when the right side of the equation (11) divided by the current I is defined as the measured value K _R of the circuit impedance coefficient, On the other hand, the calculated value K _T of the circuit impedance coefficient is (3)
The right side of the equation divided by the current I, Becomes

Here, K _R is calculated from the equations (11) and (13). Then, by substituting the firing angle α, the actually measured commutation overlapping angle u (the measuring method will be described later), and the current I, K _R can be obtained. The circuit impedance coefficient K is calculated by the following equation using the calculated K _R and the calculated value K _T.

K = K _T + k (K _R −K _T ) ... (17) where k is a correction coefficient and indicates the correction ratio of the difference between the measured value K _R and the calculated value K _T , which depends on the ratio of waveform distortion. Is k = 0.7 ~
It is desirable to set it to 0.8. Further, when there is no waveform distortion, optimum correction can be performed by setting k = 1.0.

If K of the equation (17) is used, the commutation overlapping angle u which is considered to occur next can be obtained by the following equation (18).

u = cos ⁻¹ {cos α−KI} −α (18) Here, since α + u = 180 ° −γ (19) from the equation (1), cos α−cos (α + u) = KI … (20)

Here, α = αmax that can secure the minimum γ = γmin is αmax + u = 180 ° −γmin …… (21), so cosαmax−cos (180 ° −γmin) = KI …… (22) Therefore, cosαmax = KI-cosγmin (23).

The maximum value αmax of the firing angle α allowed from this is αmax = cos ⁻¹ (KI−cosγmin) (24). γmin is a necessary commutation allowance, K is a value obtained from the equation (17), and I is a circuit current.

In other words, by measuring the commutation overlap angle,
In controlling the firing angle of the next gate pulse, equations (16) to (2
0), the actual value u of the commutation overlap angle, the circuit current I corresponding to the current command, and the preset correction coefficient k related to the waveform distortion of the AC portion voltage are used for the next commutation. The commutation overlap angle is estimated, and from Equations (21) to (24), the allowable maximum value αmax of the firing angle is calculated from the estimated value u of the commutation overlap angle and the necessary commutation margin angle γmin. The firing angle α for firing control is limited to αmax or less.

By measuring the commutation overlap angle u in this way, it was understood that the capacity of the thyristor converter can be maximized.

Now, an embodiment that embodies such a theory will be described below.

〔Example〕

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

FIG. 1 is a block diagram showing an embodiment of the present invention.

The configuration of FIG. 1 will be described below. 1 is a power transformer, 2 is a thyristor converter using a power semiconductor conversion element, 3
Is an electric motor, 4 is a field winding of an electric motor, 5 is a current transformer, 6 is a microprocessor, 7 is a bus line, 8 is a memory, 9 is a gate pulse generator, 10 is an analog-digital converter, 11 is a rectifier, 1
2 is a counter for measuring the commutation overlap angle.

Next, the operation of the apparatus shown in FIG. 1 will be briefly described.

The microprocessor 6 takes out the processing contents stored in the memory 8 through the bus line 7, and performs arithmetic operations and input / output processing of other process signals according to the contents.
In the case of current control, the current command value given in advance is compared with the current feedback value input through the current transformer 5, the rectifier 11 and the analog-digital converter 10 and multiplied by a predetermined control gain. The signal is output to the gate pulse generator 9. The gate pulse generator 9 outputs to the thyristor converter 2 a gate pulse having a firing angle corresponding to the given signal. As a result, a current flows through the power transformer 1, the current transformer 5, the thyristor converter 2, and the electric motor 3, and the current is input again through the analog-digital converter 10 to continue the control. Finally, the current is controlled so as to be equal to the current command. The counter for measuring the commutation overlap angle will be described next.

FIG. 2 is a block diagram showing the configuration of the counter 12 for measuring the commutation overlap angle u, and FIG. 3 is a diagram showing the waveform of each part of FIG.

