JP2798595B2 - AC / DC converter controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC / DC converter for a DC power transmission system for connecting independent AC systems, which enables stable power supply by changing a control angle at high speed when an abnormality such as an accident occurs. The present invention relates to a control device.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram showing a configuration of a conventional AC / DC converter control device. In the figure, 1 and 2 are independent AC systems, 3 and 4 are transformers, 5 is an AC / DC converter composed of a thyristor bridge for converting three-phase AC to DC,
6 is an AC / DC converter composed of a thyristor bridge for converting DC into three-phase AC, 7 is an AC voltmeter for measuring three-phase voltages Ea, Eb, Ec, and 8 is a three-phase current Ia on the secondary side of the transformer 3 , Ib, and Ic, 9 is a DC current measuring device, 10 is a DC voltage measuring device, 11 is a DC line for transmitting DC power, and 12 is a reactor. Reference numeral 29 denotes an AC / DC converter control device, which is an accident detection / control angle calculator 22 for detecting a power transmission accident or calculating a control angle when a power transmission accident occurs, and a constant current control unit (AC) for performing constant current control.
R) 23, constant voltage control unit (AVR) for performing constant voltage control
24. Constant margin angle control unit (AγR) for performing constant margin angle control
25, a minimum value selecting unit 26 for selecting the smallest one of the calculated control angles, a control for selecting the control angle selected by the minimum value selecting unit 26 or the control angle calculated by the accident detection / control angle calculator 22 Angle selection unit 27, AC / DC converter 5
Has a pulse generator 28 for generating a pulse signal to be supplied to the thyristor gate of the thyristor. 20 is a constant current control unit 23
Is a current setting device for setting the current in the, and 21 is a voltage setting device for setting the voltage in the constant voltage control section 24.

FIG. 12 is a block diagram showing a configuration of a commutation failure prevention circuit included in the accident detection / control angle calculator 22.
3 is a block diagram showing a configuration of a control angle calculation circuit that calculates a control angle after a commutation failure has occurred. In FIG. 12, 3
0 is a three-phase full-wave rectifier, 31 is a commutation voltage EΔ by removing a pulsating flow.
Is a computing unit that calculates the control angle α or β from the commutation voltage EΔ according to the following equations (1) and (2).

[0004]

(Equation 1)

[0005]

(Equation 2)

In FIG. 13, reference numeral 33 denotes a commutation failure detection circuit for detecting commutation failure, which determines and detects commutation failure based on the following formula (3).

[0007]

(Equation 3)

Reference numeral 34 denotes a post-commutation-failure control angle calculator for calculating a fixed control angle after commutation failure.

Next, the operation will be described. AC / DC converter 5
Is controlled by a DC current measuring device 9 and a DC voltage measuring device 10
The constant current control unit 23 and the constant voltage control unit 24 operate so that the DC current value and the DC voltage value measured by the above become the values set by the current setting unit 20 and the voltage setting unit 21,
Each calculates a control angle. Further, the constant margin angle control unit 25 also independently calculates the control angle in order to avoid the margin angle shortage.
The minimum value selection unit 26 employs the minimum value among the control angles calculated by the constant current control unit 23, the constant voltage control unit 24, and the constant margin angle control unit 25, and generates an ignition signal based on the control angle. The signal is output from the pulse generator 28 to the AC / DC converter 5.

In this case, when the input value suddenly changes due to an accident or the like, the control angle calculation is delayed, and as a result, commutation failure or the like is performed, and even after the commutation failure occurs, the same operation as in normal operation is performed. May occur. Therefore, in order to prevent an accident such as a commutation failure, an accident detection / control angle calculator 22 shown in FIG. 11 is provided exclusively to monitor the three-phase voltages Ea, Eb, and Ec, and to reduce the control angle by reducing the voltage value. Calculation is performed, and firing is performed at a control angle corresponding to the calculation result to avoid commutation failure. Further, in the control angle calculation circuit shown in FIG. 13, the commutation failure is detected by the commutation failure detection circuit 33 from the difference between the DC current Idc and the AC current Iac,
After the commutation failure, the control angle calculator 34 outputs a predetermined fixed control angle.

[0011]

The conventional AC / DC converter control device is configured as described above, and a dedicated commutation failure prevention circuit shown in FIG. 12 is used for detecting a power transmission accident and calculating a control angle corresponding thereto. However, there was a problem that was not fully addressed. That is, the three-phase voltages Ea, Eb, Ec
Is detected by the filter 31, the three-phase full-wave rectifier 3
In the filtering for removing the pulsating flow having the output of 0, the response is delayed by about several tens of milliseconds due to the time constant of the filter 31. Further, in the case of an accident involving only one phase, since the three-phase rectification is performed, the influence of the accident hardly appears due to the influence of the sound phase. For this reason, one or more cycles may be required from the occurrence of the accident until the result is reflected in the control angle α, and the update of the control angle α is delayed and commutation fails.
There are issues .

