KR20170018647A

KR20170018647A - A frequency control system and method for power grid using an energy storage device

Info

Publication number: KR20170018647A
Application number: KR1020150112540A
Authority: KR
Inventors: 김근환; 이태식
Original assignee: 이엔테크놀로지 주식회사
Priority date: 2015-08-10
Filing date: 2015-08-10
Publication date: 2017-02-20

Abstract

A frequency control system for compensating an output by using an energy storage system (ESS) according to the present invention includes: a master frequency control module configured to control a sub-frequency control module according to a control command transmitted from an energy management system (EMS) of an electric power system; and a plurality of sub-frequency control modules configured to instruct an amount of output allocated according to a frequency control command of the master frequency control module to a power conditioning system (PCS). Also, when the frequency is controlled by using the ESS for the frequency control, the frequency can be controlled by discharging and charging electricity, and performances in terms of a response time and accuracy can be superior to those of the related waterpower generation and thermal power generation. In addition, since the frequency control system of the present invention is capable of accurately performing a frequency measurement by one frequency measurement device to allow all the frequency control modules to receive the same frequency value through broadcasting, the frequency is transmitted more accurately than a case in which frequency measurement devices are installed individually, and thus an appropriate mode can be performed depending on the situation to accurately control an output from an ESS group, thereby performing a frequency adjustment effectively.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a frequency control system and method for adjusting a frequency using an energy storage device,

The present invention relates to a frequency control system for compensating an output using an energy storage device. More particularly, the output is related to a grid frequency. The output is compensated by controlling the frequency of the decrease of the grid frequency due to lack of output, Thereby enabling adjustment of the frequency.

The energy storage system (ESS) is a system that can save energy generated by lightning at nighttime and supply energy at necessary times such as weekly peak hours to increase energy efficiency.

Such an energy storage device can be utilized in various ways such as adjusting the main pail, reducing the peak, and stabilizing the renewable output.

The frequency of the Korean power system is specified as 60Hz. However, the grid frequency is not fixed. The frequency varies depending on the inertia of the generator when the generated power at the power side and the demanded power at the load side are unbalanced or the generator is rotating. It is the frequency adjustment that adjusts the generation power to react instantly to the varying load fluctuation.

As the demand for electricity increases and the electricity runs short, the frequency falls below 60Hz. Therefore, the power is adjusted by increasing the output from the power plant. If electricity is left at lunch time or night, the frequency exceeds 60Hz. I have adjusted the frequency. This role has mainly been handled by hydropower plants and thermal power plants.

Hydropower plants have been regarded as the most suitable means for controlling the frequency by adjusting the amount of water entering the generator to raise or lower the output from 0 to the maximum output. Even if the power can not be generated by the frequency control, the water remains in the dam, so there is little energy waste and there is no big deal in the generator.

In Korea, however, hydroelectric power plants account for a small share of the total electricity production, and the frequency adjustment was mainly carried out at thermal power plants.

However, there is a problem in that when the output is adjusted, the efficiency of the power plant is deteriorated or the failure rate of the power plant equipment is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to use an energy storage device (ESS) in controlling a frequency.

In addition, the present invention can select the transient mode control and the normal mode control according to the range of the measured frequency, thereby aiming at efficient power operation.

A frequency control system and method for adjusting a frequency using an energy storage device of the present invention includes a master frequency control module for controlling an auxiliary frequency control module according to a control command transmitted from an EMS of an electric power system, And a plurality of auxiliary frequency control modules for instructing the power control device (PCS) of the output of the amount distributed according to the frequency control command.

At this time, the frequency control system controls the frequency of the system by controlling outputs of a plurality of energy storage units (ESS) groups to each of the auxiliary frequency control modules.

Meanwhile, the frequency control system may further include a mode conversion device for converting the operation mode according to the measured frequency range. The mode conversion device includes a frequency measurement unit for measuring a frequency of the system, a mode determination unit for determining a mode in accordance with the frequency value measured by the frequency measurement unit, And a mode control unit for controlling the module.

At this time, the mode determining unit may automatically select an operation mode according to the measured frequency.

The operation mode may be a normal mode, a transient mode, or a charging mode.

