Method of generalized synchronous optimal pulse width modulation for renewable energy station and system thereof

A generalized synchronous optimal pulse width modulation (PWM) system for a renewable energy station (RES), comprising:

• a data acquisition module, configured to:
• acquire steady-state operating information of a converter cluster in the RES;
• a problem construction module, configured to:
• construct a coordinated power quality optimization modulation equation based on the steady-state operating information, and add constraints to the coordinated power quality optimization modulation equation based on fundamental volt-second characteristics and timing, to obtain an optimization problem;
• wherein, the coordinated power quality optimization modulation equation is expressed as follows:
• Min
• ⁢
• I
• T
• ⁢
• H
• ⁢
• D
• ⇒
• ∑
• n
• =
• 5
• L
• i
• n
• 2
• ⇒
• ∑
• n
• =
• 5
• L
• (
• ∑
• j
• =
• 1
• N
• j
• i
• n
• ,
• j
• )
• 2
• ⇒
• ∑
• n
• =
• 5
• L
• (
• ∑
• j
• =
• 1
• N
• j
• K
• j
• n
• ⁢
• v
• n
• ,
• j
• )
• 2
• ;
• wherein, ITHD represents total harmonic distortion of current;
• L represents inductive reactance of a line and filter;
• n represents a harmonic order;
• in represents lumped harmonic current;
• Ni represents the total number of sub-units;
• in,j represents nth harmonic current of a jth sub-unit;
• Kj represents a converter coefficient;
• and vn,j represents nth harmonic voltage of the jth sub-unit;
• wherein, the optimization problem is expressed as follows:
• wherein, relevant restrictions (constraints) are added to a final optimization problem, as shown below:
• Minimize
• ⁢
• EF
• =
• ∑
• n
• =
• 5
• L
• (
• ∑
• j
• =
• 1
• N
• j
• K
• j
• ⁢
• v
• n
• ,
• j
• n
• )
• 2
• ︸
• PCC
• ,
• curr
• .
• +
• ∑
• j
• =
• 1
• N
• j
• ℒ
• i
• ⁢
• ∑
• n
• =
• 5
• L
• (
• v
• n
• ,
• j
• n
• )
• 2
• ︸
• Unit
• ,
• curr
• .
• ;
• Subject
• ⁢
• to
• ⁢
• 2
• ⁢
• V
• d
• ⁢
• c
• ,
• 1
• π
• ⁢
• ∑
• i
• =
• 1
• N
• (
• -
• 1
• )
• i
• +
• 1
• ⁢
• cos
• ⁡
• (
• θ
• i
• ,
• 1
• )
• =
• M
• 1
• ,
• 1
• ;
• …
• ⁢
• 2
• ⁢
• V
• d
• ⁢
• c
• ,
• j
• π
• ⁢
• ∑
• i
• =
• 1
• N
• (
• -
• 1
• )
• i
• +
• 1
• ⁢
• cos
• ⁡
• (
• θ
• i
• ,
• j
• )
• =
• M
• 1
• ,
• j
• ;
• 0
• <
• θ
• 1
• ,
• j
• <
• θ
• 2
• ,
• j
• ⁢
• …
• <
• θ
• N
• ,
• j
• <
• π
• 2
• ;
• wherein, EF represents a cost evaluation function;
• L represents the inductive reactance of the line and filter;
• n represents the harmonic order;
• Nj represents the total number of sub-units;
• Kj represents the converter coefficient;
• vn,j represents the nth harmonic voltage of the jth sub-unit;
• i represents a considered upper harmonic limit;
• Vdc,1 represents a first DC bus voltage;
• Vdc,j represents a jth DC bus voltage;
• M1,1 represents a desired fundamental modulation index of a first sub-unit;
• M1, represents a desired fundamental modulation index of the jth sub-unit;
• θi,j represents an ith switching time point of the jth sub-unit;
• and θN,j represents an Nth switching time point of the jth sub-unit;
• a problem solving module, configured to:
• solve the optimization problem using an optimization solver to obtain an optimal switching pulse sequence for the converter cluster at an ideal operating point;
• and
• a sequence extension module, configured to:
• solve the optimization problem using a gradient descent algorithm to obtain a pulse width modulation lookup table for the converter cluster, extended over a set modulation index range from the ideal operating point, and distribute the same to each converter.