Harmonic filter facility and setting method of harmonic filter facility

Abstract

To reduce cost of an entire harmonic filter facility and downsize the harmonic filter facility.SOLUTION: A harmonic filter facility suppressing harmonic components included in AC voltage of a bus that is a harmonic suppression target has an LC series circuit composed of a first reactor element connected to the bus and a capacitor element connected to a low pressure side of the first reactor element, and a second reactor element connected to the capacitor element in parallel in the low pressure side of the first reactor element. Anti-resonance orders of the capacitor element and the second reactor element are set to a higher order than a fundamental frequency.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a harmonic filter facility and a method for setting the harmonic filter facility.

Background Art

[0002] Conventionally, there has been a harmonic filter facility for suppressing harmonic components included in the AC voltage of a bus connected to a power supply system. This type of harmonic filter facility includes, for example, as shown in Patent Document 1, a harmonic filter circuit in which a reactor and a capacitor are connected in series, and a shunt reactor connected in parallel with the harmonic filter circuit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the above harmonic filter facility is connected to a power supply system such as large-scale solar power generation or wind power generation, for example, the filter installation bus where the harmonic filter facility is installed may be connected to the power supply system via a cable, or the filter installation bus may be connected to the same bus as the solar power generation or wind power generation connected to the upper commercial power system via a cable. In this case, since the capacitance of the cable is large, the resonance frequency of the power supply system may decrease, and the harmonic components of the filter installation bus may increase.

[0005] To address such problems, in conventional harmonic filter equipment, a shunt reactor for compensating the capacitance of the cable is connected in parallel to the harmonic filter circuit. However, since harmonic filter equipment exhibits capacitive characteristics where the impedance decreases with an increase in frequency in the fundamental wave component, the capacitance of the power system as seen from the connection bus of the harmonic filter equipment further increases. Therefore, an additional shunt reactor is required to compensate for the capacitance of the harmonic filter equipment, increasing the cost of the entire harmonic filter equipment by the number and capacitance of the additional shunt reactor, and also causing the harmonic filter equipment to become larger in size.

[0006] Therefore, the present invention has been made in view of the above problems, and the main object is to reduce the cost of the entire harmonic filter equipment and to miniaturize the harmonic filter equipment.

Means for Solving the Problems

[0007] That is, the harmonic filter equipment according to the present invention is a harmonic filter equipment that suppresses harmonic components included in the AC voltage of a bus to be subjected to harmonic suppression, and includes an LC series circuit composed of a first reactor element connected to the bus and a capacitor element connected to the low-voltage side of the first reactor element, and a second reactor element connected in parallel to the capacitor element on the low-voltage side of the first reactor element, wherein the anti-resonance order of the capacitor element and the second reactor element is set to a higher order than the fundamental frequency.

[0008] In such a harmonic filter facility, since the anti-resonant order of the capacitor element and the second reactor element is set to be higher than the fundamental frequency, the harmonic filter facility exhibits inductive characteristics where the impedance increases with the increase in frequency at the fundamental wave. As a result, an additional parallel reactor for compensating the capacitance of the cable or the capacitance of the harmonic filter facility can be substituted by the second reactor element, eliminating the need to install an additional reactor element. Therefore, the cost of the entire harmonic filter facility can be reduced, and the size of the harmonic filter facility can be minimized.

[0009] Generally, harmonics are integer multiples of the fundamental frequency. So, even if the anti-resonant order is set to be higher than the fundamental frequency, when the anti-resonant order is set to an integer value, there is a possibility that the harmonic components will expand. Therefore, it is preferable that the anti-resonant order is set to a non-integer value. This can suppress the expansion of harmonic components.

[0010] When the anti-resonant order is set to be higher than the fundamental frequency, for example, when the circuit voltage is 22 kV or more and 66 kV or less, the fundamental wave lagging capacitance is 10 Mvar or more and 30 Mvar or less, and the resonant order is 5th, 7th, 11th, or 13th, it is preferable for manufacturing that the capacitance of the capacitor element is 5 μF or more and 200 μF or less, and the inductance of the first reactor element and the inductance of the second reactor element are 0.2 mH or more and 70 mH or less.

[0011] With such a configuration, the above capacitance range and inductance range are the capacitance range and inductance range used in general harmonic filter facilities. Therefore, the anti-resonant order set to be higher than the fundamental frequency can be applied to general harmonic filter facilities.

