JP4825660B2 - Power converter for superconducting coils - Google Patents

Description

  The present invention relates to a power converter for a superconducting coil applied to, for example, a superconducting energy storage system (hereinafter referred to as SMES), and more particularly, a DC power between a three-level DC power source and a superconducting coil. The present invention relates to a control technology for a three-level chopper that performs transfer.

Power converters with power storage systems are capable of advanced power conversion control through the application of power electronics technology, such as instantaneous voltage drop due to power system accidents or lightning strikes, and power load fluctuations in railways, etc. Development and introduction are being promoted as means for solving various problems of electric power systems. In general, such a power conversion device uses a voltage-type inverter as a power converter that bidirectionally converts AC power of an interconnected power system and power of a power storage system. As a high-voltage and large-capacity voltage source inverter, there is a multi-level inverter. In recent years, a three-level system (three-level inverter), which is one type, has been put into practical use and has many applications.
On the other hand, there are various types of power storage devices for power storage systems, such as various secondary batteries including lead-acid batteries, and devices that store mechanical power such as flywheels, but SMES using superconducting coils. The development of a small and large-capacity system in which is applied to power converters is underway.

As a conventional SMES power converter, for example, the one disclosed in Patent Document 1 performs input / output of power of a superconducting coil by a two-level chopper circuit, and turns on two semiconductor switching elements constituting the chopper circuit. -The voltage applied to the superconducting coil is adjusted by off control, and the superconducting coil current is increased and decreased, and the superconducting coil current is maintained by the recirculation operation.
A specific power input / output control method is disclosed in Patent Document 2, for example. Here, a command value of active power to be input / output by the SMES is given to the chopper power controller. The chopper power controller outputs a command value of a voltage to be applied to the superconducting coil from the active power command value and the current flowing through the superconducting coil. A PWM (Pulse Width Modulation) controller performs PWM control based on this voltage command value, and outputs a drive signal for turning on / off the semiconductor switching element of the chopper circuit. For the PWM control, a triangular wave comparison method generally used in a two-level voltage source inverter can be applied.

When a three-level inverter is applied as a voltage source inverter of a high-voltage and large-capacity SMES power converter, a three-level type chopper circuit is required. FIG. 10 is a three-level chopper circuit disclosed in Non-Patent Document 1, for example, and has a configuration in which the two-level chopper circuit is tri-leveled in the same manner as the inverter in which the two-level inverter is tri-leveled.
Therefore, a control method generally used in a three-level inverter can be applied to the PWM control of the three-level chopper. FIG. 11 shows PWM control by the double carrier unipolar system shown in Non-Patent Document 1, and a voltage corresponding to the voltage command value is applied to the superconducting coil.

  FIG. 12 shows the on / off states of the semiconductor switching elements G1 to G4 in the three-level chopper circuit when the same double carrier unipolar PWM control as in FIG. 11 is performed. The switching pattern SP shown in FIG. 12 includes four semiconductor switching elements (7a, 7b, 8a, 8b) constituting the three-level chopper circuit described in FIG. 3 of the first embodiment of the invention. In FIG. 12, switching patterns corresponding to a total of 16 on / off states which can be taken by G1 to G4) are numbered.

  In FIG. 12, when charging the superconducting coil that increases the current flowing in the superconducting coil, the voltage command value is positive, and only the outer elements G1 and G4 of the three-level chopper circuit are repeatedly turned on and off, and the inner element G2, G3 remains on and does not switch. Conversely, during superconducting coil discharge that reduces the current flowing in the superconducting coil, the voltage command value is negative, only the inner elements G2 and G3 perform switching, and the outer elements G1 and G4 remain off. . At this time, although the switching pattern used differs depending on whether the voltage command value is positive or negative, if the voltage command value is constant, there are three types of switching patterns to be used. Further, among the switching patterns of FIG. 3, there are five types of zero voltage output patterns with an output voltage of 0 V, whereas the zero voltage output pattern used in FIG. 12 is only one type of SP6.

