Harmonic filter equipment and setting method of harmonic filter equipment

Abstract

To reduce cost and a size of harmonic filter equipment and to avoid a current zero error event when harmonic filter equipment is turned on or when a short circuit accident occurs on a power system side.SOLUTION: Harmonic filter equipment which suppresses harmonic components contained in AC voltage of a bus being a harmonic suppression target includes: a first capacitor element connected to the bus; a first reactor element connected in parallel to the first capacitor element; a resistance element connected in series to the first capacitor element and the first reactor element; and a fundamental wave resonance circuit which is connected in parallel to the resistance element and is configured of a second capacitor element and a second reactor element. The anti-resonance order of the first capacitor element and the first reactor element is set to a higher order than a fundamental wave order.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a harmonic filter installation and a method for setting up a harmonic filter installation. [Background technology]

[0002] Conventionally, there has been harmonic filter equipment that suppresses harmonic components contained in the AC voltage of a bus connected to a power supply system. For example, as shown in Patent Document 1, this type of harmonic filter equipment includes a harmonic filter circuit in which a reactor and a capacitor are connected in series, and a parallel reactor connected in parallel to the harmonic filter circuit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 1985-96137 Summary of the Invention [Problem to be solved by the invention]

[0004] When the harmonic filter equipment is connected to a power supply system, such as a large-scale solar or wind power generation system, the filter installation bus on which the harmonic filter equipment 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 or wind power generation system, which is connected to a higher-level commercial power system via a cable. In this case, the capacitance of the cable is large, which may reduce the resonance order of the power supply system and increase the harmonic components of the filter installation bus.

[0005] To address this issue, conventional harmonic filter systems have parallel reactors connected to the harmonic filter circuit to compensate for the cable capacitance. However, harmonic filter systems exhibit capacitive properties in that the impedance of the fundamental component decreases as the frequency increases, further increasing the capacitance of the power system as seen from the busbar to which the harmonic filter system is connected. This requires additional parallel reactors to compensate for the capacitance of the harmonic filter system, which increases the cost of the entire harmonic filter system by the number and capacity of the additional parallel reactors, and also increases the size of the harmonic filter system.

[0006] Furthermore, when the parallel reactor is turned on or if a short circuit or other accident occurs on the power grid side, a direct current is generated from the parallel reactor. In this case, the current flowing through the circuit breaker does not become zero, and an event occurs in which the circuit breaker continues to be unable to interrupt (hereinafter referred to as a zero current error event).

[0007] Therefore, the present invention has been made in consideration of the above problems, and its main objective is to reduce the cost and size of harmonic filter equipment, and to avoid a zero current error when a parallel reactor is connected or when a short circuit occurs on the power grid side. [Means for solving the problem]

[0008] That is, the harmonic filter equipment of the present invention is a harmonic filter equipment that suppresses harmonic components contained in the AC voltage of a bus that is the target for harmonic suppression, and is characterized in that it comprises a first capacitor element connected to the bus, a first reactor element connected in parallel with the first capacitor element, a resistance element connected in series with the first capacitor element and the first reactor element, and a fundamental wave resonant circuit connected in parallel with the resistance element and composed of a second capacitor element and a second reactor element, and the anti-resonance order of the first capacitor element and the first reactor element is set to a higher order than the fundamental wave order.

[0009] In such a harmonic filter equipment, the anti-resonance order of the first capacitor element and the first reactor element is set higher than the fundamental order, so the harmonic filter equipment exhibits inductivity with respect to the fundamental wave. As a result, the harmonic filter can be used in place of an additional shunt reactor to compensate for the cable capacitance or the filter's phase-leading capacitance, eliminating the need to install an additional shunt reactor. This reduces the cost of the harmonic filter equipment and allows for its miniaturization. Furthermore, the harmonic filter equipment of the present invention exhibits inductivity at the fundamental wave, and the second capacitor element and second reactor element resonate at the fundamental wave, so that at the fundamental wave, current flows through the first reactor element, the second capacitor element, and the second reactor element in that order. Therefore, when the harmonic filter is turned on or when a short-circuit fault occurs on the power grid side, an oscillating current with a period determined by the first reactor element, the second capacitor element, and the second reactor element flows from this harmonic filter equipment toward the fault point. As a result, for example, when the harmonic filter equipment of the present invention is connected to a bus via a circuit breaker, it is possible to avoid the zero current miss phenomenon, in which the current passing through the circuit breaker does not reach 0 A and continues to be unable to be interrupted.

