JP5181712B2 - Multiple inverter system - Google Patents

Description

  The present invention relates to a transformer circuit having secondary windings insulated from each other, and each phase inverter formed by connecting in series multi-stages the output terminals of unit inverters that convert and output single-phase AC voltages of arbitrary frequency and voltage The present invention relates to a multiple inverter system including a three-phase inverter formed by three sets and a control device that controls the three-phase inverter.

  FIG. 4 shows the circuit configuration of this type of multiple inverter system. In this figure, as will be described later, reference numeral 10 denotes one or more having one secondary winding or a plurality of mutually isolated secondary windings. Transformer circuit composed of a single transformer, 11-13, 21-23, 31-33 are unit inverters, 40 or 50 is for controlling the unit inverters 11-13, 21-23, 31-33 to desired states, respectively. It is a control device.

  In the circuit configuration example shown in FIG. 4, one end of each output of the unit inverters 11, 21, and 31 is connected to each other, and each output end of the unit inverters 11 to 13 is connected in series in multiple stages to connect the U phase of the three-phase inverter. In addition, the output terminals of the unit inverters 21 to 23 are connected in series in multiple stages to form a V phase of the three-phase inverter, and the output terminals of the unit inverters 31 to 33 are connected in series in multiple stages to form a three-phase inverter. This forms the W phase of the inverter.

  Also, the transformer circuit 10 shown in FIG. 4 is composed of nine three-phase transformers having one set of secondary windings, and three-phase transformer 3 having three sets of mutually isolated secondary windings. A configuration with a stand, a configuration with one three-phase transformer having nine pairs of secondary windings insulated from each other, and the like are used.

  FIG. 5 is a circuit configuration diagram of each unit inverter shown in FIG. 4. As the rectifier circuit RC, a diode is connected in a three-phase bridge based on the manufacturing specifications of the multiple inverter system (hereinafter referred to as diode bridge rectification). Circuit), a thyristor connected in a three-phase bridge (hereinafter referred to as a thyristor bridge rectifier circuit), a self-extinguishing semiconductor element such as an IGBT and an anti-parallel circuit of a diode in a three-phase bridge connected (hereinafter referred to as PWM). (Referred to as a rectifier circuit). The capacitor C is used to make the output voltage of the rectifier circuit RC smoothed as a DC voltage, and the smoothed DC voltage (voltage value E) is used as IGBTs Q1 to Q4 as self-extinguishing semiconductor elements. And the switching operation of the inverter circuit formed by connecting the antiparallel circuit of the diodes D1 to D4 with a single-phase bridge connection converts it into a single-phase AC voltage having a desired frequency and voltage.

  In the conventional multiple inverter system including the transformer circuit 10, the unit inverters 11 to 13, 21 to 23, 31 to 33, and the control device 40, a desired three-phase AC voltage is supplied from the terminals U, V, and W to the load. As a first control method, the voltage across the capacitor C is made variable by using the thyristor bridge rectifier circuit in the rectifier circuit RC shown in FIG. 5, and this variable DC voltage is converted into unit inverters 11 to 13, 21 to 21. Each of 23, 31 to 33 is converted into a three-phase AC voltage having a desired voltage value as a three-phase inverter while being converted into a single-phase AC voltage having a desired frequency by a switching operation. (Also referred to as (pulse amplitude modulation) control).

Further, as a second control method, the diode bridge rectifier circuit or the PWM rectifier circuit is used for the rectifier circuit RC shown in FIG. 5, and each of the unit inverters 11 to 13, 21 to 23, 31 to 33 is operated as a PWM ( A three-phase inverter is converted into a three-phase AC voltage having a desired voltage value while being converted into a single-phase AC voltage having a desired frequency and voltage by a pulse width modulation) control operation. At this time, by using the PWM rectifier circuit, a higher DC voltage can be obtained as compared with the diode bridge rectifier circuit, and the power factor viewed from the transformer circuit 10 side is substantially “1.0”. Can be settled.
JP 11-122943 A

  In the conventional multiple inverter system using the transformer circuit 10, the unit inverters 11 to 13, 21 to 23, 31 to 33, and the control device 40 shown in FIG. 4, the rated voltage of the AC motor as a load of the multiple inverter system is There are cases where one of a plurality of different units is selected and used by switching each time.

