KR20100060725A - Operating reserve power supply system in electric power system, and control method thereof - Google Patents

Abstract

PURPOSE: An operation reserve supply system of an electric power system and a control method thereof are provided to extend a replacement period of an energy storage device by reducing the frequencies of charge/discharge operations of the energy storage device. CONSTITUTION: A plurality of DC/DC converters(20) is connected to an energy storage device(10) in serial/parallel. An energy storage device is one of a battery, a super capacitor, and a super conductive storage device. A DC/AC inverter(30) transfers the output inputted from the DC/DC converter to the electric power system. A controller(40) generates a first frequency operation reserve power in the malfunction of the system. The controller includes a voltage controller, a frequency reserve controller, a phase controller, and a switching controller.

Description

Operating reserve power supply system in electric power system, and control method

The present invention relates to a frequency operation reserve power supply system and a method for transiently alleviating the frequency reduction caused by the output shortage caused by the failure of the renewable energy power source, thereby increasing the limit capacity of the renewable energy power source.

As a means for stabilizing the output fluctuations associated with grid linkages of renewable energy sources, firstly, supply by existing hydroelectric and fossil fuel generators, secondly, supply by neighboring systems by high voltage direct current transmission (HVDC), third, It can be classified as generating power limit of renewable energy power source.

  First, there is a limit of the frequency reserve power that can be provided by existing hydroelectric and fossil fuel generators, and this limit determines the linkable capacity of renewable energy sources. In order to continuously increase the linkage of renewable energy sources, such generators should be added, but issues such as civil complaints and environmental issues should be resolved in addition to high investment costs or long construction periods.

  Second, the supply of reserve power from neighboring grids by HVDC system is similar to the construction of power plants, and the construction cost and period do not meet the purpose of expanding the capacity of renewable energy sources, and play a multi-purpose role of improving the stability and reliability of the entire system. However, there are practical difficulties in carrying out the specialized purpose of stabilizing the output fluctuations caused by renewable energy sources.

  Third, the limit of generation output of renewable energy sources does not meet the purpose of expanding the introduction capacity of renewable energy sources.

Thus, in the prior art, the energy storage device has been alleviated the output fluctuation of the new renewable energy power source through the constant charge and discharge operation, in this case, due to the frequent charging and discharging, the cost of replacing the expensive energy storage device is too inefficient. In addition, in order to mitigate the output fluctuation of a specific capacity renewable energy power source, a considerable capacity energy storage system is required, which may cause a double cost problem.

An object of the present invention to solve the above problems is to provide frequent energy supply only when the renewable energy power supply is dropped due to system failure, which is the main cause of limited capacity, without always operating the energy storage device. The aim is to increase the introduction capacity of renewable energy sources while avoiding discharges and relatively reducing the capacity of energy storage systems.

In addition, to effectively control the system for supplying the frequency reserve power using the energy storage device in accordance with the connection of renewable energy sources, and to provide an efficient operation reserve power operation method.

The present invention has been made in order to solve the above problems, the present invention provides a system for operating reserve power supply of the power system linked to the renewable energy source, the energy storage device of the renewable energy source; A plurality of DC / DC converters connected in series / parallel with the energy storage device; A DC / AC inverter transferring an output flowing through the DC / C converter to a power system; And a controller for controlling the DC / DC converter and the DC / AC inverter to generate a frequency reserve while controlling a system frequency to a predetermined value when a system failure occurs.

Here, the energy storage device is preferably any one of a battery, a super capacitor, and a superconducting storage device, and the control unit preferably includes a voltage controller, a current and phase angle controller, and a switching controller.

The control unit may control the DC / DC converter through the frequency reserve power controller, the current controller, and the switching controller, and the control unit may control the DC / AC through the voltage controller, the current or phase angle controller, and the switching controller. It is desirable to control the inverter.

In addition, the present invention provides a method for operating reserve power of a power system linkage of renewable energy, comprising: (a) determining whether a system failure occurs in a system standby state; (b) supplying a first frequency operating reserve by using an energy storage device when the system failure occurs; (c) determining whether the system failure is removed; (d) determining whether to recover the system frequency when the system fault is removed; (e) charging energy to the energy storage device when the system frequency is restored; And (f) determining whether the charging is completed.

In addition, when the system failure does not occur in the step (a), it is preferable to maintain the system standby mode, and when the system failure is not eliminated in the step (c), switching to the step (b) desirable.

In addition, if the system frequency is not recovered in the step (d), it is preferable to switch to the step (c), and when the system failure is not eliminated in the step (c), the step (b) is performed. When the charging is completed in the step (f), it may be switched to the system standby mode, and when the charging is not completed, it may be switched to the (e) step.