[0010] It is preferable that the first reactor element or the first capacitor element is connected to the bus via a circuit breaker, and the inductance of the first reactor element is set within a range that satisfies the following equations 1 and 2.

[0011]

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[0012]

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[0013] With this configuration, the harmonic filter equipment can reliably exhibit inductivity at the fundamental wave, and can also reliably avoid the current zero miss phenomenon.

[0014] It is preferable that the resonance order of the first reactor element, the second capacitor element, and the second reactor element is set to a lower order than the fundamental wave.

[0015] With this configuration, the harmonic filter equipment has a resonance order lower than the fundamental order and an anti-resonance order higher than the fundamental order, so that the fundamental order can reliably exhibit inductivity.

[0016] Generally, harmonics are integer multiples of the fundamental frequency. Therefore, even if the anti-resonance order is set to a higher order than the fundamental frequency, if the anti-resonance order is set to an integer value, harmonic components may be amplified. Therefore, it is preferable to set the anti-resonance order to a non-integer value. This makes it possible to suppress the amplified harmonic components.

[0017] It is preferable that the power supply further comprises an impedance element having a damping effect connected in parallel to the first reactor element.

[0018] With this configuration, since an impedance element is connected in parallel with the first reactor element, the combined impedance of the first reactor element and the first capacitor element can be reduced at the anti-resonance order, and voltage amplification at the anti-resonance order can be mitigated.

[0019] Furthermore, a method for setting up a harmonic filter equipment includes an LC series circuit formed by a first reactor element connected to the bus and a second capacitor element and second reactor element connected to the low-voltage side of the first reactor element, and a second reactor element connected in parallel with the first capacitor element and the low-voltage side of the first reactor element, characterized in that the anti-resonance order of the first capacitor element and the first reactor element is set to an order higher than the fundamental frequency.

[0020] With this configuration, it is possible to obtain the same effects as those of the above-mentioned harmonic filter equipment. [Effects of the Invention]

[0021] According to the present invention configured in this manner, it is possible to reduce the cost and size of harmonic filter equipment, and to avoid current zero miss events when a reactor is turned on or when a short circuit occurs on the power system side. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic diagram illustrating a harmonic filter system according to an embodiment of the present invention. [Figure 2] 3 is a schematic diagram showing the fz characteristics of the harmonic filter equipment in the same embodiment. FIG. [Figure 3] FIG. 10 is a diagram showing fz characteristics in an example. [Figure 4] 10 is a graph showing the waveform of a current flowing from a harmonic filter system in the event of a three-phase short circuit fault in an embodiment. [Figure 5] 10 is a graph showing the waveform of a current flowing from a harmonic filter system in the event of a three-phase short-circuit fault in a comparative example. [Figure 6] FIG. 10 is a schematic diagram showing a harmonic filter installation according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of a harmonic filter system according to the present invention will be described below with reference to the drawings. Note that in all of the drawings shown below, some details may be omitted or exaggerated for clarity. The same components are designated by the same reference numerals, and their descriptions will be omitted where appropriate.

[0024] <Device configuration> The harmonic filter equipment 100 in this embodiment suppresses harmonic components contained in the AC voltage of a bus B, which is the target of harmonic suppression. In this embodiment, the harmonic components are, for example, the fifth, seventh, eleventh, or thirteenth harmonics. In this embodiment, power is supplied to the bus B from a power grid (not shown).

