Patent Document

TECHNICAL FIELD 
     The present invention relates to a calculation method of input/output power at the time of drive/regenerative mode, in a power-electronics product which includes a chopper circuit and which is configured, for example, to perform a motor control. 
     BACKGROUND ART 
     For example, each of Non Patent Literature 1 and Patent Literatures 1 and 2 has proposed a motor drive device, as a device for supplying electric power of a direct-current power source to a load and for regenerating electric power of the load into the direct-current power source by using a chopper circuit. 
     CITATION LIST 
     Non Patent Literature 
     
         
         Non Patent Literature 1: “220000 r/min-2 kW PM Motor Drive System for Turbocharger” in Journal-D of the Institute of Electrical Engineers of Japan, Vol. 125 (2005), No. 9, pp. 854-861 
       
    
     Patent Literature 
     
         
         Patent Literature 1: Japanese Patent No. 3278188 
         Patent Literature 2: Japanese Patent Application Publication No. 2008-295280 
       
    
       FIG. 3  shows one example of a motor drive device equipped with a direct-current power source, a chopper circuit and an inverter. 
     In  FIG. 3 , a reference sign  10  denotes a battery, and a reference sign C 1  denotes a condenser. The condenser C 1  is connected with the battery  10  to be in parallel with the battery  10 . A reference sign  11  denotes a switching element connected through a reactor L 1  with the battery  10  to be in parallel with the battery  10 . A reference sign  12  denotes a switching element connected with the switching element  11  to be in series with the switching element  11 . 
     The switching element  11  is connected with a free-wheel diode (bypass diode)  13  to be in antiparallel (inverse-parallel) with the free-wheel diode  13 . The switching element  12  is connected with a free-wheel diode (bypass diode)  14  to be in antiparallel with the free-wheel diode  14 . A series combination of the switching elements  11  and  12  is connected with a condenser C 2  to be in parallel with the condenser C 2 . The condenser C 2  is connected with a series combination formed by connecting the switching elements  15  and  16  in series. The condenser C 2  is in parallel with this series combination of the switching elements  15  and  16 . The switching element  15  is connected with a free-wheel diode (bypass diode)  17  to be in antiparallel with the free-wheel diode  17 . The switching element  16  is connected with a free-wheel diode (bypass diode)  18  to be in antiparallel with the free-wheel diode  18 . 
     One end of a reactor L 2  is connected with a common connection point of the switching elements  15  and  16 . An inverter  19  having a three-phase bridge configuration is disposed between another end of the reactor L 2  and a negative-pole terminal of the battery  10 , and is connected with the another end of the reactor L 2  and the negative-pole terminal of the battery  10 . Three-phase output of the inverter  19  is supplied to a PM motor  20 . 
     A common connection point of the inverter  19  and the reactor L 2  is connected through anode and cathode of a diode D 1  with a common connection point (=point P) of the switching element  12  and the condenser C 2 . 
     The inverter  19  is a 120-degree-conduction current-source inverter. The inverter  19  is constituted by switching elements and free-wheel diodes (bypass diodes). The switching elements of the inverter  19  are connected with one another in the form of three-phase bridge. Each of the free-wheel diodes of the inverter  19  is connected with the corresponding switching element of the inverter  19  to be in antiparallel with this switching element. 
     A gate-drive circuit of the inverter  19 , a detector for sensing a voltage Vdc of the point P and a detector for sensing a current Idc flowing in the reactor L 2  are omitted from the depiction of Figures. 
