JP2003235164A - Method and apparatus for controlling received power - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for controlling received power wherein, when received power is controlled, the influences of harmonic currents produced due to local loads on a power supply system are taken into account according to the state of the operation of a power receiving system, and thereby received power is controlled to the necessary and sufficient degree to prevent the malfunctions of power relays. <P>SOLUTION: The power control method is for the received power of a system wherein non-utility generators 4 (G1, G2) operate in parallel with a power supply system 1. In the method, the power flow Pwc at a receiving point A is controlled according to the magnitude of harmonic currents Jhc at the receiving point A. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system in which a private generator is operated in parallel with another power source such as a grid.

[0002]

2. Description of the Related Art In a factory facility having a private generator 4 (G1, G2 ...) That operates in parallel with a system 1 according to the prior art, the purpose is to prevent the generator 4 from operating independently.
A reverse power relay and an insufficient power relay are installed at the power receiving point A. In operation, a method of controlling the power generation output of the power generator 4 so that the power flow Pwc at the power receiving point A has a constant value is adopted.

In FIG. 3, a power control system in which a generator 4 (G1, G2 ...) Is operating in parallel with a grid 1 is connected from a grid 1 to a power receiving point A via a circuit breaker 1A and a current transformer CT. The power line bus bar 1B shown by a horizontal line is connected to the power receiving point A, and the power line bus bar 1B is connected to the load 6 (61,62 ...) And the generator 4 (G1, G2 ... ) Are connected via circuit breakers 711, 712, ..., 721, 722 ,.

In addition, the power flow Pw from the grid 1 at the receiving point A
In c, the received power converter 21 detects the current and voltage detected by the current transformer CT and the voltage transformer PT. The power flow (Pwc) PV detected by the received power converter 21 is compared with a target value SV0 preset by the received power setting device 22, and the control output MV (MV1, MV2 ・) of the received power control device 23. Generator 4 (G1, G2
・ ・) Governor (GOV1, GOV2 ・ ・) is controlled to load 6
(61,62 ...) Most of the electric power required by the generator 4 (G1, G2
・ ・), The remaining load power (power flow Pwc) is received from the grid 1, and the received power (Pwc) PV is controlled to reach the target value SV0 set by the received power setter 22. .
As a result, the power supply from the on-site generators 4 (G1, G2 ...) to the grid 1 is prevented, and the received power (power flow) (Pwc) PV is controlled so that the contracted power is not exceeded. Is done.

Normally, control is performed so that the power flow Pwc from the grid 1 to the factory is controlled so that the power relays such as the reverse power relay and the insufficient power relay described above do not operate.
Harmonic current (Jh1, Jh2 ...) at the factory load 6 (61,62 ...)
If there is a load that causes the occurrence of harmonics, the harmonic current Jhc is added to the power receiving point A, and as a result, there is a problem that "the current waveform is distorted and the power relay malfunctions." Therefore, in order to prevent the malfunction of this power relay, the target value SV0 of the received power setting device 22 is set to a level at which this power relay does not operate.

[0006]

In the power control method for the received power according to the prior art, the power setting value of the received power is determined in consideration of the maximum harmonic generation amount of the premises load.
Regardless of the change in harmonic generation load or the operating condition of the generator,
It was set up to receive power flow levels that were higher than necessary, and it was uneconomical to receive power purchased more than necessary from the grid.

The present invention has been made in view of the above points, and an object thereof is to solve the above-mentioned problems and to determine the influence of the harmonic current generated by the premises load on the system side according to the operating condition. It is an object of the present invention to provide a power control method for received power, which is capable of performing necessary and sufficient received power control to prevent malfunction of a power relay by performing expected received power control, and a received power control device thereof.

[0008]

According to the present invention, there is provided a power control method for received power of a system in which a private generator is operated in parallel with a grid, wherein the power flow at the power receiving point is controlled by the power receiving point. Shall be controlled according to the magnitude of the harmonic current. By such a method, by controlling the power flow in consideration of the effect of the harmonic current generated by the premises load on the system side, the necessary and sufficient received power control can be performed according to the operating conditions, and the power relay malfunctions. The operation can be prevented.

Further, the magnitude of the harmonic current at the power receiving point is determined in advance from the power system constant as seen from the power receiving point on the system side, the constant of the generator, and the amount of the harmonic current generated by the premises load. Based on the constants, the magnitude of the harmonic current at the power receiving point can be calculated according to the operating conditions of the generator and the premises load, and the target value of the received power of the received power control device can be corrected and controlled.