[0012] As a specific embodiment of the first reactor element, those constituted by a series reactor or a step-down transformer may be mentioned. Here, when the circuit voltage, which is the voltage of the circuit where the harmonic filter facility is provided, is high, the inductance of the second reactor element may exceed the range of inductance allowed in a general harmonic filter facility, and the anti-resonance order may not be selectable. In that case, it is preferable that the first reactor element is constituted by a step-down transformer.

[0013] With such a configuration, by utilizing the leakage reactance of the step-down transformer, even when the circuit voltage is high, the inductance of the second reactor element can be made within the allowable range, so that the anti-resonance order can be selected.

[0014] It is desirable to further include a resistance element connected in parallel with the second reactor element.

[0015] With such a configuration, since a resistance element is connected in parallel with the second reactor element, at the anti-resonance order, the impedance of the second reactor element can be reduced, and the voltage magnification at the anti-resonance order can be mitigated.

[0016] Also, a method for setting a harmonic filter facility is a method for setting a harmonic filter facility including an LC series circuit constituted by a first reactor element connected to the bus bar and a capacitor element connected to the low-voltage side of the first reactor element, and a second reactor element connected in parallel with the capacitor element on the low-voltage side of the first reactor element, characterized in that the anti-resonance orders of the capacitor element and the second reactor element are set to be higher than the fundamental frequency.

[0017] With such a configuration, the same operational effects as those of the above harmonic filter facility can be obtained.

Effects of the Invention

[0018] According to the present invention configured as described above, it is possible to reduce the cost of the entire harmonic filter facility and to miniaturize the harmonic filter facility.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0020] Hereinafter, an embodiment of a harmonic filter facility according to the present invention will be described with reference to the drawings. Note that, for the sake of clarity, any of the following figures may be appropriately omitted or exaggerated and schematically drawn. The same components are denoted by the same reference numerals, and the description thereof will be appropriately omitted.

[0021] <Device Configuration> The harmonic filter facility 100 in the present embodiment suppresses harmonic components included in the AC voltage of the bus bar L that is the object of harmonic suppression. In the present embodiment, the harmonic components are, for example, the 5th harmonic, 7th harmonic, 11th harmonic, or 13th harmonic.

[0022] Specifically, as shown in FIG. 1, the harmonic filter facility 100 includes an LC series circuit 10 composed of a first reactor element 11 connected to the busbar L and a capacitor element 12 connected to the low-voltage side of the first reactor element 11, and a second reactor element 20 connected in parallel with the capacitor element 12 on the low-voltage side of the first reactor element 11.

[0023] The high-voltage side of the first reactor element 11 is electrically connected to the busbar L. In this embodiment, the first reactor element 11 is, for example, a series reactor and has a configuration that does not include a step-down transformer.

[0024] The capacitor element 12 is provided on the low-voltage side of the first reactor element 11 and is connected in series with the first reactor element 11. In this embodiment, the capacitor element 12 is, for example, a film capacitor.

[0025] The second reactor element 20 is electrically connected in parallel with the capacitor element 12. In this embodiment, the second reactor element 20 is, for example, an oil-immersed self-cooled reactor.

[0026] Here, as shown in FIG. 2, the anti-resonance order n1 of the capacitor element 12 and the second reactor element 20 is set to be higher than the fundamental frequency n0. Specifically, the anti-resonance order n1 is set to a non-integer positive value. Also, the anti-resonance order n1 is set to be lower than the resonance order n2 of the first reactor element 11, the second reactor element 20, and the capacitor element 12. As a result, the anti-resonance order n1 is set to be higher than the fundamental frequency n0 and lower than the resonance order n2.

[0027] As a result, the harmonic filter facility 100 exhibits inductance, which is a characteristic that the composite impedance of the harmonic filter facility 100 increases with the increase in frequency at the fundamental frequency n0. Also, the harmonic filter facility 100 exhibits capacitance, which is a characteristic that the composite impedance of the harmonic filter facility 100 decreases with the increase in frequency at a frequency higher than the anti-resonant order n1 and lower than the resonant order n2. Further, at the resonant order n2, the harmonic filter facility 100 suppresses the harmonic components included in the bus L.

