JP2015109757A - High frequency power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency power conversion device which improves device efficiency by preventing a DC current from being increased in the case where a load is capacitive, reducing a passage current peak value of an inverter element, and decreasing a passage current of a thyristor element.SOLUTION: A thyristor rectifier control circuit 10 performs control in such a manner that output power, an output current or an output voltage of an output transformer 7 is fixed by an output power command value, an output current command value or an output voltage command value. In the case where a DC voltage detection value Vdc in a DC connection part between a thyristor rectifier 3 and an inverter part 5 is greater than a DC voltage command value Vdc1, an inverter control circuit 9 performs 180° electrification control. In the case where the DC voltage detection value Vdc is equal to or smaller than the DC voltage command value Vdc1, the inverter control circuit 9 performs proportional integration operation on the basis of a deviation between the DC voltage detection value Vdc and the DC voltage command value Vdc1, and performs pulse width modulation control on the basis of a value resulting a proportional integration operation result from 180°.

Description

  The present invention relates to a high frequency power converter having a thyristor rectifier in an AC / DC converter.

  An example of a main circuit configuration of a conventional high-frequency power converter is shown in FIG. As shown in FIG. 9, the high-frequency power converter 1 includes a thyristor rectifier 3 that converts AC power output from a power source 2 into DC power using a thyristor element, a smoothing capacitor 4 that smoothes the output of the thyristor rectifier 3, An inverter unit 5 that converts DC power into three-phase AC power, a filter circuit 6, and an output transformer 7 are provided, and a three-phase AC voltage is output to a load 8.

  An example of the control method of the high-frequency power converter is shown in FIGS.

  In the control method shown in FIG. 10, the inverter control circuit 9 controls the inverter unit 5 by energizing 180 degrees, and may be either a voltage type or a current type. Further, the inverter unit 5 controls the power factor to be constant (100%) by changing the output frequency with respect to the power factor fluctuation. In Patent Document 1 shown in FIG. 12, zero current switching is performed.

  In the control method shown in FIG. 11, the operation of the inverter unit 5 in the inverter control circuit 9 has a fixed frequency and a conduction width fixed at 180 degrees.

  The control shown in FIG. 10 and FIG. 11 includes the output power constant control, the output current constant control, and the output voltage constant control as the control for the load, and the control target is selected according to the purpose of use. These output power, output voltage, and output current are controlled only by the thyristor rectifier 3.

JP-A-8-223924

  However, when the power factor of the load 8 changes greatly between the leading power factor and the lagging power factor, the following problems occur.

  There is an output transformer 7 between the inverter unit 5 and the load 8, and a voltage is generated by the leakage inductance of the output transformer 7. Here, the voltage drop due to the filter circuit 6 is ignored. This is shown in FIG.

FIG. 13 is a vector diagram showing the relationship between the transformer primary voltage and the output voltage (transformer secondary voltage), and the transformer primary voltage is converted to the secondary side. In the constant output voltage control, in the case of a lagging current load and a leading current load with the same power factor angle, a large difference occurs in the primary voltage of the transformer due to the voltage generated by the leakage inductance of the output transformer 7. When the load 8 is inductive, as shown in FIG. 13, the output voltage V _L is smaller than the transformer primary voltage V _LI, but conversely, when the load 8 is capacitive (the current advances from the voltage), the output The voltage V _C (same as the absolute value of the output voltage V _L of the previous inductive load) is greater than the transformer primary voltage V _CI . That is, the primary voltage of the transformer is higher in the inductive load than in the capacitive load even when the output voltage is the same. This is an influence of the voltage generated on the leakage inductance of the output transformer 7.

  For this reason, in the high-frequency power converter, in the case of constant output voltage control, the voltage of the DC connection is controlled according to the state of the load 8, and the voltage is lower than that of the delayed (inductive) load when the load is advanced (capacitive) There is a need. For this reason, the current of the DC connection portion becomes large at the time of the capacitive load, the passing current peak value becomes high in the inverter element (IGBT, MOSFET, etc.) of the inverter portion 5, and the passing current of the thyristor element is increased in the thyristor rectifier 3. To increase. As a result, both the inverter element and the thyristor element have a large thermal duty (loss), which may increase the number of parallel elements and cause cooling difficulties depending on conditions.

