JP2013153547A - Power leveling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power leveling device that maintains a predetermined value of DC voltage with high responsiveness despite a high capacity capacitor employed in a DC circuit.SOLUTION: AC power conversion means 6 performs a power charge/discharge between a power system and a capacitor 5 such that a current detected by a current detector 63 matches an AC current command Ip based on a surplus or deficit of power of the power system. DC power conversion means 4 delivers power between power storage means 3 and the capacitor 5 so that a current detected by a current detector 43 matches a DC current command Irf that is the sum of a DC current command Ir based on a differential voltage between the capacitor 5 and a predetermined value to be maintained and a feed-forward current command If calculated by feed-forward control means 9 on the basis of the AC current command Ip.

Description

  In the power supply system composed of an AC power supply and a load, the present invention charges and discharges the power corresponding to the fluctuation of the load power to the power system so that the power capacity of the AC power supply matches the leveled power. The present invention relates to a power leveling device capable of performing the above.

FIG. 5 shows an apparatus configuration disclosed in Patent Document 1 as this type of power leveling apparatus.
Reference numeral 1 denotes a three-phase AC power source (hereinafter simply referred to as an AC power source). A load 2 receives power from the AC power source 1. The AC power source 1 and the load 2 are connected by a three-phase three-wire power system line.

  The power leveling apparatus includes a power storage unit 3, a DC power conversion unit 4, a DC intermediate capacitor 5, an AC power conversion unit 6, a DC voltage control unit 7, and a charge / discharge power control unit 8. The DC intermediate capacitor 5 is simply referred to as a capacitor 5 below.

  The power storage means 3 is connected to one end of the DC power conversion means 4. The other end of the DC power conversion means 4 is connected to a DC terminal of the AC power conversion means 6 via a capacitor 5. The AC terminal of the AC power conversion means 6 is connected to the power system.

  In this power leveling device, the charge / discharge power control means 8 compares the power consumed by the load 2 with a predetermined leveled power. The power consumed by the load 2 can be calculated by detecting the system voltage and the current flowing through the load 2. Further, the leveled power is load power commensurate with the output capacity of the AC power source 1 and is determined to be maintained at a predetermined value when viewed from the AC power source 1.

  When the power consumed by the load 2 is smaller than the leveled power, the charge / discharge power control unit 8 sets the power command for charging the power storage unit 3 with surplus power generated in the power system. Further, the charge / discharge power control means 8 outputs a direct current command Ir based on the charge power command.

  The direct current control means 44 operates the direct current power conversion means 4 so that the direct current detected by the current detector 43 matches the direct current command Ir. In this case, the chopper 41 steps down the power charged in the capacitor 5 and charges the power storage means 3. As a result, the voltage of the capacitor 5 (hereinafter referred to as DC voltage) decreases.

The voltage detector 51 detects the magnitude of the DC voltage and inputs the detected value to the DC voltage control means 7.
The DC voltage control means 7 outputs an AC current command Ip necessary for maintaining the DC voltage at a predetermined value. The alternating current control means 64 operates the inverter 61 so that the alternating current detected by the current detector 63 matches the alternating current command Ip. Due to the operation of the inverter 61, the surplus power of the power system is charged in the capacitor 5.

  On the other hand, when the power consumed by the load 2 is larger than the leveled power, the charge / discharge power control means 8 sets the power command for discharging the insufficient power generated in the power system from the power storage means 3. Further, the charge / discharge power control means 8 outputs a direct current command Ir based on the discharge power command.

  The direct current control means 44 operates the direct current power conversion means 4 so that the direct current detected by the current detector 43 matches the direct current command Ir. In this case, the chopper 41 boosts the electric power charged in the power storage unit 3 and charges the capacitor 5. Thereby, the voltage of the capacitor 5 rises.

  The DC voltage control means 7 outputs an AC current command Ip necessary for maintaining the DC voltage at a predetermined value. The alternating current control means 64 operates the inverter 61 so that the alternating current detected by the current detector 63 matches the alternating current command Ip. By the operation of the inverter 61, the power charged in the capacitor 5 is discharged to the power system.

  By the operation of the power leveling device, the power supplied from the AC power supply 1 to the power system is always maintained at the leveled power regardless of the fluctuation of the power consumed by the load 2.

JP 2002-199588 A

  However, the power leveling device described above operates so that the power charged / discharged from the power storage means 3 matches the charge / discharge power command calculated by the charge / discharge power control means 8. Power is exchanged between the power storage means 3 and the power system through the chopper 41 and the inverter 61.

