JP5630236B2 - Power storage device - Google Patents

Description

  The present invention relates to a power storage device including a flywheel as a power storage medium.

  Conventionally, a power storage device including a flywheel has been proposed (see, for example, Patent Document 1). In an uninterruptible power supply using the power storage device, power is normally supplied to a three-phase induction generator motor having a rotor with a flywheel in the power storage device, the flywheel is rotated, and rotational energy is stored in the flywheel. During a power outage, the rotational energy of the flywheel is converted into electrical energy to supply power to the external load.

JP 2003-111494 A

  Usually, the voltage between the DC buses of the inverter supplying the variable frequency alternating current to the three-phase induction motor that rotates the flywheel, that is, the DC link voltage is kept constant, but for some reason (for example, from the load When the DC link voltage rises due to regenerative energy, there is a problem that the inverter stops overvoltage due to the protection function. In order to prevent overvoltage, there are several methods conventionally proposed as methods for processing the energy of the DC link unit. (1) Return the regenerative energy to a commercial AC power source. However, this method requires a switching element and a control circuit in order to make the AC / DC converter connected to the AC power source reversible. In addition, when the AC power supply fails, the energy of the DC link portion cannot be returned to the AC power supply. (2) Provide a dedicated load for preventing overvoltage in the DC link unit to consume energy. However, this method can suppress an increase in the DC link voltage during a power failure of the AC power supply, but requires a switching element and a control circuit.

  In view of the above problems, an object of the present invention is to provide a power storage device that can prevent an inverter from being overvoltage stopped.

In order to achieve the above object, a power storage device according to the present invention is configured as follows.
The power storage device of the present invention includes a flywheel, a generator motor coupled to the flywheel, and an inverter having an AC side connected to the generator motor and a DC side connected to a DC link unit, from the inverter to the generator motor A power storage device that exchanges electric energy with the DC link unit by supplying AC of variable frequency to control the rotational speed of the flywheel, wherein the inverter detects the voltage of the DC link unit a voltage detector which, based on the rotational speed of the detection voltage from said voltage detector the flywheel, the voltage command value of the DC link portion from the first voltage command value and the first voltage command value big and the second voltage command value setting portion for setting to one of a voltage command value, to the detection voltage from said voltage detector and the rotational speed of the flywheel Zui and, the maximum rotational speed setting unit for setting to one of the maximum rotation speed rpm Maximum rotation speed of the first maximum speed and said first maximum rotational speed greater than the second of the flywheel The voltage command value setting unit operates when the voltage command value of the DC link unit is used as the first voltage command value, and the detected voltage from the voltage detector is greater than the first voltage command value. When the value is larger than the first predetermined value, the voltage command value of the DC link unit is switched to the second voltage command value, and the maximum rotation number setting unit sets the maximum rotation number of the flywheel rotation number. When operating at the first maximum rotational speed, if the detected voltage from the voltage detector is equal to or greater than the first predetermined value, the maximum rotational speed of the flywheel is set to the second rotational speed. It is characterized by switching to the maximum rotation speed .
Further, the power storage device of the present invention, when the above configuration odor Te, the voltage command value setting unit is operating a voltage command value of the DC link section as said second voltage command value, before Symbol voltage detection When the detected voltage from the detector is not equal to or higher than the first predetermined value and the rotational speed of the flywheel is equal to or lower than the first maximum rotational speed , the voltage command value of the DC link unit is set to the first voltage command. switch to a value, when the detected voltage from the voltage detector is not less than the maximum number of revolutions speed of the first of said first of said flywheel, not more than a predetermined value, a voltage command value of the DC link section Without changing , when the maximum rotational speed setting unit is operating with the maximum rotational speed of the flywheel as the second maximum rotational speed, the detected voltage from the voltage detector is the first rotational speed. If the flywheel is not above the predetermined value When the rotation speed is equal to or less than the first maximum rotation speed, the maximum rotation speed of the flywheel is switched to the first maximum rotation speed, and the detection voltage from the voltage detector is set to the first maximum rotation speed. When the rotational speed of the flywheel is not equal to or greater than a predetermined value and is not less than or equal to the first maximum rotational speed, the maximum rotational speed of the flywheel is not changed .
The power storage device according to the present invention is characterized in that, in the above configuration, the first predetermined value is equal to or greater than the first voltage command value and equal to or less than an overvoltage value at which the inverter stops .
The power storage device of the present invention includes a flywheel, a generator motor coupled to the flywheel, and an inverter having an AC side connected to the generator motor and a DC side connected to a DC link unit. A power storage device that exchanges electric energy with the DC link unit by supplying variable frequency AC to a generator motor and controlling the rotational speed of the flywheel, wherein the inverter is connected to the DC link unit When regenerative energy is generated from the load that is generated, the voltage command value of the DC link unit is changed from the first voltage command value to the first voltage command based on the voltage of the DC link unit and the rotational speed of the flywheel. Is set to a second voltage command value that is greater than the value, and based on the voltage of the DC link unit and the rotational speed of the flywheel, Wherein the maximum rotation speed rotation speed of the Lee wheel is set to the first maximum rotation maximum rotation speed of the first maximum rotational speed greater than the second from the number of.

