Abstract:
A controller of an elevator for stably controlling regenerated power by using a cheap secondary battery of a low capacity without damaging energy saving effects obtained by charging. The controller of the elevator includes a converter for rectifying AC power and converting the AC power to DC power; an inverter for converting the DC power to AC power having a variable voltage and a variable frequency and operating the elevator; a power accumulating device for accumulating DC power from a DC bus in a regenerative operation of the elevator and supplying the DC power accumulated on the DC bus during a power operation time; a charging-discharging control circuit for controlling charging and discharging operations of the power accumulating device; a series connecting body arranged between DC buses and including a gate for regenerative current control and a regenerative resistor; a regenerative control circuit for controlling operation of the gate for regenerative current control; and a charging-discharging state measuring device for measuring charge and discharge states of the power accumulating device. The regenerative control circuit controls the operation of the gate for regenerative current control in control modes in which duty is different in accordance with a measured value of the charge and discharge states.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a controller of an elevator of an energy saving type to which a secondary battery is applied. 
     2. Description of the Related Art 
     FIG. 8 is a view showing the basic construction of a controller for controlling the operation of an elevator by applying a conventional secondary battery thereto. 
     In FIG. 8, reference numerals  1  and  2  respectively designate a three-phase AC power source and a converter constructed by a diode, etc. and converting AC power outputted from the three-phase AC power source  1  to DC power. The DC power converted by the converter  2  is supplied to a DC bus  3 . The operation of an inverter  4  is controlled by a speed controller for controlling a speed position of the elevator and described later. A direct current supplied through the DC bus  3  is converted to an alternating current of predetermined desirable variable voltage and variable frequency and an AC motor  5  is driven so that a hoisting machine  6  of the elevator directly connected to the AC motor  5  is rotated. Thus, a rope  7  wound around the hoisting machine  6  controls elevating and lowering operations of a car  8  and a counterweight  9  connected to both ends of this rope  7  and passengers within the car  8  are moved to a predetermined stage floor. 
     Here, weights of the car  8  and the counterweight  9  are designed such that these weights are approximately equal to each other when passengers half a number limit ride in the car  8 . Namely, when the car  8  is elevated and lowered with no load, a power running operation is performed at a lowering time of the car  8  and a regenerative operation is performed at a elevating time of the car  8 . Conversely, when the car  8  is lowered in the number limit riding, the regenerative operation is performed at the lowering time of the car  8  and the power running operation is performed at the elevating time of the car  8 . 
     An elevator control circuit  10  is constructed by a microcomputer, etc., and manages and controls an entire operation of the elevator. A power accumulating device  11  is arranged between DC buses  3  and accumulates power at the regenerative operation time of the elevator, and supplies the accumulated power to the inverter  4  together with the converter  2  at the power running operation time. The power accumulating device  11  is constructed by a secondary battery  12  and a DC-DC converter  13  for controlling charging and discharging operations of this secondary battery  12 . 
     Here, the DC-DC converter  13  has a voltage lowering type chopper circuit and a voltage raising type chopper circuit. The voltage lowering type chopper circuit is constructed by a reactor  13   a , a gate  13   b  for charging current control connected in series to this reactor  13   a , and a diode  13   c  connected in reverse parallel to a gate  13   d  for discharging current control described later. The voltage raising type chopper circuit is constructed by the reactor  13   a , the gate  13   d  for discharging current control connected in series to this reactor  13   a , and a diode  13   e  connected in reverse parallel to the above gate  13   b  for charging current control. Operations of the gate  13   b  for charging current control and the gate  13   d  for discharging current control are controlled by a charging-discharging control circuit  15  on the basis of a measuring value from a charging-discharging state measuring device  14  for measuring charging and discharging states of the power accumulating device  11  and a measuring value from a voltage measuring instrument  18 . A current measuring instrument arranged between the secondary battery  12  and the DC-DC converter  13  is used as the charging-discharging state measuring device  14  in this conventional example. 