Japanese Patent No. 2543336 (FIGS. 1 and 2) Japanese Patent No. 2771948 (FIG. 1) Funabashi, Takayanagi, Hayashi, Sannomiya, Tsutsumi: “Conceptual design of voltage-type AC / DC converter for 100 MVA class SMES”, IEEJ Electric Power Technology Study Group, PE-01-12, pp. 67-72, 2001 (Figures 2 and 3)

As described above, in the conventional double carrier unipolar system of the three-level chopper used in the SMES power converter, the drive signal of the switching element is controlled by the logic output based on the comparison between the voltage command value and the triangular wave. Therefore, the switching elements that perform the on / off operation with respect to the voltage command value are limited to two specific elements.
For this reason, depending on the operation pattern required in each application, for example, when it is desired to pursue a direction in which the load factor of each element is equalized by setting three or more switching elements that perform on / off operation, and operations such as charging and discharging. Even if there is a case where smooth mode transition occurs, the conventional method of driving a switching element with a logical output by comparing a voltage command value and a triangular wave is not able to meet these various requirements. was there.

  The present invention has been made to solve the above-described conventional problems, and in the three-level chopper, the switching element that performs the on / off operation is not limited to two elements that are determined according to the voltage command value. An object of the present invention is to obtain a power converter for a superconducting coil that can give a degree of freedom in selection and can be applied to a wider range of uses.

A power converter for a superconducting coil according to the present invention is connected between a three-level DC power source having a positive terminal, a negative terminal, and a neutral point terminal, and a superconducting coil having a positive and negative bipolar terminal. A switching element is provided, and a DC output voltage to the bipolar terminal of the superconducting coil follows the voltage command value, and a three-level chopper that transfers DC power between the DC power supply and the superconducting coil by turning on and off each switching element. In the superconducting coil power converter equipped with a chopper control means for controlling on / off of each switching element,
The chopper control means sets in advance a switching pattern for specifying the on / off control order of each switching element for each of a plurality of types of control modes related to charging / discharging of the superconducting coil, and sets the corresponding control mode according to the voltage command value. A switching pattern selection unit for selecting the switching pattern, and a signal for driving on / off of each switching element by calculating the output voltage pulse width of the three-level chopper by the switching pattern selected so that the DC output voltage matches the voltage command value It is provided with a pulse generating unit for generating.

  In the present invention, since an arbitrary switching pattern can be set for each control mode, each switching element constituting the three-level chopper can be turned on and off in a direction satisfying the individually required characteristics. As a power converter, it can be applied to a wider range of uses.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing an example of a superconducting coil power conversion device according to Embodiment 1 of the present invention.
Two DC capacitors 4a and 4b are connected in series between the DC output terminals (positive side terminal, negative side terminal and neutral point terminal) of the voltage source inverter circuit 3 connected to the power system 1 via the transformer 2. . The chopper circuit 6 that is a three-level chopper performs bidirectional power conversion by the chopper operation between the two DC capacitors 4a and 4b serving as a DC power source and the superconducting coil 5.

  The voltage source inverter circuit 3 is a high-voltage and large-capacity three-phase three-level inverter. As a semiconductor switching element having a self-extinguishing function, for example, a high-voltage, high-current GTO thyristor (Gate Turn-Off Thyristor) or GCT A thyristor (Gate Committed Turn-off Thyristor) or the like is applied, but a conventional power transistor or an IGBT (Insulated Gate Bipolar Transistor) whose breakdown voltage has been increasing in recent years is also applicable. Since the three-phase three-level inverter is not a main part in the present application, and its configuration and operation are known, detailed description thereof is omitted.

The chopper circuit 6 is a voltage reversible chopper circuit as shown in FIG. 2 and is a bridge type chopper circuit having a three-level configuration similar to that of the voltage source inverter circuit 3. However, the direction of the current flowing through the superconducting coil 5 is uniform. When the direction is fixed, the semiconductor switching element for reversing the direction of the current becomes unnecessary, so the number of semiconductor elements used is halved.
That is, two sets of semiconductors are formed by a series connection set of semiconductor switching elements 7a and 7b as first and second switching elements and a series connection set of semiconductor switching elements 8a and 8b as third and fourth switching elements. A semiconductor connected in series with a switching element, and similarly, two sets of diodes by a series connection set of diodes 9a and 9b as first diodes and a series connection set of diodes 10a and 10b as second diodes It is composed of two clamp diodes 11a and 11b which are first and second clamp diodes for clamping a connection point between the switching elements to a neutral point terminal.

  In FIG. 2, the GTO is applied as the semiconductor switching element. However, the semiconductor switching element may be replaced with another semiconductor switching element such as a GCT, a power transistor, or an IGBT corresponding to the semiconductor switching element applied in the voltage source inverter circuit 3. Good. Further, a group of two diodes connected in series may be replaced with one diode if it has a sufficient withstand voltage with respect to the DC circuit voltage.