  However, in the chopper 41 and the inverter 61, power loss occurs due to the on / off operation of the switching element. Therefore, the power actually discharged to the power system by the AC power conversion means 6 is the power obtained by subtracting the power loss generated by the chopper 41 and the inverter 61 from the discharge power command calculated by the charge / discharge power control means 8. Become. The power actually charged from the power system by the AC power conversion means 6 is the power obtained by adding the power loss generated in the chopper 41 and the inverter 61 to the charge power command calculated by the charge / discharge power control means 8. It becomes.

  That is, a deviation occurs between the power charged / discharged from the power leveling device to the power system and the surplus power and insufficient power of the power system. In particular, when the power leveling device discharges the insufficient power generated in the power system, it is necessary for the AC power supply 1 to supply the power loss generated in the power leveling device. Therefore, there is a problem that the AC power supply 1 must have a power capacity that is larger than the power corresponding to the leveled power.

  A capacitor 5 exists between the chopper 41 and the inverter 61. That is, the capacitor 5 is included in a DC voltage control loop that maintains the DC voltage at a predetermined value. For this reason, the response of the DC voltage control is delayed, and when the power consumption of the load 2 varies, the DC voltage varies. When the DC voltage fluctuates, the response of the power leveling device to the power fluctuation of the load 2 becomes slow. Therefore, there is a problem that the AC power supply 1 must have a power capacity that allows for further fluctuations in the load power.

  The present invention has been made to solve the above problems, and provides a power leveling device capable of discharging power equal to insufficient power generated in an electric power system and speeding up the response of DC voltage control. The purpose is to do.

  In order to achieve the above object, the first invention is connected to an electric power system including an AC power source and a load that is supplied with electric power from the AC power source. And a power leveling device including a capacitor connected to a DC circuit between the DC power conversion means and the AC power conversion means.

  The DC power conversion means performs a constant voltage control operation for maintaining the voltage of the capacitor at a predetermined value by transferring power between the power storage means and the capacitor, and the AC power conversion means is connected to the power system. It is characterized in that a charge control operation for charging the surplus power of the capacitor to the capacitor or a discharge control operation for discharging the insufficient power of the power system from the capacitor is performed.

Thereby, since the electric power equal to the electric power which is insufficient in the electric power system can be discharged by the AC power conversion means, the fluctuation of the load electric power viewed from the AC power source can be suppressed.
According to a second aspect of the present invention, in the power leveling device according to the first aspect, the direct-current power conversion means has a voltage difference between the voltage value of the capacitor and a predetermined value to be maintained, surplus power and shortage of the power system. A constant voltage control operation is performed based on a feedforward control amount corresponding to electric power.

Thereby, the response of the DC voltage control of the power leveling device can be made faster.
According to a third aspect, in the power leveling apparatus according to the second aspect, the feedforward control amount includes an amount corresponding to a differential amount between surplus power and insufficient power.

Thereby, the response of the DC voltage control of the power leveling device can be made faster.
4th invention is the electric power leveling apparatus which concerns on 2nd invention. The feedforward control amount adds the quantity corresponding to the surplus power and the shortage power and the quantity corresponding to the differential quantity of the surplus power and the shortage power. It is characterized by that.

Thereby, the response of the DC voltage control of the power leveling device can be made faster.
A fifth invention is characterized in that, in the power leveling device according to the third or fourth invention, the magnitude of the differential amount of the surplus power and the insufficient power is adjusted according to the capacitance value of the capacitor. To do.

  Thereby, the DC voltage control of the power leveling device can be optimized according to the capacitance value of the capacitor.

  According to the present invention, the AC power conversion means charges or discharges power equal to surplus power or insufficient power generated in the power system, so that fluctuations in load power viewed from the AC power source can be suppressed. Moreover, since the DC power conversion means performs DC voltage control based on the control amount corresponding to the surplus power and the insufficient power of the power system, the response of the DC voltage control can be made faster.

It is a figure for demonstrating embodiment of the power leveling apparatus which concerns on this invention. It is a figure for demonstrating the 1st Example of a feedforward control means. It is a figure for demonstrating the 2nd Example of a feedforward control means. It is a figure for demonstrating the 3rd Example of a feedforward control means. It is a figure for demonstrating the power leveling apparatus which concerns on a prior art.

  Hereinafter, embodiments of a power converter according to the present invention will be described with reference to FIGS. In FIG. 1, the same components as those shown in FIG. 5 are given the same reference numerals, and descriptions thereof are omitted.

FIG. 1 is a diagram for explaining an embodiment of a power leveling apparatus according to the present invention.
First, the main circuit configuration and the basic operation of the power leveling apparatus according to the present invention will be described.

  In this figure, the main circuit of the power leveling device is the power storage means 3, the DC power conversion means 4 connected to the power storage means 3, the AC power conversion means 6 connected to the power system, the DC power conversion means 4 and the AC power. The capacitor 5 is connected to a DC circuit between the converter 6 and the converter 5.

