System stabilization device

• US 8,527,106 B2
• Filed: 04/10/2009
• Issued: 09/03/2013
• Est. Priority Date: 04/11/2008
• Status: Expired due to Fees

• Current Assignee: Meidensha Corporation
• Original Assignee: Meidensha Corporation
• Inventors: Muneshima, Masakazu, Oi, Kazunobu, Hirayama, Issei
• Primary Examiner(s): Padmanabhan, Kavita
• Assistant Examiner(s): STEVENS, THOMAS H
• Application Number:
  US12/934,623
• Publication Number:
  US 20110098866A1
• Time in Patent Office: 1,607 Days
• Field of Search: 700/293, 416/132.B, 307 52- 62
• US Class Current: 700/293
• CPC Class Codes: H02J 2300/10 The dispersed energy generation being of fossil origin, e.g. diesel generators
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/28 The renewable source being wind energy wind motors F03D
• CPC Class Codes: H02J 2300/40 wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/48 Controlling the sharing of the in-phase component
• CPC Class Codes: H02J 3/50 Controlling the sharing of the out-of-phase component
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects
• CPC Class Codes: Y02E 70/30 Systems combining energy storage with energy generation of non-fossil origin

Abstract

A control unit of a system stabilization device uses a fluctuation detection block (60) to determine fluctuation components included in the active component and reactive component currents of a system current and fluctuation components included in the frequency signal and the amplitude signal of a system voltage. The high frequency cut-off of the fluctuation detection block (60) is set to be f1; the low frequency cut-off is set to be f2. The fluctuation detection block (60) is composed of a low-pass filter (61) with a time constant of T1, a low-pass filter (62) with a time constant of T2, a subtracter (63) which outputs the difference, between the output signals of the filter (61) and the filter (62), and a feedback circuit (64) which provides feedback on the output of the subtracter (63) to the filters (61, 62). Thus, stability is ensured without using a current detector.

Claims

1. A system stabilization device provided in a distribution system which, when a power system is normal, is connected to the power system, and when an abnormality occurs in the power system, is cut off from the power system, and to which a dispersed generation plant and a load are connected,

the system stabilization device having a control unit, and a power converter which performs a converting action and an inverting action in accordance with a gate signal fed from the control unit,

wherein when the power system is normal, the control unit

determines a first active component of a system current and a first reactive component of the system current, the system current flowing from the power system into the distribution system;

determines a first fluctuation component included in the first active component of the system current by a first fluctuation detection block, and uses the first fluctuation component as a first current command for the first active component;

determines a second fluctuation component included in the first reactive component of the system current by a second fluctuation detection block, and uses the second fluctuation component as a second current command for the first reactive component;

further determines a second active component of an alternating current output current and a second reactive component of the alternating current output current, the alternating current output current being outputted from the power converter; and

outputs the gate signal for reducing a first current deviation, which is a first deviation between the first current command for the first active component and the second active component of the alternating current output current, to zero, and also reducing a second current deviation, which is a second deviation between the second current command for the first reactive component and the second reactive component of the alternating current output current, to zero, and

when the abnormality occurs in the power system, the control unit

determines, from a system voltage of the distribution system, a frequency signal showing a frequency of the system voltage and an amplitude signal showing an amplitude of the system voltage;

determines a third fluctuation component included in the frequency signal by a third fluctuation detection block, and uses the third fluctuation component as a third current command for a third active component;

determines a fourth fluctuation component included in the amplitude signal by a fourth fluctuation detection block, and uses the fourth fluctuation component as a fourth current command for a third reactive component;

further determines the second active component of the alternating current output current and the second reactive component of the alternating current output current, the alternating current output current being outputted from the power converter; and

outputs the gate signal for reducing a third current deviation, which is a third deviation between the third current command for the third active component and the second active component of the alternating current output current, to zero, and also reducing a fourth current deviation, which is a fourth deviation between the fourth current command for the third reactive component and the second reactive component of the alternating current output current, to zero, and

when a first cut-off frequency on a high frequency side of a pass band frequency of a fluctuation detection block is set to be f1, a second cut-off frequency on a low frequency side of the pass band frequency is set to be f2, a first time constant of a first low-pass filter for noise removal which has the first cut-off frequency of f1 is set to be T1, and a second time constant of a second low-pass filter for setting a fluctuation detection time which has the second cut-off frequency of f2 is set to be T2, the first fluctuation detection block, the second fluctuation detection block, the third fluctuation detection block, and the fourth fluctuation detection block are each composed of a first filter having first order lag characteristics with the first time constant of T1, a second filter having first order lag characteristics with the second time constant of T2, a subtracter which performs subtraction between a first signal outputted from the first filter and a second signal outputted from the second filter and outputs a resulting difference, and a feedback circuit for providing the first filter and the second filter with feedback on an output of the subtracter.

