Abstract:
An elevator control apparatus includes: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power having a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power having the variable voltage and the variable frequency, operating an elevator; a power storage unit for storing the DC power; a required power computing circuit for computing required power of the elevator based on a speed command of the controller; a charge/discharge control circuit for issuing a drive signal for changing charge current, supplied to the power storage unit, based on regenerative electric power so as to charge the power storage unit with the regenerative electric power if the required power of the elevator is negative, meaning that the regenerative electric power is available; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signal. Thus, regenerative electric power can be effectively used, contributing to energy savings.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an elevator control apparatus utilizing a power storage unit. 
     2. Description of the Related Art 
     A conventional elevator control apparatus will be described with reference to an accompanying drawing. FIG. 19 shows a construction of a conventional elevator control apparatus disclosed, for example, under a title of “Redesigned medium-to-low speed passenger elevator, Grandy” on page 9 of Mitsubishi Denki Giho (written by Ando, Kimura, and Mori, Vol. 70, No. 11 issued in 1996). 
     The conventional elevator control apparatus shown in FIG. 19 includes a commercial three-phase AC power source  1 , a motor  2 , such as an induction motor IM, a hoisting machine  3 , a rope  4 , an elevator car  5 , a counterweight  6 , an encoder  7 , a controller  8 , a converter  9  formed of a diode or the like, a capacitor  10 , a current detector  11 , such as a current transformer (CT), an inverter  12 , an inverter control circuit  13 , a gate drive circuit  14 , a regenerative resistor  15 , and a switching means  16 , such as an IGBT. 
     An operation of the aforesaid conventional elevator control apparatus will now be described with reference to the drawing. 
     The hoisting machine  3  is driven by the motor  2  to move the elevator car  5  and the counterweight  6  connected to both ends of the rope  4 , thereby carrying passengers in the car to a predetermined floor. 
     The converter  9  rectifies AC power supplied from the commercial power source  1  to convert it into DC power, which is stored in the capacitor  10 . The DC power is converted into AC power of a variable voltage and a variable frequency by the inverter  12 . 
     The controller  8  controls starts and stops of the elevator and also creates commands regarding start and stop positions and speed. Based on a speed command supplied by the controller  8 , the inverter control circuit  13  rotationally drives the motor  2  by reflecting current feedback from the current detector  11  and speed feedback from the encoder  7  mounted on the hoisting machine  3 , thereby implementing the position and speed control of the elevator. At this time, the inverter control circuit  13  controls output voltages and frequencies of the inverter  12  via the gate drive circuit  14 . 
     The counterweight  6  of the elevator is set such that it is balanced when the car  5  is loaded with a moderate number of passengers. For example, when the elevator travels in a balanced state, it is possible to increase the speed of the elevator while consuming electric power in an acceleration mode, and to turn accumulated speed energy back into electric power in a deceleration mode. In typical elevators, however, the regenerative electric power is consumed by being converted into heat energy by the regenerative resistor  15  by controlling the switching means  16 . 
     The conventional elevator control apparatus described above operates the elevator by constantly supplying electric power from the commercial power source. This has been posing a problem in that the electric power generated during a regenerative mode of the elevator is thermally consumed mainly by the regenerative resistor rather than being effectively used. 
     SUMMARY OF THE INVENTION 
     The present invention has been made with a view toward solving the foregoing problem, and it is an object of the present invention to provide an elevator control apparatus that permits energy saving by effectively utilizing electric power generated during a regenerative mode of an elevator. 
     To this end, according to one aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a required power computing circuit for computing required power of the elevator based on a speed command of the controller; a charge/discharge control circuit which conducts control by changing charge current, which is to be supplied to the power storage unit, based on regenerative electric power, and issues a drive signal for charging the power storage unit with the regenerative electric power if required power of the elevator is negative, that is, if the regenerative electric power is available; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signal. 
     According to another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a required power computing circuit for computing required power of the elevator based on a speed command of the controller; a charge/discharge control circuit which carries out control such that a bus voltage between the converter and the inverter stays constant at a preset voltage that is not less than a voltage obtained by rectifying the AC power, and issues a drive signal for charging the power storage unit with the regenerative electric power if required power of the elevator is negative, that is, if the regenerative electric power is available; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signal. 
     According to yet another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a required power computing circuit for computing required power of the elevator based on a speed command of the controller and issuing a regenerative operation signal if the required power is negative; a charge/discharge control circuit that starts charge control of regenerative electric power and issues a drive signal for charging the power storage unit with the regenerative electric power upon receipt of the regenerative operation signal; and a charge/discharge circuit for starting charging the power storage unit with the regenerative electric power in accordance with the drive signal. 
     According to still another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that stops charge control of regenerative electric power and issues a drive signal for stopping charging the power storage unit with the regenerative electric power upon receipt of an elevator stop signal from the controller; and a charge/discharge circuit for stopping charging the power storage unit with the regenerative electric power in accordance with the drive signal. 