In the configuration of FIG. 2, the same components as those of FIG. 1 are designated by the same reference numerals as those described in FIG. In FIG. 2, 21 is an AC power source, 22 is an AC side inductance L _A
[H], 23 is a level detection circuit for detecting the level of the applied voltage waveform (in the level detection circuit 23, 24 is a current limiting resistor, 25 is a rectifier circuit, 26 is a zener diode, 27 is a photocoupler, and 28 is a resistor. , 31 is a logical sum circuit, 32 is a logical product circuit, 33 is a signal hold circuit, 34 is an inverting circuit, 35 is a counter, and 36 is a digital output circuit.

The operation of FIG. 2 will be described with reference to FIG.

3 (a) shows the waveform of the DC output voltage e _{DC at} the firing angle α and the commutation overlap angle u, and FIG. 3 (b) shows the thyristor 2a of FIG.
(Up), gate pulse applied to thyristor 2d (V _N ),
(C) is thyristor 2b ( _UN ) and thyristor 2c in FIG.
The gated pulse applied to (Vp), (d) the waveform of the AC input voltage e ₁ of the thyristor converter 2 in FIG. 2, and (e) the second
The waveform at 44 in the figure, (f) is the waveform at 45 in FIG. 2, (g) is the waveform at 47 in FIG. 2, and (h) is the value of the counter 35 in FIG. The waveforms in FIGS. 3 (a) to 3 (d) are well-known, so the description thereof will be omitted. Level detection circuit of FIG.
Reference numeral 23 detects the level of the waveform shown in FIG. 3 (d) with the zener diode 26 (determination level shown in FIG. 3 (d)), and functions to supply a current to the photocoupler 27 when the input voltage is higher than this level. As a result, the output signal 44 of the level detection circuit 23 is
The waveform is as shown in FIG. Circuit elements 31 to 33 are provided in order to extract only the commutation overlapping angle u from this waveform. OR circuit 31, the thyristor Up, a gate pulse 41 of V _N, thyristor U _N, takes the logical sum of the gate pulse 42 of Vp, the logical product of the output signal 44 and the output signal 43 at the AND circuit 32 To take. FIG. 3 (f) shows the AND circuit.
There are 32 outputs. The signal hold circuit 33 is a circuit that holds the signal applied to the terminal D at the rising edge of the signal 45 applied to the terminal T and outputs the signal to the terminal 1. When the signal at the terminal C becomes "1", the output terminal This circuit clears 1 (“0”). Therefore, the signals 44 and 4 shown in FIGS.
When a signal 46 obtained by inverting 5 and the signal 44 is applied to the terminals D, T, and C, the output 47 is as shown in FIG. 3 (g). The counter 35 is a circuit that counts the clock signal 48 when the signal 47 is “1”,
It is reset by the signal 49. Therefore, the counter value is as shown in FIG. The logical product of the signals 43 and 44 by the logical product circuit 32 is that the output signal 44 of the level detection circuit 23 may become “1” due to a disturbance other than the commutation. The output signal 44 is input to the T terminal in accordance with the output timing of the gate pulses 41 and 42.

FIG. 4 is a processing flowchart for obtaining the coefficient K shown in the equation (17), which is executed by the microprocessor 6. The start timing of this is signal 47 in FIG.
Is a section of "0". Specifically, when the current waveform crosses the zero point, or when the signal 47 in FIG. 2 is “0”.
It is sufficient to use the time when it became. FIG. 3 (h) is a diagram in which the former is the activation timing.

In block 51, the value of the counter 35 shown in FIG. 2 is read. In block 52, the commutation overlap angle u is set to (25) by the counter value, the clock frequency, and the power supply frequency.
Calculate with an expression.

Here, f: power supply frequency (Hz) fc: clock frequency (Hz) n: counter value The block 54 uses the u, the circuit current I, the firing angle α, and the correction coefficient k to express the equation (16), The coefficient K is obtained from the equation (17). The block 53 is for preventing the calculation error from increasing. When I is smaller than the constant value Ic, the block 54 is switched to the block 55 and K = Kc (constant value) is set instead. In the block 56, the counter 35 is cleared, and the output 49 from the digital output circuit 36 in FIG. 2 is used for clearing.

FIG. 5 is a flow chart of the current control process, and the start timing is not specified.