According to this method, the target value of the received power of the received power control device is a system in which the total amount of harmonic current generated by the load in operation, which is obtained in advance, is the system viewed from the power receiving point which is obtained in advance. The harmonic current that is shunted to the grid side is obtained from the impedance and the internal impedance of the generator that is operating inside the building, and the target value is corrected by multiplying this harmonic current by a predetermined correction factor. be able to.

The corrected target value of the received power is used to predict the harmonic current shunted to the system side according to the amount of harmonic current generated in the premises load and the operating condition of the generator in operation. Since the received power control device controls the generated power of the generator that is in operation, and controls the power flow at the power receiving point with this corrected target value of received power Economic operation can be achieved without receiving electricity.

Further, the received power control apparatus using the above-described received power control method includes target value correction means for calculating the magnitude of the harmonic current at the received power point, and this target value correction means is the received power point. From the system side, the internal impedance of the generator, the predicted amount of harmonic current generated by each load in the premises, and the memory means that stores the data in advance, and the operating status of each load in the premises. On the premises, the input means that receives the digital input that shows and the digital input that shows the operating status of the generator, and the digital input that shows the predicted amount of harmonic current generated for each load and the operation information of the premises load An addition arithmetic circuit that predicts the total harmonic current that occurs,
A parallel arithmetic circuit that calculates the internal impedance of the generator from the internal impedance of the generator and the digital input that indicates the operating status of the generator, and the total harmonic current that is generated by the internal load of the generator that is operating from this parallel arithmetic circuit and the system impedance. A shunt current calculating circuit for shunting to the system side, and a target value correction circuit for correcting the target value of the received power of the received power control device by multiplying the shunt current calculated by this shunt current calculating circuit by a correction factor, It can be configured.

[0013]

1 is a block diagram of a system for explaining a power control method for received power and an apparatus for controlling the received power according to an embodiment of the present invention, and FIG. 2 is a block diagram of a target value correction means according to the embodiment. The same members corresponding to those in FIG. 3 are designated by the same reference numerals. In FIG. 1, according to the present invention, there is provided a power control method for received power (power flow) Pwc of a system in which a generator 4 (G1, G2 ...) Is operating in parallel with a grid 1, The power flow Pwc can be controlled according to the magnitude of the harmonic current Jhc at the power receiving point A.

According to this control method, the indoor load 6 (61, 62
・ ・) By controlling the power flow Pwc in anticipation of the influence of the harmonic currents (Jh1, Jh2 ・) generated on the system 1 side, the load 6 (61, 62 ・ ・) in operation and The received power Pwc that is necessary and sufficient according to the operating status of the generator 4 (G1, G2 ...) Can be controlled to prevent malfunction of the power relay and achieve economical operation.

[0015]

(Embodiment 1) In FIG. 1, a power control method for received power Pwc and a received power control apparatus therefor according to the present invention show a value of a harmonic current Jhc passing through a power receiving point A and a value of a harmonic current Jhc. Generated load 6 (61,62 ...) And generator 4 (G1,
G2 ...) Prediction calculation from the operating state of the
The set value SV of the power flow control of the received power Pwc is automatically changed according to Jhs.

This system configuration is based on the system 1 circuit breaker 1A
Also, power is supplied to the power receiving point A via the current transformer CT. A power line bus bar 1B is provided at this power receiving point A, and loads 6 (61,62 ...) Are respectively passed through the circuit breakers 711,712 ,.
Further, the generator 4 (G1, G2 ...) Is connected to the power line bus bar 1B via the circuit breakers 721, 722 ,. The received power Pwc at the power receiving point A is the power flow Pwc at the power receiving point detected by the power receiving power converter 1 based on the detected amounts of the current transformer CT and the voltage transformer PT, and the power receiving power control device 23 controls the control signal MV (MV1, MV2
・) Is output and the two generators G1 and G2 are shown in the illustrated example, but the governors GOV1 and GOV2 of the generators G1 and G2 are controlled. The set value SV of the received power control device 23 is controlled by using the value (SV) calculated by the target value correction means 5.

Further, the magnitude of the harmonic current Jhc at the power receiving point A is determined by the system constant (system impedance Zs) as seen from the power receiving point A on the system 1 side and the constants of the generator 4 (G1, G2 ...) (Internal Impedance Zg1, Zg2, ...) and each premises load 6 (61,62.
・) Observing and measuring the amount of harmonic current (Jh1, Jh2 ···) and the constant data (for example, stored in the data storage part (831,821,822 ···, 811,812 ···) of the memory 8) Based on the generator 4 (G1, G2 ...) and the premises load 6 (6
1,62 ・ ・) (Specifically, circuit breakers 721,722, ・
., 711, 712, ... Operating states of auxiliary relays Ay21, Ay22
・, Ay11, Ay12 ・ ・ Contact signals d21, d22, ・ ・, d11, d12 ・
・) The target value of the received power Pwc of the received power controller 23 is calculated by predicting the magnitude (Jhc) of the harmonic current at the receiving point A
SV (= SV0 + αJhs) can be corrected and controlled.