     According to a further aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that starts charge control of regenerative electric power and issues a drive signal for charging the power storage unit with the regenerative electric power when a bus voltage between the converter and the inverter reaches a preset predetermined voltage that is higher than a voltage obtained by rectifying the AC power; and a charge/discharge circuit for starting charging the power storage unit with the regenerative electric power in accordance with the drive signal. 
     According to a further aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that carries out control such that a bus voltage between the converter and the inverter stays constant at a present voltage that is not less than a voltage obtained by rectifying the AC power, and stops the charge control of regenerative electric power and issues a drive signal for stopping charging the power storage unit with the regenerative electric power when charge current is controlled until it reaches zero; and a charge/discharge circuit for stopping charging the power storage unit with the regenerative electric power in accordance with the drive signal. 
     According to another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that controls a charge current supplied to the power storage unit at a constant present predetermined current value and issues a drive signal for charging the power storage unit with the regenerative electric power at the constant current; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signal. 
     According to a further aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that stops charge control of regenerative electric power and issues a drive signal for stopping charging the power storage unit with the regenerative electric power when a bus voltage between the converter and the inverter reaches a preset predetermined voltage that is higher than a voltage obtained by rectifying the AC power; and a charge/discharge circuit for stopping charging the power storage unit with the regenerative electric power in accordance with the drive signal. 
     According to another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit that controls charge current supplied to the power storage unit at a plurality of present predetermined constant current values in steps based on the bus voltage between the converter and the inverter, and issues a drive signal for charging the power storage unit with regenerative electric power at constant current; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signal. 
     According to a further aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit which carries out control such that a bus voltage between the converter and the inverter stays constant at a preset predetermined voltage and that, when charge current supplied to the power storage unit reaches a preset predetermined upper limit value, the charge current stays at the upper limit value, and issues a drive signal for charging the power storage device with regenerative electric power; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signal. 
     In a preferred form of the invention, when the charge current supplied to the power storage unit reaches the predetermined upper limited value, and if the bus voltage exceeds a preset second predetermined voltage while charging the power storage unit at the upper limit value is being continued, then the charge/discharge control circuit causes a part of the regenerative electric power to be thermally consumed by a resistor. 
     According to a further aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit which carries out control such that a bus voltage between the converter and the inverter stays constant at a preset predetermined voltage, issues a first drive signal for charging the power storage unit with the regenerative electric power control, and stops charge control of the regenerative electric power and issues a second drive signal for stopping charging the power storage unit with the regenerative electric power when a voltage of the power storage unit reaches a preset predetermined upper limit value; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the first drive signal and for stopping charging the power storage unit with the regenerative electric power in accordance with the second drive signal. 
     According to another aspect of the present invention, there is provided an elevator control apparatus including: a converter for rectifying AC power into DC power; an inverter for converting the DC power into AC power of a variable voltage and a variable frequency; a controller for controlling a motor based on the AC power of the variable voltage and the variable frequency so as to operate an elevator; a power storage unit for storing the DC power; a charge/discharge control circuit which carries out control such that a bus voltage between the converter and the inverter stays constant at a preset predetermined voltage, issues a drive signal for charging the power storage unit with regenerative electric power, and carries out control such that the charge current supplied to the power storage unit reaches a predetermined upper limit value and issues a drive signal for charging the power storage unit with regenerative electric power when a voltage of the power storage unit reaches a preset predetermined voltage; and a charge/discharge circuit for charging the power storage unit with the regenerative electric power in accordance with the drive signals. 
     In a preferred form of the invention, when the voltage of the power storage unit reaches the preset predetermined voltage, and if the bus voltage exceeds a preset second predetermined voltage while charging the power storage unit at the upper limit value is being continued, then the charge/discharge control circuit causes a part of the regenerative electric power to be thermally consumed by a resistor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a construction of an elevator control apparatus according to a first embodiment of the present invention; 
     FIG. 2 is a circuit diagram showing a configuration of a charge/discharge circuit of the elevator control apparatus according to the first embodiment of the present invention; 
     FIG. 3 is a circuit diagram showing a configuration of an inverter control circuit and a configuration of a required power computing circuit of the elevator control apparatus according to the first embodiment of the present invention; 
     FIG. 4 is a circuit diagram showing a configuration of a charge/discharge control circuit of the elevator control apparatus according to the first embodiment of the present invention; 
