JP6559501B2 - Control device for power converter - Google Patents

Description

  Embodiments of the present invention relate to a control device for a power converter disposed at both ends of a DC power transmission line in order to transfer power between two power systems connected via the DC power transmission line.

  DC transmission (HVDC: High Voltage Direct Current) is economically advantageous over AC transmission for long-distance transmission because it has low transmission loss and low construction costs for transmission facilities. Furthermore, because of the interconnection of different frequency systems and quick response, DC power transmission is also used to improve the efficiency of AC systems. In recent years, long-distance DC power transmission has increased further for the purpose of introducing international interconnection and renewable energy. In the converter technology for that purpose, separately excited power converters to which thyristors are applied are technically mature and have low loss, so that they are mainstream in high-voltage and large-capacity DC power transmission. The power converter is disposed on both sides of the current transmission line.

  The power converter is normally controlled by a control device. A conventional power converter control device includes a constant current control circuit (ACR) that can control a direct current to a specified value, a constant voltage control circuit (AVR) that can control a direct current voltage to a specified value, and a margin angle to a specified value. A constant margin angle control circuit (AγR) that can be controlled and a minimum value selection unit that selects the minimum value of the outputs are configured to control the firing angle of the power converter. In normal operation, the forward converter side controls the control angle on the forward converter side so that the DC current matches the DC current command value in the constant current control mode, and the reverse converter side converts the DC voltage to DC voltage in the constant voltage control mode. The control angle on the inverter side is controlled so as to match the command value. In addition, the power converter on the upstream side of the DC transmission line is referred to as a forward converter, and the power converter on the downstream side is referred to as an inverse converter.

"A novel method to mitigate commutation failures in HVDC systems." Zhang, Lidong, and Lars Dofnas. Power System Technology, 2002. Proceedings. PowerCon 2002. International Conference on. Vol. 1. IEEE, 2002.

JP 2000-139084 A

  However, in a DC power transmission system to which a separately-excited power converter is applied, the commutation of the converter due to an AC system fault on the reverse converter side cannot be normally performed, and a plurality of paths of the converter are simultaneously conducted and short-circuited ( (Commutation failure) may occur. In particular, in the long-distance DC power transmission system, even if the fault current on the reverse converter side increases, it takes time to affect the forward converter side, and it is difficult to effectively control it. The operation of the constant margin angle control on the reverse converter side is slow, and there is a problem that commutation failure cannot be reliably prevented due to delay in securing the margin angle.

  More specifically, when the voltage drops due to a system fault, the current flowing through the thyristor valve increases, the overlap angle μ increases, and the margin angle γ decreases. If the margin angle γ is smaller than the arc extinguishing time of the thyristor valve, the thyristor valve cannot establish a forward voltage blocking capability, and will conduct even if there is no gate signal when the next forward voltage is reached. There is a case.

  The embodiment of the present invention has been proposed in order to solve the above-described problems of the prior art. The purpose is to provide a control device for a power converter that can quickly secure a margin angle and more reliably prevent commutation failure.

A power converter control device according to an embodiment for achieving the object as described above is provided at an end of a DC power transmission line connected to an AC power system, and converts the AC power into DC power. In the control device, the first voltage detection unit for detecting the voltage of the AC power system and the control for controlling the margin angle of the power converter to be constant based on the voltage detected by the first voltage detection unit. A constant margin angle control unit that outputs an angle; a second voltage detection unit that detects the voltage of the AC power system on the input side at a higher speed than the first voltage detection unit; and the second voltage detection unit. An auxiliary constant margin angle control unit that calculates a constant margin angle auxiliary value based on the voltage detected by the step and outputs the constant margin angle auxiliary value as a limit value of the control angle of the constant margin angle control unit. And the second voltage detector is connected to the alternating current on the input side. The voltage of each phase of the three-phase AC flowing through the power system is detected, and the auxiliary constant margin angle control unit is configured to detect the constant margin angle based on the voltage of each phase detected by the second voltage detection unit. An auxiliary value is calculated, and the auxiliary constant margin angle control unit converts the voltage of each phase detected by the second voltage detection unit from a three-dimensional coordinate system to a two-dimensional coordinate system; and the coordinate conversion And a voltage value calculation unit that calculates a voltage for calculating the constant margin angle auxiliary value from the two-dimensional voltage value obtained by the unit .

It is a block diagram of the DC power transmission system of 1st thru | or 6th embodiment. It is a block diagram of the auxiliary | assistant constant margin angle control part and constant margin angle control part of 1st Embodiment. It is a detailed block diagram of the auxiliary fixed margin angle control part of 1st Embodiment. It is a graph for demonstrating the effect at the time of applying the auxiliary | assistant constant margin angle control part of 1st Embodiment. It is a block diagram of the control apparatus of the converter of 2nd Embodiment. It is a block diagram of the auxiliary | assistant constant current control part of 2nd Embodiment. It is an equivalent circuit diagram of the DC power transmission system of the second embodiment. It is a graph for demonstrating the effect at the time of applying the auxiliary | assistant constant current control part of 2nd Embodiment. It is a block diagram which applied the commutation failure prevention part of 3rd Embodiment. It is a detailed block diagram which applied the commutation failure prevention part of 3rd Embodiment. It is a graph explaining the fixed pattern of the margin angle operation amount of 3rd Embodiment. It is a graph for demonstrating the effect of the commutation failure prevention at the time of a three-phase accident at the time of applying the converter control apparatus of 3rd Embodiment. It is a graph for demonstrating the effect of the commutation failure prevention at the time of a three-phase accident at the time of applying the converter control apparatus of 3rd Embodiment. It is a graph for demonstrating the effect of the commutation failure prevention at the time of the single phase accident at the time of applying the converter control apparatus of 3rd Embodiment. It is a graph for demonstrating the effect of the commutation failure prevention at the time of the single phase accident at the time of applying the converter control apparatus of 3rd Embodiment. It is a detailed block diagram which applied the commutation failure prevention part of 4th Embodiment. It is a graph explaining the example of the margin angle pattern calculation at the time of the accident detection by the commutation failure prevention part of 4th Embodiment. It is a block diagram of the control apparatus of the converter of 5th Embodiment. It is a block diagram of the control apparatus of the converter of 6th Embodiment.

[First Embodiment]
[1. Configuration / Operation]
A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a DC power transmission system according to the present embodiment. The power converter has the same configuration on the forward converter side and the reverse converter side. FIG. 2 is a configuration diagram of the auxiliary constant margin angle control unit and the constant margin angle control unit of the present embodiment. FIG. 3 is a detailed configuration diagram of the auxiliary constant margin angle control unit of the present embodiment.

  The DC power transmission system of the present embodiment has a configuration as shown in FIG. At both ends of the DC power transmission line 5, a pair of DC reactors 4-1 and 4-2, a pair of power converters 3-1 and 3-2, and a pair of converter transformers 2-1 and 2-2 are arranged in this order. Be placed. Control devices 7-1 and 7-2 for the pair of power converters are connected to the pair of power converters 3-1 and 3-2, respectively. In the DC power transmission system that can transmit power in both directions, the power converter control devices 7-1 and 7-2 on both sides have the same configuration, and hereinafter, both are collectively referred to as the power converter control device 7. Further, the power converters 3-1 and 3-2 have basically the same configuration and are collectively referred to as the power converter 3. Note that the DC power transmission system can transmit power in both directions. When power is transmitted from the power converter 3-1 side to the power converter 3-2 side, the power converter 3-1 is a forward converter, When the power converter 3-2 is an inverse converter and power is transmitted from the power converter 3-2 side to the power converter 3-1, the power converter 3-2 is a forward converter, the power converter 3- Reference numeral 1 denotes an inverse converter.

  The power converter control device 7 allows power to be exchanged between the two power systems 1 and 2 connected via the DC power transmission line 5, and the control device 7 includes both ends of the DC power transmission line 5. Is controlled. In the control device 7 of the power converter 3, the constant current control unit 8, the constant voltage control unit 10, and the constant margin angle control unit 14 are connected upstream of the minimum value selection unit 17, and upstream of the constant margin angle control unit 14. The margin angle calculation unit 13 and the auxiliary constant margin angle control unit 16 are connected. The first voltage detection unit 11 is connected upstream of the margin angle calculation unit 13, and the second voltage detection unit 12 is connected upstream of the auxiliary constant margin angle control unit 16.