  In such a case, in addition to the first and second control methods described above, the rated voltage of the connected AC motor is in the range of 1/3 to 2/3 of the output rated voltage of the multiple inverter system. As disclosed in Patent Document 1, the control device 40 outputs, for example, each of the unit inverters 11, 21, 31 to output a zero voltage and the unit inverters 12, 13, 22, 23, 32, 33. Each outputs a single-phase AC voltage having a desired frequency and voltage by a PAM control operation or a PWM control operation (hereinafter referred to as a third control method).

  Similarly, when the rated voltage of the connected AC motor is in the range of 1/3 or less of the output rated voltage of the multiple inverter system, the control device 40, for example, unit inverters 11, 12, 21, 22, Each of 31 and 32 outputs a zero voltage, and each of the unit inverters 13, 23 and 33 outputs a single-phase AC voltage having a desired frequency and voltage by a PAM control operation or a PWM control operation (hereinafter referred to as a fourth voltage). Is referred to as a control method).

  In the third or fourth control method, the unit inverter that outputs zero voltage is in the Q1, Q3 on state shown in FIG. 5 in the Q2, Q4 off state, and in the Q1, Q3 off state, the Q2, Q4 on state. Are alternately repeated while synchronizing with the output voltage polarity change of each phase inverter, or fixed to Q2, Q4 off state in Q1, Q3 on state or Q2, Q4 on state in Q1, Q3 off state By doing so, the purpose can be achieved.

  In the conventional multiple inverter system described above, in order to stop the normal operation using any one of the first to fourth control methods, the unit inverters 11 to 13, 21 to 23, 31 to 33 are respectively The pulse-off operation was performed all at once.

  With this simultaneous pulse-off operation, the maximum value between the output terminals U, V, and W of this multiplex inverter system is “the voltage across the capacitor C in each unit inverter (voltage value E) × series multiplex”. It is known that a voltage of “number of connections × 2 phases” is generated, and in the circuit configuration shown in FIG. 4, the voltage is “6E” volts.

  That is, using any one of the first to fourth control methods described above, even when the rated voltage of the AC motor as a load of the multiple inverter system is 2/3 or less of the output rated voltage of the multiple inverter system, As the simultaneous pulse-off operation is performed, a maximum voltage of “6E” volts may be applied between the primary windings of the AC motor. In the case of the third and fourth control methods, the unit inverter The DC voltage of the AC motor could not be lowered, and the maximum withstand voltage corresponding to the rated voltage of this AC motor (usually “4E” volts or less) could be exceeded.

  An object of the present invention is to provide a multiple inverter system capable of solving the above-mentioned problems.

According to the first aspect of the present invention, there is provided a transformer circuit comprising one or a plurality of transformers having one secondary winding or a plurality of mutually isolated secondary windings, and each of the secondary windings. Combine three sets of phase inverters that are configured by connecting the output terminals of unit inverters that convert the input AC voltage to single-phase AC voltage of any frequency and voltage and connect it in series with N ( N is an integer of 2 or more ) stages in series. a three-phase inverter formed Te, a multi-inverter system comprising a control unit for controlling the three-phase inverter to a desired state, controls the phase-phase inverter of the M (M <N) base unit inverters of Thus, when the multiple inverter system can output up to the rated voltage of the load with respect to the load of the multiple inverter system, the control device forms each phase inverter. In each unit inverter, at least one unit outputs a zero voltage, and the rest is in an operation state for outputting a single-phase AC voltage having a desired frequency and voltage,
When the three-phase inverter is outputting in this operating state and a pulse-off command is issued to the three-phase inverter, first, each unit inverter outputting the desired voltage is pulse-off by the control device, and this pulse-off operation is performed. In a multiple inverter system in which each of the unit inverters outputting the zero voltage is pulsed off by the control device after a predetermined time elapses from
The unit inverter that outputs the zero voltage is switched at predetermined intervals from among the N unit inverters of each phase.

