JP2015104209A - Power leveling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power leveling device which can control the charge and discharge power of a flywheel device as per a charge and discharge command.SOLUTION: A power leveling device 2a for compensating power variation at a system interconnection point by using a FW device 1 including a flywheel and an induction motor coupled therewith includes a frequency command operation block 40 for operating a frequency command from an effective power command (P command), i.e., a charge and discharge command to an interconnection inverter 4a connected with the system interconnection point, and a variable voltage variable frequency power supply 20 having the DC side connected to the DC link with the interconnection inverter 4a, and performing V/f control of the induction motor of the FW device 1 by using a frequency command operated by the frequency command operation block 40.

Description

  The present invention relates to a power leveling device that compensates for power fluctuations at a grid connection point using a flywheel device as a large-capacity power storage device.

  In recent years, there are an increasing number of cases where renewable energy represented by solar power generation and wind power generation is connected to an electric power system. However, the amount of power generated by renewable energy fluctuates depending on natural factors such as the amount of solar radiation and wind conditions. Voltage and frequency fluctuate, and in the worst case, a large-scale power outage may occur. Therefore, in order to compensate for power fluctuations of renewable energy, a power leveling device using a large-capacity power storage device is installed to achieve power leveling. In many cases, chemical storage devices such as lead batteries and Li-ion batteries are used as large-capacity storage devices. However, in areas where maintenance is difficult, such as remote islands, flywheels are chemical-less storage devices. The number of cases using devices (hereinafter abbreviated as FW devices) is increasing.

Referring to FIG. 3, the conventional power leveling device 2 using the FW device 1 is connected to the grid connection point connected to the commercial grid power supply 3 for controlling the active power (P) and the reactive power (Q). It is connected to the inverter 4. The interconnection inverter 4 controls the active power (P) at the grid connection point based on the active power command (P command) from the charge / discharge command calculation block 5 and the reactive power command from the charge / discharge command calculation block 5. The reactive power (Q) at the grid connection point is controlled based on (Q command). The charge / discharge command calculation block 5 includes a voltage V of the grid connection point detected by the grid point voltage detector 6, a current I _{inv of} the grid inverter 4 detected by the grid inverter current detector 7, and a load current detection. the load current I _L in the load 9 is detected by the vessel 8, P command and Q command from the voltage V _dc of the DC link section that connects the electric power leveling apparatus 2 interconnection inverter 4 detected by the DC voltage detector 10 And The power leveling device 2 includes a variable voltage variable frequency power source (VVVF) 20 connected to the interconnection inverter 4 and a DC voltage constant control block 30. The DC voltage constant control block 30 calculates a frequency command from the voltage V _dc of the DC link unit connecting the interconnection inverter 4 and the power leveling device 2 detected by the DC voltage detector 10, and the VVVF 20 Based on the frequency command calculated in the control block 30, the FW device 1 (induction motor that drives the flywheel) is V / f controlled, and the voltage V _dc of the DC link unit that connects the interconnection inverter 4 and the VVVF 20 is It was controlled to be constant (see, for example, Patent Document 1).

JP 2012-114994 A

However, in the prior art, when the rotational speed of the FW device 1 decreases, it is difficult to keep the voltage V _dc of the DC link section connecting the interconnection inverter 4 and the VVVF 20 constant, and the mechanical energy stored in the FW device 1 It is difficult to discharge all of them, resulting in regenerative expiration, and the FW device 1 cannot be effectively charged and discharged.

  The objective of this invention is providing the electric power leveling apparatus which can control the charging / discharging electric power of FW apparatus 1 according to charging / discharging instruction | command in view of said subject.