According to this method, the target value SV of the received power Pwc of the received power control device 23 is the harmonic current (Jh1, Jh2 ...) Due to the load 6 (61,62 ..
・) The total amount of generated Jh (= ΣJhi) of the system impedance Zs as seen from the power receiving point A seen from the power receiving point A in advance and the power generator 4 (G1, G2 ・ ・) on the inside of the building The internal impedance (Zg1, Zg2, ··) and the harmonic current Jhs shunting to the system 1 side are calculated from this, and this harmonic current Jhs is multiplied by a predetermined correction factor α to obtain the target of the above received power Pwc. Value SV
Can be corrected.

The target value SV of this corrected received power Pwc
Is a generator 4 that is still in operation, depending on the amount of harmonic currents (Jh1, Jh2 ...) that are operating in the premises load 6 (61, 62 ...).
The harmonic current Jhs shunting to the system 1 side can be predicted according to the operating status of (G1, G2 ...), so the received power control device 23 is operating the generator 4 (G1, G2 ... ) Is controlled and the power flow Pwc at the power receiving point A is controlled by the corrected target value SV of the received power, so that it is economical without receiving the extra received power (purchased power) Pwc. Can be operated.

Next, the harmonic currents (Jh1, Jh2 ...) Due to the operating load 6 (61,62 ...) Pass through the receiving point A to the grid 1
The current Jhc (Jhs) flowing to the side is obtained by an approximate calculation formula. Harmonic current (Jh1, Jh2
・) Total current of ΣJhi, generator 4 (G1, G2
・ ・) If the internal impedance is Zg and the system impedance on the system 1 side is Zs, the current Jhs flowing to the system 1 side via the power receiving point A can be obtained by equation (1).
That is,

[0021]

[Equation 1] On the other hand, harmonic current Jhc generated in relays such as power relays
It is generally considered that the operating error due to is proportional to the magnitude of the harmonic current Jhc, so if the power set value SV of the received power Pwc is changed according to the harmonic current Jhc, which is the cause of this error, The current waveform passing point A is the harmonic current Jh
Even if it is distorted by c, the power relay will not malfunction. Internal impedance (Zg1, Z2) of generator 4 (G1, G2 ...)
g2, ・ ・) is fixed for each individual generator even though there is a difference due to capacity, so the circuit breaker on the generator 4 (G1, G2 ・ ・) side
721,722, ···········································································································
・) The total current of the harmonic current (Jh1, Jh2 ・ ・) depends on the operating load 6 depending on the switching conditions of the load circuit breakers 711, 712, ・ ・.
(61,62 ・ ・) total harmonic current (Jh1, Jh2 ・ ・) ΣJh
By calculating i, it is possible to calculate easily. To be exact, the current Jhs flowing to the system 1 side of equation (1) may be divided into the operating load 6 (61,62 ・ ・), but generally the load 6 (61,62 ・ ・) The impedance of the generator 4 (G1,
Since it has a sufficiently large value with respect to the internal impedance Zg (Zg1, Zg2, ..) of G2 ..) and the system impedance Zs, sufficient accuracy can be obtained by the simple calculation of equation (1). (Embodiment 2) Next, as described above, the received power control apparatus 23 according to one embodiment of the present invention controls the harmonic current Jh at the power receiving point A.
It is configured to include target value correction means for predicting and calculating the magnitude of c. In FIG. 2, the target value correction means 5 includes a system impedance Zs when the system side 1 is viewed from the power receiving point A, and internal impedances (Zg1, Zg2 ...) of the generator 4 (G1, G2 ...).
・) And the predicted generation amount of harmonic current (Jh1, Jh2 ・ ・) for each load 6 (61,62 ・ ・) in the premises, and the data of each memory area 831, memory area 821,822, ..., Memory Area 811, 812,
.. and memory means 8 to be stored in advance in each load 6 (6
1,62 ...) Digital input (d11, d12.
・) And the digital input (d21, d22 ・ ・) which shows the operation status of the generator 4 (G1, G2 ・ ・), and the input means 9 for receiving the load and each load 6 (61,62 ・ ・) Predicted harmonic current generation
(Jh1, Jh2 ・ ・) and digital input (d11, d12 ・ ・) showing the operation information of the load 6 (61,62 ・ ・) on the premises Additive calculation to predict the total harmonic current Jh = ΣJhi generated in the premises Circuit 52 (Add
1) and the internal impedance of the generator 4 (G1, G2 ...) (Zg
1, Zg2 ・ ・) and a digital input (d21, d2
2 ・ ・) and the parallel internal operation circuit 53 (Add2) that calculates the operating internal impedance Zg of the generator side G (G1, G2 ・ ・), and the combined internal impedance Zg of this parallel operational circuit 53 (Add2) and the system impedance A shunt current Jhs that divides the total harmonic current ΣJhi generated in the operating premises load from Zs to the system 1 side
And the target value SV of the received power setting device 22 of the received power control device 23 by multiplying the divided current Jhs calculated by this divided current calculation circuit 51 by the correction factor α (54).
And a target value correction circuit (55, 56) that corrects 0.