According to a second aspect of the present invention, there is provided a transformer circuit including one or a plurality of transformers having one secondary winding or a plurality of mutually isolated secondary windings, and each of the secondary windings. Combining three sets of phase inverters configured by connecting the output terminals of unit inverters that convert input AC voltage into single-phase AC voltage of any frequency and voltage and output it in series (N is an integer of 2 or more). A multiple inverter system comprising a formed three-phase inverter and a control device that controls the three-phase inverter to a desired state, and controls M (M <N) unit inverters of the phase inverter of each phase. Thus, when the multiple inverter system can output up to the rated voltage of the load with respect to the load of the multiple inverter system, the control device forms each phase inverter. At least one of each unit inverter outputs a zero voltage, and the rest is in an operation state of outputting a single-phase AC voltage having a desired frequency and voltage,
When the three-phase inverter is outputting in this operating state and a pulse-off command is issued to the three-phase inverter, first, each unit inverter outputting the desired voltage is pulsed off by the control device, and this pulse-off operation is performed. In a multiple inverter system in which each of the unit inverters outputting the zero voltage is pulsed off by the control device after a predetermined time elapses from
The unit inverter that outputs the zero voltage is selected in advance from among the N unit inverters of each phase .

According to a third aspect of the present invention, there is provided a transformer circuit composed of one or a plurality of transformers having one secondary winding or a plurality of mutually isolated secondary windings, and from each of the secondary windings Each unit inverter that converts the input AC voltage into a single-phase AC voltage having an arbitrary frequency and voltage and outputs it is connected in series N ( N is a positive number of 2 or more ) stages, and each set of three phase inverters a three-phase inverter formed by a multiple inverter system comprising a control unit for controlling the three-phase inverter to a desired state, controls the phase-phase inverter of the M (M <N) base unit inverters of Thus, when the multiple inverter system can output up to the rated voltage of the load with respect to the load of the multiple inverter system, the control device forms the respective phase inverters. At least one of each unit inverter outputs a zero voltage, and the rest is in an operation state of outputting a single-phase AC voltage having a desired frequency and voltage,
When the three-phase inverter is outputting in this operating state and a pulse-off command is issued to the three-phase inverter, first, each unit inverter outputting the desired voltage is pulse-off by the control device, and this pulse-off operation is performed. In a multiple inverter system that monitors the output current of the subsequent three-phase inverter and pulse-offs each unit inverter that is outputting the zero voltage by the control device when the output current becomes a predetermined value or less ,
The unit inverter that outputs the zero voltage is switched at predetermined intervals from among the N unit inverters of each phase .

Furthermore, the fourth invention provides a transformer circuit composed of one or a plurality of transformers having one secondary winding or a plurality of mutually isolated secondary windings, and each of the secondary windings. Each phase inverter 3 is formed by connecting the output terminals of the unit inverters that convert the input AC voltage from a single-phase AC voltage of an arbitrary frequency and voltage and output it in series N (N is a positive number of 2 or more) stages. A multi-inverter system comprising a three-phase inverter formed by a set and a control device for controlling the three-phase inverter to a desired state, wherein M (M <N) unit inverters of the phase inverter of each phase When the multi-inverter system can output up to the rated voltage of the load with respect to the load of the multi-inverter system, the control device forms each phase inverter. At least one of the unit inverters that are configured outputs zero voltage, and the rest is in an operation state that outputs a single-phase AC voltage having a desired frequency and voltage.
When the three-phase inverter is outputting in this operating state and a pulse-off command is issued to the three-phase inverter, first, each unit inverter outputting the desired voltage is pulse-off by the control device, and this pulse-off operation is performed. In a multiple inverter system that monitors the output current of the subsequent three-phase inverter and pulse-offs each unit inverter that is outputting the zero voltage by the control device when the output current becomes a predetermined value or less,
The unit inverter that outputs the zero voltage is selected in advance from among the N unit inverters of each phase .