     Operations of the device configured as above will now be explained. At first, at the time of drive mode, the switching element  11  is turned on (opened), so that electric current is applied to the reactor L 1  by a direct-current voltage which is derived from the battery  10  and which is smoothed by the condenser C 1 . Thereby, energy is stored in the reactor L 1 . Then, the switching element  11  is turned off (closed), so that the energy stored in the reactor L 1  is charged through the free-wheel diode  14  into the condenser C 2 . Thereby, a voltage of the condenser C 2  is increased. 
     By virtue of such a structure, the charging of condenser C 2  is possible even if a voltage on the side of condenser C 2  is high. Accordingly, the reactor L 1 , the switching element  11 , the diode  14  and the condenser C 2  constitute a first boost chopper circuit. At this time, the switching element  11  is repeatedly turned on and off in order to maintain the voltage Vdc of the condenser C 2  at a constant level. By varying a target value of this voltage control or regulation (AVR) of the condenser C 2 , a loss reduction becomes possible. 
     Moreover, when the switching element  15  is turned on, electric current is applied to the reactor L 2  so that energy is stored in the reactor L 2 . In this case, the drive is impossible unless the voltage Vdc of the side of condenser C 2  is higher than a voltage of the side of the reactor L 2 . Next, when the switching element  15  is turned off and the switching element  16  is turned on, a constant current flows through the switching element  16  and any two now-conducting switching elements of the inverter  19  into the reactor L 2  by means of the energy stored in the reactor L 2 . This electric current is detected by the not-shown current detector. Alternatively, a rotational speed of the PM motor  20  is detected or estimated from a waveform based on gate signals. So as to bring this electric current or rotational speed to its target value, an on/off control of the switching elements  15  and  16  is performed so that a current control (ACR) or a speed control (ASR) is performed. Moreover, by using the on/off control of the switching elements  15  and  16 , the motor  20  can be rotated by a voltage level lower than the battery voltage. 
     Next, operations at the time of regenerative mode will now be explained. At the time of regeneration, the PM motor  20  generates an induced voltage proportional to its rotational speed. If the induced voltage of motor becomes higher than the voltage of the side of reactor L 2 , electric current can be applied through any of the not-shown free-wheel diodes of the inverter  19  to the side of reactor L 2 . When the switching element  16  is turned on, the electric current flows in the reactor L 2  so that energy is stored in the reactor L 2 . Then, when the switching element  16  is turned off, electric current flows through the diode  17  by the energy of the reactor L 2  at first. Next, the switching element  15  is turned on after a dead time has elapsed. Thereby, electric current flows through the switching element  15  and is charged into the condenser C 2 , so that the voltage of the condenser C 2  is increased. 
     By virtue of such a structure, the charging of condenser C 2  is possible even if the induced voltage of the PM motor  20  is low. Accordingly, the switching elements  15  and  16 , the reactor L 2  and the condenser C 2  constitute a second boost chopper circuit. In this second boost chopper section, a current control (ACR) for maintaining electric current at a constant level, a speed control (ASR) of the PM motor  20 , or a power control (APR) for maintaining electric power at a constant level is performed. At this time, electric power is returned to the battery  10  by an increased amount of voltage of the condenser C 2  which is caused by a regeneration power derived from the second boost chopper circuit. 
     As a concrete procedure of retuning electric power to the battery  10 , the switching element  12  is turned on to apply electric current to the reactor L 1 . Thereby, the reactor L 1  stores energy. Then, the switching element  12  is turned off, so that electric current is applied through the free-wheel diode  13  to the reactor L 1  by the energy of the reactor L 1 . 
