JP5028940B2 - Output voltage control apparatus and method for serial multiple AC / DC converter - Google Patents

Description

  The present invention relates to an output voltage control apparatus and method for a serial multiplex type AC / DC converter comprising a plurality of AC / DC converters connected in series to three phases.

  In general, an output control device of an AC / DC converter uses pulse width modulation control by a carrier wave comparison method, and controls an AC output voltage. The carrier wave comparison method is a method in which an AC voltage waveform based on an output voltage command value is compared with a carrier wave (carrier) that determines a switching frequency, and an on / off pulse signal is generated based on the magnitude of the AC voltage waveform and the value of the carrier wave.

  For example, to reduce the output voltage of the AC / DC converter, the amplitude (modulation factor) of the AC voltage waveform is lowered from 1. However, when the modulation factor is lowered, the voltage harmonics increase as shown in FIG. The voltage distortion rate tends to increase. On the other hand, waveform distortion can be reduced and control performance can be improved by increasing the carrier frequency. However, since the loss increases as the carrier frequency increases, especially in the case of a large capacity AC / DC converter, In practice, the carrier frequency is set low.

  In the case of a large-capacity AC / DC converter, since it is difficult to design a large converter capacity per converter, a converter multiplexing system is used. For example, a serial multiplex AC / DC converter is configured by connecting a plurality of converters in series for each phase of three phases. In this multiplex type serial multiplex type AC / DC converter, when the output voltage is lowered, each converter synthesizes and outputs voltage vectors having the same phase and the same modulation rate. For example, when multiplexing is performed by two converters, conventionally, in order to set the modulation rate to 0.8, the modulation rate is set to 0.8 for both of the two converters in the same phase.

  FIG. 11 is an output voltage vector diagram when the output voltage of the serial multiplex AC / DC converter multiplexed by two converters is reduced from 1 pu to 0.8 pu. 11A is an output voltage vector diagram before reducing the output voltage of the serial multiple AC / DC converter, and FIG. 11B is an output voltage vector diagram after reducing the output voltage of the serial multiple AC / DC converter. It is.

  As shown in FIG. 11 (a), the three-phase in-phase converter of the serial multiplexing type conversion device is a voltage vector having the same phase and the same modulation rate, and each of the three phases has a phase difference of 120 ° and has three phases. Equilibrium. For example, in the U phase, the output voltages U1 and U2 of the two converters have the same phase and the same voltage value (same modulation rate). Also for the V phase, the output voltages V1 and V2 of the two converters have the same phase and the same voltage value (the same modulation factor), and for the W phase, the output voltages W1 and W2 of the two converters have the same phase and the same value. It is a voltage value (same modulation rate). Since each of the three phases has a phase difference of 120 ° and is balanced in three phases, the voltage values of U1 to W2 are all equal.

  In this state, when the output voltage is reduced to 0.8 pu, the modulation rate of the two converters for each of the three phases is set to 0.8. As a result, as shown in FIG. 11, the output voltages u1 to w2 of the two converters in each phase of the three phases are similar to the voltage vector of FIG. 11 (a) reduced to 0.8 pu. Become.

Here, in a serial multiplex AC / DC converter, there is a power converter that obtains a switching angle in advance in order to reduce a specific harmonic order, and operates at the switching angle (see, for example, Patent Document 1). .
JP-A-6-276747

  However, in Patent Document 1, the switching angle at which each harmonic content is minimized is obtained. However, the control is performed when the output voltage is constant, and the output voltage is variable. It cannot be applied as it is. That is, for example, in the case of multiplexing with two converters, in order to set the output voltage to 0.8 pu, the modulation rate is set to 0.8 for both converters in the same phase. Since the output waveform distortion changes due to the change of, each harmonic content also changes.

  Therefore, a harmonic filter is provided to remove waveform distortion. However, when designing a harmonic filter, it is necessary to design the filter so as to suppress the maximum value of waveform distortion to a certain limit value. Therefore, the harmonic filter cannot be made compact.

  An object of the present invention is to provide an output voltage control device and method for a serial multiple AC / DC converter that can suppress harmonics accompanying changes in the output voltage while suppressing conversion loss in the converter.