  ADVANTAGE OF THE INVENTION According to this invention, the electrical storage apparatus which can prevent that an inverter carries out an overvoltage stop can be provided.

It is a block diagram which shows the structure of the power supply device using the electrical storage apparatus which concerns on this embodiment of this invention. It is a block diagram which shows the electrical storage apparatus which concerns on this embodiment of this invention. It is a flowchart explaining operation | movement of the electrical storage apparatus which concerns on this embodiment of this invention. It is a state transition diagram explaining operation | movement of the electrical storage apparatus which concerns on this embodiment of this invention. It is another application example of the power storage device according to the embodiment of the present invention. It is another application example of the power storage device according to the embodiment of the present invention.

  DESCRIPTION OF EMBODIMENTS Preferred embodiments (examples) of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a configuration of a power supply device using a power storage device according to this embodiment of the present invention. The power supply apparatus 10 converts the AC power supplied from the AC power supply 11 from the AC input terminal 12, the AC output terminal 14 for connecting the load 13, and the AC power supply 11 into DC power. AC / DC converter 16 to be supplied to DC link unit 15, power storage device 17 connected to DC link unit 15, and DC power supplied to DC link unit 15 is converted to desired AC power to load 13. A DC / AC converter 18 to be supplied and a DC output terminal 25 connected to the DC link unit 15 are provided. A load 19 is connected to the DC output terminal 25. The power storage device 17 includes an inverter 20 and a flywheel 21.

  FIG. 2 is a block diagram showing the power storage device 17. The inverter 20 controls the rotational speed of the flywheel by supplying a variable frequency alternating current to a generator motor (not shown, but a synchronous machine, an induction machine, etc.) coupled to the flywheel (FW). The inverter circuit 22, the control unit 23, and a voltage detector 27 are included. The inverter circuit 22 is a switching circuit having a three-phase bridge configuration, and is connected to the DC link unit 15 by a wiring 24 and is connected to the flywheel 21 by a wiring 26. The wiring 24 is provided with a voltage detector 27 for detecting the voltage of the wiring 24, that is, the voltage (DC link voltage) of the DC link unit 15 (see FIG. 1). The flywheel 21 includes a flywheel and a generator motor coupled to the rotary shaft of the flywheel.

  The control unit 23 detects the voltage value detected by the voltage detector 27 and the two voltage command values Vdc1 * (first voltage command value) and Vdc2 * (first voltage command value) selected by the switch 29 controlled by the switch control unit 28. 2), a deviation calculating unit 30 that calculates a deviation from any one of the two voltage command values) and a PID control unit 31 that performs PID control based on the deviation. Further, at the subsequent stage of the PID control unit 31, two flywheel maximum rotation speeds N1 (first maximum rotation speed) and N2 (second maximum rotation speed) selected by the switch 33 controlled by the switch control section 32 are provided. ) Is provided to limit the number of rotations of the flywheel. The output from the PID control unit 31 is input to the PWM control unit 35 through the limiter 34, the switching operation of the inverter circuit 22 is controlled by the PWM control unit 35, and the alternating current of the variable frequency is supplied to the flywheel 21. The rotation speed of the wheel is controlled. Further, the switch control unit 28 controls the switch 29 based on the detection voltage from the voltage detector 27 and the signal from the limiter 34 (the rotational speed of the flywheel), and the voltage command value Vdc1 * or the voltage command value Vdc2 * Is selected and output to the deviation calculation unit 30. The switch control unit 32 controls the switch 33 based on the detected voltage from the voltage detector 27 and the signal (the rotational speed of the flywheel) from the limiter 34, and either the maximum rotational speed N1 or the maximum rotational speed N2. Is output to the limiter 34. The switch control unit 28, the switch 29, the voltage command value Vdc1 *, and the voltage command value Vdc2 * constitute a voltage command value setting unit 36, and the switch control unit 32, the switch 33, the maximum rotation speed N1, and the maximum rotation speed N2. Constitutes the maximum rotational speed setting unit 37. Details will be described with reference to the flowchart of FIG.