[0025] 1 , the harmonic filter equipment 100 includes a first capacitor element 11 connected to a bus B, a first reactor element 12 connected in parallel with the first capacitor element 11, a resistor element 13 connected in series with the first capacitor element 11 and the first reactor element 12, and a fundamental wave resonant circuit 14 connected in parallel with the resistor element 13 and composed of a second capacitor element 141 and a second reactor element 142. In this embodiment, the resistor element 13 is provided on the low-voltage side of the first capacitor element 11 and the second reactor element 12, but it may also be provided on the high-voltage side of the first capacitor element 11 and the second reactor element 12.

[0026] The harmonic filter equipment 100 of this embodiment constitutes a so-called C-type filter by the first capacitor element 11, the resistor element 13, and the fundamental wave resonant circuit 14. The C-type filter here refers to a high-pass filter in which a second capacitor element 141 and a second reactor element 142 are provided in parallel with the resistor element 13 to prevent loss in the resistor element 13 due to the fundamental wave current. In other words, the harmonic filter equipment 100 of this embodiment is a C-type filter to which a first reactor element 12 connected in parallel to the first capacitor element 11 has been added. The low-voltage side end of the C-type filter may be grounded or ungrounded.

[0027] In this embodiment, the high voltage side of the first capacitor element 11 and the high voltage side of the first reactor element 12 are electrically connected to the bus B via a circuit breaker S.

[0028] The fundamental wave resonant circuit 14 is a circuit that resonates at a fundamental wave by the second capacitor element 141 and the second reactor element 142. Specifically, as the second capacitor element 141 and the second reactor element 142 resonate at the fundamental wave, a current at the fundamental wave flows in the order of the first reactor element 12, the second capacitor element 141, and the second reactor element 142. Therefore, when the circuit breaker S is closed or a short-circuit fault occurs on the power grid side, a current having a period equal to an oscillation frequency determined by the first reactor element 12, the second capacitor element 141, and the second reactor element 142 flows toward the fault point, and no direct current flows.

[0029] Here, the anti-resonance order n1 of the first capacitor element 11 and the first reactor element 12 is set to a higher order than the fundamental order n0, as shown in Fig. 2. Specifically, the anti-resonance order n1 is set to a non-integer positive value. Furthermore, the anti-resonance order n1 is set to a lower order than the resonance order n2 of the first capacitor element 11, the second capacitor element 141, and the second reactor element 142. In other words, the anti-resonance order n1 is set to a higher order than the fundamental order n0 and a lower order than the resonance order n2.

[0030] As a result, the harmonic filter equipment 100 exhibits inductivity, which is a characteristic whereby the composite impedance of the harmonic filter equipment 100 increases with increasing frequency, at the fundamental wave order n0. Furthermore, the harmonic filter equipment 100 exhibits capacitiveness, which is a characteristic whereby the composite impedance of the harmonic filter equipment 100 decreases with increasing frequency, at frequencies higher than the anti-resonance order n1 and lower than the resonance order n2. Furthermore, the harmonic filter equipment 100 suppresses the harmonic component corresponding to the resonance order n2 by the first capacitor element 11, the second capacitor element 141, and the second reactor element 142 resonating at the resonance order n2, causing the harmonic component corresponding to the resonance order n2 to flow through the harmonic filter equipment 100.

[0031] 2, the resonance order n' of the first reactor element 12, the second capacitor element 141, and the second reactor element 142 is set to be lower than the fundamental wave. That is, the harmonic filter equipment 100 has a resonance order n' lower than the fundamental wave order n0 and an anti-resonance order n1 higher than the fundamental wave order n0 and lower than the resonance order n2, thereby becoming a filter that reliably exhibits inductivity at the fundamental wave.

[0032] <How to set the constants for harmonic filter equipment> Next, a method for setting the capacitance C1 of the first capacitor element 11, the inductance L1 of the first reactor element 12, the impedance R of the resistor element 13, the capacitance C2 of the second capacitor element 141, and the inductance L2 of the second reactor element 142 will be described. In the following, ω is the fundamental angular frequency, V is the circuit voltage of the circuit in which the harmonic filter equipment 100 is installed, Q1 is the fundamental wave leading phase capacitance, Q2 is the fundamental wave lagging phase capacitance, ω is the fundamental wave angular frequency (2π×50 Hz), and γ is the sharpness.