  As described above, in the high-frequency power converter, when the load is capacitive, the increase in DC current is suppressed, the peak value of the passing current of the inverter element is reduced, the passing current of the thyristor element is reduced, and the efficiency of the device is improved. Improvement is an issue.

  The present invention has been devised in view of the conventional problems, and one aspect thereof is a thyristor rectifier that performs AC-DC conversion, a voltage-type inverter unit that performs DC-AC conversion, and an output of the inverter unit. An output transformer, a thyristor rectifier control circuit for controlling a thyristor rectifier, and an inverter control circuit for controlling an inverter unit, wherein the thyristor rectifier control circuit is an output transformer. Output power is controlled to be constant at the output power command value, and the inverter control circuit is 180 degrees when the DC voltage detection value at the DC connection between the thyristor rectifier and the inverter unit is larger than the DC voltage command value. When energization control is performed and the DC voltage detection value is less than or equal to the DC voltage command value, proportional integration is performed based on the deviation between the DC voltage detection value and the DC voltage command value. Perform calculations, and performs pulse width modulation control based on a value obtained by subtracting the proportional integral operation results from 180 degrees.

  As another aspect, a thyristor rectifier that performs AC-DC conversion, a voltage-type inverter unit that performs DC-AC conversion, an output transformer that transforms the output of the inverter unit, and a thyristor rectifier control that controls the thyristor rectifier A high-frequency power converter comprising a circuit and an inverter control circuit for controlling an inverter unit, wherein the thyristor rectifier control circuit is configured such that an output current detection value of an output transformer is constant at an output current command value. The inverter control circuit performs 180 degree energization control when the DC voltage detection value at the DC connection between the thyristor rectifier and the inverter is larger than the DC voltage command value, and the DC voltage detection value is less than the DC voltage command value. In the case of, the proportional-integral calculation is performed based on the deviation between the DC voltage detection value and the DC voltage command value, and the proportional-integral calculation is performed from 180 degrees. And performing a pulse width modulation control based on a value obtained by subtracting the results.

  As another aspect, a thyristor rectifier that performs AC-DC conversion, a voltage-type inverter unit that performs DC-AC conversion, an output transformer that transforms the output of the inverter unit, and a thyristor rectifier control that controls the thyristor rectifier A high-frequency power converter comprising a circuit and an inverter control circuit for controlling an inverter unit, wherein the thyristor rectifier control circuit is configured so that an output voltage detected value of an output transformer is constant at an output voltage command value. The inverter control circuit performs 180 degree energization control when the DC voltage detection value at the DC connection between the thyristor rectifier and the inverter is larger than the DC voltage command value, and the DC voltage detection value is less than the DC voltage command value. In the case of, the proportional-integral calculation is performed based on the deviation between the DC voltage detection value and the DC voltage command value, and the proportional-integral calculation is performed from 180 degrees. And performing a pulse width modulation control based on a value obtained by subtracting the results.

  According to the present invention, in a high-frequency power converter, it is possible to suppress an increase in DC current, lower a passing current peak value of an inverter element, reduce a passing current of a thyristor rectifier, and improve efficiency of the device. Become.

Schematic which shows the main circuit of the high frequency power converter device in embodiment. Schematic which shows the inverter control circuit in embodiment. Schematic which shows the thyristor rectifier control circuit in embodiment. The figure which shows the load range at the time of performing output power constant control when active power is a rated value. The enlarged view of the load operating point of FIG. The time chart which shows the direct current voltage, direct current, and inverter conduction width in constant output power control. A time chart showing DC voltage, DC current, and inverter current width in constant output current control. The time chart which shows the direct current voltage, direct current, and inverter conduction width in output voltage constant control. Schematic which shows an example of a high frequency power converter device. Schematic which shows an example of the control method of a high frequency power converter device. Schematic which shows the other example of the control method of a high frequency power converter device. Schematic which shows the circuit structure of patent document 1. FIG. The vector diagram which shows the relationship between a transformer primary voltage and an output voltage.