  The power storage device 17 of the present embodiment having the above configuration is a power storage device that keeps the DC link voltage at a certain value or more, and when the DC link voltage rises above the overvoltage prevention voltage level (first predetermined value). The inverter 20 that drives the flywheel 21 has a control system that prevents the overvoltage stop. In this system, energy (such as regenerative energy) that causes overvoltage in the DC link unit 15 is absorbed by the flywheel 21 to prevent overvoltage. The features of this method are as follows. (1) No additional switching element or control circuit is required. (2) Since the overvoltage prevention function is automatically performed by the inverter 20, no external control signal is required. (3) It has a flywheel maximum rotation speed N1 during normal operation and a flywheel maximum rotation speed N2 during overvoltage prevention operation. That is, there are two types of upper limiters for the rotational speed of the flywheel. (4) It has a voltage command value Vdc1 * during normal operation and a voltage command value Vdc2 * during overvoltage prevention operation. (5) The difference between the rotational energy at the maximum flywheel rotational speed N2 and the rotational energy at the maximum flywheel rotational speed N1 is the amount of energy that can be absorbed to prevent overvoltage.

  Then, the energy that causes the DC link voltage to increase (regenerative energy from the loads 13 and 19) is stored in the flywheel 21, and the increase in the voltage of the DC link unit 15 is suppressed. For this energy storage, the flywheel 21 is controlled at a value slightly lower than the maximum rotational speed during normal operation. The flywheel rotation speed during normal operation takes into account the amount of energy regenerated from the loads 13 and 19. decide.

  Thereby, the voltage of the DC link unit 15 is stabilized, and the overvoltage stop of the inverter 20 that drives the flywheel 21 and other devices connected to the DC link unit 15 is prevented. Since the stored regenerative energy is supplied to the loads 13 and 19 again, energy waste is reduced.

  Next, operation | movement of the electrical storage apparatus 17 which concerns on this embodiment of this invention is demonstrated.

(Constant control of DC link voltage)
The inverter 20 controls the flywheel 21 so as to keep the DC link voltage at a constant value (voltage command value Vdc1 * or Vdc2 *). This DC link voltage is detected by the voltage detector 27.

  When the DC link voltage is high, the rotational speed of the flywheel 21 is increased, the rotational energy is stored in the flywheel 21, and the DC link voltage is controlled to decrease. When the DC link voltage is low, the rotational speed of the flywheel 21 is decreased, electric energy is extracted from the flywheel 21, and control is performed to increase the DC link voltage (general PID process).

(Overvoltage prevention operation)
Two inverters 20 that drive the flywheel 21 are set with two maximum rotational speeds (upper limiters for rotational speed) of the flywheel 21. The upper limit maximum rotational speeds are N1 and N2. Moreover, let the lower limit rotation speed of the flywheel 21 be N0.

  N0 is the minimum rotational speed at which electrical energy can be extracted from the flywheel 21. N1 is the maximum number of rotations of the flywheel during normal operation. N2 is the maximum rotation speed of the flywheel during the overvoltage prevention operation. N2 is larger than N1 (N2> N1). The difference between N1 and N2 is the amount of energy that can be stored in the flywheel 21 to prevent overvoltage.

  When the AC power supply 11 is operating normally, the DC link voltage input to the inverter 20 is referred to as a normal voltage (VdcS). The level at which the inverter 20 starts the overvoltage prevention operation is defined as an overvoltage prevention voltage level (VcdSV). The DC link voltage target values Vdc1 * and Vdc2 * controlled by the inverter 20 are set. Vdc1 * sets a DC link voltage target value during normal operation. Vdc2 * sets the DC link voltage target value during the overvoltage protection operation. These voltages are set according to the following relationship. Vdc1 * <VdcS <Vdc2 * <VdSV

(Explanation of operation)
The operation of the power storage device will be described with reference to the flowchart of FIG. 3 and the state transition diagram of FIG.

  First, the flowchart of FIG. 3 will be described.

Step S11: The switch control unit 28 and the switch control unit 32 determine whether or not the voltage detection value detected by the voltage detector 27 is equal to or higher than the overvoltage prevention voltage VdcSV (first predetermined value). If the detected voltage value is smaller than the overvoltage prevention voltage VdcSV, step S12 is executed. If the detected voltage value is equal to or higher than the overvoltage prevention voltage VdcSV, step S15 is executed.
Step S12: The switch control unit 28 and the switch control unit 32 determine whether or not the rotational speed of the flywheel 21 is equal to or less than N1 (second predetermined value) from the signal output from the limiter 34. If the rotational speed of the flywheel 21 is N1 or less, step S13 is executed. If the rotational speed of the flywheel 21 is greater than N1, step S14 is executed.
Step S13: The switch control unit 32 sets the maximum rotation speed limiter to N1 by the switch 33. Further, the switch control unit 28 sets the voltage command value to Vdc1 * by the switch 29. Then return.
Step S14: The switch control unit 32 maintains the current maximum rotational speed limiter by the switch 33. The switch control unit 28 maintains the current voltage command value for the switch 29. Then return.
Step S15: The switch control unit 32 sets the maximum rotation speed limiter to N2 by the switch 33. Further, the switch control unit 28 sets the voltage command value to Vdc2 * by the switch 29. Then return.