     Additionally, the positive-side voltage of the inverter  19  is introduced through the diode D 1  to the point P of the condenser C 2  as a bypass when a gate of the inverter  19  is shut off. Hence, a voltage rise of the inverter  19  can be suppressed. Therefore, damage of the respective switching elements constituting the inverter  19  can be prevented. 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     As mentioned above, in the device of  FIG. 3 , the voltage control for the voltage Vdc of the point P and the current control for the current Idc flowing in the reactor L 2  are performed. Hence, the voltage Vdc and the current Idc are already known. 
     However, a value of an electric current flowing in the point P (=a region to which the voltage Vdc is applied, i.e., a region producing the voltage Vdc) corresponding to an input portion of direct-current power is unknown. Also, a value of a voltage applied between the negative-pole terminal of the battery  10  and the common connection point of the inverter  19  and the reactor L 2  (=a region in which the current Idc flows) is unknown. The common connection point of the reactor L 2  and the inverter  19  corresponds to an output portion of the direct-current power. Therefore, an input/output electric power value cannot be calculated. 
     Therefore, in a case that an output power control or a regenerative power control is performed, in order to control precisely, it has been necessary to measure the electric power value by providing an electric-current detector at the region having the voltage Vdc or providing a voltage detector at the region having the current Idc. 
     The present invention solves the above problem. It is an object of the present invention to provide an electrical power control device or an electrical power calculation method in an electrical power control device, devised to calculate the input/output electrical power value without using a current detector of the input portion or a voltage detector of the output portion. 
     Solution to Problem 
     An electrical power control device comprises: a direct-current power source; a chopper circuit including a first switching element whose one end is connected with a positive-pole terminal side of the direct-current power source, a second switching element whose one end is connected with a negative-pole terminal side of the direct-current power source, wherein the first switching element and the second switching element are provided between the positive-pole terminal and the negative-pole terminal of the direct-current power source in series with the direct-current power source, and a reactor whose one end is connected with a common connection point located between another end of the first switching element and another end of the second switching element; and a load connected between another end of the reactor and the negative-pole terminal of the direct-current power source. This electrical power control device is configured to supply direct-current power of the direct-current power source to the load and is configured to regenerate the direct-current power source with direct-current power of the load by controlling the chopper circuit. In such an electrical power control device, an output voltage Vdc of the direct-current power source, a current Idc flowing in the reactor, a switching duty d 1  of the first switching element of the chopper circuit, a switching duty d 2  of the second switching element of the chopper circuit, and a dead time DT between the first switching element and the second switching element are known when a normal voltage control and/or current control is carried out. At this time, the switching duty d 1  satisfies a condition of 0≦d 1 ≦1, the switching duty d 2  satisfies a condition of 0≦d 2 ≦1, and the dead time DT satisfies a condition of 0≦DT≦1. Moreover, a relation of 1=d 1 +d 2 +DT is satisfied. 
     Therefore, according to the present invention, an electrical power W is determined (obtained) in the following manner by use of these known values Vdc, Idc, d 1 , d 2  and DT. 
     That is, 
     (1) In a case that only a drive of load is performed and also that the switching duty d 1  is known, the electrical power W is determined by calculating a following formula (1)
 