Constant current control unit 8 controls so as to follow the direct current I _d obtained from the DC transmission line 5 through the power converter 3 into a direct current setting value I _dp by the feedback control or the like. More specifically, the constant current control unit 8 inputs the DC current set value I _dp and the DC current I _d and outputs the control angle α _ACR based on the difference between them, and the control angle α is controlled based on the α _ACR. by being, to follow the direct current I _d in the DC current set value I _dp.

The constant voltage control unit 10 controls the DC voltage V _d acquired from the DC power transmission line 5 via the power converter 3 to follow the DC voltage set value V _dp by feedback control or the like. More specifically, the constant voltage control unit 10 inputs the DC voltage set value V _dp and the DC voltage V _d and outputs a control angle α _AVR based on the difference between them, and the control angle α is controlled based on α _AVR. As a result, the DC voltage V _d is caused to follow the DC voltage set value V _dp .

The first voltage detector 11 is a low-speed and high-precision converter transformer to reduce the influence of small AC voltage fluctuations that occur during normal operation, such as voltage distortion, compared to the second voltage detector 12. It is set to detect the primary AC voltage _Vac of the devices 2-1 and 2-2.

The second voltage detector 12 detects the three-phase voltages V _A , V _B and V _C of the AC bus connected to the converter transformer 2 on the primary side (input side). The second voltage detection unit 12 is three-phase faster than the first voltage detection unit 11 so that the auxiliary constant margin angle control unit 16 operates to ensure the margin angle γ quickly when an accident occurs. The voltages V _A , V _B and V _C can be detected.

The margin angle calculation unit 13 converts the voltage V _ac detected by the first voltage detection unit 11 into a secondary (output side) AC voltage, and calculates the margin angle γ _meas1 by the following equation (1). .

However, _Xt : Commutation impedance, _Id : DC current, _ELL : Transformer transformer secondary side line voltage.

The constant margin angle control unit 14 controls the margin angle γ of the power converter 3 to be constant. More specifically, the constant margin angle control unit 14 performs PI control based on the difference between the margin angle calculation value γ _meas1 output from the margin angle calculation unit 13 and the margin angle setting value γ _ref1 to convert power. The control angle α _AγR of the power generator 3 is calculated, and the margin angle γ is controlled to be constant by determining the control angle α of the power converter 3 based on the calculated value. Here, the margin angle set value γ _ref1 is set in advance by the administrator of the DC power transmission system in the control device 7 of the power converter.

The minimum value selection unit 17 determines the minimum value among the output values α _ACR , α _AVR , α _AγR of the constant current control unit 8, constant voltage control unit 10, and constant margin angle control unit 14 as the control angle α of the power converter 3. Set as.

Auxiliary constant margin angle control unit 16, a constant margin angle based on the second voltage detector 12 is a three-phase voltage _V A has been _detected, V B, _{V C} and the DC current _{I d} and the auxiliary margin angle set value gamma _ref2 A constant margin angle auxiliary value AγR _SUP for determining the control angle α _AγR that is an output value of the control unit 14 is calculated and output to the constant margin angle control unit 14. Here, the auxiliary margin angle set value γ _ref2 is set in advance by the administrator of the DC power transmission system in the control device 7 of the power converter.

  More specifically, the auxiliary constant margin angle control unit 16 includes a low-pass filter 16-1 that smoothes the three-phase voltage detected by the second voltage detection unit 12, and an AC voltage and a DC current that are smoothed by the low-pass filter 16-1. And a determined value calculation unit 16-2 that calculates the control angle of the power converter 3 based on the set value of the margin angle.

As shown in FIG. 2, a coordinate calculation unit 15 is arranged between the auxiliary constant margin angle control unit 16 and the second voltage detection unit 12. The coordinate calculation unit 15 includes a coordinate conversion unit 15-1 and a voltage value calculation unit 15-2. The coordinate conversion unit 15-1 uses the following formulas (2) to (i) from the three-phase voltages V _A , V _B , and V _C input from the second voltage detection unit 12 to convert the αβ coordinates from the abc coordinates. The voltage value calculation unit 15-2 calculates the voltage value V _αβ from V _α and V _β using the following equations (2)-(ii), and the calculated value is the low-pass filter 16- Output to 1.

The low-pass filter 16-1 reduces the high-frequency noise component by the second voltage detection unit 12 from V _αβ input from the voltage value calculation unit 15-2, and determines the voltage value V _αβ ′ as a decision value calculation unit 16- Output to 2. Note that the time constant T4 of the low-pass filter 16-1 is set to about 1 ms in consideration of a reduction in normal malfunction and a trade-off between control speed.

Next, the determined value calculation unit 16-2 calculates the actual control angle α _{AγR_SUP} using the following equation (3), and the lower limit value calculation unit 16-3 calculates the actual control angle α _{AγR_SUP} from π. The subtracted auxiliary margin angle AγR _SUP is set as the lower limit β _min of the constant margin angle control unit 14.

However, _Xt : Commutation impedance, _Id : DC current, G: Tap ratio of converter transformer.

The output of the auxiliary constant margin angle control unit 16 is set as an output limiter of the margin angle control unit 14, that is, the lower limit value β _min . Further, the margin angle setting value γ _ref2 of the auxiliary constant margin angle control unit 16 is set lower than the margin angle setting value γ _ref1 of the constant margin angle control unit 14. The auxiliary margin angle setting value γ _ref2 of the auxiliary constant margin angle control unit 16 is set 1 to 2 ° lower than the margin angle setting value γ _ref1 of the constant margin angle control unit 14, so that the constant margin angle control unit 14 in a normal state is set. Noise can be reduced from the output of, and stability during steady state can be improved.

[2. Action]
The operation of the present embodiment as described above will be described. The power converter control devices 7-1 and 7-2 according to the present embodiment allow power to be exchanged between the two power systems 1-1 and 1-2 connected via the DC power transmission line 5. The two power converters 3-1 and 3-2 disposed at both ends of the DC transmission line 5 are respectively controlled.

The power converter control device 7 determines the margin angle γ of the power converter 3 based on the first voltage detection unit 11 that detects the voltage of the AC power system and the voltage detected by the first voltage detection unit 11. A constant margin angle control unit 14 that outputs a control angle α that is controlled to be constant, a second voltage detection unit 12 that detects the voltage of the AC power system faster than the first voltage detection unit 11, and a second The constant margin angle auxiliary value AγR _SUP is calculated based on the voltage detected by the voltage detection unit 12, and this constant margin angle auxiliary value AγR _SUP is output as the limit value β _min of the control angle α _AγR of the constant margin angle control unit 14. And an auxiliary constant margin angle control unit 16 for performing the above.

The second voltage detector 12 detects the voltage of each phase of the three-phase AC flowing through the AC power system 1 on the input side. The auxiliary constant margin angle controller 16 is the second voltage detector 12. based on the detected phase voltages to calculate the constant margin angle auxiliary value AγR _SUP.

Therefore, the second voltage detection unit 12 quickly detects a voltage due to an accident or the like, and the auxiliary constant margin angle control unit 16 sets the output limit value of the constant margin angle control unit 14 based on the detected voltage. In the event of an accident, a limit value corresponding to that is set, and commutation failure can be prevented. By providing the auxiliary constant margin angle control unit 16 and the second voltage detecting unit 12, the second voltage detector 12 is a three-phase voltage V _A at high _speed, V _B, and detects the V _C, the auxiliary constant margin angle control The unit 16 sets the set value β _min for determining the output value α _AγR of the constant margin angle control unit 14 based on the voltage detected at high speed, the direct current, and the set value of the margin angle according to an accident or the like. Therefore, the constant margin angle control unit 14 calculates an appropriate control angle _αAγR , so that the margin angle γ can be secured more quickly and a commutation failure can be prevented more reliably. Moreover, by using the 2nd voltage detection part 12, the conversion of alternating voltage can be detected rapidly and the auxiliary | assistant constant margin angle control part 16 operate | moves rapidly at the time of an accident. Furthermore, since the constant margin angle control 14 uses the first voltage detection unit 11 which is low speed but highly accurate, it is possible to ensure stability during normal operation. In short, high-precision detection and high-speed detection can be used separately to achieve both normal operation stability and quick response in the event of an accident.

The auxiliary constant margin angle control unit 16 converts a voltage of each phase detected by the second voltage detection unit 12 from a three-dimensional coordinate system to a two-dimensional coordinate system, and a coordinate conversion unit 15-1. and a voltage value calculating unit 15-2 calculates a voltage for calculating the constant margin angle auxiliary value Eiganmaaru _SUP from a two-dimensional voltage value obtained by. The constant margin angle auxiliary value AγR _SUP can be calculated quickly and easily from the three-phase detection voltage, and the limit value is set in advance for the margin angle calculated based on the low-speed first voltage detector 11. It becomes possible to give.

