KR20210047621A - GRID CONNECTED POWER DEVICE with POWER COMPENSATION for LOW VOLTAGE RIDE THROUGH and GRID CONNECTING METHOD - Google Patents

Abstract

Provided is a power compensation system linkage device which can stabilize a direct current (DC) link voltage without loss of generated power. The power compensation system linkage device comprises: a system linkage device linking power transfer between a renewable energy generation system and a system, and having a system linkage switch regulating connection with the system, an insulation transformer transmitting alternating current (AC) power while blocking a direct current path of the system and the renewable energy generation system, and a renewable side conversion circuit converting AC of the insulation transformer and DC of a DC link of the renewable energy generation system; a power conversion control unit controlling DC-AC conversion operation of the system linkage device; and a power compensation device connected between the system linkage switch and the insulation transformer, and supplying power to the system in line with the renewable energy generation system in a low voltage acceptance operation situation.

Description

Power compensation system linkage device and system linkage method for low voltage acceptance operation {GRID CONNECTED POWER DEVICE with POWER COMPENSATION for LOW VOLTAGE RIDE THROUGH and GRID CONNECTING METHOD}

The present invention relates to a power compensation system linkage device for low voltage acceptance operation of a new renewable energy generation system such as a wind turbine, and more particularly, a power compensation system linkage capable of performing stable power compensation even in a situation where the system voltage is significantly reduced. It relates to the device.

Recently, the demand for new and renewable energy has been steadily increasing as a countermeasure against depletion of fossil fuels and global warming, and among them, the installed capacity of wind power generation is rapidly increasing worldwide, which means that the amount of power the wind power takes up in the system is also rapid. Means to increase.

However, nature does not supply what man wants, as much as he wants, when man wants it, and the amount of power generation rapidly fluctuates according to changes in nature, which adversely affects the entire power system.

In addition, the gradual increase in the proportion of wind power generation in the power system does not stop power generation against disturbances in the system, but requires it to play the role of cooperating with the system.Therefore, in many countries, grid connection regulations (Grid Code) is being legalized.

In particular, low voltage acceptance operation (LVRT) maintains a connected state without removing the wind power generation from the grid within a predetermined time, even if an instantaneous low voltage state occurs in the system, and is determined at the point when the system recovers from the instantaneous low voltage state. The power of the system is sent to the system to perform an action that contributes to system recovery.

More specifically, when an instantaneous low voltage of the system occurs, the low voltage acceptance operation (LVRT) function required for the wind turbine (small) is illustrated. The low voltage acceptance operation function is 0625 seconds until the instantaneous low voltage of the system reaches the level of 20% of the grid voltage in a normal state. It is the ability to keep the grid-connected state when operating for a period of time and recovering more than 90% of the grid voltage in a normal state for a maximum of 3 seconds.

Most of the grid-connected devices for distributed power supply are power conversion devices that are connected through DC link power. In the normal state, the DC link voltage is stabilized due to power transfer from the renewable energy source to the grid, but in the LVRT situation where the grid voltage is significantly low, the power delivered to the grid decreases or disappears, so the DC link voltage rises rapidly. It is done.

As a conventional solution for solving this problem, there is a method using a dynamic brake. This is a method of suppressing the increased voltage through an external resistor when the DCLink voltage rises above a specific voltage. It can be applied to most grid-connected devices for new and renewable energy, and has the advantage of simple control method and configuration, but there is a problem in that a space for attaching an external resistor is required, and the larger the capacity, the larger the required space.

As another conventional solution, there is a de-loading droop control method. This is mainly used in wind power generation, and is a method of reducing power generation for new and renewable energy when the DC link voltage rises above a specific voltage or a specific frequency. There is an advantage in that external hardware is not required, but the voltage suppression performance is poor, and in order to improve the performance, a complex control algorithm is required, which makes it difficult to apply.

As another conventional solution, there is a power compensation control method. This is a method of compensating the power produced by the power conversion device for controlling new and renewable energy according to the LVRT situation. The control performance is superior to the Droop control and does not require an external device, but the control algorithm is relatively complex, and requires a very detailed system, power conversion device, and generation power parameters.

Republic of Korea Publication 10-2014-0087932

An object of the present invention is to provide a power compensation system interconnection device capable of stabilizing a DC link voltage without loss of power generated by renewable energy in an LVRT situation.