 W=Vdc·d   1   ·Idc   (1)
 
     (2) In a case that only a power regeneration from load is performed and also that the switching duty d 2  is known, the electrical power W is determined by calculating a following formula (2).
 
 W=Vdc ·(1− d   2 )· Idc   (2)
 
     (3) In a case that the drive of load is performed and also that the switching duty d 2  is known, the electrical power W is determined by calculating a following formula (3)
 
 W=Vdc ·(1− d   2   −DT )· Idc   (3)
 
     (4) In a case that electrical power is regenerated from load and also that the switching duty d 1  is known, the electrical power W is determined by calculating a following formula (4).
 
 W=Vdc ·( d   1   +DT )· Idc   (4)
 
     (5) In a case that the drive of load and the regeneration from load are performed and also that the switching duty d 1  and the switching duty d 2  are known, the electrical power W is determined by calculating any one of the above formulas (1) to (4). 
     (6) Furthermore, an internal loss by the chopper circuit is calculated, and thereby, an electrical-power rate (ratio) n between input and output of the chopper circuit is obtained based on the internal loss. Then, from the electrical-power rate n and the electrical power W obtained by one of the above formulas (1) to (4); an electrical power W′ adjusted in consideration of an equipment efficiency is determined by calculating a following formula (5).
 
 W′=n·W   (5)
 
     According to the above structures, an electrical-power value can be calculated without providing a current detector for detecting electric current flowing in the direct-current power source (the region to which the voltage Vdc is applied) and a voltage detector for detecting voltage applied to the another end of the reactor (voltage of the region in which the current Idc flows). 
     Advantageous Effects of Invention 
     (1) According to the inventions, an electrical-power value can be calculated without providing a current detector for detecting electric current flowing in the direct-current power source and without providing a voltage detector for detecting voltage applied to the another end of the reactor. 
     (2) Moreover, by using the calculated electrical-power value, a drive (power-running) power control or a regenerative power control can be accurately attained without providing the current detector or the voltage detector. 
    
    
     
       BRIEF EXPLANATION OF DRAWINGS 
         FIG. 1  A configuration view of an electrical power control device to which the present invention is applied. 
         FIG. 2  A main circuit diagram showing seventh to ninth examples according to the present invention. 
         FIG. 3  A circuit diagram showing one example of a motor drive device to which the present invention is applied. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments according to the present invention will be explained referring to the drawings. However, the present invention is not limited to examples of the following embodiments.  FIG. 1  shows a configuration of an electrical power control device to which the present invention is applied. A reference sign  1  denotes a direct-current power source (DC power source), for example, constituted by a circuit ranging from the point P (to which the voltage Vdc is applied) to the battery  10 , i.e., constituted by the battery  10 , the condensers C 1  and C 2 , the reactor L 1 , the switching elements  11  and  12 , and the free-wheel diodes  13  and  14  in  FIG. 3 . 
     This direct-current power source  1  according to the present invention is not limited to the circuit shown by  FIG. 3 , and may be a direct-current power source having a thyristor-rectifier bridge circuit or a battery having the voltage value Vdc. 
     A reference sign  2  denotes a chopper circuit, for example, including the switching elements  15  and  16 , the free-wheel diodes  17  and  18  and the reactor L 2  in  FIG. 3 . 
     A reference sign  3  denotes a control section including a function for calculating an electric power W. For example, this function of the control section  3  calculates the electric power W by using the above formulas (1) to (4) on the basis of the voltage Vdc of point P of  FIG. 3 , the electric current Idc flowing in the reactor L 2 , a switching duty d 1  of a first switching element (the switching element  15  of  FIG. 3 ) of the chopper circuit  2 , a switching duty d 2  of a second switching element (the switching element  16  of  FIG. 3 ) of the chopper circuit  2 , and the dead time DT between the first switching element and the second switching element. The switching duty d 1  satisfies a condition of 0≦d 1 ≦1. The switching duty d 2  satisfies a condition of 0≦d 2 ≦1. The dead time DT satisfies a condition of 0≦DT≦1. 
     Moreover, the control section  3  includes a function for calculating an electric power W′ adjusted by taking the equipment efficiency into consideration. This function of the control section  3  calculates the electric power W′, by calculating an internal loss of the chopper circuit  2  and calculating the above formula (5) from the electric power W and a power ratio (rate) n of input and output of chopper circuit based on the internal loss. 
     Moreover, the control section  3  includes a function for performing a control for supplying direct-current power of the direct-current power source  1  to the direct-current load  4  and a (regenerative) control for returning direct-current power of the direct-current load  4  to the direct-current power source  1  by controlling the chopper circuit  2 . 
     The direct-current load  4 , for example in  FIG. 3 , includes the inverter  19  for converting direct-current power into alternating-current power, and the PM motor  20  connected with an alternating-current side of the inverter  19 . 
     The voltage Vdc, the current Idc, the switching duty (duty time) d 1 , the switching duty (duty time) d 2  and the dead time DT are known (1=d 1 +d 2 +DT) under the normal voltage control or current control. Means for detecting these values are omitted from the depiction of  FIG. 1 . 
     Next, concrete examples will now be explained in each of which the present invention is applied to the motor drive device of  FIG. 3 . In the following examples, operations of the switching elements  11 ,  12 ,  15  and  16  at the time of drive mode of the PM motor  20  and at the time of regenerative mode of electric power of the PM motor  20  are basically as mentioned above. 
     First Example 
     In a first example, the present invention is applied to a case where only the drive of the PM motor  20  is performed in the circuit of  FIG. 3  and where the switching duty d 1  of the switching element  15  is known. It is noted that the switching duty d 1  is represented by duty=A/B, wherein A denotes a turn-on time of the switching element and wherein B denotes one period of ON-OFF operation. 
     At this time, the switching elements  16  and  12  whose on-off controls are performed during the regenerative motion are unnecessary. Hence, the combination of the switching element  16  and the diode  18  may be replaced with only the diode  18 , and the combination of the switching element  12  and the diode  14  may be replaced with only the diode  14 . 
     A value of the current flowing in the point P (=the region to which the voltage Vdc is applied) of  FIG. 3  is equal to d 1 ·Idc. Accordingly, the control section  3  of  FIG. 1  calculates the value of electric power W by the following formula (1).
 