The control device 3 of the power converter includes a margin angle calculation unit 13 that calculates the margin angle γ _meas1 based on the voltage V _ac detected by the first voltage detection unit 11 and the current I _d flowing through the DC power transmission line 5. . The constant margin angle control unit 14 determines the control angle α _AγR based on the margin angle γ _meas1 calculated by the margin angle calculation unit 13 and the margin angle setting value γ _ref1 preset in the constant margin angle control unit 14. To do. Therefore, since the margin angle γ follows the margin angle set value γ _ref1 by performing feedback control based on the margin angle γ _meas1 which is the current value of the margin angle γ, the margin angle γ can be made substantially constant.

Auxiliary constant margin angle control unit 16, a voltage V _.alpha..beta for outputting the voltage value calculating unit 15-2, a DC transmission line 5 and the current I _d flowing through the pre auxiliary constant margin angle auxiliary margin angle which is set in the control unit 16 Based on the set value γ _ref2 , the fixed margin angle auxiliary value AγR _SUP is determined. Therefore, by setting the auxiliary margin angle setting value γ _ref2 in the auxiliary constant margin angle control unit 16, a constant margin angle auxiliary value AγR _SUP that follows the set value can be output, and the margin angle setting value γ _ref1 and the auxiliary margin setting value γ _ref1 can be output. By optimizing the relationship with the margin angle set value γ _ref2 , commutation failure can be more effectively prevented.

The auxiliary margin angle setting value γ _ref2 set in the auxiliary constant margin angle control unit 16 is set lower than the margin angle setting value γ _ref1 set in the constant margin angle control unit 14. Therefore, basically, the margin angle set value γ _ref1 is larger than the lower limit value β _min . More specifically, if the margin angle set value γ _ref1 is set to a value larger than the lower limit value β _min and smaller than the upper limit value β _max , the target value is between the lower limit value and the upper limit value, which is preferable in terms of control. It can be a numerical relationship. Briefly, by setting the margin angle setting value γ _ref2 of the auxiliary constant margin angle control unit 16 to be 1 to 2 ° lower than the margin angle setting value γ _ref1 of the constant margin angle control unit 14, the constant margin is set during normal operation. The output α _AγR of the angle control unit 14 is not limited to the output of the auxiliary constant margin angle control unit 16 and can be output as it is.

[3. effect]
The auxiliary constant margin angle control unit 16 includes a low-pass filter 16-1 that removes noise from the voltage detected by the second voltage detection unit 12. Accordingly, the auxiliary constant margin angle control unit 16 can assist the constant margin angle control unit 14 without being affected by noise, so that the control is not affected by small fluctuations other than during an accident. be able to.

Next, the effect is demonstrated based on this embodiment. FIG. 4 is a graph for explaining an effect when the auxiliary constant margin angle control unit 16 of the present embodiment is applied. The effect when a three-phase ground fault occurs will be verified when the auxiliary constant margin angle control unit 16 is not installed and when the auxiliary constant margin angle control unit 16 is installed. As shown in FIG. 4A, it is predicted that a three-phase ground fault will occur in the AC system on the reverse converter side in 0.01 second, and the AC voltage on the reverse converter side starts from 0.01 second. Descent into a shape. When the auxiliary constant margin angle control unit 16 is not mounted, as shown in FIG. 4A, the step-like drop of the AC voltage V _ac (Vac normal_auxiliary AγR in the figure) is large. As shown in b) to (d), detection by the power converter control device 7 is delayed and commutation failure occurs.

On the other hand, when the auxiliary constant margin angle control unit 16 is mounted, as shown in FIG. 4A, the AC voltage V _ac detected by the second voltage detection unit 12 (Vac high-speed_auxiliary AγR in the figure is present). 4), the AC voltage drop can be detected almost instantaneously, and as shown in FIG. 4B, the output α _{AγR_SUP} of the auxiliary constant margin angle control unit 16 operates to be small, and as a result, the constant margin angle control unit 14, the output α _AγR (with αAγR_auxiliary AγR) is controlled to be small, and as shown in FIGS. 4C and 4D, commutation failure can be prevented.

[Second Embodiment]
[1. Constitution]
First, the configuration of the second embodiment will be described. FIG. 5 is a configuration diagram of the converter control device of the second embodiment. FIG. 6 is a configuration diagram of an auxiliary constant current control unit according to the second embodiment. The configuration of the power converter control device 1 of the second embodiment is obtained by adding an auxiliary constant current control unit 9 upstream of the constant current control unit 8 to the configuration of the first embodiment as shown in FIG. It is. In the event of an AC fault on the reverse converter side, overcurrent is suppressed using the auxiliary constant current control unit 9 on the forward converter side, and voltage drop is performed at high speed using the auxiliary constant margin angle control unit 16 on the reverse converter side. Detect and control to increase the margin angle γ.

The constant current control unit 8 controls the output of the auxiliary constant current control unit 9, that is, the sum of the constant current auxiliary value ACR _SUP and the DC current I _d to follow the DC current set value I _dp .

  The auxiliary constant current control unit 9 includes a signal selector 9-1, a low-pass filter 9-2, an incomplete differentiation unit 9-3, a calculation unit 9-4, a filter unit 9-5, and an integrator 9-. 6.

  The signal selector 9-1 acquires the REC / INV operation signal of the power converter, and outputs “1” when the operation is REC operation, and outputs “0” when the operation is INV operation. When the power converter is on the forward converter side, the REC operation signal is input to the power converter, and when the power converter is on the reverse converter side, the INV operation signal is input to the power converter.

The low-pass filter 9-2 does not pass the high-frequency component of the DC voltage _VdREC on the forward converter side, but passes only the low-frequency component to smoothly reduce noise and output it to the incomplete differentiation unit 9-3. To do. The incomplete differentiation unit 9-3 performs incomplete differentiation on the output of the low-pass filter 9-2 and outputs the result to the calculation unit 9-4. The calculation unit 9-4 calculates the product of the incomplete differential value incompletely differentiated by the incomplete differentiation unit 9-3 and the capacitance of the DC power transmission line, and outputs the product to the filter unit 9-5. The filter unit 9-5 passes only the positive component of the product calculated by the calculation unit 9-4 and outputs it to the integrator 9-6.

The integrator 9-6 basically passes the output from the filter unit 9-5 as a signal, that is, a constant current auxiliary value ACR _SUP in the case of INV operation, and passes in the case of REC operation. I won't let you. Therefore, the auxiliary constant current control unit 9 operates in the REC operation, and does not operate in the INV operation.

[2. Action]
Next, the operation will be described. FIG. 7 is an equivalent circuit diagram of the DC power transmission system of the present embodiment. The sum of the DC current _{I dREC} transient current _{I C} and the forward converter side direct current line is a direct current _{I DINV} the inverter side. Further, the current I _C flowing in the DC line multiplying the capacitance C of the DC transmission line to the differential value of the detected DC voltage value V _dREC forward converter side. However, when the differentiator is used directly, the output ACR _{SUP of} the auxiliary constant current control unit 9 may fluctuate greatly if the DC voltage detection value V _dREC on the forward converter side slightly fluctuates.

Therefore, the DC voltage detection value V _dREC on the forward converter side is _removed from the high frequency noise component by the low pass filter 9-2, and further, the high frequency noise is obtained by using the incomplete differentiator 9-3 which is not a general differentiator. Further attenuates the component. Further, only an increase in the DC current on the inverter side is taken into consideration, and only an increase is made when there is a margin during normal operation and the threshold Th _{ACR_SUP is} exceeded. The adder 101-1 adds the output ACR _SUP of the auxiliary constant current control unit 9 and the direct current I _d, and the subtractor 101-2 subtracts the added value from I _dp to _{obtain the} subtracted value. Based on this, the constant current control unit 8 outputs the control angle α _ACR so that the sum of the constant current auxiliary value ACR _SUP and the direct current I _d follows the direct current command value I _dp and outputs the control angle of the forward converter. α is controlled.

In the present embodiment, since it is necessary to consider the quick operation at the time of an AC accident and the reduction of malfunction due to noise during normal operation, the time constant T1 of the low-pass filter 9-2 is about 1 ms, incomplete differentiation It is recommended to set the time constant T2 of the unit 9-3 to about 5 ms and the threshold Th _{ACR_SUP} to 4% to 8% of the DC current rating I _rated .

