Model predictive controller for autonomous hybrid microgrids

Patent metadata

Field	Value
Publication number	US-10651654-B2
Application number	US-201816179805-A
Country	US
Kind code	B2
Filing date	Nov 2, 2018
Priority date	Nov 7, 2017
Publication date	May 12, 2020
Grant date	May 12, 2020

Abstract

A control system is disclosed with a control strategy for autonomous multi-bus hybrid microgrids based on Finite-Control-Set Model Predictive Control (FCS-MPC). The control loops are expedited by predicting the future states and determining the optimal control action before switching signals are sent to converters/inverters. The method eliminates PI and PWM components, and offers 1) accurate PV maximum power point tracking (MPPT) and battery charging/discharging control, 2) DC and AC bus voltage/frequency regulation, and 3) precise and flexible power sharing control among multiple DERs.

First claim

What is claimed is:

1. A method for controlling a microgrid, comprising:
collecting power data from a multi-bus hybrid microgrid, wherein the multi-bus hybrid microgrid comprises at least a converter or an inverter;
predicting one or more future states of the microgrid from present and past states of the microgrid;
determining a predetermined control action before switching signals are sent to the converter or inverter using Finite-Control-Set Model Predictive Control (FCS-MPC) during autonomous mode by switching a circuit breaker at a point of common coupling (PCC), wherein the VSI is a three-phase two-level inverter with three legs and two switches in each leg; and
predicting next PV power as:
P PV,1 ( k+ 1)= I PV,1 ( k+ 1)· V PV,1 ( k +1)

P PV,0 ( k+ 1)= I PV,0 ( k+ 1)· V PV,0 ( k+ 1),

where P PV,1 (k+1) and P PV,0 (k+1) are next-step predictions of PV power when a converter switch is “ON” and “OFF”, respectively, I PV,1 (k+1) and I PV,0 (k+1) are next-step predictions of PV current when the converter switch is “ON” and “OFF”, respectively, V PV,1 (k+1) and V PV,0 (k+1) are next-step predictions of PV voltage when the converter switch is “ON” and “OFF”, respectively, and k is a discrete control step sequence.

2. The method of claim 1 , comprising minimizing a cost function before sending control commands to minimize error between an objective and a reference target value.

3. The method of claim 1 , comprising determining the FCS-MPC based on a discrete-time state space of a converter/inverter as:
x ( k+ 1)= Ax ( k )+ Bu ( k )
y ( k+ 1)= Cx ( k )+ Du ( k )
where x is the state variable matrix, u is the control input, y is the output, k denotes the present discrete control step sequence, and A, B, C, D are the state-space matrices.

4. The method of claim 1 , comprising a cost function embodies reference values, control actuations, and future states and then minimized subject to certain predefined constraints.

5. The method of claim 1 , comprising a cost function is minimized subject to constraints of:
J=f [ x ( k ), u ( k ), . . . , x ( k+N ), u ( k+N )]
where J is a control cost and N is the length of predicting horizon.

6. The method of claim 1 , comprising extracting maximum photovoltaic (PV) power using MPPT.

7. The method of claim 1 , comprising determining a maximum power reference (P MPP ) in real time and based on the state space of a converter, a next sample time value of the PV current (I PV (k+1)) and voltage (V PV (k+1)), where T S denotes the sample time, L PV is a total filter inductance of a PV converter, V PV (k) and I PV (k) are present PV voltage and current, V PV (k−1) denotes a previous PV voltage, and k is a discrete control step sequence, further comprising determining:

I

PV
,
1

⁡

(

k
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=

I
PV

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k
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+

T
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PV

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V
PV

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(
k
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-

V
PV

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(

k
-
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I

PV
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0

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(

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PV

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PV

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k
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PV

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.

8. The method of claim 1 , comprising determining a cost funct

Assignees

• Yi Zhehan
• Wang Yishen
• Huang Bibin
• Shi Di
• Wang Zhiwei
• Hou Tingting
• State Grid Corp China
• Geiri Co Ltd
• State Grid Jiangxi Electric Power Co

Inventors

• Yi Zhehan
• Wang Yishen
• Huang Bibin
• Shi Di
• Wang Zhiwei
• Hou Tingting

Classifications

• H02J3/003 Primary

  Load forecast, e.g. methods or systems for forecasting future load demand · CPC title

• H02M7/5387

  in a bridge configuration · CPC title

• H02J3/002

  Flicker reduction, e.g. compensation of flicker introduced by non-linear load · CPC title

• H02J3/38

  Arrangements for feeding a single network from two or more generators or sources in parallel; Arrangements for feeding already energised networks from additional generators or sources in parallel · CPC title

• G05F1/67

  to the maximum power available from a generator, e.g. from solar cell · CPC title