 W=Vdc·d   1   ·Idc   (1)
 
     Second Example 
     In a second example, the present invention is applied to a case where only the regeneration of electric power of the PM motor  20  (regenerative mode by the PM motor  20 ) is performed in the circuit of  FIG. 3  and where the switching duty d 2  of the switching element  16  is known. 
     At this time, the switching elements  15  and  11  whose on-off controls are performed during the drive motion are unnecessary. Hence, the combination of the switching element  15  and the diode  17  may be replaced with only the diode  17 , and the combination of the switching element  11  and the diode  13  may be replaced with only the diode  13 . 
     During the regeneration of electric power, a regeneration current flows through the switching element  15  or the diode  17  into the point P (the region to which the voltage Vdc is applied) when the switching element  16  is in OFF state. Accordingly, a value of this regeneration current is equal to a product (multiplication) of the current Idc and a turn-off time (1−d 2 ) of the switching element  16 . 
     Therefore, the control section  3  of  FIG. 1  calculates the value of electric power W by the following formula (2).
 
 W=Vdc ·(1 −d   2 )· Idc   (2)
 
     Third Example 
     In a third example, the present invention is applied to a case where the drive of the PM motor  20  is performed in the circuit of  FIG. 3  and where the switching duty d 2  of the switching element  16  is known. 
     During the drive of the PM motor  20 , electric current flows from the point P when the switching element  15  is in ON state. This turn-on time of the switching element  15  is represented by (1−d 2 −DT) using the turn-off time (1−d 2 ) of the switching element  16  and the dead time DT. Accordingly, a value of the current flowing in the point P is equal to (1−d 2 −DT)·Idc. Therefore, the control section  3  of  FIG. 1  calculates the value of electric power W by the following formula (3).
 
 W=Vdc ·(1− d   2   −DT )· Idc   (3)
 
     Fourth Example 
     In a fourth example, the present invention is applied to a case where the regeneration of electric power of the PM motor  20  is performed in the circuit of  FIG. 3  and where the switching duty d 1  of the switching element  15  is known. 
     During the electric-power regeneration, regenerative current flows in the point P through the switching element  15  turned on when the switching element  16  is in OFF state. This turn-off time of the switching element  16  is represented by a sum (d 1 +DT) of the switching duty d 1  of the switching element  15  and the dead time DT. Accordingly, a value of the regenerative current flowing in the point P is equal to a product (multiplication) of the current Idc and the turn-off time (d 1 +DT) of the switching element  16 . 
     Therefore, the control section  3  of  FIG. 1  calculates the value of electric power W by the following formula (4).
 