  In the present invention, in order to suppress a decrease in the DC voltage at the time of an advanced load, the current width of the inverter unit 5 is limited from a certain value of the DC voltage so that the inverter unit 5 partially bears the voltage control capability, and the DC connection unit This prevents the voltage from dropping. In order to realize this, conventionally, the output power, the output current, and the output voltage are controlled only by the thyristor rectifier 3, but in the present invention, the current width is also controlled by the inverter unit 5.

  Hereinafter, embodiments of the high-frequency power converter according to the present invention will be described in detail with reference to FIGS.

[Embodiment 1]
FIG. 1 is a schematic diagram showing a high-frequency power converter according to this embodiment. As shown in FIG. 1, a high-frequency power converter 1 includes a thyristor rectifier 3 that converts AC power output from a power source 2 into DC power using a thyristor, a smoothing capacitor 4 that smoothes the output of the thyristor rectifier 3, and a DC A voltage type inverter unit 5 that converts electric power into AC power, and outputs an AC voltage to the load 8.

  The power source 2 outputs an alternating current of commercial frequency and is connected to a power system of a power company or a private line of a consumer.

  The thyristor rectifier 3 rectifies the alternating current output from the power supply 2 into a direct current. Further, constant control of the output voltage, output current or output power to the load 8 is performed by the firing angle of the thyristor.

  The smoothing capacitor 4 smoothes the output of the thyristor rectifier 3 and suppresses DC voltage ripple.

  A filter circuit (for example, LC filter) 6 and an output transformer 7 that transforms the output of the inverter unit 5 are interposed between the inverter unit 5 and the load 8.

  FIG. 2 is a block diagram showing the inverter control circuit 9. As shown in FIG. 2, the adding unit 11 calculates a deviation between the DC voltage detection value Vdc of the DC connection unit and a predetermined DC voltage command value Vdc1. When the active power is the rated value, the DC voltage command value Vdc1 is determined so that the DC current Idc becomes the Idc allowable value. A PI (proportional integration) calculation is performed by the PI calculation unit 12 based on the deviation, and the calculation result is output to the switch 13. By this PI calculation, the DC voltage detection value Vdc is controlled to be substantially constant with the DC voltage command value Vdc1.

  The switch 13 outputs 0 when the DC voltage detection value Vdc is larger than the DC voltage command value Vdc1, and outputs the calculation result of the PI calculation unit 12 when the DC voltage detection value Vdc is equal to or less than the DC voltage command value Vdc1. The adding unit 14 subtracts the output of the switch 13 from the 180 ° which is the upper limit of the conduction width and outputs the result to the PWM modulator 15 in order to narrow the conduction width. The PWM modulator 15 performs PWM modulation control based on the output of the adder 14, and outputs single-phase inverter gate signals GU, GV, GX, GY. In the present embodiment, the output frequency is a fixed value (for example, 20 kHz).

  Hereinafter, constant output power control, constant output current control, and constant output voltage control will be described. In the description, all loads are advanced loads.

[Constant output power control]
In the case of constant output power control, the thyristor rectifier control circuit 10 of the thyristor rectifier 3 is obtained by replacing the output voltage effective value Vout and the output voltage command value Vout ^* shown in FIG. 3 with the output power detection value and the output power command value. . The output power detection value is calculated from the output voltage detection value _Vout detected by the voltage detector VT and the output current detection value _Iout detected by the current detector CT. The adder 21 calculates a deviation between the output power detection value and the output power command value. A PI (proportional integration) calculation is performed by the PI calculation unit 22 based on the deviation. By this proportional integration calculation, the output power is controlled to be constant at the output power command value. Based on this proportional-integral calculation result, the rectifier control signal generator 23 generates thyristor rectifier control signals u, v, w, x, y, and z.