Further, in an accident of only one phase to 3-phase full-wave rectification, the calculated commutation voltage EΔ had another problem of lowering the transmission capacity of the healthy phases to be applied to all three phases.

A commutation failure detection circuit 33 shown in FIG.
In the above, the commutation failure is detected only from the difference between the AC current value Iac and the DC current value Idc in accordance with the above equation (3). In DC power transmission, constant power control is performed, and since the DC voltage is constant, the current set value constantly changes and it is difficult to calculate the optimal control angle. However, there is a problem that transmission power is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and a control angle corresponding to the occurrence of a power transmission accident is obtained at high speed in accordance with a time differential value of a moving average of a measured DC voltage. It is an object of the present invention to obtain an AC / DC converter control device having improved responsiveness in control of a control angle corresponding to occurrence of a power transmission accident.

According to the present invention, the control angle is determined by using a predetermined conversion characteristic based on the measured moving average of the DC current and the AC current and the set value of the DC current, so that the optimum angle according to the situation after the commutation failure has occurred. It is an object of the present invention to obtain an AC / DC converter control device capable of setting various control angles.

[0016]

An AC / DC converter control device according to the present invention time-differentiates a moving average of a measured DC voltage, and obtains a control angle corresponding to the time differential value based on the time differential value. It is provided with conversion means.

According to the AC / DC converter control device of the present invention, a control after commutation failure is obtained by obtaining a control angle by a predetermined conversion characteristic by using a moving average of a measured DC current and an AC current and a DC current set value as inputs. It is provided with conversion means for determining the angle.

[0018]

According to the AC / DC converter control device of the present invention, the moving average of the measured DC voltage is time-differentiated, and based on the time differential value, the control angle is controlled in accordance with the time differential value.
It is possible to control a control angle in response to a power transmission accident promptly.

The AC / DC converter control device according to the present invention comprises:
The control angle is determined from the measured moving average of the DC and AC currents and the DC current set value using a predetermined conversion characteristic, and the control angle after commutation failure is determined, so the optimal control angle according to the situation is set. It becomes possible to do.

[0020]

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. FIG.
Shows an illustration a is sampled and the sampled is voltage waveforms for obtaining a moving average exchange is the basic operation of linear transducer controller, the time from P1 P14 that sampling is performed, V is is sampled The voltage waveform, V (1), is the voltage value sampled for the first time.

The structure of the AC-DC converter controller 11
1 is substantially the same as the configuration of the AC / DC converter control device shown in FIG.
The same parts as those described in 1 are denoted by the same reference numerals and description thereof will be omitted. The accident detection / control angle calculator 22 of the AC / DC converter control device includes a commutation failure prevention circuit shown in FIG. In FIG. 2, reference numeral 35 denotes a moving average voltage calculator (system fluctuation detecting means) which performs a moving average on each phase voltage Ea, Eb, Ec based on three sampling values and calculates a moving average voltage value of each phase voltage. , And a memory (not shown) for sequentially storing each sampling value. Numeral 36 denotes the equations (1) and (2) described in the prior art.
This is an arithmetic unit that performs the operation shown in FIG.

FIG. 4 shows a voltage waveform on the AC side at the time of a single-line ground fault, where Ea, Eb, and Ec are the respective phase voltages. Reference numeral 93 denotes the time when the accident occurred, which indicates that the accident occurred in the a-phase. 94 is the output voltage waveform of the filter 31 shown in FIG. 1 2 conventional AC-DC converter controller 95 is a time when the accident based on the level of the output voltage of the filter 31 is detected.
Reference numeral 96 denotes a voltage waveform based on a moving average calculation result obtained by performing a moving average calculation on the phase voltage Ea.

Next, the operation will be described. When the moving average is performed using three sampling values as shown in FIG. 1, the voltage value V (n) obtained by the moving average is obtained by the following equation (4).

[0024]

(Equation 4)

FIG. 3 shows the voltage value V shown in the above equation (4).
(N) is a flowchart showing a moving average calculation process for the phase voltage Ea in this case. According to this flowchart, first, sampling values V (n), V (n−1), and V (n−1) obtained by sampling the phase voltage Ea are obtained.
(N-2) are sequentially stored in the memory (step ST
1). Next, the past two sampling values V (n-1), stored in the memory immediately before the sampling value V (n),
V (n-2) is read from the memory (step ST
2), these sampling values V (n-1), V (n-
2) and an average value of the sampling values V (n) is calculated (step ST3). Then, the average value obtained in step ST3 is set as the phase voltage value V (N) at the latest sampling time point when the sampling value V (n) is obtained (step ST4). The voltage waveform shown by the solid line in FIG. 4C is the phase voltage value V (N) obtained and observed in this manner.
Of the phase voltage Ea.