The mode control unit informs the plurality of auxiliary frequency control modules and the master frequency control module by broadcasting in order to operate according to the selected mode.

A method of controlling a frequency using an energy storage device according to an embodiment of the present invention includes the steps of: (a) determining whether the energy storage device is in a charging mode and performing charging in a charging mode; (b) (C) comparing the measured frequency value with a preset frequency value to determine whether it is a transient mode, (d) determining a transient mode discrimination step ) Performing the normal mode when the transient mode is not performed in the step (c), and performing the transient mode when the transient mode is selected.

(E) checking the SOC value after performing the normal mode or the transient mode, (f) comparing the SOC value with a predetermined SOC value range, (g) comparing the SOC value with a predetermined SOC value range, ) Performing the charging mode when the comparison value is within the predetermined SOC value range in the step (f).

Meanwhile, after performing the charging mode in the step (g), the mode conversion may be performed according to the newly measured frequency value after returning to the step (b).

When adjusting the output, the ESS for frequency adjustment can discharge or charge the electricity to keep the frequency constant. It has superior performance in response speed and accuracy than existing hydroelectric power generation and thermal power generation.

In addition, in the frequency control system according to the present invention, since one frequency meter accurately measures the frequency, all the frequency control modules broadcast the same frequency value, so that the frequency is transmitted more accurately than when the frequency meter is individually installed. So that the output from the energy storage device group can be precisely controlled and the frequency adjustment can be performed more efficiently.

1 is a diagram of a power system in accordance with an embodiment of the present invention.
2 is a view illustrating a mode conversion apparatus according to an embodiment of the present invention.
3 is a flowchart illustrating an operation of a frequency control system using an energy storage device according to an embodiment of the present invention.
4 is a diagram illustrating a frequency control method using an energy storage device according to an embodiment of the present invention.
5 is a graph illustrating a frequency control using an energy storage device according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may obscure the subject matter of the present invention.

Before describing the present invention, the terms used and the meanings thereof will be summarized in connection with the present invention.

Energy Storage System (ESS) is a comprehensive system that integrates battery, BMS (Battery Management System, PCS (Power conditioning System), EMS (100) System, and narrowly refers to a configuration of a battery and a PCS as an energy storage device.

The battery is a component that plays a role of storing electricity through PCS and discharging electricity when it is needed. BMS is a component that battery cell has maximum characteristics such as cell capacity / protection, life prediction, charge / discharge control, It is a device that can be safely used without explosion due to external impact. The PCS receives the power from the generator and stores it in the battery or converts the characteristics of the electricity to discharge it into the system. The EMS 100 includes a Supervisory Control And Data Acquisition (SCADA) system 200 for monitoring the status of the battery, monitoring and controlling the status of the PCS, a database 130 for storing collected data related to the power system, Which is an operating system for monitoring and controlling the ESS in a control center or the like. The HMI 110 (Human Machine Interface) refers to a user equipment for controlling the power system. On the other hand, the state of charge (SOC) means a state of charge of the energy storage device 300 (ESS).

EMS (100) has FEMS, BEMS, HEMS, etc., and EMS (100) system applied to factory is FEMS, EMS system applied to building is BEMS, and EMS (100) do.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 is a diagram illustrating a power system according to an embodiment of the present invention.

The frequency control system 120 according to an embodiment of the present invention includes a master frequency control module 121 and a plurality of auxiliary frequency control modules 122. The master frequency control module 121 for controlling the auxiliary frequency control module 122 in accordance with the control command transmitted from the EMS 100 of the power system and the master frequency control module 121 for controlling the master frequency control module 121 And a plurality of auxiliary frequency control modules 122 for instructing the power control unit PCS of the output of the allocated amount.

Meanwhile, the frequency control system 120 can control the frequency of the system by controlling the output of the plurality of energy storage devices 300 (ESS) to each of the auxiliary frequency control modules 122. By using such a plurality of energy storage devices 300 (ESS), it is possible to maintain the frequency constant by discharging or charging the electric power when controlling the output, and it is possible to maintain the frequency in response to the electric power or the thermal power Thereby enabling efficient power operation.

And may further include a mode conversion device 123 in another embodiment of the frequency control system 120 using the energy storage device of the present invention. More specifically, it is characterized by further comprising a mode conversion device 123 for converting the operation mode according to the measured frequency range.