     FIG. 5 is a diagram showing a charge current waveform of the elevator control apparatus according to the first embodiment of the present invention; 
     FIG. 6 is a circuit diagram showing a configuration of a charge/discharge control circuit of an elevator control apparatus according to a second embodiment of the present invention; 
     FIGS.  7 (A) and  7 (B) are timing charts illustrating an operation of the elevator control apparatus according to the second embodiment of the present invention; 
     FIGS.  8 (A)- 8 (C) are timing charts illustrating an operation of the elevator control apparatus according to a third embodiment of the present invention; 
     FIG. 9 is a circuit diagram showing a configuration of a charge/discharge control circuit of an elevator control apparatus according to a fourth embodiment of the present invention; 
     FIGS.  10 (A)- 10 (C) are timing charts illustrating an operation of an elevator control apparatus according to a fourth embodiment of the present invention; 
     FIGS.  11 (A)- 11 (C) are timing charts illustrating an operation of an elevator control apparatus according to a fifth embodiment of the present invention; 
     FIGS.  12 (A)- 12 (C) are timing charts illustrating an operation of an elevator control apparatus according to a sixth embodiment of the present invention; 
     FIGS.  13 (A)- 13 (C) are timing charts illustrating an operation of an elevator control apparatus according to a seventh embodiment of the present invention; 
     FIG. 14 is a diagram showing a construction of an elevator control apparatus according to an eighth embodiment of the present invention; 
     FIGS.  15 (A)- 15 (D) are timing charts illustrating an operation of the elevator control apparatus according to the eighth embodiment of the present invention; 
     FIGS.  16 (A)- 16 (D) are timing charts illustrating an operation of the elevator control apparatus according to a ninth embodiment of the present invention; 
     FIGS.  17 (A)- 17 (D) are timing charts illustrating an operation of the elevator control apparatus according to a tenth embodiment of the present invention; 
     FIGS.  18 (A)- 18 (D) are timing charts illustrating an operation of the elevator control apparatus according to an eleventh embodiment of the present invention; and 
     FIG. 19 is a diagram showing a construction of a conventional elevator control apparatus. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     An elevator control apparatus according to a first embodiment of the present invention will be described in conjunction with the accompanying drawings. FIG. 1 is a diagram showing a construction of the elevator control apparatus according to the first embodiment of the present invention. In the drawings, the like reference numerals will denote like or equivalent components. 
     A three-phase AC power source  1  through a gate drive circuit  14  in FIG. 1 are equivalent to the like components of FIG. 19 described in the foregoing conventional example. 
     The elevator control apparatus shown in FIG. 1 further includes a power storage unit  21  composed of a battery, a charge/discharge circuit  22  composed of a DC/DC converter or the like, a charge/discharge control circuit  23  for controlling charging and discharging power of the charge/discharge circuit  22 , a current detector  24  which is composed of a current transformer (CT) or the like and which detects an input/output current of the power storage unit  21 , a required power computing circuit  50  for computing required power of an elevator, and a communication cable  51  for transmitting a signal indicating the required power computed by the required power computing circuit  50 . 
     FIG. 2 is a circuit diagram showing a configuration of the charge/discharge circuit. Referring to FIG. 2, reference numeral  25  denotes a reactor, a reference numerals  26  and  27  denote switching devices, such as IGBTs or the like, and reference numerals  28  and  29  denote diodes that are connected inversely in parallel. 
     The power storage unit  21  is charged by a step-down chopper circuit formed by the switching device  26  and the diode  29 . Discharging from the power storage unit  21  is performed by a step-up chopper circuit formed by the switching device  27  and the diode  28 . 
     FIG. 3 is a block diagram showing the configurations of an inverter control circuit and a required power computing circuit shown in FIG.  1 . Referring to FIG. 3, a three-phase into two-phase coordinate converter  33  converts three-phase AC currents Iu, Iv, and Iw into values on a two-axis rotating coordinate system (d-q coordinate system) that rotates in synchronization with a frequency ωl of an AC voltage applied to a stator winding, i.e. stator winding currents Id and Iq. A magnetic flux computing device  38  calculates a magnetic flux Φ2d interlinking a rotor from the stator winding current Id on the d-q coordinate system. 
     FIG. 3 further shows a PWM signal generating circuit  31 , a two-phase into three-phase coordinate converter  32  for converting voltage command values Vd and Vq on the d-q coordinate system into three-phase AC voltage command values, a d-axis current controller  34  that performs, for example, a proportional integral operation on a difference between a d-axis component command value Id* of a stator winding current and its actual value Id thereby to control a d-axis current to a command value, and a q-axis current controller  35  that also performs, for example, the proportional integral operation on a difference between a q-axis component command value Iq* of a stator winding current and its actual value Iq thereby to control a q-axis current to a command value. 
     FIG. 3 further shows a magnetic flux controller  36  for controlling a d-axis component Φ2d of a rotor winding interlinking magnetic flux to a desired value Φ2d*, a velocity controller  37  for controlling a rotor angular velocity ωr to a desired value ωr*, a dividing device  39 , and a coefficient device  40 . A slip frequency command ωs* is calculated by the dividing device  39  and the coefficient device  40 . 
     In FIG. 3, reference numerals  41 ,  42 ,  43 ,  44 , and  45  denote adders or subtractors. Reference numeral  46  denotes an integrator. 
     In the drawing, reference numeral  47  denotes an adder, reference numerals  48  and  49  denote integrators, and reference numeral  50  denotes a required power computing device. A product of a voltage command value Vd and a stator winding current Id on the d-q coordinate system and a product of a voltage command value Vq and a stator winding current Iq are added to compute required power Pw of an elevator. 