[3. effect]
Next, the effect will be described. The power converter control device 7 of the second embodiment includes an auxiliary constant current control unit 9 in addition to the configuration of the first embodiment. The power converter control device 7 outputs a control angle α _ACR for controlling the margin angle γ of the power converter 3 to be constant based on the DC current I _d from the DC power transmission line 5; An auxiliary constant current control unit 9 is provided that multiplies the incomplete differential value obtained by incomplete differentiation of the DC voltage on the forward converter side by the capacitance of the DC transmission line 5 and outputs a constant current auxiliary value. Further, the constant current control unit 8 performs control so that the sum of the constant current auxiliary value ACR _SUP and the DC current I _d that is the output of the auxiliary constant current control unit 9 follows the DC current set value I _dp .

In this way, the auxiliary constant current control unit 9 directly acquires the DC voltage V _dREC on the forward converter side according to an accident or the like, calculates the constant current auxiliary value ACR _SUP, and calculates the value as the DC current. and raised by adding to the I _d, to follow the direct current set value I _dp. Therefore, the constant current control unit 8 can output an optimum output α _ACR according to an accident or the like, and the control angle α is determined based on the outputs α _ACR , α _AγR , α _AVR , and the control angle α This suppresses the DC overcurrent. Since the margin angle γ of the reverse converter depends on the direct current, by suppressing the overcurrent, the overlap angle μ can be reliably reduced, and as a result, the margin angle γ can be secured to further prevent commutation. Can do. Further, as a basic operation, the auxiliary constant current control unit 9 operates on the forward converter side, and the auxiliary constant margin angle control unit 16 operates on the reverse converter side, whereby a synergy effect can be produced.

The auxiliary constant current control unit 9 includes an incomplete differentiation unit 9-3 that incompletely differentiates the DC voltage V _dREC on the forward converter side, an incomplete differential value that is incompletely differentiated by the incomplete differentiation unit 9-3, and a DC transmission. The calculation part 9-4 which calculates the product with the capacitance of the electric wire 5 and the filter part 9-5 which passes only the positive component of the product which the calculation part 9-4 calculated are provided. Since control is performed such that only the positive component is passed through and added to I _d to follow I _dp , it is possible to perform control excluding unnecessary negative components.

The auxiliary constant current control unit 9 includes a low-pass filter 9-2 that smoothly _outputs the DC voltage V _dREC on the forward converter side to the incomplete differentiation unit 9-3. Therefore, noise other than an accident does not affect the output of the auxiliary constant current control unit 9, so that the control of the auxiliary constant current control unit 9 can be ensured.

FIG. 8 is a graph for explaining the effect when the auxiliary constant current control unit of the present embodiment is applied. In the case of the prior art not implementing the auxiliary constant current control unit 9, the change of the DC current I _d when the AC accident in the case of mounting the auxiliary constant current control unit 9 shown.

In the case where the auxiliary constant current control unit 9 is not mounted, when an AC _fault occurs in the AC system on the reverse converter side, the DC current I _{dINV_conventional} on the reverse converter side increases rapidly. The discharge current increases. Therefore, even if the DC current I _{dINV_conventional} on the reverse converter side becomes large, the DC current I _{dREC_conventional} side on the forward converter side does not increase so much, so the forward converter side performing constant current control is effectively DC The increase in current cannot be suppressed and commutation fails.

When the auxiliary constant current control unit 9 is mounted, when an AC accident occurs, the auxiliary constant current control unit 9 calculates the current flowing through the DC circuit, and outputs the output and the constant current auxiliary value ACR _SUP as shown in FIG. put out. Since the DC current I _{dREC_ACR_SUP} on the forward converter side is controlled by the difference between I _dp and the constant current auxiliary value ACR _SUP , the overcurrent is efficiently suppressed and commutation failure can be prevented.

[Third Embodiment]
[1. Constitution]
FIG. 9 is a configuration diagram to which the commutation failure prevention unit of the third embodiment is applied. FIG. 10 is a detailed configuration diagram to which the commutation failure prevention unit of this embodiment is applied. As shown in FIG. 9, the configuration of the control device for the power converter according to the present embodiment uses an αβ voltage V _αβ upstream of the auxiliary constant margin angle control unit 16 in addition to the configuration of the first embodiment. A commutation failure prevention unit 15 that detects the target accident and prevents the commutation failure when the target accident occurs is provided. Note that the description of the same configuration as that of the first embodiment is omitted.

  The commutation failure prevention unit 15 includes a three-phase balanced accident detection unit 15-1 to 15-6, a three-phase unbalanced accident detection unit 15-7 to 15-10, a sampling extraction holding unit 15-16, and a margin angle. It has a pattern calculation unit 15-12 and set value resetting units 15-13 and 15-14.

The three-phase equilibrium accident detection units 15-1 to 15-6 convert the three-phase AC voltage detected by the AC voltage detection unit 12 into the αβ coordinate, and the three-phase AC voltage converted into the αβ coordinate is the first threshold Th _1. If the voltage drops further, it is determined that a three-phase equilibrium accident has occurred in the AC system.

  Specifically, the three-phase equilibrium accident detection units 15-1 to 15-6 include a coordinate conversion unit 15-1, a voltage value calculation unit 15-2, a low-pass filter 15-3, a subtractor 15-4, It comprises a comparator 15-5 and a signal on delay unit 15-6.

The coordinate conversion unit 15-1 converts the abc coordinate to the αβ coordinate from the three-phase voltages V _A , V _B , and V _C input from the second voltage detection unit 12 using the above equations (2) to (i). After conversion, the voltage value calculation unit 15-2 calculates V _αβ from V _α and V _{β using the} above equations (2) to (ii). This configuration is the same as in the first embodiment.

The low-pass filter 15-3 smoothly removes the high-frequency component from V _αβ and passes only the low-frequency component to smoothly pass V _αβ ′, and the subtractor 15-4 subtracts V _αβ from V _αβ ′. calculates the difference [Delta] V _{.alpha..beta,} comparator 15-5 discriminates whether or not the difference [Delta] V _.alpha..beta of .alpha..beta voltage exceeds the first threshold value Th _1, the signal on-delay unit 15-6, the difference [Delta] V _.alpha..beta first If the time exceeding the threshold Th ₁ is longer than the set time D1, it is determined that an equilibrium accident has occurred, and TRGABC is set to “1”.

Three-phase unbalanced fault detection unit 15-7～15-10 determines that the zero-phase voltage of the three-phase AC voltage three-phase unbalanced accident the AC system when increased from the second threshold value Th _2. Specifically, the three-phase unbalanced accident detection units 15-7 to 15-10 include an adder 15-7, a calculator 15-8, a comparator 15-9, and a signal on delay unit 15-10. Composed.

The adder 15-7 and the absolute value circuit 15-8 calculate the absolute value of the value obtained by adding the three-phase voltages V _A , V _B , and V _C input from the second voltage detection unit 12 as the zero-phase voltage V0. , comparator 15-9 discriminates whether or not the zero-phase voltage V0 exceeds the threshold value Th _2, the signal on-delay unit 15-10, time setting the time zero phase voltage V0 exceeds a threshold value Th ₂ D2 If it is longer, it is determined that an unbalanced accident has occurred, and TRG0 is set to “1”.

  The logic circuit 15-11 outputs a logical sum TRG of TRGABC and TRG0. Specifically, the logic circuit 15-11 sets TRG to “1” when a balanced or unbalanced accident occurs, that is, when one or both of TRGABC and TRG0 are “1”. In other cases, TRG is set to “0” and output to the sample extraction holding unit 15-16.

The sample extraction holding unit 15-16 samples and holds the margin angle γ _meas1 calculated by the margin angle calculation unit 13, and three-phase equilibrium accident detection units 15-1 to _15-6 and a three-phase unbalance accident detection unit. When any one or both of 15-7 to 15-10 detect an accident, the retained margin γ _meas1 is output as γ _init . More specifically, the sample extraction holding unit 15-16 records a value before several samplings from the calculated margin angle calculated value γ _meas1, and outputs the recorded value γ _init when TRG becomes “1”.

The margin angle pattern calculation unit 15-12 performs stepwise as shown in FIG. 11 based on the margin angle γ _init immediately before the accident sampled and held by the sample extraction holding unit 15-16 and several samplings before the accident. The changing margin angle pattern Δγp is calculated.