An output voltage control device for a serial multiplex AC / DC converter according to claim 1 is a serial multiplex AC / DC converter configured by connecting a plurality of converters for converting power to each of three phases in series. The voltage command value input means for inputting the voltage command value of the serial multiple AC / DC converter, and the voltage increase or decrease of the serial multiple AC / DC converter input by the voltage command value input means, Based on the voltage command value of the phase change, the voltage value and phase of the output voltage of at least one converter among the converters of each phase are fixed, and the voltage value and phase of the output voltage of any remaining converter in a state of changing the output voltage command value of the voltage command value becomes equal such each phase of each transducer of the vector sum of the phases of each of the converter output voltage is the multi-series type AC-DC converter Converter Pressure command value output means, and converter control means for controlling the output voltage of each converter of each phase based on the voltage command value of the converter from the converter voltage command value output means. And

The output voltage control device of the serial multiplex type AC / DC converter according to the invention of claim 2 is the invention according to claim 1 , wherein the converter control means compares the AC voltage waveform based on the voltage command value with the carrier wave and compares them. A carrier wave comparison control system that controls each converter of each phase according to the magnitude of the value is adopted, and the frequency of the carrier wave is changed with respect to the converter in which the voltage command value is changed.

An output voltage control method for a serial multiplex AC / DC converter according to the invention of claim 3 is a serial multiplex AC / DC converter configured by connecting a plurality of converters for converting power to each of three phases in series. In the output voltage control method, the voltage command value of the serial multiple AC / DC converter is input, and each phase is determined based on the voltage increase / decrease and phase change voltage command values of the input serial multiple AC / DC converter. Conversion of each phase in a state where the voltage value and phase of the output voltage of at least one of the converters is constant and the voltage value and phase of the output voltage of any of the remaining converters are changed. The voltage command value of each converter of each phase is set so that the vector sum of the output voltage of the converter becomes equal to the voltage command value of the serial multiple AC / DC converter, and based on the output voltage command value of the converter For each phase And controlling the output voltage of the vessel.

  According to the present invention, the voltage command value of each converter of each phase is output so that the vector sum of the output voltage of each converter of each phase becomes equal to the voltage command value of the serial multiple AC / DC converter. The voltage command value of each converter of each phase can be output without changing the modulation rate even with respect to the voltage command value for raising or lowering the voltage of the serial multiple AC / DC converter. Therefore, an increase in voltage harmonics accompanying a decrease in the modulation factor can be prevented, and an increase in the voltage distortion rate can be prevented. Further, the capacity of the harmonic filter can be reduced, and the harmonic filter can be made compact and the filter loss can be reduced. Moreover, the harmonic loss which generate | occur | produces with a transformer can be reduced by reduction of a generated harmonic.

  FIG. 1 is a configuration diagram of an output voltage control device of a serial multiple AC / DC converter according to an embodiment of the present invention. The serial multiple conversion device 11 is provided with a plurality of converters 12 for each of the three phases. FIG. 1 shows a case where n converters 12 are provided for the U phase, V phase, and W phase of each of the three phases. That is, converters 12U1 and 12U2 to 12Un are provided in the U phase, converters 12V1 and 12V2 to 12Vn are provided in the V phase, and converters 12W1 and 12W2 to 12Wn are provided in the W phase.

  FIG. 2 is a circuit configuration diagram illustrating an example of the converter 12. The converter 12 is configured by connecting, for example, four IGBTs (Insulated Gate Bipolar Transistors) 13 which are, for example, insulated gate semiconductor elements in series and parallel, and converts DC power from the DC power supply 14 into AC power to be wound. 15 is output.

  As shown in FIG. 1, the winding 15 of the converter 12 is magnetically coupled to the primary winding of the transformer 16, and n pieces are arranged in series in each of the three phases. Thereby, the output voltage of n converters 12 connected in series is output from each primary winding of transformer 16 for each phase.

  The converter control device 17 controls each of the converters 12U1 to 12Wn, and the voltage command value Vr of the serial multiple AC / DC converter is input to the voltage command value input means 18. The converter voltage command value output means 19 is based on the voltage command value Vr of the serial multiplex type AC / DC converter input by the voltage command value input means 18, and each converter 12U1 of each phase stored in the storage unit 20 in advance. Voltage command values Vru1 to Vrwn of ˜12 Wn are taken out and output to the converter control means 21.