[0033] Here, the capacitance C1 of the first capacitor element 11, the impedance R of the resistor element 13, the capacitance C2 of the second capacitor element 141, and the inductance L2 of the second reactor element 142 are set in the same manner as in the conventional C-type filter. That is, the inductive reactance of the circuit in which the harmonic filter equipment 100 is installed is set to X L , the capacitive reactance of the circuit in which the harmonic filter equipment 100 is provided is X C Then, the inductive reactance X L and capacitive reactance X C is expressed by the following equations 3 and 4.

[0034]

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[0035]

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[0036] The reactance X of the second capacitor element 141 C2 and the reactance X of the second reactor element 142 L2 Since the reactance X of the first capacitor element 11 is the same as that of the fundamental wave, C1 is expressed as follows:

[0037]

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[0038] From equations 3 to 5, the inductive reactance X L , capacitive reactance X C and the reactance X of the first capacitor element 11 C1 has been calculated, the capacitance C1 of the first capacitor element 11, the impedance R of the resistor element 13, the capacitance C2 of the second capacitor element 141, and the inductance L2 of the second reactor element 142 are expressed by the following equations 6 to 9.

[0039]

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[0040]

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[0041]

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[0042]

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[0043] Next, a description will be given of a method for setting the inductance L1 of the first reactor element 12. Here, the anti-resonance order n1 of the first capacitor element 11 and the first reactor element 12 is expressed by the following equation 10.

[0044]

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[0045] In order for the harmonic filter equipment 100 to exhibit inductivity at the fundamental wave, the anti-resonance order n1 must be greater than 1. Therefore, using Equation 10, the setting range for the harmonic filter equipment 100 to exhibit inductivity at the fundamental wave is expressed by Equation 11.

[0046]

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[0047] Furthermore, a setting range for avoiding a zero current miss event is calculated. When a fault occurs on the power grid side, the zero miss evaluation time, which is the time from when the circuit breaker S opens to when a zero miss is evaluated, is defined as T. The oscillating current generated by the first reactor element 12, the second capacitor element 141, and the second reactor element 142 contributes to avoiding a zero current miss event, and it is sufficient if the half cycle of this oscillating current is shorter than the zero miss evaluation time T. In other words, the inductance L1 of the first reactor element 12, the capacitance C2 of the second capacitor element 141, and the inductance L2 of the second reactor element 142 must satisfy the following equation 12.

[0048]

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[0049] Furthermore, when avoiding a zero current miss event, the inductance L1 of the first reactor element 12 must be set to a positive value in order for the first reactor element 12, the second capacitor element 141, and the second reactor element 142 to operate as reactors. Therefore, by calculating Equation 12 for the inductance L1 of the first reactor element 12, the setting range for avoiding a zero current miss event is expressed by Equation 13.

[0050]

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[0051] By setting the inductance L1 of the first reactor element 12 so as to satisfy equations 11 and 13, the harmonic filter equipment 100 exhibits inductivity at the fundamental wave, and it is possible to avoid a zero current error event when a short circuit or other accident occurs on the power system side.

[0052] <Example> The present invention will be described in more detail below 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.

[0053] <Example: Confirmation of frequency characteristics and harmonic suppression effect> First, to confirm the frequency characteristics and harmonic suppression effect of the harmonic filter equipment 100, an analysis was performed using a known circuit simulation tool (Alternative Transient Program, hereinafter referred to as ATP). The analysis conditions were: circuit voltage V = 154 kV, fundamental wave phase lead capacitance Q1 = 10 Mvar, sharpness γ = 10, fundamental wave order n0 = 50 Hz, anti-resonance order n1 = 1.5th, and resonance order n2 = 5th. Furthermore, if there is no resistance in the circuit in which the harmonic filter equipment 100 is installed, the impedance at anti-resonance order n1 becomes infinite and the impedance at resonance order n2 becomes zero. Therefore, the analysis was performed by connecting a simulated resistor of approximately 0.5% of the inductance L1 of the first reactor element 12 in series with the first reactor element 12.