An object of the present invention is to provide a system connection method in which a power compensation system connection device for low voltage acceptance operation can be stably connected to a restored system without initial charging resistance.

A power compensation system linkage device according to an aspect of the present invention includes a grid linking switch that connects a new and renewable energy generation system and power transmission between the grid and regulates the connection with the grid, and a direct connection between the grid and the new and renewable energy generation system. A grid connection device including an isolation transformer for transmitting AC power while blocking a current path, and a new and renewable side conversion circuit for converting AC of the isolation transformer and DC link of the new and renewable energy power generation system; A power conversion control unit for controlling a DC-AC conversion operation of the grid-connected device; And a power compensation device connected between the grid-connected switch and the isolation transformer, and supplying power to the grid in step with the new and renewable energy generation system in a low voltage receiving operation situation.

Here, the power compensation device includes: an energy storage medium that stores energy in the form of mechanical potential energy due to inertia or gravity; An energy converter in the form of a motor generator for converting energy stored in the energy storage medium into electric power; A DC conversion circuit for converting power output from the energy converter into DC; A compensation-side conversion circuit for converting DC power of the DC conversion circuit and AC power of the system; And a power compensation control unit that controls the compensation-side conversion circuit to supply the power stored in the BESS to the system in a low-voltage-accepting operation situation.

Here, the power compensation device includes: a BESS for storing and discharging power in a battery or a supercapacitor, which is a secondary battery; A compensation-side conversion circuit for converting DC power of the BESS and AC power of the system; And a power compensation control unit that controls the compensation-side conversion circuit to supply the power stored in the BESS to the system in a low-voltage-accepting operation situation.

Here, the power compensation control unit may include: a power distribution unit that calculates a compensation power to be supplied to the system in a low voltage acceptance operation situation and a share of the compensation power with the renewable energy generation system; And a power compensation unit for systemically compensating the power obtained by applying the share ratio to the compensated power.

Here, the power conversion control unit reflects the command value of the DC link voltage to the DC link voltage at the present time, and supplies it from the renewable energy generation system in a low voltage receiving operation situation excluding the power required inside the renewable energy generation system. Possible generated power may be calculated and provided to the power distribution unit.

Here, the power compensation device, when the grid voltage is restored to normal while the new and renewable energy generation system is separated from the grid, the voltage of the DC link is restored until a predetermined reference value of the peak voltage between lines of the restored grid is reached. Power can be provided.

Here, the power compensation device, monitoring the grid voltage while the grid connection switch is open; When the grid voltage is restored to normal, calculating a peak voltage between lines of the grid; Supplying the power stored therein to the DC link; Checking whether the DC link voltage is greater than or equal to a predetermined reference value of a peak voltage between lines; When the DCLink voltage is higher than a predetermined reference value of the peak voltage between lines, stopping power supply to the DCLink and disconnecting the connection with the renewable energy generation system; And closing the grid-connected switch and instructing the grid-connected power control to the power conversion control unit.

A grid linking method according to another aspect of the present invention is connected between a grid linking switch that regulates the connection between the new and renewable energy power generation system and the grid, and an isolation transformer that insulates the new and renewable energy power generation system and the grid, and a low voltage acceptance operation situation In the grid connection method performed in the power compensation device that supplies power to the grid in keeping with the renewable energy generation system in,

Monitoring the grid voltage while the renewable energy power generation system is separated from the grid; When the grid voltage is restored to normal, calculating a peak voltage between lines of the grid; Supplying the electric power stored therein to the DC link of the renewable energy generation system; Checking whether the DC link voltage is greater than or equal to a predetermined reference value of a peak voltage between lines; When the DCLink voltage is higher than a predetermined reference value of the peak voltage between lines, stopping power supply to the DCLink and disconnecting the connection with the renewable energy generation system; And closing the grid-connected switch and instructing grid-connected power control for renewable energy generation.

If the power compensation system linkage device for the low voltage acceptance operation of the present invention according to the above-described configuration is implemented, there is an advantage in that the DC link voltage can be stabilized without loss of power generated by renewable energy in the LVRT situation.