A block 61 calculates the firing angle α so that the current command given by the current control calculation is equal to the circuit current. In block 62, Kmax obtained from the equations (16) and (17) and the circuit current I are used to obtain αmax from the equation (24). In block 63, a process of comparing the firing angle α calculated in block 61 and αmax calculated in block 62 is performed.

In block 64, when α> αmax, α = αmax is set. In block 65, a process of generating a gate pulse with a firing angle α is performed. As a result, when the ignition angle α obtained by the current control calculation is a value that cannot secure the commutation margin angle γmin, a normal galvanic operation can be performed by correcting it to α that can secure this.

In the prior art, since the calculated value of αmax described above has a marginal value in consideration of design error and power supply voltage error (including waveform distortion), it is often corrected in block 64 of FIG. Therefore, the ability of the thyristor converter must be limited and used.

On the other hand, if the present embodiment is used, the determination can always be made with an appropriate αmax, so that the capacity of the thyristor converter can be fully used. This makes it possible to reduce the power supply voltage, so (1) the power transformer capacity can be reduced (about 10%), (2) the power factor can be improved (about 10%), and (3) low breakdown voltage (about 10%). %) Thyristor element can be used, and (4) various losses that occur during commutation operation of the thyristor can be reduced (about 20%). The above items (1) to (3) are substantially proportional to the voltage, and the item (4) is proportional to the square of the voltage.

Although the present invention has been described with respect to the single-phase circuit, the same effect can be obtained by the same processing in the three-phase circuit. Further, in the level detecting circuit 23 shown in FIG. 2, the Zener diode 26 is used for description, but a comparator or a voltage drop of the diode which exhibits the same effect may be used. Further, although the commutation overlap angle time is measured by the counter, it may be equivalently measured by digitally inputting the signal 47 of FIG. 2 and the number of loops of the software processing.

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7.

The difference between FIG. 6 and the embodiment of FIG. 2 is that the input voltage of the thyristor converter 2 which is the input signal of the level detection circuit 23 is changed to both ends of the thyristor 2a (Up), and the logical product circuit 32 is provided.
One of the input signals is changed from 43 to U _N , Vp gate pulse 42. The numbers in FIG. 6 that are the same as those in FIG. 2 are the same items. The operation of FIG. 6 will be described with reference to FIG. 7 as in the case of using FIG. 3 for the explanation of FIG.

7 (a) to 7 (c) are the same as FIG. FIG. 7 (d) shows the voltage waveform across the thyristor 2a (Up) in FIG. 6 (the same waveform across the thyristor 2d in FIG. 6), and the waveform in FIG. 7 (e) is 44 in FIG. In FIG. 6, (f) is the waveform at 45 in FIG. 6, (g) is the waveform at 47 in FIG. 6, and (h) is the value of the counter 35 in FIG. Fig. 6
The waveform of 44 is the circuit of FIG. 7 (d).
The level is determined in 23, which is shown in FIG. 7 (e). Sixth
The waveform 45 in FIG. 7 is shown in FIG. 7 (f) because of the logical product of the signal 41 in FIG. 7 (c) and (e). The waveform 47 in FIG. 6 is similar to the operation of the signal hold circuit 33 in FIG.
Becomes As a result, the value of the counter 35 in FIG. 6 becomes FIG. 7 (h) as in the case of FIG.

From the above, the same effects as those of FIG. 2 and FIG. 3 can be obtained by performing the processing of the processing flowcharts of FIG. 4 and FIG. However, the start-up timing of FIG. 4 is once for each cycle of the power supply waveform, and the calculation interval of the coefficient K by the actual measurement of the commutation overlap angle is twice as long as that of the second time. The same effect can be obtained if the strains are not significantly different in 1/2 cycle.

Next, a third embodiment of the present invention will be described with reference to FIGS. 8 and 9.

The difference between FIG. 8 and the embodiment of FIG. 2 is that the input signal of the level detection circuit 23 is taken in from both ends of the AC-side inductance 22 and the position of the inverting circuit 34 that establishes the relationship between the signals 44 and 46 is changed. There is a change as shown. 8th
Numbers in the figure that are the same as those in FIG. 2 are the same items. Second
The operation of FIG. 8 will be described with reference to FIG. 9 similarly to the case of using FIG. 3 for the illustration.