  The converter control means 21 compares the AC voltage waveform based on the voltage command value with the carrier wave, and controls the converter of each phase according to the magnitude of those values. Output control commands. That is, the converter control means 21 gates so that the output voltage of each converter 12U1 to 12Wn of each phase becomes the voltage command values Vru1 to Vrwn of the converters 12U1 to 12Wn from the converter voltage command value output means 19. A control command is output to the control circuit 22, and the gate control circuit 22 outputs a gate signal to each converter 12U1 to 12Wn of each phase.

  Here, the storage unit 20 converts each phase of each of the three phases so that the vector sum of the output voltages of the respective converters 12U1 to 12Wn of each phase becomes equal to the voltage command value Vr of the serial multiple AC / DC converter. Voltage command values Vru1 to Vrwn of the units 12U1 to 12Wn are stored in advance.

  FIG. 3 is an explanatory diagram of Example 1 of the voltage command value of each converter 12 of each phase stored in advance in the storage unit 20. FIG. 3 shows voltage vectors when two converters 12 for each phase are provided, and FIG. 3A shows the output voltage before the output voltage of the serial multiple AC / DC converter 11 is lowered. FIG. 3B is a vector diagram and FIG. 3B is an output voltage vector diagram after the output voltage of the serial multiple AC / DC converter 11 is lowered.

  That is, in the first embodiment, when the voltage command value Vr for voltage reduction of the serial multiple AC / DC converter 11 is input, the voltage values | U1 | of the output voltages U1 to W2 of the converters 12U1 to 12W2 of each phase ˜ | W2 | (voltage value of the output voltage when the modulation factor m is 1) is kept constant, and the phase of the output voltages U1 to W2 is changed.

  As shown in FIG. 3 (a), the output voltage before reducing the output voltage of the serial multiple AC / DC converter 11 is the same voltage value for the output voltages U1 and U2 of the two converters in the U phase. (Voltage value of the output voltage when the modulation factor m is 1) For the V phase, the output voltages V1 and V2 of the two converters have the same phase and the same voltage value (output when the modulation factor m is 1). Similarly, for the W phase, the output voltages W1 and W2 of the two converters are the same voltage value (the voltage value of the output voltage when the modulation factor m is 1). Since each of the three phases has a phase difference of 120 ° and is balanced in three phases, the voltage values of U1 to W2 are all equal. That is, | U1 | = | U2 | = | V1 | = | V2 | = | W1 | = | W2 |.

  Now, when the voltage command value Vr of the serial multiple AC / DC converter 11 is a voltage reduction command (modulation factor m is m = √3 / 2) that is √3 / 2 times, FIG. As shown, the voltage values | U1 | to | W2 | of the output voltages U1 to W2 of the converters 12U1 to 12W2 of the respective phases are kept constant, and the phases of the output voltages U1, V1, and W1 are set to π / 6. The phase of the output voltages U2, V2, and W2 is delayed by π / 6. As a result, for the U phase, the V phase, and the W phase, an output voltage whose magnitude is √3 / 2 times and whose phase remains unchanged by 120 ° can be obtained.

  Here, the loss of the converter 12 will be considered. The loss of the converter 12 (conduction loss / loss of the freewheeling diode) is represented by the product of the modulation factor m and the power factor cosΦ. In the case of the conventional system shown in FIG. 11, the phase of each of the three phases is the same, and the voltage values | U1 | to | W2 | of U1 to W2 are multiplied by √3 / 2, so the modulation factor m is m = √. Since 3/2 and Φ = 0, the power factor cosΦ is cos0 = 1. Therefore, in the case of the conventional method, the loss of the converter 12 (conduction loss / loss of the freewheeling diode) can be expressed by the product of mcosΦ = (√3 / 2) · 1. On the other hand, in Example 1, since the voltage values | U1 | to | W2 | of the output voltages U1 to W2 are kept constant, the modulation factor m is m = 1 and Φ = π / 6, so the power factor cosΦ is cosπ / 6 = √3 / 2. Therefore, in the first embodiment, the loss of the converter 12 (conduction loss / loss of the freewheeling diode) can be expressed by the product of mcosΦ = 1 · (√3 / 2), and the loss of conduction loss and the freewheeling diode are the same. is there. If the carrier frequency is the same, the number of times of switching is the same and the turn-on and turn-off losses are also the same. As a result, the loss is almost the same in both the conventional method and the first embodiment.