2 is a diagram illustrating a mode conversion device 123 according to an embodiment of the present invention.

Referring to FIG. 2, the mode conversion device 123 includes a frequency measurement unit 123-1, a mode determination unit 123-2, and a mode control unit 123-3.

More specifically, a frequency measuring section 123-1 for measuring the frequency of the system, a mode determining section 123-2 for determining the mode in accordance with the frequency value measured by the frequency measuring section 123-1, And a mode control unit 123-3 for controlling the auxiliary frequency control module 122 according to the mode determined by the mode determination unit 123-2.

At this time, the frequency measuring unit 123-1 is intended to measure a commercial frequency (low frequency), and a frequency system using a metal diaphragm can be used at a low frequency.

The mode determination unit 123-2 can automatically select the operation mode according to the measured frequency. The mode conversion device 123 does not passively control the mode through the automatic selection, so that it is possible to quickly respond to various incidents occurring in the power system.

On the other hand, the operation mode may be a normal mode, a transient mode, and a charging mode. At this time, the normal mode is characterized by performing automatic power generation control.

The normal mode serves to restore the frequency. At a predetermined time interval, the dropped frequency is checked, and the command value is transmitted to the PCS in accordance with the frequency, thereby contributing to the recovery of the system frequency through the output of the energy storage device 300 (ESS). At this time, the normal mode generates an output for a set period according to the control purpose of the system. For example, if the drop in frequency is not large, the system can operate in normal mode and generate output in a period of 2 to 4 seconds to recover the dropped frequency.

In this normal mode, the energy storage device 300 (ESS) can alternately charge and discharge, and the SOC value of the energy storage device 300 (ESS) can be maintained at 50 to 80%.

Transient mode plays a role of quick response when a frequency related accident occurs. This is to follow the frequency and control it directly without linking with the power system. At this time, when the system frequency greatly drops, an accident occurs in a power system such as a blackout. In the transient mode, a large amount of output is applied in a short time to prevent such an accident. At this time, since the energy storage device 300 (ESS) generates a strong output at one time to prevent a maximum decrease of the frequency, the SOC value may drop to 10%. The frequency comparison value at which this transient mode operates can be set differently according to the control purpose of the system.

The charging mode can be activated when the SOC value of the battery is equal to or lower than the SOC value set by the user. Generally, when the SOC value is 50% or less, it operates in the charge mode. On the other hand, in the transient mode, since the SOC value is very low, it can be immediately switched to the charging mode.

At this time, since there are a plurality of energy storage devices 300 (ESS), another energy storage device 300 (ESS) can be operated in transient mode and normal mode. Which can be controlled by the master frequency control module 121.

In this way, the normal mode, the transient mode, and the charging mode can be automatically selected through the mode converter 123, and when an accident occurs in the power system, the first energy storage device 300 (ESS) And the second energy storage device 300 (ESS) can immediately operate in the normal mode and contribute to frequency recovery after preventing the maximum fall of the frequency in the transient mode.

3 is a flowchart illustrating an operation of the frequency control system 120 using the energy storage device according to an embodiment of the present invention.

4 is a diagram illustrating a frequency control method using an energy storage device according to an embodiment of the present invention.

5 is a graph illustrating a frequency control using an energy storage device according to an embodiment of the present invention.

3 to 5, a frequency control method for adjusting a frequency by compensating an output according to an embodiment of the present invention includes a charging mode discriminating step S1, a frequency measuring step S2, a transient mode discriminating step S3 A mode performing step S4, an SOC value checking step S5, a SOC value comparing step S6, and a charging mode performing step S7. (A) determining whether the mode determining unit is in a charging mode and performing a charging in a charging mode; (b) (C) a transient mode discriminating step of discriminating whether the frequency value measured by the frequency measuring unit is a transient mode by comparing the measured frequency value with a preset frequency value according to the mode judging unit mode S3), (d) if at least one of the auxiliary frequency control modules performs the normal mode in the step (c) according to the control command of the mode control unit, and performs the transient mode in the transient mode (E) a step (S5) of confirming the SOC value after the energy storage device performs the normal mode or the transient mode according to the command of the auxiliary frequency control module; (f) The SOC value (S6) comparing a predetermined range of the SOC value with the range of the predetermined SOC value; and (g) performing a charging mode when the comparison value is within a predetermined SOC value range in the step (f).