[0028] More specifically, the first inductance L1, which is the inductance of the first reactor element 11, the second inductance L2, which is the inductance of the second reactor element 20, and the capacitance C of the capacitor element 12 are calculated as follows using the anti-resonant order n1 and the resonant order n2. Hereinafter, ω is the fundamental angular frequency, V is the circuit voltage of the circuit in which the harmonic filter facility 100 is provided, and Q1 is the lagging capacitance of the harmonic filter facility 100 at the fundamental frequency n0.

[0029] First, the composite impedance Z of the entire harmonic filter facility 100 is represented by Equation (1) below.

[0030]

Equation

[0031] Also, the anti-resonant order n1 and the resonant order n2 are represented by Equation (2) and Equation (3), respectively.

[0032]

Equation

[0033]

Equation

[0034] From Equation (2), the second inductance L2 is represented by Equation (4) below.

[0035]

Number

[0036] By substituting the number 4 into the number 3, the first inductance L1 is represented by the following number 5.

[0037]

Number

[0038] Then, by substituting the numbers 4 and 5 into the number 1, the capacitance C is represented by the following number 6.

[0039]

Number

[0040] By substituting the capacitance C obtained with the number 6 into the numbers 4 and 5, the first inductance L1 and the second inductance L2 are calculated.

[0041] <Example> Hereinafter, the present invention will be described in more detail based on specific examples. However, the following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0042] <Confirmation of Frequency Characteristics and Harmonic Suppression Effect> First, in order to confirm the frequency characteristics and harmonic suppression effect of the harmonic filter facility 100, an analysis was performed using a known circuit simulation tool (Alternative Transient Program, hereinafter referred to as ATP). The analysis conditions were set as follows: the circuit voltage V was 22 kV, the fundamental wave lagging reactive power Q1 was 20 Mvar, the fundamental frequency n0 was 50 Hz, the anti-resonance order n1 was 1.5 times, and the resonance order n2 was 4.9 times. Also, when there is no resistance in the circuit where the harmonic filter facility 100 is installed, the impedance at the anti-resonance order n1 becomes infinite and the impedance at the resonance order n2 becomes 0. Therefore, with the sharpness set to 100, the analysis was performed assuming the existence of the resistance R1 of the LC series circuit 10 and the resistance R2 of the parallel circuit composed of the capacitor element 12 and the second reactor element 20.

[0043] Substituting the parameters of the above analysis conditions into the equations from Equation 4 to Equation 6, the capacitance C is 111 μF, the first inductance L1 is 4.19 mH, and the second inductance L2 is 40.6 mH. Also, from the definition formula of sharpness, the resistance R1 of the LC series circuit 10 is 0.0645 Ω, and the resistance R2 of the parallel circuit is 0.625 Ω.

[0044] When the capacitance C is 111 μF, the first inductance L1 is 4.19 mH, and the second inductance L2 is 40.6 mH, the frequency characteristics of the harmonic filter facility 100 were analyzed using the circuit simulation tool ATP. As a result, the anti-resonance order n1 was 1.5 times and the resonance order n2 was 4.9 times, confirming that they were the set anti-resonance order n1 and resonance order n2.

[0045] Next, the harmonic suppression effect of the harmonic filter facility 100 against the 5th harmonic was confirmed. Here, the system short-circuit capacity behind the filter installation bus was 1000 MVA, and the 5th harmonic voltage behind was 5% with respect to the fundamental wave (22 kV × 5% = 1.1 kV).

[0046] Before the harmonic filter facility 100 is connected to the bus L, in the case of only the 5th harmonic voltage behind, the voltage to ground of the bus L becomes 898 V from the following Equation 7.

[0047]

Number

[0048] In this case, when using the circuit simulation tool ATP, at the fundamental frequency n0, the impedance on the busbar L side is 0.484 Ω, and the impedance of the harmonic filter facility 100 is 24.3 Ω. Also, at the 5th harmonic, the impedance on the busbar L side is 2.41 Ω, and the impedance of the harmonic filter facility 100 is 0.288 Ω.

[0049] Therefore, when the harmonic filter facility 100 has a harmonic suppression effect, when the harmonic filter facility 100 is connected to the busbar L, starting from the following number 8, it is considered that the voltage of the busbar L will become 95.9 V. Thus, when using the circuit simulation tool ATP, it was confirmed that the voltage of the busbar L after the harmonic filter facility 100 was connected to the busbar L was 95.9 V, and it was confirmed that the harmonic filter facility 100 had a suppression effect on the 5th harmonic.