  FIG. 4 is an explanatory diagram of Example 2 of the voltage command value of each converter 12 of each phase stored in advance in the storage unit 20. 4 shows voltage vectors when two converters 12 are provided for each phase, and FIG. 4A shows the output voltage before the output voltage of the serial multiple AC / DC converter 11 is lowered. 4B is an output voltage vector diagram after the output voltage of the serial multiple AC / DC converter 11 is lowered.

  In the second embodiment, when the voltage command value Vr for reducing the voltage of the serial multiple AC / DC converter 11 is inputted, the voltage command value Vr of the serial multiple AC / DC converter 11 becomes the output voltage | U1 of one converter 12. | ~ | W2 | (the output voltage when the modulation factor m is 1) is greater than the voltage value and phase of the output voltage of one converter 12 of the converters 12U1 to 12W2 of each phase. The voltage value of the output voltage of the remaining at least one converter 12 is changed (the modulation factor m is less than 1).

  As shown in FIG. 4A, the output voltage before reducing the output voltage of the serial multiple AC / DC converter 11 is similar to FIG. 3A, and each of the three phases has a phase difference of 120 °. The voltage values of U1 to W2 are all equal, and | U1 | = | U2 | = | V1 | = | V2 | = | W1 | = | W2 |.

  Now, it is assumed that a voltage lowering command in which the voltage command value Vr of the serial multiple AC / DC converter 11 is 0.6 times is given. In this case, as shown in FIG. 4B, the voltage values | U1 |, | V1 |, | W1 | of the output voltages U1, V1, W1 of the converters 12U1, 12V1, 12W1 of the respective phases The phase is kept constant, and the voltage values | u2 |, | v2 |, and | w2 | are each 0 while the phases of the output voltages u2, v2, and w2 of the converters 12U2, 12V2, and 12W2 of the remaining phases remain unchanged. Change to 2 pu. As a result, for the U phase, the V phase, and the W phase, an output voltage that is 0.6 times larger and remains unchanged from the original phase by 120 ° is obtained. In this case, the loss of the converter 12 is substantially the same as in the conventional method.

  FIG. 5 is an explanatory diagram of Example 3 of the voltage command value of each converter 12 of each phase stored in advance in the storage unit 20. FIG. 5 shows voltage vectors when two converters 12 for each phase are provided. FIG. 5A shows the output voltage before the output voltage of the serial multiple AC / DC converter 11 is lowered. FIG. 5B is a vector diagram after the output voltage of the serial multiple AC / DC converter 11 is lowered.

  In the third embodiment, when the voltage command value Vr for voltage reduction and phase change of the serial multiple AC / DC converter 11 is input, the output of at least one converter 12 among the converters 12U1 to 12W2 of each phase. The voltage value and phase of the voltage are made constant, and the voltage value and phase of the output voltage of any remaining converter 12 are changed.

  As shown in FIG. 5 (a), the output voltage before reducing the output voltage of the serial multiple AC / DC converter 11 has a phase difference of 120 ° in each of the three phases, as in FIG. 3 (a). The voltage values of U1 to W2 are all equal, and | U1 | = | U2 | = | V1 | = | V2 | = | W1 | = | W2 |.

  Now, it is assumed that the voltage command value Vr of the serial multiple AC / DC converter 11 is 1 / √3 times the previous voltage command and a phase voltage command of π / 6 is given. In this case, as shown in FIG. 5B, the voltage values | U1 |, | V1 |, | W1 | of the output voltages U1, V1, W1 of the converters 12U1, 12V1, 12W1 of the respective phases The phase is kept constant, the phases of the output voltages u2, v2, and w2 of the converters 12U2, 12V2, and 12W2 of the remaining phases are advanced by π / 2, and the voltage values | u2 |, | v2 |, | Each w2 | is changed to 1 / √3. As a result, for U phase, V phase, and W phase, an output voltage whose magnitude is 1 / √3 times the previous phase and the phase is advanced by π / 6 and is changed by 120 ° as it is is obtained. In this case, the loss of the converter 12 is substantially the same as in the conventional method.

