JP6346791B2 - Electric power leveling device - Google Patents

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. 5, the conventional power leveling device 2 using the FW device a <b> 1 is connected to the active power (P) and reactive power (Q) of the grid connection point connected to the commercial power supply 3. 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) b1 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 f _FW 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 VVVFb 1 Based on the frequency command f _FW calculated by the constant voltage control block 30, V / f control is performed on the FW device a1 (induction motor that drives the flywheel), and the DC link unit that connects the interconnection inverter 4 and VVVFb1 The voltage V _dc is controlled to be constant (see, for example, Patent Document 1). When power cannot be compensated for by one FW device a1, as shown in FIG. 6, a plurality of VVVFb1 to VVVFbn and FW devices a1 to FW devices an are connected in parallel to increase the compensation capacity.

JP 2012-114994 A

However, in the prior art, in order to keep the voltage V _dc of the DC link unit connecting the interconnection inverter 4 and the plurality of VVVFb1 to VVVFbn constant, the plurality of FW devices a1 to FW devices an are all set to the same frequency command f. _Even if the charge / discharge power is small, the FW devices a1 to FW device an cannot be individually charged / discharged and the operation efficiency is not good.

  In view of the above problems, an object of the present invention is to provide a power leveling device that can perform charge / discharge control individually for a plurality of FW devices and has high operational efficiency.

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 plurality of flywheel devices including a flywheel and an induction motor coupled to the flywheel. A plurality of variable voltage variable frequency power supplies connected to a DC link portion with the interconnection inverter connected to the grid interconnection point on the DC side, respectively provided corresponding to the plurality of flywheel devices; The one or more flywheel devices that perform charging / discharging are selected based on the charge / discharge command from the charge / discharge command calculation block and the number of rotations of the plurality of flywheel devices, and the selected flywheel device. FW group control unit for calculating each individual power command with respect to the FW group, and an individual frequency indicator based on the individual power command calculated by the FW group control unit. The flywheel device selected by the FW group control unit using the individual frequency command calculated by the frequency command calculation unit. V / f control the induction motor, and the FW group control unit divides the charge / discharge command by the individual power command that provides maximum efficiency when charging / discharging the flywheel device. Is calculated as the number of the flywheel devices that perform charging / discharging, and when the charging / discharging command is a charging command, charging is performed in order of decreasing rotational speed from among the plurality of flywheel devices. The flywheel device to be operated is selected, the individual power commands for maximum efficiency are allocated in the order of the low rotation speed in the selected flywheel device, and the remaining ones are selected. Allotting to the flywheel device having the highest rotational speed, and when the charge / discharge command is a discharge command, the discharge is performed in the order of the high rotational speed from among the plurality of flywheel devices. Select a flywheel device, assign individual power commands for maximum efficiency in order of increasing rotation speed among the selected flywheel devices, and select the remaining flywheel device with the lowest rotation speed among the selected flywheel devices. It is characterized by allocating .
Et al is in the power leveling apparatus according to the present invention, the DC voltage of the DC link part of the interconnection inverter, by the interconnection inverter may be controlled to be constant.
Further, in the power leveling apparatus according to the present invention, the frequency command calculation unit may be configured to output the individual power command P _m , the individual frequency command f _n , a sampling time T _s , and the individual frequency command before one sampling. 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, respectively, f _n = f _n −1+ (p / 2π) ² · (T _s P _m / J _m You may calculate by fn _-1 ).
Furthermore, in the power leveling apparatus according to the present invention, the charge / discharge command calculation block includes the voltage at the grid connection point, the current of the grid connection inverter, the load current, the grid connection inverter, and the variable voltage variable. The charge / discharge command may be calculated based on the DC voltage of the DC link unit with the frequency power supply. _

  According to the present invention, constant control of the DC voltage of the DC link unit is performed on the connected inverter side, and the frequency command of each FW device connected to a plurality of units is created individually from the charge / discharge command of the entire system. Therefore, charging / discharging control can be performed for a plurality of FW devices individually, and the operational efficiency can be improved.