When the margin angle γ _init immediately before the accident is small, if an attempt is made to increase the margin angle γ in an AC accident, 1) the control angle α of the inverse converter is operated because the control angle α on the inverse converter side is advanced. The DC voltage _Vd decreases when the voltage becomes smaller. 2) When the DC voltage _Vd decreases, more current flows from the forward converter and the DC cable, so the DC current _Id increases. 3) The DC current _Id. 4), the overlap angle μ increases. 4) The increase in the overlap angle μ decreases the margin angle γ, which further reduces the margin and may cause a commutation failure.

Therefore, as shown in FIG. 11, the margin angle pattern Δγp is increased in two steps. FIG. 11 is a graph illustrating a fixed pattern of the margin angle operation amount according to the present embodiment. Immediately after the accident, the effect of the operation amount of the margin angle is large, so the first operation amount Δγ ₁ is made smaller as the margin angle γ _init immediately before the accident becomes smaller. The pattern is automatically calculated by the equation (4) according to the margin angle γ _init immediately before the accident, and the optimum operation amount Δγ ₁ corresponding to the prior margin angle can be calculated. Thereafter, Δγ ₂ is further increased at a rate of (Δγ ₂ −Δγ ₁ ) / T _γ2 . Further, the margin angle pattern Δγp is continued at least during the accident, and can be smoothly returned to zero. This can prevent commutation failure not only immediately after the accident but also during the accident or during recovery from the accident removal. In addition, the slope k1 and γ _{0 in} the following formula (4) are designed by a DC power transmission system. In the long-distance cable direct current power transmission system, 1 <k1 <2, 6 ° <γ ₀ <8 °, 10 ° <Δγ ₂ <15 °, T _γ1 : several ms, 15 ms <T _γ2 <25 ms, T _γ3 : accident A duration + margin (10 ms to 25 ms) is recommended.

Where γ _{init is the} margin angle immediately before the accident, γ _{min is the} minimum margin angle, and γ ₀ is a constant value.

The set value resetting units 15-13 and 15-14 use the value Δγ obtained by adding the calculation to the margin angle pattern Δγp calculated by the margin angle pattern calculation unit 15-12 to the margin angle setting value γ of the auxiliary constant margin angle control unit 16. _The value added to _ref2 is _reset as the margin angle setting value γ _ref3 of the auxiliary margin angle control unit 16. The value of the first stage of the margin angle pattern is calculated so as to be proportional to the margin angle immediately before the accident.

The multiplier 15-13 multiplies the margin angle pattern Δγp calculated by the margin angle pattern calculation unit 15-12, the accident detection signal TRG _FLT, and the INV / REC operation signal INV _EN to calculate Δγ, and the adder 15-14 _{Adds Δγ to} the margin angle setting value γ _ref2 , _{resets the} margin angle setting value γ _ref3 , and outputs it to the auxiliary constant margin angle control unit 16.

  The signal selector 15-15 acquires the INV / REC operation signal of the power converter, and outputs “0” when the operation is REC operation, and outputs “1” when the operation is INV operation. When the power converter is on the forward converter side, the signal “1” is input to the multiplier 15-13, and when the power converter is on the inverse converter side, the signal “0” is the multiplier 15-. 13 is input.

The maximum value hold unit 15-17 holds the set time T5 and the accident detection signal TRG. The set time T5 has a margin from the accident duration. For example, since the removal time of a three-phase ground fault or a single-phase ground fault is generally 100 ms, T5 is set to about 400 ms. The value obtained by adding the margin angle pattern Δγ to the margin angle setting value γ _ref2 is set as the margin angle setting value γ _ref3 of the auxiliary constant margin angle control unit 16, and the control angle α is controlled so as to increase the margin angle γ. To prevent.

[2. Action]
The power converter controller 7 determines whether or not a three-phase equilibrium accident has occurred based on the three-phase AC voltage detected by the second voltage detection unit. 6, a three-phase unbalanced accident detection unit 15-7 to 15-10 for determining whether or not a three-phase unbalanced accident has occurred based on the zero- phase voltage of the three-phase AC voltage, and a three-phase balanced accident detection unit The margin angle pattern Δγp that changes stepwise based on the discrimination results of the 15-1 to 15-6 and the three-phase unbalance accident detection units 15-7 to 15-10 and the margin angle calculated by the margin angle calculation unit a margin angle pattern calculating unit 15-12 of calculating, margin angle setting value of the margin angle pattern assisting a value obtained by adding the margin angle setting value gamma _ref2 auxiliary constant margin angle control unit 16 Δγp margin angle controller 16 gamma _ref3 Set value resetting units 15-13 and 15-14 to be reset as Having. In this way, when a three-phase unbalanced accident or a three-phase balanced accident occurs, the commutation failure occurs by resetting the margin angle set value γ _ref2 to the optimum margin angle set value γ _ref3 in the event of an accident. Can be prevented from occurring.

The control device 7 of the power converter samples and holds the margin angle γ _meas1 of the power converter 3, and three-phase balanced accident detection units 15-1 to _15-6 and a three-phase unbalanced accident detection unit 15-7. It has a sample extraction holding unit 15-16 for outputting based on the discrimination results of -15-10. Further, the margin angle pattern calculation unit 15-12 calculates a margin angle pattern Δγp that changes stepwise based on the margin angle γ _init sampled and held by the sample extraction holding unit 15-16. In this way, the margin angle γ _meas1 is sampled and held, and is output at the time of the accident. Therefore, the margin angle pattern before the accident can be calculated by outputting the margin angle several times before the accident. .

The three-phase equilibrium accident detection units 15-1 to 15-6 convert the three-phase AC voltage detected by the second voltage detection unit 12 into αβ coordinates, and the AC voltage converted into αβ coordinates is the first threshold Th _1. If the voltage drops further, it is determined that a three-phase equilibrium accident has occurred in the AC system. Also, three-phase unbalanced fault detection unit 15-7～15-10 determines that the zero-phase voltage of the three-phase AC voltage three-phase unbalanced accident the AC system when increased from the second threshold value Th ₂ . In this way, a three-phase balanced accident or a three-phase unbalanced accident can be detected easily.

  The value of the first stage of the margin angle pattern Δγp is calculated so as to be proportional to the margin angle immediately before the accident. In this way, the margin angle pattern can be appropriately created, and therefore control with the appropriate margin angle pattern can be started immediately after the accident.

The sample extraction holding unit 15-16 samples and holds the margin angle of the power converter 3, and three-phase equilibrium accident detection units 15-1 to 15-6 and three-phase unbalance accident detection units 15-7 to 15-15. When either or both of -10 detect an accident, they are output. In this way, since γ _meas1 several samples before the accident can be output as γ _init , it is possible to calculate an appropriate margin angle pattern Δγp, thereby performing appropriate control and ensuring prevention of commutation failure. Can be.

[3. effect]
The effect of this embodiment will be described. 12 and 13 are graphs for explaining the effect of preventing commutation failure at the time of a three-phase accident when the control device for the power converter of the present embodiment is applied. When a three-phase ground fault occurs, as shown in FIG. 13A, the αβ voltage difference ΔV _αβ exceeds the first threshold Th ₁ , TRG becomes 1, and the margin angle pattern calculation unit 15-12 Based on the immediately preceding margin angle, a margin angle pattern Δγp (γ pattern in FIG. 13_commutation failure prevention present) as shown in FIG. 13B is calculated. This margin angle pattern Δγp is added to the set value γ _ref2 of the auxiliary constant margin angle control unit 16 to control the control angle α (α_commutation failure prevention in the figure) so as to increase the margin angle γ. As a result, the control angle α (α_commutation failure prevention in the figure) proceeds faster, and commutation failure can be prevented.

  FIG. 14 and FIG. 15 are graphs for explaining the effect of preventing commutation failure during a single-phase fault when the power converter control device of this embodiment is applied. As shown in FIGS. 14 and 15, when the commutation failure prevention unit 15 is mounted, the speed of detecting the decrease in the AC voltage due to the single-phase accident is fast, the margin angle γ can be secured, and the commutation is successful. On the other hand, when the commutation failure prevention unit 15 is not mounted, the speed of detecting the decrease in the AC voltage due to the single-phase accident is slow, the margin angle γ cannot be secured, and commutation failure occurs.

