JP2009112175A - Power stabilization system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely bring out an absorbing effect in a power variation caused by charging/discharging of a power-storage unit, and to stabilize a trend in a power supply. <P>SOLUTION: Two systems of power-variation absorbing units 14, 15 comprising a bidirectional AC/DC converter 6 and a secondary battery 7 are provided to a distributing power source 3 connected to a power system 1. For example, in the unit 14, only a power variation in the charging direction is compensated by controlling to maintain the lower-limit voltage of the secondary battery; and in the unit 15, only the power variation in the discharging direction is compensated by controlling to maintain the upper-limit voltage of the secondary battery. The system is thus designed to absorb the power variation within the permissible capacity of the secondary battery. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a system that absorbs power fluctuations generated by a distributed power supply system such as wind power generation or solar power generation with a secondary battery, and stabilizes the power flow of a connected power system.

Distributed power sources such as wind power generation and solar power generation cause large tidal current fluctuations in the power system because generated power fluctuates greatly depending on environmental conditions. In general, a distributed power source using such natural energy is often connected to the end of the system and has high wiring impedance. For this reason, the system voltage fluctuates due to such a power flow fluctuation, which adversely affects other loads.
Therefore, a system has been developed that compensates for power fluctuations such as output fluctuations, load fluctuations, power fluctuations, etc., by absorbing or releasing power using a power storage means such as a secondary battery (for example, , See Patent Document 1).

FIG. 2 shows an example disclosed in Patent Document 1.
First, the power fluctuation absorber 5 inputs the output voltage and current of the distributed power supply 3 to the power detector 11 and calculates the generated power of the distributed power supply 3. Further, the voltage and current of the secondary battery 7 to be used are input to the secondary battery remaining capacity detector 12, and the remaining capacity is calculated by, for example, current integration calculation or a voltage-remaining capacity conversion table.

  The two detection signals are input to the control circuit 13 of the bidirectional AC / DC power converter 6, and the output power control signal of the converter 6 is calculated. That is, the control circuit 13 decreases the power release or power absorption of the secondary battery 7 when the power generation output of the distributed power source 3 increases, and increases the power output of the distributed power source 3 when the power generation output of the distributed power source 3 decreases. A power compensation command calculation function and an output power control function based on the compensation command are provided so as to reduce power absorption of the secondary battery 7 or increase power release. As a result, the power fluctuation at the connection point between the distributed power source 3 and the power fluctuation absorber 5 is compensated.

  However, in the bidirectional AC / DC converter 6 and the secondary battery 7, loss occurs during charging / discharging, so the remaining capacity of the secondary battery 7 gradually decreases as it is, and finally reaches the lower limit of the remaining capacity. The power fluctuation absorbing effect cannot be obtained. Similarly, when the average value of the active power fluctuation amount is biased in the direction of charging the secondary battery 7, the remaining capacity of the secondary battery 7 gradually increases as it is, and finally reaches the upper limit value of the remaining capacity. The power fluctuation absorbing effect cannot be obtained.

Therefore, various control methods have been proposed in order to correct the average bias of the charge / discharge amount of the secondary battery 7 and prevent the remaining capacity from sticking to the upper limit value and / or the lower limit value in the long term. ing.
For example, in Non-Patent Document 1, when the terminal voltage of the secondary battery (corresponding to the remaining capacity) exceeds a preset threshold value (two upper and lower threshold values are set in the terminal voltage allowable range), By correcting the output command value to the secondary battery so that it approaches the middle direction of the allowable voltage range (by adding the correction value to the compensation target value obtained by removing the fluctuation component from the active power measurement value of the distributed power source) The average bias of the battery charge / discharge amount is controlled.

Although there are various methods for detecting the remaining capacity of the secondary battery 7, it is general to use an integrated amount of charge / discharge current (current time product (Ah)) for a certain time (for example, Patent Document 2). reference).
JP 2006-287998 A JP 07-192769 A FY2000 Survey Report NEDO-NP-0004 “Investigation of Feasibility of Wind Power Generation with Storage Batteries” (issued in February 2002)

  However, in the integration method as described in Patent Document 2, errors are also integrated, so that a periodic reset is required. In addition, maintenance is also required when the allowable capacity is reduced due to characteristic deterioration. On the other hand, according to the method as described in Non-Patent Document 1, the problem due to the integration method is avoided, but when the remaining capacity exceeds the threshold value, the correction operation is started / finished. When the increase / decrease is repeated across the threshold value, the correction operation is frequently repeated, and as a result, there remains a problem that a good power fluctuation absorption effect cannot be obtained.