  Next, with regard to the chopper circuit 6 shown in FIG. 2, a specific chopper operation will be described with reference to FIG. FIG. 3 shows all the switching patterns that the chopper circuit 6 can take. That is, since the chopper circuit 6 includes the four semiconductor switching elements 7a, 7b, 8a, and 8b, it can take a total of 16 combinations of on / off states SP0 to SP15 shown in FIG. Depending on the current path flowing in each of the switching patterns SP0 to SP15, it can be broadly classified into three types of operation modes: charging or discharging of the DC capacitors 4a and 4b, and the circulating state of the superconducting coil current.

  However, in the switching patterns SP0 to SP15, even if the semiconductor switching element 7a (or 8b) is switched when the semiconductor switching element 7b (or 8a) is off, the current path does not change. Therefore, SP1, 8, and 9 have the same current path as SP0. Similarly, SP2 and SP10, SP3 and SP11, SP4 and SP5, and SP12 and SP13 have the same current path. Therefore, when the semiconductor switching element 7b (or 8a) is off, if it is decided to always turn off the semiconductor switching element 7a (or 8b), the switching patterns to be used are SP0, 2, 3, 4, 6 among all 16 patterns. , 7, 12, 14, 15 Thereby, the control which selects a switching pattern can be simplified.

4A to 4D show the switching patterns SP0, 2, 3 and 4, respectively. FIGS. 5A to 5D show the same SP6, 7, 12 and 14, respectively. FIG. The current paths of SP15 are shown respectively.
3 and 4 to 6, SPs 7, 14, and 15 are switching patterns that increase the current flowing through the superconducting coil 5, and are therefore used in the superconducting coil charging control mode. Among these patterns, SP15 outputs voltage 2E, and SP7 and SP14 output voltage E to charge the superconducting coil 5.
SP0, 2, 4 are switching patterns for reducing the current flowing through the superconducting coil 5, and are used in the superconducting coil discharge control mode. Among them, SP0 is a pattern for outputting a voltage (−2E), and SP2 and 4 are patterns for outputting a voltage (−E) to discharge from the superconducting coil 5.
SP3, 6 and 12 are switching patterns in which the current of the superconducting coil 5 circulates through the chopper circuit 6, and is a zero voltage output pattern in which no voltage is applied to the superconducting coil 5. These zero voltage output switching patterns are used to maintain the current flowing through the superconducting coil 5, but a slight loss occurs when flowing through the semiconductor element, so the superconducting coil current gradually decreases. Therefore, except for the superconducting coil charge control mode and the superconducting coil discharge control mode described above, a superconducting coil current compensation control mode for holding the superconducting coil current while compensating for the decrease in the superconducting coil current is provided. Therefore, there are three types of control modes for the chopper circuit 6: a superconducting coil charge control mode, a superconducting coil discharge control mode, and a superconducting coil current compensation control mode.

  In the present invention, a switching pattern for specifying the on / off control order of each switching element is set in advance for each of these control modes and stored in the PWM controller 14 which is a chopper control means. Hereinafter, an example of the order of switching patterns set for each control mode will be described with reference to FIGS.

FIG. 7 shows the order of switching patterns in the superconducting coil charge control mode. In order to smoothly switch to other control modes, SP3 and SP12 having a switching pattern common to the other control modes are provided. That is, it is possible to shift to the position of SP3 or SP12 of another control mode in the operation state of the recirculation mode by SP3 or SP12 which is the switching pattern of zero voltage output. Also, considering the continuity of the switching pattern so that two or more semiconductor switching elements do not switch at the same time, the order of SP12 → SP14 → SP15 → SP7 → SP3 → SP7 → SP15 → SP14 → SP12 is set as one cycle. repeat. As a result, each semiconductor switching element performs an on / off switching operation once.
The superconducting coil charging control mode is executed when the current of the superconducting coil 5 is greatly reduced from the rated value, such as immediately after outputting a large amount of power from the power converter, and the DC circuit voltage is applied to the superconducting coil during the pattern period of SP15. 5 to increase the superconducting coil current.

