Inverter-based stand-alone microgrid control system using time synchronization-based measurement unit

Patent metadata

Field	Value
Publication number	US-10108153-B2
Application number	US-201514964954-A
Country	US
Kind code	B2
Filing date	Dec 10, 2015
Priority date	May 7, 2015
Publication date	Oct 23, 2018
Grant date	Oct 23, 2018

Abstract

An inverter-based stand-alone microgrid control system using a time synchronization-based measurement unit, in which a converter controller configured to control a converter that determines a voltage and a phase of a point where a plurality of distributed power supply devices is interconnected. The system includes a time correction unit configured to provide a time corrected on the basis of time information received from a GPS; a signal comparison/generation unit configured to compare a sine wave generated according to a voltage magnitude and a phase reference signal with a harmonic carrier signal on the basis of the time provided by the time correction unit, and generate a PWM signal; and a switch operation control unit configured to apply the PWM signal from the signal comparison/generation unit to the converter, and operate a switch.

First claim

What is claimed is:

1. An inverter-based stand-alone microgrid control system using a time synchronization-based measurement unit, comprising:
a stand-alone microgrid including a converter that determines a voltage and a phase of a point where a plurality of distributed power supply devices is interconnected;
a converter controller configured to control the converter;
a time correction unit configured to provide a time corrected on the basis of time information received from a Global Positioning System (GPS);
a signal comparison/generation unit configured to compare a sine wave generated according to a voltage magnitude and a phase reference signal with a harmonic carrier signal on the basis of the time provided by the time correction unit, and generate a Pulse Width Modulation (PWM) signal; and
a switch operation control unit configured to apply the PWM signal from the signal comparison/generation unit to the converter, and operate a switch.

2. The inverter-based stand-alone microgrid control system using the time synchronization-based measurement unit of claim 1 , wherein the time correction unit includes:
a GPS receiving unit configured to receive time information once per second from the GPS; and
an internal clock, as a converter internal clock, configured to correct the time information once per second on the basis of a GPS signal and accurately provide a time of 1 second divided into microseconds.

3. The inverter-based stand-alone microgrid control system using the time synchronization-based measurement unit of claim 1 , wherein the signal comparison/generation unit includes:
a function generation unit configured to generate a sinusoidal signal on the basis of the time provided by the time correction unit, and generate the sine wave according to a voltage magnitude and a phase reference signal;
a harmonic carrier signal generation unit configured to generate the harmonic carrier signal in the range of 10 kHz to 20 kHz to be used by the converter; and
a PWM signal generation unit configured to compare the sine wave from the function generation unit with the harmonic carrier signal from the harmonic carrier signal generation unit, and generate the PWM signal.

4. An inverter-based stand-alone microgrid control system using a time synchronization-based measurement unit, comprising:
a stand-alone microgrid including converters that determine a voltage and a phase of a point where a plurality of distributed power supply devices is interconnected;
a converter controller configured to correspond to each of the converters in order to control the converters included in the stand-alone microgrid and also configured to control a switch operation of each of the converters on the basis of a noiseless sinusoidal signal; and
a microgrid control center including a microgrid Energy Management System (EMS) configured to provide initial operation reference values, and configured to perform power-generation prediction and economic load dispatch for managing the stand-alone microgrid and perform Supervisory Control and Data Acquisition (SCADA) for automatically supervising and controlling an operation state of a low-level system.

5. The inverter-based stand-alone microgrid control system using the time synchronization-based measurement unit of claim 4 , wherein the time synchronization-based measurement unit is installed in the microgrid and data acquired by the time synchronization-based measurement unit are periodically transmitted to the microgrid control center, and a high-level multi-microgrid control tower issues a command for multi-microgrid interconnection.

6. The inverter-based stand-alone microgrid control system using the time synchronization-based measurement unit of claim 4 , wherein the microgrid EMS determines an output of a converter-based generator (CBG) and an input/output amount of an energy storage system (ESS) within the microgrid on the basis of current load, power-generation quantity, and State Of Charge (SOC) and predicted load and power-generation quantity pattern and provides the initial operation reference values.

7. The inverter-based stand-alone microgrid control system using the time synchronization-based measurement unit of claim 4 , wherein the microgrid control center includes:
a supervisory power control block configured to compare current a Converter-Based Generator (CBG) and an Energy Storage System (ESS) operation values transmitted from the time synchronization-based measurement unit with the initial operation reference values and provide modified operation reference value.

8. The inverter-based stand-alone microgrid control system using the time synchronization-based measurement unit of claim 7 , wherein the supervisory power control block continuously operates and reduces an error until the microgrid EMS provides new initial operation reference values, and transmits modified operation reference values to a power flow calculation block and a system model modification block in each operation.

9. The inverter-based stand-alone microgrid control system using the time synchronization-based measurement unit of claim 4 , wherein the microgrid control center includes:
a system model modification block configured to compare actual system measurement values obtained when modified operation reference values are transmitted and modify and complement a system model when an error is greater than a reference value.

10. The inverter-based stand-alone microgrid control system using the time synchronization-based measurement unit of claim 9 , wherein the system model modification block repeatedly compares a result of a power flow calculation using the modified operation reference values with the actual system measurement values and reflects a microgrid impedance (Zmg) to a model for a power flow calculation block.

11. The inverter-based stand-alone microgrid control system using the time synchronization-based measurement unit of claim 4 , wherein the microgrid control center includes:
a power flow calculation block configured to perform a power flow calculation by reflecting operation reference values modified by a supervisory power control block to a model to which currently measured loads are applied, and obtain a phase angle of a Converter-Based Generator (CBG) to satisfy a given condition.

12. The inverter-based stand-alone microgrid control system using the time synchronization-based measurement unit of claim 11 , wherein the power flow calculation block performs a power flow calculation by reflecting operation reference values issued from a high-level multi-microgrid control tower in the case of a multi-microgrid including a number of interconnected microgrids, and
a corresponding value is used for power transmission between multi-microgrids.

13. The inverter-based stand-alone microgrid control system using the time synchronization-based measurement unit of claim 4 , wherein the microgrid control center includes:
a tie line control means configured to control power transmission and interconnection between multi-microgrids, and
in a situation where multi-microgrids are continuously interconnected, the tie line control means intactly uses operation reference values transmitted after a power flow calculation, and
in a situation where separated multi-microgrids are being interconnected, the tie line control means synchronizes voltage magnitudes and phases of both interconnection buses by reflecting modified portions of the operation reference values transmitted from a high-level multi-microgrid control tower.

14. An inverter-based stand-alone microgrid control system using a time synchronization-based measurement

Assignees

• Univ Yonsei Iacf
• Keri Korea Electrotechnology Res Inst

Inventors

• Park Jungwook
• Lee Soohyoung

Classifications

• H02J3/388

  Arrangements for the handling of islanding, e.g. for disconnection or for avoiding the disconnection of power · CPC title

• Y02P80/14

  District level solutions, i.e. local energy networks · CPC title

• H02J3/08

  Synchronisation of networks · CPC title

• G05B13/026 Primary

  using a predictor · CPC title

• H02J3/48

  Controlling the sharing of active power · CPC title