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 FW group control part shown in FIG. It is a block diagram which shows the structure of the frequency instruction | command calculation block shown in FIG. It is a figure which shows the example of FW loss data memorize | stored in the FW loss data memory | storage part shown in FIG. It is a block diagram which shows the structure of the conventional power leveling apparatus provided with FW apparatus. It is a block diagram which shows the structure of the conventional power leveling apparatus provided with the several FW 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 / discharging power to n FW devices a1 to an that are power storage devices. As shown in FIG. It is composed of a variable voltage variable frequency power supply (VVVF) c1 to cn provided for each of a1 to an and a frequency command calculation block 40. The FW devices a1 to an each include a flywheel and an induction motor coupled to the flywheel. When charging, the flywheel is rotated by the induction motor to store rotational energy, and when discharging, the induction motor operates as a generator. Let the rotational energy of the flywheel be converted into electrical energy and output.

  The VVVFc1 to cn are connected to the induction motors of the FW devices a1 to an on the AC side, respectively, and the DC side is connected to the DC link portion with the interconnection inverter 4a. The VVVFc1 to cn supply the AC of variable voltage and variable frequency to the induction motors of the FW devices a1 to an, respectively, and control the rotational speed of the flywheel, whereby the DC link unit and the FW device with the interconnection inverter 4a are controlled. Send and receive electrical energy between a1 and an.

The interconnection inverter 4a is connected to the grid interconnection point connected to the commercial grid power supply 3 on the AC side, and connected to the DC link portion with VVVFc1 to cn 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 linkage point voltage detector 6, the current I _{inv of} the grid inverter 4 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 4 and the power leveling device 2a 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. Note that the output of the P command, the Q command, and the V _dc command is performed at predetermined intervals such as a unit of several seconds.

A FW group control unit 50 is provided in the torque command calculation block 40.
The FW group control unit 50 has three control modes: a charging mode, a discharging mode, and a standby mode. Since the sign of the P command is used for switching determination of each operation mode, it is defined as + for a charge command and-for a discharge command. The charging mode is an operation mode that is performed when surplus power is generated and the sign of the P command is + and the charging command is, and the FW group control unit 50 performs charging from one of the FW devices a1 to an. Alternatively, a plurality of FW devices ai (i is an integer of 1 to n, and will be described as an integer of i = 1 to n hereinafter), and an individual power command that is an individual charging command for the selected FW device ai _Calculate P _FWai . The discharge mode is an operation mode that is performed when insufficient power is generated and the sign of the P command is-and the command is a discharge command, and the FW group control unit 50 performs one discharge from the FW devices a1 to an. Alternatively, a plurality of FW devices ai (i is an integer of 1 to n, which will be described as an integer of i = 1 to n hereinafter), and an individual power command that is an individual discharge command for the selected FW device ai _Calculate P _FWai . The standby mode is an operation mode performed when there is neither surplus power nor insufficient power and the P command is 0, and the FW group control unit 50 stands by without calculating the individual power command P _FWai that is a charge / discharge command. . When determining the standby mode, if the P command is only 0, the transition to the standby mode may not be performed. Therefore, the standby mode may be determined within a predetermined range centered on 0. good. Further, in the FW device ai that is not selected in the standby mode or the charge mode and the discharge mode, the loss is reduced when the induction motor is also turned off and completely free-runned, but it takes time to restart. Since there is a case where high-speed power compensation cannot be performed, excitation should be continued at the minimum necessary level.

  As shown in FIG. 2, the FW group control unit 50 includes an SOC limiter 51, an individual power command calculation unit 52, and an FW loss data storage unit 52. In addition, you may make it input the output frequency of FW apparatus a1-an instead of FW rotation speed.