  As described above, since only one semiconductor switching element performs an on or off operation when the switching pattern rank advances by one, the control is simple, and four semiconductor switching elements are provided in one cycle shown in FIG. However, since all ON / OFF operations are performed once, there is an advantage that the ON / OFF operations are not concentrated on some elements and are equalized as in the prior art.

Here, the reason for setting the order of the switching patterns shown in FIG. 7 will be described in more detail.
In the superconducting coil charging control mode shown in FIG. 7, in order to charge the superconducting coil 5, the output voltage of the chopper circuit 3 needs to be positive (0 to 2E). Therefore, in this mode, SP7, 14 and 15 whose output voltage is E or 2E is selected, and the output voltage is controlled according to the output voltage command value by adjusting the output time (pulse width) of each pattern. Become. However, if the pulse width control is performed only with these three patterns SP7, 14, and 15, the average output voltage obtained is in the range of E to 2E regardless of the order and the pulse width. Therefore, a zero voltage output pattern is also required to cope with output voltage command values of 0 to E.

Next, as a pulse output order, it is considered that 0 → E → 2E → E → 0 is repeated in terms of output voltage. The reason for this is that when any two of the four elements in the zero voltage output pattern are on, and all four of the 4E outputs are on, the condition that two or more switching is not performed simultaneously is applied. This is because the order of 0 → 2E or 2E → 0 always requires two elements to be turned on or off and does not meet the conditions.
On the other hand, in the pattern of E output, three elements are in an on state, and only one element is turned on or off by combining appropriate patterns in the order of 0 ← → E and E ← → 2E. Therefore, the voltage output can be increased or decreased, and the above conditions can be satisfied.

Here, there are three possible zero voltage output patterns SP3, 6, and 12 (SP11 and 13 have already been excluded), and a case where SP6 is combined with three positive voltage output patterns SP7, 14, and 15 is considered. And the order in which all the elements are switched equally cannot be obtained. The same applies when SP3 or SP12 is used as a zero voltage output pattern instead of SP6 and combined with three positive voltage output patterns.
Another way to select zero voltage output is to select and combine two patterns from three patterns, or to combine all three patterns, but only when two of SP3 and SP12 are selected and combined. The order in which the elements in FIG. 7 are switched evenly is obtained, which is the content shown in FIG.

Next, FIG. 8 shows a switching pattern arrangement in the superconducting coil discharge control mode. SP3 and SP3 which are zero voltage output patterns for switching to other control modes are provided, and switching patterns are continuously arranged in the order of SP12 → SP4 → SP0 → SP2 → SP3 → SP2 → SP0 → SP4 → SP12. Is repeated as one cycle. As a result, as in the superconducting coil charging control mode, each semiconductor switching element performs on / off switching once.
The basis for setting the switching pattern order shown in FIG. 8 is the same as in the case of FIG. 7, and the description thereof is omitted.
The superconducting coil discharge control mode is executed when power is output from the power converter, and supplies the power of the superconducting coil 5 to the DC circuit in the SP0 pattern period.

FIG. 9 shows a switching pattern arrangement in the superconducting coil current compensation control mode. The amount of decrease in the superconducting coil current in the recirculation state is slight, and the voltage command value in the case of compensating charging for the decrease is close to 0. Therefore, a voltage E that is half the DC circuit voltage is applied to the superconducting coil 5. Set the mode. Thereby, compared with the case where the DC circuit full voltage 2E is applied, the gradient in which the current rises is halved, and charging with a small current ripple can be performed. Therefore, SP7 and SP14 which output voltage E are used, and SP3 and SP12 which are zero voltage output patterns for smoothly switching to other control modes are provided.
Furthermore, as in the other control modes, in order to satisfy the condition that each semiconductor switching element performs on / off switching once at all, SP6 which is a zero voltage output pattern is added, thereby continuously switching patterns. And repeat the order of SP12 → SP14 → SP6 → SP7 → SP3 → SP7 → SP6 → SP14 → SP12 as one cycle.

  Next, the operation of the PWM controller 14 will be described with reference to FIG. The chopper power controller 13 calculates the command value Vdref of the voltage to be output by the chopper circuit 6 based on the superconducting coil current Id and the power command value Pref output from the inverter power controller 12, and outputs it to the PWM controller 14. To do. The control mode selection unit 15 of the PWM controller 14 selects the control mode of the chopper circuit 6 based on the voltage command value Vdref. That is, the superconducting coil discharge control mode based on the negative voltage command value, the superconducting coil charge control mode based on the positive voltage command value after the coil discharge control, and the minute positive voltage command when the superconducting coil current Id is almost the rated value. Based on the value, one of the superconducting coil current compensation control mode and the three control modes is selected. The switching pattern selection unit 16 selects and outputs five types of switching patterns corresponding to the control modes shown in FIGS. 7 to 9 based on the control mode signal output from the control mode selection unit 15.