The grid linking method performed in the power compensation grid linking device for low voltage acceptance operation of the present invention can be stably linked to the restored grid without initial charging resistance, thereby reducing hardware cost for configuring the initial charging resistance. .

1 is a block diagram showing a new and renewable energy power compensation system interconnection device for LVRT (low voltage acceptance operation) according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a relationship between an embodiment of a power compensation apparatus applicable to FIG. 1 and other configurations;
3 is a control block diagram of a new and renewable energy power compensation system interconnection device for VRT (low voltage acceptance operation) in which the configuration of FIG. 2 is more specific.
FIG. 4 is a block diagram showing a part of calculating power generated by renewable energy in FIG. 3.
FIG. 5 is a block diagram illustrating a part of calculating a distribution of power to be provided to a grid in an LVRT situation in FIG. 3;
6 is a flow chart illustrating a method for connecting a system during system recovery that can be performed in the power compensation system connecting device of FIG. 1.
FIG. 7 is a block diagram showing a relationship between another embodiment of a power compensation device applicable to FIG. 1 and other configurations;

In describing the present invention, terms such as first and second may be used to describe various elements, but the elements may not be limited by terms. The terms are only for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

When a component is connected to or is referred to as being connected to another component, it can be understood that it is directly connected to or may be connected to the other component, but other components may exist in the middle. .

The terms used in the present specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions may include plural expressions unless the context clearly indicates otherwise.

In the present specification, terms such as include or include are intended to designate the presence of features, numbers, steps, actions, components, parts, or a combination thereof described in the specification, and one or more other features or numbers, It may be understood that the possibility of the presence or addition of steps, actions, components, parts, or combinations thereof, is not preliminarily excluded.

In addition, shapes and sizes of elements in the drawings may be exaggerated for clearer explanation.

1 is a block diagram showing a new renewable energy power compensation system interconnection device for LVRT (low voltage acceptance operation) according to an embodiment of the present invention.

The illustrated power compensation grid interconnection device connects the power transmission of the renewable energy generation system and the grid, and a grid link switch 115 that regulates the connection with the grid, and a direct current path between the grid and the renewable energy power generation system. A grid connection device (100) having an isolation transformer that transmits AC power while blocking the insulation transformer, and a renewable-side conversion circuit (130) for converting AC of the isolation transformer and DC link of the new and renewable energy power generation system; A power conversion control unit 200 for controlling a DC-AC conversion operation of the grid-connected device 100; And a power compensation device connected between the grid-connected switch 115 and the isolation transformer, and supplying power to the grid in step with the new and renewable energy power generation system in a low voltage receiving operation situation.

The illustrated power compensation grid linkage device adds a power compensation device to the grid linkage device similar to the general one, stores surplus energy generated from a renewable energy source in the power compensator even in LVRT situations, and saves the DC link voltage without loss of energy generated. It can be stabilized.

The illustrated power compensation device is composed of an energy storage system and assists the power required to satisfy the Grid Code in the LVRT situation. In addition, when the grid is restored in the state that the connection between the grid and the renewable energy generation system is cut off due to the lower grid voltage in the LVRT situation, the power compensation device shown can control the grid connection without initial charging resistance when the grid is initially connected. Do it. Through this, power consumed during grid connection can be eliminated, and hardware cost for configuring the initial charging resistance can be reduced.

FIG. 2 is a block diagram illustrating a relationship between an embodiment of a power compensation apparatus applicable to FIG. 1 and other configurations.

The illustrated power compensation device 4000 includes a BESS 600 for storing and discharging power in a battery or a supercapacitor, which is a secondary battery; A compensation-side conversion circuit 500 for converting DC power of the BESS 600 and AC power of the system; And a power compensation control unit 400 for controlling the compensation-side conversion circuit 500 to supply the power stored in the BESS 600 to the system in a low-voltage-accepting operation situation.

As an energy storage method, an energy storage method may be used as long as it passes through a prime mover type generator (to be described later), or a battery energy storage device (BESS) may be used as shown in FIG. 2. The power compensation control unit 400 controls the power conversion device 500 for the battery energy storage device (BESS) by receiving a compensation power command from the grid-connected device side, and accordingly, information on the active and inactive power and energy storage status to be charged and discharged. Is transmitted to the grid connection device.