  In the voltage vector of FIG. 5A, it is also possible to change only the phase while keeping the voltage magnitude constant. When changing the phase of the converter by α degrees, in the conventional method, the phase of each voltage vector is α degrees under the condition of | U1 | = | U2 | = | V1 | = | V2 | = | W1 | = | W2 | In the present invention, the voltage vectors U1, V1, and W1 are kept constant, and the phases and magnitudes of U2, V2, and W2 are changed, so that the phase control of α degrees is performed as in the prior art. It is also possible to perform. FIG. 6 is an explanatory diagram of Example 4 of the voltage command value of each converter 12 of each phase stored in advance in the storage unit 20. FIG. 6 shows a voltage vector when two converters 12 are provided for each phase, and FIG. 6A shows the output voltage before the output voltage of the serial multiple AC / DC converter 11 is lowered. 6B is an output voltage vector diagram after the output voltage of the serial multiple AC / DC converter 11 is lowered.

  In the fourth embodiment, when the control command is output to the gate control circuit 22 by the carrier wave comparison control method, the voltage command value Vr for voltage reduction of the serial multiple AC / DC converter 11 is compared with the first embodiment shown in FIG. Is input, the voltage value (output voltage when the modulation factor m is 1) and the phase of the output voltage of one of the converters 12U1 to 12W2 in each phase are constant, and the rest The voltage value of the output voltage of at least one converter 12 is changed (modulation rate m is set to less than 1), and the carrier of the carrier wave comparison control system is applied to the converter whose voltage value and phase are changed. The frequency (carrier frequency) is increased.

  As shown in FIG. 6 (a), the output voltage before reducing the output voltage of the serial multiple AC / DC converter 11 has a phase difference of 120 ° in each of the three phases, as in FIG. 3 (a). The voltage values of U1 to W2 are all equal, and | U1 | = | U2 | = | V1 | = | V2 | = | W1 | = | W2 |.

  If the voltage command value Vr of the serial multiplex AC / DC converter 11 is a voltage lowering command (modulation factor m is m = √3 / 2) which is 1 / √3 times the previous value, FIG. ), The voltage values | U1 |, | V1 |, | W1 | of the output voltages U1, V1, W1 of the converters 12U1, 12V1, 12W1 of the respective phases are kept constant, and the phase is π Advance by / 6. Then, the phases of the output voltages u2, v2, and w2 of the converters 12U2, 12V2, and 12W2 of the remaining phases are delayed by π / 3, and the voltage values | u2 |, | v2 |, and | w2 | Change to √3. In addition, the carrier frequencies of the output voltages u2, v2, and w2 of the converters 12U2, 12V2, and 12W2 of the remaining phases in which the voltage values | u2 |, | v2 |, and | w2 | are changed to 1 / √3 respectively. Increase carrier frequency Fc.

  As a result, for U phase, V phase, and W phase, an output voltage whose magnitude is √3 / 2 times and the phase remains unchanged by 120 ° is obtained, and the remaining voltage values are changed. Since the carrier voltages (carrier frequencies) Fc of the output voltages u2, v2, and w2 of the converters 12U2, 12V2, and 12W2 of the respective phases are increased, an output voltage with reduced waveform distortion can be obtained. When the modulation factor changes, the generated harmonic voltage distortion also increases or decreases.

By changing the carrier frequency according to the modulation rate, fluctuations in the generated harmonics can be suppressed. Regarding the loss of the converter 12 in this case, the loss increases because the carrier frequency is increased. However, increasing the carrier frequency increases the output voltage u2 of the converters 12U2, 12V2, and 12W2 of the remaining phases whose voltage values are reduced. Since it is only about v2 and w2, the influence is few and it becomes a loss substantially the same as the conventional system. In the above description, the carrier frequency of the carrier wave comparison control method is increased with respect to the first embodiment. However, the present invention can be similarly applied to the second and third embodiments.

  FIG. 7 is an explanatory diagram of Example 5 of the voltage command value of each converter 12 of each phase stored in advance in the storage unit 20. FIG. 7 shows voltage vectors when three converters 12 for each phase are provided. FIG. 7A shows the output voltage before the output voltage of the serial multiple AC / DC converter 11 is lowered. FIG. 7B is a vector diagram and FIG. 7B is an output voltage vector diagram after the output voltage of the serial multiple AC / DC converter 11 is lowered.

