Patent ID: 11967909
Assignee: DAIKIN INDUSTRIES, LTD.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H | IPC H

Claim 8:
9. A power conversion device comprising:
a converter unit that converts a single-phase alternating current voltage Vin and outputs a rectified voltage;
a first power source line connected to a positive output end of the converter unit;
a second power source line connected to a negative output end of the converter unit;
a PWM-controlled inverter unit having
a positive input end connected to the positive output end of the converter unit via the first power source line, and
a negative input end connected to the negative output end of the converter unit via the second power source line,
the PWM-controlled inverter unit outputting an alternating current voltage converted from the rectified voltage;

a buffer circuit connected between the first power source line and the second power source line, the buffer circuit including a buffer circuit switch and a capacitor;
a charging circuit that charges the buffer circuit with the rectified voltage in a first duration, the charging circuit including an inductor, a charging circuit diode, and a charging circuit switch,
an anode of the charging circuit diode being connected between the inductor and the charging circuit switch, and a cathode of the charging circuit diode being connected between the buffer circuit switch and the capacitor; and

a current blocking unit connected between the charging circuit and the buffer circuit, the current blocking unit including a current blocking unit diode,
the power conversion device being configured such that
in the first duration where an absolute value of an instantaneous value of the single-phase alternating current voltage Vin is higher than a direct current voltage command value Vdc*, an output end of the buffer circuit is cut off from the first power source line, a switching pattern of PWM control of the PWM-controlled inverter unit is selected such that a direct current voltage converted from an output voltage of the PWM-controlled inverter unit at a time of voltage saturation of the PWM-controlled inverter unit becomes equal to the direct current voltage command value Vdc*, a first conversion operation of supplying power to the PWM-controlled inverter unit by the rectified voltage having been output from the converter unit is performed, and the buffer circuit is charged by the rectified voltage, and
in a second duration section where the absolute value of the instantaneous value of the single-phase alternating current voltage Vin is equal to or less than the direct current voltage command value Vdc*, the output end of the buffer circuit is connected to the first power source line, a switching pattern of PWM control of the PWM-controlled inverter unit is selected such that the direct current voltage converted from the output voltage of the PWM-controlled inverter unit at a time of voltage saturation of the PWM-controlled inverter unit becomes equal to the direct current voltage command value Vdc*, and a second conversion operation of supplying power from the buffer circuit to the PWM-controlled inverter unit is performed,

a first duty drec of a current flowing from the PWM-controlled converter unit not through the buffer circuit, a second duty dc of a current flowing through the buffer circuit, and a third duty dz of a zero-phase current flowing in the PWM-controlled inverter unit satisfy

drec+dc+dz=1

and
when a maximum value of the single-phase alternating current voltage Vin is Vm, an angular velocity of the single-phase alternating current voltage Vin is ω, and time is t,
the first duty drec and the second duty dc in a period of the first conversion operation are expressed by, d
      rec
    
    =
    
      
        
          V
          dc
        
        *
      
      
        
          V
          m
        
        ⁢
        
          
          
            sin
            ⁡
            
              (
              
                ω
                ⁢
                
                  
                
                ⁢
                t
              
              )
            
          
          
        
      
    
  

  
    
      
        d
        c
      
      =
      0
    
    ,
  

the first duty drec and the second duty dc in a period of the second conversion operation are expressed by, d
      rec
    
    =
    0
  

  
    
      
        d
        c
      
      =
      
        
          
            V
            dc
          
          *
        
        
          V
          m
        
      
    
    ,
  

and
the PWM-controlled inverter unit is PWM-controlled based on phase voltage command values Vu*, Vv*, and Vw*, the first duty drec, the second duty dc, and the third duty dz.