3 is a control block diagram of a new and renewable energy power compensation system interconnection device for LVRT (low voltage acceptance operation) in which the configuration of FIG. 2 is more specific. In FIG. 3, it can be seen that the power compensation control unit 400 constituting a part of the power compensation device and the power conversion control unit 200 for the grid connection device may be mixed with each other. Even in actual implementation, it can be implemented with integrated hardware so that each parameter signal can be exchanged with each other.

Looking at the drawing, a block (power distribution unit) 460 that is in charge of power distribution and outputs an active/reactive power command suitable for the grid code according to the grid voltage level, and a block 290 that outputs the dq-axis current command. Leads the implementation of the idea of the invention.

Here, the output active/reactive power command may be changed not only to the power command by the grid code, but also to the power command requested by the system management system. Blocks excluding parts related to the spirit of the present invention are for implementing a power control algorithm of a grid-connected device, and may be similar to a structure of implementing a control algorithm of a grid-side power conversion device of a general power compensator.

The renewable energy power compensation system linkage device shown in FIGS. 1 to 3 is largely composed of a power compensation device 4000, a grid linkage device 100, and a power conversion control unit 200 for the grid linkage device 100. . The power conversion control unit 200 senses a three-phase system voltage/current and a voltage current output from a renewable energy source to calculate new and renewable energy generation power and system power, and controls the power of the system power.

Here, the power compensation control unit 400 includes: a power distribution unit 460 that calculates a compensation power to be supplied to the system in a low voltage acceptance operation situation and a share ratio of the compensation power to the renewable energy generation system; And a power compensation unit 420 that compensates for the power obtained by applying the share ratio to the compensated power through a system.

The illustrated power compensation system linkage device is a unique configuration for supporting LVRT (low voltage acceptance operation), and includes a power compensation control unit 400 for controlling to compensate for power to the system with power stored in the BESS 600; Grid Code power command generator 290 for outputting the LVRT effective and reactive power command according to the grid voltage; And a power distribution unit 460 that receives the power generation of renewable energy, grid power, and grid code power command and generates a shared power command to be output or compensated by the grid linkage device and the power compensator.

The illustrated power compensation grid connection device is a general configuration for supporting LVRT (low voltage acceptance operation), and a current controller 285 that generates a voltage value that is a two-phase synchronous coordinate value by reflecting the ^{LVRT current reference (i r*} _{dqs_GD ).} ; And an inverse coordinate converter 287 for converting the voltage value, which is the two-phase synchronization coordinate value, into a three-phase rectangular coordinate value.

The illustrated three-phase grid connection device 100 and the power conversion control unit 200 feed forward for the switch operation of the bridge circuit 30 using the current value of the system sensed by the current detection means 114 such as a Hall sensor. (Feedforward) control can be performed. At this time, the system phase estimated from the voltage value of the system sensed by the voltage detection means 112 such as an instrument transformer is applied, and a phase detector 207 is provided for this purpose. The feed forward control is generally implemented in the SVPWM method, and for this purpose, the SVPWM module 280 is provided. In addition, a DC voltage detector 140 is provided to provide a voltage value of a DC end (DC link end) as a kind of feedback parameter for the feed forward control. In order to improve the responsiveness of current control, a feedforward compensation method based on grid voltage and parameters is generally used. The feedforward compensation value may be composed of the level of the grid voltage and the value of the inductance voltage.

In the above-described feedforward control, each parameter derived from the sensed voltage value and current value is transformed between a three-phase rectangular coordinate value-a two-phase rectangular coordinate value-a two-phase synchronous coordinate value. For example, a three-phase system voltage value (Vac), which is a three-phase orthogonal coordinate value, is converted into a two-phase dq synchronous coordinate value (V ^r _dqs ) by the voltage value coordinate converter 201, and is a three-phase system that is a three-phase orthogonal coordinate value. The current value i _uvw is converted into a two-phase dq synchronous coordinate value i ^r _dqs by the current value coordinate converter 210.

The power conversion control unit 200 reflects the command value of the DC link voltage to the DC link voltage at the present time, and supplies it from the renewable energy generation system in a low voltage acceptance operation situation excluding the power required inside the renewable energy generation system. And a generated power calculation unit 270 that calculates possible generated power and provides it to the power distribution unit.

FIG. 4 shows an embodiment of a generated power calculation unit 270 that calculates power generated by renewable energy in FIG. 3.