     The required power computing device  50  is able to perform a similar computation to the above computation by adding a product of the voltage command value Vd and a stator winding current command value Id* on the d-q coordinate system and a product of the voltage command value Vq and a stator winding current command value Iq*. 
     Lastly, an output three-phase AC voltage command value of the two-phase into three-phase coordinate converter  32  is sent to the PWM signal generating circuit  31 , and the inverter  12  is driven by the gate drive circuit  14 . 
     FIG. 4 is a block diagram showing a configuration of a charge control circuit of the charge/discharge control circuit of FIG.  1 . Referring to FIG. 4, the charge control circuit includes a gate drive circuit  52 , a PWM signal circuit  53  for generating a PWM modulation signal, and a charge current controller  54  that performs, for example, proportional integral operation on a difference between a charge current command value Icc and an actual value Ic of a charge current detected by the current detector  24  of FIG. 1, thereby controlling the charge current to the charge current command value. The charge control circuit further includes a subtractor  55  and a dividing device  56 . 
     An operation of the elevator control apparatus according to the first embodiment will now be described with reference to the accompanying drawings. FIG. 5 shows a charge current waveform of the elevator control apparatus according to the first embodiment of the present invention. 
     The elevator travels according to a predetermined speed command issued by the inverter control circuit  13  shown in FIG.  1 . At the same time, the required power computing circuit  50  computes the required power Pw of the elevator, and the computed required power Pw is output to the charge/discharge control circuit  23  via the communication cable  51 . 
     Based on the required power Pw, the charge control circuit of the charge/discharge control circuit  23  shown in FIG. 4 charges the power storage unit  21  with the power regenerated by the elevator by actuating the control circuit  22  for charging power shown in FIG. 2 during a regenerative mode of the elevator, that is, if the required power is negative. 
     The charging control circuit of the charge/discharge control circuit  23  uses the required power Pw computed by the required power computing circuit  50  and a battery voltage Vb to create the charge current command Icc according to the following expression (1): 
     
       
           Icc=Pw/Vb   (1) 
       
     
     Then, based on the charge current command Icc and the charge current Ic, the charge current controller  54  carries out control by changing the charge current as shown in FIG.  5 . 
     The regenerative electric power charged to the power storage unit  21  is discharged as necessary by the discharge circuit of the charge/discharge circuit  22  shown in FIG.  2  and used to drive the elevator. 
     Thus, in the regenerative mode, that is, if the required power is negative, the power storage unit  21  is charged with regenerative electric power, and the regenerative electric power charged to the power storage unit is discharged as necessary. With this arrangement, effective utilization of regenerative electric power can be achieved, and power supplied from the commercial power source  1  can be reduced, permitting energy saving. 
     Second Embodiment 
     An elevator control apparatus according to a second embodiment of the present invention will be described with reference to the accompanying drawings. 
     In the foregoing first embodiment, a case has been described wherein the charge current supplied to the power storage unit  21  is controlled if the required power Pw computed by the required power computing circuit  50  is negative. The second embodiment controls a voltage between P and N shown in FIG. 1, i.e. a bus voltage Vc, to a constant voltage in charging the power storage unit  21 . The second embodiment also provides the same advantages as those of the first embodiment. 
     The required power computing circuit  50  incurs some error in computing regenerative electric power due to mechanical or electrical losses or the like. For this reason, the bus voltage decreases if a computer value is larger than actual regenerative electric power, while the bus voltage increases if a computed value is smaller than actual regenerative electric power. Controlling the bus voltage Vc at a constant voltage allows the bus voltage to be maintained at a predetermined value, permitting the power storage unit  21  to be charged more accurately based on actual regenerative electric power. 
     FIG. 6 is a block diagram showing a configuration of a charging control circuit of a charge/discharge control circuit of an elevator control apparatus according to the second embodiment of the present invention. The rest of the configuration is the same as the configuration of the first embodiment described above. 
     Referring to FIG. 6, reference numerals  52  through  55  denote the same components as those of the charging control circuit of FIG. 4 shown in the aforesaid first embodiment. Reference numeral  23 A denotes a charge/discharge control circuit, reference numeral  57  denotes a voltage controller, and reference numeral  58  denotes a subtractor. 
     An operation of the elevator control apparatus according to the second embodiment will now be described in conjunction with the accompanying drawings. FIGS.  7 (A) and  7 (B) are timing charts illustrating the operation of the elevator control apparatus according to the second embodiment of the present invention, wherein FIG.  7 (A) shows a waveform of the bus voltage, and FIG.  7 (B) shows a waveform of charge current. 
     The elevator travels according to a predetermined speed command issued by the inverter control circuit  13  shown in FIG.  3 . At the same time, the required power computing circuit  50  shown in FIG. 1 computes the required power Pw of the elevator, and if the required power becomes negative, then a regenerative operation signal is output to a charge/discharge control circuit  23 A via the communication cable  51 . 
     Upon receipt of the regenerative operation signal of the elevator, the charging control of the charge/discharge control circuit  23 A starts as illustrated in FIGS.  7 (A) and  7 (B) to charge the power storage unit  21  with the regenerative electric power of the elevator. 