[0054] Substituting the parameters of the above analysis conditions into equations 3 to 13, the capacitance C1 of the first capacitor element 11 was 1.3 μF, the inductance L1 of the first reactor element 12 was 3356 mH, the impedance R of the resistor element 13 was 4941 Ω, the capacitance C2 of the second capacitor element 141 was 32.2 μF, and the inductance L2 of the second reactor element 142 was 315 mH.

[0055] Then, the frequency characteristics of the harmonic filter equipment 100 were analyzed using the circuit simulation tool ATP. As a result, it was confirmed that the anti-resonance order n1 and the resonance order n2 were set as shown in Figure 3. It was also confirmed that the resonance order n' was lower than the fundamental wave order n0.

[0056] <Example: Confirmation of the effect of avoiding zero current error events> Next, the circuit simulation tool ATP was used to confirm the effectiveness of the harmonic filter equipment 100 in avoiding a zero current miss event. Here, the harmonic filter equipment 100 was connected to a 154 kV voltage source via bus B, and a simulation was performed in which a three-phase short circuit fault was generated in the voltage source.

[0057] Figure 4 is a graph showing the waveform of the current flowing from the harmonic filter equipment 100 in a simulation in which a three-phase short circuit fault is generated in the voltage source. As shown in Figure 4, it was confirmed that an oscillating current is generated when a three-phase short circuit fault occurs at 0.2 seconds, and the current flowing from the harmonic filter equipment 100 passes through the zero point. Therefore, it was confirmed that the harmonic filter equipment 100 reliably exhibits inductivity at the fundamental wave, and that a DC current, which is the cause of an oscillating current and a current zero miss event, is not generated when a three-phase short circuit fault occurs.

[0058] Figure 5 is a graph showing the waveform of the current flowing from the parallel reactor when only the parallel reactor is connected to the bus in a simulation in which a three-phase short-circuit fault is generated in the voltage source. As shown in Figure 5, when a three-phase short-circuit fault occurs, it was confirmed that a DC current flows from the parallel reactor toward the fault point, and the current does not pass through the zero point, resulting in a current zero miss event.

[0059] <Effects of this embodiment> In such a harmonic filter equipment, the anti-resonance order n1 of the first capacitor element 11 and the first reactor element 12 is set to be higher than the fundamental order n0, so the harmonic filter equipment 100 exhibits inductivity with respect to the fundamental wave. As a result, the harmonic filter can be used in place of an additional shunt reactor for compensating for the cable capacitance or the filter's phase-leading capacitance, eliminating the need to install an additional shunt reactor. This reduces the cost of the harmonic filter equipment 100 and makes it possible to miniaturize the harmonic filter equipment 100. Furthermore, the harmonic filter equipment 100 exhibits inductivity at the fundamental wave, and the second capacitor element 141 and the second reactor element 142 resonate at the fundamental wave, so that at the fundamental wave, current flows through the first reactor element 12, the second capacitor element 141, and the second reactor element 142 in that order. Therefore, when the harmonic filter equipment 100 is turned on or when a short-circuit fault occurs on the power grid side, an oscillating current flows from this harmonic filter equipment toward the fault point, with a period determined by the first reactor element 12, the second capacitor element 141, and the second reactor element 142. As a result, no direct current flows from the harmonic filter equipment 100, so it is possible to avoid a zero current miss phenomenon, in which the current passing through the circuit breaker S does not become 0 A and continues to be unable to be interrupted.

[0060] Furthermore, since the inductance L1 of the first reactor element 12 is set to satisfy the formulas 11 and 13, the harmonic filter equipment 100 can reliably exhibit inductivity at the fundamental wave while reliably avoiding the current zero miss phenomenon.