Meanwhile, after the energy storage device performs the charging mode in step (g), the energy storage device returns to step (b) and performs mode conversion according to the frequency value newly measured by the frequency measurement part can do.

(c) In step S3, the frequency value determined as the transient mode may be set differently according to the control purpose of the system. For example, in case of the commercial power supply is set to 60Hz, and the transient mode setting reference frequency value is 59.5Hz, when the system frequency falls to 59.3Hz due to an accident, etc., To prevent a decrease in the system frequency. In the case where the frequency drop is not large, such as an accident, generally, it can be set to operate in the normal mode.

Thus, those skilled in the art will appreciate that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

If the ESS replaces the frequency tuning function, a coal-fired power generator with a low power generation cost can be operated at 100% output. In the past, thermal power plants were not able to drive 100% because they had reserves to adjust the frequency.

When adjusting the output, the ESS for frequency adjustment can discharge or charge the electricity to keep the frequency constant. Performance is superior in terms of response speed and accuracy than existing hydropower or thermal power generation.

100: EMS (Energy Management System)
110: Human Machine Interface (HMI)
120: Frequency control system
121: Master frequency control module
122: auxiliary frequency control module
123: Mode conversion device
123-1: frequency measuring unit
123-2: mode judgment section
123-3:
130: DB (Database)
200: SCADA system (Supervisory Control And Data Acquisition system)
300: Energy storage device (ESS)

Claims

A master frequency control module for controlling the auxiliary frequency control module according to the control command transmitted from the EMS of the power system; And
A plurality of auxiliary frequency control modules for instructing a power control device (PCS) to output an amount of the allocated power according to a frequency control command of the master frequency control module;
To adjust the frequency to compensate for the output.

The method according to claim 1,
The frequency control system
And the frequency of the system is controlled by controlling the outputs of the plurality of energy storage devices to each of the auxiliary frequency control modules.

3. The method of claim 2,
The frequency control system
Further comprising a mode conversion device for converting the operation mode according to the measured frequency range.

The method of claim 3,
The mode conversion device
A frequency measuring unit for measuring a frequency of the system;
A mode judging unit for judging a mode according to the frequency value measured by the frequency measuring unit; And
A mode control unit for controlling the auxiliary frequency control module according to the mode determined by the mode determination unit;
And adjusting the frequency by compensating the output.

5. The method of claim 4,
The mode determination unit
Characterized in that the operating mode is automatically selected according to the measured frequency.

6. The method of claim 5,
Wherein the operation mode is a normal mode, a transient mode, and a charge mode, wherein the frequency is adjusted by compensating the output.

5. The method of claim 4,
The mode control unit
And informing the plurality of auxiliary frequency control modules and the master frequency control module by broadcasting in order to operate according to the selected mode.

A method for frequency control in a frequency control system,
(a) determining whether the mode judging unit is in the charging mode, and performing charging in the case of the charging mode;
(b) a frequency measuring step of measuring a frequency of the frequency measuring part system when the charging mode is not in the step (a);
(c) comparing the frequency value measured by the frequency measurement unit with a preset frequency value according to the mode judging unit mode to determine whether the frequency mode is a transient mode; And
(d) performing at least one auxiliary frequency control module according to a control command of the mode control unit, performing a normal mode when the auxiliary frequency control module is not a transient mode in the step (c), and performing a transient mode when the auxiliary frequency control module is in a transient mode ;
And adjusting the frequency by compensating the output including the frequency.

9. The method of claim 8,
Following step (d) above,
(e) confirming the SOC value after the energy storage device performs the normal mode or the transient mode according to the command of the auxiliary frequency control module;
(f) comparing the SOC value with a predetermined SOC value range; And
(g) performing a charging mode when the comparison value is within a predetermined SOC value range in the step (f);
And adjusting the frequency by compensating the output including the frequency.

10. The method of claim 9,
Wherein after the energy storage device performs the charging mode in the step (f), the mode conversion may be performed according to the frequency value newly measured by the frequency measurement part, after returning to step (b) To adjust the frequency.