The illustrated generated power calculation unit 270 includes a multiplier 271 for multiplying a current voltage value Vdc and a current current value Idc of DCLink to obtain a current generated power value; A subtractor 272 that calculates a difference value between a current voltage value (Vdc) and a command voltage value (V*dc) of DCLink; A voltage controller 273 calculating an offset power (power to be provided to a load belonging to a renewable energy generation system) from the difference between the two voltage values; And a subtractor 274 that subtracts _{the offset power from the current production power value and calculates the generated power P gen that} can be supplied to the system in the LVRT situation.

The illustrated generated power calculation unit 270 performs a kind of source power calculation for calculating generated power in new and renewable energy. The peculiar thing of the illustrated generation power calculation unit 270 is that the DC-Link voltage is not only calculated based on the voltage/current value of the DC link sensed at the time in calculating the generated power. It is calculated by compensating them together. Through this, it is possible to reflect the loss caused by switching and the hardware of the grid connection device, which is difficult to calculate, and through this, the power to be discharged to the grid or power compensator in the LVRT situation can be more accurately calculated.

FIG. 5 shows an embodiment of a power distribution unit 460 that calculates a distribution of power to be provided to a grid in the LVRT situation in FIG. 3.

The illustrated power distribution unit 460 is a configuration for limiting the apparent power, and calculates the product of the apparent power according to the grid code from ^{the active power value (P *} _GD ) according to the grid code and the command reactive power value (Q ^* _{GD ).} A squarer 461;

A subtractor (462) for obtaining a difference between the apparent power product calculated by the squarer and the apparent power product (S ² _{rate) output from the grid-connecting device;} Limiters (463, 464) to limit the difference; An inverse square (465) for inverse square of the limited difference; A subtractor 466 for subtracting the inverse squared value from the active power value (P ^* _{GD) according to the grid code;} The final command active power value (P ^* _comp ) divided by the power compensation device is calculated by ^{subtracting the total command active power value (P *} _{) (which may be the same as P gen} obtained in Fig. 4) from the output value of the subtractor 466. A subtractor 467 may be included.

The illustrated power distribution unit 460 is a component for calculating the power burden of the power compensation device 4000 and the grid connection device 200, and the command active power value (P ^* _GD ) and the command invalid according to the Grid Code An arc tangent group 471 that calculates a power phase θ _PW from a power value Q ^* _GD; Tangent groups (472, 473) for calculating the total command reactive power value (Q ^* ) by applying a tangent to the total command active power value (P ^* ) to the power phase (θ _{PW );} The power phase power compensation device to a (θ _PW) sharing minutes command active power value (P ^* _comp) an effective tangent group (472, 474 for calculating the applied tangent Power Compensator sharing minutes reference reactive power value (Q ^* _comp) ) Can be included.

The illustrated power distribution unit 460 first checks whether the output power defined by the Grid Code exceeds the rated apparent power that can be output from the renewable energy system interconnection device, and then limits it. If the limited active power output is greater than the power generated by new and renewable energy, it becomes the power to be compensated by the power compensator, and if it is smaller, the power to be absorbed by the power compensator. _{Meanwhile, for reactive power, after calculating the power angle (θ PW} ) based on the command in the Grid Code, the power compensation device 400 compensates for the calculated amount of active power, and the reactive power command (Q ^* _comp ) and the grid are connected. The device 200 calculates the reactive power command (Q ^* -Q ^* _{comp) to be compensated.} Through this, the system power controlled by the power compensation device 400 and the system linkage device 200 may be controlled as active/reactive power of the same power angle.

Depending on the implementation, the renewable energy grid connection device 4000 of FIGS. 1 and 2 enables grid connection of new and renewable energy without initial charging resistance. The initial charging resistance is an essential hardware configuration when connecting the grid-connected device to the grid, and through this, it can suppress the instantaneous current of DC-link current to the grid. Conventionally, a system in which three initial charging resistors are placed in a three-phase power supply is the most common, and a method of placing one initial charging resistor in the DC link stage has also been proposed. When the BESS 600 provided in the illustrated grid linkage device 4000 uses a battery of an appropriate capacity, grid linkage (always use) is possible without initial charging resistance.