  In the present invention, the voltage generated between the output terminals of the multiple inverter system at the time of pulse-off of each unit inverter after normal operation is mainly due to the inductance of the load of the multiple inverter system and the freewheel diode (FWD) operation of the unit inverter. Therefore, it was made by paying attention to the fact that a voltage is generated between the output terminals in a short time from the pulse-off until the current decays to zero.

  That is, when a pulse-off command is issued to the multiple inverter system during normal operation using the third or fourth control method, the unit inverter that is outputting a desired voltage first. When the predetermined time elapses after the pulse-off operation or when the output current of the multiple inverter system becomes a predetermined value or less, each unit inverter that is outputting zero voltage is pulsed off. It is eliminated that a voltage that may exceed the maximum withstand voltage is applied to the load, and as a result, damage to the load can be prevented.

  As a first embodiment of the present invention, an AC motor as a load of a multiple inverter system by the transformer circuit 10, the unit inverters 11 to 13, 21 to 23, 31 to 33, and the control device 50 shown in FIG. One of a plurality of units having different voltages is used by switching each time, and the rated voltage of the AC motor connected with the switching is 1/3 to 2/3 of the output rated voltage of the multiple inverter system. The case of being in the range will be described below with reference to the operation flowchart of the control device 50 shown in FIG.

  First, as a normal operation state in step S11, the control device 50 outputs, for example, each of the unit inverters 11, 21, 31 outputs zero voltage, and each of the unit inverters 12, 13, 22, 23, 32, 33 performs PWM control. A single-phase AC voltage having a desired frequency and voltage is output by operation, that is, whether or not a pulse-off command is issued during the state in which the third control method described above is being performed (step S12). When the pulse-off command is not issued (branch N), the process returns to step 11.

  When it is detected in step 12 that a pulse-off command has been issued (branch Y), the process proceeds to step 13.

  In step S13, each of unit inverters 12, 13, 22, 23, 32, and 33 shifts to a pulse-off state while each of unit inverters 11, 21, and 31 outputs a zero voltage.

  As a result, a voltage of “4E” volts is generated as a maximum value between any of the output terminals U, V, and W of this multiple inverter system, and this voltage attenuates with the passage of time as described above.

  That is, in step S14, a time T1 until the voltage generated by the process in step S13 is sufficiently attenuated is set, wait until this time elapses (branch N), and when this time T1 elapses (branch Y), Control goes to step S15.

  In step S15, each of the unit inverters 11, 21, 31 that has output the zero voltage is shifted to the pulse-off state.

  Therefore, in the multiple inverter system of the present invention, the voltage “6E” generated due to the pulse-off operations of the unit inverters 11 to 13, 21 to 23, 31 to 33 in the conventional multiple inverter system being performed all at once. "Bolts can be constrained to" 4E "bolts. That is, a voltage that may exceed the maximum withstand voltage of the load is eliminated from being applied to the load, and as a result, damage to the load can be prevented.

  FIG. 2 is a circuit configuration diagram of a multiple inverter system showing a second embodiment of the present invention. The difference from the circuit configuration shown in FIG. 4 is that a control device 60 is provided instead of the control device 50. A current detector 61 for detecting the output current of the multiple inverter system is added.

  The AC motor as a load of the multiple inverter system shown in FIG. 2 is used by switching one of a plurality of units having different rated voltages each time, and the rated voltage of the AC motor connected with the switching is changed. The case where the output voltage is within 1/3 of the rated output voltage of the multiple inverter system will be described below with reference to the operation flowchart of the control device 60 shown in FIG.