When the superconducting coil charging control mode is selected by the control mode selection unit 15, the switching pattern selection unit 16 transmits the five types of switching patterns SP 3, 7, 12, 14, and 15 shown in FIG. 7 to the pulse generation unit 17. Output. When the switching pattern output in the previous control mode is SP3 or SP12 which is the zero voltage output pattern, the pulse generator 17 shifts to the switching pattern based on the new control mode, and the switching pattern shown in FIG. Create output pulses in order.
For example, when SP3 is being output, output pulses are generated in the order of switching patterns starting from SP3 shown in FIG. 7, that is, SP3 → SP7 → SP15 → SP14 → SP12 → SP14 → SP15 → SP7 → SP3. To do. When the SP12 is being output, the output pulses are generated in the order of SP12 → SP14 → SP15 → SP7 → SP3 → SP7 → SP15 → SP14 → SP12 starting from SP12.

In addition, the pulse generator 17 determines the output duration (output pulse width) of each switching pattern so that the average output voltage of the chopper circuit 6 is equal to the voltage command value Vdref (= 0 to 2E). That is, the output duration time of SP3 is t3, the output duration time of SP7 is t7, the output duration time of SP12 is t12, the output duration time of SP14 is t14, the output duration time of SP15 is t15, and the time that the switching pattern makes a round is T1. Then,
T1 = t3 + t7 × 2 + t12 + t14 × 2 + t15 × 2
The average output voltage of the chopper circuit 6 is
(E * t7 * 2 + E * t14 * 2 + 2E * t15 * 2) / T1 = Vdref
It becomes.

  Therefore, the pulse generation unit 17 sequentially outputs information on the output order of the switching patterns and the output duration of each switching pattern as a drive signal to the chopper circuit 6. As a result, any one of the five types of switching patterns is input to the chopper circuit 6. In this order, two or more semiconductor switching elements do not switch at the same time, and all the semiconductor switching elements perform the same number of on / off switching operations, and the DC circuit is used in the pattern periods of SP7, 14, and 15. The voltage E or 2E is applied to the superconducting coil 5 to increase the superconducting coil current.

  The case where the superconducting coil discharge control mode is selected by the control mode selection unit 15 is the same as the case where the superconducting coil charge control mode is selected, and the switching pattern selection unit 16 includes the SP0, 2, 3 shown in FIG. 4 and 12 are output to the pulse generator 17. When the switching pattern output in the previous control mode is SP3 or SP12, which is the zero voltage output pattern, the pulse generator 17 shifts to a switching pattern based on a new control mode, and SP3 is being output. Is SP3 → SP2 → SP0 → SP4 → SP12 → SP4 → SP0 → SP2 → SP3 in the order shown in FIG. 8 when SP12 is being output, SP12 → SP4 → SP0 → starting from SP12 Output pulses are generated in the order of SP2-> SP3-> SP2-> SP0-> SP4-> SP12.

In addition, the pulse generator 17 outputs the SP0 output duration t0, the SP2 output duration t2, the SP3 output duration t3, and the SP4 output for the voltage command value Vdref (= -2E to 0). Assuming that the duration is t4, the output duration of SP12 is t12, and the time that the switching pattern makes a round is T2, the average output voltage of the chopper circuit 6 is
(-2E * t0 * 2-E * t2 * 2-E * t4 * 2) / T2 = Vdref
However, T2 = t0 × 2 + t2 × 2 + t3 + t4 × 2 + t12
The output duration (output pulse width) of each switching pattern is determined so that
The pulse creation unit 17 sequentially outputs the output order of the switching patterns and the determined output duration time of each switching pattern as a drive signal, so that any one of the five types of switching patterns is input to the chopper circuit 6. Is done. The order is that two or more semiconductor switching elements do not switch at the same time, and all the semiconductor switching elements perform the same number of on / off switchings. The circuit voltage -E or -2E is applied to the superconducting coil 5 to reduce the superconducting coil current.