When providing the present invention, first, the present invention can increase the associated capacity of the renewable energy power source using a relatively small capacity energy storage device, or improve the frequency stability of the system, and second, the present invention is energy storage The number of charge / discharge cycles of the device can be reduced, significantly extending the replacement life of the storage device.

Third, the present invention can replace the additional construction of the existing gas engine generator, such as by using the energy storage device as a primary operating frequency reserve power supply source, can reduce the cost and construction period, and fourth, the present invention is a system failure By supplying insufficient primary frequency reserve by dropping of renewable energy sources, the combined capacity of renewable energy sources can be effectively increased.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a graph showing a change in system frequency when supplying a general operating reserve force. Differences in power generation and loads result in changes in system frequency. Thus, fluctuations in the output of wind power require the supply of frequency reserves. The frequency reserve power is composed of three stages as shown in FIG. 1, the primary frequency reserve power automatically input in 15 to 30 seconds each and the secondary power automatically input in 3 to 5 minutes by the power system operator. Secondary frequency reserve, and Tertiary frequency reserve, which the power system operator manually inputs in 15 minutes.

2 is a graph showing a change in system frequency when a system failure occurs. As shown in FIG. 2, when a failure occurs in a system to which a renewable energy source is linked, the renewable energy sources are largely eliminated from the system by a low voltage, and the system frequency decreases. At this time, when it becomes less than 59.2 Hz, some loads in the system are automatically dropped by the low frequency relay. Therefore, the maximum capacity that the frequency can maintain above 59.2Hz even if the system fails is the grid-connected limit capacity of the renewable energy power source.

Thus, in order to increase the combined capacity of the renewable energy power source, it is necessary to secure a fast response frequency of the first frequency, the present invention proposes a system for supplying the primary frequency reserve by using an energy storage device and its control or operation method. I would like to.

3 is a configuration diagram of a frequency reserve power supply system using an energy storage system (ESS) proposed in the present invention. As shown in FIG. 3, the system according to the present invention includes an energy storage device (ESS: 10), a DC / DC converter 20, a DC / AC inverter 30, and a controller 40.

One or several energy storage devices (ESS: 10) can be connected in parallel, and the low voltage DC output of the energy storage device (ESS: 10) is connected to the common DC voltage through the DC / DC converter 20. The voltage is boosted and converted into an AC output through the DC / AC inverter 30. It is operated in connection with power system through the link transformer.

Here, the energy storage device can be applied to various types of energy storage devices (eg, batteries, supercapacitors, superconducting storage devices, etc.) and improves the dynamic stability of the system as well as a means for increasing the combined capacity of new and renewable energy sources. It can be used as a primary operating frequency reserve power supply means for the.

The DC / DC converter 20 serves to generate a frequency reserve while controlling the system frequency to a command value when a system failure occurs, and simultaneously boosts the low voltage of the energy storage device to the high voltage of the common direct current stage. The DC / AC inverter 30 converts a DC output into an AC output, and serves to transfer energy of the energy storage device transferred through the DC / DC converter 20 to the power system.

4 is a diagram illustrating a configuration of controlling a DC / DC converter by a controller. As shown in FIG. 4, the command value fsys_ord and the actual value fsys of the grid frequency output the command value idc_ord of the DC current flowing into the DC-DC converter through the reserve power controller. The DC-DC converter is operated by generating a switching signal of the DC-DC converter through the current controller and the switching controller together with the DC current actual value idc.

5 is a diagram illustrating a configuration of controlling a DC / AC inverter by a controller. The DC / AC inverter 30 controls the voltage Vdc of the common direct current stage to be a constant value Vdc_ord so that the output flowing into the common direct current stage through the DC / DC converter 20 is directly transmitted to the power system. . The voltage controller receives the DC voltage command value Vdc_ord and the actual value Vdc and outputs the output current command value of the inverter or the command value of the inverter output voltage phase angle.

This output value generates a switching signal for driving the DC / AC inverter 30 through the lower current controller or phase angle controller and the switching controller. Here, a current controller for controlling the magnitude of the inverter output current may be used as a lower controller below the voltage controller, or a phase angle controller for controlling the phase angle of the inverter output voltage may be used.

As such, when the system failure occurs, the control unit 40 controls the specific system frequency command value and supplies the primary frequency operating reserve power from the energy storage device, thereby increasing the associated capacity of the renewable energy power source. To improve the frequency stability of the system. In addition, the number of charge / discharge cycles of the energy storage device can be reduced, thereby significantly extending the replacement life of the storage device.