     Based on a predetermined voltage command (a voltage not less than the voltage obtained by rectifying a supply voltage), a charging power control circuit in the charge/discharge control circuit  23 A controls the voltage to a constant voltage by a voltage controller  57  as shown in FIG.  6 . Furthermore, the charge current is controlled by a charge current controller  54  to precisely charge the power storage unit  21  with the regenerative electric power. To conduct the charging control of the charge/discharge control circuit  23 A, an elevator stop signal is received from the controller  8  shown in FIG. 1 via a communication cable or the like (not shown in FIG. 1) so as to stop the elevator as shown in FIGS.  7 (A) and  7 (B). 
     Third Embodiment 
     An elevator control apparatus according to a third embodiment of the present invention will be described with reference to the accompanying drawings. The basic construction of the elevator control apparatus according to the third embodiment is identical to the construction of the foregoing first embodiment. 
     In the second embodiment described above, the control of charging the power storage unit  21  with regenerative electric power is begun upon receipt of the elevator regenerative operation signal. In the third embodiment, the control of charging the power storage unit  21  with regenerative electric power is begun from a moment a preset bus voltage is reached during a regenerative operation mode of the elevator. The preset bus voltage is higher than a voltage obtained by rectifying and smoothing a supply voltage. With this arrangement, the same advantages can be obtained, and the need for the communication cable  51  or the like can be obviated. 
     In the second embodiment, an elevator stop signal from the controller  8  is received via the communication cable or the like to stop the control of charging the power storage unit  21  with regenerative electric power. In the third embodiment, the charging control is stopped when charge current reaches zero. This arrangement enables the same advantages to be obtained and also obviates the need for a communication cable or the like. 
     An operation of the third embodiment will now be described. FIGS.  8 (A)- 8 (C) show waveforms related to the elevator control apparatus according to the third embodiment of the present invention, wherein FIG.  8 (A) shows a bus voltage waveform, FIG.  8 (B) shows a waveform of a regenerative current from a motor  2 , and FIG.  8 (C) shows a waveform of charge current supplied to the power storage unit  21 . 
     When the elevator starts its regenerative operation, regenerative current is supplied to the capacitor  10  of FIG.  1  and the bus voltage increases as illustrated in FIG.  8 (A). The control of charging the power storage unit  21  with regenerative electric power is started from the moment the bus voltage reaches a voltage Vs that has been preset at a voltage higher than a voltage obtained by rectifying and smoothing a supply voltage as shown in FIG.  8 (C). 
     A charging power control circuit in a charge/discharge control circuit  23 A controls the voltage to a constant voltage by a voltage controller  57  based on a predetermined voltage command (the same voltage as the voltage Vs at which the charging control is started in this embodiment), and the charge current is controlled by a charge current controller  54  as shown in FIG. 6, thereby precisely charging the power storage unit  21  with regenerative electric power. 
     The charging control by the charge/discharge control circuit  23 A is stopped after the moment a charge current detected by a current detector  24  shown in FIG. 1 reaches zero. 
     Fourth Embodiment 
     An elevator control apparatus according to a fourth embodiment of the present invention will be described with reference to the accompanying drawings. The basic construction of the elevator control apparatus according to the fourth embodiment is identical to the construction of the foregoing first embodiment. 
     FIG. 9 is a block diagram showing a configuration of a charging control circuit in a charge/discharge control circuit of the elevator control apparatus according to the fourth embodiment of the present invention. Referring to FIG. 9, reference numeral  23 B denotes a charge/discharge control circuit, and a gate drive circuit  52  through a subtractor  55  are equivalent to the components of the charging control circuit of FIG. 4 referred to in the first embodiment of FIG. 6 referred to in the second embodiment. 
     In the first through third embodiments described above, the charge current of regenerative electric power supplied to the power storage unit  21  is controlled by changing it. In the fourth embodiment, the charging is performed at a constant current, making it possible to provide the same advantages as those of the first embodiment and also to prevent a sudden increase in a battery voltage attributable to large-current charging in the vicinity of a peak of regenerative electric power taking place before an elevator is stopped when the power storage unit  21  employs a battery, and further to prevent a gas from being produced in the battery, thus protecting the battery from rapid deterioration. 
     An operation of the fourth embodiment will now be described. FIGS.  10 (A)- 10 (C) show waveforms related to the elevator control apparatus according to the fourth embodiment of the present invention, wherein FIG.  10 (A) shows a bus voltage waveform, FIG.  10 (B) shows a waveform of a regenerative current from a motor  2 , and FIG.  10 (C) shows a waveform of charge current supplied to the power storage unit  21 . 
     Upon receipt of an elevator regenerative operation signal from the required power computing circuit  50  shown in FIG. 1 via the communication cable  51 , the charge/discharge control circuit  23 B performs charging at a constant current of a charge current command value Ic* as shown in FIG.  10 (C). 
     As shown in FIG. 9, the current is controlled to the constant current by a charge current controller  54 . 
