US 12,500,414 B1Granted

System and method for voltage compensation and state of charge-assisted power sharing in DC microgrids

AssigneeKing Fahd University of Petroleum and Minerals

InventorsMd Shafiul Alam, Fahad Saleh Al-Ismail, Md Shafiullah, Mohammad Ali Yousif Abido

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Abstract

A control system for a direct current (DC) microgrid is described. The control system includes a DC bus with a positive bus line and a negative bus line, DC battery circuits with a positive coupler connected to the positive bus line and a negative coupler connected to the negative bus line, switches including a control input terminal located in each DC battery circuit, a distributed generator circuit connected to the DC bus, a constant load power circuit connected to the DC bus, a computing device connected to each control input terminal, the DC bus, the distributed generator circuit and the constant load power circuit. The computing device includes an electric circuitry, a memory, and at least one processor to determine a DC bus voltage, determine the SoC of the DC battery circuits, generate PWM signals that control the DC bus voltage, and balance the SoC of the DC battery circuits.

Claims19

Dependent claims

A control system for a direct current (DC) microgrid, comprising:

a DC bus configured with a positive bus line and a negative bus line;
a plurality of DC battery circuits each configured with a positive coupler and a negative coupler, wherein each positive coupler is connected to the positive bus line and each negative coupler is connected to the negative bus line;
a plurality of switches located in each DC battery circuit, wherein each switch includes a control input terminal;
a distributed generator circuit connected to the DC bus;
a constant load power circuit connected to the DC bus;
and
a computing device connected to each control input terminal, the DC bus, the distributed generator circuit and the constant load power circuit, wherein the computing device includes an electric circuitry, a memory configured to store program instructions, and at least one processor configured to execute the program instructions to:
determine a DC bus voltage of the DC bus,
determine a state of charge (SoC) of each of the plurality of DC battery circuits, and
generate phase width modulation (PWM) signals which:
control the DC bus voltage, and
balance the SoC of the DC battery circuits;
and
a proportional integral (PI) controller connected to the computing device, wherein the computing device is configured to:
receive a power reference value Pdgref from the distributed generator circuit;
receive a voltage reference value Vdg from the distributed generator circuit;
calculate a distributed generator current reference value 1Vdg;
receive a distributed generator current Idg from the distributed generator circuit;
calculate a distributed generator error between the current reference value 1Vdg and the distributed generator current Idg;
and
apply the distributed generator error to the PI controller, wherein the PI controller is configured to generate the PWM signals to actuate a boost converter switch.

18 more elements

A method of controlling a DC bus voltage and a state of charge (SoC) balance in a DC microgrid having a plurality of DC battery circuits, each DC battery circuit including a DC battery connected to a bidirectional buck-boost converter, comprising:

calculating, by a fractional order proportional integral (FOPI) voltage controller connected to a computing device, a fractional order proportional integral (FOPI) transfer function of the plurality of DC batteries;
calculating, by the FOPI voltage controller, a compensation voltage vcom of each DC battery of the plurality of DC battery circuits based on the FOPI transfer function;
measuring, by the computing device, an SoC of each of the DC batteries;
calculating, by the computing device, an average SoC of the DC batteries of the plurality of DC battery circuits;
formulating, by the computing device, an SoC transfer function based on the average SoC of the DC batteries of the plurality of DC battery circuits;
combining, by the computing device, the compensation voltage vcom and the SoC transfer function in a double control loop of the plurality of DC battery circuits to obtain a control model;
modifying, by the computing device, the control model to develop a small signal model based on bidirectional buck-boost converter small signal equations of the plurality of DC battery circuits;
generating, by the FOPI voltage controller, a FOPI control transfer function for each DC battery circuit based on the small signal model;
tuning, by the computing device, a plurality of parameters of the FOPI control transfer function based on a modified particle swarm optimizer;
and
controlling the DC bus voltage based on the FOPI control transfer function.

8 more elements

Dependencies are inferred from the claim text.

Facts

Application: 19/242,533Filed 18 Jun 2025 · us provisional application
Priority: 6 Dec 2024
Granted: 16 Dec 2025
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

H02J 1/10
Circuit arrangements for DC mains or DC distribution networks: parallel operation of DC sources
G05B 6/02
Internal feedback arrangements for obtaining particular characteristics, e.g. proportional, integral or differential: electric
H02J
Power supply and charging
G05B
Control or regulating systems in general