  The case where the superconducting coil current compensation control mode is selected by the control mode selection unit 15 is the same as the case where the superconducting coil charging control mode and the superconducting coil discharge control mode are selected, and the switching pattern selection unit 16 is shown in FIG. The five types of switching patterns SP3, 6, 7, 12, and 14 shown are output to the pulse generator 17. When the switching pattern output in the previous control mode is SP3 or SP12, which is the zero voltage output pattern, the pulse generator 17 shifts to a switching pattern based on a new control mode, and SP3 is being output. When SP12 is shifted during output in the order of SP3 → SP7 → SP6 → SP14 → SP12 → SP14 → SP6 → SP7 → SP3 shown in FIG. 9, SP12 → SP14 → SP6 → Output pulses are generated in the order of SP7-> SP3-> SP7-> SP6-> SP14-> SP12.

Further, the pulse generator 17 sets the output duration of SP3 to t3, the output duration of SP6 to t6, the output duration of SP7 to t7, and the output duration of SP12 to the minute positive voltage command value Vdref. Assuming that the output duration time of t12, SP14 is t14, and the time for which the switching pattern makes a round is T3, the average output voltage of the chopper circuit 6 is
(E * t7 * 2 + E * t14 * 2) / T3 = Vdref
However, T3 = t3 + t6 × 2 + t7 × 2 + t12 + t14 × 2
The output duration (output pulse width) of each switching pattern is determined so that
The pulse creation unit 17 sequentially outputs the output order of the switching patterns and the determined output duration time of each switching pattern as a drive signal, so that any one of the five types of switching patterns is input to the chopper circuit 6. Is done. The order is that two or more semiconductor switching elements do not switch at the same time, and all the semiconductor switching elements perform the same number of on / off switchings, and the DC circuit voltage is changed in the pattern period of SP7 and SP14. E is applied to the superconducting coil 5 to increase the superconducting coil current to compensate for the current decrease due to circuit loss.

  As described above, in the first embodiment of the present invention, in all three types of control modes of the chopper circuit 6, the control within each control mode is simple and smooth without switching two or more semiconductor switching elements simultaneously. Become. In addition, the switching frequency of each semiconductor switching element can be averaged, and heat generated by switching can be distributed to each semiconductor switching element. Further, since the zero voltage output patterns SP3 and SP12 common to all the control modes are provided, the switching of each control mode can be smoothly performed.

In the first embodiment of the present invention, the order of the switching patterns in the three control modes is shown in FIGS. 7 to 9, respectively. However, the switching that specifies the on / off control order of each switching element in advance for each control mode. The application of the present invention in which a pattern is set and the switching pattern set in the corresponding control mode is selected according to the voltage command value is not necessarily limited to the order shown in the illustrated figure.
Even in such a case, the switching element that performs the on / off operation is not limited to two elements that are determined according to the voltage command value as in the conventional case, and the selection can be given a degree of freedom. The problem of the present invention that it can be applied can be solved.

  Further, in each modification of the present invention, the three-level chopper includes a first switching element whose anode is connected to the positive terminal of the DC power supply, and is connected in series with the cathode side of the first switching element, and the cathode is superconducting. A second switching element connected to the positive terminal of the coil; a third switching element whose anode is connected to the negative terminal of the superconducting coil; and a cathode connected to the cathode side of the third switching element in series. Fourthly, the switching element connected to the negative terminal, the anode connected to the negative terminal of the DC power supply, the cathode connected to the positive terminal of the superconducting coil, and the anode connected to the negative terminal of the superconducting coil The second diode whose cathode is connected to the positive terminal of the DC power supply, and the anode is connected to the neutral point terminal of the DC power supply A first clamp diode connected to the connection point of the first and second switching elements, and an anode connected to the connection point of the third and fourth switching elements, and the cathode to the neutral point terminal of the DC power supply Since the second clamp diode to be connected is provided, it is possible to reliably realize a three-level chopper that can satisfy an individually required characteristic by setting an arbitrary switching pattern for each control mode. Become.

Also, when the voltages of the positive side terminal, the negative side terminal and the neutral point terminal of the DC power source are + E, -E and 0, respectively, and the DC output voltage average value of the three-level chopper is ED,
The plurality of types of control modes are a superconducting coil charge control mode that controls in a voltage range of + 2E>ED> 0, a superconducting coil discharge control mode that controls in a voltage range of 0>ED> −2E, and a voltage of + E>ED> 0 Since the superconducting coil current compensation control mode is controlled in a range, the operation necessary for the superconducting coil is surely performed.