     A gate  16  for regenerative current control and a regenerative resistor  17  are arranged between DC buses  3 . The voltage measuring instrument  18  measures the voltage of a DC bus  3 . A regenerative control circuit  19  is operated on the basis of regenerative control commands from a speed control circuit described later. The gate  16  for regenerative current control is constructed such that an ON pulse width is controlled on the basis of control of the regenerative control circuit  19  when a measuring voltage provided by the voltage measuring instrument  17  is equal to or greater than a predetermined value at the regenerative operation time. Regenerated power is discharged in the regenerative resistor  17  and is converted to thermal energy and is consumed. 
     An encoder  20  is directly connected to the hoisting machine  6 . The speed control circuit  21  controls a position and a speed of the elevator by controlling an output voltage and an output frequency of the inverter  4  on the basis of speed commands and a speed feedback output from the encoder  22  based on commands from the elevator control circuit  10 . 
     An operation of the controller having the above construction will next be explained. 
     At a power running operation time of the elevator, power is supplied to the inverter  4  from both the three-phase AC power source  1  and the power accumulating device  11 . The power accumulating device  11  is constructed by the secondary battery  12  and the DC-DC converter  13 , and an operation of this power accumulating device  11  is controlled by the charging-discharging control circuit  15 . In general, the number of secondary batteries  12  is reduced as much as possible and an output voltage of each secondary battery  12  is lower than the voltage of the DC bus  3  so as to make the controller compact and cheaply construct the controller. The voltage of the DC bus  3  is basically controlled near a voltage provided by rectifying a three-phase AC of the three-phase AC power source  1 . Accordingly, it is necessary to lower the bus voltage of the DC bus  3  at a charging time of the secondary battery  12  and raise the bus voltage of the DC bus  3  at a discharging time of the secondary battery  12 . Therefore, the DC-DC converter  13  is adopted. Operations of the gate  13   b  for charging current control and the gate  13   d  for discharging current control in this DC-DC converter  13  are controlled by the charging-discharging control circuit  15 . 
     FIGS. 9 and 10 are flow charts showing controls of the charging-discharging control circuit  15  at its discharging and charging times. 
     The control of the charging-discharging control circuit  15  at the discharging time shown in FIG. 9 will first be explained. 
     A current control minor loop, etc. are constructed in voltage control of a control system and the control operation may be more stably performed. However, for simplicity, the control of the charging-discharging control circuit  15  is here explained by a control system using the bus voltage. 
     First, the bus voltage of the DC bus  3  is measured by the voltage measuring instrument  17  (step S 11 ). The charging-discharging control circuit  15  compares this measuring voltage with a predetermined desirable voltage set value and judges whether the measuring voltage exceeds the voltage set value or not (step S 12 ). If no measuring voltage exceeds the set value, the charging-discharging control circuit  15  next judges whether the measuring value of a discharging current of the secondary battery  12  provided by the charging-discharging state measuring device  14  exceeds a predetermined value or not (step S 13 ). 
     When the measuring voltage exceeds the set value by these judgments, or when the measuring value of the discharging current of the secondary battery  12  exceeds the predetermined value even if no measuring voltage exceeds the set value, an adjusting time DT is subtracted from the present ON time to shorten an ON pulse width of the gate  13   d  for discharging current control and a new gate ON time is calculated (step S 14 ). 
     In contrast to this, when it is judged in the above step S 13  that no measuring value of the discharging current of the secondary battery  12  provided by the measuring device  14  exceeds the predetermined value, a new gate ON time is calculated by adding the adjusting time DT to the present ON time so as to lengthen the ON pulse width of the gate  13   d  for discharging current control (step S 15 ). Thus, ON control of the gate  13   d  for discharging current control is performed on the basis of the calculated gate ON time, and the calculated gate ON time is stored to a built-in memory as the present ON time (step S 16 ). 
     Thus, more electric current flows from the secondary battery  12  by lengthening the ON pulse width of the gate  13   d  for discharging current control. As a result, supply power is increased and the bus voltage of the DC bus  3  is increased by the power supplied. When the power running operation is considered, the elevator requires power and this power is supplied by discharging the secondary battery  12  and by power from the three-phase AC power source  1 . When the bus voltage is controlled such that this bus voltage is higher than an output voltage of the converter  2  supplied from the three-phase AC power source  1 , all power is supplied from the secondary battery  12 . However, the controller is designed such that all power is not supplied from the secondary battery  12 , but is supplied from the secondary battery  12  and the three-phase AC power source  1  in a suitable ratio to cheaply construct the power accumulating device  11 . 