9 (a) to 9 (c) are the same as FIG. 9 (d) is a waveform obtained by subtracting FIG. 3 (d) from the AC power supply 21, and FIG. 9 (e) is a signal 44 obtained by inverting the output of the level detection circuit 23 of FIG. 8 by the inverting circuit 34. Waveform, (f) of FIG.
The waveform of 45, (g) is the waveform of 47 of FIG. 8, and (h) is the value of the counter 35 of FIG. Similarly to FIG. 2, the waveform of the signal 47 obtained from the signals 44 and 45 of FIG. 8 is the signal 4 of FIG.
The value of the counter 35 obtained becomes the same as that of FIG. 7 by becoming the same as 7, and by performing the processing of the processing flow charts of FIG. 4 and FIG. The same effect as can be obtained.

〔The invention's effect〕

As described above, according to the present invention, since the commutation overlap angle can be actually measured and an appropriate αmax can be always obtained, the capability of the thyristor converter can be maximized.

[Brief description of drawings]

FIG. 1 is a hardware configuration diagram for controlling an electric motor, FIG. 2 is a block diagram showing a first embodiment of the present invention, FIG. 3 is a waveform diagram showing waveforms of respective parts in FIG. 2, and FIG. 4 is a circuit impedance coefficient. FIG. 5 is a flow chart for explaining the calculation of FIG. 5, FIG. 5 is a flow chart for explaining the current control processing, FIG. 6 is a block diagram showing the second embodiment of the present invention, and FIG. 7 is FIG. FIG. 8 is a waveform diagram showing waveforms at various portions of FIG. 8, FIG. 8 is a block diagram showing a third embodiment of the present invention, FIG. 9 is a waveform diagram showing waveforms at various portions of FIG. 8, and FIG. 10 is a theory of the present invention. FIG. 11 is a circuit diagram showing a circuit used for explaining the above, FIG. 11 is an explanatory diagram of waveforms in FIG. 10, and FIG. 12 is an explanatory diagram of the same theory. 1 ... Power transformer, 2 ... Thyristor converter, 3 ...
Electric motor, 4 ... Field winding of electric motor, 5 ... Current transformer, 6 ...
… Microprocessor, 7 …… bus line, 8 …… memory, 9 …… gate pulse generator, 10 …… analog digital converter, 11 …… rectifier, 12 …… counter, 21 …… AC power supply, 22 …… AC side inductance, 23 ...... Level detection circuit, 31 …… Theoretical sum circuit, 32 …… AND circuit, 33 ……
Signal hold circuit, 34 ... Inversion circuit, 35 ... Counter,
36: Digital output circuit.

Claims (2)

[Claims] 1. A control device of a thyristor converter for controlling an ignition angle of a thyristor based on a current command to control electric power supplied to a load, wherein an AC part voltage of the thyristor converter is lowered to a set voltage or less. Is detected, and when the AND condition between the drop detection signal and the gate pulse of the thyristor is satisfied,
The period when the drop detection signal is output is measured to measure the commutation overlap angle, and when the ignition angle of the next gate pulse is controlled, the actual value of the commutation overlap angle and the circuit current corresponding to the current command are measured. And estimating the commutation overlap angle at the next commutation based on the firing angle at the time of actual measurement of the commutation overlap angle and the preset correction coefficient related to the waveform distortion of the AC part voltage, The allowable maximum value of the ignition angle is obtained from the estimated value of the commutation overlap angle and the necessary commutation margin angle, and the ignition angle related to the next ignition control is limited to the allowable maximum value or less. Control device for thyristor converter. 2. The estimated value of the commutation overlap angle is a coefficient K defined by the following equation from the measured value u of the commutation overlap angle, the circuit current I at that time, and the firing angle α of the firing pulse. K = 1 / I {cos α−cos (α + u)} The coefficient K is corrected based on a predetermined correction coefficient in consideration of the waveform distortion of the AC voltage, and the corrected coefficient K and current are calculated. The control device for a thyristor converter according to claim 1, wherein the circuit current I corresponding to the command is substituted into the above equation to obtain the following relational expression with the firing angle α.