  The fifth embodiment is different from the first embodiment shown in FIG. 3 in that the voltage command value Vr of the serial multiple AC / DC converter 11 when the voltage command value Vr for voltage reduction of the serial multiple AC / DC converter 11 is input. Of the plurality of converters 12 connected in series, and the remaining converters other than the number necessary for sharing the voltage command value Vr of the serial multiple AC / DC converter 12 12 is stopped or the output voltage is set to 0, and the output voltages of the converters 12 corresponding to the number of converters necessary to share the voltage command value Vr of the serial multiple AC / DC converter 11 are adjusted.

  As shown in FIG. 7 (a), the output voltage before reducing the output voltage of the serial multiple AC / DC converter 11 is the same in the U phase for the output voltages U1, U2, and U3 of the three converters in the same phase. Similarly, with respect to the voltage value (voltage value of the output voltage when the modulation factor m is 1) and the V phase, the output voltages V1, V2, and V3 of the three converters have the same phase and the same voltage value (the modulation factor m is 1). Similarly, for the W phase, the output voltages W1, W2, and W3 of the three converters are the same voltage value in the same phase (the voltage value of the output voltage when the modulation factor m is 1). ). Since each of the three phases has a phase difference of 120 ° and is balanced in three phases, the voltage values of U1 to W3 are all equal. That is, | U1 | = | U2 | = | U3 | = | V1 | = | V2 | = | V3 | = | W1 | = | W2 | = | W3 |.

  Now, it is assumed that a voltage lowering command in which the voltage command value Vr of the serial multiple AC / DC converter 11 is 2/3 times is given. In this case, as shown in FIG. 7B, the voltage values | U1 |, | U2 | and the phase of the output voltages U1, U2 of the converters 12U1, 12U2 of each phase are kept constant, The remaining converters 12U3, 12V3, 12W3 of each phase are stopped or the output voltage is set to zero. As a result, an output voltage that is 2/3 times larger and has the original phase changed by 120 ° is obtained for the U phase, the V phase, and the W phase.

  When the voltage command value Vr of the serial multiple AC / DC converter 11 is a voltage reduction command that is not an integral multiple of the output voltage of one converter 12, for example, a voltage that is smaller than 2/3 times and larger than 1/3 times When a lowering command (for example, a voltage lowering command of √3 / 3 times) is given, one converter 12U3, 12V3, 12W3 of each phase is stopped or the output voltage is set to 0, and the remaining each phase The voltage values | U1 | and | U2 | are set to √3 / 2 times (modulation factor m is m = √3 / 2) while keeping the phases of the output voltages U1 and U2 of the converters 12U1 and 12U2 as they are. As a result, for the U phase, the V phase, and the W phase, an output voltage whose magnitude is √3 / 3 times and whose phase is unchanged by 120 ° is obtained.

  FIG. 8 is an explanatory diagram of Example 6 of the voltage command value of each converter 12 of each phase stored in advance in the storage unit 20. FIG. 8 shows voltage vectors when three converters 12 for each phase are provided. FIG. 8A shows the output voltage before the output voltage of the serial multiple AC / DC converter 11 is lowered. FIG. 8B is a vector diagram after the output voltage of the serial multiple AC / DC converter 11 is lowered.

  In the sixth embodiment, in contrast to the fifth embodiment shown in FIG. 7, when a voltage lowering command that is not an integral multiple of the output voltage of one converter is given, the converter 12 that does not stop or set the output voltage to 0 is used. Instead of reducing the output voltage voltage value, the voltage value of the output voltage of the converter 12 that does not stop or set the output voltage to 0 (the voltage value of the output voltage when the modulation factor m is 1) remains constant. It holds and changes the phase of the output voltage.

  As shown in FIG. 8 (a), the output voltage before reducing the output voltage of the serial multiple AC / DC converter 11 has a phase difference of 120 ° in each of the three phases, as in FIG. 7 (a). The voltage values of U1 to W3 are all equal, and | U1 | = | U2 | = | U3 | = | V1 | = | V2 | = | V3 | = | W1 | = | W2 | = | W3 |.

  Now, it is assumed that a voltage lowering command (modulation factor m is m = √3 / 2) in which the voltage command value Vr of the serial multiple AC / DC converter 11 is √3 / 3 times is given. In this case, since it is a voltage reduction command that is not an integral multiple of the output voltage of one converter 12 and is a voltage command that can be borne by two converters 12 with one unit stopped or the output voltage set to 0, One converter 12U3, 12V3, 12W3 is stopped or the output voltage is set to 0. Two converters 12U1, 12U2 for the U phase, two converters 12V1, 12V2, for the V phase, two conversions for the W phase The voltage command value Vr is output by the units 12W1 and 12W2.