2. The system stabilization device according to claim 1, wherein

in each of the first fluctuation detection block, the second fluctuation detection block, the third fluctuation detection block, and the fourth fluctuation detection block,

the first cut-off frequency on the high frequency side of the pass band frequency of the fluctuation detection block is set as f1, the second cut-off frequency on the low frequency side of the pass band frequency is set as f2, the first time constant for noise removal with a value of 1/f1 is set as T1, and the second time constant for setting the fluctuation detection time with a value of 1/f2 is set as T2, and

the first fluctuation detection block, the second fluctuation detection block, the third fluctuation detection block and the fourth fluctuation detection block each perform computations with use of computing programs to

add an input signal inputted to the fluctuation detection block and a feedback signal,

carry out first order lag filtering of a sum of the input signal and the feedback signal, with the time constant as T1, to determine the first filter signal,

carry out first order lag filtering of a sum of the input signal and the feedback signal, with the time constant as T2, to determine the second filter signal, and

subtract the second filter signal from the first filter signal to determine a fluctuation component, output the fluctuation component as the first current command the second current command the third current command, and the fourth current command, and feed back the fluctuation component as the feedback signal.

3. A system stabilization device provided in a distribution system which, when a power system is normal, is connected to the power system, and when an abnormality occurs in the power system, is cut off from the power system, and to which a dispersed generation plant and a load are connected,

the system stabilization device having a control unit, and a power converter which performs a converting action and an inverting action in accordance with a gate signal fed from the control unit,

wherein when the power system is normal, the control unit

determines a first active component of a system current and a first reactive component of the system current, the system current flowing from the power system into the distribution system;

determines a first fluctuation component included in the first active component of the system current by a first fluctuation detection block, and uses the first fluctuation component as a first current command for the first active component;

determines a second fluctuation component included in the first reactive component of the system current by a second fluctuation detection block, and uses the second fluctuation component as a second current command for the first reactive component;

further determines a second active component of an alternating current output current and a second reactive component of the alternating current output current, the alternating current output current being outputted from the power converter; and

outputs the gate signal for reducing a first current deviation, which is a first deviation between the first current command for the first active component and the second active component of the alternating current output current, to zero, and also reducing a second current deviation, which is a second deviation between the second current command for the first reactive component and the second reactive component of the alternating current output current, to zero, and

when the abnormality occurs in the power system, the control unit

determines, from a system voltage of the distribution system, a frequency signal showing a frequency of the system voltage and an amplitude signal showing an amplitude of the system voltage;

determines a third fluctuation component included in the frequency signal by a third fluctuation detection block, and uses the third fluctuation component as a third current command for a third active component;

determines a fourth fluctuation component included in the amplitude signal by a fourth fluctuation detection block, and uses the fourth fluctuation component as a fourth current command for a third reactive component;

further determines the second active component of the alternating current output current and the second reactive component of the alternating current output current, the alternating current output current being outputted from the power converter; and

outputs the gate signal for reducing a third current deviation, which is a third deviation between the third current command for the third active component and the second active component of the alternating current output current, to zero, and also reducing a fourth current deviation, which is a fourth deviation between the fourth current command for the third reactive component and the second reactive component of the alternating current output current, to zero, and

when a first cut-off frequency on a high frequency side of a pass band frequency of a fluctuation detection block is set to be f1, a second cut-off frequency on a low frequency side of the pass band frequency is set to be f2, a first time constant of a first low-pass filter for noise removal which has the first cut-off frequency of f1 is set to be T1, a second time constant of a second low-pass filter for setting a fluctuation detection time which has the second cut-off frequency of f2 is set to be T2, ζ

set as an oscillation coefficient, α

is set as a setting number, G is set as a gain, a value obtained by multiplying T1 by α

is set to be T3, and a value obtained by dividing T2 by α

is set to be T4, the first fluctuation detection block, the second fluctuation detection block, the third fluctuation detection block, and the fourth fluctuation detection block are each composed of a first filter having first order lag characteristics with a time constant of T3, a second filter having first order lag characteristics with a time constant of T4, a subtracter which performs subtraction between a signal outputted from the first filter and a signal outputted from the second filter and outputs a resulting difference, and an amplifier for multiplying an output of the subtracter by the gain G, and outputting a resulting product, and

