Wind turbine hybrid microgrid system and controller therefor

Patent metadata

Field	Value
Publication number	US-12100964-B2
Application number	US-202418620060-A
Country	US
Kind code	B2
Filing date	Mar 28, 2024
Priority date	Oct 27, 2022
Publication date	Sep 24, 2024
Grant date	Sep 24, 2024

Abstract

A system and a method for controlling a hybrid microgrid system (HMS) is disclosed. The HMS includes a WTG, an RSC, a GSC, a DC-link connecting the RSC and the GSC, a PV system that outputs a DC current to the DC-link, a rechargeable battery, a bidirectional BBC connected between the DC-link and the rechargeable battery, and a controller. The method for controlling the HMS includes: preparing a definition set including a characteristic element ci and equations defining desired value ci*, a fractional order sliding mode surface ζi, and a control law element uicnt; monitoring ci(t) and the HMS status; calculating the equations based on monitored information; and controlling the HMS based on the uicnt(t) calculated and in accordance with a global sliding mode control with fractional order terms. The ζi comprises a fractional time integral and fractional time derivative of ei(t), where ei(t)=ci(t)−ci*(t). The uicnt(t) satisfiesζi(t)⁢d⁢ζi(t)dt<0,when ζi(t)≠0.

First claim

The invention claimed is:

1. A controller of a wind turbine hybrid microgrid system (HMS) comprising: a renewable energy source including a wind turbine (WT) generator and an electric generator; a grid side converter (GSC) configured to output a power to a point of common coupling (PCC); a DC-link configured to receive a power from the renewable energy source and to supply a power to the GSC; a rechargeable battery configured to exchange a power via the DC-link; a load configured to receive a power via the PCC; a utility grid configured to exchange power via the PCC; and a controller comprising: a processor; a memory; a bus-line; and I/O port,
wherein the controller is configured to control the HMS by executing a program installed in the memory and in accordance with a global sliding mode control with fractional order terms (GSMCFO) method,
wherein the program comprises a definition set customized for the HMS and to be referred in applying the GSMCFO method to the HMS,
wherein the definition set comprises: a characteristic element c i to be measured; and equations defining a desired value c i * of the characteristic element c i , a fractional order sliding mode (FOSM) surface ζ i of the characteristic element c i , and a control law element u i cnt of the characteristic element c i ,
wherein the controller is further configured to
monitor the characteristic element c i (t) and a related status of the HMS,
calculate at least one of the equations defined in the definition set based on the characteristic element c i (t) monitored and the related status of the HMS monitored, and
control the HMS based on the control law element u i cnt (t) calculated, and in accordance with the GSMCFO,
wherein the equation defining the FOSM surface ζ i (t) for the characteristic element c i (t) comprises a fractional time integral of a tracking error e i (t) and a fractional time derivative of the tracking error e i (t), wherein the tracking error e i (t) for the characteristic element c i (t) is defined as,
e i ( t )= c i ( t )− c i *( t ),

wherein the equation defining the control law element u i cnt (t) is configured to satisfy a condition

ζ
i

(
t
)

⁢

d
⁢

ζ
i

(
t
)

dt

<
0

,

so far as ζ i (t) is not zero.

2. The controller of claim 1 , wherein the definition set further comprises: a minimum value SOC min and a maximum value SOC max of the state of charge (SOC) of the rechargeable battery; and equations defining a power imbalance ΔP and a power balance condition of the HMS, given respectively as
Δ P=P re +P ug −P dem −P b ,

Δ P= 0,

wherein P re represents a total power generated by the renewable energy source, P ug , a grid power exchanged between the utility grid and the PCC, P dem , a load demand, P b , a battery power exchanged between the rechargeable battery and the DC-link,
and wherein the controller is further configured to
monitor elements required to calculate a power imbalance ΔP and a SOC,
calculate the power imbalance ΔP with the equation given in the definition set, and
controlling the battery power P b and the grid power P ug to satisfy and maintain the power balance condition, under a restriction that the SOC of the rechargeable battery satisfies a condition,
SOC min ≤SOC≤SOC max .

3. The controller of claim 2 , wherein the electric generator comprises a rotor and a stator;
a rotor side converter (RSC) configured to receive an AC power from the electric generator and output an RSC output DC current to the DC-link;
a solar photovoltaic (PV) system configured to output a PV output DC current to the DC-link; and
a bidirectional buck-boost converter (BBBC) connected between the DC-link and the rechargeable battery and configured to control a power exchanged between the rechargeable battery and the DC-link, and
wherein the definition set further comprises an equation defining an equivalent control law element u i eqv for the characteristic element c i , wherein the equivalent control law element u i eqv comprises a maximum disturbance term R t 1-μ δ i , representing a possible maximum value of a lumped external disturbances and parametric perturbations to the tracking error e i (t), wherein, R t 1-μ represents a Riemann-Liouville fractional integration, and δ i , a positive function,
and wherein the equation defining the control law element u i cnt (t) comprises a function SG(ζ i (t)) given by a signum function sgn(ζ i (t)) or one of its smooth approximations including

tanh
⁡
(

ζ
i

(
t
)

θ

)

,

wherein, θ(>0),
and wherein the characteristic element c 1 is an angular frequency ω r , of the WT, and the characteristic element c 2 is a d-axis stator current I ds ,
wherein the desired value ω r * for the angular frequency ω r of the WT is defined as,

c
1
*

(
t
)

=

ω
r
*

=

λ
*

⁢

V
w

R

,

wherein λ* denotes a desired tip speed ratio, giving a maximum power coefficient for the turbine with a blade radius R, at a wind speed V w , and wherein,
the desired value I ds * for the d-axis stator current I ds of the rotor is given as,
c 2 *( t )= I ds *=0

and wherein the equations defining the FOSM surfaces ζ i (t) for the characteristic elements c i (i=1, 2) are given as,
ζ 1 ( t )= k 1 R t μ e 1 ( t )+σ 1 R t 1-μ e 1 ( t )+ R t 2-μ e 1 ( t ),

ζ 2 ( t )= k 1 R t μ e 2 ( t )+ R t 1-μ e 2 ( t ),

wherein, 0<μ<1, k 1 , k 2 , and σ 1 are positive constants, R t μ denotes a Riemann-Liouville fractional integration, R t 1-μ and R t 2-μ denote Riemann-Liouville fractional derivations,
and wherein the equivalent control law element u 1 eqv (t) a

Assignees

• Univ King Fahd Pet & Minerals

Inventors

• Khalid Muhammad
• Maaruf Muhammad

Classifications

• H02J2101/28

  Wind energy · CPC title

• H02J2101/24

  Photovoltaics · CPC title

• H02M3/1582

  Buck-boost converters (H02M3/1584 takes precedence) · CPC title

• H02J3/32

  using batteries or super capacitors with converting means · CPC title

• H02M5/4585

  having a rectifier with controlled elements · CPC title