     Namely, in FIG. 9, the measuring value of the discharging current is compared with a supply allotment corresponding current (predetermined value). If this measuring value exceeds the predetermined value, the ON pulse width of the gate  13   d  for discharging current control is lengthened and a supply amount is further increased. In contrast to this, when no measuring value of the discharging current exceeds the predetermined value, the ON pulse width of the gate  13   d  for discharging current control is shortened and the power supply is clipped. Thus, since power supplied from the secondary battery  12  is clipped from the power required in the inverter  4 , -the bus voltage of the DC bus  3  is reduced so that supply of power from the converter  2  is started. These operations are performed for a very short time so that a suitable bus voltage is actually obtained to supply required power of the elevator. Thus, power can be supplied from the secondary battery  12  and the three-phase AC power source  1  in a predetermined desirable ratio. 
     The control of the charging-discharging control circuit  15  at the charging time shown in FIG. 10 will next be explained. 
     When there is power regeneration from the AC motor  5 , the bus voltage of the DC bus  3  is increased by this regenerated power. When this voltage is higher than an output voltage of the converter  2 , the power supply from the three-phase AC power source  1  is stopped. When there is no power accumulating device  11  and this stopping state is continued, the voltage of the DC bus  3  is increased. Therefore, when a measuring voltage value of the voltage measuring instrument  17  for detecting the bus voltage of the DC bus  3  reaches a certain predetermined voltage, the regenerative control circuit  19  is operated and closes the gate  16  for regenerative current control. Thus, power flows through the regenerative resistor  17  and the regenerated power is consumed and the elevator is decelerated by electromagnetic braking effects. However, when there is the power accumulating device  11 , this power is sent to the power accumulating device  11  by the control of the charging-discharging control circuit  15  with a voltage equal to or smaller than a predetermined voltage. 
     Namely, as shown in FIG. 10, if the measuring value of the bus voltage of the DC bus  3  provided by the voltage measuring instrument  17  exceeds the predetermined voltage, the charging-discharging control circuit  15  detects that it is a regenerative state, and increases a charging current to the secondary battery  12  by lengthening the ON pulse width of the gate  13   b  for charging current control (step S 21 →S 22 →S 23 ). When the regenerated power from the elevator is reduced in a short time, the voltage of the DC bus  3  is also correspondingly reduced and no measuring value of the voltage measuring instrument  17  exceeds the predetermined voltage. Accordingly, the ON pulse width of the gate  13   b  for charging current control is shortly controlled and charging power is also reduced and controlled (step S 21 →S 22 →S 24 ). 
     Thus, the bus voltage is controlled in a suitable range and a charging operation is performed by monitoring the bus voltage of the DC bus  3  and controlling the charging power. Further, energy is saved by accumulating and re-utilizing power conventionally consumed in the regenerated power. When no power of a charger is consumed for certain reasons, such as a breakdown, etc., the regenerative control circuit  19  is operated as a backup and the regenerated power is consumed by a resistor so that the elevator is suitably decelerated. In a general elevator for housing, the regenerated power is about 2 KVA and is about 4 KVA at its maximum decelerating value, although this regenerated power varies in accordance with capacity of the elevator, etc. 
     The regenerative control circuit  19  monitors the voltage of the DC bus  3 . If this voltage is equal to or greater than a predetermined value, the ON pulse width of the gate  16  for regenerative current control is controlled by the regenerative control circuit  19  so as to discharge the power in the regenerative resistor  17 , so that the regenerated power flows through the regenerative resistor  17 . There are various kinds of systems for controlling this pulse width, but the pulse width is simply controlled in accordance with the following formula. Namely, when the voltage of the DC bus  3  for starting turning-on of the gate  16  for regenerative current control is set to VR, a flowing current IR can be simply calculated by turning-on (closing) a circuit since the resistance of the regenerative resistor  17  is already known. Further, maximum power flow is already known. Therefore, if this maximum power (VA) is set to WR, it is sufficient to generate an ON pulse with a duty of WR/(VR×IR) while the DC bus voltage is monitored. However, an object of this construction is to consume all regenerated power in the regenerative resistor  17 . 