6 is a flowchart illustrating a method of connecting a system during system recovery that can be performed in the power compensation system connecting device of FIG. 1.

The grid connection method according to the illustrated flow chart may be carried out by the power compensation device 4000, and accordingly, the power compensation device 4000 includes a grid voltage in a state in which the renewable energy generation system is separated from the grid. When it is restored to normal, power may be provided until the voltage of the DCLink reaches a predetermined reference value of the peak voltage between lines of the restored system.

The illustrated grid connection method includes the steps of monitoring the grid voltage in a state in which the renewable energy generation system is separated from the grid, that is, in a state in which the grid link switch 115 is open (S110) (S120); When the grid voltage is restored to normal, calculating a peak voltage between lines of the grid (S130); Supplying the power stored therein to the DC link (S140); Checking whether the DC link voltage is equal to or greater than a predetermined reference value (80% in the drawing) of the peak voltage between lines (S150); If the DCLink voltage is higher than a predetermined reference value of the peak voltage between lines, stopping power supply to the DCLink and disconnecting the connection with the renewable energy generation system (S160); And closing the grid-connected switch 115 and instructing the power conversion control unit 200 to control the grid-connected power (S180).

In the illustrated S110 state in which the switch connected to the grid is OFF and the switch of the grid interconnecting device is also OFF, it is checked whether the grid voltage is restored (S120). Since the peak voltage between lines of the grid voltage appears as the magnitude of the DC link voltage, it is calculated and controlled by gradually increasing the grid voltage from 0 to the peak voltage between lines with the power compensation device 4000 (that is, controlling the ramp voltage). S140). Accordingly, the power stored in the power compensation device 4000 is reflected as the DC link voltage. Even if the DC link voltage is grid-connected, after charging to a voltage that does not have a problem (80% of the peak voltage between lines), the voltage control of the power compensator is stopped and all link switches of the power compensator 4000 are turned off (S160). In this state, the grid connection switch 115 is turned on to perform grid connection (S170), and power control is performed while the switch of the grid connection device is turned on (S180).

FIG. 7 is a block diagram showing a relationship between another embodiment of a power compensation apparatus applicable to FIG. 1 and other configurations.

The illustrated power compensation device includes an energy storage medium 800 for storing energy in the form of mechanical potential energy due to inertia or gravity; An energy converter 900 in the form of a motor generator for converting energy stored in the energy storage medium into electric power; A DC conversion circuit 540 for converting the power output from the energy converter into DC; A compensation-side conversion circuit 520 for converting DC power of the DC conversion circuit and AC power of the system; And a power compensation control unit 400-1 for controlling the compensation-side conversion circuit to supply the power stored in the BESS to the system in a low-voltage-accepting operation situation.

The flywheel is suitable as the energy storage medium 800 in that the frequency of the system power can be adjusted together, but it is not limited thereto, and a pumping power generation facility, a compressed air storage device, a heat storage energy storage device, etc. may be applied.

The illustrated energy storage method uses an energy storage method in which energy stored in a physical energy storage medium in the form of physical/mechanical potential energy is output through a generator in the form of a prime mover.

The illustrated power compensation control unit 400-1 receives a compensation power command from the grid connection device 100 and/or the power conversion control unit 200, and serves as a DC conversion circuit 540 and a compensation side as a power conversion device in the power compensation device. The conversion circuit 520 is controlled, and the controlled active and reactive power information and energy storage state information are transmitted to the grid connection device 100 and/or the power conversion control unit 200.

Here, the DC conversion circuit (S540) for controlling power generated from the energy storage medium performs power control for charging or discharging energy, and the compensation-side conversion circuit 520 connected to the system is a grid connection device for distributed power in the system. It plays the role of power control that absorbs or discharges the power generated by the device.

Those skilled in the art to which the present invention pertains, since the present invention may be implemented in other specific forms without changing the technical spirit or essential features thereof, the embodiments described above are illustrative in all respects and should be understood as non-limiting. Only do it. The scope of the present invention is indicated by the claims to be described later rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. .