ζ

expressed by a Formula (01) is set at a value of 1 or higher, and the setting number α and

the gain G are set using the Formula (01), a Formula (02) and a Formula (03);

5. The system stabilization device according to claim 3, wherein

in each of the first fluctuation detection block, the second fluctuation detection block, the third fluctuation detection block, and the fourth fluctuation detection block,

the first cut-off frequency on the high frequency side of the pass band frequency of a fluctuation detection block is set as f1, the second cut-off frequency on the low frequency side of the pass band frequency is set as f2, the first time constant for noise removal with a value of 1/f1 is set as T1, the second time constant for setting the fluctuation detection time with a value of 1/f2 is set as T2, the oscillation coefficient is set as ζ

, the setting number is set as α

, the gain is set as G, the value obtained by multiplying T1 by α

is set as T3, and the value obtained by dividing T2 by α

is set as T4,

the first fluctuation detection block, the second fluctuation detection block, the third fluctuation detection block, and the fourth fluctuation detection block each perform computations with use of computing programs to

carry out first order lag filtering of an input signal inputted to the fluctuation detection block, with the third time constant as T3, to determine a first filter signal,

carry out first order lag filtering of the input signal inputted to the fluctuation detection block, with the fourth time constant as T4, to determine a second filter signal,

subtract the second filter signal from the first filter signal to determine a subtraction signal, and

multiply the subtraction signal by the gain G to determine a fluctuation component, and output the fluctuation component as the first current command, the second current command, the third current command, and the fourth current command.

4. A system stabilization device provided in a distribution system which, when a power system is normal, is connected to the power system, and when an abnormality occurs in the power system, is cut off from the power system, and to which a dispersed generation plant and a load are connected,

the system stabilization device having a control unit, and a power converter which performs a converting action and an inverting action in accordance with a gate signal fed from the control unit,

wherein when the power system is normal, the control unit

determines a first active component of a system current and a first reactive component of the system current, the system current flowing from the power system into the distribution system;

determines a first fluctuation component included in the first active component of the system current by a first fluctuation detection block, and uses the first fluctuation component as a first current command for the first active component;

determines a second fluctuation component included in the first reactive component of the system current by a second fluctuation detection block, and uses the second fluctuation component as a second current command for the first reactive component;

further determines a second active component of an alternating current output current and a second reactive component of the alternating current output current, the alternating current output current being outputted from the power converter; and

outputs the gate signal for reducing a first current deviation, which is a first deviation between the first current command for the first active component and the second active component of the alternating current output current, to zero, and also reducing a second current deviation, which is a second deviation between the second current command for the first reactive component and the second reactive component of the alternating current output current, to zero, and

when the abnormality occurs in the power system, the control unit

determines, from a system voltage of the distribution system, a frequency signal showing a frequency of the system voltage and an amplitude signal showing an amplitude of the system voltage;

determines a third fluctuation component included in the frequency signal by a third fluctuation detection block, and uses the third fluctuation component as a third current command for a third active component;

determines a fourth fluctuation component included in the amplitude signal by a fourth fluctuation detection block, and uses the fourth fluctuation component as a fourth current command for a third reactive component;

further determines the second active component of the alternating current output current and the second reactive component of the alternating current output current, the alternating current output current being outputted from the power converter; and

outputs the gate signal for reducing a third current deviation, which is a third deviation between the third current command for the third active component and the second active component of the alternating current output current, to zero, and also reducing a fourth current deviation, which is a fourth deviation between the fourth current command for the third reactive component and the second reactive component of the alternating current output current, to zero, and

when a first cut-off frequency on a high frequency side of a pass band frequency of a fluctuation detection block is set to be f1, a second cut-off frequency on a low frequency side of the pass band frequency is set to be f2, a first time constant of a first low-pass filter for noise removal which has the first cut-off frequency of f1 is set to be T1, a second time constant of a second low-pass filter for setting a fluctuation detection time which has the second cut-off frequency of f2 is set to be T2, ζ

is set as an oscillation coefficient, α

is set as a setting number, G is set as a gain, a value obtained by multiplying T1 by α

is set to be T3, and a value obtained by dividing T2 by α

a is set to be T4, the first fluctuation detection block, the second fluctuation detection block, the third fluctuation detection block, and the fourth fluctuation detection block are each composed of a first filter having first order lag characteristics with a third time constant of T3, a second filter having first order lag characteristics with a fourth time constant of T4, a subtracter which performs subtraction between a signal outputted from the first filter and a signal outputted from the second filter and outputs a resulting difference, and an amplifier for multiplying an output of the subtracter by the gain G, and outputting a resulting product, and

the gain G is set at an arbitrary value, and the setting number α

is set using a Formula (04);