  Therefore, the problem of the present invention is to solve the problem related to the remaining capacity detection method and characteristic deterioration of the secondary battery and the problem related to the optimization control of the remaining capacity, and to ensure the power fluctuation absorption effect by charging and discharging the power storage device. There is to be obtained.

In order to solve such a problem, in the present invention, a power fluctuation absorber comprising a secondary battery and a bidirectional AC / DC converter is connected in parallel with a distributed power source connected to a power system, and the power fluctuation absorption is achieved. In the power stabilization system that stabilizes the power flow of the power system by absorbing the active power fluctuation of the distributed power source by charging and discharging the device,
The power fluctuation absorber is composed of two units, the control device of each power fluctuation absorber is a first computing means for computing a power command for setting the voltage of the secondary battery to a constant value, and the dispersion A second computing means for extracting fluctuation components from the active power output from the power source, the active power fluctuation components being positive active power fluctuation components (generated power exceeding the average generated power) and negative active power fluctuation components (average) A third calculation means that separates the generated power below the generated power),
One of the two power fluctuation absorbing devices adds the positive active power fluctuation component and the power command calculated by setting the set voltage to the lower limit voltage of the secondary battery, The other power fluctuation absorbing device of the two units adds the negative active power fluctuation component and the power command calculated by setting the set voltage to the upper limit voltage of the secondary battery. Then, a charge / discharge operation using the charge / discharge power command is performed.

  According to the present invention, since it is not necessary to detect the remaining capacity of the secondary battery, the problem of errors can be eliminated. In addition, since the two power fluctuation absorbing devices operate in a direction to maintain the upper limit voltage or the lower limit voltage of the secondary battery in a steady state, the power fluctuation absorbing operation is performed within the allowable capacity range of the secondary battery even when the characteristics deteriorate. Can be continued.

FIG. 1 is a block diagram showing an embodiment of the present invention.
As shown in FIG. 1, two sets of independent power fluctuation absorbers 14 and 15 (bidirectional AC / DC converter 6 + secondary battery 7) are connected in parallel with a distributed power source 3 connected to the power system 1. The Each of the power fluctuation absorbers 14 and 15 extracts a fluctuation component from the current command value calculation means 22 for setting the terminal voltage of the secondary battery 7 to a desired value, and the active power output from the distributed power source 3. Obtained by adding the calculation results 23 and the calculation means 23 for separating the active power fluctuation component (the output component exceeding the average power) into the positive power fluctuation component and the negative power fluctuation component (the output component below the average power). A control unit 21 that controls the bidirectional AC / DC converter 6 is provided based on the charge / discharge power command. The calculation means 23 of the generated power fluctuation component of the distributed power source 3 is shown in common in FIG.

The power fluctuation absorber 14 that absorbs only positive power fluctuation components among the power fluctuation components will be described below.
First, the terminal voltage set value 25 of the secondary battery 7 is set to the lower limit voltage of the secondary battery 7. The deviation between the terminal voltage setting value and the terminal voltage detection value is input to the voltage regulator (AVR) 17 to calculate an output power command value for maintaining the secondary battery terminal voltage at the lower limit voltage. Here, the lower limit voltage is not a discharge end voltage generally referred to, but a value that is a lower limit in the secondary battery voltage operation range determined by the specifications (maximum output, expected life, etc.) of the power stabilization system.

  Next, the output voltage and output current of the distributed power source 3 are input to the power detector 11 to detect the generated power of the distributed power source, and the power fluctuation component extraction circuit 19 extracts the generated power fluctuation component. As a calculation method, for example, there is a method of calculating the generated power fluctuation by calculating the average power using a filter having a time constant lower than the frequency component of the absorbed power and calculating the deviation between the average power and the detected power.

  The generated power fluctuation component obtained in this way is input to the polarity determination circuit 20, a positive power fluctuation component (an output component exceeding the average power) is extracted, and the output power obtained by the lower limit voltage control of the secondary battery is extracted therefrom. The command value is added and input to the control unit 21 as an AC power command. The control unit 21 performs control calculation so that the output power detection value detected by the power detector 16 of the power fluctuation absorber 15 follows the AC power command value, and calculates a control signal for the bidirectional AC / DC converter 6. To do.

  At this time, by setting the time constant of the voltage regulator (AVR) 17 so that the output power command value obtained by the upper limit voltage control of the secondary battery responds slower than the generated power fluctuation component to be compensated. The power fluctuation absorbing device 14 gives priority to the compensation operation of the generated power fluctuation amount, and the power fluctuation absorbing device 14 absorbs the positive fluctuation of the generated power generated by the distributed power source 3 while averaging, in the vicinity of the lower limit voltage of the secondary battery 7, that is, low Maintain the remaining capacity state.