  The output power constant control in the present embodiment will be described with reference to FIGS. In FIG. 6, the horizontal axis indicates time, and the vertical axis indicates the DC voltage detection value Vdc, the DC current Idc, and the gate current width of the inverter unit 5 with respect to time. The vicinity of the arrow in FIG. 4 is a load operating point, and (1) to (5) in FIG.

  In the range of (1) to (2), since power control can be performed only by the thyristor rectifier 3, the flow width of the inverter unit 5 is 180 energization. From the point of (2), if the capacity further advances and the inverter unit 5 is energized 180 degrees, the DC voltage detection value Vdc decreases as shown by the one-dot chain line shown in FIG. 6, and the DC current Idc is less than the Idc allowable value. growing. In this embodiment, when the power factor is capacitive and the DC voltage detection value Vdc is lower than the DC voltage command value Vdc1, the switch 13 in the inverter control circuit 9 (FIG. 2) is switched downward, and the inverter current width is reduced. Start narrowing. At this time, DC voltage detection value Vdc≈DC voltage command value Vdc1 is controlled, and an increase in DC current Idc is suppressed. Further, since the flow width becomes narrow, the output voltage decreases.

  The feedback amount of the inverter unit 5 is only the DC voltage detection value Vdc, and the DC voltage detection value Vdc is directly controlled. The first adjustment of the power control is performed by the thyristor rectifier 3, and the power is indirectly controlled by the inverter unit 5 as the second adjustment.

  In (2) to (3), the lead power factor is further increased, but the DC voltage detection value Vdc is substantially constant, and the power is controlled by the flow width of the inverter unit 5. The load state has returned from (3).

[For constant output current control]
Next, a method for constant output current control will be described. The concept of control is the same as in the case of constant output power control.

In the case of the constant output current control, the thyristor rectifier control circuit 10 replaces the output voltage effective value Vout and the output voltage command value Vout ^* shown in FIG. 3 with the output current effective value and the output current command value. The subsequent operation is the same as in the case of constant output power control.

  FIG. 7 shows an example when the power factor decreases with time (when only R increases). The horizontal axis indicates time, and the vertical axis indicates the DC voltage detection value Vdc, the DC current Idc, and the state of the gate current width of the inverter unit 5 with respect to time. The power factor relationship between the operating points (6), (7), and (8) shows the case where the lead power factor (6)> (7)> (8) ((8) is closer to the power factor 1). ing.

  When (6) is advanced and the power factor is large and the inverter unit 5 is subjected to 180-degree energization control, the DC voltage detection value Vdc is lower than the DC voltage command value Vdc1 as indicated by the alternate long and short dash line, and the DC current Idc is lower than the Idc allowable value. growing. Therefore, the DC voltage detection value Vdc is increased by narrowing the flow width of the inverter unit 5, and the DC current Idc is reduced.

  During the period of (6) to (7), the current adjustment is mainly performed by the inverter unit 5. In (7) to (8), the power factor is close to 1, the inverter unit 5 is 180 energization control, and the current adjustment is performed by the thyristor rectifier 3.

[For constant output voltage control]
Next, a method of constant output voltage control will be described. The concept of control is the same as in the case of constant output power control and constant output current control. A thyristor rectifier control circuit 10 is shown in FIG. The operations of the adder 21, the PI calculator 22, and the rectifier control signal generator 23 are the same as those in the case of constant output power control and constant output current control.

  FIG. 8 shows an example when the power factor decreases with time (when only R increases). The horizontal axis indicates time, and the vertical axis indicates the DC voltage detection value Vdc, the DC current Idc, and the state of the gate current width of the inverter unit 5 with respect to time. The power factor relationship between the operating points (9), (10), and (11) shows a case where the advance power factor (9)> (10)> (11) (11 is closer to the power factor 1).

  When (9) advances and the degree of the power factor is large and the inverter unit 5 is 180 degrees energization control, as shown in FIG. 8, the DC voltage detection value Vdc is lower than the DC voltage command value Vdc1 as indicated by the alternate long and short dash line. The current Idc becomes larger than the Idc allowable value. Therefore, the DC voltage detection value Vdc is increased by narrowing the flow width of the inverter unit 5, and the DC current Idc is reduced.