  First, as a state of normal operation in step S21, for example, the unit inverters 11, 12, 21, 22, 31, and 32 output zero voltage by the control device 60, and the unit inverters 13, 23, and 33 each perform PWM control. A single-phase AC voltage having a desired frequency and voltage is output by operation, that is, whether or not a pulse-off command is issued during the state in which the above-described fourth control method is performed is monitored (step S22). When the pulse-off command is not issued (branch N), the process returns to step 21.

  When it is detected in step 22 that a pulse-off command has been issued (branch Y), the process proceeds to step 23.

  In step S23, each of the unit inverters 13, 23, and 33 shifts to a pulse-off state while the unit inverters 11, 12, 21, 22, 31, and 32 output zero voltage.

  As a result, a voltage of “2E” volts is generated as a maximum value between any of the output terminals U, V, and W of this multiple inverter system, and this voltage attenuates as time passes as described above.

  That is, in step S24, the voltage generated by the process of step S23 is sufficiently attenuated, and as a result, the detection value of the current detector 61 is also decreased (branch N). This detection value is zero or a predetermined value. Hereinafter, for example, when it becomes 1% or less of the rating (branch Y), the process proceeds to step S25.

  In step S25, the unit inverters 11, 12, 21, 22, 31, and 32 that have output the zero voltage are shifted to the pulse-off state.

  Therefore, in the multiple inverter system of the present invention, the voltage “6E” generated due to the pulse-off operations of the unit inverters 11 to 13, 21 to 23, 31 to 33 in the conventional multiple inverter system being performed all at once. "Bolts can be constrained to" 2E "bolts. That is, a voltage that may exceed the maximum withstand voltage of the load is eliminated from being applied to the load, and as a result, damage to the load can be prevented.

  Furthermore, according to the multiple inverter system using the first or second embodiment of the present invention, the AC motor as the load of the multiple inverter system selects one of the multiple units having different rated voltages. However, it is advantageous in terms of price, installation area, etc., since it can be used with a single multi-inverter system for applications that are switched and used each time.

  In the above description of the first or second embodiment, the unit inverter that outputs a single-phase AC voltage having a desired frequency and voltage is fixed, but each phase 3 (N = 3) is described. ) By making it possible to arbitrarily select from the unit inverters of each unit and repeating this selection operation every predetermined time, the heat loss of each unit inverter can be averaged. As a result, each unit inverter The temperature rise value can be made uniform.

Operational flow chart showing the first embodiment of the present invention Circuit diagram of a multiple inverter system showing a second embodiment of the present invention Flowchart for explaining the operation of FIG. Circuit diagram of multiple inverter system Circuit diagram of unit inverter

DESCRIPTION OF SYMBOLS 10 ... Transformer circuit, 11-13, 21-23, 31-33 ... Unit inverter, 40, 50, 60 ... Control apparatus, 61 ... Current detector.

Claims (4)