As shown in FIG. 15A, immediately after the occurrence of the single-phase ground fault, the zero-phase voltage detection value V ₀ increases, exceeds the second threshold Th ₂ , and TRG becomes “1”. When “1” is set in TRG, the margin angle pattern calculation unit 15-12 calculates the margin angle pattern Δγp as shown in FIG. 15B based on the margin angle immediately before the accident. As in the case of the three-phase ground fault, this margin angle pattern Δγp is added to the set value γ _ref2 of the auxiliary constant margin angle control unit 16 to control the margin angle γ to be large, as shown in FIG. Thus, commutation failure can be reliably prevented.

[Fourth Embodiment]
[1. Constitution]
FIG. 16 is a detailed configuration diagram to which the commutation failure prevention unit of the fourth embodiment is applied. As shown in FIG. 16, the configuration of the control device for the power converter according to the fourth embodiment is different from the third embodiment in the commutation failure prevention unit. As shown in FIG. 16, the control device for the power converter according to the fourth embodiment uses the αβ voltage Vαβ upstream of the auxiliary constant margin angle control unit 16 in addition to the configuration of the first embodiment. It has a commutation failure prevention unit 15 'that detects an accident and prevents commutation failure when a target accident occurs. In addition, the description which overlaps with 3rd Embodiment and 4th Embodiment is abbreviate | omitted.

  The commutation failure prevention unit 15 ′ includes three-phase balanced accident detection units 15-1 to 15-6, three-phase unbalanced accident detection units 15-7 to 15-10, and a margin angle pattern calculation unit 15-12-1. 15-12-1 and setting value resetting units 15-13-1, 15-13-2, 15-20, and 15-14.

  The three-phase equilibrium accident detection units 15-1 to 15-6 convert the three-phase AC voltage detected by the second voltage detection unit 12 into the αβ coordinate, and the three-phase AC voltage converted into the αβ coordinate is the first threshold value. If the voltage drops further, it is determined that a three-phase equilibrium accident has occurred in the AC system. This is the same as the three-phase equilibrium accident detection unit of the third embodiment.

The sampling extraction holding unit 15-16-1 samples and holds the margin angle γ meas1 of the power converter, and corresponds to the three-phase equilibrium accident detected by the three-phase equilibrium accident detection units 15-1 to _{15-6. And} output them as a margin angle γ _init1 . More specifically, sampling holder 15-16-1 holds by sampling the margin angle gamma _Meas1 of the power converter, when "1" is set to TRGABC, margin angle the margin angle gamma _{Meas1 Output} as γ _init1 .

As shown in FIG. 11, the margin angle pattern calculation unit 15-12-1 is based on the margin angle γ _init1 just before the accident sampled and held by the sampling extraction holding unit 15-16-1 and several samplings before the accident. A margin angle pattern Δγp ₁ that changes gradually is calculated. More specifically, the margin angle pattern calculation unit 15-12-1 records a value before several samplings from the margin angle calculation value γ _meas1 and outputs the recorded value γ _init1 when TRGABC becomes “1”.

The three-phase unbalanced accident detection units 15-7 to 15-10 determine that a three-phase unbalanced accident has occurred in the AC system when the zero- phase voltage of the three-phase AC voltage increases beyond the second threshold. This is the same as the three-phase equilibrium accident detection unit of the third embodiment.

Sampling holder 15-16-2 holds by sampling the margin angle gamma _Meas1 of the power converter, the three-phase unbalanced accidents three-phase unbalanced fault detection unit 15-7～15-10 detects Correspondingly, they are output as a margin angle γ _init2 . More specifically, sampling holder 15-16-2 records the value of several sampling before the calculated value gamma _Meas1 the margin angle, and outputs the TRG0 becomes "1" as the record value gamma _INIT2.

As shown in FIG. 11, the margin angle pattern calculation unit 15-12-2 is based on the margin angle γ _init2 just before the accident sampled and held by the sample extraction and holding unit 15-16-2 and several samplings before the accident. A margin angle pattern Δγp ₂ that changes gradually is calculated. As shown in FIGS. 17A and 17B, the increase in the margin angle pattern Δγp _{2 in} the case of the three-phase unbalanced accident is set larger than the margin angle pattern Δγp _{1 in} the case of the three-phase equilibrium accident.

  The signal selector 15-15 acquires the INV / REC operation signal of the power converter, and outputs “0” when the operation is REC operation, and outputs “1” when the operation is INV operation. When the power converter is on the forward converter side, the signal “1” is input to the multiplier 15-13, and when the power converter is on the inverse converter side, the signal “0” is the multiplier 15-. 13-1 and 15-13-2.

  The logical negation circuit 15-18-1 calculates a logical negation from the output of the signal on delay unit 15-6 and outputs the logical negation to the logical product circuit 15-19-2. The logical negation circuit 15-18-2 calculates a logical negation from the output of the signal on delay unit 15-10 and outputs the logical negation to the logical product circuit 15-19-1.

The logical product circuit 15-19-1 calculates the logical product of the output of the signal on delay unit 15-6 and the output of the logical negation circuit 15-18-2 and outputs the logical product to the maximum value holding unit 15-17-1. . More specifically, the AND circuit 15-19-1 outputs “1” from the three-phase balanced fault detectors 15-1 to 15-6 when a balanced fault occurs and no unbalanced fault occurs. When “0” is output from the three-phase unbalanced accident detection units 15-7 to 15-10, “1” is set to TRG ₁ and output to the maximum value holding unit 15-17-1. In other cases, TRG ₁ is set to “0” and output.

The logical product circuit 15-19-2 calculates the logical product of the output of the signal on delay unit 15-10 and the output of the logical negation circuit 15-18-1, and outputs the logical product to the maximum value holding unit 15-17-2. . More specifically, the AND circuit 15-19-1 receives “1” from the three-phase unbalanced accident detection units 15-7 to 15-10 when an unbalanced accident occurs and no balanced accident occurs. When “0” is output from the three-phase equilibrium accident detection units 15-1 to 15-6, “1” is set to TRG ₂ and output to the maximum value holding unit 15-17-1. In other cases, TRG ₂ is set to “0” and output.

  The balanced accident detection flag TRG1 and the unbalanced accident detection flag TRG2 are calculated by the following equation (5).

The maximum value hold unit 15-17-1 holds the accident detection signal TRG ₁ during the set time T5 and outputs it to the multiplier 15-13-1 to TRG _FLT1 . The set time T5 has a margin from the accident duration.

Maximum value hold section 15-17-2, during the set time T5, holds the fault detection signal TRG _2, and outputs to the multiplier 15-13-2 to _{TRG FLT2.} The set time T5 has a margin from the accident duration.

The set value resetting units 15-13-1, 15-13-2, 15-20, and 15-14 are margin angle patterns Δγp ₁₁ calculated by the margin angle pattern calculating units 15-12-1 and 15-12-2. , Δγp ₂₂ , a value obtained by adding a larger value to the margin angle setting value γ _ref2 of the auxiliary constant margin angle control unit 16 is _reset as the margin angle setting value γ _ref3 of the auxiliary margin angle control unit 16.

More specifically, the multiplier 15-13-1 multiplies the margin angle pattern Δγp ₁ calculated by the balanced accident response margin angle pattern calculation unit 15-12-1, the accident detection signal TRG _FLT1, and the INV / REC operation signal INV _EN . Δγp ₁₁ is calculated, and the multiplier 15-13-2 calculates the margin angle pattern Δγp ₂ calculated by the unbalanced accident handling margin angle pattern calculation unit 15-12-2, the accident detection signal TRG _FLT2 and the INV / REC operation. Multiply the signal INV _EN to calculate Δγp ₂₂ .

Then, the maximum value selection unit 15-20 selects the maximum value from Δγp ₁₁ and Δγp ₂₂ , and outputs the maximum value as Δγ to the adder 15-14. The adder 15-14 adds Δγ to the margin angle set value γ _ref2 . _{Is added} as the margin angle setting value γ _ref3 of the auxiliary constant margin angle control unit 16 and output to the auxiliary constant margin angle control unit 16.

Specifically, a three-phase balanced accident is detected by αβ conversion, and a three-phase unbalanced accident is detected by zero-phase voltage. The sampling extraction holding units 15-16-1 and 15-16-2 respectively record values before sampling several _times from the calculated value γ _meas1 of the margin angle, and based on the detected signals TRGABC and TRG0, the margin angle immediately before the accident γ _init1 and γ _init2 are acquired. Corresponding to the three-phase equilibrium accident and the unbalance, the balance accident response margin angle pattern calculation unit 15-12-1 and the unbalance accident correspondence margin angle pattern calculation unit 15-12-2 respectively have a margin angle pattern Δγp ₁ , Δγp ₂ is calculated. Using the logic circuits 15-18-1, 15-18-2, 15-19-1, and 15-19-2, the margin angle pattern Δγ to be added to the margin angle setting value γ _ref2 is selected according to the accident type. Combine like so.