[0061] Furthermore, the harmonic filter equipment has a resonance order n' lower than the fundamental order n0 and an anti-resonance order n1 higher than the fundamental order n0, so that it reliably exhibits inductivity at the fundamental wave.

[0062] Furthermore, since the anti-resonance order n1 is set to a non-integer value, the expansion of harmonic components can be suppressed.

[0063] <Other embodiments> The present invention is not limited to the above-described embodiment.

[0064] As shown in Fig. 6, the harmonic filter equipment 100 may further include an impedance element 20 having a damping effect connected in parallel to the first reactor element 12. In Fig. 6, the impedance element 20 is, for example, a resistor, but the impedance element 20 may also be a combination of a reactor, a resistor, or a capacitor. This allows the impedance of the first reactor element 12 to be lowered at the anti-resonance order n1, thereby mitigating voltage amplification at the anti-resonance order n1.

[0065] In the above embodiment, the inductance L1 of the first reactor element 12 is set to satisfy the formulas 11 and 13, but is not limited thereto. The inductance L1 of the first reactor element 12 may be set so that the anti-resonance order n1 is higher than the fundamental order n0.

[0066] In the above embodiment, the resonance order n' of the first reactor element 12, the second capacitor element 141, and the second reactor element 142 is set to an order lower than the fundamental wave, but this is not limited to this. If the harmonic filter equipment 100 exhibits inductivity at the fundamental wave, the resonance order n' of the first reactor element 12, the second capacitor element 141, and the second reactor element 142 may be set to an order higher than the fundamental wave order n0.

[0067] In the above embodiment, the anti-resonance order n1 is set to a non-integer value, but this is not limited to this. As long as the anti-resonance order n1 is set to be higher than the fundamental wave order n0, the anti-resonance order n1 may be set to an integer value.

[0068] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0069] 100···Harmonic filter equipment 11 First capacitor element 12 Second reactor element 13 Resistive element 14...Fundamental resonance circuit 141... Second capacitor element 142... Second reactor element 20 Impedance element n0...Fundamental wave order n1...anti-resonance order B...Bus bar

Claims

1. A harmonic filter equipment that suppresses harmonic components contained in the AC voltage of a bus that is a target for harmonic suppression, a first capacitor element connected to the bus; a first reactor element connected in parallel with the first capacitor element; a resistor element connected in series with the first capacitor element and the first reactor element; a fundamental wave resonant circuit connected in parallel with the resistance element and configured with a second capacitor element and a second reactor element, A harmonic filter system, characterized in that the anti-resonance order of the first capacitor element and the first reactor element is set to be higher than the fundamental wave order.

2. 2. The harmonic filter equipment according to claim 1, wherein the first reactor element or the first capacitor element is connected to the bus via a circuit breaker, and the inductance of the first reactor element is set within a range that satisfies the following equations 1 and 2. [Equation 1] [Equation 2] L １ : inductance of the first reactor element L ２ : inductance of the second reactor element C １ : capacitance of the first capacitor element C ２ : capacitance of the second capacitor element ω: Fundamental wave angular frequency T: The time from when the circuit breaker is opened to when the current zero error phenomenon is determined

3. The harmonic filter facility according to claim 1 , wherein the resonance order of the first reactor element, the second capacitor element, and the second reactor element is set to be lower than that of a fundamental wave.

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

5. The harmonic filter equipment according to claim 1 , further comprising an impedance element connected in parallel with the first reactor element.

6. A method for setting up a harmonic filter facility including a first capacitor element connected to a bus, a first reactor element connected in parallel with the first capacitor element, a resistor element connected in series with the first capacitor element, and a fundamental wave resonant circuit connected in parallel with the resistor element and formed of a second capacitor element and a second reactor element, A method for setting up a harmonic filter equipment, characterized in that the anti-resonance order of the first capacitor element and the first reactor element is set to an order higher than the fundamental wave order.

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