6. A system stabilization device provided in a distribution system which, when a power system is normal, is connected to the power system, and when an abnormality occurs in the power system, is cut off from the power system, and to which a dispersed generation plant and a load are connected,

the system stabilization device having a control unit, and a power converter which performs a converting action and an inverting action in accordance with a gate signal fed from the control unit,

wherein when the power system is normal, the control unit

determines a first active component of a system current and a first reactive component of the system current, the system current flowing from the power system into the distribution system;

determines a first fluctuation component included in the first active component of the system current by a first fluctuation detection block, and uses the first fluctuation component as a first current command for the first active component;

determines a second fluctuation component included in the first reactive component of the system current by a second fluctuation detection block, and uses the second fluctuation component as a second current command for the first reactive component;

further determines a second active component of an alternating current output current and a second reactive component of the alternating current output current, the alternating current output current being outputted from the power converter; and

outputs the gate signal for reducing a first current deviation, which is a first deviation between the first current command for the first active component and the second active component of the alternating current output current, to zero, and also reducing a second current deviation, which is a second deviation between the second current command for the first reactive component and the second reactive component of the alternating current output current, to zero, and

when the abnormality occurs in the power system, the control unit

determines, from a system voltage of the distribution system, a frequency signal showing a frequency of the system voltage and an amplitude signal showing an amplitude of the system voltage;

determines a third fluctuation component included in the frequency signal by a third fluctuation detection block, and uses the third fluctuation component as a third current command for a third active component;

determines a fourth fluctuation component included in the amplitude signal by a fourth fluctuation detection block, and uses the fourth fluctuation component as a fourth current command for a third reactive component;

further determines the second active component of the alternating current output current and the second reactive component of the alternating current output current, the alternating current output current being outputted from the power converter; and

outputs the gate signal for reducing a third current deviation, which is a third deviation between the third current command for the third active component and the second active component of the alternating current output current, to zero, and also reducing a fourth current deviation, which is a fourth deviation between the fourth current command for the third reactive component and the second reactive component of the alternating current output current, to zero, and

when a first cut-off frequency on a high frequency side of a pass band frequency of a fluctuation detection block, is set to be f1, a first time constant of a low-pass filter for noise removal which has a first cut-off frequency of f1 is set to be T1, ζ

is set as an oscillation coefficient, α

is set as a setting number, G is set as a gain, a value obtained by multiplying T1 by α

is set to be T3, a cushioning time set at an arbitrary time is set to be T5, one sampling period is set to be Ts, and x is set as a limiting value, the first fluctuation detection block, the second fluctuation detection block, the third fluctuation detection block, and the fourth fluctuation detection block each have a filter having first order lag characteristics with a third time constant of T3, a limiter having limiting characteristics defined as ±

(x/T5)Ts, a delay circuit for delaying an inputted signal by one sampling period Ts and outputting a delayed signal, a first subtracter, a second subtracter, an adder, and an amplifier,

the first subtracter performs subtraction between a signal outputted from the filter having the first order lag characteristics and a signal outputted from the delay circuit, and feeds a resulting difference to the limiter,

the adder adds a signal outputted from the limiter and the signal outputted from the delay circuit, and outputs a resulting sum,

the delay circuit delays the signal outputted from the adder by one sampling period Ts, and outputs the delayed signal,

the second subtracter performs subtraction between the signal outputted from the filter having the first order lag characteristics and the signal outputted from the adder, and outputs a resulting difference to the amplifier,

the amplifier multiplies the output of the adder by the gain G, and outputs a resulting product, and

ζ

expressed by a Formula (01) is set at a value of 1 or higher, and the setting number α and

the gain G are set using the Formula (01), a Formula (02) and a Formula (03);

8. The system stabilization device according to claim 6, wherein

in each of the first fluctuation detection block, the second fluctuation detection block, the third fluctuation detection block, and the fourth fluctuation detection block,

the first cut-off frequency on the high frequency side of the pass band frequency of a fluctuation detection block is set as f1, the first time constant for noise removal with a value of 1/f1 is set as T1, the oscillation coefficient is set as ζ

the setting number is set as α

, the gain is set as G, the value obtained by multiplying T1 by α

is set as T3, the cushioning time set at the arbitrary time is set as T5, the one sampling period is set as Ts, and the limiting value is set as x,

the first fluctuation detection block, the second fluctuation detection block, the third fluctuation detection block, and the fourth fluctuation detection block each perform computations with use of computing programs to

carry out first order lag filtering of an input signal inputted to the fluctuation detection block, with a third time constant as T3, to determine a filter signal,

subtract the delayed signal from the filter signal to determine a first subtraction signal,

perform a limiting operation on the first subtraction signal by the limiting characteristics defined as ±