The voltage of the capacitor 5 is detected by a voltage detector 51.
The power storage means 3 is a battery capable of charging and discharging electric power. However, the power storage means 3 is not limited to a battery, and may be any one that can charge and discharge electric power, such as one that can mutually convert electrical energy and mechanical energy.

The main circuit of the DC power conversion means 4 is composed of a chopper 41 and a capacitor 42.
The chopper 41 includes a switching element series circuit in which switching elements are connected in series, and a reactor having one end connected to the connection point. The other end of the reactor is connected to the high potential terminal of the storage means 3. The low potential terminal of the switching element series circuit is connected to the low potential terminal of the power storage means. Further, both ends of the switching element series circuit are connected to the capacitor 5.

The capacitor 42 is connected to both ends of the power storage means 3. The capacitor 42 smoothes the voltage of the power storage means 3.
The direct current control means 44 generates a control signal for turning on and off the switching element of the chopper 41 in order to make the direct current detected by the current detector 43 coincide with the direct current command Irf. By the on / off operation of the switching element, the chopper 41 boosts the power of the power storage unit 3 and charges the capacitor 5, or reduces the power of the capacitor 5 to charge the power storage unit 3.

The main circuit of the AC power conversion means 6 includes an inverter 61 and a filter 62.
The inverter 61 includes three sets of switching element series circuits in which switching elements are connected in series. Both ends of each of the three sets of switching element series circuits are connected to a capacitor 5. The connection middle point of each of the three sets of switching element series circuits is an AC terminal and is connected to one end of the filter 62.

The other end of the filter 62 is connected to the power system. The filter 62 removes harmonic components of the current flowing between the inverter 61 and the power system.
The alternating current control means 64 generates a control signal for turning on and off the switching element of the inverter 61 in order to match the alternating current detected by the current detector 63 with the alternating current command Ip. By the on / off operation of the switching element, the inverter 61 converts AC power of the power system into DC power and charges the capacitor 5, or converts the DC power of the capacitor 5 into AC power and discharges it to the power system.

Next, the DC voltage control means 7a, charge / discharge power control means 8a, and feedforward control means 9 that characterize the present invention will be described.
The charge / discharge power control means 8a compares the power consumed by the load 2 with a predetermined leveled power. When the power consumed by the load 2 is smaller than the leveled power, the difference power between the leveled power and the power consumed by the load 2 is surplus power generated in the power system. The charge / discharge power control means 8a uses the surplus power as a power command for the AC power conversion means 6 to charge the capacitor 5. Further, an alternating current command Ip is output based on this charging power command.

  On the other hand, when the power consumed by the load 2 is larger than the leveled power, the difference power between the leveled power and the power consumed by the load 2 is insufficient power generated in the power system. The charge / discharge power control means 8a uses the insufficient power as a power command for the AC power conversion means 6 to discharge from the capacitor 5. Further, the charge / discharge power control means 8a outputs an alternating current command Ip based on this discharge power command.

  As described above, the AC power conversion means 6 operates so that the AC current detected by the current detector 63 matches the AC current command Ip output from the charge / discharge power control means 8a. As a result, surplus power generated in the power system is charged in the capacitor 5 or insufficient power generated in the power system is discharged from the capacitor 5.

  The DC voltage control means 7 a generates a direct current command Ir flowing between the power storage means 3 and the chopper 41 in order to make the voltage of the capacitor 5 detected by the voltage detector 51 coincide with a predetermined value. When the voltage of the capacitor 5 is larger than a predetermined value, the direct current command Ir is a current command for causing a current to flow from the chopper 41 to the power storage means 3. On the other hand, when the voltage of the capacitor 5 is smaller than a predetermined value, the direct current command Ir is a current command for causing a current to flow from the power storage means 3 to the chopper 41.

  The DC current control unit 44 receives a DC current command Irf obtained by adding a DC current command Ir output from the DC voltage control unit 7a and a feedforward current command If output from a feedforward control unit 9 described later. The

  As described above, the DC power conversion means 4 operates so that the current detected by the current detector 43 matches the DC current command Irf. As a result, the power of the power storage unit 3 is charged into the capacitor 5 or the power of the capacitor 5 is charged into the power storage unit 3.

The feedforward control means 9 calculates the feedforward current command If using the alternating current command Ip output from the charge / discharge power control means 8a.
FIG. 2 is a block diagram for explaining a first embodiment of the feedforward control means 9.

  The feedforward control means 9 of this embodiment uses a value obtained by multiplying the alternating current command Ip output from the charge / discharge power control means 8a and the first gain by the calculation means 91 as the feedforward current command If. To do.