The target value correction circuit (55, 56) is an adder 56.
The same calculation can be performed even if the arrangement position of the multiplier 55 is reversed. The load impedance of the load 6 (61,62 ...) Is the internal impedance (Z of the generator side G (G1, G2 ...)).
g1, Zg2 ···), but the load impedance of the specific load 6x is considered to be necessary when the influence of Zx is a concern.
・) The load impedance Zx of this specific load 6x is also assumed to be connected in parallel to the specific load 6x under the conditions of operating information d1x in addition to the content of calculating the parallel operation circuit 53 (Add2) that calculates the operating internal impedance Zg Just calculate.

[0023]

According to the present invention, it is necessary and sufficient to perform the received power control by anticipating the influence of the harmonic current generated by the premises load on the system side according to the operating condition of the received power system. It is possible to provide a power control method for received power and a received power control device for controlling received power, which can prevent malfunction of a power relay.

[Brief description of drawings]

FIG. 1 is a system configuration diagram illustrating a power control method of received power and a received power control device thereof according to an embodiment of the present invention.

FIG. 2 is a block diagram of target value correction means according to one embodiment.

FIG. 3 is a system configuration diagram illustrating a power control method for received power and a received power control device according to a conventional technique.

[Explanation of symbols]

1 system 1A, 7,711,712,721,722 Circuit breaker 1B power line bus bar 21, W / V incoming power converter 22 Received power setting device 23, APC power reception control device 4, G1, G2 generator 5 Target value correction means 51 Shunt current calculation circuit 52 Addition arithmetic circuit 53 Parallel arithmetic circuit 54, α correction count 55,56 Target value correction circuit 6,61,62 load 8,811,812,821,822,831 memory section 9, d11, d12, d21, d22 Digital input means A power receiving point Ay11, AY12, AY21, AY22 Auxiliary relay CT current transformer PT voltage transformer Jh, Jh1, Jh2 Harmonic current Jhs, Jhc Harmonic current at power receiving point Pwc power flow SV, SV0 Received power set value Zg, Zg1, Zg2 Internal impedance Zs system impedance GOV1, GOV2 governor

Claims (3)

[Claims] 1. A private power generator (hereinafter abbreviated as a power generator)
Is a power control method for the received power of a system operating in parallel with the grid, which controls the power flow at the receiving point according to the magnitude of the harmonic current at the receiving point. Power control method. 2. The power control method for received power according to claim 1, wherein the magnitude of the harmonic current at the power receiving point is a system constant when the power system is viewed from the power receiving point, a generator constant, and a premises The amount of harmonic current generated by the load is calculated in advance, and based on these constants, the magnitude of the harmonic current at the power receiving point is calculated according to the operating conditions of the generator and local load, and the power received by the power receiving power control device is calculated. A power control method for received power, characterized in that the target value of power is corrected and controlled. 3. A received power control apparatus using the received power control method according to claim 1 or 2, further comprising target value correction means for calculating the magnitude of the harmonic current at the power receiving point. The target value correcting means is a system impedance when the system side is viewed from the power receiving point, each internal impedance of the generator, a predicted generation amount of a harmonic current due to each load in the premises, and a memory means that stores data in advance, Input means for receiving a digital input indicating the operating status of each load on the premises and a digital input indicating the operating status of the generator, the predicted harmonic current generation amount for each load, and operating information of the premises load Of the internal impedance of the generator side from the addition arithmetic circuit that predicts the total harmonic current generated in the premises from the digital input that indicates the internal impedance of the generator and the digital input that indicates the operating status. The parallel operation circuit for calculating the current, the shunt current operation circuit for shunting all the harmonic currents generated in the operating premises load to the system side from the parallel operation circuit and the system impedance, and the shunt current operation circuit A target value correction circuit that multiplies the shunt current by a correction factor to correct the target value of the received power of the received power control device.