Transformer circuit composed of one or a plurality of transformers having one secondary winding or a plurality of mutually isolated secondary windings, and an input AC voltage from each of the secondary windings is arbitrarily set three-phase output terminal of the unit of inverter outputs the converted single-phase AC voltage of a frequency and voltage series N (N is an integer greater than or equal to 2) formed by combining three sets phase inverter constituted by connecting stages an inverter, by a multi-inverter system comprising a control unit for controlling the three-phase inverter to a desired state, and controls the phase-phase inverter of the M (M <N) base unit inverters of the When the multiple inverter system can output up to the rated voltage of the load with respect to the load of the multiple inverter system, each unit inverter forming each phase inverter by the control device. At least one of the inverters outputs a zero voltage, and the rest is in an operation state of outputting a single-phase AC voltage having a desired frequency and voltage,
When the three-phase inverter is outputting in this operating state and a pulse-off command is issued to the three-phase inverter, first, each unit inverter outputting the desired voltage is pulse-off by the control device, and this pulse-off operation is performed. In a multiple inverter system in which each of the unit inverters outputting the zero voltage is pulsed off by the control device after a predetermined time elapses from
The multiple inverter system , wherein the unit inverter that outputs the zero voltage is switched at predetermined intervals from among the N unit inverters of each phase . Transformer circuit composed of one or a plurality of transformers having one secondary winding or a plurality of mutually isolated secondary windings, and an input AC voltage from each of the secondary windings is arbitrarily set A three-phase inverter formed by combining three sets of phase inverters configured by connecting the output terminals of unit inverters that convert to a single-phase AC voltage of frequency and voltage and output in series N (N is an integer of 2 or more) stages; A multiple inverter system comprising a control device for controlling the three-phase inverter to a desired state, wherein the multiple inverter is controlled by controlling M (M <N) unit inverters of the phase inverter of each phase. When the multiple inverter system can output up to the rated voltage of the load with respect to the load of the system, each unit inverter forming each phase inverter by the control device. Among converter, at least one outputs a zero voltage, the remainder to the operating state of outputting the single-phase AC voltage of desired frequency and voltage,
  When the three-phase inverter is outputting in this operating state and a pulse-off command is issued to the three-phase inverter, first, each unit inverter outputting the desired voltage is pulse-off by the control device, and this pulse-off operation is performed. In a multiple inverter system in which each of the unit inverters outputting the zero voltage is pulsed off by the control device after a predetermined time elapses from
  A multiple inverter system, wherein the unit inverter for outputting the zero voltage is selected in advance from among the N unit inverters for each phase. Transformer circuit composed of one or a plurality of transformers having one secondary winding or a plurality of mutually isolated secondary windings, and an input AC voltage from each of the secondary windings is arbitrarily set A three-phase inverter formed by three sets of inverters each having a series N ( N is a positive number of 2 or more ) stages connected to the output terminals of each unit inverter that converts the frequency and voltage into a single-phase AC voltage and outputs it And a control device for controlling the three-phase inverter to a desired state , wherein the multiple inverter system is controlled by controlling M (M <N) unit inverters of the phase inverter of each phase. When the multiple inverter system can output up to the rated voltage of the load with respect to the load of the inverter system, each unit inverter forming each phase inverter by the control device. At least one of the inverters outputs a zero voltage, and the rest is in an operation state of outputting a single-phase AC voltage having a desired frequency and voltage,
When the three-phase inverter is outputting in this operating state and a pulse-off command is issued to the three-phase inverter, first, each unit inverter outputting the desired voltage is pulse-off by the control device, and this pulse-off operation is performed. In a multiple inverter system that monitors the output current of the subsequent three-phase inverter and pulse-offs each unit inverter that is outputting the zero voltage by the control device when the output current becomes a predetermined value or less ,
The multiple inverter system , wherein the unit inverter that outputs the zero voltage is switched at predetermined intervals from among the N unit inverters of each phase . Transformer circuit composed of one or a plurality of transformers having one secondary winding or a plurality of mutually isolated secondary windings, and an input AC voltage from each of the secondary windings is arbitrarily set Three-phase inverter formed by three sets of each phase inverter formed by connecting the output terminals of each unit inverter to be converted into a single-phase AC voltage of frequency and voltage in series N (N is a positive number of 2 or more) stages And a control device for controlling the three-phase inverter to a desired state, wherein the multiple inverter system is controlled by controlling M (M <N) unit inverters of the phase inverter of each phase. When the multiple inverter system can output up to the rated voltage of the load with respect to the load of the inverter system, each unit inverter forming each phase inverter by the control device. Among converter, at least one outputs a zero voltage, the remainder to the operating state of outputting the single-phase AC voltage of desired frequency and voltage,
  When the three-phase inverter is outputting in this operating state and a pulse-off command is issued to the three-phase inverter, first, each unit inverter outputting the desired voltage is pulse-off by the control device, and this pulse-off operation is performed. In a multiple inverter system that monitors the output current of the subsequent three-phase inverter and pulse-offs each unit inverter that is outputting the zero voltage by the control device when the output current becomes a predetermined value or less,
  A multiple inverter system, wherein the unit inverter for outputting the zero voltage is selected in advance from among the N unit inverters for each phase.

Images