The switching pattern set in the superconducting coil charging control mode includes the following ON / OFF control of each switching element (the first to fourth switching elements are indicated as SW-1 to SW-4). Therefore, the superconducting coil can be charged smoothly and reliably.
Rank SW-1 SW-2 SW-3 SW-4
1 ON ON OFF OFF
2 ON ON ON OFF
3 ON ON ON ON
4 OFF ON ON ON
5 OFF OFF ON ON
6 OFF ON ON ON
7 ON ON ON ON
8 ON ON ON OFF
1 ON ON OFF OFF

In addition, the switching pattern set in the superconducting coil discharge control mode includes the following ON / OFF control of each switching element (the first to fourth switching elements are indicated as SW-1 to SW-4). Therefore, the discharging operation of the superconducting coil is smoothly and reliably performed.
Rank SW-1 SW-2 SW-3 SW-4
1 ON ON OFF OFF
2 OFF ON OFF OFF
3 OFF OFF OFF OFF
4 OFF OFF ON OFF
5 OFF OFF ON ON
6 OFF OFF ON OFF
7 OFF OFF OFF OFF
8 OFF ON OFF OFF
1 ON ON OFF OFF

In addition, the switching pattern set in the superconducting coil current compensation control mode is ON / OFF control of each switching element (the first to fourth switching elements are indicated as SW-1 to SW-4). Since the repetition is performed in the following order, the current compensation operation of the superconducting coil is smoothly and reliably performed.
Rank SW-1 SW-2 SW-3 SW-4
1 ON ON OFF OFF
2 ON ON ON OFF
3 OFF ON ON OFF
4 OFF ON ON ON
5 OFF OFF ON ON
6 OFF ON ON ON
7 OFF ON ON OFF
8 ON ON ON OFF
1 ON ON OFF OFF

  In addition, when shifting the control mode from the previous control mode to another control mode according to the change in the voltage command value, each switching element is turned on / off from the switching pattern order in which the output voltage in the control mode before the transition becomes zero. Since the transition to the switching pattern order in the transition destination control mode that is the same as the on / off state of the switching pattern order before transition is made, the switching transition of each control mode is performed smoothly.

It is a figure which shows the structure of the power converter device for superconducting coils in Embodiment 1 of this invention. It is an internal block diagram of the chopper circuit 6 in Embodiment 1 of this invention. 6 is a switching pattern table showing all combinations of on / off states that can be taken by the semiconductor switching element of the chopper circuit 6. 3 is a diagram showing current paths in switching patterns SP0, SP2, SP3, SP4 of the chopper circuit 6. FIG. Similarly, it is a diagram showing a current path in each switching pattern SP6, SP7, SP12, SP14 of the chopper circuit 6. FIG. Similarly, it is a figure which shows the electric current path in switching pattern SP15 of the chopper circuit 6. FIG. It is a figure which shows the order of the switching pattern in the superconducting coil charge control mode in Embodiment 1 of this invention. It is a figure which shows the order of the switching pattern in the superconducting coil discharge control mode in Embodiment 1 of this invention. It is a figure which shows the order of the switching pattern in the superconducting coil current compensation control mode in Embodiment 1 of this invention. It is a figure which shows the conventional 3 level chopper circuit and a superconducting coil. It is a wave form diagram which shows the PWM control method of the conventional 3 level chopper circuit. It is a wave form diagram which shows the ON / OFF state of each semiconductor switching element at the time of performing PWM control of the conventional 3 level chopper circuit.

Explanation of symbols

3 Voltage source inverter circuit, 4a, 4b DC capacitor, 5 superconducting coil,
6 chopper circuit, 7a, 7b, 8a, 8b semiconductor switching element,
9a, 9b, 10a, 10b diode, 11a, 11b clamp diode,
12 inverter power controller, 13 chopper power controller, 14 PWM controller,
15 control mode selector, 16 switching pattern selector, 17 pulse generator,
Vdref Voltage command value.