     However, in the conventional controller of the elevator, it is necessary to use the secondary battery  12  having a large capacity and able to be charged by the regenerated power, in the power accumulating device  11 , for all conditions, in which a temperature and charging degree of the power accumulating device  11 , i.e., a full charging state of the power accumulating device  11 , are set to reference values and a product of a charging-discharging current and a charging-discharging voltage is normalized and accumulated as a capacity, and a SOC (State Of Charge) is obtained as this normalized and accumulated value, etc. Therefore, an expensive and large sized power accumulating device  11  is required. 
     SUMMARY OF THE INVENTION 
     To solve the above-mentioned problems, an object of the present invention is to provide a controller of an elevator capable of stably controlling regenerated power by using a cheap secondary battery of a low capacity without damaging energy saving effects obtained by charging. 
     To achieve this object, a controller of an elevator in this invention comprises a converter for rectifying AC power from an AC power source and converting the AC power to DC power; an inverter for converting the DC power to AC power of a variable voltage and a variable frequency and driving an electric motor and operating the elevator; power accumulating means arranged between DC buses between the converter and the inverter, and accumulating DC power from the DC buses at a regenerative operation time of the elevator and supplying the DC power accumulated on the DC buses at a power running operation time; charging-discharging control means for controlling charging and discharging operations of the power accumulating means with respect to the DC buses; a series connecting body arranged between the DC buses and constructed by a gate for regenerative current control and a regenerative resistor for discharging regenerated power flowing-in through this gate for regenerative current control; regenerative control means for controlling an operation of the gate for regenerative current control; and charging-discharging state measuring means for measuring charging and discharging states of the power accumulating means; the regenerative control means controlling the operation of the gate for regenerative current control in plural control modes in which an electric current or power flowing through the regenerative resistor is different in accordance with a measuring value from the charging-discharging state measuring means. 
     Further, the charging-discharging state measuring means includes bus voltage measuring means for measuring a bus voltage of each of the DC buses, and a measuring value of the bus voltage is outputted as a measuring value of the charging and discharging states, and the regenerative control means controls an ON pulse of the gate for regenerative current control in accordance with the measuring value of the bus voltage. 
     Further, the charging-discharging state measuring means further comprises charging voltage measuring means for measuring a charging voltage of the power accumulating means, and the regenerative control means controls the ON pulse of the gate for regenerative current control in accordance with the measuring value of the bus voltage and a measuring value of the charging voltage. 
     Further, the charging-discharging state measuring means measures at least one of charging and discharging currents, charging and discharging voltages and a temperature of the power accumulating means, and the regenerative control means has a table setting duty therein in accordance with these measuring values, and an ON pulse of the gate for regenerative current control is controlled in accordance with the duty set in the table. 
     Further, the regenerative control means has a table setting duty therein in accordance with the charging current and the charging voltage. 
     Further, the regenerative control means has plural tables according to temperatures, and selects a table according to a measuring temperature from the charging-discharging state measuring means, and controls the ON pulse of the gate for regenerative current control in accordance with the duty according to the charging current and the charging voltage. 
     Further, the regenerative control means has a table setting duty therein in accordance with the charging voltage and a changing amount of the charging voltage. 
     Further, the regenerative control means has plural tables each according to a charging degree as a value obtained by normalizing and accumulating a product of a charging-discharging current by a charging-discharging voltage in a capacity with a full charging state of the power accumulating means as a reference, and selects a table according to the charging degree, and controls the ON pulse of the gate for regenerative current control in accordance with the duty according to the charging voltage and the changing amount of the charging voltage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the construction of a controller of an elevator in this invention. 
     FIG. 2 is a flow chart showing control contents of a regenerative control circuit in an embodiment of this invention. 