  As shown in FIG. 8B, the voltage values | U1 | to | W2 | of the output voltages U1 to W2 of the converters 12U1 to 12W2 of the respective phases are kept constant, and the output voltages U1, V1, W1 are kept constant. Is advanced by π / 6, and the phases of the output voltages U2, V2, W2 are delayed by π / 6. As a result, for the U phase, the V phase, and the W phase, an output voltage whose magnitude is √3 / 3 times and whose phase is unchanged by 120 ° is obtained.

  In the above description, in correspondence with the voltage command value Vr of the serial multiple AC / DC converter 11, the voltage command value of each converter 12 of each phase as shown in FIGS. Although it memorize | stores, you may make it calculate each time.

  In the embodiment of the present invention, an example in which a single-phase converter is combined is introduced, but a three-phase converter or a three-phase / single-phase converter may be combined.

  Moreover, although the converter 12 of each phase was operated with the same number, it may be operated with a different number for each phase. For example, in the serial multiplex AC / DC converter 11 having four converters 12 for each phase and a total of 12 converters 12, the U phase and the V phase are operated by two units, and the W phase May be operated with three vehicles. In this case, it goes without saying that the voltage values of the U-phase, V-phase, and W-phase output voltages of the three phases are controlled to be equal. Even when the number of operating converters 12 of each phase is not the same, the loss of the converter 12 at that time hardly changes.

  Further, when the output voltage of the converter 12 is lowered, a certain converter can be output in reverse. FIG. 9 is an explanatory diagram of Example 7 of the voltage command value of each converter 12 of each phase stored in advance in the storage unit 20. FIG. 9 shows voltage vectors when three converters 12 for each phase are provided. FIG. 9A shows the output voltage before the output voltage of the serial multiple AC / DC converter 11 is lowered. FIG. 9B is an output voltage vector diagram after the output voltage of the serial multiple AC / DC converter 11 is lowered.

  In the ninth embodiment, in contrast to the sixth embodiment shown in FIG. 8, when a voltage reduction command that is not an integral multiple of the output voltage of one converter is given, the converter 12 that does not stop or set the output voltage to 0 is used. Instead of changing the phase of the output voltage while keeping the voltage value of the output voltage constant, the voltage value of the output voltage of one of the converters 12 is output in reverse.

  As shown in FIG. 9A, the output voltage before reducing the output voltage of the serial multiple AC / DC converter 11 is similar to FIG. 8A, and each of the three phases has a phase difference of 120 °. The voltage values of U1 to W3 are all equal, and | U1 | = | U2 | = | U3 | = | V1 | = | V2 | = | V3 | = | W1 | = | W2 | = | W3 |.

    Now, it is assumed that a voltage reduction command (modulation factor m is m = 1/2) in which the voltage command value Vr of the serial multiple AC / DC converter 11 is ½ times is given. In this case, as shown in FIG. 9B, the output voltages U1, U2 of the two U-phase converters 12U1, 12U2, and the output voltages V1, V2, W of the two V-phase converters 12V1, 12V2. The output voltages W1 and W2 of the two phase converters 12W1 and 12W2 are kept constant, the output voltage u3 of the U-phase converter 12U3, the output voltage v3 of the V-phase converter 12V3, and the W-phase converter The output voltage w3 of 12W3 is set to 0.5 pu output in the reverse direction. As a result, for the U phase, the V phase, and the W phase, an output voltage that is ½ times larger and remains unchanged from the original phase by 120 ° is obtained. This means that the present invention can also be applied to the case of the reverse phase without restricting the phase change range of U3, V3, and W3. Furthermore, the outputs of U1, U2, V1, V2, W1, and W2 can be fixed, and only the voltage vectors of U3, V3, and W3 can be changed. As a result, the control circuits for U1, U2, V1, V2, W1, and W2 can be simplified.