  Next, the state transition diagram of FIG. 4 will be described. FIG. 4A is a diagram showing a change in the rotational speed of the flywheel 21, and FIG. 4B is a diagram showing a DC link voltage.

(State 1) Preparatory operation A state from the state where the flywheel 21 is stationary until the lower limit rotational speed N0 is exceeded. The flywheel is accelerated to a certain number of revolutions (range T1 in FIG. 4).

(State 2) DC link voltage constant control state 1
The rotational speed of the flywheel 21 is controlled so that the DC link voltage becomes Vdc1 *. When the DC link voltage VdcS is supplied from the AC power supply 11, the rotational speed of the flywheel 21 increases because Vdc1 * <VdcS. Since the capacity of the inverter 20 is sufficiently smaller than the capacity of the AC power supply 11, the DC link voltage remains unchanged at VdcS. Therefore, the rotational speed of the flywheel 21 continues to increase and becomes N1 (range T2 in FIG. 4).

(State 3) DC link voltage constant control state 2
The rotational speed of the flywheel 21 is maintained in a constant state of N1 (range T3 in FIG. 4).

(State 4) Overvoltage state 1
When the rotational speed of the flywheel 21 is N1, if there is energy regeneration from the loads 13 and 19 in the DC link unit 15, energy cannot be stored in the flywheel 21, so the DC link voltage increases (T4 in FIG. 4). Range).

(State 5) Overvoltage state 2
When the DC link voltage exceeds VdcSV, inverter 20 changes the upper limit rotation speed of flywheel 21 of limiter 34 from N1 to N2, and the DC link voltage target value from Vdc1 * to Vdc2 *.
Since (current DC voltage)> (control target value) (VdcSV> Vdc2 *), the inverter 20 increases the rotational speed of the flywheel 21 to be in a state of N1 or more and N2 or less. If the capacity of the inverter 20 is larger than the regenerative capacity from the loads 13 and 19, the DC link voltage is controlled to Vdc2 * (range T5 in FIG. 4).

(State 6) Overvoltage state 3
The regeneration from the loads 13 and 19 ends, and the DC link voltage tries to return to the original voltage (VdcS). However, the inverter 20 tries to keep the DC link voltage at Vdc2 *, and thus the rotational speed of the flywheel 21. Is reduced and electric energy is supplied to the DC link unit 15 (range T6 in FIG. 4).

(State 7) Return to Normal Operation State When the rotational speed of the flywheel 21 becomes N1 or less, the inverter 20 changes the upper limit rotational speed of the flywheel 21 of the limiter 34 from N2 to N1, and sets the DC link voltage target value to Vdc2. Change from * to Vdc1 *. At this time, since (current DC voltage)> (control target value) (Vdc2 *> Vdc1 *), an attempt is made to increase the rotational speed of the flywheel 21, but the rotational speed of the flywheel 21 is the upper limit rotational speed. Because of N1, the rotational speed cannot be increased.
On the other hand, due to the power consumption of the loads 13 and 19, the DC link voltage gradually decreases and matches VdcS.
As a result, it becomes the same as the state 3 (the range of T7 in FIG. 4).

(State 8)
When the AC power supply 11 has a power failure, the DC link voltage decreases, so the inverter 20 reduces the rotational speed of the flywheel 21 and supplies electric energy to the DC link unit 15.
If the capacity of the inverter 20 is larger than the load capacity connected to the DC link unit 15, the DC link voltage is controlled to Vdc1 * and becomes stable (range T8 in FIG. 4).

  Thus, according to the power storage device of the present embodiment, it is possible to prevent the inverter from being overvoltage stopped.

  The power storage device 17 according to the present embodiment can be applied to the power supply device shown in FIG. 5 or the uninterruptible power supply device shown in FIG.

  In this embodiment, the signal for controlling the switch control unit 28 and the switch control unit 32 is a signal from the inside of the power storage device 17, but the switch control unit 28 and the switch control are also performed by a signal from the outside of the power storage device 17. The unit 32 can also be controlled. Further, in FIG. 2, it is described that the signal from the switch 29 is directly sent to the deviation calculating unit 30, but by providing a filter between the switch 29 and the deviation calculating unit 30, It is possible to make the switching smooth.

