Hybrid microgrid system for wind power electrical generation

12119,659

18/620141

March 28, 2024

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) satisfies [mathematical expression included] when ζi(t)≠0.

KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS (Dhahran, SA)

KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS (Dhahran, SA)

1. A hybrid microgrid system (HMS) for wind power electrical generation comprising: a wind turbine (WT) 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 WT and the electric generator and to supply a power to the GSC; a rechargeable battery configured to exchange a power between 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, and 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 (i of the characteristic element c i , and a control law element u i cnt of the characteristic element c i , and 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 status of the HMS monitored, and control the HMS based on the control law element u i cnt (t) calculated, 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 [mathematical expression included] so far as ζ i (t) is not zero.

2. The hybrid microgrid system of claim 1 , wherein the definition set further comprises: a minimum value SOC min in 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 WT and the electric generator, 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, wherein the controller is further configured to monitor elements required to calculate a power imbalance ΔP and a SOC, calculate a power imbalance ΔP with the equation given in the definition set, and control 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 hybrid microgrid system of claim 2 , wherein the WT comprises: a wind turbine generator and 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, 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 [mathematical expression included]  wherein, θ(>0).

4. The hybrid microgrid system of claim 3 , 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, [mathematical expression included] 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 , 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 wherein the equations defining the FOSM surfaces ζ i (t) for the characteristic elements c 1 (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 2 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, wherein the equivalent control law element u 1 eqv (t) and the control law element u i cnt (t) of the angular frequency ω r are given by q-axis stator voltages V qs eqv (t) and V qs cnt (t), and defined respectively as, [mathematical expression included] wherein the equivalent control law element u 2 eqv (t) and the control law element u 2 cnt (t) of the d-axis stator current I ds of the rotor are given by d-axis stator voltages V ds eqv (t) and V ds cnt (t), and defined respectively as [mathematical expression included] wherein α is given by [mathematical expression included] wherein P denotes a number of pole pairs of the rotor, Λ r , a rotor flux, J, an inertia of mechanical shaft of the wind turbine generator, L q , a q-axis self-inductance of the stator, Rs, a stator resistance, I qs , a q-axis stator current, Λ r , a rotor flux, L d , a d-axis self-inductance of the stator, R t 1-μ δ 1 and R t 1-μ δ 2 represent the maximum disturbance terms, α ∈ (0, 1), i and γ i (i=1, 2) are positive constants.

5. The hybrid microgrid system of claim 3 , wherein the DC-link further comprises a DC-bus and a DC-link capacitor, and wherein the characteristic element c 3 is a DC-link voltage V dc , the desired value V dc * defined for the DC-link voltage V dc is given as [mathematical expression included] wherein V pv MPPT represents an output voltage of the PV system under a maximum power point tracking (MPPT) operation, V dc min , V dc max and V dc nom represent a minimum allowable value, a maximum allowable value, and a nominal value of the DC-link voltages, each predetermined respectively, the equation defining the FOSM surfaces ζ 3 (t) of the DC-link voltage is given as, ζ 3 (t)= k 3 R t μ e 3 (t)+ R t 1-μ e 3 (t) wherein, μ ∈ (0, 1) and k 3 are positive constants, R t 1-μ denotes a Riemann-Liouville fractional integration, R t 1-μ denotes a Riemann-Liouville fractional derivation, wherein the equations defining the equivalent control law element u 3 eqv (t) and the control law element u 3 cnt (t) of the DC-link voltage V dc are given by d-axis AC output currents I d eqv (t) and I d cnt (t) from the GSC, and defined respectively as, [mathematical expression included] wherein C dc denotes a capacitance of the DC-link capacitor, V d , a voltage of the AC output from the GSC, P w , an output power from the RSC, I pv , an output current from the PV system, D, a duty cycle ratio of the BBBC, I b , a battery output current, R t 1-μ δ 3 is the maximum disturbance term, α ∈ (0, 1), 3 and γ 3 are positive constants.

