SYSTEM STABILIZATION DEVICE

• US 20110098866A1
• Filed: 04/10/2009
• Published: 04/28/2011
• Est. Priority Date: 04/11/2008
• Status: Active Grant

• Current Assignee: Meidensha Corporation
• Original Assignee: Meidensha Corporation
• Inventors: Hirayama, Issei, Muneshima, Masakazu, Oi, Kazunobu
• Granted Patent: US 8,527,106 B2
• Time in Patent Office: Days
• 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 cut-off frequency on the high frequency side of the fluctuation detection block (60) is set to be f1; the cut-off frequency on the low frequency side is set to be f2; the time constant of the low-pass filter for noise removal which has a cut-off frequency of f1 is set to be T1; and the time constant of the low-pass filter for setting a fluctuation detection time which has a cut-off frequency of f2 is set to be T2. The fluctuation detection block (60) is composed of a low-pass filter (61) having first order lag characteristics with a time constant of T1, a low-pass filter (62) having first order lag characteristics with a time constant of T2, a subtracter (63) which performs subtraction between the output signals of the filter (61) and the filter (62) and outputs the difference, and a feedback circuit (64) which provides feedback on the output of the subtracter (63) to the filters (61, 62). Thus, stable actions are ensured without using a current detector or the like.

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

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

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

further determines an active component of an alternating current output current and a 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 current deviation for the active component, which is a deviation between the current command for the active component and the active component of the alternating current output current, to zero, and also reducing a current deviation for the reactive component, which is a deviation between the current command for the reactive component and the 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 fluctuation component included in the frequency signal by a third fluctuation detection block, and uses the fluctuation component as a current command for an active component;

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

further determines the active component of the alternating current output current and the 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 current deviation for the active component, which is a deviation between the current command for the active component and the active component of the alternating current output current, to zero, and also reducing a current deviation for the reactive component, which is a deviation between the current command for the reactive component and the reactive component of the alternating current output current, to zero, and

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

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

in each of the first to fourth fluctuation detection blocks,

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

the first to fourth fluctuation detection blocks 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 a time constant as T1, to determine a first filter signal,

carry out first order lag filtering of a sum of the input signal and the feedback signal, with a time constant as T2, to determine a 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 current commands, 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 an active component of a system current and a reactive component of the system current, the system current flowing from the power system into the distribution system;

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

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

further determines an active component of an alternating current output current and a 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 current deviation for the active component, which is a deviation between the current command for the active component and the active component of the alternating current output current, to zero, and also reducing a current deviation for the reactive component, which is a deviation between the current command for the reactive component and the 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 fluctuation component included in the frequency signal by a third fluctuation detection block, and uses the fluctuation component as a current command for an active component;

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

further determines the active component of the alternating current output current and the 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 current deviation for the active component, which is a deviation between the current command for the active component and the active component of the alternating current output current, to zero, and also reducing a current deviation for the reactive component, which is a deviation between the current command for the reactive component and the reactive component of the alternating current output current, to zero, and

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

is set to be T4, the first to fourth fluctuation detection blocks 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 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), Formula (02) and Formula (03);

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

in each of the first to fourth fluctuation detection blocks,

the cut-off frequency on the high frequency side of the pass band frequency of the fluctuation detection block is set as f1, the cut-off frequency on the low frequency side of the pass band frequency is set as f2, the time constant for noise removal with a value of 1/f1 is set as T1, the 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 to fourth fluctuation detection blocks each perform computations with use of computing programs to

carry out first order lag filtering of the input signal inputted to the fluctuation detection block, with a 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 a 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 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 an active component of a system current and a reactive component of the system current, the system current flowing from the power system into the distribution system;

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

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

further determines an active component of an alternating current output current and a 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 current deviation for the active component, which is a deviation between the current command for the active component and the active component of the alternating current output current, to zero, and also reducing a current deviation for the reactive component, which is a deviation between the current command for the reactive component and the 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 fluctuation component included in the frequency signal by a third fluctuation detection block, and uses the fluctuation component as a current command for an active component;

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

further determines the active component of the alternating current output current and the 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 current deviation for the active component, which is a deviation between the current command for the active component and the active component of the alternating current output current, to zero, and also reducing a current deviation for the reactive component, which is a deviation between the current command for the reactive component and the reactive component of the alternating current output current, to zero, and when a cut-off frequency on a high frequency side of a pass band frequency of the fluctuation detection block is set to be f1, a cut-off frequency on a low frequency side of the pass band frequency is set to be f2, a time constant of a low-pass filter for noise removal which has a cut-off frequency of f1 is set to be T1, a time constant of a low-pass filter for setting a fluctuation detection time which has a 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

is set to be T4, the first to fourth fluctuation detection blocks 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

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

is set using 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 an active component of a system current and a reactive component of the system current, the system current flowing from the power system into the distribution system;

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

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

further determines an active component of an alternating current output current and a 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 current deviation for the active component, which is a deviation between the current command for the active component and the active component of the alternating current output current, to zero, and also reducing a current deviation for the reactive component, which is a deviation between the current command for the reactive component and the 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 fluctuation component included in the frequency signal by a third fluctuation detection block, and uses the fluctuation component as a current command for an active component;

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

further determines the active component of the alternating current output current and the 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 current deviation for the active component, which is a deviation between the current command for the active component and the active component of the alternating current output current, to zero, and also reducing a current deviation for the reactive component, which is a deviation between the current command for the reactive component and the reactive component of the alternating current output current, to zero, and when a cut-off frequency on a high frequency side of a pass band frequency of the fluctuation detection block is set to be f1, a time constant of a low-pass filter for noise removal which has a cut-off frequency of f1 is set to be T1, 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, 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 to fourth fluctuation detection blocks each have a filter having first order lag characteristics with a 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 the 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 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), Formula (02) and Formula (03);

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

in each of the first to fourth fluctuation detection blocks,

the cut-off frequency on the high frequency side of the pass band frequency of the fluctuation detection block is set as f1, the 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 to fourth fluctuation detection blocks each perform computations with use of computing programs to

carry out first order lag filtering of the input signal inputted to the fluctuation detection block, with a 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 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 an active component of a system current and a reactive component of the system current, the system current flowing from the power system into the distribution system;

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

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

further determines an active component of an alternating current output current and a 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 current deviation for the active component, which is a deviation between the current command for the active component and the active component of the alternating current output current, to zero, and also reducing a current deviation for the reactive component, which is a deviation between the current command for the reactive component and the 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 fluctuation component included in the frequency signal by a third fluctuation detection block, and uses the fluctuation component as a current command for an active component;

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

further determines the active component of the alternating current output current and the 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 current deviation for the active component, which is a deviation between the current command for the active component and the active component of the alternating current output current, to zero, and also reducing a current deviation for the reactive component, which is a deviation between the current command for the reactive component and the reactive component of the alternating current output current, to zero, and when a cut-off frequency on a high frequency side of a pass band frequency of the fluctuation detection block is set to be f1, a time constant of a low-pass filter for noise removal which has a 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 to fourth fluctuation detection blocks each have a filter having first order lag characteristics with a 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 the 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

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

is set using Formula (04);