     FIG. 3 is a flow chart showing control contents of the regenerative control circuit in an embodiment of this invention. 
     FIG. 4 is an explanatory view of a table arranged in the regenerative control circuit in an embodiment of this invention in which duty is set in the table in accordance with a charging current and a charging voltage. 
     FIG. 5 is an explanatory view of plural tables arranged in the regenerative control circuit in an embodiment of this invention in which duty according to temperature is set in the tables in accordance with the charging current and the charging voltage. 
     FIG. 6 is an explanatory view of a table arranged in the regenerative control circuit in an embodiment of this invention in which duty is set in the table in accordance with the charging voltage and a changing amount of the charging voltage. 
     FIG. 7 is an explanatory view of plural tables arranged in the regenerative control circuit in an embodiment of this invention in which duty according to a charging degree SOC is set in the tables in accordance with the charging voltage and the changing amount of the charging voltage. 
     FIG. 8 is a block diagram showing the construction of a controlled of an elevator in a conventional example. 
     FIG. 9 is a flow chart showing the control of a charging-discharging control circuit shown in FIG. 8 at its discharging time. 
     FIG. 10 is a flow chart showing the control of the charging-discharging control circuit shown in FIG. 8 at its charging time. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In this invention, a cheap secondary battery of a low capacity is used as a secondary battery for a power accumulating device, and a control operation is performed such that regenerated power can be stably controlled without damaging energy saving effects obtained by charging. 
     Characteristics of the secondary battery used in the power accumulating device are different from each other in accordance with kinds of the battery such as a lead battery, a nickel hydrogen battery, etc. However, in general, no charging operation is efficiently performed in relation to a solvent within the battery in states in which temperature is lower and higher than a normal temperature. Further, when a charging degree is high (approaches a full charge), no charging operation is efficiently performed. When a large electric current is charged in such bad charging reception states, an increase in internal resistance, i.e., increases in heating of the battery and charging voltage are caused and subsequent charging performance is further deteriorated. Therefore, it is necessary to control an operation of the secondary battery so as not to excessively charge the secondary battery as much as possible. 
     FIG. 1 is a block diagram showing the construction of a controller of an elevator in this invention. In FIG. 1, the same reference numerals as the conventional example shown in FIG. 8 are designated by the same reference numerals and their explanations are omitted here. New reference numerals  14 A and  19  A respectively designate a charging-discharging state measuring device and a regenerative control circuit in the present invention. The regenerative control circuit  19 A controls the operation of a gate  16  for regenerative current control in plural control modes in which an electric current or power flowing through a regenerative resistor is different in accordance with a measuring value from the charging-discharging state measuring device  14 A. 
     Concrete embodiment modes will next be explained. 
     Embodiment mode 1 
     In this embodiment mode 1, the charging-discharging state measuring device  14 A is separately shown in FIG.  1 . However, the charging-discharging state measuring device  14 A includes a voltage measuring instrument  18  for measuring a bus voltage of a DC bus  3 , and considers a measuring value of this bus voltage as a charging-discharging state measuring value and outputs this measuring value to the regenerative control circuit  19 A. The regenerative control circuit  19 A controls the operation of the gate  16  for regenerative current control in plural control modes in which an electric current or power flowing through a regenerative resistor is different in accordance with the measuring value of the bus voltage. 
     The control of the regenerative control circuit  19 A in the embodiment mode  1  of this invention will next be explained with reference to the flow chart shown in FIG.  2 . 
     The regenerative control circuit  19 A determines an ON pulse width of the gate  16  for regenerative current control by the bus voltage of the DC bus  3 . It is first judged whether the measured bus voltage exceeds a second stage voltage V 2  or not (steps S 101 , S 102 ). Here, the second stage voltage V 2  is set to suppose that there is abnormality at a charging time, etc. The second stage voltage V 2  is a voltage for performing a monitoring operation for flowing all regenerated power through the regenerative resistor  17 . If the measured bus voltage exceeds this second stage voltage V 2 , duty of the ON pulse of the gate  16  for regenerative current control is set to B and a state for flowing all power through the regenerative resistor  17  is attained as in the conventional case (step S 102 →S 103 ). 
