Method and apparatus for allocating virtual inertia in photovoltaic cluster

Patent metadata

Field	Value
Publication number	US-12348043-B2
Application number	US-202217782999-A
Country	US
Kind code	B2
Filing date	Mar 28, 2022
Priority date	Mar 23, 2022
Publication date	Jul 1, 2025
Grant date	Jul 1, 2025

Abstract

The method includes: determining required virtual inertia based on a frequency change rate monitored at a grid connection point of a photovoltaic grid-connected system; obtaining values of indexes that affect virtual inertia provided by each virtual synchronous generator (VSG) control unit in a photovoltaic cluster of the photovoltaic grid-connected system; determining, by using a predetermined function equation, a function value corresponding to each index; and determining an allocation proportion of the required virtual inertia in each VSG control unit based on the function value corresponding to each index. A problem of difficult conversion between a plurality of kinds of performance during operation of a power system is resolved, the frequency change rate is suppressed to a certain extent, and a stable state is recovered quickly.

First claim

The invention claimed is:

1. A method for allocating virtual inertia in a photovoltaic cluster, comprising:
determining required virtual inertia based on a frequency change rate monitored at a grid connection point of a photovoltaic grid-connected system;
obtaining values of indexes that affect virtual inertia provided by each virtual synchronous generator (VSG) control unit in a photovoltaic cluster of the photovoltaic grid-connected system;
determining, by using a predetermined function equation, a function value corresponding to each index, wherein the function equation is determined by constructing an objective function, determining, based on the objective function, a membership function corresponding to each VSG control unit, establishing a small-signal model of the system, analyzing stability of parameters in the membership function with a root locus analysis method, and determining an optimal parameter;
determining an allocation proportion of the required virtual inertia in each VSG control unit based on the function value corresponding to each index; and
presetting a threshold of the frequency change rate, and starting virtual inertia control when the frequency change rate exceeds the threshold;
wherein the step of determining, by using a predetermined function equation, a function value corresponding to each index comprises:
determining, by using the following function equation, the function value corresponding to each index:

u
⁡
(
x
)

=

{

p
10

⁢

x
2

+

q
10

⁢
x

+

C
10

,

a
≤
x
≤
b

1
,

b
≤
x
≤
c

p
11

⁢

x
2

+

q
11

⁢
x

+

C
11

,

c
≤
x
≤
d

wherein x represents the index; u(x) represents the function value; p 10 , q 10 , C 10 , p 11 , q 11 , and C 11 represent determined parameters; and a, b, c, and d represent boundaries for dividing a working region of the energy storage device in a state of charge (SOC), wherein a section from a to b represents a discharging state of the energy storage device, a section from b to c represents a normal state of the energy storage device, and a section from c to d represents a charging state of the energy storage device.

2. The method for allocating virtual inertia in a photovoltaic cluster according to claim 1 , wherein the obtaining values of indexes that affect virtual inertia provided by each VSG control unit in a photovoltaic cluster of the photovoltaic grid-connected system comprises:
obtaining a residual energy storage capacity of a supercapacitor, rated power of a converter, and adjustable charge and discharge power of an energy storage device for a photovoltaic unit corresponding to each VSG control unit in the photovoltaic cluster of the photovoltaic grid-connected system.

3. The method for allocating virtual inertia in a photovoltaic cluster according to claim 2 , wherein
the step of determining an allocation proportion of the required virtual inertia in each VSG control unit based on the function value corresponding to each index comprises:
determining, based on a ratio of a sum of the function value corresponding to each index in each photovoltaic unit, an amount of the virtual inertia allocated to each VSG control unit.

4. The method for allocating virtual inertia in a photovoltaic cluster according to claim 3 , wherein the step of determining required virtual inertia based on a frequency change rate of a photovoltaic grid-connected system comprises:
determining the required virtual inertia by using the following function:

F
=

{

k
1

⁢

e

df
/
dt

+

k
2

+

H
0

❘
"\[LeftBracketingBar]"

df
/

Assignees

• State Grid Hebei Electric Power Co Ltd Res Institute
• State Grid Hebei Electric Power Co Ltd
• State Grid Corp China

Inventors

• Fan Hui
• Liang Jifeng
• Luo Peng
• Li Tiecheng
• Zeng siming
• Zang Qian
• Wang Leibao

Classifications

• H02J2103/30

  Simulating, planning, modelling, reliability check or computer assisted design [CAD] of electric power networks · CPC title

• H02J2101/24

  Photovoltaics · CPC title

• H02J3/00142

  Oscillations concerning frequency · CPC title

• H02J3/28 Primary

  Arrangements for balancing of the load in networks by storage of energy · CPC title

• Y02E10/56

  Power conversion systems, e.g. maximum power point trackers · CPC title