10: system stage 112: voltage detection means
114: current detection means 115: grid-connected switch
130: conversion circuit 140: DC voltage detector
200: power conversion control unit 270: generation power calculation unit
290: power command generator 400: power compensation control unit
420: power compensation unit 460: power distribution unit
600: BESS 4000: power compensation device

Claims (8)

A grid-connected switch that connects the power transmission between the renewable energy generation system and the grid, and regulates the connection with the grid, and an isolation transformer that transmits AC power while blocking the direct current path of the grid and the renewable energy generation system; A grid connection device including a new and renewable side conversion circuit for converting AC of the insulation transformer and DC link of the new and renewable energy generation system;
A power conversion control unit for controlling a DC-AC conversion operation of the grid-connected device; And
A power compensation device that is connected between the grid-connected switch and the isolation transformer, and supplies power to the grid in step with the new and renewable energy generation system in a low-voltage receiving operation situation.
Power compensation system linkage device for a low voltage receiving operation comprising a.
The method of claim 1,
The power compensation device,
An energy storage medium that stores energy in the form of mechanical potential energy by inertia or gravity;
An energy converter in the form of a motor generator for converting energy stored in the energy storage medium into electric power;
A DC conversion circuit for converting power output from the energy converter into DC;
A compensation-side conversion circuit for converting DC power of the DC conversion circuit and AC power of the system; And
Power compensation control unit that controls the compensation-side conversion circuit to supply the power stored in the BESS to the system in a low-voltage-accepting operation situation
Power compensation system linkage device for a low voltage receiving operation comprising a.
The method of claim 1,
The power compensation device,
BESS that stores and discharges electric power in a battery or supercapacitor, which is a secondary battery;
A compensation-side conversion circuit for converting DC power of the BESS and AC power of the system; And
Power compensation control unit that controls the compensation-side conversion circuit to supply the power stored in the BESS to the system in a low-voltage-accepting operation situation
Power compensation system linkage device for a low voltage receiving operation comprising a.
The method according to claim 2 or 3,
The power compensation control unit
A power distribution unit that calculates a compensation power to be supplied to a system in a low-voltage receiving operation situation and a share of the compensation power with the renewable energy generation system; And
A power compensation unit that compensates for the power obtained by applying the share ratio to the compensated power by a system
Power compensation system linkage device for a low voltage receiving operation comprising a.
The method of claim 4,
The power conversion control unit,
By reflecting the command value of the DC link voltage to the DC link voltage at the present time, the generated power that can be supplied from the renewable energy power generation system is calculated in a low voltage receiving operation situation excluding the power required inside the renewable energy power generation system, and the Power compensation system linkage device for low voltage receiving operation, characterized in that provided to the power distribution unit.
The method of claim 1,
The power compensation device,
When the grid voltage is restored to normal while the renewable energy generation system is disconnected from the grid, a low voltage acceptance operation that provides power until the voltage of the DC link reaches a predetermined reference value of the peak voltage between lines of the restored grid is performed. Power compensation grid connection device for
The method of claim 6,
The power compensation device,
Monitoring the grid voltage while the grid-connected switch is open;
When the grid voltage is restored to normal, calculating a peak voltage between lines of the grid;
Supplying the power stored therein to the DC link;
Checking whether the DC link voltage is greater than or equal to a predetermined reference value of a peak voltage between lines;
When the DC link voltage is greater than or equal to a predetermined reference value of the peak voltage between lines, stopping power supply to the DC link and disconnecting the connection with the renewable energy generation system; And
Closing the grid-connected switch and instructing the grid-connected power control to the power conversion control unit
Power compensation system linkage device for low voltage acceptance operation performing a grid linkage method comprising a.
It is connected between the grid connection switch that regulates the connection between the new and renewable energy power generation system and the grid, and the isolation transformer that insulates the new and renewable energy power generation system and the grid. In the grid connection method performed in a power compensation device that supplies power,
Monitoring the grid voltage while the renewable energy power generation system is separated from the grid;
When the grid voltage is restored to normal, calculating a peak voltage between lines of the grid;
Supplying the electric power stored therein to the DC link of the renewable energy generation system;
Checking whether the DC link voltage is greater than or equal to a predetermined reference value of a peak voltage between lines;
When the DC link voltage is greater than or equal to a predetermined reference value of the peak voltage between lines, stopping power supply to the DC link and disconnecting the connection with the renewable energy generation system; And
Closing the grid-connected switch and instructing grid-connected power control for renewable energy generation
System connection method comprising a.

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