  The SOC limiter 51 performs an SOC limiter process that narrows down the P command calculated by the charge / discharge command calculation block 5a in accordance with the charging state of the entire FW devices a1 to an. The SOC limiter 51 reduces the accumulated energy of the FW devices a1 to an to a predetermined reference range (for example 50 SOC limiter processing is performed in order to maintain (˜60%). The SOC limiter 51 grasps the total stored energy based on the FW rotation speeds of the FW devices a1 to an, and the total stored energy is higher than a preset upper limit value (for example, an upper limit of 60% of the reference range of stored energy). If it exceeds 58%, which is slightly lower, the P command (charge command) is narrowed down, and the total stored energy is set to a preset lower limit (for example, 52% slightly higher than the lower limit 50% of the reference range of stored energy). If it falls below, the P command (discharge command) is narrowed down. The active power command after the limiter processing by the SOC limiter 51 is set as a P ′ command.

  The FW loss data storage unit 52 is a storage unit such as a ROM or a flash memory, and stores FW loss data indicating the amount of power loss when charging / discharging the FW devices a1 to an. As the FW loss data, for example, as shown in FIG. 4A, mechanical loss characteristic data indicating loss characteristics corresponding to the rotation speeds of the FW devices a1 to an can be used. According to the mechanical loss characteristic data shown in FIG. 4 (a), it can be seen that the rate of increase / decrease in loss increases as the rotational speed increases. In addition, since a plurality of FW devices a1 to an are basically made with the same specifications, only one type of FW loss data is required, but when using a plurality of FW devices with different characteristics, each FW loss It is also possible to store data. Further, the FW loss data may be provided as a table, or may be a method of calculating and storing the converted FW loss data one by one.

The individual power command calculation unit 53 selects one or a plurality of FW devices ai that perform charging / discharging based on the P ′ command output from the SOC limiter 51 and the FW rotation speeds of the FW devices a1 to an. The individual power command P _FWai for the selected FW device ai is calculated.

First, the selection operation of the FW devices a1 to an by the individual power command calculation unit 53 will be described.
As shown in the following equation, the individual power command calculation unit 53 divides the absolute value of the P ′ command output from the SOC limiter 51 by the maximum power P _FW that can be charged / discharged by one FW device ai. The number _Nc to be selected is calculated. However, since the number _Nc is an integer, when a value after the decimal point is generated, the value is increased by one.

Next, when the mechanical loss characteristic data is stored as the FW loss data in the FW loss data storage unit 52, the individual power command calculation unit 53 reduces the mechanical loss based on the mechanical loss characteristic data. The number _Nc of FW devices ai calculated by [Equation 1] is selected from the FW devices a1 to an. When the mechanical loss characteristic data shown in FIG. 4A is stored in the FW loss data storage unit 52, in the charging mode, the FW rotation speed is calculated from [Mathematical formula 1] in the order from the lowest FW device a1 to an. and was selected FW device ai of number _{N c,} in the discharge mode, selects the number _{N c} of FW speed is calculated in a higher order equation (1) from the FW apparatus a1 to an. Thereby, the mechanical loss of FW apparatus a1-an can be decreased.

Next, as shown in the following equation, the individual power command calculation unit 53 divides the P ′ command output from the SOC limiter 51 by the number _Nc calculated by [Equation 1], thereby selecting the selected FW device. An individual power command P _FWai for each of a _i is calculated.

In this embodiment, the individual power command P _FWai is configured to be evenly allocated to the selected FW device ai. However, in the case of a charge command, the FW rotation speed is within the selected FW device ai. The maximum power P _FW may be allocated as the individual power command P _{FWai in ascending} order, and the remaining power _may be allocated to the highest FW rotation speed among the selected FW devices ai. In the case of a discharge command, the maximum power P _FW is allocated as the individual power command P _{FWai in} order of _increasing FW rotation speed in the selected FW device ai, and the remaining FW rotation speed is selected in the selected FW device ai. You may make it allocate to the thing with the lowest.

The frequency command calculation block 40 calculates the individual frequency command f _FWai from the individual power command P _FWai calculated by the individual power command calculation unit 53, and _VVVFc1 to cn are the individual frequencies calculated by the frequency command calculation block 40. Based on the command f _FWai , the FW devices a1 to an (induction motors that drive the flywheel) are subjected to V / f control.