[2. Action]
The operation of this embodiment will be described. The sampling extraction holding units 15-16-1 and 15-16-2 sample and hold the margin angle γ meas1 of the power converter, and the three-phase equilibrium accident detection units 15-1 to _15-6 and the three-phase _fault In response to each of the three-phase balanced accident and the three-phase unbalanced accident detected by the balanced accident detectors 15-7 to 15-10, they are output. In this way, even when a three-phase balanced accident and a three-phase unbalanced accident occur simultaneously, appropriate control corresponding to the accident can be performed.

The increase in the margin angle pattern Δγp _{2 in} the case of the three-phase unbalance accident is set larger than the margin angle pattern Δγp _{1 in} the case of the three-phase equilibrium accident. In this way, it is possible to cope with different accidents by increasing the margin angle set value γ _ref3 in the case of a three-phase unbalanced accident at the time of the occurrence of the accident.

The third embodiment is compared with the fourth embodiment. The commutation failure prevention unit 15 of the third embodiment calculates the margin angle pattern Δγp when one of the αβ voltage difference ΔV _αβ and the zero phase voltage V ₀ exceeds the threshold value, and the auxiliary constant margin angle control unit 16. The margin angle pattern Δγ is added to the margin angle setting value γ _ref2 . That is, regardless of the balance / unbalance of the AC system accident, if the margin angle γ _init immediately before the accident is the same, the same margin angle pattern is controlled. On the other hand, the commutation failure prevention unit 15 ′ of the fourth embodiment can process the balanced accident and the unbalanced accident separately, and can calculate an appropriate margin angle pattern corresponding to the accident type. The basic shape of the margin angle pattern is the same as in FIG. However, the parameters are adjusted according to the balance / unbalance.

The commutation failure prevention unit 15 of the third embodiment calculates the margin angle pattern Δγp when one of the αβ voltage difference ΔV _αβ and the zero phase voltage V ₀ exceeds the threshold value, and the auxiliary constant margin angle control unit 16. The margin angle pattern Δγ is added to the margin angle setting value γ _ref2 . That is, regardless of the balance / unbalance of the AC system accident, if the margin angle γ _init immediately before the accident is the same, the control is performed with the same margin angle pattern Δγ. On the other hand, the commutation failure prevention unit 15 ′ can process the balanced accident and the unbalanced accident separately to calculate an appropriate margin angle pattern Δγ corresponding to the type of the accident. The basic shape of the margin angle pattern Δγ is the same as in FIG. However, the parameters are adjusted according to the balance / unbalance.

[3. effect]
The effect of this embodiment will be described. When only one of the balanced accident and the unbalanced accident is detected, the margin angle pattern corresponding to the accident is selected by the maximum value selection unit 15-20. However, in a normal system, even if an equilibrium accident occurs, the zero phase of the voltage may increase due to voltage distortion, etc., or even if an unbalance accident occurs, the effective value of the overall voltage may decrease. There are cases where both balanced and unbalanced accidents are detected with a certain time difference.

  FIG. 17 is a graph for explaining an example of margin angle pattern calculation when an accident is detected by the commutation failure prevention unit 15 ′ of the fourth embodiment. Specifically, an example in which an equilibrium accident is detected first and an unbalance accident is detected first are shown.

As shown in FIG. 17A, when an unbalanced accident is detected after the balanced accident is detected first, TRGABC becomes “1” at the time t0 when the balanced accident occurs, and the unbalanced accident occurs. At time t1, TRG0 becomes “1”. Also, TRG ₁ becomes “1” between times t0 and t1, “1” is held in the maximum value hold unit 15-17-1, and TRG _FLT1 becomes “1” from t0. Conversely, since TRG _FLT2 remains “0” for a long time, an equilibrium accident is detected, and the margin angle pattern Δγ corresponding to the equilibrium accident is added to the margin angle setting value γ _ref2 of the auxiliary constant margin angle control unit 16 to provide a margin. It is _reset as the angle setting value γ _ref3 .

As shown in FIG. 17B, when an unbalance accident is detected after the unbalance accident is detected first, TRG0 becomes “1” at the time t0 when the unbalance accident occurs, and an equilibrium accident occurs. At time t1, TRGABC becomes “1”. Also, between times t0 and t1, TRG ₂ becomes “1”, “1” is held in the maximum value hold unit 15-17-2, and TRG _FLT2 changes from t0 to “1”. An unbalanced accident is detected, and a margin angle pattern corresponding to the unbalanced accident is added to the margin angle setting value γ _ref2 of the auxiliary constant margin angle control unit 16 to be _reset as the margin angle setting value γ _ref3 . In this way, the fourth embodiment can be expected to have the same effect as the third embodiment or more.

[Fifth Embodiment]
FIG. 18 is a configuration diagram of a control device for a power converter according to the fifth embodiment. The auxiliary constant current control unit 9, the commutation failure prevention unit 15, and the auxiliary constant margin angle control unit 16 are mounted. In the event of an AC fault on the reverse converter side, overcurrent can be suppressed using the auxiliary constant current control unit 9 on the forward converter side. On the reverse converter side, the voltage drop is detected at high speed, the commutation failure prevention unit 15 calculates the margin angle pattern Δγ corresponding to the margin angle immediately before the accident, and the margin angle set value γ of the auxiliary constant margin angle control unit 16 is calculated. _The margin angle pattern Δγ is added to _ref2 , and control is performed to increase the margin angle, so that commutation failure can be reliably prevented.

[Sixth Embodiment]
FIG. 19 is a configuration diagram of a control device for a power converter according to the sixth embodiment. In the sixth embodiment, the auxiliary constant current control unit 9, the commutation failure prevention unit 15 ', and the auxiliary constant margin angle control unit 16 described in the second and fourth embodiments are mounted. In the event of an AC fault on the reverse converter side, overcurrent can be suppressed using the auxiliary constant current control unit 9 on the forward converter side. On the reverse converter side, the voltage drop is detected at high speed, the commutation failure prevention unit 15 ′ calculates the margin angle immediately before the accident and the margin angle pattern corresponding to the accident type, and the margin angle of the auxiliary constant margin angle control unit 16 The margin angle pattern is added to the set value γ _ref2 and control is performed to increase the margin angle, so that commutation failure can be reliably prevented. The sixth embodiment can be expected to have the same effect as that of the fifth embodiment, or more than the fifth embodiment.

[Seventh Embodiment]
In the second embodiment, the power converter control devices 7-1 and 7-2 include the auxiliary constant current control unit 9 and the auxiliary constant margin angle control unit 16, and the auxiliary constant current control unit 9 is provided on the forward converter side. And the auxiliary constant margin angle control unit 16 is operated on the inverse converter side. However, in the seventh embodiment, the control devices 7-1 and 7-2 of the power converter include the auxiliary constant margin angle control unit. 16, the auxiliary constant current control unit 9 is provided, and the auxiliary constant current control unit 9 is operated on the inverse converter side. As an effect, since the auxiliary constant margin angle control unit 16 is not provided, the configuration can be simplified and the cost can be kept low.