The first gain is a gain for adjusting the magnitude of the feedforward current command If.
FIG. 3 is a block diagram for explaining a second embodiment of the feedforward control means 9.

  The feedforward control means 9 of this embodiment uses the value obtained by subtracting the primary delay amount of the alternating current command Ip from the alternating current command Ip by the computing means 94, that is, the differential amount of the alternating current command Ip. Let it be If. The differential amount of the AC current command Ip is calculated from the AC current command Ip by multiplying the value obtained by passing the AC current command Ip through the low-pass filter 92 and the second gain by the calculation means 93. This value is obtained by subtracting by means 93.

  The second gain is a gain for overshooting the feedforward current command If over a predetermined amount to speed up the DC voltage control. The magnitude of the second gain is adjusted according to the capacitance value of the capacitor 5. For example, when the capacitance value of the capacitor 5 is large, the second gain is set to a large value, and when the capacitance value is small, the second gain is set to a small value.

FIG. 4 is a block diagram for explaining a third embodiment of the feedforward control means 9.
The feedforward control means 9 of this embodiment further calculates a value obtained by adding the AC current command Ip output from the charge / discharge power control means 8a and the differential amount of the AC current command Ip by the calculation means 95. A value obtained by multiplying the first gain by means 91 is defined as feedforward current command If. The differential amount of the alternating current command Ip is the same as the differential amount of the alternating current command Ip described in the second embodiment.

  As described above, the power leveling apparatus according to the present invention includes the charge / discharge power control means 8a for controlling the AC power conversion means 6 and the direct current in order to charge or discharge the capacitor 5 with surplus power or insufficient power generated in the power system. DC voltage control means 7a for controlling the power conversion means 4 is provided. By providing such DC voltage control means 7a and charge / discharge power control means 8a, the power leveling device can suppress fluctuations in load power viewed from the AC power supply 1.

  Furthermore, the power leveling apparatus according to the present invention includes feedforward control means 9 for calculating a feedforward current command If using the alternating current command Ip output from the charge / discharge power control means 8a. By adding the feedforward current command If to the DC current command Ir, the power leveling device can speed up the response of the DC voltage control. As a result, even when the power consumption of the load 2 changes suddenly, fluctuations in the load power viewed from the AC power source 1 can be suppressed at high speed.

  In addition, the 1st-3rd Example of the feedforward control means 9 demonstrated above is an example, Comprising: The feedforward control means 9 is not limited to the structure shown in FIGS. That is, the feedforward control means 9 may take other configurations as long as it calculates a control amount for feedforward control of a DC voltage using the AC current command Ip.

  The feedforward control means 9 calculates the feedforward current command using the alternating current command output from the charge / discharge power control means 8a, but feeds using the charge / discharge power command instead of the alternating current command. A forward current command may be calculated.

  Further, the configurations of the DC power conversion means 4 and the AC power conversion means 6 shown in FIG. 1 are merely examples, and are not limited to the above-described configurations, and other configurations may be adopted as long as the same functions can be exhibited. .

  DESCRIPTION OF SYMBOLS 1 ... AC power supply, 2 ... Load, 3 ... Power storage means, 4 ... DC power conversion means, 5 ... Capacitor, 6 ... AC power conversion means, 7, 7a ... DC voltage control means, 8, 8a ... charge / discharge power control means, 9 ... feed forward control means, 10 ... addition means.

Claims (5)

In a power leveling device connected to a power system composed of an AC power source and a load that receives power supply from the AC power source,
The power leveling device includes: power storage means; direct current power conversion means connected to the power storage means; alternating current power conversion means connected to the power system; and direct current between the direct current power conversion means and the alternating current power conversion means. With a capacitor connected to the circuit,
The DC power conversion means performs a constant voltage control operation for maintaining the voltage of the capacitor at a predetermined value by transferring power between the power storage means and the capacitor.
The AC power conversion means performs a charge control operation for charging the capacitor with surplus power of the power system, or a discharge control operation for discharging insufficient power of the power system from the capacitor.
A power leveling device characterized by that.   The DC power conversion means is configured to control the constant voltage control based on a voltage difference between a voltage value of the capacitor and a predetermined value to be maintained, and a feedforward control amount corresponding to the surplus power and the insufficient power. The power leveling apparatus according to claim 1, wherein the power leveling apparatus performs an operation.   The power leveling device according to claim 2, wherein the feedforward control amount includes an amount corresponding to a differential amount of the surplus power and the insufficient power.   The feedforward control amount is obtained by adding an amount corresponding to the surplus power and the insufficient power and an amount corresponding to a differential amount of the surplus power and the insufficient power. The power leveling device described.   5. The power leveling device according to claim 3, wherein a magnitude of the differential amount between the surplus power and the insufficient power is adjusted according to a capacitance value of the capacitor. .

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