(x/T5)Ts to determine a limit signal,

add the limit signal and the delayed signal to determine an addition signal,

delay the addition signal by the one sampling period Ts to form the delayed signal,

subtract the addition signal from the filter signal to determine a second subtraction signal, and multiply the second subtraction signal by the gain G to obtain a fluctuation component, and output the fluctuation component as the first current command, the second current command, the third current command, and the fourth current command.

7. A system stabilization device provided in a distribution system which, when a power system is normal, is connected to the power system, and when an abnormality occurs in the power system, is cut off from the power system, and to which a dispersed generation plant and a load are connected,

the system stabilization device having a control unit, and a power converter which performs a converting action and an inverting action in accordance with a gate signal fed from the control unit,

wherein when the power system is normal, the control unit

determines a first active component of a system current and a first reactive component of the system current, the system current flowing from the power system into the distribution system;

determines a first fluctuation component included in the first active component of the system current by a first fluctuation detection block, and uses the first fluctuation component as a first current command for the first active component;

determines a second fluctuation component included in the first reactive component of the system current by a second fluctuation detection block, and uses the second fluctuation component as a second current command for the first reactive component;

further determines a second active component of an alternating current output current and a second reactive component of the alternating current output current, the alternating current output current being outputted from the power converter; and

outputs the gate signal for reducing a first current deviation, which is a first deviation, which is a first deviation between the first current command for the first active component and the second active component of the alternating current output current, to zero, and also reducing a second current deviation, which is a deviation between the second current command for the first reactive component and the second reactive component of the alternating current output current, to zero, and

when the abnormality occurs in the power system, the control unit

determines, from a system voltage of the distribution system, a frequency signal showing a frequency of the system voltage and an amplitude signal showing an amplitude of the system voltage;

determines a third fluctuation component included in the frequency signal by a third fluctuation detection block, and uses the third fluctuation component as a third current command for a third active component;

determines a fourth fluctuation component included in the amplitude signal by a fourth fluctuation detection block, and uses the fourth fluctuation component as a fourth current command for a third reactive component;

further determines the second active component of the alternating current output current and the second reactive component of the alternating current output current, the alternating current output current being outputted from the power converter; and

outputs the gate signal for reducing a third current deviation, which is a third deviation between the third current command for the third active component and the second active component of the alternating current output current, to zero, and also reducing a fourth current deviation, which is a fourth deviation between the fourth current command for the third reactive component and the second reactive component of the alternating current output current, to zero, and

when a first cut-off frequency on a high frequency side of a pass band frequency of a fluctuation detection block is set to be f1, a first time constant of a low-pass filter for noise removal which has a first cut-off frequency of f1 is set to be T1, ζ

is set as an oscillation coefficient, α

is set as a setting number, G is set as a gain, a value obtained by multiplying T1 by α

is set to be T3, a cushioning time set at an arbitrary time is set to be T5, one sampling period is set to be Ts, and x is set as a limiting value, the first fluctuation detection block, the second fluctuation detection block, the third fluctuation detection block, and the fourth fluctuation detection block each have a filter having first order lag characteristics with a third time constant of T3, a limiter having limiting characteristics defined as ±

(x/T5)Ts, a delay circuit for delaying an inputted signal by one sampling period Ts and outputting a delayed signal, a first subtracter, a second subtracter, an adder, and an amplifier,

the first subtracter performs subtraction between a signal outputted from the filter having the first order lag characteristics and a signal outputted from the delay circuit, and feeds a resulting difference to the limiter,

the adder adds a signal outputted from the limiter and the signal outputted from the delay circuit, and outputs a resulting sum,

the delay circuit delays the signal outputted from the adder by one sampling period Ts, and outputs the delayed signal,

the second subtracter performs subtraction between the signal outputted from the filler having the first order lag characteristics and the signal outputted from the adder, and outputs a resulting difference to the amplifier,

the amplifier multiplies the output of the adder by the gain G, and outputs a resulting product, and

the gain G is set at an arbitrary value, and the setting number α

is set using a Formula (04);