 W=Vdc ·( d   1   +DT )· Idc   (4)
 
     Fifth Example 
     In a fifth example, the present invention is applied to a case where the drive and the electric-power regeneration of the PM motor  20  are performed in the circuit of  FIG. 3  and where the switching duty d 1  of the switching element  15  and the switching duty d 2  of the switching element  16  are known. 
     The control section  3  of  FIG. 1  calculates the value of electric power W by one of the above formulas (1) to (4) of the first to fourth examples. 
     Sixth Example 
     The value of electric power which is calculated in the first to fifth examples is the electric-power value of the point P (the region to which the voltage Vdc is applied) of  FIG. 3 . Hence, in a case of actual equipment (device), this electric-power value of the point P deviates from an electric-power value of input/output portion of the chopper circuit due to an internal loss. Therefore, in this example, the internal loss is calculated. In the case that a rate of electric power of the input/output portion relative to the point P of  FIG. 3  is known as n, an accurate electric power W′ of the input/output portion can be obtained by calculating the following formula (5) using the electric power W calculated in the first to fifth examples.
 
 W′=n·W   (5)
 
     It is noted that an efficiency η of the equipment can be used as this rate n. 
     Seventh Example 
     In a seventh example, a power control or power regulation (APR) including a control loop as shown in  FIG. 2  is applied to the switching elements  15  and  16  of  FIG. 3  which have performed the current control (ACR) beforehand, on the basis of the electric-power value W (W′) calculated in the first to sixth examples. Thereby, the power-running (driving) control and the power-regenerating control can be attained without providing additional current/voltage detector. 
       FIG. 2  extracts a part from  FIG. 3 , and shows components same as those of  FIG. 3  with same reference signs. In  FIG. 2 , a reference sign  30  denotes an electric-power control section for performing the power control (APR) on the basis of an electric-power command value W cmd  and the electric-power value W (W′) calculated in the first to sixth examples. 
     A reference sign  40  denotes an electric-current control section for performing the current control (ACR) on the basis of an electric-current command value Idc cmd  and the electric-current detection value Idc. 
     Eighth Example 
     An eighth example is done under the same case as the third example (i.e., under the case where the drive is performed in  FIG. 3  and where only the switching duty d 2  of the switching element  16  is known) and also under the case of the seventh example. In the eighth example, the dead time DT of the above formula (3) is ignored. That is, the electric-power value W which is a control target is calculated by a following formula (6).
 
 W=Vdc ·(1 −d   2 )· Idc   (6)
 
     In this case, an error in the control is caused by an influence of the dead time. Therefore, the electric-power command value W cmd  is modified into W′ cmd  as shown by a following formula (7). Accordingly, the output electric-power control can be accurately performed because a correction depending on the dead time is added.
 
 W′   cmd   =W   cmd   +DT·Vdc·Idc   (7)
 
     Ninth Example 
     A ninth example is done under the same case as the fourth example (i.e., under the case where the regeneration is performed in  FIG. 3  and where only the switching duty d 1  of the switching element  15  is known) and also under the case of the seventh example. In the ninth example, the dead time DT of the above formula (4) is ignored. That is, the electric-power value W which is a control target is calculated by a following formula (8).
 
 W=Vdc·d   1   ·Idc   (8)
 
     In this case, an error in the control is caused by an influence of the dead time. Therefore, the electric-power command value W cmd  is modified into W′ cmd  as shown by a following formula (9). Accordingly, the output electric-power control can be accurately performed because a correction depending on the dead time is added.
 
 W′   cmd   =W   cmd   −DT·Vdc·Idc   (9)
 
     LIST OF REFERENCE SIGNS 
     
         
         
           
               1 —Direct-current power source 
               2 —Chopper circuit 
               3 —Control section 
               4 —Direct-current load 
               10 —Battery 
               11 ,  12 ,  15 ,  16 —Switching element 
               13 ,  14 ,  17 ,  18 —Free-wheel diode 
               19 —Inverter 
               20 —PM motor 
               30 —Electric power control section 
               40 —Electric current control section 
             C 1 , C 2 —Condenser 
             L 1 , L 2 —Reactor 
             D 1 —Diode

Technology Category: 5