  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 the numerical values and the compositions (materials) of the respective components Is just an example. Therefore, the present invention is not limited to the described embodiments, and can be variously modified without departing from the scope of the technical idea shown in the claims.

  The power storage device according to the present invention is used as a power storage device used for an uninterruptible power supply or the like.

DESCRIPTION OF SYMBOLS 10 Power supply device 11 AC power supply 12 AC input terminal 13,40 Load 14 AC output terminal 15 DC link part 16 AC / DC converter 17 Power storage device 18 DC / AC converter 19, 42, 43 Load 20 Inverter 21 Flywheel 22 Inverter circuit 23 Control unit 24 Wiring 25 DC output terminal 26 Wiring 27 Voltage detector 28 Switch control unit 29 Switch 30 Deviation calculation unit 31 PID control unit 32 Switch control unit 33 Switch 34 Limiter 35 PWM control unit 36 Voltage command value setting unit 37 Maximum rotation speed Setting part 41 Rectifier

Claims (4)

A flywheel, a generator motor coupled to the flywheel, and an inverter having an alternating current side connected to the generator motor and a direct current side connected to a direct current link unit, supply alternating current of variable frequency from the inverter to the generator motor Then, by controlling the number of rotations of the flywheel, a power storage device that exchanges electric energy with the DC link unit,
The inverter is
A voltage detector for detecting the voltage of the DC link unit;
Based on the detected voltage from the voltage detector and the rotational speed of the flywheel, the voltage command value of the DC link unit is set to a first voltage command value and a second voltage command greater than the first voltage command value . A voltage command value setting unit to be set to any of the values,
Based on the detected voltage from the voltage detector and the rotation speed of the flywheel, the maximum rotation speed of the flywheel is set to a second maximum value greater than the first maximum rotation speed and the first maximum rotation speed . A maximum rotation number setting part to be set to any of the maximum rotation number ,
The voltage command value setting unit is
When the voltage command value of the DC link unit is operating as the first voltage command value, and the detected voltage from the voltage detector is greater than a first predetermined value greater than the first voltage command value , Switching the voltage command value of the DC link unit to the second voltage command value,
The maximum rotation speed setting unit is
When operating at the maximum rotational speed of the flywheel as the first maximum rotational speed, if the detected voltage from the voltage detector is greater than or equal to the first predetermined value, the rotation of the flywheel A power storage device that switches a maximum number of rotations to the second maximum number of rotations . The voltage command value setting unit is
When operating the voltage command value of the DC link unit as the second voltage command value,
When pre-Symbol detection voltage from the voltage detector is equal to or less than the maximum number of revolutions speed of the first of said first of said flywheel, not more than a predetermined value, said voltage command value of the DC link section first switch to the voltage command value of 1,
When the detected voltage from the voltage detector is not equal to or higher than the first predetermined value and the rotational speed of the flywheel is not equal to or lower than the first maximum rotational speed , the voltage command value of the DC link unit is not changed ,
The maximum rotation speed setting unit is
When operating the maximum rotation speed of the flywheel as the second maximum rotation speed,
When the detected voltage from the voltage detector is not equal to or higher than the first predetermined value and the rotational speed of the flywheel is equal to or lower than the first maximum rotational speed, the maximum rotational speed of the flywheel is Switch to the first maximum speed,
When the detected voltage from the voltage detector is not higher than the first predetermined value and the rotational speed of the flywheel is not lower than the first maximum rotational speed, the maximum rotational speed of the flywheel is not changed. The power storage device according to claim 1, wherein: The power storage device according to claim 1 , wherein the first predetermined value is equal to or greater than the first voltage command value and equal to or less than an overvoltage value at which the inverter stops . A flywheel, a generator motor coupled to the flywheel, and an inverter having an alternating current side connected to the generator motor and a direct current side connected to a direct current link unit, and supplying the generator motor with variable frequency alternating current from the inverter Then, by controlling the number of rotations of the flywheel, a power storage device that exchanges electric energy with the DC link unit,
The inverter is
When regenerative energy is generated from a load connected to the DC link part,
Based on the voltage of the DC link unit and the rotational speed of the flywheel, the voltage command value of the DC link unit is greater than the first voltage command value from the first voltage command value.
Set to
Based on the voltage of the DC link section and the rotational speed of the flywheel, a second maximum rotation in which the maximum rotational speed of the flywheel is greater than the first maximum rotational speed from the first maximum rotational speed. Set to number
A power storage device.

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