In this way, the current sampling value and the past two sampling values up to the present are averaged. Using this moving average, even if there is one abnormal input, the other two
Since the sampling values for the times indicate normal values, the calculated average movement value does not change much, and a result similar to that obtained when filtering is performed is obtained. The moving average voltage calculator 35 shown in FIG. 2 receives the phase voltages Ea, Eb, and Ec individually, performs a moving average independently, and performs a phase voltage value V (N).
Is calculated.

As shown in FIG. 4, when a ground fault occurs only in the phase a, the conventional AC / DC converter controller rectifies the current by the three-phase full-wave rectifier 30 and determines that the other two phases are sound. output to the impact is unlikely to appear, the response because the connection via the filter 31 delay, whereas so the output voltage waveform 94 shown in (b) of FIG. 4, each phase individually by the AC-DC converter controller So that it is not affected by the healthy phase. In addition, since the signal does not pass through a filter, it is observed as a voltage waveform as shown in FIG.

The arithmetic unit 36 includes a moving average voltage calculator 35
The control angle is calculated from each of the voltage values calculated in the above equations (1) and (2), and the orthogonal transformer 5 is controlled by the control angle. The above accident detection / control angle calculator 2
In the second example, the control angle is calculated by using the moving averaged voltage value for each sampling. However, the control angle can be determined by using the differential coefficient of the moving averaged voltage.

FIG. 5 shows another accident detection / control angle calculator 22.
FIG. 2 is a block diagram illustrating a configuration of a commutation failure prevention circuit included in the circuit. The circuit for preventing commutation failure includes phase voltages Ea, Eb, and Ec.
, A moving average calculator 37 for calculating a voltage value by independently performing a moving average to calculate a voltage value, and a differential coefficient-control angle converter 39 having a characteristic 40 shown in FIG. In FIG. 6, β is a control advance angle, and the control angle α is converted by the above equation (2). The moving average calculator 3
7, a differentiator 38 and a differential coefficient-control angle converter 39 correspond to conversion means.

In the accident detection / control angle calculator 22 , the output of the moving average calculator 37 for each phase voltage is differentiated by the differentiator 38 to obtain a differential coefficient, and the control angle is obtained from the characteristic shown in FIG. Responsiveness in control of a control angle when a ground fault or the like occurs without being affected by a sound phase can be improved.

Further, the control angle is calculated using each phase voltage moving averaged for each sampling. However, the DC voltage on the DC line 11 side is moving averaged, and the moving averaged DC voltage is further calculated. It is also possible to determine the control angle based on the degree of voltage drop.

[0032] FIG. 7 is a block diagram showing the configuration of a commutation failure prevention circuit fault detection and control angle calculation unit 22 has in an embodiment of the AC-DC converter control apparatus according to the present invention. This commutation failure prevention circuit includes a moving average calculator 65 for moving average of the output of the DC voltage measuring device 10 to calculate a voltage value, and a degree of change of the DC voltage output from the moving average calculator 65 as a control angle. A Vdc (t) -control angle converter 66 for conversion is provided. Note that the moving average calculator 65 and Vdc (t)-
The control angle converter 66 corresponds to a conversion unit.

In the constant power control, the DC voltage set value is fixed because control is performed by changing the current set value, and thus the DC transmission line is maintained at a constant voltage. Therefore, when the DC voltage of the DC transmission line decreases due to an accident or the like, the situation of the decrease differs depending on the degree of the accident.

FIG. 8 shows a DC line 1 when an accident occurs.
FIG. 4 is a waveform diagram showing a moving averaged DC voltage waveform on the fourth side, and the time from when the DC voltage value starts to decrease to a predetermined level is t4 sec in the DC voltage waveform 61 and t5 sec in the DC voltage waveform 60; Since t4 <t5, the DC voltage waveform 61 indicates the occurrence of an accident larger than the DC voltage waveform 60. Therefore, the control angle is controlled based on the degree of the decrease in the DC voltage waveform. Therefore, Vdc
The (t) -control angle converter 66 has a conversion characteristic as shown in FIG. 6, and can thereby determine the control angle.
The degree of the decrease in the DC voltage waveform can also be obtained by differentiating the DC voltage waveform shown in FIG. 8, and in this case, needless to say, a differentiator is required.

In this embodiment, the DC line 11
Since the control angle is obtained from the degree of the voltage drop of the output of the moving average calculator 65 with respect to the DC voltage on the side, it is possible to improve the responsiveness in controlling the control angle when a ground fault or the like occurs.