  According to the embodiment of the present invention, when the output voltage of the converter 12 of the serial multiplex conversion device is changed, the output voltage of each converter 12 has the same phase and the same modulation rate as in the prior art. Rather than operating, the phase and voltage value (modulation rate) of the plurality of converters 12 are individually controlled, and the voltage vectors are synthesized into a predetermined voltage vector, so that voltage distortion due to harmonics can be reduced and controlled. . For this reason, it is possible to reduce the size and filter loss by reducing the capacity of the harmonic filter. Moreover, the harmonic loss which generate | occur | produces with a transformer can be reduced by the reduction | decrease of a generated harmonic. Further, since the voltage value (modulation factor) and phase of the output voltage of the converter 12 can be freely changed, it is possible to flexibly cope with the voltage command value of the serial multiple AC / DC converter.

The block diagram of the output voltage control apparatus of the serial multiple type | mold AC / DC converter concerning embodiment of this invention. The circuit block diagram which shows an example of the converter in embodiment of this invention. Explanatory drawing of Example 1 of the voltage command value of each converter of each phase previously memorize | stored in the memory | storage part in embodiment of this invention. Explanatory drawing of Example 2 of the voltage command value of each converter of each phase previously memorize | stored in the memory | storage part in embodiment of this invention. Explanatory drawing of Example 3 of the voltage command value of each converter of each phase previously memorize | stored in the memory | storage part in embodiment of this invention. Explanatory drawing of Example 4 of the voltage command value of each converter of each phase previously memorize | stored in the memory | storage part in embodiment of this invention. Explanatory drawing of Example 5 of the voltage command value of each converter of each phase previously memorize | stored in the memory | storage part in embodiment of this invention. Explanatory drawing of Example 6 of the voltage command value of each converter of each phase previously memorize | stored in the memory | storage part in embodiment of this invention. Explanatory drawing of Example 7 of the voltage command value of each converter of each phase previously memorize | stored in the memory | storage part in embodiment of this invention. The characteristic diagram which shows the relationship between the modulation rate of a converter, and the voltage distortion rate of the output voltage of a converter. The output voltage vector figure at the time of reducing the output voltage of the conventional serial multiplex type | mold AC / DC converter multiplexed with two converters from 1 to 0.8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Series multiple conversion apparatus, 12 ... Converter, 13 ... IGBT, 14 ... DC power supply, 15 ... Winding, 16 ... Transformer, 17 ... Converter control apparatus, 18 ... Voltage command value input means, 19 ... Conversion Voltage command value output means, 20 ... storage section, 21 ... converter control means, 22 ... gate control circuit

Claims (3)

In an output voltage control device of a serial multiple AC / DC converter configured by connecting a plurality of converters that convert electric power in series to each of the three phases, the voltage command value of the serial multiple AC / DC converter is input. At least one of the converters of each phase based on the voltage command value input means for performing and the voltage command value of the voltage increase / decrease and phase change of the serial multiple AC / DC converter input by the voltage command value input means The vector sum of the output voltage of each converter in each phase with the voltage value and phase of the output voltage of one converter fixed and the voltage value and phase of the output voltage of any remaining converter changed. Converter voltage command value output means for outputting the voltage command value of each converter of each phase such that is equal to the voltage command value of the serial multiple AC / DC converter, and from the converter voltage command value output means Converter power The output voltage control apparatus for a multi-series type AC-DC converter, characterized in that on the basis of the command value and a converter control means for controlling the output voltage of each phase of each transducer. The converter control means employs a carrier wave comparison control system that compares an AC voltage waveform based on a voltage command value and a carrier wave, and controls each converter of each phase according to the magnitude of those values, thereby changing the voltage value. 2. The output voltage control apparatus for a serial multiplex AC / DC converter according to claim 1 , wherein the frequency of the carrier wave is changed with respect to the converter. In the output voltage control method for a serial multiple AC / DC converter configured by connecting a plurality of converters for converting electric power in series to each of the three phases, the voltage command value of the serial multiple AC / DC converter is input. The voltage value and phase of the output voltage of at least one converter among the converters of each phase based on the input voltage increase or decrease and phase change voltage command values of the serial multiplex type AC / DC converter. In a state where the voltage value and phase of the output voltage of any of the remaining converters are constant, the vector sum of the output voltages of the converters of each phase is the voltage command value of the serial multiple AC / DC converter. The voltage command value of each converter of each phase to be equal is output, and the output voltage of each converter of each phase is controlled based on the output voltage command value of the converter. Multi-type AC / DC converter Voltage control method.

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