6. The hybrid microgrid system of claim 3 , wherein the GSC is further configured to output an AC output to a point of common coupling (PCC) via a grid side filter, wherein the characteristic elements c i (t) (i=4, 5) are a d-axis AC current I d (i=4) of the AC output from the GSC, and a q-axis AC current I q (i=5) of the AC output from the GSC for, respectively, the desired values defined for the d-axis AC current and the q-axis AC current are given respectively as [mathematical expression included] c 5 *(t)= I q *=0, wherein P dem and P ug represent a power demand at the load and a power exchanged between the PCC and the utility grid, respectively, wherein P ug >0, when provided from the utility grid to the PCC, P ug <0, when provided from the GSC to the utility grid, V d , a d-axis AC voltage of the AC output from the GSC, the equations defining the FOSM surfaces ζ i (t) for the d-axis AC current I d (i=4) and the q-axis AC current I q (i=5) are given respectively as, ζ 4 =k 4 R t μ e 4 (t)+ R t 1-μ e 4 (t), ζ 5 (t)= k 5 R t μ e 4 (t)+ R t 1-μ e 5 (t), wherein μ ∈ (0, 1), k 4 , and k 5 are positive constants, R t μ and R t 1-μ each denotes a Riemann-Liouville fractional integration and a Riemann-Liouville fractional derivation, respectively, wherein the equations defining the equivalent control law element u 4 eqv (t) and the control law element u 4 cnt (t) of the d-axis AC current I d are given by d-axis AC voltages V d eqv (t) and V d cnt (t) of the AC output from the GSC, and defined respectively as, [mathematical expression included] wherein the equations defining the equivalent control law element u 5 eqv (t) and the control law element u 5 cnt (t) of the q-axis AC current I q are given by q-axis AC voltages V q eqv (t) and V q cnt (t) of the AC output from the GSC, and defined respectively as, [mathematical expression included] wherein L f and R f denote a grid side filter inductance and a grid side filter resistance, respectively, U d and U q , a d-axis and a q-axis voltages at a point of common coupling (PCC), respectively, ωg, an electrical angular frequency of the AC output from the GSC, R t 1-μ δ i ,(i=4, 5) are the maximum disturbance terms, α ∈ (0, 1), i and γ i (i=4, 5) are positive constants.

7. The HMS of claim 3 , wherein the BBBC is configured to facilitate charging of the rechargeable battery while operating as a buck converter, and to facilitate discharging to the DC-link while operating as a boost converter, and wherein the characteristic element c 1 (i=6) is a battery current I b , the desired value I b * defined for the battery current I b is given as, [mathematical expression included] wherein P re represents a sum of powers generated by the WT, P ug a power supplied by the utility grid, P dem , a load demand, and V b , a battery voltage, the equation defining the FOSM surfaces ζ 6 (t) of the battery current is given as, ζ 6 (t)= k 6 R t 1-μ e 6 + R t 1-μ e 6 , wherein, μ ∈ (0, 1) and k 6 are positive constants, R t 1-μ denotes a Riemann-Liouville fractional integration, R t 1-μ denotes a Riemann-Liouville fractional derivation, wherein the equations defining the equivalent control law element u 6 eqv (t) and the control law element u 6 cnt (t) of the battery current I b are given by duty cycles D eqv (t) and D cnt (t) of the BBBC, and defined respectively as, [mathematical expression included] wherein L b denotes a battery inductance, V b , a battery voltage, R b , a battery resistance, V dc , a DC-link voltage, R t 1-μ δ 6 represents the maximum disturbance term, α ∈ (0, 1), 6 and γ 6 are positive constants.

2021101279 May 2021
114172398 March 2022
202041048086 November 2020

Ahmad Aziz Al Alahmadi, et al., “Hybrid Wind/PV/Battery Energy Management-Based Intelligent Non-Integer Control for Smart DC-Microgrid of Smart University”, IEEE Access, vol. 9, Jul. 9, 2021, pp. 98948-98961. cited by applicant
Bo Yang, et al., “Passivity-based fractional-order sliding-mode control design and implementation of grid-connected photovoltaic systems”, Journal of Renewable and Sustainable Energy, vol. 10, Issue 4, Jul. 2, 2018, pp. 1-21. cited by applicant
Abdel-Raheem Youssef, et al., Advanced multi-sector P&O maximum power point tracking technique for wind energy conversion system, International Journal of Electrical Power and Energy Systems, vol. 107, 2019, pp. 89-97. cited by applicant
Sofia Boulmrharj, et al., Online battery state-of-charge estimation methods in micro-grid systems, Journal of Energy Storage, vol. 30, 2020, pp. 1-18. cited by applicant
Jing Wang, et al., “Fractional order sliding mode control via disturbance observer for a class of fractional order systems with mismatched disturbance”, Mechatronics, vol. 53, 2018, pp. 8-19. cited by applicant
Yuanlong Xie, et al., “Coupled fractional-order sliding mode control and obstacle avoidance of a four-wheeled steerable mobile robot”, ISA Transactions, vol. 108, 2021, pp. 282-294. cited by applicant
Boubacar Housseini, et al., “Robust Nonlinear Controller Design for On-Grid/Off-Grid Wind Energy Battery-Storage System”, IEEE Transactions on Smart Grid, vol. 9, No. 6, Nov. 2018, pp. 5588-5598. cited by applicant
Nasrin Chatrenour, et al., “Improved double integral sliding mode MPPT controller based parameter estimation for a stand-alone photovoltaic system”, Energy Conversion and Management, vol. 139, 2017, pp. 97-109. cited by applicant
Mohammad Kamruzzaman Khan Prince, et al., “Modeling, Parameter Measurement, and Control of PMSG-based Grid-connected Wind Energy Conversion System”, Journal of Modern Power Systems and Clean Energy, vol. 9, No. 5, Sep. 2021, pp. 1054-1065. cited by applicant

edspgr.12119659