The power leveling apparatus according to the present invention is configured as follows in order to achieve the above object.
The power leveling device of the present invention is a power leveling device that compensates for power fluctuations at a grid connection point using a flywheel device including a flywheel and an induction motor coupled to the flywheel. A frequency command calculation unit that calculates a frequency command from a charge / discharge command to a grid connection inverter connected to the grid connection point, a DC side is connected to a DC link unit with the grid connection inverter, and the frequency command calculation unit And a variable voltage variable frequency power source that performs V / f control of the induction motor of the flywheel device using the calculated frequency command.
Furthermore, in the power leveling device according to the present invention, the DC voltage of the DC link unit with the interconnection inverter may be controlled to be constant by the interconnection inverter.
Furthermore, in the power leveling device according to the present invention, the frequency command calculation unit is configured such that the charge / discharge command is P _m , the frequency command is f _n , the sampling time is T _s , and the frequency command before sampling is f _{n −1} , where p is the number of motor pole pairs of the induction motor and J _m is the moment of inertia of the flywheel,
f _n = f _n-1 + (p / 2π) ² · (T _s P _m / J _m f _n-1 )
You may make it calculate by.
Furthermore, in the power leveling apparatus according to the present invention, the charge / discharge command includes the voltage of the grid connection point, the current of the grid connection inverter, the load current, the grid connection inverter, and the variable voltage variable frequency power supply. And may be calculated based on the DC voltage of the DC link unit.

  ADVANTAGE OF THE INVENTION According to this invention, there exists an effect that the charging / discharging electric power of a flywheel apparatus can be controlled according to a charging / discharging instruction | command by calculating directly the frequency instruction | command of the induction motor of a flywheel apparatus from charging / discharging instruction | command.

It is a block diagram which shows the structure of embodiment of the power leveling apparatus which concerns on this invention. It is a block diagram which shows the structure of the frequency instruction | command calculation block shown in FIG. It is a block diagram which shows the structure of the conventional power leveling apparatus.

  Next, embodiments of the present invention will be specifically described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and a part of the description is omitted.

  The power leveling device 2a of the present embodiment is a device that levels power by charging and discharging power to the FW device 1 that is a power storage device. As shown in FIG. 1, a variable voltage variable frequency power supply (VVVF) ) 20 and a frequency command calculation block 40. The FW device 1 includes a flywheel and an induction motor coupled to the flywheel, and stores rotational energy by rotating the flywheel by the induction motor at the time of charging. It is converted into electrical energy and output.

  The VVVF 20 has an AC side connected to the induction motor of the FW device 1 and a DC side connected to a DC link portion with the interconnection inverter 4a. The VVVF 20 supplies electric energy between the DC link unit with the interconnection inverter 4a and the FW device 1 by supplying variable frequency AC to the induction motor of the FW device 1 and controlling the rotational speed of the flywheel. Give and receive.

The interconnection inverter 4 a is connected to the grid connection point connected to the commercial grid power supply 3 on the AC side, and connected to the DC link portion with the VVVF 20 on the DC side. The interconnection inverter 4a controls the reactive current for controlling the reactive power (Q) at the grid connection point based on the reactive power command (Q command) from the charging / discharging command calculation block 5a, and the charge / discharge command. Based on the DC voltage command (V _dc command) from the calculation block 5a, the effective current for making the voltage V _dc of the DC link part connecting the interconnection inverter 4a and the power leveling device 2a constant is controlled.

The charge / discharge command calculation block 5a includes the voltage V of the grid connection point detected by the grid point voltage detector 6, the current I _{inv of} the grid inverter 4a detected by the grid inverter current detector 7, and the load current detection. the load current I _L in the load 9 is detected by the vessel 8, the real power command from the voltage V _dc of the DC link section that connects the interconnection inverter 4a and the power leveling device 2 detected by the DC voltage detector 10 (P Command), reactive power command (Q command), and DC voltage command (V _dc command). The charge / discharge command calculation block 5a outputs the calculated Q command and V _dc command to the interconnection inverter 4a, and outputs the calculated P command, which is a charge / discharge command, to the frequency command calculation block 40 of the power leveling device 2a. Output.

  The frequency command calculation block 40 calculates a frequency command from the P command calculated by the charge / discharge command calculation block 5a, and the VVVF 20 calculates the FW device 1 (flywheel) based on the frequency command calculated by the frequency command calculation block 40. V / f control of the induction motor that drives

Next, a calculation method for calculating the frequency command from the P command performed in the frequency command calculation block 40 will be described in detail.
As a premise, the machine output of the FW device 1 is controlled (unit: W), and the FW device 1 rotation is calculated based on the synchronous frequency without considering the slippage during acceleration / deceleration of the FW device 1. It is assumed that there is no viscous friction and disturbance torque. Under these conditions, assuming that the torque during acceleration / deceleration is T _m , the inertia moment of the flywheel in the FW device 1 is J _m , and the rotational angular velocity is ω _m , the following relational expression is derived from the equations of the mechanical system.