     In contrast to this, when no measured bus voltage exceeds the second stage voltage V 2 , it is next judged whether the bus voltage exceeds a first stage voltage V 1  or not (step S 102 →S 104 ). Here, the first stage voltage V 1  is lower than the above second stage voltage V 2  and is higher than a voltage for starting charging of the power accumulating device  11  and is set in a regenerative charging state. If the bus voltage exceeds this voltage V 1 , the duty is set to A (step S 104 →S 105 ). Here, for example, A is set such that the duty in A is set to ½ to ⅓ times the duty in B and regenerated power ½ to ⅓ times the regenerated power in B flows through the regenerative resistor  17 . In contrast to this, if no bus voltage exceeds the voltage V 1 , the duty is set to 0 (step S 104 →S 106 ). The width of the ON pulse of the gate  16  for regenerative current control is controlled in accordance with such a set duty (step S 107 ). 
     Namely, when a regenerative operation is started, the bus voltage is increased and a charging-discharging control circuit  15  detects this increase and starts charging. If there are limits in a charging current, etc. and all power cannot be charged, the bus voltage  3  gradually begins to be increased and reaches the first stage voltage V 1 . Regenerated power is divided into powers in the above charging and regenerative resistance discharging from this time point. As a result, the regenerative operation is terminated without reaching the second stage voltage V 2  unless there is abnormality in a charging circuit, etc. 
     Accordingly, in the controller of the elevator having such a construction, no excessive burden is applied to the secondary battery  12  when the regenerated power is charged to the power accumulating device  11 . Therefore, a cheap power accumulating device having high energy saving efficiency can be used. Accordingly, it is possible to provide a controller of an elevator able to stably control the regenerated power by using a cheap secondary battery of a low capacity without damaging energy saving effects provided by charging. 
     Embodiment mode 2 
     In this embodiment mode 2, the charging-discharging state measuring device  14 A shown in FIG. 1 further includes a charging voltage measuring instrument for measuring a charging voltage of the secondary battery  12  of the power accumulating device  11  with respect to the embodiment mode 1. A measuring value of the bus voltage and a measuring value of the charging voltage are outputted to the regenerative control circuit  19 A as a measuring value in a charging-discharging state. The regenerative control circuit  19 A controls the ON pulse width of the gate  16  for regenerative current control in accordance with the measuring value of the bus voltage and the measuring value of the charging voltage. 
     Namely, the voltage of the secondary battery  12  at the charging time is different in accordance with the present SOC state, a circumferential temperature, etc. even when the secondary battery  12  is charged by the same electric current. Further, it is not preferable to unconditionally limit the charging by only the voltage at the charging time. However, in charging control, it is necessary to monitor this charging voltage and limit a charging amount (power, electric current). In this embodiment mode 2, a control operation is performed in consideration of such points. 
     The control of the regenerative control circuit  19 A in the embodiment mode 2 of this invention will next be explained with reference to the flow chart shown in FIG.  3 . 
     Similar to the embodiment mode 1, the regenerative control circuit  19 A, first, judges whether a measured bus voltage exceeds a second stage voltage V 2  or not. When the measured bus voltage exceeds the second stage voltage V 2 , the regenerative control circuit  19 A sets the duty of an ON pulse of the gate  16  for regenerative current control to B. Similar to the conventional case, a state for flowing all power through the regenerative resistor  17  is attained (steps S 201  to S 203 ). 
     In contrast to this, when no measured bus voltage exceeds the second stage voltage V 2 , it is next judged whether the charging voltage of the secondary battery  12  exceeds a predetermined value or not. If the charging voltage exceeds the predetermined value, duty=A is set as in the embodiment mode 1 (step S 204 →S 205 ), and regenerated power ½ to ⅓ times that in B flows through the regenerative resistor  17 . In contrast to this, if no charging voltage exceeds the predetermined value, the duty is set to 0 (step S 204 →S 206 ). The width of the ON pulse of the gate  16  for regenerative current control is controlled in accordance with such a set duty (step S 207 ). 