Next, the calculation method of the individual frequency command in the frequency command calculation block 40 will be described in detail.
As a premise, the mechanical output (unit is W) of the FW device ai is controlled, and the FW device ai rotation is calculated based on the synchronous frequency without taking into account the slip at the time of acceleration / deceleration of the FW device ai. It is assumed that there is no viscous friction and disturbance torque. Under these conditions, if the torque during acceleration / deceleration is T _m , the inertial moment of the flywheel in the FW device ai 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 3] 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.

Furthermore, when the number of motor pole pairs is p, and the rotational angular velocity ω _mn and the rotational angular velocity ω _mn−1 before one sampling are rewritten with the power source frequency f _n and the power source frequency f _n−1 before one sampling, respectively, can get.

Next, the relationship between the machine output P _m and the torque T _m is expressed by the following equation.

Next, substituting [Equation 6] into [Equation 5] and rearranging the current power supply frequency f _n yields

According to [ _Equation 7], by calculating the individual power command P _FWai calculated by the FW group control unit 50 as the machine output P _m , the power supply frequency f _n is calculated one by one as the individual frequency command f _FWai for constant power It is possible.

Therefore, the individual power command P _FWai calculated by the FW group control unit 50 is input to the frequency command calculation block 40, and the individual frequency command f _FWai is calculated one by one using the [ _Equation 7] in the frequency command calculation block 40, and VVVFFi. V / f controls the induction motor of the FW device ai according to the individual frequency command f _FWai calculated by the frequency command calculation block 40, thereby controlling the charge / discharge power of the FW device ai during acceleration / deceleration according to the command value. Can do.

  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 [Expression 7] is performed.

The gain block 41 is a block obtained by _gaining together the constant parts in [ _Expression 7], and multiplies the input individual power command P _FWai (P _m ) by K _{f expressed} by the following equation.

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

The calculation result of the adder 43 is the calculation result of [Equation 7]. However, when the charge / discharge power is large and the acceleration / deceleration time of the FW device ai is short, the rotational speed of the FW device ai is shifted by the amount of slip. Therefore, a slip correction block 44 that grasps the slip of the FW device ai in advance and corrects the slip frequency for the calculation result of the adder 43 is provided. In addition, when outputting the final individual frequency command f _FWai , a frequency limiting block 45 is provided for limiting the maximum frequency and the minimum frequency in operating the FW device ai.

With this configuration, when the FW device ai is charged, the sign of the P command input to the frequency command calculation block 40 is given by + so that the calculated individual frequency command f _FWai is delayed by one previous sampling. Since the frequency command f _FWai increases, the FW device ai accelerates and accumulates rotational energy. On the other hand, during discharge of the FW device ai is the sign of P command to be input to the frequency command calculation block 40 - by giving in, it computed the individual frequency command f _FWai is 1 sampling sequence delayed by separate frequency command f _FWai Therefore, the FW device ai 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 ai is V / f control. However, the control that is the base of the induction motor of the FW device ai may be replaced with vector control speed control. . In this case, the same constant power control of the FW device ai can be performed by converting the frequency command f _n into a speed command.

Further, the motor efficiency characteristic data (see FIG. 4B) indicating the efficiency according to the load factor of the FW device ai (charge / discharge power / rated capacity of the FW device ai) is stored in the FW loss data storage unit 52 as FW loss data. You may make it memorize. According to the motor efficiency characteristic data shown in FIG. 4B, the individual power command P _FWai that _{achieves the} maximum efficiency when the load factor is approximately 80% and the maximum efficiency can be derived. Accordingly, the number _Nc to be selected may be calculated by dividing the absolute value of the P ′ command output from the SOC limiter 51 by the individual power command P _FWai that _provides the maximum efficiency. Then, in the case of the charge command, the individual power command P _FWai having the maximum efficiency is allocated in the order from the lowest FW rotation speed among the selected FW devices ai, and the FW rotation speed is selected among the remaining FW devices ai. You may make it allocate to the highest thing. Further, in the case of a discharge command, the individual power command P _FWai that _{gives the} maximum efficiency is allocated in order of increasing FW rotation speed in the selected FW device ai, and the FW rotation speed is selected among the FW devices ai that have selected the rest. You may make it allocate to the lowest thing.