Next, the power fluctuation absorber 15 that absorbs only negative power fluctuation components will be described.
First, the terminal voltage set value 25 of the secondary battery 7 is set to the upper limit voltage of the secondary battery 7. The deviation between the terminal voltage setting value and the terminal voltage detection value is input to the voltage regulator (AVR) 17 to calculate an output power command value for maintaining the secondary battery terminal voltage at the upper limit voltage. Here, the upper limit voltage is not a full charge voltage generally referred to, but a value that becomes an upper limit in the secondary battery voltage operation range determined by the specifications (maximum output, expected life, etc.) of the power stabilization system.

  Next, the output voltage and output current of the distributed power source 3 are input to the power detector 11, the generated power of the distributed power source is detected, and the generated power fluctuation component is extracted by the power fluctuation component extraction circuit 19. As a calculation method, for example, there is a method of calculating the generated power fluctuation by calculating the average power using a filter having a time constant lower than the frequency component of the absorbed power and calculating the deviation between the average power and the detected power.

  The generated power fluctuation component obtained in this way is input to the polarity determination circuit 20 to extract a negative power fluctuation component (an output component lower than the average power), and the output power obtained by the lower limit voltage control of the secondary battery is extracted therefrom. The command value is added and input to the control unit 21 as an AC power command. The control unit 21 performs control calculation so that the output power detection value detected by the power detector 16 of the power fluctuation absorber 15 follows the AC power command value, and calculates a control signal for the bidirectional AC / DC converter 6. .

  At this time, by setting the time constant of the voltage regulator (AVR) 17 so that the output power command value obtained by the lower limit voltage control of the secondary battery responds slower than the generated power fluctuation component to be compensated. The power fluctuation absorbing device 15 gives priority to the compensation operation of the generated power fluctuation amount, and on the average, the power fluctuation absorbing device 15 absorbs the negative generated power fluctuation generated by the distributed power source 3 and is, on average, near the upper limit voltage of the secondary battery 7, that is, high Maintain the remaining capacity state.

  By operating the two power fluctuation absorbers 14 and 15 as described above, the secondary battery 7 operates in a remaining capacity state at a substantially constant ratio determined by the battery characteristics with respect to the allowable capacity. Accordingly, it is not necessary to detect the remaining capacity, and even when the characteristics are further deteriorated, it is possible to continue the power fluctuation absorbing operation within the allowable capacity of the secondary battery.

Configuration diagram showing an embodiment of the present invention Block diagram showing a conventional example

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power system, 2 ... Load, 3 ... Distributed power supply, 5 ... Power fluctuation absorber, 6 ... Bidirectional AC / DC converter, 7 ... Secondary battery, 8 ... Current detector (ACCT), 9 ... Current detector (DCCT), 11 ... power detector (for distributed power source), 12 ... secondary battery remaining capacity detector, 13 ... bidirectional AC / DC converter control circuit, 14 ... first power fluctuation absorber, 15 ... second Power fluctuation absorber, 16 ... output power detector, 17 ... automatic voltage regulator (AVR), 19 ... power fluctuation component extraction circuit, 20 ... polarity determination circuit, 21 ... AC-DC converter output control unit, 22 ... secondary Battery voltage control unit, 23 ... distributed power generation power fluctuation calculation unit, 24 ... adder, 25 ... secondary battery terminal voltage setting value (for the first power fluctuation absorber), 26 ... secondary battery terminal voltage setting value (For second power fluctuation absorber), 30... First power fluctuation absorber control circuit, 3 ... second power fluctuation absorber control circuit.

Claims (1)

A power fluctuation absorber comprising a secondary battery and a bidirectional AC / DC converter is connected in parallel with a distributed power source connected to a power system, and the power fluctuation absorber performs charging / discharging, whereby the distributed power source In a power stabilization system that absorbs fluctuations in active power and stabilizes power flow in the power system,
The power fluctuation absorber is composed of two units, the control device of each power fluctuation absorber is a first computing means for computing a power command for setting the voltage of the secondary battery to a constant value, and the dispersion A second computing means for extracting fluctuation components from the active power output from the power source, the active power fluctuation components being positive active power fluctuation components (generated power exceeding the average generated power) and negative active power fluctuation components (average) A third calculation means that separates the generated power below the generated power),
One of the two power fluctuation absorbing devices adds the positive active power fluctuation component and the power command calculated by setting the set voltage to the lower limit voltage of the secondary battery, The other power fluctuation absorbing device of the two units adds the negative active power fluctuation component and the power command calculated by setting the set voltage to the upper limit voltage of the secondary battery. And performing a charge / discharge operation based on a charge / discharge power command.

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