     Here, the predetermined value compared with the charging voltage is a value for performing a monitoring operation for protecting the battery at a charging time. When the charging voltage exceeds the predetermined value, excessive charging can be prevented by allotting one portion of the regenerated power to discharging using the regenerative resistor  17 . Further, the regenerated power is charged as much as possible and the secondary battery  12  can be protected while energy saving efficiency is secured as a whole. Accordingly, a cheap power accumulating device can be constructed. 
     In each of the following embodiment modes, the charging-discharging state measuring device  14 A shown in FIG. 1 has each of measuring instruments for measuring charging and discharging currents, charging and discharging voltages and a temperature of the power accumulating device  11 . The regenerative control circuit  19 A has a table in which these measuring values are inputted as charging-discharging state measuring values and duty according to each of the measuring values is set. The regenerative control circuit  19 A controls the width of an ON pulse of the gate  16  for regenerative current control in accordance with the duty set in the table. 
     In general, a charging voltage of the power accumulating device  11  tends to be suddenly increased just before excessive charging even when the same amount of the charging current continuously flows through the power accumulating device  11 . Accordingly, if a change in the charging voltage is measured, it is possible to perform a control operation in which charging is reduced and stopped, etc. at an early point in time. It is preferable in view of a battery life, etc. that no large charging is performed at a temperature except for a normal temperature. If the control operation is performed in fine conditions of a change in the charging voltage, SOC, temperature, etc. as well as the charging voltage, this control operation has a preferable influence on the life of the secondary battery  12  and it is more effective that these tables are made and the regenerative control is performed in plural modes. 
     Namely, the change in the charging voltage provided by charging is strictly caused by charging results. If a table for restraining an electric current is provided by temperature and SOC, the control operation can be clearly performed in further detail. The regenerated power is received as much as possible in the charging to the power accumulating device  11  to secure energy saving effects, but the control operation is performed such that no secondary battery  12  is excessively charged to protect its charging ability and secure the battery life. 
     Each of embodiment modes having a table and controlling the ON pulse width of the gate  16  for regenerative current control in accordance with duty set in the table will next be described. 
     Embodiment mode 3 
     As shown in FIG. 4, the regenerative control circuit  19 A has a table Ti setting duty therein in accordance with a charging current and a charging voltage. Duty corresponding to measuring values of the charging current and the charging voltage is calculated from the table Ti. The ON pulse width of the gate  16  for regenerative current control is controlled in accordance with this duty. 
     Embodiment mode 4 
     As shown in FIG. 5, the regenerative control circuit  19 A has plural tables T 1   a , T 1   b , T 1   c , - - - in which duty according to the temperature of the secondary battery  12  is set in accordance with the charging current and the charging voltage. 
     The regenerative control circuit  19 A selects a table according to the measuring temperature from these tables, and controls the ON pulse width of the gate  16  for regenerative current control in accordance with the duty set in the selected table. 
     Embodiment mode 5 
     As shown in FIG. 6, the regenerative control circuit  19 A has a table T 2  in which duty is set in accordance with the charging voltage and a changing amount of the charging voltage. The regenerative control circuit  19 A calculates duty set in the table T 3  on the basis of the charging voltage and the changing amount of the charging voltage, and controls the ON pulse width of the gate  16  for regenerative current control in accordance with the calculated duty. 
     Embodiment mode 6 
     As shown in FIG. 7, the regenerative control circuit  19 A has plural tables T 2   a , T 2   b , T 2   c , - - - in which duty according to a charging degree SOC is set in accordance with the charging voltage and a changing amount of the charging voltage. The regenerative control circuit  19 A selects a table according to this charging degree SOC, and calculates duty set in the selected table on the basis of the charging voltage and the changing amount of the charging voltage. The regenerative control circuit  19 A then controls the ON pulse of the above gate for regenerative current control in accordance with the calculated duty. 
     As mentioned above, according to this invention, the operation of the gate for regenerative current control is controlled in plural control modes in which an electric current or power flowing through the regenerative resistor is different in accordance with a charging state of the power accumulating device. Accordingly, it is possible to stably control the regenerated power by using a cheap secondary battery of a low capacity without damaging energy saving effects provided by charging.