Further, inverter efficiency characteristic data (see FIG. 4C) indicating the efficiency in accordance with the load factor of VVVFFi (charge / discharge power / VVVFFi rated capacity) is stored in the FW loss data storage unit 52 as FW loss data. You may do it. According to the inverter efficiency characteristic data shown in FIG. 4C, the maximum efficiency is obtained when the load factor is approximately 80%, and the individual power command P _FWai that _{achieves the} maximum efficiency can be derived. Accordingly, the number _Nc to be selected may be calculated by dividing the absolute value of the P ′ command output from the SOC limiter 51 by the individual power command P _FWai that _provides the maximum efficiency. Then, in the case of the charge command, the individual power command P _FWai having the maximum efficiency is allocated in the order from the lowest FW rotation speed among the selected FW devices ai, and the FW rotation speed is selected among the remaining FW devices ai. You may make it allocate to the highest thing. Further, in the case of a discharge command, the individual power command P _FWai that _{gives the} maximum efficiency is allocated in order of increasing FW rotation speed in the selected FW device ai, and the FW rotation speed is selected among the FW devices ai that have selected the rest. You may make it allocate to the lowest thing.

Further, a plurality of FW loss data are stored among the mechanical loss characteristic data shown in FIG. 4A, the motor efficiency characteristic data shown in FIG. 4B, and the inverter efficiency characteristic data shown in FIG. 4C. It may be stored in the unit 52 as FW loss data. In this case, the FW group control unit 50 minimizes the loss during charging / discharging based on the machine, mechanical loss characteristic data, motor efficiency characteristic data, and inverter efficiency characteristic data stored in the FW loss data storage unit 52. The selection of the FW device ai and the calculation of the individual power command P _FWai to be broken into the selected FW device ai can be performed.

As described above, this embodiment compensates for power fluctuations at the grid connection point using a plurality of FW devices a1 to an including a flywheel and an induction motor coupled to the flywheel. A plurality of power leveling devices 2a, each having a DC side connected to a DC link unit connected to a grid connection inverter 4a connected to a grid connection point and provided corresponding to a plurality of FW devices a1 to an Variable voltage variable frequency power source VVVFc1-cn, charge / discharge command (P command) to interconnection inverter 4a, and one or a plurality of units that perform charge / discharge based on FW rotation speed of a plurality of FW devices a1-an FW devices a1 to an and FW group control unit 50 for calculating the individual power command P _FWai for the selected FW device ai, and the individual calculated by the FW group control unit 50 A frequency command calculation block 40 that calculates an individual frequency command f _FWai based on the power command P _FWai , and the variable voltage variable frequency power supplies VVVFc1 to _cn use the individual frequency command f _FWai calculated by the frequency command calculation block 40. Then, the induction motor of the FW device ai selected by the FW group control unit 50 is subjected to V / f control.
With this configuration, constant control of the DC voltage of the DC link unit is performed on the connected inverter 4a side, and frequency commands for each of the FW devices a1 to an connected to a plurality of units are individually created from charge / discharge commands for the entire system. Therefore, charge / discharge control can be performed individually for the plurality of FW devices a1 to an, and operational efficiency can be improved.

Further, in the present embodiment, the FW group control unit 50 calculates the number of FW devices a1 to an that perform charging and discharging based on the P command, and when the P command is a charging command, a plurality of FW devices. When the FW device ai that performs charging in the order of low rotation speed is selected from a1 to an, and the P command is a discharge command, discharging is performed in descending order of rotation speed from the plurality of FW devices a1 to an. The FW device ai to perform is selected.
With this configuration, the mechanical loss of the FW devices a1 to an can be reduced.