[0050]

Number

[0051] <Selection of the anti-resonance order available for the harmonic filter facility 100> Next, the range of the anti-resonance order n1 available for the harmonic filter facility 100 was selected. Here, in order to determine the inductance range and capacitance range of a general harmonic filter facility 100, the circuit voltage V is set to be 22 kV or more and 66 kV or less, the fundamental wave lagging capacity Q1 is 10 Mvar or more and 30 Mvar or less, and the resonance order n2 is 5th, 7th, 11th, or 13th.

[0052] Under the above preconditions, the condition for the capacitance C of the harmonic filter facility 100 to be maximum is when the circuit voltage V is 22 kV, the fundamental wave lagging reactive power Q1 is 30 Mvar, and the resonance order n2 is 13. Also, the condition for the capacitance C of the harmonic filter facility 100 to be minimum is when the circuit voltage V is 66 kV, the fundamental wave lagging reactive power Q1 is 10 Mvar, and the resonance order n2 is 5. Therefore, the range of the capacitance C of the harmonic filter facility 100 is 5 μF or more and 200 μF or less.

[0053] Also, under the above preconditions, the condition for the first inductance L1 and the second inductance L2 to be maximum is when the circuit voltage V is 66 kV, the fundamental wave lagging reactive power Q1 is 10 Mvar, and the resonance order n2 is 5. Also, the condition for the capacitance C of the harmonic filter facility 100 to be minimum is when the circuit voltage V is 22 kV, the fundamental wave lagging reactive power Q1 is 30 Mvar, and the resonance order n2 is 13. Therefore, the range of the first inductance L1 and the second inductance L2 is 0.2 mH or more and 70 mH or less.

[0054] From the above, in this embodiment, a general harmonic filter facility 100 refers to a facility in which the range of the capacitance C is 5 μF or more and 200 μF or less, and the range of the first inductance L1 and the second inductance L2 is 0.2 mH or more and 70 mH or less. And the range of the anti-resonance order n1 applicable to the general harmonic filter facility 100 is shown in FIG. 3.

[0055] As is clear from FIG. 3, it can be seen that the lower the circuit voltage V and the larger the fundamental wave lagging reactive power Q1, the wider the range in which the anti-resonance order n1 can be selected. Specifically, as shown in FIG. 3(a), when the circuit voltage V is 22 kV and the fundamental wave lagging reactive power Q1 is 30 Mvar, the range of the achievable anti-resonance order n1 at the same resonance order n2 is larger than in the case of other circuit voltages V and fundamental wave lagging reactive powers Q1.

[0056] On the one hand, when the circuit voltage V is 66 kV, the second inductance L2 becomes too large and exceeds 70 mH which is applicable to a general harmonic filter facility 100. As a result, when the first reactor element 11 does not include a step-down transformer described later, the anti-resonance order n1 applicable to the general harmonic filter facility 100 cannot be selected.

[0057] <Effect of this embodiment> According to the harmonic filter facility 100 in this embodiment, since the anti-resonance order n1 of the capacitor element 12 and the second reactor element 20 is set to be higher than the fundamental frequency n0, the harmonic filter facility 100 will exhibit inductiveness at the fundamental frequency n0. As a result, even when the harmonic filter facility 100 is connected to the busbar L via, for example, a cable, the second reactor element 20 can be used to substitute for the capacitance of the cable or an additional parallel reactor for compensating the capacitance of the harmonic filter facility 100, so there is no need to install an additional reactor element. Therefore, the cost of the entire harmonic filter facility 100 can be reduced, and the harmonic filter facility 100 can be miniaturized.

[0058] Also, since the anti-resonance order n1 is set to a non-integer value, the expansion of harmonic components can be suppressed.

[0059] Furthermore, since the anti-resonance order n1 is selected so as to satisfy the condition that the capacitance C is 5 μF or more and 200 μF or less, and the first inductance L1 and the second inductance L2 are 0.2 mH or more and 70 mH or less, the anti-resonance order n1 set to be higher than the fundamental frequency n0 can be used in a general harmonic filter facility.

[0060] <Other embodiments> It should be noted that the present invention is not limited to the above-described embodiment.