6 is a graph showing the increase in the associated capacity by the first reserve power compensation by the driving reserve power supply system according to the present invention. As shown in FIG. 6, the present invention provides a primary frequency reserve by using an energy storage device at the moment when a renewable energy power source is dropped due to system failure, thereby alleviating the degree to which the system frequency falls. To increase the capacity limit.

That is, the capacity of the energy storage device can be considerably reduced because the power is supplied transiently only for about 15 seconds to less than 1 minute. For example, if about 60 MW of power should be supplied for 1 minute as a frequency reserve, 1 MWh of capacity would be required if the storage is ideal. In addition, the failure of the transmission system with a large wavelength is not frequent (eg, 55 times in Korea in 2003). Therefore, even if a new renewable energy power source is dropped every time for all these failures, the required number of charge / discharge cycles of the storage device is always maintained. Significantly less than in operation, the cost of saving or replacing storage can be reduced.

7 is a diagram illustrating a flowchart of a method for supplying driving reserve power by linking a power system of a renewable energy source according to the present invention. As shown in Fig. 7, the operation reserve power supply system is operated in a standby mode at all times after starting. (S100) In this mode, the output is 0 while the system is connected to the grid, and when there is an output command, It is an operation state that can output. Always monitor or determine whether there is a system failure (S110), and maintains the system standby mode if it is not a system failure (S100).

If the system failure is determined by determining whether the system failure, the primary frequency operation reserve power is supplied under the control of the control unit 40 shown in Figs. 4 and 5 (S300). And continuously determine whether the system failure is removed (S400), if the system failure is not removed, the operation reserve power supply is continued again (S300), if the system failure is removed, the frequency is recovered (S500) is determined do.

The operation reserve power supply is continued until the frequency is restored, and when the frequency is restored, the battery is switched to the discharged energy storage device charging mode (S600). It is determined whether the charging is completed (S700), and when the charging is completed, the system is switched to the standby mode (S100).

While the invention has been shown and described with respect to the specific embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Anyone with it will know easily.

1 is a graph showing a change in system frequency when supplying a general operating reserve force;

2 is a graph showing a change in system frequency at the time of system failure;

3 is a configuration diagram of a frequency reserve power supply system using an energy storage system (ESS) proposed in the present invention;

4 is a diagram illustrating a configuration of controlling a DC / DC converter by a controller;

5 is a diagram illustrating a configuration of controlling a DC / AC inverter by a controller;

6 is a graph showing the increase in the associated capacity by the first reserve power compensation by the driving reserve power supply system according to the present invention;

7 is a diagram illustrating a flowchart of a method for supplying driving reserve power by linking a power system of a renewable energy source according to the present invention.

Claims (10)

In operation reserve power supply system of power system linkage of renewable energy source, Energy storage device of renewable energy source; A plurality of DC / DC converters connected in series / parallel with the energy storage device; A DC / AC inverter transferring an output flowing through the DC / C converter to a power system; And a controller for controlling the DC / DC converter and the DC / AC inverter to generate a frequency reserve while controlling a system frequency to a predetermined value when a system failure occurs. The method of claim 1, The energy storage device is a driving reserve power supply system, characterized in that any one of a battery, a super capacitor, a superconducting storage device. The method of claim 1, And the control unit includes a voltage controller, a frequency reserve force controller, a current or phase angle controller, and a switching controller. The method of claim 3, And the control unit controls the DC / DC converter through the frequency reserve power controller, the current controller, and the switching controller. The method of claim 3, And the control unit controls the DC / AC inverter through the voltage controller, the current or phase angle controller, and the switching controller. In the operation reserve power operation method of grid-linked generation of renewable energy, (a) determining whether a system failure occurs in the system standby state; (b) supplying a first frequency operating reserve by using an energy storage device when the system failure occurs; (c) determining whether the system failure is removed; (d) determining whether to recover the system frequency when the system fault is removed; (e) charging energy to the energy storage device when the system frequency is restored; (f) determining whether the charging is completed. The method of claim 6, When the system failure does not occur in the step (a), the operation reserve power operating method, characterized in that for maintaining the system standby mode. The method of claim 6, If the system failure is not eliminated in the step (c), the operation reserve power operating method, characterized in that switching to the step (b). The method of claim 6, If the system frequency is not recovered in the step (d), switch to the step (c), and if the system failure is not removed in the step (c), the operation characterized in that the step (b) How to operate reserve power. The method of claim 6, In step (f), when the charging is completed, the system standby mode, and if the charging is not completed, the operation reserve power operation method, characterized in that to switch to the step (e).

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