  During the periods (9) to (10), the voltage adjustment is mainly performed by the inverter unit 5. In (10) to (11), the power factor is close to 1, the inverter unit 5 performs 180 energization control, and voltage adjustment is performed by the thyristor rectifier 3.

  When the load 8 becomes capacitive and it is necessary to reduce the output voltage, the inverter control circuit 9 suppresses the decrease in the DC voltage detection value Vdc by narrowing the inverter conduction width from the DC voltage command value Vdc1, An increase in the direct current Idc can be suppressed. As a result, the inverter unit 5 can reduce the passing current peak value in the inverter element (IGBT, MOSFET, etc.), and the thyristor rectifier 3 can reduce the passing current, thereby providing a highly efficient device.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are naturally within the scope of the claims.

DESCRIPTION OF SYMBOLS 1 ... High frequency power converter 2 ... Power supply 3 ... Thyristor rectifier 5 ... Inverter part 7 ... Output transformer 8 ... Load 9 ... Inverter control circuit 10 ... Thyristor rectifier control circuit Vdc ... DC voltage detection value Vdc1 ... DC voltage command value

Claims (3)

A thyristor rectifier that performs AC-DC conversion;
A voltage-type inverter unit for performing DC-AC conversion;
An output transformer for transforming the output of the inverter unit;
A thyristor rectifier control circuit for controlling the thyristor rectifier;
An inverter control circuit for controlling the inverter unit;
A high-frequency power conversion device comprising:
The thyristor rectifier control circuit controls the output power of the output transformer to be constant at the output power command value,
When the DC voltage detection value at the DC connection between the thyristor rectifier and the inverter unit is larger than the DC voltage command value, the inverter control circuit performs 180-degree conduction control, and when the DC voltage detection value is equal to or less than the DC voltage command value, A high frequency power conversion characterized by performing proportional integral calculation based on a deviation between a DC voltage detection value and a DC voltage command value and performing pulse width modulation control based on a value obtained by subtracting the proportional integral calculation result from 180 degrees. apparatus. A thyristor rectifier that performs AC-DC conversion;
A voltage-type inverter unit for performing DC-AC conversion;
An output transformer for transforming the output of the inverter unit;
A thyristor rectifier control circuit for controlling the thyristor rectifier;
An inverter control circuit for controlling the inverter unit;
A high-frequency power conversion device comprising:
The thyristor rectifier control circuit controls the output current detection value of the output transformer to be constant at the output current command value,
When the DC voltage detection value at the DC connection between the thyristor rectifier and the inverter unit is larger than the DC voltage command value, the inverter control circuit performs 180-degree conduction control, and when the DC voltage detection value is equal to or less than the DC voltage command value, A high frequency power conversion characterized by performing proportional integral calculation based on a deviation between a DC voltage detection value and a DC voltage command value and performing pulse width modulation control based on a value obtained by subtracting the proportional integral calculation result from 180 degrees. apparatus. A thyristor rectifier that performs AC-DC conversion;
A voltage-type inverter unit for performing DC-AC conversion;
An output transformer for transforming the output of the inverter unit;
A thyristor rectifier control circuit for controlling the thyristor rectifier;
An inverter control circuit for controlling the inverter unit;
A high-frequency power conversion device comprising:
The thyristor rectifier control circuit controls the output voltage detection value of the output transformer to be constant at the output voltage command value,
When the DC voltage detection value at the DC connection between the thyristor rectifier and the inverter unit is larger than the DC voltage command value, the inverter control circuit performs 180 degree energization control, and when the DC voltage detection value is less than the DC voltage command value A high frequency power conversion characterized by performing proportional integral calculation based on a deviation between a DC voltage detection value and a DC voltage command value and performing pulse width modulation control based on a value obtained by subtracting the proportional integral calculation result from 180 degrees. apparatus.

Images