[0061] In the above embodiment, when the circuit voltage V is 66 kV, it was not possible to select an anti-resonance order n1 that satisfies the condition that the capacitance C ranges from 5 μF to 200 μF and the ranges of the first inductance L1 and the second inductance L2 are from 0.2 mH to 70 mH. Therefore, the first reactor element 11 may be constituted by a step-down transformer 11T. Specifically, as shown in FIG. 4, an example is the case where the first reactor element 11 is a step-down transformer 11T. The step-down transformer 11T shown in FIG. 4 is, for example, a single-winding transformer, and when the primary-side voltage is, for example, 66 kV, it steps down the secondary-side voltage to, for example, 22 kV, but is not limited thereto.

[0062] Consider selecting an anti-resonance order n1 applicable to a general harmonic filter facility 100 using the step-down transformer 11T shown in FIG. 4. Note that the capacity of the step-down transformer 11T is 20 Mvar, and the leakage reactance is 5 - 15%. In this case, the secondary-side leakage inductance of the step-down transformer is 3.9 - 11.6 mH.

[0063] Here, when the anti-resonance order n1 is 1.5 and the resonance order n2 is 4.9, calculating based on Equation 4 - Equation 6, the capacitance C is 12.4 μF, the first inductance L1 is 37.6 mH, and the second inductance L2 is 363 mH. When converted to the secondary side, the capacitance C is 112 μF, the first inductance L1 is 4.2 mH, and the second inductance L2 is 40.3 mH. Therefore, since all of the capacitance C, the first inductance L1, and the second inductance L2 are within the range of a general harmonic filter facility 100, it is possible to select the anti-resonance order n1 even when the circuit voltage V is high by utilizing the leakage inductance of the step-down transformer 11T.

[0064] In FIG. 4, the first reactor element 11 was constituted only by the step-down transformer 11T, but as shown in FIG. 5, the first reactor element 11 may be constituted by the step-down transformer 11T and the series reactor 11L.

[0065] Also, as shown in FIG. 6, the harmonic filter facility 100 may further include a resistance element 30 connected in parallel to the second reactor element 20. In FIG. 6, the resistance element 30 is, for example, a resistor, but the resistance element 30 may be a combination of any of a reactor, a resistor, or a capacitor. Thereby, at the anti-resonance order n1, the impedance of the second reactor element 20 can be decreased, and the voltage magnification at the anti-resonance order n1 can be alleviated.

[0066] Needless to say, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit thereof.

Description of Reference Numerals

[0067] 100 ··· Harmonic filter facility 10 ··· LC series circuit 11 ··· First reactor element 11T ··· Step-down transformer 12 ··· Capacitor element 20 ··· Second reactor element 30 ··· Resistance element L ··· Bus bar

Claims

1. A harmonic filter facility for suppressing harmonic components included in the AC voltage of a bus to be subjected to harmonic suppression, comprising: an LC series circuit constituted by a first reactor element connected to the bus and a capacitor element connected to the low-voltage side of the first reactor element; a second reactor element connected in parallel with the capacitor element on the low-voltage side of the first reactor element; A harmonic filter facility, wherein the anti-resonance order of the capacitor element and the second reactor element is set to a higher order than the fundamental frequency.

2. The harmonic filter facility according to claim 1, wherein the anti-resonance order is set to a non-integer value.

3. When the anti-resonance order is set to a higher order than the fundamental frequency, if the circuit voltage is 22 kV or more and 66 kV or less, the fundamental wave lagging capacity is 10 Mvar or more and 30 Mvar or less, and the resonance order is 5th, 7th, 11th, or 13th, the capacitance of the capacitor element is 5 μF or more and 200 μF or less, and the inductance of the first reactor element and the inductance of the second reactor element are 0.2 mH or more and 70 mH or less. The harmonic filter facility according to claim 1.

4. The harmonic filter facility according to claim 1, wherein the first reactor element is constituted by a series reactor or a step-down transformer.

5. The harmonic filter facility according to any one of claims 1 to 4, further comprising a resistance element connected in parallel with the second reactor element.

6. A method for setting a harmonic filter facility, comprising: an LC series circuit constituted by a first reactor element connected to a bus and a capacitor element connected to the low-voltage side of the first reactor element; and a second reactor element connected in parallel with the capacitor element on the low-voltage side of the first reactor element, wherein the anti-resonance order of the capacitor element and the second reactor element is set to a higher order than the fundamental frequency.

Images