Further, in the present embodiment, the FW group control unit 50 performs charging / discharging by dividing the P command by the individual power command P _FWai that becomes maximum efficiency when charging / discharging the FW devices a1 to an. The number of FW devices ai is calculated. Further, in the case of the charge command, the FW group control unit 50 allocates the individual power command P _FWai that is the maximum efficiency in the order of the lowest rotation speed among the selected FW devices ai, and the remaining FW devices ai that have selected the remaining power Among the selected FW devices ai, the individual power command P _FWai having the highest efficiency is allocated in the order of the highest rotation number and the remaining FW devices are selected. Allocate to the lowest number of rotations in ai.
With this configuration, the FW device ai can be charged and discharged efficiently, and loss can be reduced.

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 regenerative invalidation is not caused and the FW device a1 is made efficient. 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 individual frequency command f _FWai for each of the FW devices _a1 to an 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, interconnection inverter 4a and the variable voltage variable frequency power supply c1~ Calculation is performed based on the DC voltage V _dc of the DC link unit with cn.

  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.

a1-an flywheel (FW) devices b1-bn, c1-cn variable voltage variable frequency power supply (VVVF)
2 Power leveling device 2a Power leveling device (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 30 DC voltage constant control block 40 Frequency command calculation block (frequency command calculation block)
41 Gain Block 42 Divider 43 Adder 44 Slip Correction Block 45 Frequency Limit Block 46 Delay Block 50 FW Group Control Unit 51 SOC Limiter 52 FW Loss Data Storage Unit 53 Individual Power Command Calculation Unit

Claims (4)

A power leveling device that compensates for power fluctuations at a grid connection point using a plurality of flywheel devices including a flywheel and an induction motor coupled to the flywheel,
A plurality of variable voltage variable frequency power supplies provided corresponding to the plurality of flywheel devices, connected to a DC link portion with a grid inverter connected to the grid connection point on the DC side,
Based on the charge / discharge command from the charge / discharge command calculation block and the number of rotations of the plurality of flywheel devices, one or more flywheel devices that perform charging / discharging are selected, and the selected flywheel device is selected. FW group control unit for calculating each individual power command;
A frequency command calculation unit that calculates an individual frequency command based on the individual power command calculated by the FW group control unit;
The variable voltage variable frequency power supply V / f-controls the induction motor of the flywheel device selected by the FW group control unit using the individual frequency command calculated by the frequency command calculation unit ,
The FW group control unit performs charge / discharge by dividing the charge / discharge command by the individual power command, which is maximum efficiency when charging / discharging the flywheel device, and rounding up the value after the decimal point by one. Calculated as the number of flywheel devices, and when the charge / discharge command is a charge command, select the flywheel device that performs charging in order of decreasing rotation speed from among the plurality of flywheel devices, and select In the flywheel device, the individual power command for maximum efficiency is allocated in the order of the low rotation number, the remaining one is allocated to the flywheel device having the highest rotation number, and the charge / discharge command is allocated. Is a discharge command, the flywheel device that performs discharge in descending order of the number of rotations is selected from the plurality of flywheel devices, and the selected flywheel device is selected. Allocated individual power command having the maximum efficiency rotation speed is higher order in the Eel device, power leveling apparatus, characterized in that allocated to those rpm in the flywheel device selected remaining lowest. DC voltage of the DC link part between the interconnection inverter, power leveling apparatus according to claim 1, characterized in that it is controlled to be constant by the interactive inverter. The frequency command calculation unit is configured such that the individual power command is P _m , the individual frequency command is f _n , the sampling time is T _s , the individual frequency command before sampling is f _n−1 , and the number of motor pole pairs of the induction motor P and the moment of inertia of the flywheel as 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 calculation block includes: a voltage of the grid connection point; a current of the grid inverter; a load current; and a DC voltage of a DC link unit of the grid inverter and the variable voltage variable frequency power supply. power leveling device according to any one of claims 1 to 3, wherein that you calculate the charging and discharging command based.

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