Here, when [Equation 1] is discretized, the sampling time is T _s , the current angular velocity of sampling is ω _mn , and the rotational angular velocity before sampling is ω _mn−1 , the following equation is rewritten.

Further, when the number of motor pole pairs is p and the rotational angular velocity ω _mn is rewritten with ω _mn-1 by the power supply frequencies f _n and f _n−1 , the following equation is obtained.

Next, the relationship between the machine output P _m and the torque T _m is expressed by the following equation. The power supply frequency f _n−1 is a value before one sampling.

Next, substituting [Equation 4] into [Equation 3] and rearranging the current frequency f _n yields the following equation.

According to [Equation 5], by calculating the P command calculated by the charge / discharge command calculation block 5a as the machine output P _m , it is possible to calculate the frequency command f _n that becomes constant power one by one. Therefore, the P command calculated by the charge and discharge command computing block 5a and input to the frequency command calculation block 40, one by one and calculates the frequency instruction f _n using Equation 5 with the frequency command computation block 40, VVVF20 frequency command the induction motor of FW device 1 according to the operation frequency command f _n in operation block 40 by controlling V / f, it is possible to control the charge-discharge electric power of the FW device 1 during acceleration or deceleration in the street command value.

  Referring to FIG. 2, the frequency command calculation block 40 includes a gain block 41, a divider 42, an adder 43, a slip correction block 44, a frequency limit block 45, and a delay block 46. The calculation of [Formula 5] is performed.

The gain block 41 is a block in which the constant parts in [Formula 5] are collectively gained, and the input P command (P _m ) is multiplied by K _f expressed by the following equation.

Next, the operation result of the gain block 41 is divided by the divider 42 by the frequency command f _n−1 delayed by one sampling by the delay block 46, and the operation result of the divider 42 is divided by the delay block 46 by the adder 43. The frequency command f _n−1 delayed by one sampling is added.

Although the calculation result of the adder 43 is the calculation result of [Equation 5], when the charge / discharge power is large and the acceleration / deceleration time of the FW device 1 is short, the rotational speed of the FW device 1 is shifted by the amount of slip. Therefore, a slip correction block 44 that grasps the slip of the FW device 1 in advance and corrects the slip frequency with respect to the calculated frequency command f _n (calculation result of the adder 43) is provided. Further, when outputting the final frequency command f _n, it is provided frequency limit block 45 to limit the maximum frequency and the minimum frequency in operating the FW device 1.

With this configuration, when the FW device 1 is charged, the sign of the P command input to the frequency command calculation block 40 is given by +, so that the calculated frequency command f _n is increased from the previous frequency command f _n−1. As a result, the FW device 1 is accelerated and accumulates rotational energy. On the other hand, when the FW device 1 is discharged, by giving the sign of the P command input to the frequency command calculation block 40 as-, the calculated frequency command f _n decreases from the previous frequency command f _n−1 . The FW device 1 decelerates, and rotational energy is converted into electrical energy and output.

In the present embodiment, the control that is the base of the induction motor of the FW device 1 is V / f control. However, the control that is the base of the induction motor of the FW device 1 may be replaced with vector control speed control. . In this case, the same constant power control of the FW device 1 can be performed by converting the frequency command f _n into a speed command.

As described above, the present embodiment uses the power leveling device 2a that compensates for power fluctuations at the grid connection point using the FW device 1 including the flywheel and the induction motor coupled to the flywheel. A frequency command calculation block 40 that calculates a frequency command from an active power command (P command) that is a charge / discharge command to the grid connection inverter 4a connected to the grid connection point, and the DC side is connected to the grid connection inverter 4a. And a variable voltage variable frequency power supply 20 that V / f-controls the induction motor of the FW device 1 using the frequency command calculated by the frequency command calculation block 40.
With this configuration, the charge / discharge power of the FW device 1 can be controlled in accordance with the charge / discharge command by directly calculating the frequency command of the induction motor of the FW device 1 from the charge / discharge command.