     To carry out the charging control of the charge/discharge control circuit  23 B, an elevator stop signal from the controller  8  shown in FIG. 1 is received via a communication cable or the like (not shown in FIG.  1 ), and the elevator is stopped as illustrated in FIG.  10 (C). 
     Fifth Embodiment 
     An elevator control apparatus according to a fifth embodiment of the present invention will be described with reference to the accompanying drawings. The basic construction of the elevator control apparatus according to the fifth embodiment is identical to the construction of the foregoing first embodiment. 
     In the fourth embodiment described above, upon receipt of the elevator regenerative operation signal, the charging the power storage unit  21  is begun at a constant current, and the charging is stopped upon receipt of the elevator stop signal. In the fifth embodiment, control of charging the power storage unit  21  with regenerative electric power is begun at the moment a bus voltage, which is preset at a voltage higher than a voltage obtained by rectifying and smoothing a supply voltage, is reached, and the control of charging the power storage unit  21  with the regenerative electric power is stopped at the moment a preset but voltage is reached. The fifth embodiment provides the same advantages as those of the fourth embodiment described above, and also prevents the capacitor  10  from being charged with power supplied from the commercial power source  1  when there is more charge current than regenerative current, and prevents the bus voltage from markedly increasing when there is less charge current than regenerative current. 
     An operation of the fifth embodiment will now be described. FIGS.  11 (A)- 11 (C) show waveforms related to the elevator control apparatus according to the fifth embodiment of the present invention, wherein FIG.  11 (A) shows a bus voltage waveform, FIG.  11 (B) shows a waveform of a regenerative current from a motor  2 , and FIG.  11 (C) shows a waveform of charge current supplied to the power storage unit  21 . 
     When the regenerative operation of the elevator begins, the capacitor  10  shown in FIG. 1 is charged, and the bus voltage increases. As shown in FIG.  11 (A), when a bus voltage Vs preset at a voltage higher than a voltage obtained by rectifying and smoothing a supply voltage is reached, charging the power storage unit  21  with regenerative electric power at a constant current is started according to a charge current command value Ic*. 
     Then, as shown in FIG.  11 (A), when a preset bus voltage Ve (Ve&lt;Vs) is reached, the charging of the power storage unit  21  is stopped as illustrated in FIG.  11 (C). Thus, the power storage unit  21  can be charged based on regenerative current by changing the time for supplying the charge current. 
     Sixth Embodiment 
     An elevator control apparatus according to a sixth embodiment of the present invention will be described with reference to the accompanying drawings. The basic construction of the elevator control apparatus according to the sixth embodiment is identical to the construction of the foregoing first embodiment. 
     In the fourth and fifth embodiments described above, charging is performed at one preset constant current. In the sixth embodiment, a charge current value is changed in steps based on a bus voltage to provide substantially the same advantages as those of the fifth embodiment. 
     An operation of the sixth embodiment will now be described. FIGS.  12 (A)- 12 (C) show waveforms related to the elevator control apparatus according to the sixth embodiment of the present invention, wherein FIG.  12 (A) shows a bus voltage waveform, FIG.  12 (B) shows a waveform of a regenerative current from a motor  2 , and FIG.  12 (C) shows a waveform of charge current supplied to the power storage unit  21 . 
     When the regenerative operation of the elevator begins, the capacitor  10  shown in FIG. 1 is charged, and the bus voltage increases. As shown in FIG.  12 (A), when a first preset bus voltage Vs 1  that is higher than a voltage obtained by rectifying and smoothing a supply voltage is reached, charging the power storage unit  21  with regenerative electric power at a constant current is started according to a first charge current command value Ic 1 *. 
     Then, as shown in FIG.  12 (A), when a second preset bus voltage Vs 2  (Vs 2 &gt;Vs 1 ) is reached, charging the power storage unit  21  with regenerative electric power at a constant current is performed according to a second charge current command value Ic 2 *. Furthermore, when a third preset but voltage Vs 3  (Vs 3 &gt;Vs 2 ) is reached, charging the power storage unit  21  with regenerative electric power at a constant current is performed according to a third charge current command value Ic 3 *. 
     If the bus voltage decreases to the second bus voltage Vs 2  or the first bus voltage Vs 1 , then the charge current command value is changed accordingly. Some hysteresis voltage may be provided for a switching voltage between an increasing bus voltage and a decreasing bus voltage. When the bus voltage reaches Ve (Vs 1 &gt;Ve), the charging control of the charge circuit is stopped. 
     Although the sixth embodiment has referred to a case where the three-step switching system is used, any number of steps may be used as long as there are two steps or more. 
     Alternatively, the charging control may be started upon receipt of an elevator regenerative operation signal, and the charging control may be stopped upon receipt of an elevator stop signal. 
     Seventh Embodiment 
     An elevator control apparatus according to a seventh embodiment of the present invention will be described with reference to the accompanying drawings. The basic construction of the elevator control apparatus according to the seventh embodiment is identical to the construction of the foregoing first embodiment. 
