Patent ID: 11901733
Assignee: QINGYUAN POWER SUPPLY BUREAU OF GUANGDONG POWER GRID CORPORATION
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  Y | IPC H

Claim 0:
1. A hybrid passive power filter, comprising: a series passive harmonic isolation unit, a parallel passive filtering unit, and a harmonic load;
wherein an input terminal of the series passive harmonic isolation unit is electrically connected to a power grid, an output terminal of the series passive harmonic isolation unit is electrically connected to a first terminal of the harmonic load directly, and the series passive harmonic isolation unit is configured to isolate harmonics; wherein an input terminal of the parallel passive filtering unit is electrically connected to the output terminal of the series passive harmonic isolation unit, an output terminal of the parallel passive filtering unit is electrically connected to a second terminal of the harmonic load directly, and the parallel passive filtering unit is configured to filter out harmonics; and
wherein the parallel passive filtering unit comprises at least one of: a third-order passive filtering branch and a fifth-order passive filtering branch, the third-order passive filtering branch and the fifth-order passive filtering branch which are connected in parallel comprise one terminal which is electrically connected to the output terminal of the series passive harmonic isolation unit and comprise another terminal which is electrically connected to the second terminal of the harmonic load;
wherein the third-order passive filtering branch comprises a first inductor and a first capacitor;
wherein a first terminal of the first inductor is electrically connected to the output terminal of the series passive harmonic isolation unit, a second terminal of the first inductor is electrically connected to a first terminal of the first capacitor, and a second terminal of the first capacitor is electrically connected to the second terminal of the harmonic load; and
wherein the fifth-order passive filtering branch comprises a second inductor and a second capacitor;
wherein a first terminal of the second inductor is electrically connected to the first terminal of the first inductor, a second terminal of the second inductor is electrically connected to a first terminal of the second capacitor, and a second terminal of the second capacitor is electrically connected to the second terminal of the first capacitor;
wherein an equivalent impedance of the parallel passive filtering unit is less than an equivalent impedance of the series passive harmonic isolation unit,
wherein equivalent impedance of the parallel passive filtering unit at an n-th harmonic satisfies a following relationship:, Z
   F
   
    (
    n
    )
   
  
  =
  
   j
   ⁢
   
    1
    n
   
   ×
   
    
     
      (
      
       
        n
        2
       
       -
       9
      
      )
     
     ⁢
     
      (
      
       
        n
        2
       
       -
       
        2
        ⁢
        5
       
      
      )
     
     ⁢
     ω
     ⁢
     
      l
      1
     
     ⁢
     ω
     ⁢
     
      l
      2
     
    
    
     
      
       (
       
        
         n
         2
        
        -
        9
       
       )
      
      ⁢
      ω
      ⁢
      
       l
       1
      
     
     +
     
      
       (
       
        
         n
         2
        
        -
        
         2
         ⁢
         5
        
       
       )
      
      ⁢
      ω
      ⁢
      
       l
       2
      
     
    
   
  
 

wherein ω denotes a resonant angular frequency, l1 denotes an inductance of the first inductor, and l2 denotes an inductance of the second inductor,
wherein a harmonic current of the harmonic load satisfies the following formula:, I
    s
    
     (
     n
     )
    
   
   =
   
    
     
      
       Z
       F
       
        (
        n
        )
       
      
      
       
        Z
        F
        
         (
         n
         )
        
       
       +
       
        Z
        s
       
       +
       
        Z
        I
        
         (
         n
         )
        
       
      
     
     ⁢
     
      I
      L
      
       (
       n
       )
      
     
    
    +
    
     
      U
      s
      
       (
       n
       )
      
     
     
      
       Z
       F
       
        (
        n
        )
       
      
      +
      
       Z
       s
      
      +
      
       Z
       I
       
        (
        n
        )
       
      
     
    
   
  
  ,
 

wherein ZF(n) denotes the equivalent impedance of the parallel passive filtering unit at the n-th harmonic ZI(n) denotes the equivalent impedance of the series passive harmonic isolation unit at the n-th harmonic, Zs denotes an equivalent impedance of the power supply, and Us(n) denotes a background harmonic voltage in the power supply.