Further, in the present embodiment, the DC voltage V _{dc at} the DC link section with respect to the interconnection inverter 4a is controlled to be constant by the interconnection inverter 4a.
With this configuration, the DC link portion DC voltage V _dc between the interconnection inverter 4a and the variable voltage variable frequency power supply 20 is controlled to be constant on the interconnection inverter 4a side, so that the FW device 1 can be made efficient without being regeneratively expired. It is possible to charge and discharge well.

Further, in the present embodiment, the frequency command calculation block 40 includes a charge / discharge command P _m , a frequency command f _n , a sampling time T _s , a frequency command before sampling f _n−1 , and an induction motor motor. If the number of pole pairs is p and the moment of inertia of the flywheel is J _m ,
f _n = f _n-1 + (p / 2π) ² · (T _s P _m / J _m f _n-1 )
It is comprised so that it may calculate by.
With this configuration, the frequency command can be calculated from an active power command (P command) that is a charge / discharge command to the interconnection inverter 4a by a simple calculation.

Further, in this embodiment, the charge and discharge command includes a voltage V of the grid interconnection point, and the current I _inv of interconnection inverter 4a, the load current I _L, and interconnection inverter 4a and the variable voltage variable frequency power source 20 It is calculated on the basis of the DC voltage V _dc of the DC link section.

The configurations, shapes, sizes, and arrangement relationships described in the above embodiments are merely schematically shown to the extent that the present invention can be understood and implemented, and numerical values and compositions (materials) of the respective components. Is merely an example. Therefore, the present invention is not limited to the described embodiments, and can be modified in various forms without departing from the scope of the technical idea shown in the claims.
For example, in the present embodiment, the control method of the induction motor of the FW device 1 has been described. However, the control method of the present invention is not limited to the FW device 1 and the induction motor is accelerated / decelerated at a constant power. It is applicable as a control method.

DESCRIPTION OF SYMBOLS 1 FW apparatus 2 Power leveling apparatus 2a Power leveling apparatus (this Embodiment)
3 Commercial system power supply 4, 4a Linkage inverter 5, 5a Charge / discharge command calculation block 6 Linkage point voltage detector 7 Linkage inverter current detector 8 Load current detector 9 Load 10 DC voltage detector 20 Variable voltage variable frequency power supply (VVVF)
30 DC voltage constant control block 40 Frequency command calculation block (frequency command calculation unit)
41 Gain Block 42 Divider 43 Adder 44 Slip Correction Block 45 Frequency Limit Block 46 Delay Block

Claims (4)

A power leveling device that compensates for power fluctuations at a grid connection point using a flywheel device including a flywheel and an induction motor coupled to the flywheel,
A frequency command calculation unit that calculates a frequency command from a charge / discharge command to the interconnection inverter connected to the grid interconnection point;
A variable voltage variable frequency power source having a DC side connected to a DC link unit with the interconnection inverter and V / f controlling the induction motor of the flywheel device using the frequency command calculated by the frequency command calculation unit; A power leveling apparatus comprising:   2. The power leveling apparatus according to claim 1, wherein a DC voltage of a DC link portion with the interconnection inverter is controlled to be constant by the interconnection inverter. The frequency command calculation unit is configured such that the charge / discharge command is P _m , the frequency command is f _n , the sampling time is T _s , the frequency command before sampling is f _n−1 , and the number of motor pole pairs of the induction motor is p When the inertia moment of the flywheel is J _m ,
f _n = f _n-1 + (p / 2π) ² · (T _s P _m / J _m f _n-1 )
The power leveling device according to claim 1, wherein the power leveling device performs calculation according to claim 1.   The charge / discharge command is based on a voltage at the grid connection point, a current of the grid inverter, a load current, and a DC voltage of a DC link unit between the grid inverter and the variable voltage variable frequency power supply. The power leveling apparatus according to claim 1, wherein the power leveling apparatus is operated.

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