Embodiment 2 FIG. Figure 9 is a block diagram showing the configuration of a control angle calculation circuit for calculating the control angle after commutation failure occurs fault detection and control angle calculation unit 22 has in an embodiment of another AC to DC conversion device control apparatus according to the present invention It is. In the figure, 70 is the following equation (5)
And 71 is a converter for converting the calculation result In of the calculator 70 into the control angle β. This converter 71 has the characteristics shown in FIG. Note that the arithmetic unit 70 and the converter 71 correspond to conversion means.

[0037]

(Equation 5)

In the conventional AC / DC converter control device, as shown in the above equation (3), the DC current value Idc and the AC current value Ia
Since the commutation failure is determined by determining whether or not the difference from c exceeds a predetermined value K, the control angle that is updated after the transfer failure is fixed considering that the current set value is constantly updated. It had to be done. On the other hand, in the AC / DC converter control device of the present embodiment, the arithmetic unit 70
The operation shown in is performed. In equation (5), f (Ire
f) is a correction coefficient depending on the characteristics of the power transmission system, and may be a constant for simplification. Then, in consideration of the fact that the current set value is variable, the degree of difference between the DC current value Idc and the AC current value Iac with respect to the current set value Iref is evaluated as shown in Expression (5). Further, the calculation result In of the equation (5) is converted into an appropriate control angle by the characteristic of the converter 71 shown in FIG.

As described above, according to the present embodiment, the control angle is not fixed, and the difference between the DC current value Idc and the AC current value Iac with respect to the current set value is evaluated. An appropriate control angle can be obtained according to the calculation result of (5), an optimal control angle can be set according to the situation, and the transmission power is not unnecessarily reduced unlike the related art.

[0040]

As described above, according to the present invention, the moving average of the measured DC voltage is time-differentiated, and the control angle corresponding to the time differential value is obtained based on the time differential value. Therefore, there is an effect that responsiveness in controlling the control angle corresponding to the occurrence of a power transmission accident or the like is improved.

According to the present invention, the control angle is determined by using the predetermined conversion characteristic based on the measured moving average of the DC current and the AC current and the DC current set value. There is an effect that an optimal control angle can be set according to a later situation.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a basic operation for obtaining the moving average is performed by the exchange linear transducer controller.

2 is a block diagram showing the commutation failure prevention circuit in exchange straight transducer controller.

3 is a flow chart showing a moving average calculation processing for the phase voltage Ea in exchange straight transducer controller.

[4] In a waveform diagram showing a like voltage waveform obtained by performing the moving average calculated for the phase voltage Ea in the AC-side voltage waveform and exchange straight transducer controller of when caused a line ground fault is there.

5 is a block diagram showing the commutation failure prevention circuit in exchange straight transducer controller.

[6] derivative of commutation failure prevention circuit in exchange straight transducer controller - it is a characteristic diagram showing the conversion characteristics control angle transducer has.

FIG. 7 is a block diagram showing a configuration of a commutation failure prevention circuit in the AC / DC converter control device according to one embodiment of the present invention;

FIG. 8 is a waveform diagram showing a DC voltage waveform corresponding to an accident that has occurred for explaining the operation of the commutation failure prevention circuit in the AC / DC converter control device according to one embodiment of the present invention;

9 is a block diagram showing the configuration of a control angle calculation circuit for calculating the control angle after commutation failure occurs in the AC-DC converter control apparatus of another embodiment of the present invention.

FIG. 10 is a characteristic diagram showing conversion characteristics of a converter of a control angle calculation circuit in an AC / DC converter control device according to another embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration of a conventional AC / DC converter control device.

FIG. 12 is a block diagram showing a configuration of a commutation failure prevention circuit in a conventional AC / DC converter control device.

FIG. 13 is a block diagram showing a configuration of a control angle calculation circuit for calculating a control angle after occurrence of a commutation failure in the conventional AC / DC converter control device.

[Explanation of symbols]

 1, AC system 5, 6 AC / DC converter 11 DC line 29 AC / DC converter controller 35 Moving average voltage calculator (system fluctuation detecting means) 37 Moving average calculator 38 Differentiator 39 Differential coefficient-control angle converter (conversion Means) 65 moving average calculator 66 Vdc (t) -control angle converter (conversion means) 70 arithmetic unit 71 converter (conversion means)

Claims (2)

(57) [Claims] 1. A AC-DC converter control device for controlling the control angle of the AC-DC converter for performing conversion between AC and DC in the DC power transmission system that connects two independent sets of AC system, the movement of the measured DC voltage Time derivative of the mean
Calculate the control angle according to the time derivative based on the time derivative
AC-DC converter control apparatus characterized by comprising a conversion means that. 2. A AC-DC converter control device for controlling the control angle of the AC-DC converter for performing conversion between AC and DC in the DC power transmission system that connects two independent sets of AC system, the DC current and AC were measured Moving average of current
Current setting values, and from these input values,
Control angle after commutation failure by calculating control angle based on commutation characteristics
An AC / DC converter control device comprising a conversion unit for determining