     In the third embodiment described above, no upper limit value is provided for the charge current of the power storage unit  21 . In the seventh embodiment, the charge current is furnished with an upper limit value. The seventh embodiment is able to provide the same advantages as those of the above third embodiment and also to prevent a sudden increase in a battery voltage attributable to large-current charging in the vicinity of a peak of regenerative electric power taking place before an elevator is stopped when the power storage unit  21  employs a battery, and further to prevent a gas from being produced in the battery, thus protecting the battery from rapid deterioration. 
     An operation of the seventh embodiment will now be described. FIGS.  13 (A)- 13 (C) show waveforms related to the elevator control apparatus according to the seventh embodiment of the present invention, wherein FIG.  13 (A) shows a bus voltage waveform, FIG.  13 (B) shows a waveform of a regenerative current from a motor  2 , and FIG.  13 (C) shows a waveform of charge current supplied to the power storage unit  21 . 
     When the regenerative operation of the elevator begins, the capacitor  10  shown in FIG. 1 is charged, and the bus voltage increases. When a preset bus voltage Vs that is higher than a voltage obtained by rectifying and smoothing a supply voltage is reached as shown in FIG.  13 (A), control of charging the power storage unit  21  with regenerative electric power is started as shown in FIG.  13 (C). 
     A charging power control circuit in a charge/discharge control circuit  23 A controls a voltage to a constant voltage by a voltage controller  57  based on a predetermined voltage command (the same voltage as the voltage Vs at which the charging control is started in this embodiment), and the charge current is controlled by a charge current controller  54  as shown in FIG. 6, thereby precisely charging the power storage unit  21  with regenerative electric power. 
     An upper limit value I limit  is preset at a charge current value that is lower than a charge current at which the voltage of the power storage unit  21  suddenly increases or a gas is produced therein. When the charge current reaches the upper limit value I limit  as shown in FIG.  13 (C), charging is carried out at that upper limit value. The charging control by the charge/discharge control circuit  23 A is stopped after the moment a charge current detected by a current detector  24  shown in FIG. 1 reaches zero. 
     Alternatively, the charging control may be started upon receipt of an elevator regenerative operation signal, and the charging control may be stopped upon receipt of an elevator stop signal. 
     Eighth Embodiment 
     An elevator control apparatus according to an eighth embodiment of the present invention will be described in conjunction with the accompanying drawings. FIG. 14 shows a construction of the elevator control apparatus according to the eighth embodiment of the present invention. 
     Referring to FIG. 14, reference numeral  15  denotes a resistor, and reference numeral  16  denotes a switching means, such as an IGBT. The rest of the components are equivalent to the components of FIG. 1 mentioned in the first embodiment described above. 
     In the above seventh embodiment, the charge current of the power storage unit  21  is provided with an upper limit value. In the eighth embodiment, the charge current is furnished with an upper limit value, and when the charge current supplied to the power storage unit  21  reaches a predetermined upper limit value, if a bus voltage exceeds a second predetermined voltage, then a part of regenerative electric power is thermally consumed by the resistor  15  while continuing charging the power storage unit  21  at the upper limit current value. With this arrangement, the same advantages as those of the above seventh embodiment can be obtained, and an increase in the bus voltage can be restrained, thus protecting an inverter circuit  12  from an overvoltage. 
     An operation of the eighth embodiment will now be described. FIG.  15 (A) shows a bus voltage waveform, FIG.  15 (B) shows a waveform of a regenerative current from a motor  2 , FIG.  15 (C) shows a waveform of charge current supplied to the power storage unit  21 , FIG.  15 (D) shows a waveform of the resistor  15 . 
     The eighth embodiment performs the same basic operation as the seventh embodiment described above, but differs therefrom in that, when the charge current supplied to the power storage unit  21  reaches a predetermined upper limit value I limit , if the bus voltage exceeds a second predetermined voltage Vrs as shown in FIG.  15 (A), then a charge/discharge control circuit  23  sends a signal to that effect to a controller  8  via a communication cable (not shown) while continuing charging the power storage unit  21  at the upper limit value I limit , and turns a switching means  16  On by a control signal from the controller  8  to pass current through the resistor  15  as illustrated in FIG.  15 (D) so as to thermally consume a part of regenerative electric power. This restrains a sudden increase in the bus voltage. When the bus voltage reaches a third predetermined voltage Vre of less, the switching means  16  is turned OFF. Alternatively, the switching means  16  may be turned ON or driven directly by the charge/discharge control circuit  23 . 
     Ninth Embodiment 
     An elevator control apparatus according to a ninth embodiment of the present invention will be described with reference to the accompanying drawings. The basic construction of the elevator control apparatus according to the ninth embodiment is the same as that of the first embodiment. 
     In the seventh embodiment, the charge current is provided with an upper limit value for the purpose of preventing a sudden increase in a battery voltage attributable to large-current charging in the vicinity of a peak of regenerative electric power taking place before an elevator is stopped when the power storage unit  21  employs a battery, and also preventing a gas from being produced in the battery, thus protecting the battery from rapid deterioration. For attaining the same purpose mentioned above, the ninth embodiment is adapted to stop charging the power storage unit  21  when the voltage of the power storage unit  21  reaches a preset upper limit voltage. The ninth embodiment provides the same advantages as those of the seventh embodiment. 