[Other Embodiments]
Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

1-1, 1-2 ... AC system 2-1, 2-2 ... Converter transformer 3-1, 3-2 ... Power converter 4-1, 4-2 ... DC reactor 5 ... DC transmission line 6- DESCRIPTION OF SYMBOLS 1,6-2 ... Interchange alternating current bus-line 7-1, 7-2 of a converter and an alternating current system ... Control apparatus 8 of a power converter ... Constant current control part (ACR)
9 ... Auxiliary constant current control unit 10 ... Constant voltage control unit (AVR)
DESCRIPTION OF SYMBOLS 11 ... 1st voltage detection part 12 ... 2nd voltage detection part 13 ... Margin angle calculation part 14 ... Constant margin angle control part (A (gamma) R)
15, 15 '... Commutation failure (CF) prevention unit or coordinate calculation unit 16 ... Auxiliary constant margin angle control unit 17 ... Minimum value selection unit 101-1, 102-2, 15-4, 15-7, 15-14 ... adders / subtracters 9-1, 15-15 ... signal selectors 9-2, 16-1, 15-3 ... low pass filter 9-3 ... incomplete differentiation unit 9-4 ... calculation unit 9-5 ... filter unit 16- 2 ... determined value calculation unit 16-3 ... lower limit value calculation units 15-1 to 15-6 ... three-phase balanced accident detection units 15-7 to 15-10 ... three-phase unbalanced accident detection unit 15-1 ... coordinate conversion unit 15-2: Voltage value calculation units 15-5, 15-9 ... Comparators 15-6, 15-10 ... Signal on delay unit 15-8 ... Absolute value circuit 15-11 ... Logic circuits 15-12, 15-12 −1, 15-12-2... Margin angle pattern calculation unit 15-13-1, 15-13-2, 15-20, 1 -14 ... set value resetting units 15-13, 15-13-1, 15-13-2 ... multipliers 15-16, 15-16-1, 15-16-2 ... sample extraction holding unit 15-17, 15-17-1, 15-17-2 ... Maximum value hold units 15-18-1, 15-18-2 ... Logical negation circuits 15-19-1, 15-19-2 ... AND circuit 15-20 ... Maximum value selection unit α: control angle γ: margin angle μ: overlap angle β: advance angle V _d , V _dREC : DC voltage, DC voltage on the forward converter side I _d , I _dREC , I _dINV : DC current, forward conversion DC current V _ac on the converter side and the reverse converter side: three-phase voltage γ _meas1 of converter AC bus: calculated value of margin angle α _max , α _min : upper limit of control angle, lower limit limiter β _max , β _min : advance angle upper, lower limiter _{α ACR, α AVR, α AγR} : ACR, a R, the output _V dp of _{AγR, I dp:} DC voltage command value, the DC current command value _{γ ref1, γ ref2, γ ref3} : margin angle set value (the minimum margin angle)
C: DC line capacitance L: DC reactor R: DC line resistance value I _rated : DC current rating value T1, T2, T3, T4: Time constant T5: Maximum value hold time setting value (MAX_HOLD)
_{T γ1, T γ2, T γ3} : margin angle pattern time set value Δγ _1, Δγ _2: margin angle pattern angle setpoint _{Δγp 1, Δγp 2, Δγp 11} , Δγp 22, Δγ: margin angle pattern Tauganma: margin angle pattern returns Time constant γ _min : _Inverter minimum margin angle set value γ _init , γ _{init 1} , γ _{init 2} : Accident immediately before margin Th _{ACR_SUP} : Auxiliary constant current control output threshold Th ₁ , Th ₂ : αβ voltage drop threshold, zero Phase voltage threshold AγR _SUP : Constant margin angle auxiliary value ACR _SUP : Constant current auxiliary value

Claims (16)

In a control device for a power converter that is provided at an end of a DC transmission line connected to an AC power system and converts AC power into DC power,
A first voltage detector for detecting the voltage of the AC power system;
Based on the voltage detected by the first voltage detector, a constant margin angle control unit that outputs a control angle for controlling the margin angle of the power converter to be constant;
A second voltage detector that detects the voltage of the AC power system on the input side at a higher speed than the first voltage detector;
An auxiliary constant margin that calculates a constant margin angle auxiliary value based on the voltage detected by the second voltage detection unit and outputs the constant margin angle auxiliary value as a limit value of the control angle of the constant margin angle control unit. possess and the angular control unit, the,
The second voltage detector detects a voltage of each phase of a three-phase AC flowing through the AC power system on the input side;
The auxiliary constant margin angle control unit calculates the constant margin angle auxiliary value based on the voltage of each phase detected by the second voltage detection unit,
The auxiliary constant margin angle control unit converts a voltage of each phase detected by the second voltage detection unit from a three-dimensional coordinate system to a two-dimensional coordinate system, and 2 obtained by the coordinate conversion unit. A control apparatus for a power converter, comprising: a voltage value calculation unit that calculates a voltage for calculating the constant margin angle auxiliary value from a dimension voltage value . A margin angle calculation unit that calculates a margin angle based on the voltage detected by the first voltage detection unit and the current flowing through the DC transmission line;
The constant margin angle control unit determines the control angle based on a margin angle calculated by the margin angle calculation unit and a margin angle setting value set in the constant margin angle control unit in advance. The power converter control device according to claim 1 . The auxiliary constant margin angle control unit includes a voltage output from the voltage value calculation unit, a current flowing through the DC transmission line, and a constant margin angle auxiliary value set value set in advance in the auxiliary constant margin angle control unit. based on the determining the constant margin angle auxiliary value, converter control apparatus according to claim 1, wherein. The auxiliary set auxiliary margin angle set value to the constant margin angle controller, said that it is set lower than the constant margin angle set margin angle set value to the control unit, according to claim 3, wherein Control device for power converter.   The power converter control device according to claim 1, wherein the auxiliary constant margin angle control unit includes a low-pass filter that removes noise from a voltage detected by the second voltage detection unit. Based on the direct current from the direct current transmission line, a constant current control unit that outputs a control angle for controlling the current of the power converter constant,
An auxiliary constant current control unit that outputs a constant current auxiliary value by multiplying an incomplete differential value obtained by incomplete differentiation of the DC voltage on the forward converter side and the capacitance of the DC transmission line;
The said constant current control part controls so that the sum of the constant current auxiliary value which is an output of the said auxiliary | assistant constant current control part, and the said direct current may track a direct current setting value. The power converter control device according to any one of claims 5 to 6. The auxiliary constant current control unit is a product of an incomplete differential unit that incompletely differentiates the DC voltage on the forward converter side, an incomplete differential value that is incompletely differentiated by the incomplete differential unit, and a capacitance of the DC transmission line. The control device for a power converter according to claim 6 , further comprising: a calculation unit that calculates a value and a filter unit that passes only a positive component of a product calculated by the calculation unit. 8. The power converter control device according to claim 7, wherein the auxiliary constant current control unit includes a low-pass filter that smoothly outputs a DC voltage on a forward converter side to the incomplete differentiation unit. A three-phase equilibrium accident detection unit for determining whether a three-phase equilibrium accident has occurred based on the three-phase AC voltage detected by the second voltage detection unit;
A three-phase unbalanced accident detection unit that determines whether or not a three-phase unbalanced accident has occurred based on the zero- phase voltage of the three-phase AC voltage;
A margin angle pattern that calculates a margin angle pattern that changes stepwise based on the discrimination results of the three-phase equilibrium accident detection unit and the three-phase unbalance accident detection unit and the margin angle calculated by the margin angle calculation unit A calculation unit;
A setting value resetting unit that resets a value obtained by adding the margin angle pattern to a margin angle setting value of the auxiliary constant margin angle control unit as a margin angle setting value of the auxiliary constant margin angle control unit;
The control apparatus for a power converter according to claim 2 . Sampling and holding a margin angle of the power converter, having a sampling extraction holding unit that outputs based on the determination result of the three-phase equilibrium accident detection unit and the three-phase unbalance accident detection unit,
10. The power according to claim 9, wherein the margin angle pattern calculation unit calculates a margin angle pattern that changes stepwise based on the margin angle sampled and held by the sample extraction holding unit. Control device for the converter. The three-phase equilibrium accident detection unit converts the three-phase AC voltage detected by the second voltage detection unit into αβ coordinates, and when the AC voltage converted into αβ coordinates falls below the first threshold, three-phase balanced fault it is determined that has occurred, the control device for a power converter according to claim 9 or 1 0, wherein. The three-phase unbalanced fault detection unit that determines that the zero-phase voltage of the three-phase AC voltage three-phase unbalanced accident the AC system when increased from the second threshold value, the preceding claims 9, characterized in 1 converter control apparatus according to any one of 1. Power converter control apparatus according to any one of claims 9 to 1 2 the value of the first stage can be calculated as proportional to the margin angle of accident immediately before, and wherein said margin angle pattern . The sampling extraction holding unit is configured to extract and hold the power converter when one or both of the three-phase balanced accident detection unit and the three-phase unbalanced accident detection unit detect an accident. The power converter control device according to claim 10 , wherein a margin angle is output. The sample extraction holding unit is sampled and held corresponding to each of the three-phase equilibrium accident and the three-phase unbalance accident detected by the three-phase equilibrium accident detection unit and the three-phase unbalance accident detection unit. The power converter control device according to claim 10 , wherein a margin angle of the power converter is output. Three-phase the margin angle setting greater the increase in margin angle pattern for three-phase unbalanced fault than the pattern, the control device for a power converter according to claim 1 5, wherein in the case of equilibrium accident.