Claims (7)

Connected between a three-level DC power source having a positive terminal, a negative terminal, and a neutral point terminal and a superconducting coil having a positive and negative bipolar terminal, a plurality of switching elements are provided, and each of the switching elements is turned on / off As a result, a three-level chopper that transmits and receives DC power between the DC power supply and the superconducting coil, and on / off control of the switching elements so that the DC output voltage to the bipolar terminals of the superconducting coil follows the voltage command value. In the superconducting coil power converter equipped with the chopper control means to
The chopper control means sets a switching pattern for specifying an on / off control order of each switching element in advance for each of a plurality of types of control modes related to charging / discharging of the superconducting coil, and corresponds to the voltage command value. A switching pattern selection unit that selects a switching pattern set in a control mode, and calculates an output voltage pulse width of the three-level chopper by the selected switching pattern so that the DC output voltage matches the voltage command value; A superconducting coil power converter comprising a pulse generating unit that generates a signal for driving on and off each switching element. The three-level chopper has a first switching element whose anode is connected to the positive terminal of the DC power supply, and is connected in series with the cathode side of the first switching element, and the cathode is connected to the positive terminal of the superconducting coil. A second switching element, a third switching element whose anode is connected to the negative terminal of the superconducting coil, a cathode connected to the cathode side of the third switching element, and a cathode connected to the negative terminal of the DC power supply Fourth, a switching element, a first diode whose anode is connected to the negative terminal of the DC power supply and a cathode connected to the positive terminal of the superconducting coil, an anode connected to the negative terminal of the superconducting coil, and the cathode A second diode and an anode connected to the positive terminal of the DC power supply are connected to a neutral point terminal of the DC power supply. A first clamp diode whose cathode is connected to a connection point of the first and second switching elements, and an anode which is connected to a connection point of the third and fourth switching elements, and a cathode in the DC power source. The superconducting coil power converter according to claim 1, further comprising a second clamp diode connected to the sex point terminal. When the voltages of the positive terminal, negative terminal and neutral point terminal of the DC power supply are + E, −E and 0, respectively, and the DC output voltage average value of the three-level chopper is ED,
The plurality of types of control modes include a superconducting coil charge control mode that controls in a voltage range of + 2E>ED> 0, a superconducting coil discharge control mode that controls in a voltage range of 0>ED> −2E, and + E>ED> 0. The superconducting coil power converter according to claim 2, comprising a superconducting coil current compensation control mode controlled in a voltage range. The switching pattern set in the superconducting coil charging control mode includes the following ON / OFF control of each switching element (the first to fourth switching elements are indicated as SW-1 to SW-4). 4. The superconducting coil power converter according to claim 3, wherein the power converter is repeated in order.
Rank SW-1 SW-2 SW-3 SW-4
1 ON ON OFF OFF
2 ON ON ON OFF
3 ON ON ON ON
4 OFF ON ON ON
5 OFF OFF ON ON
6 OFF ON ON ON
7 ON ON ON ON
8 ON ON ON OFF
1 ON ON OFF OFF The switching pattern set in the superconducting coil discharge control mode includes the following ON / OFF control of each switching element (the first to fourth switching elements are indicated as SW-1 to SW-4). 4. The superconducting coil power converter according to claim 3, wherein the power converter is repeated in order.
Rank SW-1 SW-2 SW-3 SW-4
1 ON ON OFF OFF
2 OFF ON OFF OFF
3 OFF OFF OFF OFF
4 OFF OFF ON OFF
5 OFF OFF ON ON
6 OFF OFF ON OFF
7 OFF OFF OFF OFF
8 OFF ON OFF OFF
1 ON ON OFF OFF The switching pattern set in the superconducting coil current compensation control mode includes the following ON / OFF control of each switching element (the first to fourth switching elements are indicated as SW-1 to SW-4). 4. The superconducting coil power converter according to claim 3, wherein the power converter is repeated in the following order.
Rank SW-1 SW-2 SW-3 SW-4
1 ON ON OFF OFF
2 ON ON ON OFF
3 OFF ON ON OFF
4 OFF ON ON ON
5 OFF OFF ON ON
6 OFF ON ON ON
7 OFF ON ON OFF
8 ON ON ON OFF
1 ON ON OFF OFF When shifting the control mode from the previous control mode to another control mode in accordance with the change in the voltage command value, the switching elements of each switching element are determined from the switching pattern order in which the output voltage in the control mode before the transition becomes zero. The superconducting coil power according to any one of claims 3 to 6, wherein an on / off state shifts to a switching pattern order in a transition destination control mode in which the on-off state of the switching pattern order before transition is the same. Conversion device.

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