     An operation of the ninth embodiment will now be described. FIGS.  16 (A)- 16 (D) show waveforms related to the elevator control apparatus according to the ninth embodiment of the present invention, wherein FIG.  16 (A) shows a bus voltage waveform, FIG.  16 (B) shows a waveform of a regenerative current from a motor  2 , FIG.  16 (C) shows a waveform of charge current supplied to the power storage unit  21 , and FIG.  16 (D) shows a voltage waveform of the power storage unit  21 . 
     The ninth embodiment performs the same basic operation as the third embodiment described above, but differs therefrom in that, when the voltage of the power storage unit  21  reaches a preset upper voltage Vbe as shown in FIG.  16 (D), charging the power storage unit  21  is stopped as shown in FIG.  16 (C). 
     Tenth Embodiment 
     An elevator control apparatus according to a tenth embodiment of the present invention will be described with reference to the accompanying drawings. The basic construction of the elevator control apparatus according to the tenth embodiment is the same as that of the first embodiment. 
     In the ninth embodiment described above, the charging of the power storage unit  21  is stopped when the voltage of the power storage unit  21  reaches the preset upper limit voltage. In the tenth embodiment, when the voltage of the power storage unit  21  reaches a preset voltage, charging is continued, with an upper limit value being provided for the charge current supplied to the power storage unit  21 . This arrangement provides the same advantages as those of the ninth embodiment described above, and also permits further energy saving because charging the power storage unit  21  can be continued with regenerative electric power at a lower rate of charge current. 
     An operation of the tenth embodiment will now be described. FIGS.  17 (A)- 17 (D) show waveforms related to the elevator control apparatus according to the tenth embodiment of the present invention, wherein FIG.  17 (A) shows a bus voltage waveform, FIG.  17 (B) shows a waveform of a regenerative current from a motor  2 , FIG.  17 (C) shows a waveform of charge current supplied to the power storage unit  21 , and FIG.  17 (D) shows a voltage waveform of the power storage unit  21 . 
     The tenth embodiment performs the same basic operation as the ninth embodiment described above, but differs therefrom in that, when the voltage of the power storage unit  21  reaches a preset voltage Vbc as illustrated in FIG.  17 (D), the charging is continued, providing an upper limit value Ir at a lower rate for the charge current supplied to the power storage unit  21  as illustrated in FIG.  17 (C) so as to charge the power storage unit  21  with regenerative electric power as much as possible. 
     As in the case of the fifth embodiment described above, the upper limit value Ir of the charge current may take two values, namely, Ir and zero, according to the bus voltage or the voltage of the power storage unit  21 . Further alternatively, the upper limit value Ir of the charge current may change in steps according to the bus voltage or the voltage of the power storage unit  21 , as in the case of the sixth embodiment. 
     Eleventh Embodiment 
     An elevator control apparatus according to an eleventh embodiment of the present invention will be described with reference to the accompanying drawings. The basic construction of the elevator control apparatus according to the eleventh embodiment is the same as that of the eighth embodiment. 
     In the above tenth embodiment, the charge current of the power storage unit  21  is provided with an upper limit value when the voltage of the power storage unit  21  reaches a preset voltage. In the eleventh embodiment, the charge current is furnished with an upper limit value, and when the charge current supplied to the power storage unit  21  reaches a predetermined upper limit value, if a bus voltage exceeds a second predetermined voltage, then a part of regenerative electric power is thermally consumed by a resistor  15  while continuing charging the power storage unit  21  at the upper limit current value. With this arrangement, the same advantages as those of the above tenth embodiment can be obtained, and an increase in the bus voltage can be restrained, thus protecting an inverter circuit  12  from an overvoltage. 
     An operation of the eleventh embodiment will now be described. FIGS.  18 (A)- 18 (D) show waveforms related to the elevator control apparatus according to the eleventh embodiment of the present invention, wherein FIG.  18 (A) shows a bus voltage waveform, FIG.  18 (B) shows a waveform of a regenerative current from a motor  2 , FIG.  18 (C) shows a waveform of charge current supplied to the power storage unit  21 , and FIG.  18 (D) shows a waveform of the resistor  15 . 
     The eleventh embodiment performs the same basic operation as the tenth embodiment described above, but differs therefrom in that, after the voltage of the power storage unit  21  reaches a predetermined voltage Vs, if the bus voltage exceeds a second predetermined voltage Vrs as shown in FIG.  18 (A), then a switching means  16  is turned ON to pass current through the resistor  15  as illustrated in FIG.  18 (D) so as to thermally consume a part of regenerative electric power while continuing charging the power storage unit  21  at the upper limit current value Ir. This restrains a sudden increase in the bus voltage. When the bus voltage reaches a third predetermined voltage Vre or less, the switching means  16  is turned OFF.